Dynamic Link Exchange Protocol (DLEP)
RFC 8175
| Document | Type | RFC - Proposed Standard (June 2017; Errata) | |
|---|---|---|---|
| Authors | Stan Ratliff , Shawn Jury , Darryl Satterwhite , Rick Taylor , Bo Berry | ||
| Last updated | 2021-03-11 | ||
| Replaces | draft-sratliff-manet-dlep | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text html pdf htmlized bibtex | ||
| Reviews | |||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Justin Dean | ||
| Shepherd write-up | Show (last changed 2016-03-23) | ||
| IESG | IESG state | RFC 8175 (Proposed Standard) | |
| Action Holders |
(None)
|
||
| Consensus Boilerplate | Yes | ||
| Telechat date | |||
| Responsible AD | Alvaro Retana | ||
| Send notices to | aretana@cisco.com | ||
| IANA | IANA review state | Version Changed - Review Needed | |
| IANA action state | RFC-Ed-Ack | ||
Internet Engineering Task Force (IETF) S. Ratliff
Request for Comments: 8175 VT iDirect
Category: Standards Track S. Jury
ISSN: 2070-1721 Cisco Systems
D. Satterwhite
Broadcom
R. Taylor
Airbus Defence & Space
B. Berry
June 2017
Dynamic Link Exchange Protocol (DLEP)
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. This document
introduces a new protocol called the Dynamic Link Exchange Protocol
(DLEP), which provides a bidirectional, event-driven communication
channel between the router and the modem to facilitate communication
of changing link characteristics.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc8175.
Ratliff, et al. Standards Track [Page 1]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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
2. Protocol Overview ...............................................7
2.1. Destinations ...............................................8
2.2. Conventions and Terminology ................................9
3. Requirements ....................................................9
4. Implementation Scenarios .......................................10
5. Assumptions ....................................................10
6. Metrics ........................................................11
7. DLEP Session Flow ..............................................12
7.1. Peer Discovery State ......................................12
7.2. Session Initialization State ..............................14
7.3. In-Session State ..........................................14
7.3.1. Heartbeats .........................................15
7.4. Session Termination State .................................15
7.5. Session Reset State .......................................16
7.5.1. Unexpected TCP Connection Termination ..............16
8. Transaction Model ..............................................16
9. Extensions .....................................................17
9.1. Experiments ...............................................18
10. Scalability ...................................................18
11. DLEP Signal and Message Structure .............................18
11.1. DLEP Signal Header .......................................19
11.2. DLEP Message Header ......................................20
11.3. DLEP Generic Data Item ...................................20
12. DLEP Signals and Messages .....................................21
12.1. General Processing Rules .................................21
12.2. Status Code Processing ...................................22
12.3. Peer Discovery Signal ....................................22
12.4. Peer Offer Signal ........................................23
12.5. Session Initialization Message ...........................23
Ratliff, et al. Standards Track [Page 2]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
12.6. Session Initialization Response Message ..................24
12.7. Session Update Message ...................................26
12.8. Session Update Response Message ..........................27
12.9. Session Termination Message ..............................28
12.10. Session Termination Response Message ....................28
12.11. Destination Up Message ..................................28
12.12. Destination Up Response Message .........................30
12.13. Destination Announce Message ............................30
12.14. Destination Announce Response Message ...................31
12.15. Destination Down Message ................................32
12.16. Destination Down Response Message .......................33
12.17. Destination Update Message ..............................33
12.18. Link Characteristics Request Message ....................35
12.19. Link Characteristics Response Message ...................35
12.20. Heartbeat Message .......................................36
13. DLEP Data Items ...............................................37
13.1. Status ...................................................38
13.2. IPv4 Connection Point ....................................41
13.3. IPv6 Connection Point ....................................42
13.4. Peer Type ................................................43
13.5. Heartbeat Interval .......................................45
13.6. Extensions Supported .....................................45
13.7. MAC Address ..............................................46
13.8. IPv4 Address .............................................47
13.8.1. IPv4 Address Processing ...........................48
13.9. IPv6 Address .............................................49
13.9.1. IPv6 Address Processing ...........................50
13.10. IPv4 Attached Subnet ....................................51
13.10.1. IPv4 Attached Subnet Processing ..................52
13.11. IPv6 Attached Subnet ....................................53
13.11.1. IPv6 Attached Subnet Processing ..................54
13.12. Maximum Data Rate (Receive) .............................55
13.13. Maximum Data Rate (Transmit) ............................56
13.14. Current Data Rate (Receive) .............................56
13.15. Current Data Rate (Transmit) ............................57
13.16. Latency .................................................58
13.17. Resources ...............................................59
13.18. Relative Link Quality (Receive) .........................60
13.19. Relative Link Quality (Transmit) ........................60
13.20. Maximum Transmission Unit (MTU) .........................61
14. Security Considerations .......................................62
15. IANA Considerations ...........................................63
15.1. Registrations ............................................63
15.2. Signal Type Registrations ................................63
15.3. Message Type Registrations ...............................64
15.4. DLEP Data Item Registrations .............................65
15.5. DLEP Status Code Registrations ...........................66
Ratliff, et al. Standards Track [Page 3]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
15.6. DLEP Extension Registrations .............................67
15.7. DLEP IPv4 Connection Point Flags .........................68
15.8. DLEP IPv6 Connection Point Flags .........................68
15.9. DLEP Peer Type Flags .....................................68
15.10. DLEP IPv4 Address Flags .................................69
15.11. DLEP IPv6 Address Flags .................................69
15.12. DLEP IPv4 Attached Subnet Flags .........................69
15.13. DLEP IPv6 Attached Subnet Flags .........................70
