Network Working Group B. Carpenter
Internet-Draft Univ. of Auckland
Intended status: Standards Track B. Liu
Expires: July 10, 2015 Huawei Technologies Co., Ltd
January 6, 2015
A Generic Discovery and Negotiation Protocol for Autonomic Networking
draft-carpenter-anima-gdn-protocol-01
Abstract
This document establishes requirements for a protocol that enables
intelligent devices to dynamically discover peer devices, to
synchronize state with them, and to negotiate mutual configurations
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 as
possible alternatives.
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 July 10, 2015.
Copyright Notice
Copyright (c) 2015 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
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
Carpenter & Liu Expires July 10, 2015 [Page 1]
Internet-Draft GDN Protocol January 2015
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 . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Requirements for Discovery . . . . . . . . . . . . . . . 4
2.2. Requirements for Synchronization and Negotiation
Capability . . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Specific Technical Requirements . . . . . . . . . . . . . 6
3. GDNP Protocol Overview . . . . . . . . . . . . . . . . . . . 7
3.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 7
3.2. High-Level Design Choices . . . . . . . . . . . . . . . . 9
3.3. GDNP Protocol Basic Properties and Mechanisms . . . . . . 12
3.3.1. Discovery Mechanism and Procedures . . . . . . . . . 12
3.3.2. Certificate-based Security Mechanism . . . . . . . . 14
3.3.3. Negotiation Procedures . . . . . . . . . . . . . . . 17
3.3.4. Synchronization Procedure . . . . . . . . . . . . . . 18
3.4. GDNP Constants . . . . . . . . . . . . . . . . . . . . . 19
3.5. Device Identifier and Certificate Tag . . . . . . . . . . 19
3.6. Session Identifier (Session ID) . . . . . . . . . . . . . 20
3.7. GDNP Messages . . . . . . . . . . . . . . . . . . . . . . 20
3.7.1. GDNP Message Format . . . . . . . . . . . . . . . . . 20
3.7.2. Discovery Message . . . . . . . . . . . . . . . . . . 21
3.7.3. Response Message . . . . . . . . . . . . . . . . . . 21
3.7.4. Request Message . . . . . . . . . . . . . . . . . . . 22
3.7.5. Negotiation Message . . . . . . . . . . . . . . . . . 22
3.7.6. Negotiation-ending Message . . . . . . . . . . . . . 22
3.7.7. Confirm-waiting Message . . . . . . . . . . . . . . . 22
3.8. GDNP General Options . . . . . . . . . . . . . . . . . . 23
3.8.1. Format of GDNP Options . . . . . . . . . . . . . . . 23
3.8.2. Divert Option . . . . . . . . . . . . . . . . . . . . 23
3.8.3. Accept Option . . . . . . . . . . . . . . . . . . . . 24
3.8.4. Decline Option . . . . . . . . . . . . . . . . . . . 24
3.8.5. Waiting Time Option . . . . . . . . . . . . . . . . . 25
3.8.6. Certificate Option . . . . . . . . . . . . . . . . . 26
3.8.7. Signature Option . . . . . . . . . . . . . . . . . . 26
3.8.8. Locator Options . . . . . . . . . . . . . . . . . . . 27
3.9. Discovery Objective Option . . . . . . . . . . . . . . . 29
3.10. Negotiation and Synchronization Objective Options and
Considerations . . . . . . . . . . . . . . . . . . . . . 29
3.10.1. Organizing of GDNP Options . . . . . . . . . . . . . 30
3.10.2. Vendor Specific Options . . . . . . . . . . . . . . 30
3.10.3. Experimental Options . . . . . . . . . . . . . . . . 31
Carpenter & Liu Expires July 10, 2015 [Page 2]
Internet-Draft GDN Protocol January 2015
3.11. Items for Future Work . . . . . . . . . . . . . . . . . . 31
4. Security Considerations . . . . . . . . . . . . . . . . . . . 33
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 34
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 36
7. Change log [RFC Editor: Please remove] . . . . . . . . . . . 36
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 36
8.1. Normative References . . . . . . . . . . . . . . . . . . 37
8.2. Informative References . . . . . . . . . . . . . . . . . 37
Appendix A. Capability Analysis of Current Protocols . . . . . . 39
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 42
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
[I-D.irtf-nmrg-autonomic-network-definitions] and
[I-D.irtf-nmrg-an-gap-analysis]. In order to fulfil autonomy,
devices that embody autonomic service agents need to be able to
discover each other, to synchronize state with each other, and to
negotiate parameters and resources directly with each other. There
is no restriction on the type of parameters and resources concerned,
which include very basic information needed for addressing and
routing, as well as anything else that might be configured in a
conventional network.
Following this Introduction, Section 2 describes the requirements for
network device discovery, synchronization and negotiation.
Negotiation is an iterative process, requiring multiple message
exchanges forming a closed loop between the negotiating devices.
State synchronization, when needed, can be effected as a special case
of negotiation. Section 3.2 describes a behavior model for a
protocol intended to support discovery, synchronization and
negotiation. The design of Generic Discovery and Negotiation
Protocol (GDNP) in Section 3 of this document is mainly based on this
behavior model. The relevant capabilities of various existing
protocols are reviewed in Appendix A.
The proposed discovery mechanism is oriented towards synchronization
and negotiation objectives. It is based on a neighbor discovery
process, but also supports diversion to off-link peers. Although
many negotiations will occur between horizontally distributed peers,
many target scenarios are hierarchical networks, which is the
predominant structure of current large-scale networks. However, when
a device starts up with no pre-configuration, it has no knowledge of
Carpenter & Liu Expires July 10, 2015 [Page 3]
Internet-Draft GDN Protocol January 2015
a hierarchical superior. 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 a professionally managed network.
Therefore, the discovery mechanism needs to be able to bootstrap
itself without making any prior assumptions about network structure.
Because GDNP can be used to perform a decision process among
distributed devices or between networks, it adopts a tight
certificate-based security mechanism, which needs a Public Key
Infrastructure (PKI) [RFC5280] system. The PKI may be managed by an
operator or be autonomic.
It is understood that in realistic deployments, not all devices will
support GDNP. Such mixed scenarios are not discussed in this
specification.
2. Requirement Analysis of Discovery, Synchronization and Negotiation
This section discusses the requirements for discovery, negotiation
and synchronization capabilities.
2.1. Requirements for Discovery
In an autonomic network we must assume that when a device starts up
it has no information about any peer devices. In some cases, when a
new user session starts up, the device concerned may again lack
information about relevant peer devices. 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.
Therefore a basic requirement is that there must be a mechanism by
which a device can separately discover peer devices for each of the
technical objectives that it needs to manage or configure. 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 peer devices 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 support
both on-link discovery and off-link discovery of peers that support
specific technical objectives.
The relevant peer devices 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. In many
scenarios, the discovery process may be followed by a synchronization
or negotiation process. Therefore, a discovery objective may be
Carpenter & Liu Expires July 10, 2015 [Page 4]
Internet-Draft GDN Protocol January 2015
associated with one or more synchronization or negotiation
objectives.
When a device first starts up, it has no knowledge of the network
structure. Therefore the discovery process must be able to support
any network scenario, assuming only that the device concerned is
bootstrapped from factory condition.
In some networks, as mentioned above, there will be some hierarchical
structure, at least for certain synchronization or negotiation
objectives. A special case of discovery is that each device must be
able to discover its hierarchical superior for each such objective
that it is capable of handling. This is part of the more general
requirement to discover off-link devices.
During initialisation, a device must be able to discover the
appropriate trust anchor, i.e. the appropriate PKI authority.
