A Generic Autonomic Signaling Protocol (GRASP)
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This is an older version of an Internet-Draft that was ultimately published as RFC 8990.
|Authors||Carsten Bormann , Brian E. Carpenter , Bing Liu|
|Last updated||2017-05-08 (Latest revision 2017-03-30)|
|RFC stream||Internet Engineering Task Force (IETF)|
ARTART Telechat review by Martin Thomson Not ready
GENART Last Call review (of -09) by Joel Halpern Ready w/nits
INTDIR Early review (of -09) by Charles Perkins On the Right Track
|Additional resources||Mailing list discussion|
|Stream||WG state||Submitted to IESG for Publication|
|Document shepherd||Sheng Jiang|
|Shepherd write-up||Show Last changed 2017-01-17|
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Needs a YES. Needs 9 more YES or NO OBJECTION positions to pass.
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Network Working Group C. Bormann Internet-Draft Universitaet Bremen TZI Intended status: Standards Track B. Carpenter, Ed. Expires: October 1, 2017 Univ. of Auckland B. Liu, Ed. Huawei Technologies Co., Ltd March 30, 2017 A Generic Autonomic Signaling Protocol (GRASP) draft-ietf-anima-grasp-11 Abstract This document establishes requirements for a signaling protocol that enables autonomic nodes and autonomic service agents to dynamically discover peers, to synchronize state with them, and to negotiate parameter settings with them. The document then defines a general protocol for discovery, synchronization and negotiation, while the technical objectives for specific scenarios are to be described in separate documents. An Appendix briefly discusses existing protocols with comparable features. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on October 1, 2017. Copyright Notice Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of Bormann, et al. Expires October 1, 2017 [Page 1] Internet-Draft GRASP March 2017 publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirement Analysis of Discovery, Synchronization and Negotiation . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. Requirements for Discovery . . . . . . . . . . . . . . . 5 2.2. Requirements for Synchronization and Negotiation Capability . . . . . . . . . . . . . . . . . . . . . . . 6 2.3. Specific Technical Requirements . . . . . . . . . . . . . 9 3. GRASP Protocol Overview . . . . . . . . . . . . . . . . . . . 10 3.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 10 3.2. High Level Deployment Model . . . . . . . . . . . . . . . 12 3.3. High Level Design Choices . . . . . . . . . . . . . . . . 13 3.4. Quick Operating Overview . . . . . . . . . . . . . . . . 16 3.5. GRASP Protocol Basic Properties and Mechanisms . . . . . 16 3.5.1. Required External Security Mechanism . . . . . . . . 16 3.5.2. Constrained Instances . . . . . . . . . . . . . . . . 17 3.5.3. Transport Layer Usage . . . . . . . . . . . . . . . . 19 3.5.4. Discovery Mechanism and Procedures . . . . . . . . . 20 3.5.5. Negotiation Procedures . . . . . . . . . . . . . . . 23 3.5.6. Synchronization and Flooding Procedures . . . . . . . 25 3.6. GRASP Constants . . . . . . . . . . . . . . . . . . . . . 27 3.7. Session Identifier (Session ID) . . . . . . . . . . . . . 28 3.8. GRASP Messages . . . . . . . . . . . . . . . . . . . . . 29 3.8.1. Message Overview . . . . . . . . . . . . . . . . . . 29 3.8.2. GRASP Message Format . . . . . . . . . . . . . . . . 29 3.8.3. Message Size . . . . . . . . . . . . . . . . . . . . 30 3.8.4. Discovery Message . . . . . . . . . . . . . . . . . . 30 3.8.5. Discovery Response Message . . . . . . . . . . . . . 31 3.8.6. Request Messages . . . . . . . . . . . . . . . . . . 32 3.8.7. Negotiation Message . . . . . . . . . . . . . . . . . 33 3.8.8. Negotiation End Message . . . . . . . . . . . . . . . 34 3.8.9. Confirm Waiting Message . . . . . . . . . . . . . 34 3.8.10. Synchronization Message . . . . . . . . . . . . . . . 34 3.8.11. Flood Synchronization Message . . . . . . . . . . . . 35 3.8.12. Invalid Message . . . . . . . . . . . . . . . . . . . 36 3.8.13. No Operation Message . . . . . . . . . . . . . . . . 36 3.9. GRASP Options . . . . . . . . . . . . . . . . . . . . . . 36 3.9.1. Format of GRASP Options . . . . . . . . . . . . . . . 36 3.9.2. Divert Option . . . . . . . . . . . . . . . . . . . . 37 3.9.3. Accept Option . . . . . . . . . . . . . . . . . . . . 37 Bormann, et al. Expires October 1, 2017 [Page 2] Internet-Draft GRASP March 2017 3.9.4. Decline Option . . . . . . . . . . . . . . . . . . . 37 3.9.5. Locator Options . . . . . . . . . . . . . . . . . . . 38 3.10. Objective Options . . . . . . . . . . . . . . . . . . . . 40 3.10.1. Format of Objective Options . . . . . . . . . . . . 40 3.10.2. Objective flags . . . . . . . . . . . . . . . . . . 41 3.10.3. General Considerations for Objective Options . . . . 41 3.10.4. Organizing of Objective Options . . . . . . . . . . 42 3.10.5. Experimental and Example Objective Options . . . . . 44 4. Implementation Status [RFC Editor: please remove] . . . . . . 44 4.1. BUPT C++ Implementation . . . . . . . . . . . . . . . . . 44 4.2. Python Implementation . . . . . . . . . . . . . . . . . . 45 5. Security Considerations . . . . . . . . . . . . . . . . . . . 45 6. CDDL Specification of GRASP . . . . . . . . . . . . . . . . . 48 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 50 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 52 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 52 9.1. Normative References . . . . . . . . . . . . . . . . . . 52 9.2. Informative References . . . . . . . . . . . . . . . . . 53 Appendix A. Open Issues [RFC Editor: This section should be empty. Please remove] . . . . . . . . . . . . . . . 56 Appendix B. Closed Issues [RFC Editor: Please remove] . . . . . 56 Appendix C. Change log [RFC Editor: Please remove] . . . . . . . 65 Appendix D. Example Message Formats . . . . . . . . . . . . . . 71 D.1. Discovery Example . . . . . . . . . . . . . . . . . . . . 72 D.2. Flood Example . . . . . . . . . . . . . . . . . . . . . . 72 D.3. Synchronization Example . . . . . . . . . . . . . . . . . 72 D.4. Simple Negotiation Example . . . . . . . . . . . . . . . 73 D.5. Complete Negotiation Example . . . . . . . . . . . . . . 73 Appendix E. Capability Analysis of Current Protocols . . . . . . 74 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 77 1. Introduction The success of the Internet has made IP-based networks bigger and more complicated. Large-scale ISP and enterprise networks have become more and more problematic for human based management. Also, operational costs are growing quickly. Consequently, there are increased requirements for autonomic behavior in the networks. General aspects of autonomic networks are discussed in [RFC7575] and [RFC7576]. One approach is to largely decentralize the logic of network management by migrating it into network elements. A reference model for autonomic networking on this basis is given in [I-D.ietf-anima-reference-model]. The reader should consult this document to understand how various autonomic components fit together. In order to fulfill autonomy, devices that embody Autonomic Service Agents (ASAs, [RFC7575]) have specific signaling requirements. In Bormann, et al. Expires October 1, 2017 [Page 3] Internet-Draft GRASP March 2017 particular they need to discover each other, to synchronize state with each other, and to negotiate parameters and resources directly with each other. There is no limitation on the types of parameters and resources concerned, which can include very basic information needed for addressing and routing, as well as anything else that might be configured in a conventional non-autonomic network. The atomic unit of discovery, synchronization or negotiation is referred to as a technical objective, i.e, a configurable parameter or set of parameters (defined more precisely in Section 3.1). Following this Introduction, Section 2 describes the requirements for discovery, synchronization and negotiation. Negotiation is an iterative process, requiring multiple message exchanges forming a closed loop between the negotiating entities. In fact, these entities are ASAs, normally but not necessarily in different network devices. State synchronization, when needed, can be regarded as a special case of negotiation, without iteration. Section 3.3 describes a behavior model for a protocol intended to support discovery, synchronization and negotiation. The design of GeneRic Autonomic Signaling Protocol (GRASP) in Section 3 of this document is based on this behavior model. The relevant capabilities of various existing protocols are reviewed in Appendix E. The proposed discovery mechanism is oriented towards synchronization and negotiation objectives. It is based on a neighbor discovery process on the local link, but also supports diversion to peers on other links. There is no assumption of any particular form of network topology. When a device starts up with no pre-configuration, it has no knowledge of the topology. The protocol itself is capable of being used in a small and/or flat network structure such as a small office or home network as well as in a large professionally managed network. Therefore, the discovery mechanism needs to be able to allow a device to bootstrap itself without making any prior assumptions about network structure. Because GRASP can be used as part of a decision process among distributed devices or between networks, it must run in a secure and strongly authenticated environment. In realistic deployments, not all devices will support GRASP. Therefore, some autonomic service agents will directly manage a group of non-autonomic nodes, and other non-autonomic nodes will be managed traditionally. Such mixed scenarios are not discussed in this specification. Bormann, et al. Expires October 1, 2017 [Page 4] Internet-Draft GRASP March 2017 2. Requirement Analysis of Discovery, Synchronization and Negotiation This section discusses the requirements for discovery, negotiation and synchronization capabilities. The primary user of the protocol is an autonomic service agent (ASA), so the requirements are mainly expressed as the features needed by an ASA. A single physical device might contain several ASAs, and a single ASA might manage several technical objectives. If a technical objective is managed by several ASAs, any necessary coordination is outside the scope of the GRASP signaling protocol. Furthermore, requirements for ASAs themselves, such as the processing of Intent [RFC7575], are out of scope for the present document. 2.1. Requirements for Discovery D1. ASAs may be designed to manage any type of configurable device or software, as required in Section 2.2. A basic requirement is therefore that the protocol can represent and discover any kind of technical objective among arbitrary subsets of participating nodes. In an autonomic network we must assume that when a device starts up it has no information about any peer devices, the network structure, or what specific role it must play. The ASA(s) inside the device are in the same situation. In some cases, when a new application session starts up within a device, the device or ASA may again lack information about relevant peers. For example, it might be necessary to set up resources on multiple other devices, coordinated and matched to each other so that there is no wasted resource. Security settings might also need updating to allow for the new device or user. The relevant peers may be different for different technical objectives. Therefore discovery needs to be repeated as often as necessary to find peers capable of acting as counterparts for each objective that a discovery initiator needs to handle. From this background we derive the next three requirements: D2. When an ASA first starts up, it may have no knowledge of the specific network to which it is attached. Therefore the discovery process must be able to support any network scenario, assuming only that the device concerned is bootstrapped from factory condition. D3. When an ASA starts up, it must require no configured location information about any peers in order to discover them. D4. If an ASA supports multiple technical objectives, relevant peers may be different for different discovery objectives, so discovery needs to be performed separately to find counterparts for each objective. Thus, there must be a mechanism by which an ASA can Bormann, et al. Expires October 1, 2017 [Page 5] Internet-Draft GRASP March 2017 separately discover peer ASAs for each of the technical objectives that it needs to manage, whenever necessary. D5. Following discovery, an ASA will normally perform negotiation or synchronization for the corresponding objectives. The design should allow for this by conveniently linking discovery to negotiation and synchronization. It may provide an optional mechanism to combine discovery and negotiation/synchronization in a single protocol exchange. D6. Some objectives may only be significant on the local link, but others may be significant across the routed network and require off- link operations. Thus, the relevant peers might be immediate neighbors on the same layer 2 link, or they might be more distant and only accessible via layer 3. The mechanism must therefore provide both on-link and off-link discovery of ASAs supporting specific technical objectives. D7. The discovery process should be flexible enough to allow for special cases, such as the following: o During initialization, a device must be able to establish mutual trust with the rest of the network and participate in an authentication mechanism. Although this will inevitably start with a discovery action, it is a special case precisely because trust is not yet established. This topic is the subject of [I-D.ietf-anima-bootstrapping-keyinfra]. We require that once trust has been established for a device, all ASAs within the device inherit the device's credentials and are also trusted. This does not preclude the device having multiple credentials. o Depending on the type of network involved, discovery of other central functions might be needed, such as the Network Operations Center (NOC) [I-D.ietf-anima-stable-connectivity]. The protocol must be capable of supporting such discovery during initialization, as well as discovery during ongoing operation. D8. The discovery process must not generate excessive traffic and must take account of sleeping nodes. D9. There must be a mechanism for handling stale discovery results. 2.2. Requirements for Synchronization and Negotiation Capability As background, consider the example of routing protocols, the closest approximation to autonomic networking already in widespread use. Routing protocols use a largely autonomic model based on distributed devices that communicate repeatedly with each other. The focus is Bormann, et al. Expires October 1, 2017 [Page 6] Internet-Draft GRASP March 2017 reachability, so routing protocols primarily consider simple link status and metrics, and an underlying assumption is that nodes need a consistent, although partial, view of the network topology in order for the routing algorithm to converge. Also, routing is mainly based on simple information synchronization between peers, rather than on bi-directional negotiation. By contrast, autonomic networks need to be able to manage many different types of parameter and consider many more dimensions, such as latency, load, unused or limited resources, conflicting resource requests, security settings, power saving, load balancing, etc. Status information and resource metrics need to be shared between nodes for dynamic adjustment of resources and for monitoring purposes. While this might be achieved by existing protocols when they are available, the new protocol needs to be able to support parameter exchange, including mutual synchronization, even when no negotiation as such is required. In general, these parameters do not apply to all participating nodes, but only to a subset. SN1. A basic requirement for the protocol is therefore the ability to represent, discover, synchronize and negotiate almost any kind of network parameter among selected subsets of participating nodes. SN2. Negotiation is an iterative request/response process that must be guaranteed to terminate (with success or failure). While tie- breaking rules must be defined specifically for each use case, the protocol should have some general mechanisms in support of loop and deadlock prevention, such as hop count limits or timeouts. SN3. Synchronization must be possible for groups of nodes ranging from small to very large. SN4. To avoid "reinventing the wheel", the protocol should be able to encapsulate the data formats used by existing configuration protocols (such as NETCONF/YANG) in cases where that is convenient. SN5. Human intervention in complex situations is costly and error- prone. Therefore, synchronization or negotiation of parameters without human intervention is desirable whenever the coordination of multiple devices can improve overall network performance. It follows that the protocol's resource requirements must be appropriate for any device that would otherwise need human intervention. The issue of running in constrained nodes is discussed in [I-D.ietf-anima-reference-model]. SN6. Human intervention in large networks is often replaced by use of a top-down network management system (NMS). It therefore follows that the protocol, as part of the Autonomic Networking Bormann, et al. Expires October 1, 2017 [Page 7] Internet-Draft GRASP March 2017 Infrastructure, should be capable of running in any device that would otherwise be managed by an NMS, and that it can co-exist with an NMS, and with protocols such as SNMP and NETCONF. SN7. Some features are expected to be implemented by individual ASAs, but the protocol must be general enough to allow them: o Dependencies and conflicts: In order to decide upon a configuration for a given device, the device may need information from neighbors. This can be established through the negotiation procedure, or through synchronization if that is sufficient. However, a given item in a neighbor may depend on other information from its own neighbors, which may need another negotiation or synchronization procedure to obtain or decide. Therefore, there are potential dependencies and conflicts among negotiation or synchronization procedures. Resolving dependencies and conflicts is a matter for the individual ASAs involved. To allow this, there need to be clear boundaries and convergence mechanisms for negotiations. Also some mechanisms are needed to avoid loop dependencies or uncontrolled growth in a tree of dependencies. It is the ASA designer's responsibility to avoid or detect looping dependencies or excessive growth of dependency trees. The protocol's role is limited to bilateral