Dynamic Link Exchange Protocol (DLEP)
draft-ietf-manet-dlep-16
The information below is for an old version of the document.
Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 8175.
|
|
---|---|---|---|
Authors | Stan Ratliff , Bo Berry, Shawn Jury , Darryl Satterwhite , Rick Taylor | ||
Last updated | 2015-10-14 (Latest revision 2015-07-21) | ||
Replaces | draft-sratliff-manet-dlep | ||
RFC stream | Internet Engineering Task Force (IETF) | ||
Formats | |||
Reviews |
TSVART Telechat review
(of
-25)
by Michael Scharf
Ready w/nits
GENART Last Call review
(of
-25)
by Matthew Miller
Almost ready
RTGDIR Early review
(of
-13)
by Lou Berger
Has issues
|
||
Additional resources | Mailing list discussion | ||
Stream | WG state | WG Document | |
Document shepherd | Justin Dean | ||
Shepherd write-up | Show Last changed 2015-06-10 | ||
IESG | IESG state | Became RFC 8175 (Proposed Standard) | |
Consensus boilerplate | Unknown | ||
Telechat date | (None) | ||
Responsible AD | Alvaro Retana | ||
Send notices to | (None) |
draft-ietf-manet-dlep-16
Mobile Ad hoc Networks Working Group S. Ratliff Internet-Draft VT iDirect Intended status: Standards Track B. Berry Expires: January 21, 2016 S. Jury Cisco Systems D. Satterwhite Broadcom R. Taylor Airbus Defence & Space July 20, 2015 Dynamic Link Exchange Protocol (DLEP) draft-ietf-manet-dlep-16 Abstract When routing devices rely on modems to effect communications over wireless links, they need timely and accurate knowledge of the characteristics of the link (speed, state, etc.) in order to make routing decisions. In mobile or other environments where these characteristics change frequently, manual configurations or the inference of state through routing or transport protocols does not allow the router to make the best decisions. A bidirectional, event- driven communication channel between the router and the modem is necessary. 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 January 21, 2016. Ratliff, et al. Expires January 21, 2016 [Page 1] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 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 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 . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Protocol Overview . . . . . . . . . . . . . . . . . . . . 7 1.2. Requirements . . . . . . . . . . . . . . . . . . . . . . 8 2. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 8 3. Core Features and Extensions . . . . . . . . . . . . . . . . 10 3.1. Experiments . . . . . . . . . . . . . . . . . . . . . . . 10 4. Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.1. Mandatory Metrics . . . . . . . . . . . . . . . . . . . . 12 5. DLEP Session Flow . . . . . . . . . . . . . . . . . . . . . . 12 5.1. Peer Discovery State . . . . . . . . . . . . . . . . . . 12 5.2. Session Initialization State . . . . . . . . . . . . . . 13 5.3. In-Session State . . . . . . . . . . . . . . . . . . . . 14 5.4. Session Termination State . . . . . . . . . . . . . . . . 16 6. DLEP Signal and Message Processing . . . . . . . . . . . . . 16 7. DLEP Signal and Message Structure . . . . . . . . . . . . . . 17 7.1. DLEP Signal Header . . . . . . . . . . . . . . . . . . . 18 7.2. DLEP Message Header . . . . . . . . . . . . . . . . . . . 18 7.3. DLEP Generic Data Item . . . . . . . . . . . . . . . . . 19 8. DLEP Signals and Messages . . . . . . . . . . . . . . . . . . 19 8.1. Peer Discovery Signal . . . . . . . . . . . . . . . . . . 20 8.2. Peer Offer Signal . . . . . . . . . . . . . . . . . . . . 21 8.3. Session Initialization Message . . . . . . . . . . . . . 21 8.4. Session Initialization Response Message . . . . . . . . . 22 8.5. Session Update Message . . . . . . . . . . . . . . . . . 24 8.6. Session Update Response Message . . . . . . . . . . . . . 25 8.7. Session Termination Message . . . . . . . . . . . . . . . 25 8.8. Session Termination Response Message . . . . . . . . . . 26 8.9. Destination Up Message . . . . . . . . . . . . . . . . . 26 8.10. Destination Up Response Message . . . . . . . . . . . . . 27 8.11. Destination Down Message . . . . . . . . . . . . . . . . 28 8.12. Destination Down Response Message . . . . . . . . . . . . 28 Ratliff, et al. Expires January 21, 2016 [Page 2] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 8.13. Destination Update Message . . . . . . . . . . . . . . . 29 8.14. Heartbeat Message . . . . . . . . . . . . . . . . . . . . 30 8.15. Link Characteristics Request Message . . . . . . . . . . 30 8.16. Link Characteristics Response Message . . . . . . . . . . 31 9. DLEP Data Items . . . . . . . . . . . . . . . . . . . . . . . 32 9.1. Status . . . . . . . . . . . . . . . . . . . . . . . . . 33 9.2. IPv4 Connection Point . . . . . . . . . . . . . . . . . . 35 9.3. IPv6 Connection Point . . . . . . . . . . . . . . . . . . 36 9.4. Peer Type . . . . . . . . . . . . . . . . . . . . . . . . 37 9.5. Heartbeat Interval . . . . . . . . . . . . . . . . . . . 38 9.6. Extensions Supported . . . . . . . . . . . . . . . . . . 39 9.7. MAC Address . . . . . . . . . . . . . . . . . . . . . . . 39 9.8. IPv4 Address . . . . . . . . . . . . . . . . . . . . . . 40 9.9. IPv6 Address . . . . . . . . . . . . . . . . . . . . . . 41 9.10. IPv4 Attached Subnet . . . . . . . . . . . . . . . . . . 42 9.11. IPv6 Attached Subnet . . . . . . . . . . . . . . . . . . 42 9.12. Maximum Data Rate (Receive) . . . . . . . . . . . . . . . 43 9.13. Maximum Data Rate (Transmit) . . . . . . . . . . . . . . 44 9.14. Current Data Rate (Receive) . . . . . . . . . . . . . . . 44 9.15. Current Data Rate (Transmit) . . . . . . . . . . . . . . 45 9.16. Latency . . . . . . . . . . . . . . . . . . . . . . . . . 46 9.17. Resources (Receive) . . . . . . . . . . . . . . . . . . . 47 9.18. Resources (Transmit) . . . . . . . . . . . . . . . . . . 47 9.19. Relative Link Quality (Receive) . . . . . . . . . . . . . 48 9.20. Relative Link Quality (Transmit) . . . . . . . . . . . . 49 9.21. Link Characteristics Response Timer . . . . . . . . . . . 49 10. Credit-Windowing . . . . . . . . . . . . . . . . . . . . . . 50 10.1. Credit-Windowing Messages . . . . . . . . . . . . . . . 51 10.1.1. Destination Up Message . . . . . . . . . . . . . . . 51 10.1.2. Destination Up Response Message . . . . . . . . . . 51 10.1.3. Destination Update Message . . . . . . . . . . . . . 51 10.2. Credit-Windowing Data Items . . . . . . . . . . . . . . 52 10.2.1. Credit Grant . . . . . . . . . . . . . . . . . . . . 52 10.2.2. Credit Window Status . . . . . . . . . . . . . . . . 53 10.2.3. Credit Request . . . . . . . . . . . . . . . . . . . 54 11. Security Considerations . . . . . . . . . . . . . . . . . . . 55 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 55 12.1. Registrations . . . . . . . . . . . . . . . . . . . . . 55 12.2. Expert Review: Evaluation Guidelines . . . . . . . . . . 56 12.3. Signal/Message Type Registration . . . . . . . . . . . . 56 12.4. DLEP Data Item Registrations . . . . . . . . . . . . . . 56 12.5. DLEP Status Code Registrations . . . . . . . . . . . . . 56 12.6. DLEP Extensions Registrations . . . . . . . . . . . . . 56 12.7. DLEP Well-known Port . . . . . . . . . . . . . . . . . . 57 12.8. DLEP Multicast Address . . . . . . . . . . . . . . . . . 57 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 57 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 57 14.1. Normative References . . . . . . . . . . . . . . . . . . 57 Ratliff, et al. Expires January 21, 2016 [Page 3] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 14.2. Informative References . . . . . . . . . . . . . . . . . 57 Appendix A. Discovery Signal Flows . . . . . . . . . . . . . . . 58 Appendix B. Peer Level Message Flows . . . . . . . . . . . . . . 58 B.1. Session Initialization . . . . . . . . . . . . . . . . . 58 B.2. Session Initialization - Refused . . . . . . . . . . . . 59 B.3. Router Changes IP Addresses . . . . . . . . . . . . . . . 60 B.4. Modem Changes Session-wide Metrics . . . . . . . . . . . 60 B.5. Router Terminates Session . . . . . . . . . . . . . . . . 60 B.6. Modem Terminates Session . . . . . . . . . . . . . . . . 61 B.7. Session Heartbeats . . . . . . . . . . . . . . . . . . . 61 B.8. Router Detects a Heartbeat timeout . . . . . . . . . . . 62 B.9. Modem Detects a Heartbeat timeout . . . . . . . . . . . . 63 Appendix C. Destination Specific Signal Flows . . . . . . . . . 63 C.1. Common Destination Signaling . . . . . . . . . . . . . . 63 C.2. Multicast Destination Signaling . . . . . . . . . . . . . 64 C.3. Link Characteristics Request . . . . . . . . . . . . . . 64 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 65 1. Introduction There exist today a collection of modem devices that control links of variable datarate and quality. Examples of these types of links include line-of-sight (LOS) terrestrial radios, satellite terminals, and broadband modems. Fluctuations in speed and quality of these links can occur due to configuration, or on a moment-to-moment basis, due to physical phenomena like multipath interference, obstructions, rain fade, etc. It is also quite possible that link quality and datarate vary with respect to individual destinations on a link, and with the type of traffic being sent. As an example, consider the case of an 802.11 access point, serving two associated laptop computers. In this environment, the answer to the question "What is the datarate on the 802.11 link?" is "It depends on which associated laptop we're talking about, and on what kind of traffic is being sent." While the first laptop, being physically close to the access point, may have a datarate of 54Mbps for unicast traffic, the other laptop, being relatively far away, or obstructed by some object, can simultaneously have a datarate of only 32Mbps for unicast. However, for multicast traffic sent from the access point, all traffic is sent at the base transmission rate (which is configurable, but depending on the model of the access point, is usually 24Mbps or less). In addition to utilizing variable datarate links, mobile networks are challenged by the notion that link connectivity will come and go over time, without an effect on a router's interface state (Up or Down). Effectively utilizing a relatively short-lived connection is problematic in IP routed networks, as routing protocols tend to rely on interface state and independent timers at OSI Layer 3 to maintain network convergence (e.g., HELLO messages and/or recognition of DEAD Ratliff, et al. Expires January 21, 2016 [Page 4] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 routing adjacencies). These dynamic connections can be better utilized with an event-driven paradigm, where acquisition of a new neighbor (or loss of an existing one) is signaled, as opposed to a paradigm driven by timers and/or interface state. Another complicating factor for mobile networks are the different methods of physically connecting the modem devices to the router. Modems can be deployed as an interface card in a router's chassis, or as a standalone device connected to the router via Ethernet or serial link. In the case of Ethernet attachment, with existing protocols and techniques, routing software cannot be aware of convergence events occurring on the radio link (e.g., acquisition or loss of a potential routing neighbor), nor can the router be aware of the actual capacity of the link. This lack of awareness, along with the variability in datarate, leads to a situation where finding the (current) best route through the network to a given destination is difficult to establish and properly maintain. This is especially true of demand-based access schemes such as Demand Assigned Multiple Access (DAMA) implementations used on some satellite systems. With a DAMA-based system, additional datarate may be available, but will not be used unless the network devices emit traffic at a rate higher than the currently established rate. Increasing the traffic rate does not guarantee additional datarate will be allocated; rather, it may result in data loss and additional retransmissions on the link. Addressing the challenges listed above, the co-authors have developed the Dynamic Link Exchange Protocol, or DLEP. The DLEP protocol runs between a router and its attached modem devices, allowing the modem to communicate link characteristics as they change, and convergence events (acquisition and loss of potential routing destinations). The following diagrams are used to illustrate the scope of DLEP packets. |-------Local Node-------| |-------Remote Node------| | | | | +--------+ +-------+ +-------+ +--------+ | Router |=======| Modem |{~~~~~~~~}| Modem |=======| Router | | | | Device| | Device| | | +--------+ +-------+ +-------+ +--------+ | | | Link | | | |-DLEP--| | Protocol | |-DLEP--| | | | (e.g. | | | | | | 802.11) | | | Figure 1: DLEP Network In Figure 1, when the local modem detects the presence of a remote node, it (the local modem) sends a message to its router via the DLEP protocol. The message consists of an indication of what change has Ratliff, et al. Expires January 21, 2016 [Page 5] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 occurred on the link (e.g., presence of a remote node detected), along with a collection of DLEP-defined Data Items that further describe the change. Upon receipt of the message, the local router may take whatever action it deems appropriate, such as initiating discovery protocols, and/or issuing HELLO messages to converge the network. On a continuing, as-needed basis, the modem devices use DLEP to report any characteristics of the link (datarate, latency, etc.) that have changed. DLEP is independent of the link type and topology supported by the modem. Note that the DLEP protocol is specified to run only on the local link between router and modem. Some over the air signaling may be necessary between the local and remote modem in order to provide some parameters in DLEP messages between the local modem and local router, but DLEP does not specify how such over the air signaling is carried out. Over the air signaling is purely a matter for the modem implementer. Figure 2 shows how DLEP can support a configuration where routers are connected with different link types. In this example, Modem A implements a point-to-point link, and Modem B is connected via a shared medium. In both cases, the DLEP protocol is used to report the characteristics of the link (datarate, latency, etc.) to routers. The modem is also able to use the DLEP session