Logically, this is just a specific case of discovery. However, it
might be a special case requiring its own solution. In any case, the
trust anchor must be discovered before the security environment is
completely established. This question requires further study and is
the subject of [I-D.pritikin-anima-bootstrapping-keyinfra]. In
addition, depending on the type of network involved, discovery of
other central functions might be needed, such as the Network
Operations Center (NOC) [I-D.eckert-anima-stable-connectivity].
2.2. Requirements for Synchronization and Negotiation Capability
We start by considering routing protocols, the closest approximation
to autonomic networking in widespread use. Routing protocols use a
largely autonomic model based on distributed devices that communicate
iteratively with each other. However, routing is mainly based on
one-way information synchronization (in either direction), rather
than on bi-directional negotiation. The focus is reachability, so
current routing protocols only consider simple link status, i.e., up
or down. More information, such as latency, congestion, capacity,
and particularly unused capacity, would be helpful to get better path
selection and utilization rate. Also, autonomic networks need to be
able to manage many more dimensions, such as security settings, power
saving, load balancing, etc. A basic requirement for the protocol is
therefore the ability to represent, discover, synchronize and
negotiate almost any kind of network parameter.
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 a
Carpenter & Liu Expires July 10, 2015 [Page 5]
Internet-Draft GDN Protocol January 2015
requirement for the protocol is to be capable of being installed in
any device that would otherwise need human intervention.
Human intervention in large networks is often replaced by use of a
top-down network management system (NMS). It therefore follows that
a requirement for the protocol is to be capable of being installed in
any device that would otherwise be managed by an NMS, and that it can
co-exist with an NMS.
Since the goal is to minimize human intervention, it is necessary
that the network can in effect "think ahead" before changing its
parameters. In other words there must be a possibility of
forecasting the effect of a change. Stated differently, the protocol
must be capable of supporting a "dry run" of a changed configuration
before actually installing the change.
Status information and traffic 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.
Recovery from faults and identification of faulty devices should be
as automatic as possible. The protocol needs to be capable of
detecting unexpected events such a negotiation counterpart failing,
so that all devices concerned can initiate a recovery process.
The protocol needs to be able to deal with a wide variety of
technical objectives, covering any type of network parameter.
Therefore the protocol will need either an explicit information model
describing its messages, or at least a flexible and extensible
message format. One design consideration is whether to adopt an
existing information model or to design a new one. Another
consideration is whether to be able to carry some or all of the
message formats used by existing configuration protocols.
2.3. Specific Technical Requirements
To be a generic platform, the protocol should be IP version
independent. In other words, it should be able to run over IPv6 and
IPv4. Its messages and general options should be neutral with
respect to the IP version. However, some functions, such as
multicasting or broadcasting on a link, might need to be IP version
dependent. In case of doubt, IPv6 should be preferred.
The protocol must be able to access off-link counterparts, i.e., must
not be restricted to link-local operation.
Carpenter & Liu Expires July 10, 2015 [Page 6]
Internet-Draft GDN Protocol January 2015
The negotiation process must be guaranteed to terminate (with success
or failure) and if necessary it must contain tie-breaking rules for
each technical objective that requires them.
Dependencies: In order to decide a configuration on 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 among
negotiation or synchronization procedures. Thus, there need to be
clear boundaries and convergence mechanisms for these negotiation
dependencies. Also some mechanisms are needed to avoid loop
dependencies.
Policy constraints: There must be provision for general policy intent
rules to be applied by all devices in the network (e.g., security
rules, prefix length, resource sharing rules). However, policy
intent distribution might not use the negotiation protocol itself.
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
intervention must be possible (e.g. to freeze synchronization or
negotiation in a mis-behaving device). These features may not use
the negotiation protocol itself.
The protocol needs to be fully secure against forged messages and
man-in-the middle attacks, and as secure as reasonably possible
against denial of service attacks. It needs to be capable of
encryption in order to resist unwanted monitoring, although this
capability may not be required in all deployments.
3. GDNP 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.
The following terms are used throughout this document:
Carpenter & Liu Expires July 10, 2015 [Page 7]
Internet-Draft GDN Protocol January 2015
o Discovery: a process by which a device discovers peer devices
according to a specific discovery objective. The discovery
results may be different according to the different discovery
objectives. The discovered peer devices may later be used as
negotiation counterparts or as sources of synchronization data.
o Negotiation: a process by which two (or more) devices interact
iteratively to agree on parameter settings that best satisfy the
objectives of one or more devices.
o State Synchronization: a process by which two (or more) devices
interact to agree on the current state of parameter values stored
in each device. This is a special case of negotiation in which
information is exchanged but the devices do not request their
peers to change parameter settings. All other definitions apply
to both negotiation and synchronization.
o Discovery Objective: a specific network functionality, network
element role or type of autonomic service agent (TBD) which the
discovery initiator intends to discover. One device may support
multiple discovery objectives. A discovery objective may be in
one-to-one correspondence with a synchronization objective or a
negotiation objective, or it may correspond to a certain group of
such objectives.
o Discovery Initiator: a device that spontaneously starts discovery
by sending a discovery message referring to a specific discovery
objective.
o Discovery Responder: a peer device which responds to the discovery
objective initiated by the discovery initiator.
o Synchronization Objective: specific technical content, which needs
to be synchronized among a number of devices. It is naturally
based on a specific service or function or action. It could be a
logical, numeric, or string value or a more complex data
structure.
o Synchronization Initiator: a device that spontaneously starts
synchronization by sending a request message referring to a
specific synchronization objective.
o Synchronization Responder: a peer device which responds with the
value of a synchronization objective.
o Negotiation Objective: specific technical content, which needs to
be decided in coordination with another network device. It is
naturally based on a specific service or function or action. It
Carpenter & Liu Expires July 10, 2015 [Page 8]
Internet-Draft GDN Protocol January 2015
could be a logical, numeric, or string value or a more complex
data structure.
o Negotiation Initiator: a device that spontaneously starts
negotiation by sending a request message referring to a specific
negotiation objective.
o Negotiation Counterpart: a peer device with which the Negotiation
Initiator negotiates a specific negotiation objective.
o Device Identifier: a public key, which identifies the device in
GDNP messages. It is assumed that its associated private key is
maintained in the device only.
o Device Certificate: A certificate for a single device, also the
identifier of the device, further described in Section 3.5.
o Device Certificate Tag: a tag, which is bound to the device
identifier. It is used to present a Device Certificate in short
form.
3.2. High-Level Design Choices
This section describes a behavior model and some considerations for
designing a generic discovery, synchronization and negotiation
protocol, which can act as a platform for different technical
objectives.
NOTE: This protocol is described here in a stand-alone fashion as a
proof of concept. An elementary version has been prototyped by
Huawei and the Beijing University of Posts and Telecommunications.
However, this is not yet a definitive proposal for IETF adoption. In
particular, adaptation and extension of one of the protocols
discussed in Appendix A might be an option. Also, the security model
outlined below would in practice be part of a general security
mechanism in an autonomic control plane
[I-D.behringer-anima-autonomic-control-plane]. This whole
specification is subject to change as a result.
o A generic platform
The protocol is designed as a generic platform, which is
independent from the synchronization or negotiation contents. It
takes care of the general intercommunication between counterparts.
The technical contents will vary according to the various
synchronization or negotiation objectives and the different pairs
of counterparts.
Carpenter & Liu Expires July 10, 2015 [Page 9]
Internet-Draft GDN Protocol January 2015
o Security infrastructure and trust relationship
Because this negotiation protocol may directly cause changes to
device configurations and bring significant impacts to a running
network, this protocol is based on a restrictive security
infrastructure, allowing it to be trusted and monitored so that
every device in this negotiation system behaves well and remains
well protected.