signaling between ASAs, and the avoidance of loops during bilateral signaling. o Recovery from faults and identification of faulty devices should be as automatic as possible. The protocol's role is limited to discovery, synchronization and negotiation. These processes can occur at any time, and an ASA may need to repeat any of these steps when the ASA detects an event such as a negotiation counterpart failing. o Since a major goal is to minimize human intervention, it is necessary that the network can in effect "think ahead" before changing its parameters. One aspect of this is an ASA that relies on a knowledge base to predict network behavior. This is out of scope for the signaling protocol. However, another aspect is forecasting the effect of a change by a "dry run" negotiation before actually installing the change. Signaling a dry run is therefore a desirable feature of the protocol. Note that management logging, monitoring, alerts and tools for intervention are required. However, these can only be features of individual ASAs, not of the protocol itself. Another document [I-D.ietf-anima-stable-connectivity] discusses how such agents may be linked into conventional OAM systems via an Autonomic Control Plane [I-D.ietf-anima-autonomic-control-plane]. Bormann, et al. Expires October 1, 2017 [Page 8] Internet-Draft GRASP March 2017 SN8. The protocol will be able to deal with a wide variety of technical objectives, covering any type of network parameter. Therefore the protocol will need a flexible and easily extensible format for describing objectives. At a later stage it may be desirable to adopt an explicit information model. One consideration is whether to adopt an existing information model or to design a new one. 2.3. Specific Technical Requirements T1. It should be convenient for ASA designers to define new technical objectives and for programmers to express them, without excessive impact on run-time efficiency and footprint. In particular, it should be convenient for ASAs to be implemented independently of each other as user space programs rather than as kernel code, where such a programming model is possible. The classes of device in which the protocol might run is discussed in [I-D.ietf-anima-reference-model]. T2. The protocol should be easily extensible in case the initially defined discovery, synchronization and negotiation mechanisms prove to be insufficient. T3. To be a generic platform, the protocol payload format should be independent of the transport protocol or IP version. In particular, it should be able to run over IPv6 or IPv4. However, some functions, such as multicasting on a link, might need to be IP version dependent. By default, IPv6 should be preferred. T4. The protocol must be able to access off-link counterparts via routable addresses, i.e., must not be restricted to link-local operation. T5. It must also be possible for an external discovery mechanism to be used, if appropriate for a given technical objective. In other words, GRASP discovery must not be a prerequisite for GRASP negotiation or synchronization. T6. The protocol must be capable of supporting multiple simultaneous operations with one or more peers, especially when wait states occur. T7. Intent: Although the distribution of Intent is out of scope for this document, the protocol must not by design exclude its use for Intent distribution. T8. Management monitoring, alerts and intervention: Devices should be able to report to a monitoring system. Some events must be able to generate operator alerts and some provision for emergency Bormann, et al. Expires October 1, 2017 [Page 9] Internet-Draft GRASP March 2017 intervention must be possible (e.g. to freeze synchronization or negotiation in a mis-behaving device). These features might not use the signaling protocol itself, but its design should not exclude such use. T9. Because this protocol may directly cause changes to device configurations and have significant impacts on a running network, all protocol exchanges need to be fully secured against forged messages and man-in-the middle attacks, and secured as much as reasonably possible against denial of service attacks. There must also be an encryption mechanism to resist unwanted monitoring. However, it is not required that the protocol itself provides these security features; it may depend on an existing secure environment. 3. GRASP Protocol Overview 3.1. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119] when they appear in ALL CAPS. When these words are not in ALL CAPS (such as "should" or "Should"), they have their usual English meanings, and are not to be interpreted as [RFC2119] key words. This document uses terminology defined in [RFC7575]. The following additional terms are used throughout this document: o Discovery: a process by which an ASA discovers peers according to a specific discovery objective. The discovery results may be different according to the different discovery objectives. The discovered peers may later be used as negotiation counterparts or as sources of synchronization data. o Negotiation: a process by which two ASAs interact iteratively to agree on parameter settings that best satisfy the objectives of both ASAs. o State Synchronization: a process by which ASAs interact to receive the current state of parameter values stored in other ASAs. This is a special case of negotiation in which information is sent but the ASAs do not request their peers to change parameter settings. All other definitions apply to both negotiation and synchronization. Bormann, et al. Expires October 1, 2017 [Page 10] Internet-Draft GRASP March 2017 o Technical Objective (usually abbreviated as Objective): A technical objective is a data structure, whose main contents are a name and a value. The value consists of a single configurable parameter or a set of parameters of some kind. The exact format of an objective is defined in Section 3.10.1. An objective occurs in three contexts: Discovery, Negotiation and Synchronization. Normally, a given objective will not occur in negotiation and synchronization contexts simultaneously. * One ASA may support multiple independent objectives. * The parameter(s) in the value of a given objective apply to a specific service or function or action. They may in principle be anything that can be set to a specific logical, numerical or string value, or a more complex data structure, by a network node. Each node is expected to contain one or more ASAs which may each manage subsidiary non-autonomic nodes. * Discovery Objective: an objective in the process of discovery. Its value may be undefined. * Synchronization Objective: an objective whose specific technical content needs to be synchronized among two or more ASAs. Thus, each ASA will maintain its own copy of the objective. * Negotiation Objective: an objective whose specific technical content needs to be decided in coordination with another ASA. Again, each ASA will maintain its own copy of the objective. A detailed discussion of objectives, including their format, is found in Section 3.10. o Discovery Initiator: an ASA that starts discovery by sending a discovery message referring to a specific discovery objective. o Discovery Responder: a peer that either contains an ASA supporting the discovery objective indicated by the discovery initiator, or caches the locator(s) of the ASA(s) supporting the objective. It sends a Discovery Response, as described later. o Synchronization Initiator: an ASA that starts synchronization by sending a request message referring to a specific synchronization objective. o Synchronization Responder: a peer ASA which responds with the value of a synchronization objective. Bormann, et al. Expires October 1, 2017 [Page 11] Internet-Draft GRASP March 2017 o Negotiation Initiator: an ASA that starts negotiation by sending a request message referring to a specific negotiation objective. o Negotiation Counterpart: a peer with which the Negotiation Initiator negotiates a specific negotiation objective. o GRASP Instance: This refers to an instantiation of a GRASP protocol engine, likely including multiple threads or processes as well as dynamic data structures such as a discovery cache, running in a given security environment on a single device. o Network Interface: Unless otherwise stated, this refers to a network interface - which might be physical or virtual - that a specific instance of GRASP is currently using. A device might have other interfaces that are not used by GRASP. 3.2. High Level Deployment Model A GRASP implementation will be part of the Autonomic Networking Infrastructure in an autonomic node, which must also provide an appropriate security environment. In accordance with [I-D.ietf-anima-reference-model], this SHOULD be the Autonomic Control Plane (ACP) [I-D.ietf-anima-autonomic-control-plane]. It is expected that GRASP will access the ACP by using a typical socket programming interface. There will also be one or more Autonomic Service Agents (ASAs). In the minimal case of a single-purpose device, these components might be fully integrated. A more common model is expected to be a multi-purpose device capable of containing several ASAs. In this case it is expected that the ACP, GRASP and the ASAs will be implemented as separate processes, which are probably multi-threaded to support asynchronous and simultaneous operations. In some scenarios, a limited negotiation model might be deployed based on a limited trust relationship such as that between two administrative domains. ASAs might then exchange limited information and negotiate some particular configurations. A suitable Application Programming Interface (API) will be needed between GRASP and the ASAs. In some implementations, ASAs would run in user space with a GRASP library providing the API, and this library would in turn communicate via system calls with core GRASP functions. Details of the API are out of scope for the present document. For further details of possible deployment models, see [I-D.ietf-anima-reference-model]. An instance of GRASP must be aware of the network interfaces it will use, and of the appropriate global-scope and link-local addresses. Bormann, et al. Expires October 1, 2017 [Page 12] Internet-Draft GRASP March 2017 In the presence of the ACP, such information will be available from the adjacency table discussed in [I-D.ietf-anima-reference-model]. In other cases, GRASP must determine such information for itself. Details depend on the device and operating system. In the rest of this document, the term 'interfaces' refers only to the set of network interfaces that a specific instance of GRASP is currently using. Because GRASP needs to work with very high reliability, especially during bootstrapping and during fault conditions, it is essential that every implementation is as robust as possible. For example, discovery failures, or any kind of socket exception at any time, must not cause irrecoverable failures in GRASP itself, and must return suitable error codes through the API so that ASAs can also recover. GRASP must not depend upon non-volatile data storage. All run time error conditions, and events such as address renumbering, network interface failures, and CPU sleep/wake cycles, must be handled in such a way that GRASP will still operate correctly and securely (Section 3.5.1) afterwards. An autonomic node will normally run a single instance of GRASP, used by multiple ASAs. Possible exceptions are mentioned below. 3.3. High Level Design Choices This section describes a behavior model and design choices for GRASP, supporting discovery, synchronization and negotiation, to act as a platform for different technical objectives. o A generic platform: The protocol design is generic and independent of the synchronization or negotiation contents. The technical contents will vary according to the various technical objectives and the different pairs of counterparts. o Normally, a single main instance of the GRASP protocol engine will exist in an autonomic node, and each ASA will run as an independent asynchronous process. However, scenarios where multiple instances of GRASP run in a single node, perhaps with different security properties, are possible (Section 3.5.2). In this case, each instance MUST listen independently for GRASP link- local multicasts, and all instances MUST be woken by each such multicast, in order for discovery and flooding to work correctly. Bormann, et al. Expires October 1, 2017 [Page 13] Internet-Draft GRASP March 2017 o Security infrastructure: As noted above, the protocol itself has no built-in security functionality, and relies on a separate secure infrastructure. o Discovery, synchronization and negotiation are designed together: The discovery method and the synchronization and negotiation methods are designed in the same way and can be combined when this is useful, allowing a rapid mode of operation described in Section 3.5.4. These processes can also be performed independently when appropriate. * Thus, for some objectives, especially those concerned with application layer services, another discovery mechanism such as the future DNS Service Discovery [RFC7558] MAY be used. The choice is left to the designers of individual ASAs. o A uniform pattern for technical objectives: The synchronization and negotiation objectives are defined according to a uniform pattern. The values that they contain could be carried either in a simple binary format or in a complex object format. The basic protocol design uses the Concise Binary Object Representation (CBOR) [RFC7049], which is readily extensible for unknown future requirements. o A flexible model for synchronization: GRASP supports synchronization between two nodes, which could be used repeatedly to perform synchronization among a small number of nodes. It also supports an unsolicited flooding mode when large groups of nodes, possibly including all autonomic nodes, need data for the same technical objective. * There may be some network parameters for which a more traditional flooding mechanism such as DNCP [RFC7787] is considered more appropriate. GRASP can coexist with DNCP. o A simple initiator/responder model for negotiation: Multi-party negotiations are very complicated to model and cannot readily be guaranteed to converge. GRASP uses a simple bilateral model and can support multi-party negotiations by indirect steps. Bormann, et al. Expires October 1, 2017 [Page 14] Internet-Draft GRASP March 2017 o Organizing of synchronization or negotiation content: The technical content transmitted by GRASP will be organized according to the relevant function or service. The objectives for different functions or services are kept separate, because they may be negotiated or synchronized with different counterparts or have different response times. Thus a normal arrangement would be a single ASA managing a small set of closely related objectives, with a version of that ASA in each relevant autonomic node. Further discussion of this aspect is out of scope for the current document. o Requests and responses in negotiation procedures: The initiator can negotiate a specific negotiation objective with relevant counterpart ASAs. It can request relevant information from a counterpart so that it can coordinate its local configuration. It can request the counterpart to make a matching configuration. It can request simulation or forecast results by sending some dry run conditions. Beyond the traditional yes/no answer, the responder can reply with a suggested alternative value for the objective concerned. This would start a bi-directional negotiation ending in a compromise between the two ASAs. o Convergence of negotiation procedures: To enable convergence, when a responder suggests a new value or condition in a negotiation step reply, it should be as close as possible to the original request or previous suggestion. The suggested value of later negotiation steps should be chosen between the suggested values from the previous two steps. GRASP provides mechanisms to guarantee convergence (or failure) in a small number of steps, namely a timeout and a maximum number of iterations. o Extensibility: GRASP does not have a version number, and could be extended by adding new message types and options. In normal use, new semantics will be added by defining new synchronization or negotiation objectives. Bormann, et al. Expires October 1, 2017 [Page 15] Internet-Draft GRASP March 2017 3.4. Quick Operating Overview An instance of GRASP is expected to run as a separate core module, providing an API (such as [I-D.liu-anima-grasp-api]) to interface to various ASAs. These ASAs may operate without special privilege, unless they need it for other reasons (such as configuring IP addresses or manipulating routing tables). The GRASP mechanisms used by the ASA are built around GRASP objectives defined as data structures containing administrative information such as the objective's unique name, and its current value. The format and size of the value is not restricted by the protocol, except that it must be possible to serialise it for transmission in CBOR, which is no restriction at all in practice. GRASP provides the following mechanisms: o A discovery mechanism (M_DISCOVERY, M_RESPONSE), by which an ASA can discover other ASAs supporting a given objective. o A negotiation request mechanism (M_REQ_NEG), by which an ASA can start negotiation of an objective with a counterpart ASA. Once a negotiation has started, the process is symmetrical, and there is a negotiation step message (M_NEGOTIATE) for each ASA to use in turn. Two other functions support negotiating steps (M_WAIT, M_END). o A synchronization mechanism (M_REQ_SYN), by which an ASA can request the current value of an objective from a counterpart ASA. With this, there is a corresponding response function (M_SYNCH) for an ASA that wishes to respond to synchronization requests. o A flood mechanism (M_FLOOD), by which an ASA can cause the current value of an objective to be flooded throughout the autonomic network so that any ASA can receive it. One application of this is to act as an announcement, avoiding the need for discovery of a widely applicable objective. Some example messages and simple message flows are provided in Appendix D. 3.5. GRASP Protocol Basic Properties and Mechanisms 3.5.1. Required External Security Mechanism The protocol SHOULD always run within a secure Autonomic Control Plane (ACP) [I-D.ietf-anima-autonomic-control-plane]. The ACP is assumed to carry all messages securely, including link-local Bormann, et al. Expires October 1, 2017 [Page 16] Internet-Draft GRASP March 2017 multicast when it is virtualized over the ACP. A GRASP instance MUST verify whether the ACP is operational. If there is no ACP, one of the following alternatives applies: 1. The protocol instance MUST use another form of strong authentication and a form of strong encryption MUST be implemented. An exception is that during initialization of nodes there will be a transition period during which it might not be practical to run with strong encryption. This period MUST be as short as possible, changing to a fully secure setup as soon as possible. See Section 126.96.36.199 for further discussion. 