to notify the router when the remote node is lost, shortening the time required to re- converge the network. Ratliff, et al. Expires January 21, 2016 [Page 6] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 +--------+ +--------+ +----+ Modem A| | Modem A+---+ | | Device | <===== // ======> | Device | | | +--------+ P-2-P Link +--------+ | +---+----+ +---+----+ | Router | | Router | | | | | +---+----+ +---+----+ | +--------+ +--------+ | +-----+ Modem B| | Modem B| | | Device | o o o o o o o o | Device +--+ +--------+ o Shared o +--------+ o Medium o o o o o o o o +--------+ | Modem B| | Device | +---+----+ | | +---+----+ | Router | | | +--------+ Figure 2: DLEP Network with Multiple Modem Devices 1.1. Protocol Overview As mentioned earlier, DLEP defines a set of messages used by modems and their attached routers. The messages are used to communicate events that occur on the physical link(s) managed by the modem: for example, a remote node entering or leaving the network, or that the link has changed. Associated with these messages are a set of data items - information that describes the remote node (e.g., address information), and/or the characteristics of the link to the remote node. The protocol is defined as a collection of type-length-value (TLV) based formats, specifying the messages that are exchanged between a router and a modem, and the data items associated with the message. This document specifies transport of DLEP messages and data items via the TCP transport, with a UDP-based discovery mechanism. Other transports for the protocol are possible, but are outside the scope of this document. Ratliff, et al. Expires January 21, 2016 [Page 7] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 DLEP uses a session-oriented paradigm between the modem device and its associated router. If multiple modem devices are attached to a router (as in Figure 2), or the modem supports multiple connections (via multiple logical or physical interfaces), then separate DLEP sessions exist for each modem or connection. This router/modem session provides a carrier for information exchange concerning 'destinations' that are available via the modem device. A 'destination' can be either physical (as in the case of a specific far-end router), or a logical destination (as in a Multicast group). As such, all of the destination-level exchanges in DLEP can be envisioned as building an information base concerning the remote nodes, and the link characteristics to those nodes. Multicast traffic destined for the variable-quality network (the network accessed via the DLEP modem) is handled in IP networks by deriving a Layer 2 MAC address based on the Layer 3 address. Leveraging on this scheme, multicast traffic is supported in DLEP simply by treating the derived MAC address as any other 'destination' (albeit a logical one) in the network. To support these logical destinations, one of the DLEP participants (typically, the router) informs the other as to the existence of the logical destination. The modem, once it is aware of the existence of this logical destination, reports link characteristics just as it would for any other destination in the network. The specific algorithms a modem would use to derive metrics on multicast (or logical) destinations are outside the scope of this specification, and is left to specific implementations to decide. 1.2. Requirements 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 BCP 14, RFC 2119 [RFC2119]. 2. Assumptions Routers and modems that exist as part of the same node (e.g., that are locally connected) can use a discovery technique to locate each other, thus avoiding a priori configuration. The router is responsible for initializing the discovery process, using the Peer Discovery signal (Section 8.1). DLEP uses a session-oriented paradigm. A router and modem form a session by completing the discovery and initialization process. This router-modem session persists unless or until it either (1) times out, based on the timeout values supplied, or (2) is explicitly torn down by one of the participants. Note that while use of timers in Ratliff, et al. Expires January 21, 2016 [Page 8] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 DLEP is optional, it is strongly RECOMMENDED that implementations choose to run with timers enabled. DLEP assumes that the MAC address for delivering data traffic is the MAC specified in the Destination Up message (Section 8.9). No manipulation or substitution is performed; the MAC address supplied in Destination Up is used as the OSI Layer 2 Destination MAC address. DLEP also assumes that MAC addresses MUST be unique within the context of a router-modem session. Additionally, DLEP can support MAC addresses in either EUI-48 or EUI-64 format, with the restriction that ALL MAC addresses for a given DLEP session MUST be in the same format, and MUST be consistent with the MAC address format of the connected modem (e.g., if the modem is connected to the router with an EUI-48 MAC, all destination addresses via that modem MUST be expressed in EUI-48 format). DLEP uses UDP multicast for single-hop discovery signalling, and TCP for transport of the control messages. Therefore, DLEP assumes that the modem and router have topologically consistent IP addresses assigned. It is RECOMMENDED that DLEP implementations utilize IPv6 link-local addresses to reduce the administrative burden of address assignment. Destinations can be identified by either the router or the modem, and represent a specific destination (e.g., an address) that exists on the link(s) managed by the modem. A destination MUST contain a MAC address, it MAY optionally include a Layer 3 address (or addresses). Note that since a destination is a MAC address, the MAC could reference a logical destination, as in a derived multicast MAC address, as well as a physical device. As destinations are discovered, DLEP routers and modems build an information base on destinations accessible via the modem. The DLEP messages concerning destinations thus become the way for routers and modems to maintain, and notify each other about, an information base representing the physical and logical (e.g., multicast) destinations accessible via the modem device. The information base would contain addressing information (i.e. MAC address, and OPTIONALLY, Layer 3 addresses), link characteristics (metrics), and OPTIONALLY, flow control information (credits). DLEP assumes that any message not understood by a receiver MUST result in an error indication being sent to the originator, and also MUST result in termination of the session between the DLEP peers. Any DLEP data item not understood by a receiver MUST also result in termination of the session. Ratliff, et al. Expires January 21, 2016 [Page 9] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 DLEP assumes that security on the session (e.g., authentication of session partners, encryption of traffic, or both) is dealt with by the underlying transport mechanism (e.g., by using a transport such as TLS [RFC5246]). This document specifies an implementation of the DLEP messages running over the TCP transport. It is assumed that DLEP running over other transport mechanisms would be documented separately. 3. Core Features and Extensions DLEP has a core set of signals, messages and data items that MUST be parsed without error by an implementation in order to guarantee interoperability and therefore make the implementation DLEP compliant. This document defines this set of signals, messages and data items, listing them as 'core'. It should be noted that some core signals, messages and data items might not be used during the lifetime of a single DLEP session, but a compliant implementation MUST support them. While this document represents the best efforts of the working group to be functionally complete, it is recognized that extensions to DLEP will in all likelihood be necessary as more link types are used. If interoperable protocol extensions are required, they MUST be standardized either as an update to this document, or as an additional stand-alone specification. The requests for IANA- controlled registries in this document contain sufficient Reserved space, in terms of DLEP signals, messages, data items and status codes, to accommodate future extensions to the protocol and the data transferred. All extensions are considered OPTIONAL. Extensions may be negotiated on a per-session basis during session initialization via the Extensions Supported mechanism. Only the DLEP functionality listed as 'core' is required by an implementation in order to be DLEP compliant. This specification defines one extension, Credit Windowing, that devices MAY choose to implement. 3.1. Experiments This document requests Private Use numbering space in the DLEP signal/message, data item and status code registries for experimental items. The intent is to allow for experimentation with new signals, messages, data items, and/or status codes, while still retaining the documented DLEP behavior. Ratliff, et al. Expires January 21, 2016 [Page 10] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 Use of the experimental signals, messages, data items, status codes, or behaviors MUST be announced as Extensions, using extension identifiers from the Private Use space in the Extensions Supported registry (Table 4), during session initialization with a value agreed upon (a priori) between the participating peers. Multiple experiments MAY be announced in the Session Initialization messages. However, use of multiple experiments in a single session could lead to interoperability issues or unexpected results (e.g., clashes of experimental signals, messages, data items and/or status code types), and is therefore discouraged. It is left to implementations to determine the correct processing path (e.g., a decision on whether to terminate the session, or to establish a precedence of the conflicting definitions) if such conflicts arise. 4. Metrics DLEP includes the ability for the router and modem to communicate metrics that reflect the characteristics (e.g., datarate, latency) of the variable-quality link in use. DLEP does not specify how a given metric value is to be calculated, rather, the protocol assumes that metrics have been calculated with a 'best effort', incorporating all pertinent data that is available to the modem device. DLEP allows for metrics to be sent within two contexts - metrics for a specific destination within the network (e.g., a specific router), and per-session (those that apply to all destinations accessed via the modem). Most metrics can be further subdivided into transmit and receive metrics. In cases where metrics are provided at session level, the receiver MUST propagate the metrics to all entries in its information base for destinations that are accessed via the originator. DLEP modem implementations MUST announce all metric items that will be reported during the session, and provide default values for those metrics, in the Session Initialization Response message (Section 8.4). In order to use a metric type that was not included in the Session Initialization Response message, modem implementations MUST terminate the session with the router (via the Session Terminate message (Section 8.7)), and establish a new session. It is left to implementations to choose sensible default values based on their specific characteristics. Modems having static (non- changing) link metric characteristics MAY report metrics only once for a given destination (or once on a modem-wide basis, if all connections via the modem are of this static nature). Ratliff, et al. Expires January 21, 2016 [Page 11] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 A DLEP participant MAY send metrics both in a session context (via the Session Update message) and a specific destination context (via Destination Update) at any time. The heuristics for applying received metrics is left to implementations. 4.1. Mandatory Metrics As mentioned above, DLEP modem implementations MUST announce all supported metric items during the Session Initialization state. However, a modem MUST include the following list of metrics in the Session Initialization Response message (Section 8.4): o Maximum Data Rate (Receive) (Section 9.12) o Maximum Data Rate (Transmit) (Section 9.13) o Current Data Rate (Receive) (Section 9.14) o Current Data Rate (Transmit) (Section 9.15) o Latency (Section 9.16) 5. DLEP Session Flow All DLEP peers transition through four (4) distinct states during the lifetime of a DLEP session: o Peer Discovery o Session Initialization o In-Session o Session Termination The Peer Discovery state is OPTIONAL to implement for routers. If it is used, this state is the initial state. If it is not used, then one or more preconfigured address/port combinations SHOULD be provided to the router, and the device starts in the Session Initialization state. Modems MUST support the Peer Discovery state. 5.1. Peer Discovery State In the Peer Discovery state, routers send UDP packets containing a Peer Discovery signal (Section 8.1) to the DLEP well-known multicast address (Section 12.8) and port number (Section 12.7) then await a Ratliff, et al. Expires January 21, 2016 [Page 12] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 unicast UDP packet containing a Peer Offer signal (Section 8.2) from a modem. While in the Peer Discovery state, Peer Discovery signals MUST be sent repeatedly by a router, at regular intervals; every three (3) seconds is RECOMMENDED. In the Peer Discovery state, the modem waits for incoming Peer Discovery signals on the DLEP well-known multicast address and port. On receipt of a valid signal, it MUST unicast a Peer Offer signal to the source address of the received UDP packet. Peer Offer signals MAY contain the unicast address and port for TCP-based communication with a modem, via the IPv4 Connection Point data item (Section 9.2) or the IPv6 Connection Point data item (Section 9.3), on which it is prepared to accept an incoming TCP connection. The modem then begins listening for incoming TCP connections, and, having accepted one, enters the Session Initialization state. Anything other than Peer Discovery signals received on the UDP socket MUST be silently dropped. Modems SHOULD be prepared to accept a TCP connection from a router that is not using the Discovery mechanism, i.e. a connection attempt that occurs without a preceeding Peer Discovery signal. The modem MUST accept a TCP connection on only one (1) address/port combination per session. Routers MUST use one or more of the modem address/port combinations from the Peer Offer signal or from a priori configuration to establish a new TCP connection to the modem. If more than one modem address/port combinations is available, router implementations MAY use their own heuristics to determine the order in which they are tried. If a TCP connection cannot be achieved using any of the address/port combinations and the Discovery mechanism is in use, then the router SHOULD resume issuing Peer Discovery signals. If no IP Connection Point data items are included in the Peer Offer signal, the router MUST use the origin address of the signal as the IP address, and the DLEP well-known port number. Once a TCP connection has been established with the modem, the router begins a new session and enters the Session Initialization state. It is up to the router implementation if Peer Discovery signals continue to be sent after the device has transitioned to the Session Initialization state. 