On the other hand, a limited negotiation model might be deployed
based on a limited trust relationship. For example, between two
administrative domains, devices might also exchange limited
information and negotiate some particular configurations based on
a limited conventional or contractual trust relationship.
o Discovery, synchronization and negotiation 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. These processes can also be performed independently
when appropriate.
o A uniform pattern for technical contents
The synchronization and negotiation contents are defined according
to a uniform pattern. They could be carried either in TLV (Type,
Length and Value) format or in payloads described by a flexible
language. The initial protocol design uses the TLV approach. The
format is extensible for unknown future requirements.
o A conservative model for synchronization
Synchronization across a number of nodes is not a new problem and
the Trickle model that is already known to be effective and
efficient is adopted.
o A simple initiator/responder model for negotiation
Multi-party negotiations are too complicated to be modeled and
there might be too many dependencies among the parties to converge
efficiently. A simple initiator/responder model is more feasible
and can complete multiple-party negotiations by indirect steps.
Carpenter & Liu Expires July 10, 2015 [Page 10]
Internet-Draft GDN Protocol January 2015
o Organizing of synchronization or negotiation content
Naturally, the technical content will be organized according to
the relevant function or service. The content from different
functions or services is kept independent from each other. They
are not combined into a single option or single session because
these contents may be negotiated or synchronized with different
counterparts or may be different in response time.
o Self aware network device
Every network device will be pre-loaded with various functions and
be aware of its own capabilities, typically decided by the
hardware, firmware or pre-installed software. Its exact role may
depend on the surrounding network behaviors, which may include
forwarding behaviors, aggregation properties, topology location,
bandwidth, tunnel or translation properties, etc. The surrounding
topology will depend on the network planning. Following an
initial discovery phase, the device properties and those of its
neighbors are the foundation of the synchronization or negotiation
behavior of a specific device. A device has no pre-configuration
for the particular network in which it is installed.
o Requests and responses in negotiation procedures
The initiator can negotiate with its relevant negotiation
counterpart devices, which may be different according to the
specific negotiation objective. It can request relevant
information from the negotiation counterpart so that it can decide
its local configuration to give the most coordinated performance.
It can request the negotiation counterpart to make a matching
configuration in order to set up a successful communication with
it. It can request certain simulation or forecast results by
sending some dry run conditions.
Beyond the traditional yes/no answer, the responder can reply with
a suggested alternative if its answer is 'no'. This would start a
bi-directional negotiation ending in a compromise between the two
devices.
o Convergence of negotiation procedures
To enable convergence, when a responder makes a suggestion of a
changed condition in a negative reply, it should be as close as
possible to the original request or previous suggestion. The
Carpenter & Liu Expires July 10, 2015 [Page 11]
Internet-Draft GDN Protocol January 2015
suggested value of the third or later negotiation steps should be
chosen between the suggested values from the last two negotiation
steps. In any case there must be a mechanism to guarantee
convergence (or failure) in a small number of steps, such as a
timeout or maximum number of iterations.
* End of negotiation
A limited number of rounds, for example three, or a timeout, is
needed on each device for each negotiation objective. It may
be an implementation choice, a pre-configurable parameter, or a
network-wide policy intent. These choices might vary between
different types of autonomic service agent. Therefore, the
definition of each negotiation objective MUST clearly specify
this, so that the negotiation can always be terminated
properly.
* Failed negotiation
There must be a well-defined procedure for concluding that a
negotiation cannot succeed, and if so deciding what happens
next (deadlock resolution, tie-breaking, or revert to best-
effort service). Again, this MUST be specified for individual
negotiation objectives, as an implementation choice, a pre-
configurable parameter, or a network-wide policy intent.
3.3. GDNP Protocol Basic Properties and Mechanisms
3.3.1. Discovery Mechanism and Procedures
o Separated discovery and negotiation mechanisms
Although discovery and negotiation or synchronization are
defined together in the GDNP, they are separated mechanisms.
The discovery process could run independently from the
negotiation or synchronization process. Upon receiving a
discovery (Section 3.7.2) or request (Section 3.7.4) message,
the recipient device should return a message in which it either
indicates itself as a discovery responder or diverts the
initiator towards another more suitable device.
The discovery objective could be network functionalities, role-
based network elements or service agents (TBD). The discovery
results could be utilized by the negotiation protocol to decide
which device the initiator will negotiate with.
Carpenter & Liu Expires July 10, 2015 [Page 12]
Internet-Draft GDN Protocol January 2015
o Discovery Procedures
Discovery starts as on-link operation. The Divert option can
tell the discovery initiator to contact an off-link discovery
objective device. Every DISCOVERY message is sent by a
discovery initiator to the ALL_GDNP_NEIGHBOR multicast address
(Section 3.4). Every network device that supports the GDNP
always listens to a well-known transport port to capture the
discovery messages.
If the neighbor device supports the requested discovery
objective, it MAY respond with a Response message
(Section 3.7.3) with locator option(s). Otherwise, if the
neigbor device has cached information about a device that
supports the requested discovery objective (usually because it
discovered the same objective before), it SHOULD respond with a
Response message with a Divert option pointing to the
appropriate Discovery Responder.
After a GDNP device successfully discovers a Discovery
Responder supporting a specific objective, it MUST cache this
information. This cache record MAY be used for future
negotiation or synchronization, and SHOULD be passed on when
appropriate as a Divert option to another Discovery Initiator.
A GDNP device with multiple link-layer interfaces (typically a
router) MUST support discovery on all interfaces. If it
receives a DISCOVERY message on a given interface for a
specific objective that it does not support and for which it
has not previously discovered a Discovery Responder, it MUST
relay the query by re-issuing the same DISCOVERY message on its
other interfaces. Togther with the caching mechanism, this
should be sufficient to support most network bootstrapping
scenarios.
o A complete discovery process will start with multicast on the
local link; a neighbor might divert it to an off-link destination,
which could be a default higher-level gateway in a hierarchical
network. Then discovery would continue with a unicast to that
gateway; if that gateway is still not the right counterpart, it
should divert to another device, which is in principle closer to
the right counterpart. Finally the right counterpart responds to
start the negotiation or synchronization process.
o Rapid Mode (Discovery/Negotiation binding)
A Discovery message MAY include one or more Negotiation
Objective option(s). This allows a rapid mode of negotiation
Carpenter & Liu Expires July 10, 2015 [Page 13]
Internet-Draft GDN Protocol January 2015
described in Section 3.3.3. A similar mechanism is defined for
synchronization.
3.3.2. Certificate-based Security Mechanism
A certificate-based security mechanism provides security properties
for GDNP:
o the identity of a GDNP message sender can be verified by a
recipient.
o the integrity of a GDNP message can be checked by the recipient of
the message.
o anti-replay protection can be assured by the GDNP message
recipient.
The authority of the GDNP message sender depends on a Public Key
Infrastructure (PKI) system with a Certification Authority (CA),
which should normally be run by the network operator. In the case of
a network with no operator, such as a small office or home network,
the PKI itself needs to be established by an autonomic process, which
is out of scope for this specification.
A Request message MUST carry a Certificate option, defined in
Section 3.8.6. The first Negotiation Message, responding to a
Request message, SHOULD also carry a Certificate option. Using these
messages, recipients build their certificate stores, indexed by the
Device Certificate Tags included in every GDNP message. This process
is described in more detail below.
Every message MUST carry a signature option (Section 3.8.7).
For now, the authors do not think packet size is a problem. In this
GDNP specification, there SHOULD NOT be multiple certificates in a
single message. The current most used public keys are 1024/2048
bits; some may reach 4096. With overhead included, a single
certificate is less than 500 bytes. Messages are expected to be far
shorter than the normal packet MTU within a modern network.