2. The protocol instance MUST operate as described in Section 188.8.131.52 or Section 184.108.40.206. Network interfaces could be at different security levels, for example being part of the ACP or not. All the interfaces supported by a given GRASP instance MUST be at the same security level. The ACP, or in its absence another security mechanism, sets the boundary within which nodes are trusted as GRASP peers. A GRASP implementation MUST refuse to execute GRASP synchronization and negotiation functions if there is neither an operational ACP nor another secure environment. Link-local multicast is used for discovery messages. Responses to discovery messages MUST be secured, with one exception mentioned in the next section. 3.5.2. Constrained Instances This section describes some cases where additional instances of GRASP subject to certain constraints are appropriate. 220.127.116.11. No ACP As mentioned in Section 3.3, some GRASP operations might be performed across an administrative domain boundary by mutual agreement, without the benefit of an ACP. Such operations MUST be confined to a separate instance of GRASP with its own copy of all GRASP data structures. Messages MUST be authenticated and encryption MUST be implemented. TLS [RFC5246] and DTLS [RFC6347] based on a Public Key Infrastructure (PKI) [RFC5280] are RECOMMENDED for this purpose. Further details are out of scope for this document. Bormann, et al. Expires October 1, 2017 [Page 17] Internet-Draft GRASP March 2017 18.104.22.168. Discovery Unsolicited Link-Local Some services may need to use insecure GRASP discovery, response and flood messages without being able to use pre-existing security associations. Such operations being intrinsically insecure, they need to be confined to link-local use to minimize the risk of malicious actions. Possible examples include discovery of candidate ACP neighbors [I-D.ietf-anima-autonomic-control-plane], discovery of bootstrap proxies [I-D.ietf-anima-bootstrapping-keyinfra] or perhaps initialization services in networks using GRASP without being fully autonomic (e.g., no ACP). Such usage MUST be limited to link-local operations and MUST be confined to a separate insecure instance of GRASP with its own copy of all GRASP data structures. This instance is nicknamed DULL - Discovery Unsolicited Link-Local. The detailed rules for the DULL instance of GRASP are as follows: o An initiator MUST only send Discovery or Flood Synchronization link-local multicast messages with a loop count of 1. Other GRASP message types MUST NOT be sent. o A responder MUST silently discard any message whose loop count is not 1. o A responder MUST silently discard any message referring to a GRASP Objective that is not directly part of a service that requires this insecure mode. o A responder MUST NOT relay any multicast messages. o A Discovery Response MUST indicate a link-local address. o A Discovery Response MUST NOT include a Divert option. o A node MUST silently discard any message whose source address is not link-local. To minimize traffic possibly observed by third parties, GRASP traffic SHOULD be minimized by using only Flood Synchronization to announce objectives and their associated locators, rather than by using Discovery and Response. Further details are out of scope for this document 22.214.171.124. Secure Only Neighbor Negotiation Some services might use insecure on-link operations as in DULL, but also use unicast synchronization or negotiation operations protected by TLS. A separate instance of GRASP is used, with its own copy of Bormann, et al. Expires October 1, 2017 [Page 18] Internet-Draft GRASP March 2017 all GRASP data structures. This instance is nicknamed SONN - Secure Only Neighbor Negotiation. The detailed rules for the SONN instance of GRASP are as follows: o All types of GRASP message are permitted. o An initiator MUST send any Discovery or Flood Synchronization link-local multicast messages with a loop count of 1. o A responder MUST silently discard any Discovery or Flood Synchronization message whose loop count is not 1. o A responder MUST silently discard any message referring to a GRASP Objective that is not directly part of the service concerned. o A responder MUST NOT relay any multicast messages. o A Discovery Response MUST indicate a link-local address. o A Discovery Response MUST NOT include a Divert option. o A node MUST silently discard any message whose source address is not link-local. Further details are out of scope for this document. 3.5.3. Transport Layer Usage GRASP discovery and flooding messages are designed for use over link- local multicast UDP. They MUST NOT be fragmented, and therefore MUST NOT exceed the link MTU size. All other GRASP messages are unicast and could in principle run over any transport protocol. An implementation MUST support use of TCP. It MAY support use of another transport protocol. However, GRASP itself does not provide for error detection or retransmission. Use of an unreliable transport protocol is therefore NOT RECOMMENDED. Nevertheless, when running within a secure ACP on reliable infrastructure, UDP MAY be used for unicast messages not exceeding the minimum IPv6 path MTU; however, TCP MUST be used for longer messages. In other words, IPv6 fragmentation is avoided. If a node receives a UDP message but the reply is too long, it MUST open a TCP connection to the peer for the reply. Note that when the network is under heavy load or in a fault condition, UDP might become unreliable. Since this is when autonomic functions are most Bormann, et al. Expires October 1, 2017 [Page 19] Internet-Draft GRASP March 2017 necessary, automatic fallback to TCP MUST be implemented. The simplest implementation is therefore to use only TCP. For considerations when running without an ACP, see Section 126.96.36.199. For link-local multicast, the GRASP protocol listens to the well- known GRASP Listen Port (Section 3.6). For unicast transport sessions used for discovery responses, synchronization and negotiation, the ASA concerned normally listens on its own dynamically assigned ports, which are communicated to its peers during discovery. However, a minimal implementation MAY use the GRASP Listen Port for this purpose. 3.5.4. Discovery Mechanism and Procedures 188.8.131.52. Separated discovery and negotiation mechanisms Although discovery and negotiation or synchronization are defined together in GRASP, they are separate mechanisms. The discovery process could run independently from the negotiation or synchronization process. Upon receiving a Discovery (Section 3.8.4) message, the recipient node should return a response message in which it either indicates itself as a discovery responder or diverts the initiator towards another more suitable ASA. However, this response may be delayed if the recipient needs to relay the discovery onwards, as described below. The discovery action (M_DISCOVERY) will normally be followed by a negotiation (M_REQ_NEG) or synchronization (M_REQ_SYN) action. The discovery results could be utilized by the negotiation protocol to decide which ASA the initiator will negotiate with. The initiator of a discovery action for a given objective need not be capable of responding to that objective as a Negotiation Counterpart, as a Synchronization Responder or as source for flooding. For example, an ASA might perform discovery even if it only wishes to act a Synchronization Initiator or Negotiation Initiator. Such an ASA does not itself need to respond to discovery messages. It is also entirely possible to use GRASP discovery without any subsequent negotiation or synchronization action. In this case, the discovered objective is simply used as a name during the discovery process and any subsequent operations between the peers are outside the scope of GRASP. Bormann, et al. Expires October 1, 2017 [Page 20] Internet-Draft GRASP March 2017 184.108.40.206. Discovery Overview A complete discovery process will start with a multicast (of M_DISCOVERY) on the local link. On-link neighbors supporting the discovery objective will respond directly (with M_RESPONSE). A neighbor with multiple interfaces will respond with a cached discovery response if any. However, it SHOULD NOT respond with a cached response on an interface if it learnt that information from the same interface, because the peer in question will answer directly if still operational. If it has no cached response, it will relay the discovery on its other interfaces, for example reaching a higher- level gateway in a hierarchical network. If a node receiving the relayed discovery supports the discovery objective, it will respond to the relayed discovery. If it has a cached response, it will respond with that. If not, it will repeat the discovery process, which thereby becomes iterative. The loop count and timeout will ensure that the process ends. A Discovery message MAY be sent unicast (via UDP or TCP) to a peer node, which SHOULD then proceed exactly as if the message had been multicast, except that when TCP is used, the response will be on the same socket as the query. However, this mode does not guarantee successful discovery in the general case. 220.127.116.11. Discovery Procedures Discovery starts as an on-link operation. The Divert option can tell the discovery initiator to contact an off-link ASA for that discovery objective. A Discovery message is sent by a discovery initiator via UDP to the ALL_GRASP_NEIGHBORS link-local multicast address (Section 3.6). Every network device that supports GRASP always listens to a well-known UDP port to capture the discovery messages. Because this port is unique in a device, this is a function of the GRASP instance and not of an individual ASA. As a result, each ASA will need to register the objectives that it supports with the local GRASP instance. If an ASA in a neighbor device supports the requested discovery objective, the device SHOULD respond to the link-local multicast with a unicast Discovery Response message (Section 3.8.5) with locator option(s), unless it is temporarily unavailable. Otherwise, if the neighbor has cached information about an ASA that supports the requested discovery objective (usually because it discovered the same objective before), it SHOULD respond with a Discovery Response message with a Divert option pointing to the appropriate Discovery Responder. Bormann, et al. Expires October 1, 2017 [Page 21] Internet-Draft GRASP March 2017 If a device has no information about the requested discovery objective, and is not acting as a discovery relay (see below) it MUST silently discard the Discovery message. If no discovery response is received within a reasonable timeout (default GRASP_DEF_TIMEOUT milliseconds, Section 3.6), the Discovery message MAY be repeated, with a newly generated Session ID (Section 3.7). An exponential backoff SHOULD be used for subsequent repetitions, to limit the load during busy periods. Frequent repetition might be symptomatic of a denial of service attack. After a GRASP device successfully discovers a locator for a Discovery Responder supporting a specific objective, it MUST cache this information, including the interface index via which it was discovered. This cache record MAY be used for future negotiation or synchronization, and the locator SHOULD be passed on when appropriate as a Divert option to another Discovery Initiator. The cache mechanism MUST include a lifetime for each entry. The lifetime is derived from a time-to-live (ttl) parameter in each Discovery Response message. Cached entries MUST be ignored or deleted after their lifetime expires. In some environments, unplanned address renumbering might occur. In such cases, the lifetime SHOULD be short compared to the typical address lifetime and a mechanism to flush the discovery cache MUST be implemented. The discovery mechanism needs to track the node's current address to ensure that Discovery Responses always indicate the correct address. If multiple Discovery Responders are found for the same objective, they SHOULD all be cached, unless this creates a resource shortage. The method of choosing between multiple responders is an implementation choice. This choice MUST be available to each ASA but the GRASP implementation SHOULD provide a default choice. Because Discovery Responders will be cached in a finite cache, they might be deleted at any time. In this case, discovery will need to be repeated. If an ASA exits for any reason, its locator might still be cached for some time, and attempts to connect to it will fail. ASAs need to be robust in these circumstances. 18.104.22.168. Discovery Relaying A GRASP instance with multiple link-layer interfaces (typically running in a router) MUST support discovery on all interfaces. We refer to this as a 'relaying instance'. Constrained Instances (Section 3.5.2) are always single-interface instances and therefore MUST NOT perform discovery relaying. Bormann, et al. Expires October 1, 2017 [Page 22] Internet-Draft GRASP March 2017 If a relaying instance receives a Discovery message on a given interface for a specific objective that it does not support and for which it has not previously cached a Discovery Responder, it MUST relay the query by re-issuing a new Discovery message as a link-local multicast on its other interfaces. The relayed discovery message MUST have the same Session ID as the incoming discovery message and MUST be tagged with the IP address of its original initiator (see Section 3.8.4). Note that this initiator address is only used to allow for disambiguation of the Session ID and is never used to address Response packets, which are sent to the relaying instance, not the original initiator. Since the relay device is unaware of the timeout set by the original initiator it SHOULD set a timeout at least equal to GRASP_DEF_TIMEOUT milliseconds. The relaying instance MUST decrement the loop count within the objective, and MUST NOT relay the Discovery message if the result is zero. Also, it MUST limit the total rate at which it relays discovery messages to a reasonable value, in order to mitigate possible denial of service attacks. It MUST cache the Session ID value and initiator address of each relayed Discovery message until any Discovery Responses have arrived or the discovery process has timed out. To prevent loops, it MUST NOT relay a Discovery message which carries a given cached Session ID and initiator address more than once. These precautions avoid discovery loops and mitigate potential overload. The discovery results received by the relaying instance MUST in turn be sent as a Discovery Response message to the Discovery message that caused the relay action. 22.214.171.124. Rapid Mode (Discovery/Negotiation binding) A Discovery message MAY include a Negotiation Objective option. This allows a rapid mode of negotiation described in Section 3.5.5. A similar mechanism is defined for synchronization in Section 3.5.6. Note that rapid mode is currently limited to a single objective for simplicity of design and implementation. A possible future extension is to allow multiple objectives in rapid mode for greater efficiency. 3.5.5. Negotiation Procedures A negotiation initiator sends a negotiation request (using M_REQ_NEG) to a counterpart ASA, including a specific negotiation objective. It may request the negotiation counterpart to make a specific Bormann, et al. Expires October 1, 2017 [Page 23] Internet-Draft GRASP March 2017 configuration. Alternatively, it may request a certain simulation or forecast result by sending a dry run configuration. The details, including the distinction between dry run and an actual configuration change, will be defined separately for each type of negotiation objective. If no reply message of any kind is received within a reasonable timeout (default GRASP_DEF_TIMEOUT milliseconds, Section 3.6), the negotiation request MAY be repeated, with a newly generated Session ID (Section 3.7). An exponential backoff SHOULD be used for subsequent repetitions. If the counterpart can immediately apply the requested configuration, it will give an immediate positive (O_ACCEPT) answer (using M_END). This will end the negotiation phase immediately. Otherwise, it will negotiate (using M_NEGOTIATE). It will reply with a proposed alternative configuration that it can apply (typically, a configuration that uses fewer resources than requested by the negotiation initiator). This will start a bi-directional negotiation (using M_NEGOTIATE) to reach a compromise between the two ASAs. The negotiation procedure is ended when one of the negotiation peers sends a Negotiation Ending (M_END) message, which contains an accept (O_ACCEPT) or decline (O_DECLINE) option and does not need a response from the negotiation peer. Negotiation may also end in failure (equivalent to a decline) if a timeout is exceeded or a loop count is exceeded. A negotiation procedure concerns one objective and one counterpart. Both the initiator and the counterpart may take part in simultaneous negotiations with various other ASAs, or in simultaneous negotiations about different objectives. Thus, GRASP is expected to be used in a multi-threaded mode. Certain negotiation objectives may have restrictions on multi-threading, for example to avoid over-allocating resources. Some configuration actions, for example wavelength switching in optical networks, might take considerable time to execute. The ASA concerned needs to allow for this by design, but GRASP does allow for a peer to insert latency in a negotiation process if necessary (Section 3.8.9, M_WAIT). 126.96.36.199. Rapid Mode (Discovery/Negotiation Linkage) A Discovery message MAY include a Negotiation Objective option. In this case it is as if the initiator sent the sequence M_DISCOVERY, immediately followed by M_REQ_NEG. This has implications for the construction of the GRASP core, as it must carefully pass the Bormann, et al. Expires October 1, 2017 [Page 24] Internet-Draft GRASP March 2017 contents of the Negotiation Objective option to the ASA so that it may evaluate the objective directly. When a Negotiation Objective option is present the ASA replies with an M_NEGOTIATE message (or M_END with O_ACCEPT if it is immediately satisfied with the proposal), rather than with an M_RESPONSE. However, if the recipient node does not support rapid mode, discovery will continue normally. It is possible that a Discovery Response will arrive from a responder that does not support rapid mode, before such a Negotiation message arrives. In this case, rapid mode will not occur. This rapid mode could reduce the interactions between nodes so that a higher efficiency could be achieved. However, a network in which some nodes support rapid mode and others do not will have complex timing-dependent behaviors. Therefore, the rapid negotiation function SHOULD be disabled by default. 