5.2. Session Initialization State On entering the Session Initialization state, the router MUST send a Session Initialization message (Section 8.3) to the modem. The router MUST then wait for receipt of a Session Initialization Response message (Section 8.4) from the modem. Receipt of the Ratliff, et al. Expires January 21, 2016 [Page 13] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 Session Initialization Response message containing a Status data item (Section 9.1) with value 'Success', see Table 3, indicates that the modem has received and processed the Session Initialization message, and the router MUST transition to the In-Session state. On entering the Session Initialization state, the modem MUST wait for receipt of a Session Initialization message from the router. Upon receipt and successful parsing of a Session Initialization message, the modem MUST send a Session Initialization Response message, and the session MUST transition to the In-Session state. As mentioned before, DLEP provides an extension negotiation capability to be used in the Session Initialization state. Extensions supported by an implementation MUST be declared to potential DLEP peers using the Extensions Supported data item (Section 9.6). Once both peers have exchanged initialization messages, an implementation MUST NOT emit any message, signal, data item or status code associated with an extension that was not specified in the received initialization message from its peer. If the router receives any message other than a valid Session Initialization Response, it MUST send a Session Termination message (Section 8.7) with a relevant status code, e.g. 'Unexpected Message', see Table 3, and transition to the Session Termination state. If the modem receives any message other than Session Initialization, or it fails to parse the received message, it MUST NOT send any message, and MUST terminate the TCP connection, then restart at the Peer Discovery state. As mentioned before, the Session Initialization Response message MUST contain metric data items for ALL metrics that will be used during the session. If an additional metric is to be introduced after the session has started, the session between router and modem MUST be terminated and restarted, and the new metric described in the next Session Initialization Response message. 5.3. In-Session State In the In-Session state, messages can flow in both directions between peers, indicating changes to the session state, the arrival or departure of reachable destinations, or changes of the state of the links to the destinations. Ratliff, et al. Expires January 21, 2016 [Page 14] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 In order to maintain the In-Session state, periodic Heartbeat messages (Section 8.14) MAY be exchanged between router and modem. These messages are intended to keep the session alive, and to verify bidirectional connectivity between the two participants. Each DLEP peer is responsible for the creation of heartbeat messages. Receipt of any valid DLEP message MUST reset the heartbeat interval timer (i.e., valid DLEP messages take the place of, and obviate the need for, Heartbeat messages). DLEP provides a Session Update message (Section 8.5), intended to communicate some change in status (e.g., a change of layer 3 address parameters, or a modem-wide link change). In addition to the session messages, the participants will transmit messages concerning destinations in the network. These messages trigger creation/maintenance/deletion of destinations in the information base of the recipient. For example, a modem will inform its attached router of the presence of a new destination via the Destination Up message (Section 8.9). Receipt of a Destination Up causes the router to allocate the necessary resources, creating an entry in the information base with the specifics (i.e. MAC Address, Latency, Data Rate, etc.) of the destination. The loss of a destination is communicated via the Destination Down message (Section 8.11), and changes in status to the destination (e.g., varying link quality, or addressing changes) are communicated via the Destination Update message (Section 8.13). The information on a given destination will persist in the router's information base until (1) a Destination Down message is received, indicating that the modem has lost contact with the remote node, or (2) the router/modem transitions to the Session Termination state. In addition to receiving metrics about the link, DLEP provides a message allowing a router to request a different datarate, or latency, from the modem. This message is referred to as the Link Characteristics Request message (Section 8.15), and gives the router the ability to deal with requisite increases (or decreases) of allocated datarate/latency in demand-based schemes in a more deterministic manner. The In-Session state is maintained until one of the following conditions occur: o The implementation terminates the session by sending a Session Termination message (Section 8.7)), or o The DLEP peer terminates the session, indicated by receiving a Session termination message. Ratliff, et al. Expires January 21, 2016 [Page 15] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 The implementation MUST then transition to the Session Termination state. 5.4. Session Termination State When a DLEP implementation enters the Session Termination state after sending a Session Termination message (Section 8.7) as the result of an invalid message or error, it MUST wait for a Session Termination Response message (Section 8.8) from its peer. If Heartbeat messages (Section 8.14) are in use, senders SHOULD allow four (4) heartbeat intervals to expire before assuming that the peer is unresponsive, and continuing with session termination. If Heartbeat messages are not in use, then if is RECOMMENDED that an interval of eight (8) seconds be used. When a DLEP implementation enters the Session Termination state having received a Session Termination message from its peer, it MUST immediately send a Session Termination Response. The sender and receiver of a Session Termination message MUST release all resources allocated for the session, and MUST eliminate all destinations in the information base accessible via the peer represented by the session. No Destination Down messages (Section 8.11) are sent. Any messages received after either sending or receiving a Session Termination message MUST be silently ignored. Once Session Termination messages have been exchanged, or timed out, the device MUST terminate the TCP connection to the peer, and return to the relevant initial state. 6. DLEP Signal and Message Processing Most messages in DLEP are members of a request/response pair, e.g. Destination Up message (Section 8.9), and Destination Up Response message (Section 8.10). These pairs of messages define an implicit transaction model for both session messages and destination messages. As mentioned before, session message pairs control the flow of the session through the various states, e.g. an implementation MUST NOT leave the Session Initialization state until a Session Initialization message (Section 8.3) and Session Initialization Response message (Section 8.4) have been exchanged. Destination message pairs describe the arrival and departure of logical destinations, and control the flow of information about the destinations in the several ways. Ratliff, et al. Expires January 21, 2016 [Page 16] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 Prior to the exchange of a pair of Destination Up and Destination Up Response messages, no messages concerning the logical destination identified by the MAC Address data item (Section 9.7) may be sent. An implementation receiving a message with such an unannounced destination MUST terminate the session by issuing a Session Termination message (Section 8.7) with a status code of 'Invalid Destination', see Table 3, and transition to the Session Termination state. The receiver of a Destination Up message MAY decline further messages concerning a given destination by sending a Destination Up Response with a status code of 'Not Interested', see Table 3. Receivers of such responses MUST NOT send further messages concerning that destination to the peer. After exchanging a pair of Destination Down (Section 8.11) and Destination Down Response (Section 8.12) messages, no messages concerning the logical destination identified by the MAC Address data item may be a sent without a previously sending a new Destination Up message. An implementation receiving a message about a down destination MUST terminate the session by issuing a Session Termination message with a status code of 'Invalid Destination' and transition to the Session Termination state. 7. DLEP Signal and Message Structure DLEP defines two protocol units used in two different ways: Signals and Messages. Signals are only used in the Discovery mechanism and are carried in UDP datagrams. Messages are used bi-directionally over a TCP connection between two peers, in the Session Initialization, In-Session and Session Termination states. Both signals and messages consist of a header followed by an unordered list of data items. Headers consist of Type and Length information, while data items are encoded as TLV (Type-Length-Value) structures. In this document, the data items following a signal or message header are described as being 'contained in' the signal or message. There is no restriction on the order of data items following a header, and the multiplicity of duplicate data items is defined by the definition of the signal or message declared by the type in the header. All integers in header fields and values MUST be in network byte- order. Ratliff, et al. Expires January 21, 2016 [Page 17] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 7.1. DLEP Signal Header The DLEP signal header contains the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 'D' | 'L' | 'E' | 'P' | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Signal Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: DLEP Signal Header "DLEP": Every signal MUST start with the characters: U+44, U+4C, U+45, U+50. Signal Type: An 16-bit unsigned integer containing one of the DLEP Signal/Message Type values defined in this document. Length: The length in octets, expressed as a 16-bit unsigned integer, of all of the DLEP data items associated with this signal. This length SHALL NOT include the length of the header itself. The DLEP signal header is immediately followed by one or more DLEP data items, encoded in TLVs, as defined in this document. If an unrecognized, or unexpected signal is received, or a received signal contains unrecognized, invalid, or disallowed duplicate data items, the receiving peer MUST ignore the signal. 7.2. DLEP Message Header The DLEP message header contains the following fields: 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 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: DLEP Message Header Message Type: An 16-bit unsigned integer containing one of the DLEP Signal/Message Type values defined in this document. Ratliff, et al. Expires January 21, 2016 [Page 18] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 Length: The length in octets, expressed as a 16-bit unsigned integer, of all of the DLEP data items associated with this message. This length SHALL NOT include the length of the header itself. The DLEP message header is immediately followed by one or more DLEP data items, encoded in TLVs, as defined in this document. If an unrecognized, or unexpected message is received, or a received message contains unrecognized, invalid, or disallowed duplicate data items, the receiving peer MUST issue a Session Termination message (Section 8.7) with a Status data item (Section 9.1) containing the most relevant status code, and transition to the Session Termination state. 