3.3.2.1. Support for algorithm agility
Hash functions are used to provide message integrity checks. In
order to provide a means of addressing problems that may emerge in
the future with existing hash algorithms, as recommended in
[RFC4270], a mechanism for negotiating the use of more secure hashes
in the future is provided.
Carpenter & Liu Expires July 10, 2015 [Page 14]
Internet-Draft GDN Protocol January 2015
In addition to hash algorithm agility, a mechanism for signature
algorithm agility is also provided.
The support for algorithm agility in this document is mainly a
unilateral notification mechanism from sender to recipient. If the
recipient does not support the algorithm used by the sender, it
cannot authenticate the message. Senders in a single administrative
domain are not required to upgrade to a new algorithm simultaneously.
So far, the algorithm agility is supported by one-way notification,
rather than negotiation mode. As defined in Section 3.8.7, the
sender notifies the recipient what hash/signature algorithms it uses.
If the responder doesn't know a new algorithm used by the sender, the
negotiation request would fail. In order to establish a negotiation
session, the sender MAY fall back to an older, less preferred
algorithm. Certificates and network policy intent SHOULD limit the
choice of algorithms.
3.3.2.2. Message validation on reception
When receiving a GDNP message, a recipient MUST discard the GDNP
message if the Signature option is absent, or the Certificate option
is in a Request Message.
For the Request message and the Response message with a Certification
Option, the recipient MUST first check the authority of this sender
following the rules defined in [RFC5280]. After successful authority
validation, an implementation MUST add the sender's certification
into the local trust certificate record indexed by the associated
Device Certificate Tag (Section 3.5).
The recipient MUST now authenticate the sender by verifying the
Signature and checking a timestamp, as specified in Section 3.3.2.3.
The order of two procedures is left as an implementation decision.
It is RECOMMENDED to check timestamp first, because signature
verification is much more computationally expensive.
The signature field verification MUST show that the signature has
been calculated as specified in Section 3.8.7. The public key used
for signature validation is obtained from the certificate either
carried by the message or found from a local trust certificate record
by searching the message-carried Device Certificate Tag.
Only the messages that get through both the signature verifications
and timestamp check are accepted and continue to be handled for their
contained GDNP options. Messages that do not pass the above tests
MUST be discarded as insecure messages.
Carpenter & Liu Expires July 10, 2015 [Page 15]
Internet-Draft GDN Protocol January 2015
3.3.2.3. TimeStamp checking
Recipients SHOULD be configured with an allowed timestamp Delta
value, a "fuzz factor" for comparisons, and an allowed clock drift
parameter. The recommended default value for the allowed Delta is
300 seconds (5 minutes); for fuzz factor 1 second; and for clock
drift, 0.01 second.
The timestamp is defined in the Signature Option, Section 3.8.7. To
facilitate timestamp checking, each recipient SHOULD store the
following information for each sender:
o The receive time of the last received and accepted GDNP message.
This is called RDlast.
o The time stamp in the last received and accepted GDNP message.
This is called TSlast.
An accepted GDNP message is any successfully verified (for both
timestamp check and signature verification) GDNP message from the
given peer. It initiates the update of the above variables.
Recipients MUST then check the Timestamp field as follows:
o When a message is received from a new peer (i.e., one that is not
stored in the cache), the received timestamp, TSnew, is checked,
and the message is accepted if the timestamp is recent enough to
the reception time of the packet, RDnew:
-Delta < (RDnew - TSnew) < +Delta
The RDnew and TSnew values SHOULD be stored in the cache as RDlast
and TSlast.
o When a message is received from a known peer (i.e., one that
already has an entry in the cache), the timestamp is checked
against the previously received GDNP message:
TSnew + fuzz > TSlast + (RDnew - RDlast) x (1 - drift) - fuzz
If this inequality does not hold, the recipient SHOULD silently
discard the message. If, on the other hand, the inequality holds,
the recipient SHOULD process the message.
Moreover, if the above inequality holds and TSnew > TSlast, the
recipient SHOULD update RDlast and TSlast. Otherwise, the
recipient MUST NOT update RDlast or TSlast.
Carpenter & Liu Expires July 10, 2015 [Page 16]
Internet-Draft GDN Protocol January 2015
An implementation MAY use some mechanism such as a timestamp cache to
strengthen resistance to replay attacks. When there is a very large
number of nodes on the same link, or when a cache filling attack is
in progress, it is possible that the cache holding the most recent
timestamp per sender will become full. In this case, the node MUST
remove some entries from the cache or refuse some new requested
entries. The specific policy as to which entries are preferred over
others is left as an implementation decision.
3.3.3. Negotiation Procedures
A negotiation initiator sends a negotiation request to counterpart
devices, which may be different according to different negotiation
objectives. It may request relevant information from the negotiation
counterpart so that it can decide its local configuration to give the
most coordinated performance. This would be sufficient in a case
where the required function is limited to state synchronization. It
may additionally request the negotiation counterpart to make a
matching configuration in order to set up a successful communication
with it. It may request a certain simulation or forecast result by
sending some dry run conditions. The details, including the
distinction between dry run and an actual configuration change, will
be defined separately for each type of negotiation objective.
If the counterpart can immediately apply the requested configuration,
it will give an immediate positive (accept) answer. This will end
the negotiation phase immediately. Otherwise, it will 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 to reach a compromise between the two network
devices.
The negotiation procedure is ended when one of the negotiation peers
sends a Negotiation Ending message, which contains an accept or
decline option and does not need a response from the negotiation
peer.
A negotiation procedure concerns one objective and one counterpart.
Both the initiator and the counterpart may take part in simultaneous
negotiations with various other devices, or in simultaneous
negotiations about different objectives. Thus, GDNP 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.
Rapid Mode (Discovery/Negotiation linkage)
Carpenter & Liu Expires July 10, 2015 [Page 17]
Internet-Draft GDN Protocol January 2015
A Discovery message MAY include one or more Negotiation Objective
option(s). In this case the Discovery message also acts as a
Request message to indicate to the Discovery Responder that it
could directly reply to the Discovery Initiator with a Negotiation
message for rapid processing, if the discovery objective could act
as the corresponding negotiation counterpart. However, the
indication is only advisory not prescriptive.
This rapid mode could reduce the interactions between nodes so
that a higher efficiency could be achieved. This rapid
negotiation function SHOULD be configured off by default and MAY
be configured on or off by policy intent.
3.3.4. Synchronization Procedure
A synchronization initiator sends a synchronization request to
counterpart devices, which may be different according to different
synchronization objectives. The counterpart responds with a Response
message containing the current value(s) of the requested
synchronization objective. No further messages are needed, but
otherwise the procedure operates as a subset of the negotiation
procedure. If no Response message is received, the synchronization
request MAY be repeated after a suitable timeout.
A synchronization responder MAY send an unsolicited Response message
containing a synchronization objective, if and only if the
specification of this objective permits it. This MAY be sent as a
multicast message to the ALL_GDNP_NEIGHBOR multicast address
(Section 3.4). In this case the Trickle algorithm [RFC6206] MUST be
used to avoid excessive multicast traffic. The parameters Imin, Imax
and k of the Trickle algorithm will be specified as part of the
specification of the synchronization objective concerned.
Rapid Mode (Discovery/Synchronization linkage)
A Discovery message MAY include one or more Synchronization
Objective option(s). In this case the Discovery message also acts
as a Request message to indicate to the Discovery Responder that
it could directly reply to the Discovery Initiator with a Response
message with synchronization data for rapid processing, if the
discovery target supports the corresponding synchronization
objective. However, the indication is only advisory not
prescriptive.
This rapid mode could reduce the interactions between nodes so
that a higher efficiency could be achieved. This rapid
synchronization function SHOULD be configured off by default and
MAY be configured on or off by policy intent.