3.5.6. Synchronization and Flooding Procedures 188.8.131.52. Unicast Synchronization A synchronization initiator sends a synchronization request to a counterpart, including a specific synchronization objective. The counterpart responds with a Synchronization message (Section 3.8.10) containing the current value of the requested synchronization objective. No further messages are needed. If no reply message of any kind is received within a reasonable timeout (default GRASP_DEF_TIMEOUT milliseconds, Section 3.6), the synchronization request MAY be repeated, with a newly generated Session ID (Section 3.7). An exponential backoff SHOULD be used for subsequent repetitions. 184.108.40.206. Flooding In the case just described, the message exchange is unicast and concerns only one synchronization objective. For large groups of nodes requiring the same data, synchronization flooding is available. For this, a flooding initiator MAY send an unsolicited Flood Synchronization message containing one or more Synchronization Objective option(s), if and only if the specification of those objectives permits it. This is sent as a multicast message to the ALL_GRASP_NEIGHBORS multicast address (Section 3.6). Receiving flood multicasts is a function of the GRASP core, as in the case of discovery multicasts (Section 220.127.116.11). Bormann, et al. Expires October 1, 2017 [Page 25] Internet-Draft GRASP March 2017 To ensure that flooding does not result in a loop, the originator of the Flood Synchronization message MUST set the loop count in the objectives to a suitable value (the default is GRASP_DEF_LOOPCT). Also, a suitable mechanism is needed to avoid excessive multicast traffic. This mechanism MUST be defined as part of the specification of the synchronization objective(s) concerned. It might be a simple rate limit or a more complex mechanism such as the Trickle algorithm [RFC6206]. A GRASP device with multiple link-layer interfaces (typically a router) MUST support synchronization flooding on all interfaces. If it receives a multicast Flood Synchronization message on a given interface, it MUST relay it by re-issuing a Flood Synchronization message on its other interfaces. The relayed message MUST have the same Session ID as the incoming message and MUST be tagged with the IP address of its original initiator. Link-layer Flooding is supported by GRASP by setting the loop count to 1, and sending with a link-local source address. Floods with link-local source addresses and a loop count other than 1 are invalid, and such messages MUST be discarded. The relaying device MUST decrement the loop count within the first objective, and MUST NOT relay the Flood Synchronization message if the result is zero. Also, it MUST limit the total rate at which it relays Flood Synchronization messages to a reasonable value, in order to mitigate possible denial of service attacks. It MUST cache the Session ID value and initiator address of each relayed Flood Synchronization message for a time not less than twice GRASP_DEF_TIMEOUT milliseconds. To prevent loops, it MUST NOT relay a Flood Synchronization message which carries a given cached Session ID and initiator address more than once. These precautions avoid synchronization loops and mitigate potential overload. Note that this mechanism is unreliable in the case of sleeping nodes, or new nodes that join the network, or nodes that rejoin the network after a fault. An ASA that initiates a flood SHOULD repeat the flood at a suitable frequency and SHOULD also act as a synchronization responder for the objective(s) concerned. Thus nodes that require an objective subject to flooding can either wait for the next flood or request unicast synchronization for that objective. The multicast messages for synchronization flooding are subject to the security rules in Section 3.5.1. In practice this means that they MUST NOT be transmitted and MUST be ignored on receipt unless there is an operational ACP or equivalent strong security in place. However, because of the security weakness of link-local multicast (Section 5), synchronization objectives that are flooded SHOULD NOT Bormann, et al. Expires October 1, 2017 [Page 26] Internet-Draft GRASP March 2017 contain unencrypted private information and SHOULD be validated by the recipient ASA. 18.104.22.168. Rapid Mode (Discovery/Synchronization Linkage) A Discovery message MAY include a Synchronization Objective option. In this case the Discovery message also acts as a Request Synchronization message to indicate to the Discovery Responder that it could directly reply to the Discovery Initiator with a Synchronization message Section 3.8.10 with synchronization data for rapid processing, if the discovery target supports the corresponding synchronization objective. The design implications are similar to those discussed in Section 22.214.171.124. It is possible that a Discovery Response will arrive from a responder that does not support rapid mode, before such a Synchronization message arrives. In this case, rapid mode will not occur. This rapid mode could reduce the interactions between nodes so that a higher efficiency could be achieved. However, a network in which some nodes support rapid mode and others do not will have complex timing-dependent behaviors. Therefore, the rapid synchronization function SHOULD be configured off by default and MAY be configured on or off by Intent. 3.6. GRASP Constants o ALL_GRASP_NEIGHBORS A link-local scope multicast address used by a GRASP-enabled device to discover GRASP-enabled neighbor (i.e., on-link) devices. All devices that support GRASP are members of this multicast group. * IPv6 multicast address: TBD1 * IPv4 multicast address: TBD2 o GRASP_LISTEN_PORT (TBD3) A well-known UDP user port that every GRASP-enabled network device MUST always listen to for link-local multicasts. This user port MAY also be used to listen for TCP or UDP unicast messages in a simple implementation of GRASP (Section 3.5.3). o GRASP_DEF_TIMEOUT (60000 milliseconds) Bormann, et al. Expires October 1, 2017 [Page 27] Internet-Draft GRASP March 2017 The default timeout used to determine that a discovery etc. has failed to complete. o GRASP_DEF_LOOPCT (6) The default loop count used to determine that a negotiation has failed to complete, and to avoid looping messages. o GRASP_DEF_MAX_SIZE (2048) The default maximum message size in bytes. 3.7. Session Identifier (Session ID) This is an up to 32-bit opaque value used to distinguish multiple sessions between the same two devices. A new Session ID MUST be generated by the initiator for every new Discovery, Flood Synchronization or Request message. All responses and follow-up messages in the same discovery, synchronization or negotiation procedure MUST carry the same Session ID. The Session ID SHOULD have a very low collision rate locally. It MUST be generated by a pseudo-random algorithm using a locally generated seed which is unlikely to be used by any other device in the same network [RFC4086]. When allocating a new Session ID, GRASP MUST check that the value is not already in use and SHOULD check that it has not been used recently, by consulting a cache of current and recent sessions. In the unlikely event of a clash, GRASP MUST generate a new value. However, there is a finite probability that two nodes might generate the same Session ID value. For that reason, when a Session ID is communicated via GRASP, the receiving node MUST tag it with the initiator's IP address to allow disambiguation. In the highly unlikely event of two peers opening sessions with the same Session ID value, this tag will allow the two sessions to be distinguished. Multicast GRASP messages and their responses, which may be relayed between links, therefore include a field that carries the initiator's global IP address. There is a highly unlikely race condition in which two peers start simultaneous negotiation sessions with each other using the same Session ID value. Depending on various implementation choices, this might lead to the two sessions being confused. See Section 3.8.6 for details of how to avoid this. Bormann, et al. Expires October 1, 2017 [Page 28] Internet-Draft GRASP March 2017 3.8. GRASP Messages 3.8.1. Message Overview This section defines the GRASP message format and message types. Message types not listed here are reserved for future use. The messages currently defined are: Discovery and Discovery Response (M_DISCOVERY, M_RESPONSE). Request Negotiation, Negotiation, Confirm Waiting and Negotiation End (M_REQ_NEG, M_NEGOTIATE, M_WAIT, M_END). Request Synchronization, Synchronization, and Flood Synchronization (M_REQ_SYN, M_SYNCH, M_FLOOD. No Operation and Invalid (M_NOOP, M_INVALID). 3.8.2. GRASP Message Format GRASP messages share an identical header format and a variable format area for options. GRASP message headers and options are transmitted in Concise Binary Object Representation (CBOR) [RFC7049]. In this specification, they are described using CBOR data definition language (CDDL) [I-D.greevenbosch-appsawg-cbor-cddl]. Fragmentary CDDL is used to describe each item in this section. A complete and normative CDDL specification of GRASP is given in Section 6, including constants such as message types. Every GRASP message, except the No Operation message, carries a Session ID (Section 3.7). Options are then presented serially in the options field. In fragmentary CDDL, every GRASP message follows the pattern: grasp-message = (message .within message-structure) / noop-message message-structure = [MESSAGE_TYPE, session-id, ?initiator, *grasp-option] MESSAGE_TYPE = 1..255 session-id = 0..4294967295 ;up to 32 bits grasp-option = any The MESSAGE_TYPE indicates the type of the message and thus defines the expected options. Any options received that are not consistent with the MESSAGE_TYPE SHOULD be silently discarded. Bormann, et al. Expires October 1, 2017 [Page 29] Internet-Draft GRASP March 2017 The No Operation (noop) message is described in Section 3.8.13. The various MESSAGE_TYPE values are defined in Section 6. All other message elements are described below and formally defined in Section 6. If an unrecognized MESSAGE_TYPE is received in a unicast message, an Invalid message (Section 3.8.12) MAY be returned. Otherwise the message MAY be logged and MUST be discarded. If an unrecognized MESSAGE_TYPE is received in a multicast message, it MAY be logged and MUST be silently discarded. 3.8.3. Message Size GRASP nodes MUST be able to receive unicast messages of at least GRASP_DEF_MAX_SIZE bytes. GRASP nodes MUST NOT send unicast messages longer than GRASP_DEF_MAX_SIZE bytes unless a longer size is explicitly allowed for the objective concerned. For example, GRASP negotiation itself could be used to agree on a longer message size. The message parser used by GRASP should be configured to know about the GRASP_DEF_MAX_SIZE, or any larger negotiated message size, so that it may defend against overly long messages. The maximum size of multicast messages (M_DISCOVERY and M_FLOOD) depends on the link layer technology or link adaptation layer in use. 3.8.4. Discovery Message In fragmentary CDDL, a Discovery message follows the pattern: discovery-message = [M_DISCOVERY, session-id, initiator, objective] A discovery initiator sends a Discovery message to initiate a discovery process for a particular objective option. The discovery initiator sends all Discovery messages via UDP to port GRASP_LISTEN_PORT at the link-local ALL_GRASP_NEIGHBORS multicast address on each link-layer interface in use by GRASP. It then listens for unicast TCP responses on a given port, and stores the discovery results (including responding discovery objectives and corresponding unicast locators). The listening port used for TCP MUST be the same port as used for sending the Discovery UDP multicast, on a given interface. In a low- end implementation this MAY be GRASP_LISTEN_PORT. In a more complex implementation, the GRASP discovery mechanism will find, for each Bormann, et al. Expires October 1, 2017 [Page 30] Internet-Draft GRASP March 2017 interface, a dynamic port that it can bind to for both UDP and TCP before initiating any discovery. The 'initiator' field in the message is a globally unique IP address of the initiator, for the sole purpose of disambiguating the Session ID in other nodes. If for some reason the initiator does not have a globally unique IP address, it MUST use a link-local address for this purpose that is highly likely to be unique, for example using [RFC7217]. A Discovery message MUST include exactly one of the following: o a discovery objective option (Section 3.10.1). Its loop count MUST be set to a suitable value to prevent discovery loops (default value is GRASP_DEF_LOOPCT). If the discovery initiator requires only on-link responses, the loop count MUST be set to 1. o a negotiation objective option (Section 3.10.1). This is used both for the purpose of discovery and to indicate to the discovery target that it MAY directly reply to the discovery initiatior with a Negotiation message for rapid processing, if it could act as the corresponding negotiation counterpart. The sender of such a Discovery message MUST initialize a negotiation timer and loop count in the same way as a Request Negotiation message (Section 3.8.6). o a synchronization objective option (Section 3.10.1). This is used both for the purpose of discovery and to indicate to the discovery target that it MAY directly reply to the discovery initiator with a Synchronization message for rapid processing, if it could act as the corresponding synchronization counterpart. Its loop count MUST be set to a suitable value to prevent discovery loops (default value is GRASP_DEF_LOOPCT). As mentioned in Section 126.96.36.199, a Discovery message MAY be sent unicast to a peer node, which SHOULD then proceed exactly as if the message had been multicast. 3.8.5. Discovery Response Message In fragmentary CDDL, a Discovery Response message follows the pattern: response-message = [M_RESPONSE, session-id, initiator, ttl, (+locator-option // divert-option), ?objective)] ttl = 0..4294967295 ; in milliseconds Bormann, et al. Expires October 1, 2017 [Page 31] Internet-Draft GRASP March 2017 A node which receives a Discovery message SHOULD send a Discovery Response message if and only if it can respond to the discovery. It MUST contain the same Session ID and initiator as the Discovery message. It MUST contain a time-to-live (ttl) for the validity of the response, given as a positive integer value in milliseconds. Zero is treated as the default value GRASP_DEF_TIMEOUT (Section 3.6). It MAY include a copy of the discovery objective from the Discovery message. It is sent to the sender of the Discovery message via TCP at the port used to send the Discovery message (as explained in Section 3.8.4). In the case of a relayed Discovery message, the Discovery Response is thus sent to the relay, not the original initiator. If the responding node supports the discovery objective of the discovery, it MUST include at least one kind of locator option (Section 3.9.5) to indicate its own location. A sequence of multiple kinds of locator options (e.g. IP address option and FQDN option) is also valid. If the responding node itself does not support the discovery objective, but it knows the locator of the discovery objective, then it SHOULD respond to the discovery message with a divert option (Section 3.9.2) embedding a locator option or a combination of multiple kinds of locator options which indicate the locator(s) of the discovery objective. More details on the processing of Discovery Responses are given in Section 3.5.4. 3.8.6. Request Messages In fragmentary CDDL, Request Negotiation and Request Synchronization messages follow the patterns: request-negotiation-message = [M_REQ_NEG, session-id, objective] request-synchronization-message = [M_REQ_SYN, session-id, objective] A negotiation or synchronization requesting node sends the appropriate Request message to the unicast address (directly stored or resolved from an FQDN or URI) of the negotiation or Bormann, et al. Expires October 1, 2017 [Page 32] Internet-Draft GRASP March 2017 synchronization counterpart, using the appropriate protocol and port numbers (selected from the discovery results). A Request message MUST include the relevant objective option. In the case of Request Negotiation, the objective option MUST include the requested value. When an initiator sends a Request Negotiation message, it MUST initialize a negotiation timer for the new negotiation thread. The default is GRASP_DEF_TIMEOUT milliseconds. Unless this timeout is modified by a Confirm Waiting message (Section 3.8.9), the initiator will consider that the negotiation has failed when the timer expires. Similarly, when an initiator sends a Request Synchronization, it SHOULD initialize a synchronization timer. The default is GRASP_DEF_TIMEOUT milliseconds. The initiator will consider that synchronization has failed if there is no response before the timer expires. When an initiator sends a Request message, it MUST initialize the loop count of the objective option with a value defined in the specification of the option or, if no such value is specified, with GRASP_DEF_LOOPCT. If a node receives a Request message for an objective for which no ASA is currently listening, it MUST immediately close the relevant socket to indicate this to the initiator. This is to avoid unnecessary timeouts if, for example, an ASA exits prematurely but the GRASP core is listening on its behalf. To avoid the highly unlikely race condition in which two nodes simultaneously request sessions with each other using the same Session ID (Section 3.7), when a node receives a Request message, it MUST verify that the received Session ID is not already locally active. In case of a clash, it MUST discard the Request message, in which case the initiator will detect a timeout. 