7.3. DLEP Generic Data Item All DLEP data items contain the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value... : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: DLEP Generic Data Item Data Item Type: An 16-bit unsigned integer field specifying the type of data item being sent. Length: The length in octets, expressed as an 16-bit unsigned integer, of the value field of the data item. This length SHALL NOT include the length of the header itself. Value: A field of <Length> octets, which contains data specific to a particular data item. 8. DLEP Signals and Messages As mentioned above, all DLEP signals begin with the DLEP signal header, and all DLEP messages begin with the DLEP message header. Therefore, in the following descriptions of specific signals and messages, this header is assumed, and will not be replicated. Ratliff, et al. Expires January 21, 2016 [Page 19] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 Following is the set of core signals and messages that MUST be recognized by a DLEP compliant implementation. As mentioned before, not all messages may be used during a session, but an implementation MUST correctly process these messages when received. The core DLEP signals and messages are: +-------------+-----------------------------------------------------+ | Type Code | Description | +-------------+-----------------------------------------------------+ | 0 | Reserved | | 1 | Peer Discovery signal (Section 8.1) | | 2 | Peer Offer signal (Section 8.2) | | 3 | Session Initialization message (Section 8.3) | | 4 | Session Initialization Response message (Section | | | 8.4) | | 5 | Session Update message (Section 8.5) | | 6 | Session Update Response message (Section 8.6) | | 7 | Session Termination message (Section 8.7) | | 8 | Session Termination Response message (Section 8.8) | | 9 | Destination Up message (Section 8.9) | | 10 | Destination Up Response message (Section 8.10) | | 11 | Destination Down message (Section 8.11) | | 12 | Destination Down Response message (Section 8.12) | | 13 | Destination Update message (Section 8.13) | | 14 | Heartbeat message (Section 8.14) | | 15 | Link Characteristics Request message (Section 8.15) | | 16 | Link Characteristics Response message (Section | | | 8.16) | | 17-65519 | Reserved for future extensions | | 65520-65534 | Private Use. Available for experiments | | 65535 | Reserved | +-------------+-----------------------------------------------------+ Table 1: DLEP Signal/Message types 8.1. Peer Discovery Signal A Peer Discovery signal SHOULD be sent by a router to discover DLEP modems in the network. The Peer Offer signal (Section 8.2) is required to complete the discovery process. Implementations MAY implement their own retry heuristics in cases where it is determined the Peer Discovery signal has timed out. To construct a Peer Discovery signal, the Signal Type value in the signal header is set to 1, from Table 1. The Peer Discovery signal MAY contain the following data item: Ratliff, et al. Expires January 21, 2016 [Page 20] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 o Peer Type (Section 9.4) 8.2. Peer Offer Signal A Peer Offer signal MUST be sent by a DLEP modem in response to a valid Peer Discovery signal (Section 8.1). The Peer Offer signal MUST be sent to the unicast address of the originator of the Peer Discovery signal. To construct a Peer Offer signal, the Signal Type value in the signal header is set to 2, from Table 1. The Peer Offer signal MAY contain the following data item: o Peer Type (Section 9.4) The Peer Offer signal MAY contain one or more of any of the following data items, with different values: o IPv4 Connection Point (Section 9.2) o IPv6 Connection Point (Section 9.3) The IP Connection Point data items indicate the unicast address the receiver of Peer Offer MUST use when connecting the DLEP TCP session. If multiple IP Connection Point data items are present in the Peer Offer signal, implementations MAY use their own heuristics to select the address to connect to. If no IP Connection Point data items are included in the Peer Offer signal, the receiver MUST use the origin address of the signal as the IP address, and the DLEP well-known port number (Section 12.7) to establish the TCP connection. 8.3. Session Initialization Message A Session Initialization message MUST be sent by a router as the first message of the DLEP TCP session. It is sent by the router after a TCP connect to an address/port combination that was obtained either via receipt of a Peer Offer, or from a priori configuration. If any optional extensions are supported by the implementation, they MUST be enumerated in the Extensions Supported data item. If an Extensions Supported data item does not exist in a Session Initialization message, the receiver of the message MUST conclude that there is no support for extensions in the sender. Implementations supporting the Heartbeat Interval (Section 9.5) should understand that heartbeats are not fully established until Ratliff, et al. Expires January 21, 2016 [Page 21] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 receipt of Session Initialization Response message (Section 8.4), and should therefore implement their own timeout and retry heuristics for this message. To construct a Session Initialization message, the Message Type value in the message header is set to 3, from Table 1. The Session Initialization message MUST contain one of each of the following data items: o Heartbeat Interval (Section 9.5) The Session Initialization message MAY contain one of each of the following data items: o Peer Type (Section 9.4) o Extensions Supported (Section 9.6) A Session Initialization message MUST be acknowledged by the receiver issuing a Session Initialization Response message (Section 8.4). 8.4. Session Initialization Response Message A Session Initialization Response message MUST be sent in response to a received Session Initialization message (Section 8.3). The Session Initialization Response message completes the DLEP session establishment; the sender of the message should transition to the In- Session state when the message is sent, and the receiver should transition to the In-Session state upon receipt (and successful parsing) of an acceptable Session Initialization Response message. All supported metric data items MUST be included in the Session Initialization Response message, with default values to be used on a 'modem-wide' basis. This can be viewed as the modem 'declaring' all supported metrics at DLEP session initialization. Receipt of any DLEP message containing a metric data item not included in the Session Initialization Response message MUST be treated as an error, resulting in the termination of the DLEP session between router and modem. If any optional extensions are supported by the modem, they MUST be enumerated in the Extensions Supported data item. If an Extensions Supported data item does not exist in a Session Initialization Response message, the receiver of the message MUST conclude that there is no support for extensions in the sender. Ratliff, et al. Expires January 21, 2016 [Page 22] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 After the Session Initialization/Session Initialization Response messages have been successfully exchanged, implementations MUST only use extensions that are supported by BOTH peers. To construct a Session Initialization Response message, the Message Type value in the message header is set to 4, from Table 1. The Session Initialization Response message MUST contain one of each of the following data items: o Heartbeat Interval (Section 9.5) o Maximum Data Rate (Receive) (Section 9.12) o Maximum Data Rate (Transmit) (Section 9.13) o Current Data Rate (Receive) (Section 9.14) o Current Data Rate (Transmit) (Section 9.15) o Latency (Section 9.16) The Session Initialization Response message MUST contain one of each of the following data items, if the data item will be used during the lifetime of the session: o Resources (Receive) (Section 9.17) o Resources (Transmit) (Section 9.18) o Relative Link Quality (Receive) (Section 9.19) o Relative Link Quality (Transmit) (Section 9.20) The Session Initialization Response message MAY contain one of each of the following data items: o Status (Section 9.1) o Peer Type (Section 9.4) o Extensions Supported (Section 9.6) A receiver of a Session Initialization Response message without a Status data item MUST behave as if a Status data item with code 'Success' had been received. Ratliff, et al. Expires January 21, 2016 [Page 23] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 8.5. Session Update Message A Session Update message MAY be sent by a DLEP peer to indicate local Layer 3 address changes, or metric changes on a modem-wide basis. For example, addition of an IPv4 address to the router MAY prompt a Session Update message to its attached DLEP modems. Also, for example, a modem that changes its Maximum Data Rate (Receive) for all destinations MAY reflect that change via a Session Update message to its attached router(s). Concerning Layer 3 addresses, if the modem is capable of understanding and forwarding this information (via proprietary mechanisms), the address update would prompt any remote DLEP modems (DLEP-enabled modems in a remote node) to issue a Destination Update message (Section 8.13) to their local routers with the new (or deleted) addresses. Modems that do not track Layer 3 addresses SHOULD silently parse and ignore Layer 3 data items. The Session Update message MUST be acknowledged with a Session Update Response message (Section 8.6). If metrics are supplied with the Session Update message (e.g., Maximum Data Rate), these metrics are considered to be modem-wide, and therefore MUST be applied to all destinations in the information base associated with the router/modem session. Supporting implementations are free to employ heuristics to retransmit Session Update messages. The sending of Session Update messages for Layer 3 address changes SHOULD cease when either participant (router or modem) determines that the other implementation does not support Layer 3 address tracking. To construct a Session Update message, the Message Type value in the message header is set to 5, from Table 1. The Session Update message MAY contain one of each of the following data items: o Maximum Data Rate (Receive) (Section 9.12) o Maximum Data Rate (Transmit) (Section 9.13) o Current Data Rate (Receive) (Section 9.14) o Current Data Rate (Transmit) (Section 9.15) o Latency (Section 9.16) o Resources (Receive) (Section 9.17) Ratliff, et al. Expires January 21, 2016 [Page 24] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 o Resources (Transmit) (Section 9.18) o Relative Link Quality (Receive) (Section 9.19) o Relative Link Quality (Transmit) (Section 9.20) The Session Update message MAY contain one or more of the following data items, with different values: o IPv4 Address (Section 9.8) o IPv6 Address (Section 9.9) A Session Update message MUST be acknowledged by the receiver issuing a Session Update Response message (Section 8.6). 8.6. Session Update Response Message A Session Update Response message MUST be sent by implementations to indicate whether a Session Update message (Section 8.5) was successfully received. To construct a Session Update Response message, the Message Type value in the message header is set to 6, from Table 1. The Session Update Response message MAY contain one of each of the following data items: o Status (Section 9.1) A receiver of a Session Update Response message without a Status data item MUST behave as if a Status data item with code 'Success' had been received. 8.7. Session Termination Message A Session Termination message MUST be sent by a DLEP participant when the router/modem session needs to be terminated. To construct a Session Termination message, the Message Type value in the message header is set to 7, from Table 1. The Session Termination message MAY contain one of each of the following data items: o Status (Section 9.1) Ratliff, et al. Expires January 21, 2016 [Page 25] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 A receiver of a Session Termination message without a Status data item MUST behave as if a Status of 'Unknown reason for Session Termination' has been received. A Session Termination message MUST be acknowledged by the receiver issuing a Session Termination Response message (Section 8.8). 8.8. Session Termination Response Message A Session Termination Response message MUST be sent by a DLEP peer in response to a received Session Termination message (Section 8.7). Receipt of a Session Termination Response message completes the teardown of the router/modem session. To construct a Session Termination Response message, the Message Type value in the message header is set to 8, from Table 1. The Session Termination Response message MAY contain one of each of the following data items: o Status (Section 9.1) A receiver of a Session Termination Response message without a Status data item MUST behave as if a Status data item with status code 'Success', implying graceful termination, had been received. 8.9. Destination Up Message A Destination Up message can be sent either by the modem, to indicate that a new remote node has been detected, or by the router, to indicate the presence of a new logical destination (e.g., a Multicast group) in the network. A Destination Up message MUST be acknowledged by the receiver issuing a Destination Up Response message (Section 8.10). The sender of the Destination Up message is free to define its retry heuristics in event of a timeout. When a Destination Up message is received and successfully processed, the receiver should add knowledge of the new destination to its information base, indicating that the destination is accessible via the modem/router pair. To construct a Destination Up message, the Message Type value in the message header is set to 9, from Table 1. The Destination Up message MUST contain one of each of the following data items: Ratliff, et al. Expires January 21, 2016 [Page 26] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 o MAC Address (Section 9.7) The Destination Up message MAY contain one of each of the following data items: o Maximum Data Rate (Receive) (Section 9.12) o Maximum Data Rate (Transmit) (Section 9.13) o Current Data Rate (Receive) (Section 9.14) o Current Data Rate (Transmit) (Section 9.15) o Latency (Section 9.16) o Resources (Receive) (Section 9.17) o Resources (Transmit) (Section 9.18) o Relative Link Quality (Receive) (Section 9.19) o Relative Link Quality (Transmit) (Section 9.20) The Destination Up message MAY contain one or more of the following data items, with different values: o IPv4 Address (Section 9.8) o IPv6 Address (Section 9.9) o IPv4 Attached Subnet (Section 9.10) o IPv6 Attached Subnet (Section 9.11) If the sender has IPv4 and/or IPv6 address information for a destination it SHOULD include the relevant data items in the Destination Up message, reducing the need for the receiver to probe for any address. 8.10. Destination Up Response Message A DLEP participant MUST send a Destination Up Response message to indicate whether a Destination Up message (Section 8.9) was successfully processed. To construct a Destination Up Response message, the Message Type value in the message header is set to 10, from Table 1. Ratliff, et al. Expires January 21, 2016 [Page 27] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 The Destination Up Response message MUST contain one of each of the following data items: o MAC Address (Section 9.7) The Destination Up Response message MAY contain one of each of the following data items: o Status (Section 9.1) A receiver of a Destination Up Response message without a Status data item MUST behave as if a Status data item with status code 'Success' had been received. 