Carpenter & Liu Expires July 10, 2015 [Page 18]
Internet-Draft GDN Protocol January 2015
3.4. GDNP Constants
o ALL_GDNP_NEIGHBOR (TBD1)
A link-local scope multicast address used by a GDNP-enabled device
to discover GDNP-enabled neighbor (i.e., on-link) devices . All
devices that support GDNP are members of this multicast group.
* IPv6 multicast address: TBD1
* IPv4 multicast address: TBD2
o GDNP Listen Port (TBD3)
A UDP port that every GDNP-enabled network device always listens
to.
3.5. Device Identifier and Certificate Tag
A GDNP-enabled Device MUST generate a stable public/private key pair
before it participates in GDNP. There MUST NOT be any way of
accessing the private key via the network or an operator interface.
The device then uses the public key as its identifier, which is
cryptographic in nature. It is a GDNP unique identifier for a GDNP
participant.
It then gets a certificate for this public key, signed by a
Certificate Authority that is trusted by other network devices. The
Certificate Authority SHOULD be managed within the local
administrative domain, to avoid needing to trust a third party. The
signed certificate would be used for authentication of the message
sender. In a managed network, this certification process could be
performed at a central location before the device is physically
installed at its intended location. In an unmanaged network, this
process must be autonomic, including the bootstrap phase.
A 128-bit Device Certifcate Tag, which is generated by taking a
cryptographic hash over the device certificate, is a short
presentation for GDNP messages. It is the index key to find the
device certificate in a recipient's local trusted certificate record.
The tag value is formed by taking a SHA-1 hash algorithm [RFC3174]
over the corresponding device certificate and taking the leftmost 128
bits of the hash result.
Carpenter & Liu Expires July 10, 2015 [Page 19]
Internet-Draft GDN Protocol January 2015
3.6. Session Identifier (Session ID)
A 24-bit opaque value used to distinguish multiple sessions between
the same two devices. A new Session ID MUST be generated for every
new Discovery or Request message, and for every unsolicited Response
message. All follow-up messages in the same discovery,
synchronization or negotiation procedure, which is initiated by the
request message, MUST carry the same Session ID.
The Session ID SHOULD have a very low collision rate locally. It is
RECOMMENDED to be generated by a pseudo-random algorithm using a seed
which is unlikely to be used by any other device in the same network
[RFC4086].
3.7. GDNP Messages
This document defines the following GDNP message format and types.
Message types not listed here are reserved for future use. The
numeric encoding for each message type is shown in parentheses.
3.7.1. GDNP Message Format
All GDNP messages share an identical fixed format header and a
variable format area for options. Every Message carries the Device
Certificate Tag of its sender and a Session ID. Options are
presented serially in the options field, with no padding between the
options. Options are byte-aligned.
The following diagram illustrates the format of GDNP messages:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MESSAGE_TYPE | Session ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Device Certificate Tag |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options (variable length) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
MESSAGE_TYPE: Identifies the GDNP message type. 8-bit.
Session ID: Identifies this negotiation session, as defined in
Section 3.6. 24-bit.
Carpenter & Liu Expires July 10, 2015 [Page 20]
Internet-Draft GDN Protocol January 2015
Device Certificate Tag: Represents the Device Certificate, which
identifies the negotiation devices, as defined in Section 3.5.
The Device Certificate Tag is 128 bit, also defined in
Section 3.5. It is used as index key to find the device
certificate.
Options: GDNP Options carried in this message. Options are defined
starting at Section 3.8.
3.7.2. Discovery Message
DISCOVERY (MESSAGE_TYPE = 1):
A discovery initiator sends a DISCOVERY message to initiate a
discovery process.
The discovery initiator sends the DISCOVERY messages to the link-
local ALL_GDNP_NEIGHBOR multicast address for discovery, and stores
the discovery results (including responding discovery objectives and
corresponding unicast addresses or FQDNs).
A DISCOVERY message MUST include a discovery objective option
(Section 3.9).
A DISCOVERY message MAY include one or more negotiation objective
option(s) (Section 3.10) to indicate to the discovery objective that
it could directly return to the discovery initiatior with a
Negotiation message for rapid processing, if the discovery objective
could act as the corresponding negotiation counterpart, and similarly
for synchronization.
3.7.3. Response Message
RESPONSE (MESSAGE_TYPE = 2):
A node which receives a DISCOVERY message sends a Response message to
respond to a discovery. It MUST contain the same Session ID as the
DISCOVERY message. It MAY include a copy of the discovery objective
from the DISCOVERY message.
If the responding node supports the discovery objective of the
discovery, it MUST include at least one kind of locator option
(Section 3.8.8) to indicate its own location. A combination of
multiple kinds of locator options (e.g. IP address option + 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
Carpenter & Liu Expires July 10, 2015 [Page 21]
Internet-Draft GDN Protocol January 2015
it SHOULD respond to the discovery message with a divert option
(Section 3.8.2) embedding a locator option or a combination of
multiple kinds of locator options which indicate the locator(s) of
the discovery objective.
A node which receives a synchronization request sends a Response
message with the synchronization data. A node MAY send an
unsolicited Response Message with synchronization data and this MAY
be sent to the link-local ALL_GDNP_NEIGHBOR multicast address.
If the response contains synchronization data, this will be in the
form of a GDNP Option for the specific synchronization objective.
3.7.4. Request Message
REQUEST (MESSAGE_TYPE = 3):
A negotiation or synchronization requesting node sends the REQUEST
message to the unicast address (directly stored or resolved from the
FQDN) of the negotiation or synchronization counterpart (selected
from the discovery results).
A request message MUST include the relevant objective option, with
the requested value in the case of negotiation.
3.7.5. Negotiation Message
NEGOTIATION (MESSAGE_TYPE = 4):
A negotiation counterpart sends a NEGOTIATION message in response to
a REQUEST message, a NEGOTIATION message, or a DISCOVERY message in
Rapid Mode. A negotiation process MAY include multiple steps.
3.7.6. Negotiation-ending Message
NEGOTIATION-ENDING (MESSAGE_TYPE = 5):
A negotiation counterpart sends an NEGOTIATION-ENDING message to
close the negotiation. It MUST contain one, but only one of accept/
decline option, defined in Section 3.8.3 and Section 3.8.4. It could
be sent either by the requesting node or the responding node.
3.7.7. Confirm-waiting Message
CONFIRM-WAITING (MESSAGE_TYPE = 6):
A responding node sends a CONFIRM-WAITING message to indicate the
requesting node to wait for a further negotiation response. It might
Carpenter & Liu Expires July 10, 2015 [Page 22]
Internet-Draft GDN Protocol January 2015
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 than the Waiting Time Option
(Section 3.8.5).
3.8. GDNP General Options
This section defines the GDNP general option for the negotiation and
synchronization protocol signalling. Option types 10~63 are reserved
for GDNP general options defined in the future.
3.8.1. Format of GDNP Options
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-code | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-data |
| (option-len octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: An unsigned integer identifying the specific option
type carried in this option.
Option-len: An unsigned integer giving the length of the option-data
field in this option in octets.
Option-data: The data for the option; the format of this data
depends on the definition of the option.
GDNP options are scoped by using encapsulation. If an option
contains other options, the outer Option-len includes the total size
of the encapsulated options, and the latter apply only to the outer
option.
3.8.2. Divert Option
The divert option is used to redirect a GDNP 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 Response messages. If found elsewhere, it SHOULD be
silently ignored.
Carpenter & Liu Expires July 10, 2015 [Page 23]
Internet-Draft GDN Protocol January 2015
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_DIVERT | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator Option(s) of Diversion Device(s) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: OPTION_DIVERT (1).