3.8.7. Negotiation Message In fragmentary CDDL, a Negotiation message follows the pattern: negotiate-message = [M_NEGOTIATE, session-id, objective] A negotiation counterpart sends a Negotiation message in response to a Request Negotiation message, a Negotiation message, or a Discovery message in Rapid Mode. A negotiation process MAY include multiple steps. Bormann, et al. Expires October 1, 2017 [Page 33] Internet-Draft GRASP March 2017 The Negotiation message MUST include the relevant Negotiation Objective option, with its value updated according to progress in the negotiation. The sender MUST decrement the loop count by 1. If the loop count becomes zero the message MUST NOT be sent. In this case the negotiation session has failed and will time out. 3.8.8. Negotiation End Message In fragmentary CDDL, a Negotiation End message follows the pattern: end-message = [M_END, session-id, accept-option / decline-option] A negotiation counterpart sends an Negotiation End message to close the negotiation. It MUST contain either an accept or a decline option, defined in Section 3.9.3 and Section 3.9.4. It could be sent either by the requesting node or the responding node. 3.8.9. Confirm Waiting Message In fragmentary CDDL, a Confirm Waiting message follows the pattern: wait-message = [M_WAIT, session-id, waiting-time] waiting-time = 0..4294967295 ; in milliseconds A responding node sends a Confirm Waiting message to ask the requesting node to wait for a further negotiation response. It might be that the local process needs more time or that the negotiation depends on another triggered negotiation. This message MUST NOT include any other options. When received, the waiting time value overwrites and restarts the current negotiation timer (Section 3.8.6). The responding node SHOULD send a Negotiation, Negotiation End or another Confirm Waiting message before the negotiation timer expires. If not, the initiator MUST abandon or restart the negotiation procedure, to avoid an indefinite wait. 3.8.10. Synchronization Message In fragmentary CDDL, a Synchronization message follows the pattern: synch-message = [M_SYNCH, session-id, objective] A node which receives a Request Synchronization, or a Discovery message in Rapid Mode, sends back a unicast Synchronization message with the synchronization data, in the form of a GRASP Option for the specific synchronization objective present in the Request Synchronization. Bormann, et al. Expires October 1, 2017 [Page 34] Internet-Draft GRASP March 2017 3.8.11. Flood Synchronization Message In fragmentary CDDL, a Flood Synchronization message follows the pattern: flood-message = [M_FLOOD, session-id, initiator, ttl, +[objective, (locator-option / )]] ttl = 0..4294967295 ; in milliseconds A node MAY initiate flooding by sending an unsolicited Flood Synchronization Message with synchronization data. This MAY be sent to port GRASP_LISTEN_PORT at the link-local ALL_GRASP_NEIGHBORS multicast address, in accordance with the rules in Section 3.5.6. The initiator address is provided, as described for Discovery messages (Section 3.8.4), only to disambiguate the Session ID. The message MUST contain a time-to-live (ttl) for the validity of the contents, given as a positive integer value in milliseconds. There is no default; zero indicates an indefinite lifetime. The synchronization data are in the form of GRASP Option(s) for specific synchronization objective(s). The loop count(s) MUST be set to a suitable value to prevent flood loops (default value is GRASP_DEF_LOOPCT). Each objective option MAY be followed by a locator option associated with the flooded objective. In its absence, an empty option MUST be included to indicate a null locator. A node that receives a Flood Synchronization message MUST cache the received objectives for use by local ASAs. Each cached objective MUST be tagged with the locator option sent with it, or with a null tag if an empty locator option was sent. If a subsequent Flood Synchronization message carrying the same objective arrives with the same tag, the corresponding cached copy of the objective MUST be overwritten. If a subsequent Flood Synchronization message carrying the same objective arrives with a different tag, a new cached entry MUST be created. Note: the purpose of this mechanism is to allow the recipient of flooded values to distinguish between different senders of the same objective, and if necessary communicate with them using the locator, protocol and port included in the locator option. Many objectives will not need this mechanism, so they will be flooded with a null locator. Bormann, et al. Expires October 1, 2017 [Page 35] Internet-Draft GRASP March 2017 Cached entries MUST be ignored or deleted after their lifetime expires. 3.8.12. Invalid Message In fragmentary CDDL, an Invalid message follows the pattern: invalid-message = [M_INVALID, session-id, ?any] This message MAY be sent by an implementation in response to an incoming unicast message that it considers invalid. The session-id MUST be copied from the incoming message. The content SHOULD be diagnostic information such as a partial copy of the invalid message. An M_INVALID message MAY be silently ignored by a recipient. However, it could be used in support of extensibility, since it indicates that the remote node does not support a new or obsolete message or option. An M_INVALID message MUST NOT be sent in response to an M_INVALID message. 3.8.13. No Operation Message In fragmentary CDDL, a No Operation message follows the pattern: noop-message = [M_NOOP] This message MAY be sent by an implementation that for practical reasons needs to initialize a socket. It MUST be silently ignored by a recipient. 3.9. GRASP Options This section defines the GRASP options for the negotiation and synchronization protocol signaling. Additional options may be defined in the future. 3.9.1. Format of GRASP Options GRASP options are CBOR objects that MUST start with an unsigned integer identifying the specific option type carried in this option. These option types are formally defined in Section 6. Apart from that the only format requirement is that each option MUST be a well- formed CBOR object. In general a CBOR array format is RECOMMENDED to limit overhead. GRASP options may be defined to include encapsulated GRASP options. Bormann, et al. Expires October 1, 2017 [Page 36] Internet-Draft GRASP March 2017 3.9.2. Divert Option The Divert option is used to redirect a GRASP request to another node, which may be more appropriate for the intended negotiation or synchronization. It may redirect to an entity that is known as a specific negotiation or synchronization counterpart (on-link or off- link) or a default gateway. The divert option MUST only be encapsulated in Discovery Response messages. If found elsewhere, it SHOULD be silently ignored. A discovery initiator MAY ignore a Divert option if it only requires direct discovery responses. In fragmentary CDDL, the Divert option follows the pattern: divert-option = [O_DIVERT, +locator-option] The embedded Locator Option(s) (Section 3.9.5) point to diverted destination target(s) in response to a Discovery message. 3.9.3. Accept Option The accept option is used to indicate to the negotiation counterpart that the proposed negotiation content is accepted. The accept option MUST only be encapsulated in Negotiation End messages. If found elsewhere, it SHOULD be silently ignored. In fragmentary CDDL, the Accept option follows the pattern: accept-option = [O_ACCEPT] 3.9.4. Decline Option The decline option is used to indicate to the negotiation counterpart the proposed negotiation content is declined and end the negotiation process. The decline option MUST only be encapsulated in Negotiation End messages. If found elsewhere, it SHOULD be silently ignored. In fragmentary CDDL, the Decline option follows the pattern: decline-option = [O_DECLINE, ?reason] reason = text ;optional error message Note: there might be scenarios where an ASA wants to decline the proposed value and restart the negotiation process. In this case it Bormann, et al. Expires October 1, 2017 [Page 37] Internet-Draft GRASP March 2017 is an implementation choice whether to send a Decline option or to continue with a Negotiate message, with an objective option that contains a null value, or one that contains a new value that might achieve convergence. 3.9.5. Locator Options These locator options are used to present reachability information for an ASA, a device or an interface. They are Locator IPv6 Address Option, Locator IPv4 Address Option, Locator FQDN (Fully Qualified Domain Name) Option and URI (Uniform Resource Identifier) Option. Since ASAs will normally run as independent user programs, locator options need to indicate the network layer locator plus the transport protocol and port number for reaching the target. For this reason, the Locator Options for IP addresses and FQDNs include this information explicitly. In the case of the URI Option, this information can be encoded in the URI itself. Note: It is assumed that all locators are in scope throughout the GRASP domain. GRASP is not intended to work across disjoint addressing or naming realms. 188.8.131.52. Locator IPv6 address option In fragmentary CDDL, the IPv6 address option follows the pattern: ipv6-locator-option = [O_IPv6_LOCATOR, ipv6-address, transport-proto, port-number] ipv6-address = bytes .size 16 transport-proto = IPPROTO_TCP / IPPROTO_UDP IPPROTO_TCP = 6 IPPROTO_UDP = 17 port-number = 0..65535 The content of this option is a binary IPv6 address followed by the protocol number and port number to be used. Note 1: The IPv6 address MUST normally have global scope. However, during initialization, a link-local address MAY be used for specific objectives only (Section 3.5.2). In this case the corresponding Discovery Response message MUST be sent via the interface to which the link-local address applies. Note 2: A link-local IPv6 address MUST NOT be used when this option is included in a Divert option. Bormann, et al. Expires October 1, 2017 [Page 38] Internet-Draft GRASP March 2017 184.108.40.206. Locator IPv4 address option In fragmentary CDDL, the IPv4 address option follows the pattern: ipv4-locator-option = [O_IPv4_LOCATOR, ipv4-address, transport-proto, port-number] ipv4-address = bytes .size 4 The content of this option is a binary IPv4 address followed by the protocol number and port number to be used. Note: If an operator has internal network address translation for IPv4, this option MUST NOT be used within the Divert option. 220.127.116.11. Locator FQDN option In fragmentary CDDL, the FQDN option follows the pattern: fqdn-locator-option = [O_FQDN_LOCATOR, text, transport-proto, port-number] The content of this option is the Fully Qualified Domain Name of the target followed by the protocol number and port number to be used. Note 1: Any FQDN which might not be valid throughout the network in question, such as a Multicast DNS name [RFC6762], MUST NOT be used when this option is used within the Divert option. Note 2: Normal GRASP operations are not expected to use this option. It is intended for special purposes such as discovering external services. 18.104.22.168. Locator URI option In fragmentary CDDL, the URI option follows the pattern: uri-locator = [O_URI_LOCATOR, text] The content of this option is the Uniform Resource Identifier of the target [RFC3986]. Note 1: Any URI which might not be valid throughout the network in question, such as one based on a Multicast DNS name [RFC6762], MUST NOT be used when this option is used within the Divert option. Note 2: Normal GRASP operations are not expected to use this option. It is intended for special purposes such as discovering external services. Bormann, et al. Expires October 1, 2017 [Page 39] Internet-Draft GRASP March 2017 3.10. Objective Options 3.10.1. Format of Objective Options An objective option is used to identify objectives for the purposes of discovery, negotiation or synchronization. All objectives MUST be in the following format, described in fragmentary CDDL: objective = [objective-name, objective-flags, loop-count, ?any] objective-name = text loop-count = 0..255 All objectives are identified by a unique name which is a UTF-8 string, to be compared byte by byte. The names of generic objectives MUST NOT include a colon (":") and MUST be registered with IANA (Section 7). The names of privately defined objectives MUST include at least one colon (":"). The string preceding the last colon in the name MUST be globally unique and in some way identify the entity or person defining the objective. The following three methods MAY be used to create such a globally unique string: 1. The unique string is a decimal number representing a registered 32 bit Private Enterprise Number (PEN) [I-D.liang-iana-pen] that uniquely identifies the enterprise defining the objective. 2. The unique string is a fully qualified domain name that uniquely identifies the entity or person defining the objective. 3. The unique string is an email address that uniquely identifies the entity or person defining the objective. The GRASP protocol treats the objective name as an opaque string. For example, "EX1", "411:EX1", "example.com:EX1", "example.org:EX1 and "firstname.lastname@example.org:EX1" would be five different objectives. The 'objective-flags' field is described below. The 'loop-count' field is used for terminating negotiation as described in Section 3.8.7. It is also used for terminating discovery as described in Section 3.5.4, and for terminating flooding as described in Section 22.214.171.124. It is placed in the objective rather than in the GRASP message format because, as far as the ASA is concerned, it is a property of the objective itself. Bormann, et al. Expires October 1, 2017 [Page 40] Internet-Draft GRASP March 2017 The 'any' field is to express the actual value of a negotiation or synchronization objective. Its format is defined in the specification of the objective and may be a simple value or a data structure of any kind. It is optional because it is optional in a Discovery or Discovery Response message. 3.10.2. Objective flags An objective may be relevant for discovery only, for discovery and negotiation, or for discovery and synchronization. This is expressed in the objective by logical flag bits: objective-flags = uint .bits objective-flag objective-flag = &( F_DISC: 0 ; valid for discovery F_NEG: 1 ; valid for negotiation F_SYNCH: 2 ; valid for synchronization F_NEG_DRY: 3 ; negotiation is dry-run ) These bits are independent and may be combined appropriately, e.g. (F_DISC and F_SYNCH) or (F_DISC and F_NEG) or (F_DISC and F_NEG and F_NEG_DRY). Note that for a given negotiation session, an objective must be either used for negotiation, or for dry-run negotiation. Mixing the two modes in a single negotiation is not possible. 3.10.3. General Considerations for Objective Options As mentioned above, Objective Options MUST be assigned a unique name. As long as privately defined Objective Options obey the rules above, this document does not restrict their choice of name, but the entity or person concerned SHOULD publish the names in use. Names are expressed as UTF-8 strings for convenience in designing Objective Options for localized use. For generic usage, names expressed in the ASCII subset of UTF-8 are RECOMMENDED. Designers planning to use non-ASCII names are strongly advised to consult [RFC7564] or its successor to understand the complexities involved. Since the GRASP protocol compares names byte by byte, all issues of Unicode profiling and canonicalization MUST be specified in the design of the Objective Option. All Objective Options MUST respect the CBOR patterns defined above as "objective" and MUST replace the "any" field with a valid CBOR data definition for the relevant use case and application. Bormann, et al. Expires October 1, 2017 [Page 41] Internet-Draft GRASP March 2017 An Objective Option that contains no additional fields beyond its "loop-count" can only be a discovery objective and MUST only be used in Discovery and Discovery Response messages. The Negotiation Objective Options contain negotiation objectives, which vary according to different functions/services. They MUST be carried by Discovery, Request Negotiation or Negotiation messages only. The negotiation initiator MUST set the initial "loop-count" to a value specified in the specification of the objective or, if no such value is specified, to GRASP_DEF_LOOPCT. For most scenarios, there should be initial values in the negotiation requests. Consequently, the Negotiation Objective options MUST always be completely presented in a Request Negotiation message, or in a Discovery message in rapid mode. If there is no initial value, the value field SHOULD be set to the 'null' value defined by CBOR. Synchronization Objective Options are similar, but MUST be carried by Discovery, Discovery Response, Request Synchronization, or Flood Synchronization messages only. They include value fields only in Synchronization or Flood Synchronization messages. 3.10.4. Organizing of Objective Options Generic objective options MUST be specified in documents available to the public and SHOULD be designed to use either the negotiation or the synchronization mechanism described above. As noted earlier, one negotiation objective is handled by each GRASP negotiation thread. Therefore, a negotiation objective, which is based on a specific function or action, SHOULD be organized as a single GRASP option. It is NOT RECOMMENDED to organize multiple negotiation objectives into a single option, nor to split a single function or action into multiple negotiation objectives. It is important to understand that GRASP negotiation does not support transactional integrity. If transactional integrity is needed for a specific objective, this must be ensured by the ASA. For example, an ASA might need to ensure that it only participates in one negotiation thread at the same time. Such an ASA would need to stop listening for incoming negotiation requests before generating an outgoing negotiation request. A synchronization objective SHOULD be organized as a single GRASP option. Some objectives will support more than one operational mode. An example is a negotiation objective with both a "dry run" mode (where Bormann, et al. Expires October 1, 2017 [Page 42] Internet-Draft GRASP March 2017 the negotiation is to find out whether the other end can in fact make the requested change without problems) and a "live" mode. Such modes will be defined in the specification of such an objective. These objectives SHOULD include flags indicating the applicable mode(s). An issue requiring particular attention is that GRASP itself is a stateless protocol. Any state associated with a dry run operation, such as temporarily reserving a resource for subsequent use in a live run, is entirely a matter for the designer of the ASA concerned. As indicated in Section 3.1, an objective's value may include multiple parameters. Parameters might be categorized into two classes: the obligatory ones presented as fixed fields; and the optional ones presented in some other form of data structure embedded in CBOR. The format might be inherited from an existing management or configuration protocol, with the objective option acting as a carrier for that format. The data structure might be defined in a formal language, but that is a matter for the specifications of individual objectives. There are many candidates, according to the context, such as ABNF, RBNF, XML Schema, YANG, etc. The GRASP protocol itself is agnostic on these questions. The only restriction is that the format can be mapped into CBOR. It is NOT RECOMMENDED to mix parameters that have significantly different response time characteristics in a single objective. Separate objectives are more suitable for such a scenario. All objectives MUST support GRASP discovery. However, as mentioned in Section 3.3, it is acceptable for an ASA to use an alternative method of discovery. Normally, a GRASP objective will refer to specific technical parameters as explained in Section 3.1. However, it is acceptable to define an abstract objective for the purpose of managing or coordinating ASAs. It is also acceptable to define a special-purpose objective for purposes such as trust bootstrapping or formation of the ACP. To guarantee convergence, a limited number of rounds or a timeout is needed for each negotiation objective. Therefore, the definition of each negotiation objective SHOULD clearly specify this, for example a default loop count and timeout, so that the negotiation can always be terminated properly. If not, the GRASP defaults will apply. There must be a well-defined procedure for concluding that a negotiation cannot succeed, and if so deciding what happens next (e.g., deadlock resolution, tie-breaking, or revert to best-effort Bormann, et al. Expires October 1, 2017 [Page 43] Internet-Draft GRASP March 2017 service). This MUST be specified for individual negotiation objectives. 