8.11. Destination Down Message A DLEP peer MUST send a Destination Down message to report when a destination (a remote node or a multicast group) is no longer reachable. A Destination Down Response message (Section 8.12) MUST be sent by the recipient of a Destination Down message to confirm that the relevant data has been removed from the information base. The sender of the Destination Down message is free to define its retry heuristics in event of a timeout. To construct a Destination Down message, the Message Type value in the message header is set to 11, from Table 1. The Destination Down message MUST contain one of each of the following data items: o MAC Address (Section 9.7) 8.12. Destination Down Response Message A DLEP participant MUST send a Destination Down Response message to indicate whether a received Destination Down message (Section 8.11) was successfully processed. If successfully processed, the sender of the Response MUST have removed all entries in the information base that pertain to the referenced destination. To construct a Destination Down Response message, the Message Type value in the message header is set to 12, from Table 1. The Destination Down Response message MUST contain one of each of the following data items: o MAC Address (Section 9.7) Ratliff, et al. Expires January 21, 2016 [Page 28] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 The Destination Down Response message MAY contain one of each of the following data items: o Status (Section 9.1) A receiver of a Destination Down Response message without a Status data item MUST behave as if a Status data item with status code 'Success' had been received. 8.13. Destination Update Message A DLEP participant SHOULD send the Destination Update message when it detects some change in the information base for a given destination (remote node or multicast group). Some examples of changes that would prompt a Destination Update message are: o Change in link metrics (e.g., Data Rates) o Layer 3 addressing change To construct a Destination Update message, the Message Type value in the message header is set to 13, from Table 1. The Destination Update message MUST contain one of each of the following data items: o MAC Address (Section 9.7) The Destination Update message MAY contain one of each of the following data items: o Maximum Data Rate (Receive) (Section 9.12) o Maximum Data Rate (Transmit) (Section 9.13) o Current Data Rate (Receive) (Section 9.14) o Current Data Rate (Transmit) (Section 9.15) o Latency (Section 9.16) o Resources (Receive) (Section 9.17) o Resources (Transmit) (Section 9.18) o Relative Link Quality (Receive) (Section 9.19) o Relative Link Quality (Transmit) (Section 9.20) Ratliff, et al. Expires January 21, 2016 [Page 29] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 The Destination Update message MAY contain one or more of the following data items, with different values: o IPv4 Address (Section 9.8) o IPv6 Address (Section 9.9) 8.14. Heartbeat Message A Heartbeat message SHOULD be sent by a DLEP participant every N seconds, where N is defined in the Heartbeat Interval data item of the Session Initialization message (Section 8.3) or Session Initialization Response message (Section 8.4). Note that implementations setting the Heartbeat Interval to 0 effectively sets the interval to an infinite value, therefore this message SHOULD NOT be sent. The message is used by participants to detect when a DLEP session partner (either the modem or the router) is no longer communicating. Participants SHOULD allow two (2) heartbeat intervals to expire with no traffic on the router/modem session before initiating DLEP session termination procedures. To construct a Heartbeat message, the Message Type value in the message header is set to 14, from Table 1. There are no valid data items for the Heartbeat message. 8.15. Link Characteristics Request Message The Link Characteristics Request message MAY be sent by the router to request that the modem initiate changes for specific characteristics of the link. The request can reference either a real destination (e.g., a remote node), or a logical destination (e.g., a multicast group) within the network. The Link Characteristics Request message MAY contain either a Current Data Rate (CDRR or CDRT) data item to request a different datarate than what is currently allocated, a Latency data item to request that traffic delay on the link not exceed the specified value, or both. A Link Characteristics Response message (Section 8.16) is required to complete the request. Issuing a Link Characteristics Request with ONLY the MAC Address data item is a mechanism a peer MAY use to request metrics (via the Link Characteristics Response) from its partner. Ratliff, et al. Expires January 21, 2016 [Page 30] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 The sender of a Link Characteristics Request message MAY attach a timer to the request using the Link Characteristics Response Timer data item. If a Link Characteristics Response message is received after the timer expires, the sender MUST NOT assume that the request succeeded. Implementations are free to define their retry heuristics in event of a timeout. To construct a Link Characteristics Request message, the Message Type value in the message header is set to 15, from Table 1. The Link Characteristics Request message MUST contain one of each of the following data items: o MAC Address (Section 9.7) The Link Characteristics Request message MAY contain one of each of the following data items: o Link Characteristics Response Timer (Section 9.21) o Current Data Rate (Receive) (Section 9.14) o Current Data Rate (Transmit) (Section 9.15) o Latency (Section 9.16) 8.16. Link Characteristics Response Message A DLEP participant MUST send a Link Characteristics Response message to indicate whether a received Link Characteristics Request message (Section 8.15) was successfully processed. The Link Characteristics Response message SHOULD contain a complete set of metric data items, and MUST contain a full set (i.e. those declared in the Session Initialization Response message (Section 8.4)), if metrics were requested by only including a MAC address data item. It MUST contain the same metric types as the request. The values in the metric data items in the Link Characteristics Response message MUST reflect the link characteristics after the request has been processed. If an implementation is not able to alter the characteristics of the link in the manner requested, then a Status data item with status code 'Request Denied', see Table 3, MUST be added to the message. To construct a Link Characteristics Response message, the Message Type value in the message header is set to 16, from Table 1. The Link Characteristics Response message MUST contain one of each of the following data items: Ratliff, et al. Expires January 21, 2016 [Page 31] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 o MAC Address (Section 9.7) The Link Characteristics Response message SHOULD contain one of each of the following data items: o Maximum Data Rate (Receive) (Section 9.12) o Maximum Data Rate (Transmit) (Section 9.13) o Current Data Rate (Receive) (Section 9.14) o Current Data Rate (Transmit) (Section 9.15) o Latency (Section 9.16) The Link Characteristics Response message MAY contain one of each of the following data items: o Resources (Receive) (Section 9.17) o Resources (Transmit) (Section 9.18) o Relative Link Quality (Receive) (Section 9.19) o Relative Link Quality (Transmit) (Section 9.20) o Status (Section 9.1) A receiver of a Link Characteristics Response message without a Status data item MUST behave as if a Status data item with status code 'Success' had been received. 9. DLEP Data Items Following is the list of core data items that MUST be recognized by a DLEP compliant implementation. As mentioned before, not all data items need be used during a session, but an implementation MUST correctly process these data items when correctly associated with a signal or message. The core DLEP data items are: Ratliff, et al. Expires January 21, 2016 [Page 32] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 +-------------+-----------------------------------------------------+ | Type Code | Description | +-------------+-----------------------------------------------------+ | 0 | Reserved | | 1 | Status (Section 9.1) | | 2 | IPv4 Connection Point (Section 9.2) | | 3 | IPv6 Connection Point (Section 9.3) | | 4 | Peer Type (Section 9.4) | | 5 | Heartbeat Interval (Section 9.5) | | 6 | Extensions Supported (Section 9.6) | | 7 | MAC Address (Section 9.7) | | 8 | IPv4 Address (Section 9.8) | | 9 | IPv6 Address (Section 9.9) | | 10 | IPv4 Attached Subnet (Section 9.10) | | 11 | IPv6 Attached Subnet (Section 9.11) | | 12 | Maximum Data Rate (Receive) MDRR) (Section 9.12) | | 13 | Maximum Data Rate (Transmit) (MDRT) (Section 9.13) | | 14 | Current Data Rate (Receive) (CDRR) (Section 9.14) | | 15 | Current Data Rate (Transmit) (CDRT) (Section 9.15) | | 16 | Latency (Section 9.16) | | 17 | Resources (Receive) (RESR) (Section 9.17) | | 18 | Resources (Transmit) (REST) (Section 9.18) | | 19 | Relative Link Quality (Receive) (RLQR) (Section | | | 9.19) | | 20 | Relative Link Quality (Transmit) (RLQT) (Section | | | 9.20) | | 21 | Link Characteristics Response Timer (Section 9.21) | | 22-24 | Credit Windowing (Section 10) extension data items | | 25-65407 | Reserved for future extensions | | 65408-65534 | Private Use. Available for experiments | | 65535 | Reserved | +-------------+-----------------------------------------------------+ Table 2: DLEP Data Item types 9.1. Status The Status data item MAY appear in the Session Initialization Response (Section 8.4), Session Termination (Section 8.7), Session Termination Response (Section 8.8), Session Update Response (Section 8.6), Destination Up Response (Section 8.10), Destination Down Response (Section 8.12) and Link Characteristics Response (Section 8.16) messages. For the Session Termination message (Section 8.7), the Status data item indicates a reason for the termination. For all acknowledgement messages, the Status data item is used to indicate the success or failure of the previously received message. Ratliff, et al. Expires January 21, 2016 [Page 33] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 The status data item includes an optional Text field that can be used to provide a textual description of the status. The use of the Text field is entirely up to the receiving implementation, i.e., it could be output to a log file or discarded. If no Text field is supplied with the Status data item, the Length field MUST be set to 1. The Status data item contains the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Code | Text... : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Data Item Type: 1 Length: 1 + Length of text, in octets Status Code: One of the codes defined in Table 3 below. Text: UTF-8 encoded string, describing the cause, used for implementation defined purposes. Since this field is used for description, implementations SHOULD limit characters in this field to printable characters. Implementations receiving this data item SHOULD check for printable characters in the field. An implementation MUST NOT assume the Text field is NUL-terminated. +-------------+---------+-----------+-------------------------------+ | Status Code | Value | Failure | Reason | | | | Mode | | +-------------+---------+-----------+-------------------------------+ | Success | 0 | Success | The message was processed | | | | | successfully. | | Unknown | 1 | Terminate | The message was not | | Message | | | recognized by the | | | | | implementation. | | Unexpected | 2 | Terminate | The message was not expected | | Message | | | while the device was in the | | | | | current state, e.g., a | | | | | Session Initialization | | | | | message (Section 8.3) in the | | | | | In-Session state. | | Invalid | 3 | Terminate | One or more data items in the | | Data | | | message are invalid, | | | | | unexpected or incorrectly | Ratliff, et al. Expires January 21, 2016 [Page 34] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 | | | | duplicated. | | Invalid | 4 | Terminate | The destination provided in | | Destination | | | the message does not match a | | | | | previously announced | | | | | destination. For example, in | | | | | the Link Characteristic | | | | | Response message (Section | | | | | 8.16). | | <Reserved> | 5-90 | Terminate | Reserved for future | | | | | extensions. | | <Private | 91-99 | Terminate | Available for experiments. | | Use> | | | | | Not | 100 | Continue | The receiver is not | | Interested | | | interested in this message | | | | | subject, e.g. a Destination | | | | | Up Response message (Section | | | | | 8.10) to indicate no further | | | | | messages about the | | | | | destination. | | Request | 101 | Continue | The receiver refuses to | | Denied | | | complete the request. | | Timed Out | 102 | Continue | The operation could not be | | | | | completed in the time | | | | | allowed. | | <Reserved> | 103-243 | Continue | Reserved for future | | | | | extensions. | | <Private | 244-254 | Continue | Available for experiments. | | Use> | | | | | <Reserved> | 255 | Terminate | Reserved. | +-------------+---------+-----------+-------------------------------+ Table 3: DLEP Status Codes A failure mode of 'Terminate' indicates that the session MUST be terminated after sending a response containing the status code. A failure mode of 'Continue' indicates that the session SHOULD continue as normal. 9.2. IPv4 Connection Point The IPv4 Connection Point data item MAY appear in the Peer Offer signal (Section 8.2). The IPv4 Connection Point data item indicates the IPv4 address and, optionally, the TCP port number on the DLEP modem available for connections. If provided, the receiver MUST use this information to perform the TCP connect to the DLEP server. Ratliff, et al. Expires January 21, 2016 [Page 35] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 The IPv4 Connection Point data item contains the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Use TLS | IPv4 Address... : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : ...cont. | TCP Port Number (optional) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Data Item Type: 2 Length: 5 (or 7 if TCP Port included) Use TLS: Value indicating whether the TCP connection should use TLS (1), or not (0). Values other than 0 or 1 MUST be considered as invalid. IPv4 Address: The IPv4 address listening on the DLEP modem. TCP Port Number: TCP Port number on the DLEP modem. If the Length field is 7, the port number specified MUST be used to establish the TCP session. If the TCP Port Number is omitted, i.e. the Length field is 5, the receiver MUST use the DLEP well-known port number (Section 12.7) to establish the TCP connection. 