Option-len: The total length of diverted destination sub-option(s)
in octets.
Locator Option(s) of Diversion Device(s): Embedded Locator Option(s)
(Section 3.8.8) that point to diverted destination device(s).
3.8.3. 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-ending
messages. If found elsewhere, it SHOULD be silently ignored.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_ACCEPT | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: OPTION_ACCEPT (2)
Option-len: 0
3.8.4. 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-ending
messages. If found elsewhere, it SHOULD be silently ignored.
Carpenter & Liu Expires July 10, 2015 [Page 24]
Internet-Draft GDN Protocol January 2015
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_DECLINE | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: OPTION_DECLINE (3)
Option-len: 0
Notes: there are scenarios where a negotiation counterpart wants to
decline the proposed negotiation content and continue the negotiation
process. For these scenarios, the negotiation counterpart SHOULD use
a Response message, with either an objective option that contains at
least one data field with all bits set to 1 to indicate a meaningless
initial value, or a specific objective option that provides further
conditions for convergence.
3.8.5. Waiting Time Option
The waiting time option is used to indicate that the negotiation
counterpart needs to wait for a further negotiation response, since
the processing might need more time than usual or it might depend on
another triggered negotiation.
The waiting time option MUST only be encapsulated in Confirm-waiting
messages. If found elsewhere, it SHOULD be silently ignored.
The counterpart SHOULD send a Response message or another Confirm-
waiting message before the current waiting time expires. If not, the
initiator SHOULD abandon or restart the negotiation procedure, to
avoid an indefinite wait.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_WAITING | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: OPTION_WAITING (4)
Option-len: 4, in octets
Time: Time in milliseconds
Carpenter & Liu Expires July 10, 2015 [Page 25]
Internet-Draft GDN Protocol January 2015
3.8.6. Certificate Option
The Certificate option carries the certificate of the sender. The
format of the Certificate option is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION Certificate | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Certificate (variable length) .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: OPTION_CERT_PARAMETER (5)
Option-len: Length of certificate in octets
Public key: A variable-length field containing a certificate
3.8.7. Signature Option
The Signature option allows public key-based signatures to be
attached to a GDNP message. The Signature option is REQUIRED in
every GDNP message and could be any place within the GDNP message.
It protects the entire GDNP header and options. A TimeStamp has been
integrated in the Signature Option for anti-replay protection. The
format of the Signature option is described as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_SIGNATURE | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HA-id | SA-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp (64-bit) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Signature (variable length) .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: OPTION_SIGNATURE (6)
Carpenter & Liu Expires July 10, 2015 [Page 26]
Internet-Draft GDN Protocol January 2015
Option-len: 12 + Length of Signature field in octets.
HA-id: Hash Algorithm id. The hash algorithm is used for computing
the signature result. This design is adopted in order to provide
hash algorithm agility. The value is from the Hash Algorithm for
GDNP registry in IANA. The initial value assigned for SHA-1 is
0x0001.
SA-id: Signature Algorithm id. The signature algorithm is used for
computing the signature result. This design is adopted in order
to provide signature algorithm agility. The value is from the
Signature Algorithm for GDNP registry in IANA. The initial value
assigned for RSASSA-PKCS1-v1_5 is 0x0001.
Timestamp: The current time of day (NTP-format timestamp [RFC5905]
in UTC (Coordinated Universal Time), a 64-bit unsigned fixed-point
number, in seconds relative to 0h on 1 January 1900.). It can
reduce the danger of replay attacks.
Signature: A variable-length field containing a digital signature.
The signature value is computed with the hash algorithm and the
signature algorithm, as described in HA-id and SA-id. The
signature constructed by using the sender's private key protects
the following sequence of octets:
1. The GDNP message header.
2. All GDNP options including the Signature option (fill the
signature field with zeroes).
The signature field MUST be padded, with all 0, to the next 16 bit
boundary if its size is not an even multiple of 8 bits. The
padding length depends on the signature algorithm, which is
indicated in the SA-id field.
3.8.8. Locator Options
These locator options are used to present a device's or interface's
reachability information. They are Locator IPv4 Address Option,
Locator IPv6 Address Option and Locator FQDN (Fully Qualified Domain
Name) Option.
3.8.8.1. Locator IPv4 address option
Carpenter & Liu Expires July 10, 2015 [Page 27]
Internet-Draft GDN Protocol January 2015
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_LOCATOR_IPV4ADDR | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4-Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: OPTION_LOCATOR_IPV4ADDR (7)
Option-len: 4, in octets
IPv4-Address: The IPv4 address locator of the device/interface
3.8.8.2. Locator IPv6 address option
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_LOCATOR_IPV6ADDR | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6-Address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: OPTION_LOCATOR_IPV6ADDR (8)
Option-len: 16, in octets
IPv6-Address: The IPv6 address locator of the device/interface
Note: A link-local IPv6 address MUST NOT be used when this option is
used within the Divert option.
3.8.8.3. Locator FQDN option
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_FQDN | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Fully Qualified Domain Name |
| (variable length) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Carpenter & Liu Expires July 10, 2015 [Page 28]
Internet-Draft GDN Protocol January 2015
Option-code: OPTION_FQDN (9)
Option-len: Length of Fully Qualified Domain Name in octets
Domain-Name: The Fully Qualified Domain Name of the entity
3.9. Discovery Objective Option
The discovery objective option is to express the discovery objectives
that the initiating node wants to discover and to confirm them in a
Response message.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_DISOBJ | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Expression of Discovery Objectives (TBD) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: OPTION_DISOBJ (TBD)
Option-len: The total length in octets
Expression of Discovery Objectives (TBD): This field is to express
the discovery objectives that the initiating node wants to
discover. It might be network functionality, role-based network
element or service agent.
3.10. Negotiation and Synchronization Objective Options and
Considerations
Negotiation and Synchronization Objective Options MUST be assigned an
option type greater than 64 in the GDNP option table.
The Negotiation Objective Options contain negotiation objectives,
which are various according to different functions/services. They
MUST be carried by Discovery, Request or Negotiation Messages only.
For most scenarios, there SHOULD be initial values in the negotiation
requests. Consequently, the Negotiation Objective options SHOULD
always be completely presented in a Request message,or in a Discovery
message in rapid mode. If there is no initial value, the bits in the
value field SHOULD all be set to 1 to indicate a meaningless value,
unless this is inappropriate for the specific negotiation objective.
Carpenter & Liu Expires July 10, 2015 [Page 29]
Internet-Draft GDN Protocol January 2015
Synchronization Objective Options are similar, but MUST be carried by
Discovery, Request or Response messages only. They include value
fields only in Response messages.
3.10.1. Organizing of GDNP Options
Naturally, a negotiation objective, which is based on a specific
service or function or action, SHOULD be organized as a single GDNP
option. It is NOT RECOMMENDED to organize multiple negotiation
objectives into a single option.
A negotiation objective may have multiple parameters. Parameters can
be categorized into two class: the obligatory ones presented as fixed
fields; and the optional ones presented in TLV sub-options. It is
NOT RECOMMENDED to split parameters in a single objective into
multiple options, unless they have different response periods. An
exception scenario may also be described by split objectives.
3.10.2. Vendor Specific Options
Option codes 128~159 have been reserved for vendor specific options.
Multiple option codes have been assigned because a single vendor
might use multiple options simultaneously. These vendor specific
options are highly likely to have different meanings when used by
different vendors. Therefore, they SHOULD NOT be used without an
explicit human decision and SHOULD NOT be used in unmanaged networks
such as home networks.