3.10.5. Experimental and Example Objective Options The names "EX0" through "EX9" have been reserved for experimental options. Multiple names have been assigned because a single experiment may use multiple options simultaneously. These experimental options are highly likely to have different meanings when used for different experiments. Therefore, they SHOULD NOT be used without an explicit human decision and SHOULD NOT be used in unmanaged networks such as home networks. These names are also RECOMMENDED for use in documentation examples. 4. Implementation Status [RFC Editor: please remove] Two prototype implementations of GRASP have been made. 4.1. BUPT C++ Implementation o Name: BaseNegotiator.cpp, msg.cpp, Client.cpp, Server.cpp o Description: C++ implementation of GRASP core and API o Maturity: Prototype code, interoperable between Ubuntu. o Coverage: Corresponds to draft-carpenter-anima-gdn-protocol-03. Since it was implemented based on the old version draft, the most significant limitations comparing to current protocol design include: * Not support CBOR * Not support Flooding * Not support loop avoidance * only coded for IPv6, any IPv4 is accidental o Licensing: Huawei License. o Experience: https://github.com/liubingpang/IETF-Anima-Signaling- Protocol/blob/master/README.md o Contact: https://github.com/liubingpang/IETF-Anima-Signaling- Protocol Bormann, et al. Expires October 1, 2017 [Page 44] Internet-Draft GRASP March 2017 4.2. Python Implementation o Name: graspy o Description: Python 3 implementation of GRASP core and API. o Maturity: Prototype code, interoperable between Windows 7 and Linux. o Coverage: Corresponds to draft-ietf-anima-grasp-10. Limitations include: * insecure: uses a dummy ACP module and does not implement TLS * only coded for IPv6, any IPv4 is accidental * FQDN and URI locators incompletely supported * no code for rapid mode * relay code is lazy (no rate control) * all unicast transactions use TCP (no unicast UDP). Experimental code for unicast UDP proved to be complex and brittle. * optional Objective option in Response messages not implemented * workarounds for defects in Python socket module and Windows socket peculiarities o Licensing: Simplified BSD o Experience: https://www.cs.auckland.ac.nz/~brian/graspy/graspy.pdf o Contact: https://www.cs.auckland.ac.nz/~brian/graspy/ 5. Security Considerations A successful attack on negotiation-enabled nodes would be extremely harmful, as such nodes might end up with a completely undesirable configuration that would also adversely affect their peers. GRASP nodes and messages therefore require full protection. As explained in Section 3.5.1, GRASP MUST run within a secure environment such as the Autonomic Control Plane [I-D.ietf-anima-autonomic-control-plane], except for the constrained instances described in Section 3.5.2. - Authentication Bormann, et al. Expires October 1, 2017 [Page 45] Internet-Draft GRASP March 2017 A cryptographically authenticated identity for each device is needed in an autonomic network. It is not safe to assume that a large network is physically secured against interference or that all personnel are trustworthy. Each autonomic node MUST be capable of proving its identity and authenticating its messages. GRASP relies on a separate external certificate-based security mechanism to support authentication, data integrity protection, and anti-replay protection. Since GRASP must be deployed in an existing secure environment, the protocol itself specifies nothing concerning the trust anchor and certification authority. If GRASP is used temporarily without an external security mechanism, for example during system bootstrap (Section 3.5.1), the Session ID (Section 3.7) will act as a nonce to provide limited protection against third parties injecting responses. A full analysis of the secure bootstrap process is in [I-D.ietf-anima-bootstrapping-keyinfra]. - Authorization and Roles The GRASP protocol is agnostic about the roles and capabilities of individual ASAs and about which objectives a particular ASA is authorized to support. An implementation might support precautions such as allowing only one ASA in a given node to modify a given objective, but this may not be appropriate in all cases. For example, it might be operationally useful to allow an old and a new version of the same ASA to run simultaneously during an overlap period. These questions are out of scope for the present specification. - Privacy and confidentiality Generally speaking, no personal information is expected to be involved in the signaling protocol, so there should be no direct impact on personal privacy. Nevertheless, traffic flow paths, VPNs, etc. could be negotiated, which could be of interest for traffic analysis. Also, operators generally want to conceal details of their network topology and traffic density from outsiders. Therefore, since insider attacks cannot be excluded in a large network, the security mechanism for the protocol MUST provide message confidentiality. This is why Section 3.5.1 requires either an ACP or an alternative security mechanism. - Link-local multicast security Bormann, et al. Expires October 1, 2017 [Page 46] Internet-Draft GRASP March 2017 GRASP has no reasonable alternative to using link-local multicast for Discovery or Flood Synchronization messages and these messages are sent in clear and with no authentication. They are therefore available to on-link eavesdroppers, and could be forged by on-link attackers. In the case of Discovery, the Discovery Responses are unicast and will therefore be protected (Section 3.5.1), and an untrusted forger will not be able to receive responses. In the case of Flood Synchronization, an on-link eavesdropper will be able to receive the flooded objectives but there is no response message to consider. Some precautions for Flood Synchronization messages are suggested in Section 126.96.36.199. - DoS Attack Protection GRASP discovery partly relies on insecure link-local multicast. Since routers participating in GRASP sometimes relay discovery messages from one link to another, this could be a vector for denial of service attacks. Some mitigations are specified in Section 3.5.4. However, malicious code installed inside the Autonomic Control Plane could always launch DoS attacks consisting of spurious discovery messages, or of spurious discovery responses. It is important that firewalls prevent any GRASP messages from entering the domain from an unknown source. - Security during bootstrap and discovery A node cannot trust GRASP traffic from other nodes until the security environment (such as the ACP) has identified the trust anchor and can authenticate traffic by validating certificates for other nodes. Also, until it has succesfully enrolled [I-D.ietf-anima-bootstrapping-keyinfra] a node cannot assume that other nodes are able to authenticate its own traffic. Therefore, GRASP discovery during the bootstrap phase for a new device will inevitably be insecure. Secure synchronization and negotiation will be impossible until enrollment is complete. Further details are given in Section 3.5.2. - Security of discovered locators When GRASP discovery returns an IP address, it MUST be that of a node within the secure environment (Section 3.5.1). If it returns an FQDN or a URI, the ASA that receives it MUST NOT assume that the target of the locator is within the secure environment. Bormann, et al. Expires October 1, 2017 [Page 47] Internet-Draft GRASP March 2017 6. CDDL Specification of GRASP <CODE BEGINS> grasp-message = (message .within message-structure) / noop-message message-structure = [MESSAGE_TYPE, session-id, ?initiator, *grasp-option] MESSAGE_TYPE = 0..255 session-id = 0..4294967295 ;up to 32 bits grasp-option = any message /= discovery-message discovery-message = [M_DISCOVERY, session-id, initiator, objective] message /= response-message ;response to Discovery response-message = [M_RESPONSE, session-id, initiator, ttl, (+locator-option // divert-option), ?objective] message /= synch-message ;response to Synchronization request synch-message = [M_SYNCH, session-id, objective] message /= flood-message flood-message = [M_FLOOD, session-id, initiator, ttl, +[objective, (locator-option / )]] message /= request-negotiation-message request-negotiation-message = [M_REQ_NEG, session-id, objective] message /= request-synchronization-message request-synchronization-message = [M_REQ_SYN, session-id, objective] message /= negotiation-message negotiation-message = [M_NEGOTIATE, session-id, objective] message /= end-message end-message = [M_END, session-id, accept-option / decline-option ] message /= wait-message wait-message = [M_WAIT, session-id, waiting-time] message /= invalid-message invalid-message = [M_INVALID, session-id, ?any] noop-message = [M_NOOP] divert-option = [O_DIVERT, +locator-option] Bormann, et al. Expires October 1, 2017 [Page 48] Internet-Draft GRASP March 2017 accept-option = [O_ACCEPT] decline-option = [O_DECLINE, ?reason] reason = text ;optional error message waiting-time = 0..4294967295 ; in milliseconds ttl = 0..4294967295 ; in milliseconds locator-option /= [O_IPv4_LOCATOR, ipv4-address, transport-proto, port-number] ipv4-address = bytes .size 4 locator-option /= [O_IPv6_LOCATOR, ipv6-address, transport-proto, port-number] ipv6-address = bytes .size 16 locator-option /= [O_FQDN_LOCATOR, text, transport-proto, port-number] transport-proto = IPPROTO_TCP / IPPROTO_UDP IPPROTO_TCP = 6 IPPROTO_UDP = 17 port-number = 0..65535 locator-option /= [O_URI_LOCATOR, text] initiator = ipv4-address / ipv6-address objective-flags = uint .bits objective-flag objective-flag = &( F_DISC: 0 ; valid for discovery F_NEG: 1 ; valid for negotiation F_SYNCH: 2 ; valid for synchronization F_NEG_DRY: 3 ; negotiation is dry-run ) objective = [objective-name, objective-flags, loop-count, ?any] objective-name = text ;see specification for uniqueness rules loop-count = 0..255 ; Constants for message types and option types M_NOOP = 0 M_DISCOVERY = 1 M_RESPONSE = 2 M_REQ_NEG = 3 Bormann, et al. Expires October 1, 2017 [Page 49] Internet-Draft GRASP March 2017 M_REQ_SYN = 4 M_NEGOTIATE = 5 M_END = 6 M_WAIT = 7 M_SYNCH = 8 M_FLOOD = 9 M_INVALID = 99 O_DIVERT = 100 O_ACCEPT = 101 O_DECLINE = 102 O_IPv6_LOCATOR = 103 O_IPv4_LOCATOR = 104 O_FQDN_LOCATOR = 105 O_URI_LOCATOR = 106 <CODE ENDS> 7. IANA Considerations This document defines the GeneRic Autonomic Signaling Protocol (GRASP). Section 3.6 explains the following link-local multicast addresses, which IANA is requested to assign for use by GRASP: ALL_GRASP_NEIGHBORS multicast address (IPv6): (TBD1). Assigned in the IPv6 Link-Local Scope Multicast Addresses registry. ALL_GRASP_NEIGHBORS multicast address (IPv4): (TBD2). Assigned in the IPv4 Multicast Local Network Control Block. Section 3.6 explains the following User Port, which IANA is requested to assign for use by GRASP for both UDP and TCP: GRASP_LISTEN_PORT: (TBD3) Service Name: Generic Autonomic Signaling Protocol (GRASP) Transport Protocols: UDP, TCP Assignee: email@example.com Contact: firstname.lastname@example.org Description: See Section 3.6 Reference: RFC XXXX (this document) The IANA is requested to create a GRASP Parameter Registry including two registry tables. These are the GRASP Messages and Options Table and the GRASP Objective Names Table. GRASP Messages and Options Table. The values in this table are names paired with decimal integers. Future values MUST be assigned using Bormann, et al. Expires October 1, 2017 [Page 50] Internet-Draft GRASP March 2017 the Standards Action policy defined by [RFC5226]. The following initial values are assigned by this document: M_NOOP = 0 M_DISCOVERY = 1 M_RESPONSE = 2 M_REQ_NEG = 3 M_REQ_SYN = 4 M_NEGOTIATE = 5 M_END = 6 M_WAIT = 7 M_SYNCH = 8 M_FLOOD = 9 M_INVALID = 99 O_DIVERT = 100 O_ACCEPT = 101 O_DECLINE = 102 O_IPv6_LOCATOR = 103 O_IPv4_LOCATOR = 104 O_FQDN_LOCATOR = 105 O_URI_LOCATOR = 106 GRASP Objective Names Table. The values in this table are UTF-8 strings. Future values MUST be assigned using the Specification Required policy defined by [RFC5226]. To assist expert review of a new objective, the specification should include a precise description of the format of the new objective, with sufficient explanation of its semantics to allow independent implementations. See Section 3.10.3 for more details. If the new objective is similar in name or purpose to a previously registered objective, the specification should explain why a new objective is justified. The following initial values are assigned by this document: EX0 EX1 EX2 EX3 EX4 EX5 EX6 EX7 EX8 EX9 Bormann, et al. Expires October 1, 2017 [Page 51] Internet-Draft GRASP March 2017 8. Acknowledgements A major contribution to the original version of this document was made by Sheng Jiang. Significant review inputs were received from Toerless Eckert, Joel Halpern, Barry Leiba, Charles E. Perkins, and Michael Richardson. Valuable comments were received from Michael Behringer, Jeferson Campos Nobre, Laurent Ciavaglia, Zongpeng Du, Yu Fu, Zhenbin Li, Dimitri Papadimitriou, Pierre Peloso, Reshad Rahman, Markus Stenberg, Rene Struik, Dacheng Zhang, and other participants in the NMRG research group and the ANIMA working group. 9. References 9.1. Normative References [I-D.greevenbosch-appsawg-cbor-cddl] Birkholz, H., Vigano, C., and C. Bormann, "CBOR data definition language (CDDL): a notational convention to express CBOR data structures", draft-greevenbosch-appsawg- cbor-cddl-10 (work in progress), March 2017. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <http://www.rfc-editor.org/info/rfc2119>. [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005, <http://www.rfc-editor.org/info/rfc3986>. [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, DOI 10.17487/RFC4086, June 2005, <http://www.rfc-editor.org/info/rfc4086>. [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/RFC5246, August 2008, <http://www.rfc-editor.org/info/rfc5246>. [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., Housley, R., and W. Polk, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, <http://www.rfc-editor.org/info/rfc5280>. Bormann, et al. Expires October 1, 2017 [Page 52] Internet-Draft GRASP March 2017 [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, January 2012, <http://www.rfc-editor.org/info/rfc6347>. [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, October 2013, <http://www.rfc-editor.org/info/rfc7049>. [RFC7217] Gont, F., "A Method for Generating Semantically Opaque Interface Identifiers with IPv6 Stateless Address Autoconfiguration (SLAAC)", RFC 7217, DOI 10.17487/RFC7217, April 2014, <http://www.rfc-editor.org/info/rfc7217>. 9.2. Informative References [I-D.chaparadza-intarea-igcp] Behringer, M., Chaparadza, R., Petre, R., Li, X., and H. Mahkonen, "IP based Generic Control Protocol (IGCP)", draft-chaparadza-intarea-igcp-00 (work in progress), July 2011. [I-D.ietf-anima-autonomic-control-plane] Behringer, M., Eckert, T., and S. Bjarnason, "An Autonomic Control Plane", draft-ietf-anima-autonomic-control- plane-06 (work in progress), March 2017. [I-D.ietf-anima-bootstrapping-keyinfra] Pritikin, M., Richardson, M., Behringer, M., Bjarnason, S., and K. Watsen, "Bootstrapping Remote Secure Key Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping- keyinfra-05 (work in progress), March 2017. [I-D.ietf-anima-reference-model] Behringer, M., Carpenter, B., Eckert, T., Ciavaglia, L., Pierre, P., Liu, B., Nobre, J., and J. Strassner, "A Reference Model for Autonomic Networking", draft-ietf- anima-reference-model-03 (work in progress), March 2017. [I-D.ietf-anima-stable-connectivity] Eckert, T. and M. Behringer, "Using Autonomic Control Plane for Stable Connectivity of Network OAM", draft-ietf- anima-stable-connectivity-02 (work in progress), February 2017. Bormann, et al. Expires October 1, 2017 [Page 53] Internet-Draft GRASP March 2017 [I-D.liang-iana-pen] Liang, P., Melnikov, A., and D. Conrad, "Private Enterprise Number (PEN) practices and Internet Assigned Numbers Authority (IANA) registration considerations", draft-liang-iana-pen-06 (work in progress), July 2015. [I-D.liu-anima-grasp-api] Carpenter, B., Liu, B., Wang, W., and X. Gong, "Generic Autonomic Signaling Protocol Application Program Interface (GRASP API)", draft-liu-anima-grasp-api-03 (work in progress), February 2017. [I-D.stenberg-anima-adncp] Stenberg, M., "Autonomic Distributed Node Consensus Protocol", draft-stenberg-anima-adncp-00 (work in progress), March 2015. [RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S. Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional Specification", RFC 2205, DOI 10.17487/RFC2205, September 1997, <http://www.rfc-editor.org/info/rfc2205>. [RFC2334] Luciani, J., Armitage, G., Halpern, J., and N. Doraswamy, "Server Cache Synchronization Protocol (SCSP)", RFC 2334, DOI 10.17487/RFC2334, April 1998, <http://www.rfc-editor.org/info/rfc2334>. [RFC2608] Guttman, E., Perkins, C., Veizades, J., and M. Day, "Service Location Protocol, Version 2", RFC 2608, DOI 10.17487/RFC2608, June 1999, <http://www.rfc-editor.org/info/rfc2608>. [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, "Remote Authentication Dial In User Service (RADIUS)", RFC 2865, DOI 10.17487/RFC2865, June 2000, <http://www.rfc-editor.org/info/rfc2865>. [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, <http://www.rfc-editor.org/info/rfc3209>. [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 2003, <http://www.rfc-editor.org/info/rfc3315>. Bormann, et al. Expires October 1, 2017 [Page 54] Internet-Draft GRASP March 2017 [RFC3416] Presuhn, R., Ed., "Version 2 of the Protocol Operations for the Simple Network Management Protocol (SNMP)", STD 62, RFC 3416, DOI 10.17487/RFC3416, December 2002, <http://www.rfc-editor.org/info/rfc3416>. [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, DOI 10.17487/RFC4861, September 2007, <http://www.rfc-editor.org/info/rfc4861>. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, DOI 10.17487/RFC5226, May 2008, <http://www.rfc-editor.org/info/rfc5226>. [RFC5971] Schulzrinne, H. and R. Hancock, "GIST: General Internet Signalling Transport", RFC 5971, DOI 10.17487/RFC5971, October 2010, <http://www.rfc-editor.org/info/rfc5971>. [RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko, "The Trickle Algorithm", RFC 6206, DOI 10.17487/RFC6206, March 2011, <http://www.rfc-editor.org/info/rfc6206>. [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., and A. Bierman, Ed., "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, <http://www.rfc-editor.org/info/rfc6241>. [RFC6733] Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn, Ed., "Diameter Base Protocol", RFC 6733, DOI 10.17487/RFC6733, October 2012, <http://www.rfc-editor.org/info/rfc6733>. [RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762, DOI 10.17487/RFC6762, February 2013, <http://www.rfc-editor.org/info/rfc6762>. [RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013, <http://www.rfc-editor.org/info/rfc6763>. [RFC6887] Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and P. Selkirk, "Port Control Protocol (PCP)", RFC 6887, DOI 10.17487/RFC6887, April 2013, <http://www.rfc-editor.org/info/rfc6887>. Bormann, et al. Expires October 1, 2017 [Page 55] Internet-Draft GRASP March 2017 [RFC7558] Lynn, K., Cheshire, S., Blanchet, M., and D. Migault, "Requirements for Scalable DNS-Based Service Discovery (DNS-SD) / Multicast DNS (mDNS) Extensions", RFC 7558, DOI 10.17487/RFC7558, July 2015, <http://www.rfc-editor.org/info/rfc7558>. [RFC7564] Saint-Andre, P. and M. Blanchet, "PRECIS Framework: Preparation, Enforcement, and Comparison of Internationalized Strings in Application Protocols", RFC 7564, DOI 10.17487/RFC7564, May 2015, <http://www.rfc-editor.org/info/rfc7564>. [RFC7575] Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A., Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic Networking: Definitions and Design Goals", RFC 7575, DOI 10.17487/RFC7575, June 2015, <http://www.rfc-editor.org/info/rfc7575>. [RFC7576] Jiang, S., Carpenter, B., and M. Behringer, "General Gap Analysis for Autonomic Networking", RFC 7576, DOI 10.17487/RFC7576, June 2015, <http://www.rfc-editor.org/info/rfc7576>. [RFC7787] Stenberg, M. and S. Barth, "Distributed Node Consensus Protocol", RFC 7787, DOI 10.17487/RFC7787, April 2016, <http://www.rfc-editor.org/info/rfc7787>. [RFC7788] Stenberg, M., Barth, S., and P. Pfister, "Home Networking Control Protocol", RFC 7788, DOI 10.17487/RFC7788, April 2016, <http://www.rfc-editor.org/info/rfc7788>. [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, <http://www.rfc-editor.org/info/rfc8040>. Appendix A. Open Issues [RFC Editor: This section should be empty. Please remove] o 68. (Placeholder) Appendix B. Closed Issues [RFC Editor: Please remove] o 1. UDP vs TCP: For now, this specification suggests UDP and TCP as message transport mechanisms. This is not clarified yet. UDP is good for short conversations, is necessary for multicast discovery, and generally fits the discovery and divert scenarios well. However, it will cause problems with large messages. TCP is good for stable and long sessions, with a little bit of time Bormann, et al. Expires October 1, 2017 [Page 56] Internet-Draft GRASP March 2017 consumption during the session establishment stage. If messages exceed a reasonable MTU, a TCP mode will be required in any case. This question may be affected by the security discussion. RESOLVED by specifying UDP for short message and TCP for longer one. o 2. DTLS or TLS vs built-in security mechanism. For now, this specification has chosen a PKI based built-in security mechanism based on asymmetric cryptography. However, (D)TLS might be chosen as security solution to avoid duplication of effort. It also allows essentially similar security for short messages over UDP and longer ones over TCP. The implementation trade-offs are different. The current approach requires expensive asymmetric cryptographic calculations for every message. (D)TLS has startup overheads but cheaper crypto per message. DTLS is less mature than TLS. RESOLVED by specifying external security (ACP or (D)TLS). o The following open issues applied only if the original security model was retained: * 2.1. For replay protection, GRASP currently requires every participant to have an NTP-synchronized clock. Is this OK for low-end devices, and how does it work during device bootstrapping? We could take the Timestamp out of signature option, to become an independent and OPTIONAL (or RECOMMENDED) option. * 2.2. The Signature Option states that this option could be any place in a message. Wouldn't it be better to specify a position (such as the end)? That would be much simpler to implement. RESOLVED by changing security model. o 3. DoS Attack Protection needs work. RESOLVED by adding text. o 4. Should we consider preferring a text-based approach to discovery (after the initial discovery needed for bootstrapping)? This could be a complementary mechanism for multicast based discovery, especially for a very large autonomic network. Centralized registration could be automatically deployed incrementally. At the very first stage, the repository could be empty; then it could be filled in by the objectives discovered by Bormann, et al. Expires October 1, 2017 [Page 57] Internet-Draft GRASP March 2017 different devices (for example using Dynamic DNS Update). The more records are stored in the repository, the less the multicast- based discovery is needed. However, if we adopt such a mechanism, there would be challenges: stateful solution, and security. RESOLVED for now by adding optional use of DNS-SD by ASAs. Subsequently removed by editors as irrelevant to GRASP istelf. o 5. Need to expand description of the minimum requirements for the specification of an individual discovery, synchronization or negotiation objective. RESOLVED for now by extra wording. o 6. Use case and protocol walkthrough. A description of how a node starts up, performs discovery, and conducts negotiation and synchronisation for a sample use case would help readers to understand the applicability of this specification. Maybe it should be an artificial use case or maybe a simple real one, based on a conceptual API. However, the authors have not yet decided whether to have a separate document or have it in the protocol document. RESOLVED: recommend a separate document. o 7. Cross-check against other ANIMA WG documents for consistency and gaps. RESOLVED: Satisfied by WGLC. o 8. Consideration of ADNCP proposal. RESOLVED by adding optional use of DNCP for flooding-type synchronization. o 9. Clarify how a GDNP instance knows whether it is running inside the ACP. (Sheng) RESOLVED by improved text. o 10. Clarify how a non-ACP GDNP instance initiates (D)TLS. (Sheng) RESOLVED by improved text and declaring DTLS out of scope for this draft. o 11. Clarify how UDP/TCP choice is made. (Sheng) [Like DNS? - Brian] Bormann, et al. Expires October 1, 2017 [Page 58] Internet-Draft GRASP March 2017 RESOLVED by improved text. o 12. Justify that IP address within ACP or (D)TLS environment is sufficient to prove AN identity; or explain how Device Identity Option is used. (Sheng) RESOLVED for now: we assume that all ASAs in a device are trusted as soon as the device is trusted, so they share credentials. In that case the Device Identity Option is useless. This needs to be reviewed later. o 13. Emphasise that negotiation/synchronization are independent from discovery, although the rapid discovery mode includes the first step of a negotiation/synchronization. (Sheng) RESOLVED by improved text. o 14. Do we need an unsolicited flooding mechanism for discovery (for discovery results that everyone needs), to reduce scaling impact of flooding discovery messages? (Toerless) RESOLVED: Yes, added to requirements and solution. o 15. Do we need flag bits in Objective Options to distinguish distinguish Synchronization and Negotiation "Request" or rapid mode "Discovery" messages? (Bing) RESOLVED: yes, work on the API showed that these flags are essential. o 16. (Related to issue 14). Should we revive the "unsolicited Response" for flooding synchronisation data? This has to be done carefully due to the well-known issues with flooding, but it could be useful, e.g. for Intent distribution, where DNCP doesn't seem applicable. RESOLVED: Yes, see #14. o 17. Ensure that the discovery mechanism is completely proof against loops and protected against duplicate responses. RESOLVED: Added loop count mechanism. o 18. Discuss the handling of multiple valid discovery responses. RESOLVED: Stated that the choice must be available to the ASA but GRASP implementation should pick a default. Bormann, et al. Expires October 1, 2017 [Page 59] Internet-Draft GRASP March 2017 o 19. Should we use a text-oriented format such as JSON/CBOR instead of native binary TLV format? RESOLVED: Yes, changed to CBOR. o 20. Is the Divert option needed? If a discovery response provides a valid IP address or FQDN, the recipient doesn't gain any extra knowledge from the Divert. On the other hand, the presence of Divert informs the receiver that the target is off- link, which might be useful sometimes. RESOLVED: Decided to keep Divert option. o 21. Rename the protocol as GRASP (GeneRic Autonomic Signaling Protocol)? RESOLVED: Yes, name changed. o 22. Does discovery mechanism scale robustly as needed? Need hop limit on relaying? RESOLVED: Added hop limit. o 23. Need more details on TTL for caching discovery responses. RESOLVED: Done. o 24. Do we need "fast withdrawal" of discovery responses? RESOLVED: This doesn't seem necessary. If an ASA exits or stops supporting a given objective, peers will fail to start future sessions and will simply repeat discovery. o 25. Does GDNP discovery meet the needs of multi-hop DNS-SD? RESOLVED: Decided not to consider this further as a GRASP protocol issue. GRASP objectives could embed DNS-SD formats if needed. o 26. Add a URL type to the locator options (for security bootstrap etc.) RESOLVED: Done, later renamed as URI. o 27. Security of Flood multicasts (Section 188.8.131.52). RESOLVED: added text. o 28. Does ACP support secure link-local multicast? Bormann, et al. Expires October 1, 2017 [Page 60] Internet-Draft GRASP March 2017 RESOLVED by new text in the Security Considerations. o 29. PEN is used to distinguish vendor options. Would it be better to use a domain name? Anything unique will do. RESOLVED: Simplified this by removing PEN field and changing naming rules for objectives. o 30. Does response to discovery require randomized delays to mitigate amplification attacks? RESOLVED: WG feedback is that it's unnecessary. o 31. We have specified repeats for failed discovery etc. Is that sufficient to deal with sleeping nodes? RESOLVED: WG feedback is that it's unnecessary to say more. o 32. We have one-to-one synchronization and flooding synchronization. Do we also need selective flooding to a subset of nodes? RESOLVED: This will be discussed as a protocol extension in a separate draft (draft-liu-anima-grasp-distribution). o 33. Clarify if/when discovery needs to be repeated. RESOLVED: Done. o 34. Clarify what is mandatory for running in ACP, expand discussion of security boundary when running with no ACP - might rely on the local PKI infrastructure. RESOLVED: Done. o 35. State that role-based authorization of ASAs is out of scope for GRASP. GRASP doesn't recognize/handle any "roles". RESOLVED: Done. o 36. Reconsider CBOR definition for PEN syntax. ( objective-name = text / [pen, text] ; pen = uint ) RESOLVED: See issue 29. o 37. Are URI locators really needed? Bormann, et al. Expires October 1, 2017 [Page 61] Internet-Draft GRASP March 2017 RESOLVED: Yes, e.g. for security bootstrap discovery, but added note that addresses are the normal case (same for FQDN locators). o 38. Is Session ID sufficient to identify relayed responses? Isn't the originator's address needed too? RESOLVED: Yes, this is needed for multicast messages and their responses. o 39. Clarify that a node will contain one GRASP instance supporting multiple ASAs. RESOLVED: Done. o 40. Add a "reason" code to the DECLINE option? RESOLVED: Done. o 41. What happens if an ASA cannot conveniently use one of the GRASP mechanisms? Do we (a) add a message type to GRASP, or (b) simply pass the discovery results to the ASA so that it can open its own socket? RESOLVED: Both would be possible, but (b) is preferred. o 42. Do we need a feature whereby an ASA can bypass the ACP and use the data plane for efficiency/throughput? This would require discovery to return non-ACP addresses and would evade ACP security. RESOLVED: This is considered out of scope for GRASP, but a comment has been added in security considerations. o 43. Rapid mode synchronization and negotiation is currently limited to a single objective for simplicity of design and implementation. A future consideration is to allow multiple objectives in rapid mode for greater efficiency. RESOLVED: This is considered out of scope for this version. o 44. In requirement T9, the words that encryption "may not be required in all deployments" were removed. Is that OK?. RESOLVED: No objections. o 45. Device Identity Option is unused. Can we remove it completely?. Bormann, et al. Expires October 1, 2017 [Page 62] Internet-Draft GRASP March 2017 RESOLVED: No objections. Done. o 46. The 'initiator' field in DISCOVER, RESPONSE and FLOOD messages is intended to assist in loop prevention. However, we also have the loop count for that. Also, if we create a new Session ID each time a DISCOVER or FLOOD is relayed, that ID can be disambiguated by recipients. It would be simpler to remove the initiator from the messages, making parsing more uniform. Is that OK? RESOLVED: Yes. Done. o 47. REQUEST is a dual purpose message (request negotiation or request synchronization). Would it be better to split this into two different messages (and adjust various message names accordingly)? RESOLVED: Yes. Done. o 48. Should the Appendix "Capability Analysis of Current Protocols" be deleted before RFC publication? RESOLVED: No (per WG meeting at IETF 96). o 49. Section 3.5.1 Should say more about signaling between two autonomic networks/domains. RESOLVED: Description of separate GRASP instance added. o 50. Is Rapid mode limited to on-link only? What happens if first discovery responder does not support Rapid Mode? Section 3.5.5, Section 3.5.6) RESOLVED: Not limited to on-link. First responder wins. o 51. Should flooded objectives have a time-to-live before they are deleted from the flood cache? And should they be tagged in the cache with their source locator? RESOLVED: TTL added to Flood (and Discovery Response) messages. Cached flooded objectives must be tagged with their originating ASA locator, and multiple copies must be kept if necessary. o 52. Describe in detail what is allowed and disallowed in an insecure instance of GRASP. RESOLVED: Done. Bormann, et al. Expires October 1, 2017 [Page 63] Internet-Draft GRASP March 2017 o 53. Tune IANA Considerations to support early assignment request. o 54. Is there a highly unlikely race condition if two peers simultaneously choose the same Session ID and send each other simultaneous M_REQ_NEG messages? RESOLVED: Yes. Enhanced text on Session ID generation, and added precaution when receiving a Request message. o 55. Could discovery be performed over TCP? RESOLVED: Unicast discovery added as an option. o 56. Change Session-ID to 32 bits? RESOLVED: Done. o 57. Add M_INVALID message? RESOLVED: Done. o 58. Maximum message size? RESOLVED by specifying default maximum message size (2048 bytes). o 59. Add F_NEG_DRY flag to specify a "dry run" objective?. RESOLVED: Done. o 60. Change M_FLOOD syntax to associate a locator with each objective? RESOLVED: Done. o 61. Is the SONN constrained instance really needed? RESOLVED: Retained but only as an option. o 62. Is it helpful to tag descriptive text with message names (M_DISCOVER etc.)