9.3. IPv6 Connection Point The IPv6 Connection Point data item MAY appear in the Peer Offer signal (Section 8.2). The IPv6 Connection Point data item indicates the IPv6 address and, optionally, the TCP port number on the DLEP modem available for connections. If provided, the receiver MUST use this information to perform the TCP connect to the DLEP server. The IPv6 Connection Point data item contains the following fields: Ratliff, et al. Expires January 21, 2016 [Page 36] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Use TLS | IPv6 Address : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : IPv6 Address : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : IPv6 Address : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : IPv6 Address : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : ...cont. | TCP Port Number (optional) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Data Item Type: 3 Length: 17 (or 19 if TCP Port included) Use TLS: Value indicating whether the TCP connection should use TLS (1), or not (0). Values other than 0 or 1 MUST be considered as invalid. IPv6 Address: The IPv6 address listening on the DLEP modem. TCP Port Number: TCP Port number on the DLEP modem. If the Length field is 19, the port number specified MUST be used to establish the TCP session. If the TCP Port Number is omitted, i.e. the Length field is 17, the receiver MUST use the DLEP well-known port number (Section 12.7) to establish the TCP connection. 9.4. Peer Type The Peer Type data item MAY appear in the Peer Discovery (Section 8.1) and Peer Offer (Section 8.2) signals, and the Session Initialization (Section 8.3) and Session Initialization Response (Section 8.4) messages. The Peer Type data item is used by the router and modem to give additional information as to its type. The peer type is a string and is envisioned to be used for informational purposes (e.g., as output in a display command). The Peer Type data item contains the following fields: Ratliff, et al. Expires January 21, 2016 [Page 37] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Peer Type... : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Data Item Type: 4 Length: Length of peer type string, in octets. Peer Type: UTF-8 encoded string. For example, a satellite modem might set this variable to "Satellite terminal". Since this data item is intended to provide additional information for display commands, sending implementations SHOULD limit the data to printable characters, and receiving implmentations SHOULD check the data for printable characters. An implementation MUST NOT assume the Peer Type field is NUL- terminated. 9.5. Heartbeat Interval The Heartbeat Interval data item MUST appear in both the Session Initialization (Section 8.3) and Session Initialization Response (Section 8.4) messages to indicate the Heartbeat timeout window to be used by the sender. The Interval is used to specify a period (in seconds) for Heartbeat messages (Section 8.14). By specifying an Interval value of 0, implementations MAY indicate the desire to disable Heartbeat messages entirely (i.e., the Interval is set to an infinite value). However, it is RECOMMENDED that implementations use non-0 timer values. The Heartbeat Interval data item contains the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interval | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Data Item Type: 5 Length: 2 Ratliff, et al. Expires January 21, 2016 [Page 38] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 Interval: 0 = Do not use heartbeats on this DLEP session. Non-zero = Interval, in seconds, for heartbeat messages. 9.6. Extensions Supported The Extensions Supported data item MAY be used in both the Session Initialization (Section 8.3) and Session Initialization Response (Section 8.4) messages. The Extensions Supported data item is used by the router and modem to negotiate additional optional functionality they are willing to support. The Extensions List is a concatenation of the types of each supported extension, found in the IANA DLEP Extensions repository. Each Extension Type definition includes which additional signals and data-items are supported. The Extensions Supported data item contains the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Extensions List... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Data Item Type: 6 Length: Length of the extensions list in octets. This is twice (2x) the number of extensions. Extension List: A list of extensions supported, identified by their 2-octet value as listed in the extensions registry. 9.7. MAC Address The MAC address data item MUST appear in all destination-oriented messages (i.e., Destination Up (Section 8.9), Destination Up Response (Section 8.10), Destination Down (Section 8.11), Destination Down Response (Section 8.12), Destination Update (Section 8.13), Link Characteristics Request (Section 8.15), and Link Characteristics Response (Section 8.16)). The MAC Address data item contains the address of the destination on the remote node. The MAC address MAY be either a physical or a virtual destination, and MAY be expressed in EUI-48 or EUI-64 format. Examples of a virtual destination would be a multicast MAC address, or the broadcast MAC (FF:FF:FF:FF:FF:FF). Ratliff, et al. Expires January 21, 2016 [Page 39] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MAC Address : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : MAC Address : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : MAC Address : (if EUI-64 used) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Data Item Type: 7 Length: 6 for EUI-48 format, or 8 for EUI-64 format MAC Address: MAC Address of the destination. 9.8. IPv4 Address The IPv4 Address data item MAY appear in the Session Update (Section 8.5), Destination Up (Section 8.9) and Destination Update (Section 8.13) messages. When included in Destination messages, this data item contains the IPv4 address of the destination. When included in the Session Update message, this data item contains the IPv4 address of the peer. In either case, the data item also contains an indication of whether this is a new or existing address, or is a deletion of a previously known address. The IPv4 Address data item contains the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Add/Drop | IPv4 Address : | Indicator | : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : IPv4 | : Address | +-+-+-+-+-+-+-+-+ Data Item Type: 8 Length: 5 Ratliff, et al. Expires January 21, 2016 [Page 40] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 Add/Drop: Value indicating whether this is a new or existing address (1), or a withdrawal of an address (0). Values other than 0 or 1 MUST be considered as invalid. IPv4 Address: The IPv4 address of the destination or peer. 9.9. IPv6 Address The IPv6 Address data item MAY appear in the Session Update (Section 8.5), Destination Up (Section 8.9) and Destination Update (Section 8.13) messages. When included in Destination messages, this data item contains the IPv6 address of the destination. When included in the Session Update message, this data item contains the IPv6 address of the peer. In either case, the data item also contains an indication of whether this is a new or existing address, or is a deletion of a previously known address. The IPv6 Address data item contains the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Add/Drop | IPv6 Address : | Indicator | : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : IPv6 Address : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : IPv6 Address : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : IPv6 Address : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : IPv6 Address | +-+-+-+-+-+-+-+-+ Data Item Type: 9 Length: 17 Add/Drop: Value indicating whether this is a new or existing address (1), or a withdrawal of an address (0). Values other than 0 or 1 MUST be considered as invalid. IPv6 Address: IPv6 Address of the destination or peer. Ratliff, et al. Expires January 21, 2016 [Page 41] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 9.10. IPv4 Attached Subnet The DLEP IPv4 Attached Subnet allows a device to declare that it has an IPv4 subnet (e.g., a stub network) attached, or that it has become aware of an IPv4 subnet being present at a remote destination. The IPv4 Attached Subnet data item MAY appear in the Destination Up (Section 8.9) message. Once an IPv4 Subnet has been declared on a device, the declaration SHALL NOT be withdrawn without withdrawing the destination (via the Destination Down message (Section 8.11)) and re-issuing the Destination Up message. The DLEP IPv4 Attached Subnet data item contains the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 Attached Subnet | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Prefix Len. | +-+-+-+-+-+-+-+-+ Data Item Type: 10 Length: 5 IPv4 Subnet: The IPv4 subnet reachable at the destination. Prefix Length: Length of the prefix (1-32) for the IPv4 subnet. A prefix length outside the speficied range MUST be considered as invalid. 9.11. IPv6 Attached Subnet The DLEP IPv6 Attached Subnet allows a device to declare that it has an IPv6 subnet (e.g., a stub network) attached, or that it has become aware of an IPv6 subnet being present at a remote destination. The IPv6 Attached Subnet data item MAY appear in the Destination Up (Section 8.9) message. As in the case of the IPv4 attached Subnet data item above, once an IPv6 attached subnet has been declared, it SHALL NOT be withdrawn without withdrawing the destination (via the Destination Down message (Section 8.11)) and re-issuing the Destination Up message. The DLEP IPv6 Attached Subnet data item contains the following fields: Ratliff, et al. Expires January 21, 2016 [Page 42] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv6 Attached Subnet : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : IPv6 Attached Subnet : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : IPv6 Attached Subnet : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : IPv6 Attached Subnet | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Prefix Len. | +-+-+-+-+-+-+-+-+ Data Item Type: 11 Length: 17 IPv4 Subnet: The IPv6 subnet reachable at the destination. Prefix Length: Length of the prefix (1-128) for the IPv6 subnet. A prefix length outside the specified range MUST be considered as invalid. 9.12. Maximum Data Rate (Receive) The Maximum Data Rate (Receive) (MDRR) data item MUST appear in the Session Initialization Response message (Section 8.4), and MAY appear in the Session Update (Section 8.5), Destination Up (Section 8.9), Destination Update (Section 8.13) and Link Characteristics Response (Section 8.16) messages to indicate the maximum theoretical data rate, in bits per second, that can be achieved while receiving data on the link. The Maximum Data Rate (Receive) data item contains the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MDRR (bps) : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : MDRR (bps) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Ratliff, et al. Expires January 21, 2016 [Page 43] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 Data Item Type: 12 Length: 8 Maximum Data Rate (Receive): A 64-bit unsigned integer, representing the maximum theoretical data rate, in bits per second (bps), that can be achieved while receiving on the link. 9.13. Maximum Data Rate (Transmit) The Maximum Data Rate (Transmit) (MDRT) data item MUST appear in the Session Initialization Response message (Section 8.4), and MAY appear in the Session Update (Section 8.5), Destination Up (Section 8.9), Destination Update (Section 8.13) and Link Characteristics Response (Section 8.16) messages to indicate the maximum theoretical data rate, in bits per second, that can be achieved while transmitting data on the link. The Maximum Data Rate (Transmit) data item contains the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MDRT (bps) : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : MDRT (bps) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Data Item Type: 13 Length: 8 Maximum Data Rate (Transmit): A 64-bit unsigned integer, representing the maximum theoretical data rate, in bits per second (bps), that can be achieved while transmitting on the link. 9.14. Current Data Rate (Receive) The Current Data Rate (Receive) (CDRR) data item MUST appear in the Session Initialization Response message (Section 8.4), and MAY appear in the Session Update (Section 8.5), Destination Up (Section 8.9), Destination Update (Section 8.13) and Link Characteristics Response (Section 8.16) messages to indicate the rate at which the link is currently operating for receiving traffic. Ratliff, et al. Expires January 21, 2016 [Page 44] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 When used in the Link Characteristics Request message (Section 8.15), CDRR represents the desired receive rate, in bits per second, on the link. The Current Data Rate (Receive) data item contains the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | CDRR (bps) : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : CDRR (bps) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Data Item Type: 14 Length: 8 Current Data Rate (Receive): A 64-bit unsigned integer, representing the current data rate, in bits per second, that can currently be achieved while receiving traffic on the link. If there is no distinction between current and maximum receive data rates, current data rate receive MUST be set equal to the maximum data rate receive. 