There is one general requirement that applies to all vendor specific
options. They MUST start with a field that uniquely identifies the
enterprise that defines the option, in the form of a registered 32
bit Private Enterprise Number (PEN) [I-D.liang-iana-pen]. There is
no default value for this field.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_vendor | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Private Enterprise Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Contents |
. (variable length) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code: OPTION_vendor (128~159)
Option-len: Length of PEN plus option contents in octets
Carpenter & Liu Expires July 10, 2015 [Page 30]
Internet-Draft GDN Protocol January 2015
3.10.3. Experimental Options
Option code 176~191 have been reserved for experimental options.
Multiple option codes 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 option codes are also RECOMMENDED for use in documentation
examples.
3.11. Items for Future Work
There are various design questions that are worthy of more work in
the near future, as listed below:
o UDP vs TCP: For now, this specification has chosen UDP as message
transport mechanism. However, this is not closed yet. UDP is
good for short conversations, fitting the discovery and divert
scenarios well. However, it may have issues with large packets.
TCP is good for stable and long sessions, with a little bit of
time consumption during the session establishment stage. If
messages exceed a reasonable MTU, a TCP mode may be necessary.
o Message encryption: should GDNP messages be (optionally) encrypted
as well as signed, to protect against internal eavesdropping or
monitoring within the network?
o 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.
o Should discuss lifetime of discovery cache, and what to do when
discovery fails (timeout and repeat?).
o Timeout for lost Negotiation Ending and other messages to be
added.
Carpenter & Liu Expires July 10, 2015 [Page 31]
Internet-Draft GDN Protocol January 2015
o We mention convergence mechanisms and say "Also some mechanisms
are needed to avoid loop dependencies." These issues need more
work.
o For replay protection, GDNP 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.
o Would use of MDNS have any impact on the Locator FQDN option?
o Need to add a section describing the minimum requirements for the
specification of an individual discovery, synchronization or
negotiation objective. Maybe a formal information model is
needed.
o Is it reasonable to consider that a Discovery Objective is really
just a set of specific Negotiation and/or Synchronization
Objectives? In other words, if a GDNP node supports Negotiation
and/or Synchronization Objectives A, B and C, then its
corresponding Discovery Objective is a shorthand for "A+B+C".
o Would a DISCOVERY(ANY) mechanism be useful during bootstrapping,
i.e. used by all GDNP-capable routers to find all their neighbours
that support any GDNP discovery objective?.
o Would it be reasonable to allow an unsolicited Response message
with Discovery Objective content, to speed up discovery during
bootstrapping?
o Is there a risk that the relaying of discovery messages
(Section 3.3.1) will lead to loops or multicast storms? At least
we should consider throttling discovery relays to a maximum rate.
Or is there a better method for zeroconf discovery with no
predefined hierarchy?
o Should we consider a distributed or centralised DNS-like approach
to discovery (after the initial discovery needed for
bootstrapping)?
o Need to discuss automatic recovery mechanism as required by
Section 2.2 and management monitoring, alerts and intervention in
general.
o The Decline Option (Section 3.8.4) includes a note that a
counterpart could use a Response message to indicate "Decline but
Carpenter & Liu Expires July 10, 2015 [Page 32]
Internet-Draft GDN Protocol January 2015
try again". That seems strange - why not use a Negotiation
message for this case?
o The Signature Option (Section 3.8.7) 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.
o DoS Attack Protection needs work.
o 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.
However, the authors have not yet decided whether to have a
separate document or have it in this document.
o We currently assume that there is only one counterpart for each
discovery action. If this is false or one negotiation request
receives multiple different responses, how does the initiator
choose between them? Could it split them into multiple follow-up
negotiations?
o Alternatives to TLV format. It may be useful to provide a generic
method of carrying negotiation objectives in a high-level format
such as YANG or XML schema. It may also be useful to provide a
generic method of carrying existing configuration information such
as DHCP(v6) or IPv6 RA messages. These features could be provided
by encapsulating such messages in their own TLVs, but large
messages would definitely need a TCP mode instead of UDP.
4. Security Considerations
It is obvious that 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. GDNP nodes and messages therefore require full
protection.
- Authentication
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 device should be
capable of proving its identity and authenticating its messages.
Carpenter & Liu Expires July 10, 2015 [Page 33]
Internet-Draft GDN Protocol January 2015
GDNP proposes a certificate-based security mechanism to provide
authentication and data integrity protection.
The timestamp mechanism provides an anti-replay function.
Since GDNP is intended to be deployed in a single administrative
domain operating its own trust anchor and CA, there is no need for
a trusted public third party.
- Privacy
Generally speaking, no personal information is expected to be
involved in the negotiation protocol, so there should be no direct
impact on personal privacy. Nevertheless, traffic flow paths,
VPNs, etc. may be negotiated, which could be of interest for
traffic analysis. Also, carriers generally want to conceal
details of their network topology and traffic density from
outsiders. Therefore, since insider attacks cannot be prevented
in a large carrier network, the security mechanism for the
negotiation protocol needs to provide message confidentiality.
- DoS Attack Protection
TBD.
5. IANA Considerations
Section 3.4 defines the following multicast addresses, which have
been assigned by IANA for use by GDNP:
ALL_GDNP_NEIGHBOR multicast address (IPv6): (TBD1)
ALL_GDNP_NEIGHBOR multicast address (IPv4): (TBD2)
Section 3.4 defines the following UDP port, which has been assigned
by IANA for use by GDNP:
GDNP Listen Port: (TBD3)
This document defined a new General Discovery and Negotiation
Protocol. The IANA is requested to create a new GDNP registry. The
IANA is also requested to add two new registry tables to the newly-
created GDNP registry. The two tables are the GDNP Messages table
and GDNP Options table.
Initial values for these registries are given below. Future
assignments are to be made through Standards Action or Specification
Carpenter & Liu Expires July 10, 2015 [Page 34]
Internet-Draft GDN Protocol January 2015
Required [RFC5226]. Assignments for each registry consist of a type
code value, a name and a document where the usage is defined.
GDNP Messages table. The values in this table are 16-bit unsigned
integers. The following initial values are assigned in Section 3.7
in this document:
Type | Name | RFCs
---------+-----------------------------+------------
0 |Reserved | this document
1 |Discovery | this document
2 |Response | this document
3 |Request Message | this document
4 |Negotiation Message | this document
5 |Negotiation-end Message | this document
6 |Confirm-waiting Message | this document
GDNP Options table. The values in this table are 16-bit unsigned
integers. The following initial values are assigned in Section 3.8
and Section 3.10 in this document:
Type | Name | RFCs
---------+-----------------------------+------------
0 |Reserved | this document
1 |Divert Option | this document
2 |Accept Option | this document
3 |Decline Option | this document
4 |Waiting Time Option | this document
5 |Certificate Option | this document
6 |Signature Option | this document
7 |Device IPv4 Address Option | this document
8 |Device IPv6 Address Option | this document
9 |Device FQDN Option | this document
10~63 |Reserved for future GDNP | this document
|General Options |
128~159 |Vendor Specific Options | this document
176~191 |Experimental Options | this document
The IANA is also requested to create two new registry tables in the
GDNP Parameters registry. The two tables are the Hash Algorithm for
GDNP table and the Signature Algorithm for GDNP table.
Initial values for these registries are given below. Future
assignments are to be made through Standards Action or Specification
Required [RFC5226]. Assignments for each registry consist of a name,
a value and a document where the algorithm is defined.