? RESOLVED: Yes, done in various parts of the text. o 63. Should encryption be MUST instead of SHOULD in Section 3.5.1 and Section 184.108.40.206? RESOLVED: Yes, MUST implement in both cases. Bormann, et al. Expires October 1, 2017 [Page 64] Internet-Draft GRASP March 2017 o 64. Should more security text be moved from the main text into the Security Considerations? RESOLVED: No, on AD advice. o 65. Do we need to formally restrict Unicode characters allowed in objective names? RESOLVED: No, but need to point to guidance from PRECIS WG. o 66. Split requirements into separate document? RESOLVED: No, on AD advice. o 67. Remove normative dependency on draft-greevenbosch-appsawg- cbor-cddl? RESOLVED: No, on AD advice. In worst case, fix at AUTH48. Appendix C. Change log [RFC Editor: Please remove] draft-ietf-anima-grasp-11, 2017-03-30: Updates following IETF 98 discussion: Encryption changed to a MUST implement. Pointed to guidance on UTF-8 names. draft-ietf-anima-grasp-10, 2017-03-10: Updates following IETF Last call: Protocol change: Specify that an objective with no initial value should have its value field set to CBOR 'null'. Protocol change: Specify behavior on receiving unrecognized message type. Noted that UTF-8 names are matched byte-for-byte. Added brief guidance for Expert Reviewer of new generic objectives. Numerous editorial improvements and clarifications and minor text rearrangements, none intended to change the meaning. draft-ietf-anima-grasp-09, 2016-12-15: Bormann, et al. Expires October 1, 2017 [Page 65] Internet-Draft GRASP March 2017 Protocol change: Add F_NEG_DRY flag to specify a "dry run" objective. Protocol change: Change M_FLOOD syntax to associate a locator with each objective. Concentrated mentions of TLS in one section, with all details out of scope. Clarified text around constrained instances of GRASP. Strengthened text restricting LL addresses in locator options. Clarified description of rapid mode processsing. Specified that cached discovery results should not be returned on the same interface where they were learned. Shortened text in "High Level Design Choices" Dropped the word 'kernel' to avoid confusion with o/s kernel mode. Editorial improvements and clarifications. draft-ietf-anima-grasp-08, 2016-10-30: Protocol change: Added M_INVALID message. Protocol change: Increased Session ID space to 32 bits. Enhanced rules to avoid Session ID clashes. Corrected and completed description of timeouts for Request messages. Improved wording about exponential backoff and DoS. Clarified that discovery relaying is not done by limited security instances. Corrected and expanded explanation of port used for Discovery Response. Noted that Discovery message could be sent unicast in special cases. Added paragraph on extensibility. Specified default maximum message size. Added Appendix for sample messages. Bormann, et al. Expires October 1, 2017 [Page 66] Internet-Draft GRASP March 2017 Added short protocol overview. Editorial fixes, including minor re-ordering for readability. draft-ietf-anima-grasp-07, 2016-09-13: Protocol change: Added TTL field to Flood message (issue 51). Protocol change: Added Locator option to Flood message (issue 51). Protocol change: Added TTL field to Discovery Response message (corrollary to issue 51). Clarified details of rapid mode (issues 43 and 50). Description of inter-domain GRASP instance added (issue 49). Description of limited security GRASP instances added (issue 52). Strengthened advice to use TCP rather than UDP. Updated IANA considerations and text about well-known port usage (issue 53). Amended text about ASA authorization and roles to allow for overlapping ASAs. Added text recommending that Flood should be repeated periodically. Editorial fixes. draft-ietf-anima-grasp-06, 2016-06-27: Added text on discovery cache timeouts. Noted that ASAs that are only initiators do not need to respond to discovery message. Added text on unexpected address changes. Added text on robust implementation. Clarifications and editorial fixes for numerous review comments Added open issues for some review comments. draft-ietf-anima-grasp-05, 2016-05-13: Bormann, et al. Expires October 1, 2017 [Page 67] Internet-Draft GRASP March 2017 Noted in requirement T1 that it should be possible to implement ASAs independently as user space programs. Protocol change: Added protocol number and port to discovery response. Updated protocol description, CDDL and IANA considerations accordingly. Clarified that discovery and flood multicasts are handled by the GRASP core, not directly by ASAs. Clarified that a node may discover an objective without supporting it for synchronization or negotiation. Added Implementation Status section. Added reference to SCSP. Editorial fixes. draft-ietf-anima-grasp-04, 2016-03-11: Protocol change: Restored initiator field in certain messages and adjusted relaying rules to provide complete loop detection. Updated IANA Considerations. draft-ietf-anima-grasp-03, 2016-02-24: Protocol change: Removed initiator field from certain messages and adjusted relaying requirement to simplify loop detection. Also clarified narrative explanation of discovery relaying. Protocol change: Split Request message into two (Request Negotiation and Request Synchronization) and updated other message names for clarity. Protocol change: Dropped unused Device ID option. Further clarified text on transport layer usage. New text about multicast insecurity in Security Considerations. Various other clarifications and editorial fixes, including moving some material to Appendix. draft-ietf-anima-grasp-02, 2016-01-13: Resolved numerous issues according to WG discussions. Bormann, et al. Expires October 1, 2017 [Page 68] Internet-Draft GRASP March 2017 Renumbered requirements, added D9. Protocol change: only allow one objective in rapid mode. Protocol change: added optional error string to DECLINE option. Protocol change: removed statement that seemed to say that a Request not preceded by a Discovery should cause a Discovery response. That made no sense, because there is no way the initiator would know where to send the Request. Protocol change: Removed PEN option from vendor objectives, changed naming rule accordingly. Protocol change: Added FLOOD message to simplify coding. Protocol change: Added SYNCH message to simplify coding. Protocol change: Added initiator id to DISCOVER, RESPONSE and FLOOD messages. But also allowed the relay process for DISCOVER and FLOOD to regenerate a Session ID. Protocol change: Require that discovered addresses must be global (except during bootstrap). Protocol change: Receiver of REQUEST message must close socket if no ASA is listening for the objective. Protocol change: Simplified Waiting message. Protocol change: Added No Operation message. Renamed URL locator type as URI locator type. Updated CDDL definition. Various other clarifications and editorial fixes. draft-ietf-anima-grasp-01, 2015-10-09: Updated requirements after list discussion. Changed from TLV to CBOR format - many detailed changes, added co- author. Tightened up loop count and timeouts for various cases. Noted that GRASP does not provide transactional integrity. Bormann, et al. Expires October 1, 2017 [Page 69] Internet-Draft GRASP March 2017 Various other clarifications and editorial fixes. draft-ietf-anima-grasp-00, 2015-08-14: File name and protocol name changed following WG adoption. Added URL locator type. draft-carpenter-anima-gdn-protocol-04, 2015-06-21: Tuned wording around hierarchical structure. Changed "device" to "ASA" in many places. Reformulated requirements to be clear that the ASA is the main customer for signaling. Added requirement for flooding unsolicited synch, and added it to protocol spec. Recognized DNCP as alternative for flooding synch data. Requirements clarified, expanded and rearranged following design team discussion. Clarified that GDNP discovery must not be a prerequisite for GDNP negotiation or synchronization (resolved issue 13). Specified flag bits for objective options (resolved issue 15). Clarified usage of ACP vs TLS/DTLS and TCP vs UDP (resolved issues 9,10,11). Updated DNCP description from latest DNCP draft. Editorial improvements. draft-carpenter-anima-gdn-protocol-03, 2015-04-20: Removed intrinsic security, required external security Format changes to allow DNCP co-existence Recognized DNS-SD as alternative discovery method. Editorial improvements draft-carpenter-anima-gdn-protocol-02, 2015-02-19: Bormann, et al. Expires October 1, 2017 [Page 70] Internet-Draft GRASP March 2017 Tuned requirements to clarify scope, Clarified relationship between types of objective, Clarified that objectives may be simple values or complex data structures, Improved description of objective options, Added loop-avoidance mechanisms (loop count and default timeout, limitations on discovery relaying and on unsolicited responses), Allow multiple discovery objectives in one response, Provided for missing or multiple discovery responses, Indicated how modes such as "dry run" should be supported, Minor editorial and technical corrections and clarifications, Reorganized future work list. draft-carpenter-anima-gdn-protocol-01, restructured the logical flow of the document, updated to describe synchronization completely, add unsolicited responses, numerous corrections and clarifications, expanded future work list, 2015-01-06. draft-carpenter-anima-gdn-protocol-00, combination of draft-jiang- config-negotiation-ps-03 and draft-jiang-config-negotiation-protocol- 02, 2014-10-08. Appendix D. Example Message Formats For readers unfamiliar with CBOR, this appendix shows a number of example GRASP messages conforming to the CDDL syntax given in Section 6. Each message is shown three times in the following formats: 1. CBOR diagnostic notation. 2. Similar, but showing the names of the constants. (Details of the flag bit encoding are omitted.) 3. Hexadecimal version of the CBOR wire format. Long lines are split for display purposes only. Bormann, et al. Expires October 1, 2017 [Page 71] Internet-Draft GRASP March 2017 D.1. Discovery Example The initiator (2001:db8:f000:baaa:28cc:dc4c:9703:6781) multicasts a discovery message looking for objective EX1: [1, 13948744, h'20010db8f000baaa28ccdc4c97036781', ["EX1", 5, 2, 0]] [M_DISCOVERY, 13948744, h'20010db8f000baaa28ccdc4c97036781', ["EX1", F_SYNCH_bits, 2, 0]] h'84011a00d4d7485020010db8f000baaa28ccdc4c970367818463455831050200' A peer (2001:0db8:f000:baaa:f000:baaa:f000:baaa) responds with a locator: [2, 13948744, h'20010db8f000baaa28ccdc4c97036781', 60000, [103, h'20010db8f000baaaf000baaaf000baaa', 6, 49443]] [M_RESPONSE, 13948744, h'20010db8f000baaa28ccdc4c97036781', 60000, [O_IPv6_LOCATOR, h'20010db8f000baaaf000baaaf000baaa', IPPROTO_TCP, 49443]] h'85021a00d4d7485020010db8f000baaa28ccdc4c9703678119ea6084186750 20010db8f000baaaf000baaaf000baaa0619c123' D.2. Flood Example The initiator multicasts a flood message. The single objective has a null locator. There is no response: [9, 3504974, h'20010db8f000baaa28ccdc4c97036781', 10000, [["EX1", 5, 2, ["Example 1 value=", 100]], ] ] [M_FLOOD, 3504974, h'20010db8f000baaa28ccdc4c97036781', 10000, [["EX1", F_SYNCH_bits, 2, ["Example 1 value=", 100]], ] ] h'86091a00357b4e5020010db8f000baaa28ccdc4c97036781192710 828463455831050282704578616d706c6520312076616c75653d186480' D.3. Synchronization Example Following successful discovery of objective EX2, the initiator unicasts a request: [4, 4038926, ["EX2", 5, 5, 0]] [M_REQ_SYN, 4038926, ["EX2", F_SYNCH_bits, 5, 0]] h'83041a003da10e8463455832050500' The peer responds with a value: [8, 4038926, ["EX2", 5, 5, ["Example 2 value=", 200]]] [M_SYNCH, 4038926, ["EX2", F_SYNCH_bits, 5, ["Example 2 value=", 200]]] h'83081a003da10e8463455832050582704578616d706c6520322076616c75653d18c8' Bormann, et al. Expires October 1, 2017 [Page 72] Internet-Draft GRASP March 2017 D.4. Simple Negotiation Example Following successful discovery of objective EX3, the initiator unicasts a request: [3, 802813, ["EX3", 3, 6, ["NZD", 47]]] [M_REQ_NEG, 802813, ["EX3", F_NEG_bits, 6, ["NZD", 47]]] h'83031a000c3ffd8463455833030682634e5a44182f' The peer responds with immediate acceptance. Note that no objective is needed, because the initiator's request was accepted without change: [6, 802813, ] [M_END , 802813, [O_ACCEPT]] h'83061a000c3ffd811865' D.5. Complete Negotiation Example Again the initiator unicasts a request: [3, 13767778, ["EX3", 3, 6, ["NZD", 410]]] [M_REQ_NEG, 13767778, ["EX3", F_NEG_bits, 6, ["NZD", 410]]] h'83031a00d214628463455833030682634e5a4419019a' The responder starts to negotiate (making an offer): [5, 13767778, ["EX3", 3, 6, ["NZD", 80]]] [M_NEGOTIATE, 13767778, ["EX3", F_NEG_bits, 6, ["NZD", 80]]] h'83051a00d214628463455833030682634e5a441850' The initiator continues to negotiate (reducing its request, and note that the loop count is decremented): [5, 13767778, ["EX3", 3, 5, ["NZD", 307]]] [M_NEGOTIATE, 13767778, ["EX3", F_NEG_bits, 5, ["NZD", 307]]] h'83051a00d214628463455833030582634e5a44190133' The responder asks for more time: [7, 13767778, 34965] [M_WAIT, 13767778, 34965] h'83071a00d21462198895' The responder continues to negotiate (increasing its offer): Bormann, et al. Expires October 1, 2017 [Page 73] Internet-Draft GRASP March 2017 [5, 13767778, ["EX3", 3, 4, ["NZD", 120]]] [M_NEGOTIATE, 13767778, ["EX3", F_NEG_bits, 4, ["NZD", 120]]] h'83051a00d214628463455833030482634e5a441878' The initiator continues to negotiate (reducing its request): [5, 13767778, ["EX3", 3, 3, ["NZD", 246]]] [M_NEGOTIATE, 13767778, ["EX3", F_NEG_bits, 3, ["NZD", 246]]] h'83051a00d214628463455833030382634e5a4418f6' The responder refuses to negotiate further: [6, 13767778, [102, "Insufficient funds"]] [M_END , 13767778, [O_DECLINE, "Insufficient funds"]] h'83061a00d2146282186672496e73756666696369656e742066756e6473' This negotiation has failed. If either side had sent [M_END, 13767778, [O_ACCEPT]] it would have succeeded, converging on the objective value in the preceding M_NEGOTIATE. Note that apart from the initial M_REQ_NEG, the process is symmetrical. Appendix E. Capability Analysis of Current Protocols This appendix discusses various existing protocols with properties related to the requirements described in Section 2. The purpose is to evaluate whether any existing protocol, or a simple combination of existing protocols, can meet those requirements. Numerous protocols include some form of discovery, but these all appear to be very specific in their applicability. Service Location Protocol (SLP) [RFC2608] provides service discovery for managed networks, but requires configuration of its own servers. DNS-SD [RFC6763] combined with mDNS [RFC6762] provides service discovery for small networks with a single link layer. [RFC7558] aims to extend this to larger autonomous networks but this is not yet standardized. However, both SLP and DNS-SD appear to target primarily application layer services, not the layer 2 and 3 objectives relevant to basic network configuration. Both SLP and DNS-SD are text-based protocols. Routing protocols are mainly one-way information announcements. The receiver makes independent decisions based on the received information and there is no direct feedback information to the announcing peer. This remains true even though the protocol is used in both directions between peer routers; there is state synchronization, but no negotiation, and each peer runs its route calculations independently. Bormann, et al. Expires October 1, 2017 [Page 74] Internet-Draft GRASP March 2017 Simple Network Management Protocol (SNMP) [RFC3416] uses a command/ response model not well suited for peer negotiation. Network Configuration Protocol (NETCONF) [RFC6241] uses an RPC model that does allow positive or negative responses from the target system, but this is still not adequate for negotiation. There are various existing protocols that have elementary negotiation abilities, such as Dynamic Host Configuration Protocol for IPv6 (DHCPv6) [RFC3315], Neighbor Discovery (ND) [RFC4861], Port Control Protocol (PCP) [RFC6887], Remote Authentication Dial In User Service (RADIUS) [RFC2865], Diameter [RFC6733], etc. Most of them are configuration or management protocols. However, they either provide only a simple request/response model in a master/slave context or very limited negotiation abilities. There are some signaling protocols with an element of negotiation. For example Resource ReSerVation Protocol (RSVP) [RFC2205] was designed for negotiating quality of service parameters along the path of a unicast or multicast flow. RSVP is a very specialised protocol aimed at end-to-end flows. However, it has some flexibility, having been extended for MPLS label distribution [RFC3209]. A more generic design is General Internet Signalling Transport (GIST) [RFC5971], but it is complex, tries to solve many problems, and is also aimed at per-flow signaling across many hops rather than at device-to-device signaling. However, we cannot completely exclude extended RSVP or GIST as a synchronization and negotiation protocol. They do not appear to be directly useable for peer discovery. RESTCONF [RFC8040] is a protocol intended to convey NETCONF information expressed in the YANG language via HTTP, including the ability to transit HTML intermediaries. While this is a powerful approach in the context of centralised configuration of a complex network, it is not well adapted to efficient interactive negotiation between peer devices, especially simple ones that might not include YANG processing already. The Distributed Node Consensus Protocol (DNCP) [RFC7787] is defined as a generic form of state synchronization protocol, with a proposed usage profile being the Home Networking Control Protocol (HNCP) [RFC7788] for configuring Homenet routers. A specific application of DNCP for autonomic networking was proposed in [I-D.stenberg-anima-adncp]. DNCP "is designed to provide a way for each participating node to publish a set of TLV (Type-Length-Value) tuples, and to provide a shared and common view about the data published... DNCP is most suitable for data that changes only infrequently... If constant rapid Bormann, et al. Expires October 1, 2017 [Page 75] Internet-Draft GRASP March 2017 state changes are needed, the preferable choice is to use an additional point-to-point channel..." Specific features of DNCP include: o Every participating node has a unique node identifier. o DNCP messages are encoded as a sequence of TLV objects, sent over unicast UDP or TCP, with or without (D)TLS security. o Multicast is used only for discovery of DNCP neighbors when lower security is acceptable. o Synchronization of state is maintained by a flooding process using the Trickle algorithm. There is no bilateral synchronization or negotiation capability. o The HNCP profile of DNCP is designed to operate between directly connected neighbors on a shared link using UDP and link-local IPv6 addresses. DNCP does not meet the needs of a general negotiation protocol, because it is designed specifically for flooding synchronization. Also, in its HNCP profile it is limited to link-local messages and to IPv6. However, at the minimum it is a very interesting test case for this style of interaction between devices without needing a central authority, and it is a proven method of network-wide state synchronization by flooding. The Server Cache Synchronization Protocol (SCSP) [RFC2334] also describes a method for cache synchronization and cache replication among a group of nodes. A proposal was made some years ago for an IP based Generic Control Protocol (IGCP) [I-D.chaparadza-intarea-igcp]. This was aimed at information exchange and negotiation but not directly at peer discovery. However, it has many points in common with the present work. None of the above solutions appears to completely meet the needs of generic discovery, state synchronization and negotiation in a single solution. Many of the protocols assume that they are working in a traditional top-down or north-south scenario, rather than a fluid peer-to-peer scenario. Most of them are specialized in one way or another. As a result, we have not identified a combination of existing protocols that meets the requirements in Section 2. Also, we have not identified a path by which one of the existing protocols could be extended to meet the requirements. Bormann, et al. Expires October 1, 2017 [Page 76] Internet-Draft GRASP March 2017 Authors' Addresses Carsten Bormann Universitaet Bremen TZI Postfach 330440 D-28359 Bremen Germany Email: email@example.com Brian Carpenter (editor) Department of Computer Science University of Auckland PB 92019 Auckland 1142 New Zealand Email: firstname.lastname@example.org Bing Liu (editor) Huawei Technologies Co., Ltd Q14, Huawei Campus No.156 Beiqing Road Hai-Dian District, Beijing 100095 P.R. China Email: email@example.com Bormann, et al. Expires October 1, 2017 [Page 77]