9.15. Current Data Rate (Transmit) The Current Data Rate Transmit (CDRT) data item MUST appear in the Session Initialization Response message (Section 8.4), and MAY appear in the Session Update (Section 8.5), Destination Up (Section 8.9), Destination Update (Section 8.13), and Link Characteristics Response (Section 8.16) messages to indicate the rate at which the link is currently operating for transmitting traffic. When used in the Link Characteristics Request message (Section 8.15), CDRT represents the desired transmit rate, in bits per second, on the link. The Current Data Rate (Transmit) data item contains the following fields: Ratliff, et al. Expires January 21, 2016 [Page 45] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | CDRT (bps) : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : CDRT (bps) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Data Item Type: 15 Length: 8 Current Data Rate (Transmit): A 64-bit unsigned integer, representing the current data rate, in bits per second, that can currently be achieved while transmitting traffic on the link. If there is no distinction between current and maximum transmit data rates, current data rate transmit MUST be set equal to the maximum data rate transmit. 9.16. Latency The Latency data item MUST appear in the Session Initialization Response message (Section 8.4), and MAY appear in the Session Update (Section 8.5), Destination Up (Section 8.9), Destination Update (Section 8.13), and Link Characteristics Response (Section 8.16) messages to indicate the amount of latency, in microseconds, on the link. When used in the Link Characteristics Request message (Section 8.15), Latency represents the maximum latency desired on the link. The Latency value is reported as delay. The calculation of latency is implementation dependent. For example, the latency may be a running average calculated from the internal queuing. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Latency : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : Latency | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Ratliff, et al. Expires January 21, 2016 [Page 46] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 Data Item Type: 16 Length: 8 Latency: A 64-bit unsigned integer, representing the transmission delay, in microseconds, that a packet encounters as it is transmitted over the link. 9.17. Resources (Receive) The Resources (Receive) (RESR) data item MAY appear in the Session Initialization Response message (Section 8.4), Session Update (Section 8.5), Destination Up (Section 8.9), Destination Update (Section 8.13) and Link Characteristics Response (Section 8.16) messages to indicate the amount of resources for reception (with 0 meaning 'no resources available', and 100 meaning 'all resources available') at the destination. The list of resources that might be considered is beyond the scope of this document, and is left to implementations to decide. The Resources (Receive) data item contains the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RESR | +-+-+-+-+-+-+-+-+ Data Item Type: 17 Length: 1 Resources (Receive): An 8-bit integer percentage, 0-100, representing the amount of resources allocated to receiving data. Any value greater than 100 MUST be considered as invalid. If a device cannot calculate RESR, this data item SHOULD NOT be issued. 9.18. Resources (Transmit) The Resources (Transmit) (REST) data item MAY appear in the Session Initialization Response message (Section 8.4), Session Update (Section 8.5), Destination Up (Section 8.9), Destination Update (Section 8.13) and Link Characteristics Response (Section 8.16) messages to indicate the amount of resources for transmission (with 0 Ratliff, et al. Expires January 21, 2016 [Page 47] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 meaning 'no resources available', and 100 meaning 'all resources available') at the destination. The list of resources that might be considered is beyond the scope of this document, and is left to implementations to decide. The Resources (Transmit) data item contains the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | REST | +-+-+-+-+-+-+-+-+ Data Item Type: 18 Length: 1 Resources (Transmit): An 8-bit integer percentage, 0-100, representing the amount of resources allocated to transmitting data. Any value greater than 100 MUST be considered as invalid. If a device cannot calculate REST, this data item SHOULD NOT be issued. 9.19. Relative Link Quality (Receive) The Relative Link Quality (Receive) (RLQR) data item MAY appear in the Session Initialization Response message (Section 8.4), Session Update (Section 8.5), Destination Up (Section 8.9), Destination Update (Section 8.13) and Link Characteristics Response (Section 8.16) messages to indicate the quality of the link for receiving data. The Relative Link Quality (Receive) data item contains the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RLQR | +-+-+-+-+-+-+-+-+ Data Item Type: 19 Ratliff, et al. Expires January 21, 2016 [Page 48] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 Length: 1 Relative Link Quality (Receive): A non-dimensional 8-bit integer, 0-100, representing relative link quality. A value of 100 represents a link of the highest quality. Any value greater than 100 MUST be considered as invalid. If a device cannot calculate the RLQR, this data item SHOULD NOT be issued. 9.20. Relative Link Quality (Transmit) The Relative Link Quality (Transmit) (RLQT) data item MAY appear in the Session Initialization Response message (Section 8.4), Session Update (Section 8.5), Destination Up (Section 8.9), Destination Update (Section 8.13) and Link Characteristics Response (Section 8.16) messages to indicate the quality of the link for transmitting data. The Relative Link Quality (Transmit) data item contains the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RLQT | +-+-+-+-+-+-+-+-+ Data Item Type: 20 Length: 1 Relative Link Quality (Transmit): A non-dimensional 8-bit integer, 0-100, representing relative link quality. A value of 100 represents a link of the highest quality. Any value greater than 100 MUST be considered as invalid. If a device cannot calculate the RLQT, this data item SHOULD NOT be issued. 9.21. Link Characteristics Response Timer The Link Characteristics Response Timer data item MAY appear in the Link Characteristics Request message (Section 8.15) to indicate the desired number of seconds the sender will wait for a response to the Ratliff, et al. Expires January 21, 2016 [Page 49] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 request. If this data item is omitted, implementations supporting the Link Characteristics Request SHOULD choose a default value. The Link Characteristics Response Timer data item contains the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interval | +-+-+-+-+-+-+-+-+ Data Item Type: 21 Length: 1 Interval: 0 = Do not use timeouts for this Link Characteristics request. Non-zero = Interval, in seconds, to wait before considering this Link Characteristics Request lost. 10. Credit-Windowing DLEP includes an optional Protocol Extension for a credit-windowing scheme analogous to the one documented in [RFC5578]. In this scheme, data plane traffic flowing between the router and modem is controlled by the availability of credits. Credits are expressed as if two unidirectional windows exist between the modem and router. This document identifies these windows as the 'Modem Receive Window' (MRW), and the 'Router Receive Window' (RRW). If the credit-windowing extension is used, credits MUST be granted by the receiver on a given window - that is, on the 'Modem Receive Window' (MRW), the modem is responsible for granting credits to the router, allowing it (the router) to send data plane traffic to the modem. Likewise, the router is responsible for granting credits on the RRW, which allows the modem to send data plane traffic to the router. Credits are managed on a destination-specific basis; that is, separate credit counts are maintained for each destination requiring the service. Credits do not apply to the DLEP session that exists between routers and modems; they are applied only to the data plane traffic. Credits represent the number of octets, or an increment in the number of octets, that MAY be sent on the given window. When sending data Ratliff, et al. Expires January 21, 2016 [Page 50] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 plane traffic to a credit-enabled peer, the sender MUST decrement the appropriate window by the size of the data being sent. For example, when sending data plane traffic via the modem, the router MUST decriment the 'Modem Receive Window' (MRW) for the corresponding destination. When the number of available credits to the destination reaches 0, a sender MUST stop sending data plane traffic to the destination, until additional credits are supplied. If a peer is able to support the optional credit-windowing extension then it MUST include an Extensions Supported data item (Section 9.6) including the value 1, from Table 4, in the appropriate Session Initialization (Section 8.3) and Session Initialization Response (Section 8.4) message. 10.1. Credit-Windowing Messages The credit-windowing extension introduces no additional DLEP signals or messages. However, if a peer has advertised during session initialization that it supports the credit-windowing extension then the following DLEP messages MAY contain additional credit-windowing data items: 10.1.1. Destination Up Message The Destination Up message MAY contain one of each of the following data items: o Credit Grant (Section 10.2.1) If the Destination Up message does not contain the Credit Grant data item, credits MUST NOT be used for that destination. 10.1.2. Destination Up Response Message If the corresponding Destination Up message contained the Credit Grant data item, the Destination Up Response message MUST contain one of each of the following data items: o Credit Window Status (Section 10.2.2) 10.1.3. Destination Update Message If the corresponding Destination Up message contained the Credit Grant data item, the Destination Update message MUST contain one of each of the following data items: o Credit Window Status (Section 10.2.2) Ratliff, et al. Expires January 21, 2016 [Page 51] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 If the corresponding Destination Up message contained the Credit Grant data item, the Destination Update message MAY contain one of each of the following data items: o Credit Grant (Section 10.2.1) o Credit Request (Section 10.2.3) 10.2. Credit-Windowing Data Items The credit-windowing extension introduces 3 additional data items. If a peer has advertised during session initialization that it supports the credit-windowing extension then it MUST correctly process the following data items: +------------+------------------------------------------------------+ | Type Code | Description | +------------+------------------------------------------------------+ | 22 | Credit Grant (Section 10.2.1) | | 23 | Credit Window Status (Section 10.2.2) | | 24 | Credit Request (Section 10.2.3) | +------------+------------------------------------------------------+ 10.2.1. Credit Grant The Credit Grant data item is sent from a DLEP participant to grant an increment to credits on a window. The Credit Grant data item MAY appear in the Destination Up (Section 8.9) and Destination Update (Section 8.13) messages. The value in a Credit Grant data item represents an increment to be added to any existing credits available on the window. Upon successful receipt and processing of a Credit Grant data item, the receiver MUST respond with a message containing a Credit Window Status data item to report the updated aggregate values for synchronization purposes, and if initializing a new credit window, granting initial credits. When DLEP peers desire to employ the credit-windowing extension, the peer originating the Destination Up message MUST supply an initial, non-zero value as the credit increment of the receive window it controls (i.e., the Modem Receive Window, or Router Receive Window). When receiving a Credit Grant data item on a Destination Up message, the receiver MUST take one of the following actions: 1. Reject the use of credits for this destination, via the Destination Up Response message containing a Status data item (Section 9.1) with a status code of 'Request Denied'. (See Table 3), or Ratliff, et al. Expires January 21, 2016 [Page 52] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 2. Initialize the appropriate window value of zero, then apply the increment specified in the Credit Grant data item. If the initialization completes successfully, the receiver MUST respond to the Destination Up message with a Destination Up Response message that contains a Credit Window Status data item, initializing its receive window. The Credit Grant data item contains the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Credit Increment : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : Credit Increment | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Data Item Type: 22 Length: 8 Reserved: A 64-bit unsigned integer representing the additional credits to be assigned to the credit window. Since credits can only be granted by the receiver on a window, the applicable credit window (either the MRW or the RRW) is derived from the sender of the grant. The Credit Increment MUST NOT cause the window to overflow; if this condition occurs, implementations MUST set the credit window to the maximum value contained in a 64-bit quantity. 10.2.2. Credit Window Status If the credit-window extension is supported by the DLEP participants (both the router and the modem), the Credit Window Status data item MUST be sent by the participant receiving a Credit Grant for a given destination. The Credit Window Status data item contains the following fields: Ratliff, et al. Expires January 21, 2016 [Page 53] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Modem Receive Window Value : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : Modem Receive Window Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Router Receive Window Value : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : Router Receive Window Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Data Item Type: 23 Length: 16 Modem Receive Window Value: A 64-bit unsigned integer, indicating the current number of credits available on the Modem Receive Window, for the destination referred to by the message. Router Receive Window Value: A 64-bit unsigned integer, indicating the current number of credits available on the Router Receive Window, for the destination referred to by the message. 