Carpenter & Liu Expires July 10, 2015 [Page 35]
Internet-Draft GDN Protocol January 2015
Hash Algorithm for GDNP. The values in this table are 16-bit
unsigned integers. The following initial values are assigned for
Hash Algorithm for GDNP in this document:
Name | Value | RFCs
---------------------+-----------+------------
Reserved | 0x0000 | this document
SHA-1 | 0x0001 | this document
SHA-256 | 0x0002 | this document
Signature Algorithm for GDNP. The values in this table are 16-bit
unsigned integers. The following initial values are assigned for
Signature Algorithm for GDNP in this document:
Name | Value | RFCs
---------------------+-----------+------------
Reserved | 0x0000 | this document
RSASSA-PKCS1-v1_5 | 0x0001 | this document
6. Acknowledgements
A major contribution to the original version of this document was
made by Sheng Jiang.
Valuable comments were received from Zhenbin Li, Dimitri
Papadimitriou, Michael Richardson, Rene Struik, Dacheng Zhang, and
other participants in the NMRG research group and the ANIMA working
group.
This document was produced using the xml2rfc tool [RFC2629].
7. Change log [RFC Editor: Please remove]
draft-carpenter-anima-discovery-negotiation-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-discovery-negotiation-protocol-00, combination
of draft-jiang-config-negotiation-ps-03 and draft-jiang-config-
negotiation-protocol-02, 2014-10-08.
8. References
Carpenter & Liu Expires July 10, 2015 [Page 36]
Internet-Draft GDN Protocol January 2015
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3174] Eastlake, D. and P. Jones, "US Secure Hash Algorithm 1
(SHA1)", RFC 3174, September 2001.
[RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness
Requirements for Security", BCP 106, RFC 4086, June 2005.
[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, May 2008.
[RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko,
"The Trickle Algorithm", RFC 6206, March 2011.
8.2. Informative References
[I-D.behringer-anima-autonomic-control-plane]
Behringer, M., Bjarnason, S., BL, B., and T. Eckert, "An
Autonomic Control Plane", draft-behringer-anima-autonomic-
control-plane-00 (work in progress), October 2014.
[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.eckert-anima-stable-connectivity]
Eckert, T. and M. Behringer, "Autonomic Network Stable
Connectivity", draft-eckert-anima-stable-connectivity-00
(work in progress), October 2014.
[I-D.ietf-dnssd-requirements]
Lynn, K., Cheshire, S., Blanchet, M., and D. Migault,
"Requirements for Scalable DNS-SD/mDNS Extensions", draft-
ietf-dnssd-requirements-04 (work in progress), October
2014.
[I-D.ietf-homenet-hncp]
Stenberg, M. and S. Barth, "Home Networking Control
Protocol", draft-ietf-homenet-hncp-02 (work in progress),
October 2014.
Carpenter & Liu Expires July 10, 2015 [Page 37]
Internet-Draft GDN Protocol January 2015
[I-D.ietf-netconf-restconf]
Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", draft-ietf-netconf-restconf-03 (work in
progress), October 2014.
[I-D.irtf-nmrg-an-gap-analysis]
Jiang, S., Carpenter, B., and M. Behringer, "Gap Analysis
for Autonomic Networking", draft-irtf-nmrg-an-gap-
analysis-03 (work in progress), December 2014.
[I-D.irtf-nmrg-autonomic-network-definitions]
Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A.,
Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic
Networking - Definitions and Design Goals", draft-irtf-
nmrg-autonomic-network-definitions-05 (work in progress),
December 2014.
[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-04 (work in progress), July 2014.
[I-D.pritikin-anima-bootstrapping-keyinfra]
Pritikin, M., Behringer, M., and S. Bjarnason,
"Bootstrapping Key Infrastructures", draft-pritikin-anima-
bootstrapping-keyinfra-00 (work in progress), November
2014.
[RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, September 1997.
[RFC2608] Guttman, E., Perkins, C., Veizades, J., and M. Day,
"Service Location Protocol, Version 2", RFC 2608, June
1999.
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999.
[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)", RFC
2865, June 2000.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
Carpenter & Liu Expires July 10, 2015 [Page 38]
Internet-Draft GDN Protocol January 2015
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC3416] Presuhn, R., "Version 2 of the Protocol Operations for the
Simple Network Management Protocol (SNMP)", STD 62, RFC
3416, December 2002.
[RFC4270] Hoffman, P. and B. Schneier, "Attacks on Cryptographic
Hashes in Internet Protocols", RFC 4270, November 2005.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, June 2010.
[RFC5971] Schulzrinne, H. and R. Hancock, "GIST: General Internet
Signalling Transport", RFC 5971, October 2010.
[RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J., and A.
Bierman, "Network Configuration Protocol (NETCONF)", RFC
6241, June 2011.
[RFC6733] Fajardo, V., Arkko, J., Loughney, J., and G. Zorn,
"Diameter Base Protocol", RFC 6733, October 2012.
[RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
February 2013.
[RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service
Discovery", RFC 6763, February 2013.
[RFC6887] Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
Selkirk, "Port Control Protocol (PCP)", RFC 6887, April
2013.
Appendix A. Capability Analysis of Current Protocols
This section discusses various existing protocols with properties
related to the above negotiation and synchronisation requirements.
Carpenter & Liu Expires July 10, 2015 [Page 39]
Internet-Draft GDN Protocol January 2015
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.
[I-D.ietf-dnssd-requirements] aims to extend this to larger
autonomous networks. 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.
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.
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 also signalling 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 signalling across many hops rather than at device-to-device
signalling. However, we cannot completely exclude extended RSVP or
Carpenter & Liu Expires July 10, 2015 [Page 40]
Internet-Draft GDN Protocol January 2015
GIST as a synchronization and negotiation protocol. They do not
appear to be directly useable for peer discovery.
We now consider two protocols that are works in progress at the time
of this writing. Firstly, RESTCONF [I-D.ietf-netconf-restconf] 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 are unlikely to include YANG processing
already.
Secondly, we consider HomeNet Control Protocol (HNCP)
[I-D.ietf-homenet-hncp]. This is defined as "a minimalist state
synchronization protocol for Homenet routers."
NOTE: HNCP is under revision at the time of this writing, so the
following comments will soon be out of date.
Specific features are:
o Every participating node has a unique node identifier.
o "HNCP is designed to operate between directly connected neighbors
on a shared link using link-local IPv6 addresses."
o Currency of state is maintained by spontaneous link-local
multicast messages.
o HNCP discovers and tracks link-local neighbours.
o HNCP messages are encoded as a sequence of TLV objects, sent over
UDP.
o Authentication depends on a signature TLV (assuming public keys
are associated with node identifiers).
o The functionality covered initially includes: site border
discovery, prefix assignment, DNS namespace discovery, and routing
protocol selection.
Clearly HNCP does not completely meet the needs of a general
negotiation protocol, especially due to its limitation to link-local
messages and its strict dependency on IPv6, but at the minimum it is
a very interesting test case for this style of interaction between
devices without needing a central authority.
Carpenter & Liu Expires July 10, 2015 [Page 41]
Internet-Draft GDN Protocol January 2015
A proposal has been made for an IP based Generic Control Protocol
(IGCP) [I-D.chaparadza-intarea-igcp]. This is 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
discovery, state synchronization and negotiation in the general case.
Neither is there an obvious combination of protocols that does so.
Therefore, this document proposes the design of a protocol that does
meet those needs. However, this proposal needs to be confronted with
alternatives such as extension and adaptation of GIST or HNCP, or
combination with IGCP.
Authors' Addresses
Brian Carpenter
Department of Computer Science
University of Auckland
PB 92019
Auckland 1142
New Zealand
Email: brian.e.carpenter@gmail.com
Bing Liu
Huawei Technologies Co., Ltd
Q14, Huawei Campus
No.156 Beiqing Road
Hai-Dian District, Beijing 100095
P.R. China
Email: leo.liubing@huawei.com
Carpenter & Liu Expires July 10, 2015 [Page 42]