10.2.3. Credit Request The Credit Request data item MAY be sent from either DLEP participant, via the Destination Update message (Section 8.13), to indicate the desire for the partner to grant additional credits in order for data transfer to proceed on the session. If the corresponding Destination Up message (Section 8.9) for this session did not contain a Credit Window Status data item, indicating that credits are to be used on the session, then the Credit Request data item MUST be silently dropped by the receiver. The Credit Request data item contains the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Data Item Type: 24 Length: 0 Ratliff, et al. Expires January 21, 2016 [Page 54] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 11. Security Considerations The potential security concerns when using DLEP are: 1. DLEP peers may be 'spoofed' by an attacker, either at DLEP session initialization, or by injection of messages once a session has been established, and/or 2. DLEP data items could be altered by an attacker, causing the receiving peer to inappropriately alter its information base concerning network status. If the modem and router are separated by more than a single hop, session messages could be altered in order to subvert the behaviour of either or both DLEP participants. Under these circumstances, the use of [TLS] is strongly RECOMMENDED. However, if both devices are directly physically connected, or exist within an externally secured private network then an implementation MAY choose not to use TLS. To avoid potential denial of service attack, it is RECOMMENDED that implementations using the Peer Discovery mechanism maintain an information base of peers that persistently fail Session initialization having provided an acceptable Discovery signal, and ignore discovery signals from such peers. This specification does not address security of the data plane, as it (the data plane) is not affected, and standard security procedures can be employed. 12. IANA Considerations This section specifies requests to IANA. 12.1. Registrations This specification defines: o A new repository for DLEP signals and messages, with sixteen (16) values currently assigned. o Reservation of a Private Use numbering space for experimental DLEP signals and messages. o A new repository for DLEP data items, with twenty-four (24) values currently assigned. o Reservation of a Private Use numbering space in the data items repository for experimental data items. Ratliff, et al. Expires January 21, 2016 [Page 55] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 o A new repository for DLEP status codes, with eight (8) currently assigned. o Reservation of a Private Use numbering space in the status codes repository for experimental status codes. o A new repository for DLEP extensions, with one (1) value currently assigned. o Reservation of a Private Use numbering space in the extension repository for experimental extensions. o A request for allocation of a well-known port for DLEP TCP and UDP communication. o A request for allocation of a multicast IP address for DLEP discovery. 12.2. Expert Review: Evaluation Guidelines No additional guidelines for expert review are anticipated. 12.3. Signal/Message Type Registration A new repository must be created with the values of the DLEP signals and messages. All signal and message values are in the range [0..65535], defined in Table 1. 12.4. DLEP Data Item Registrations A new repository for DLEP data items must be created. All data item values are in the range [0..65535], defined in Table 2. 12.5. DLEP Status Code Registrations A new repository for DLEP status codes must be created. All status codes are in the range [0..255], defined in Table 3. 12.6. DLEP Extensions Registrations A new repository for DLEP extensions must be created. All extension values are in the range [0..65535]. Current allocations are: Ratliff, et al. Expires January 21, 2016 [Page 56] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 +-------------+-----------------------------------------------------+ | Code | Description | +-------------+-----------------------------------------------------+ | 0 | Reserved | | 1 | Credit Windowing (Section 10) | | 2-65519 | Reserved for future extensions | | 65520-65534 | Private Use. Available for experiments | | 65535 | Reserved | +-------------+-----------------------------------------------------+ Table 4: DLEP Extension types 12.7. DLEP Well-known Port It is requested that IANA allocate a well-known port number for DLEP communication. 12.8. DLEP Multicast Address It is requested that IANA allocate a multicast address for DLEP discovery signals. 13. Acknowledgements We would like to acknowledge and thank the members of the DLEP design team, who have provided invaluable insight. The members of the design team are: Teco Boot, Bow-Nan Cheng, John Dowdell, and Henning Rogge. We would also like to acknowledge the influence and contributions of Greg Harrison, Chris Olsen, Martin Duke, Subir Das, Jaewon Kang, Vikram Kaul, Nelson Powell and Victoria Mercieca. 14. References 14.1. Normative References [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>. 14.2. Informative References [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>. Ratliff, et al. Expires January 21, 2016 [Page 57] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 [RFC5578] Berry, B., Ed., Ratliff, S., Paradise, E., Kaiser, T., and M. Adams, "PPP over Ethernet (PPPoE) Extensions for Credit Flow and Link Metrics", RFC 5578, DOI 10.17487/RFC5578, February 2010, <http://www.rfc-editor.org/info/rfc5578>. Appendix A. Discovery Signal Flows Router Modem Signal Description ======================================================================== | Router initiates discovery, starts | a timer, send Peer Discovery |-------Peer Discovery---->|| signal. ~ ~ ~ ~ ~ ~ ~ Router discovery timer expires without receiving Peer Offer. | Router sends another Peer |-------Peer Discovery---------->| Discovery signal. | | Modem receives Peer Discovery | signal. | | Modem sends Peer Offer with |<--------Peer Offer-------------| Connection Point information. : : Router MAY cancel discovery timer : and stop sending Peer Discovery : signals. Appendix B. Peer Level Message Flows B.1. Session Initialization Ratliff, et al. Expires January 21, 2016 [Page 58] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 Router Modem Signal Description ======================================================================== | Router connects to discovered or | pre-configured Modem Connection |---------TCP connect----------> Point. | | Router sends Session Initialization |----Session Initialization----->| message. | | Modem receives Session Initialization | message. | | Modem sends Session Initialization |<--Session Initialization Resp.-| Response, with Success status data item. | | |<<============================>>| Session established. Heartbeats : : begin. B.2. Session Initialization - Refused Router Modem Signal Description ======================================================================== | Router connects to discovered or | pre-configured Modem Connection |---------TCP connect----------> Point. | | Router sends Session Initialization |-----Session Initialization---->| message. | | Modem receives Session Initialization | message, and will not support the | advertised extensions. | | Modem sends Session Initialization | Response, with 'Request Denied' status |<-Session Initialization Resp.--| data item. | | | Router receives negative Session | Initialization Response, closes ||---------TCP close------------|| TCP connection. Ratliff, et al. Expires January 21, 2016 [Page 59] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 B.3. Router Changes IP Addresses Router Modem Signal Description ======================================================================== | Router sends Session Update message to |-------Session Update---------->| announce change of IP address | | Modem receives Session Update message | and updates internal state. | |<----Session Update Response----| Modem sends Session Update Response. B.4. Modem Changes Session-wide Metrics Router Modem Signal Description ======================================================================== | Modem sends Session Update message to | announce change of modem-wide |<--------Session Update---------| metrics | | Router receives Session Update message | and updates internal state. | |----Session Update Response---->| Router sends Session Update Response. B.5. Router Terminates Session Router Modem Signal Description ======================================================================== | Router sends Session Termination |------Session Termination------>| message with Status data item. | | |-------TCP shutdown (send)---> | Router stops sending messages. | | Modem receives Session Termination, | stops counting received heartbeats | and stops sending heartbeats. | | Modem sends Session Termination Response |<---Session Termination Resp.---| with Status 'Success'. | | Modem stops sending messages. | ||---------TCP close------------|| Session terminated. Ratliff, et al. Expires January 21, 2016 [Page 60] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 B.6. Modem Terminates Session Router Modem Signal Description ======================================================================== | Modem sends Session Termination |<----Session Termination--------| message with Status data item. | | Modem stops sending messages. | | Router receives Session Termination, | stops counting received heartbeats | and stops sending heartbeats. | | Router sends Session Termination Response |---Session Termination Resp.--->| with Status 'Success'. | | Router stops sending messages. | ||---------TCP close------------|| Session terminated. B.7. Session Heartbeats Ratliff, et al. Expires January 21, 2016 [Page 61] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 Router Modem Signal Description ======================================================================== |----------Heartbeat------------>| Router sends heartbeat message | | Modem resets heartbeats missed | counter. ~ ~ ~ ~ ~ ~ ~ |---------[Any message]--------->| When the Modem receives any message | from the Router. | | Modem resets heartbeats missed | counter. ~ ~ ~ ~ ~ ~ ~ |<---------Heartbeat-------------| Modem sends heartbeat message | | Router resets heartbeats missed | counter. ~ ~ ~ ~ ~ ~ ~ |<--------[Any message]----------| When the Router receives any | message from the Modem. | | Modem resets heartbeats missed | counter. B.8. Router Detects a Heartbeat timeout Router Modem Signal Description ======================================================================== ||<----------------------| Router misses a heartbeat | ||<----------------------| Router misses too many heartbeats | | |------Session Termination------>| Router sends Session Termination | message with 'Timeout' Status | data item. : : Termination proceeds as above. Ratliff, et al. Expires January 21, 2016 [Page 62] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 B.9. Modem Detects a Heartbeat timeout Router Modem Signal Description ======================================================================== |---------------------->|| Modem misses a heartbeat |---------------------->|| | Modem misses too many heartbeats | | |<-----Session Termination-------| Modem sends Session Termination | message with 'Timeout' Status | data item. : : Termination proceeds as above. Appendix C. Destination Specific Signal Flows C.1. Common Destination Signaling Router Modem Signal Description ======================================================================== | Modem detects a new logical | destination is reachable, and |<-------Destination Up----------| sends Destination Up message. | |------Destination Up Resp.----->| Router sends Destination Up Response. ~ ~ ~ ~ ~ ~ ~ | Modem detects change in logical | destination metrics, and sends |<-------Destination Update------| Destination Update message. ~ ~ ~ ~ ~ ~ ~ | Modem detects change in logical | destination metrics, and sends |<-------Destination Update------| Destination Update message. ~ ~ ~ ~ ~ ~ ~ | Modem detects logical destination | is no longer reachable, and sends |<-------Destination Down--------| Destination Down message. | | Router receives Destination Down, | updates internal state, and sends |------Destination Down Resp.--->| Destination Down Response message. Ratliff, et al. Expires January 21, 2016 [Page 63] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 C.2. Multicast Destination Signaling Router Modem Signal Description ======================================================================== | Router detects a new multicast | destination is in use, and sends |--------Destination Up--------->| Destination Up message. | | Modem updates internal state to | monitor multicast destination, and |<-----Destination Up Resp.------| sends Destination Up Response. ~ ~ ~ ~ ~ ~ ~ | Modem detects change in multicast | destination metrics, and sends |<-------Destination Update------| Destination Update message. ~ ~ ~ ~ ~ ~ ~ | Modem detects change in multicast | destination metrics, and sends |<-------Destination Update------| Destination Update message. ~ ~ ~ ~ ~ ~ ~ | Router detects multicast | destination is no longer in use, |--------Destination Down------->| and sends Destination Down message. | | Modem receives Destination Down, | updates internal state, and sends |<-----Destination Down Resp.----| Destination Down Response message. C.3. Link Characteristics Request Ratliff, et al. Expires January 21, 2016 [Page 64] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 Router Modem Signal Description ======================================================================== Destination has already been ~ ~ ~ ~ ~ ~ ~ announced by either peer. | Router requires different | Characteristics for the | destination, and sends Link |--Link Characteristics Request->| Characteristics Request message. | | Modem attempts to adjust link | status to meet the received | request, and sends a Link | Characteristics Response |<---Link Characteristics Resp.--| message with the new values. Authors' Addresses Stan Ratliff VT iDirect 13861 Sunrise Valley Drive, Suite 300 Herndon, VA 20171 USA Email: sratliff@idirect.net Bo Berry Shawn Jury Cisco Systems 170 West Tasman Drive San Jose, CA 95134 USA Email: sjury@cisco.com Darryl Satterwhite Broadcom Email: dsatterw@broadcom.com Ratliff, et al. Expires January 21, 2016 [Page 65] Internet-Draft Dynamic Link Exchange Protocol (DLEP) July 2015 Rick Taylor Airbus Defence & Space Quadrant House Celtic Springs Coedkernew Newport NP10 8FZ UK Email: rick.taylor@airbus.com Ratliff, et al. Expires January 21, 2016 [Page 66]