15.14. DLEP Well-Known Port ....................................70
15.15. DLEP IPv4 Link-Local Multicast Address ..................70
15.16. DLEP IPv6 Link-Local Multicast Address ..................70
16. References ....................................................71
16.1. Normative References .....................................71
16.2. Informative References ...................................71
Appendix A. Discovery Signal Flows ................................73
Appendix B. Peer-Level Message Flows ..............................73
B.1. Session Initialization .....................................73
B.2. Session Initialization - Refused ...........................74
B.3. Router Changes IP Addresses ................................74
B.4. Modem Changes Session-Wide Metrics .........................75
B.5. Router Terminates Session ..................................75
B.6. Modem Terminates Session ...................................76
B.7. Session Heartbeats .........................................77
B.8. Router Detects a Heartbeat Timeout .........................78
B.9. Modem Detects a Heartbeat Timeout ..........................78
Appendix C. Destination-Specific Message Flows ....................79
C.1. Common Destination Notification ............................79
C.2. Multicast Destination Notification .........................80
C.3. Link Characteristics Request ...............................81
Acknowledgments ...................................................82
Authors' Addresses ................................................82
1. Introduction
There exist today a collection of modem devices that control links of
variable data rate 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
data rate 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 IEEE 802.11 access point serving two associated laptop
computers. In this environment, the answer to the question "What is
the data rate 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
Ratliff, et al. Standards Track [Page 4]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
point, may have a data rate of 54 Mbps for unicast traffic, the other
laptop, being relatively far away or obstructed by some object, can
simultaneously have a data rate of only 32 Mbps 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 24 Mbps
or less).
In addition to utilizing links that have variable data rates, 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 IP routing
protocols tend to rely on interface state and independent timers to
maintain network convergence (e.g., HELLO messages and/or recognition
of DEAD 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. DLEP not only
implements such an event-driven paradigm but does so over a local
(1-hop) TCP session, which guarantees delivery of the event messages.
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 data rate, leads to a situation where finding the
(current) best route through the network to a given node 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 data rate 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 that additional data rate will be allocated; rather, it may
result in data loss and additional retransmissions on the link.
Ratliff, et al. Standards Track [Page 5]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
Addressing the challenges listed above, the Dynamic Link Exchange
Protocol, or DLEP, has been developed. DLEP runs between a router
and its attached modem devices, allowing the modem devices to
communicate (1) link characteristics as they change and
(2) convergence events (acquisition and loss of potential routing
next hops). Figures 1 and 2 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 DLEP.
The message consists of an indication of what change has occurred on
the link (e.g., the 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 (data rate, latency, etc.) that have
changed. DLEP is independent of the link type and topology supported
by the modem. Note that DLEP 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 Device
Type A implements a point-to-point link, and Modem Device Type B is
connected via a shared medium. In both cases, DLEP is used to report
the characteristics of the link (data rate, 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 reconverge the network.
Ratliff, et al. Standards Track [Page 6]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
+--------+ +--------+
+----+ Modem | | Modem +---+
| | Device | | Device | |
| | Type A | <===== // ======> | Type A | |
| +--------+ Point-to-Point Link +--------+ |
+---+----+ +---+----+
| Router | | Router |
| | | |
+---+----+ +---+----+
| +--------+ +--------+ |
+-----+ Modem | | Modem | |
| Device | o o o o o o o o | Device +--+
| Type B | o Shared o | Type B |
+--------+ o Medium o +--------+
o o
o o
o o
o
+--------+
| Modem |
| Device |
| Type B |
+---+----+
|
|
+---+----+
| Router |
| |
+--------+
Figure 2: DLEP Network with Multiple Modem Devices
2. Protocol Overview
DLEP defines a set of Messages used by modems and their attached
routers 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. Throughout this document, we refer to
modems/routers participating in a DLEP session as "DLEP
Participants", unless a specific distinction (e.g., modem or router)
is required.
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
Ratliff, et al. Standards Track [Page 7]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
(via multiple logical or physical interfaces), then separate DLEP
sessions exist for each modem or connection. 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 absence of DLEP traffic (including
heartbeats) or (2) is explicitly torn down by one of the DLEP
participants.
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.
Such extensions are defined as additional Messages, Data Items,
and/or status codes, and associated rules of behavior, that are not
defined in this document. DLEP contains a standard mechanism for
router and modem implementations to negotiate the available
extensions to use on a per-session basis.
2.1. Destinations
The router-modem session provides a carrier for information exchange
concerning "destinations" that are available via the modem device.
Destinations can be identified by either the router or the modem and
represent a specific, addressable location that can be reached via
the link(s) managed by 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 destinations
accessible via the modem device, as well as the link characteristics
to those destinations.
A destination can be either physical or logical. The example of a
physical destination would be that of a remote, far-end router
attached via the variable-quality network. It should be noted that
for physical destinations the Media Access Control (MAC) address is
the address of the far-end router, not the modem.
The example of a logical destination is Multicast. Multicast traffic
destined for the variable-quality network (the network accessed via
the 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 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
Ratliff, et al. Standards Track [Page 8]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
would for any other destination in the network. The specific
algorithms a modem would use to derive metrics on logical
destinations are outside the scope of this specification; these
algorithms are left to specific implementations to decide.
In all cases, when this specification uses the term "destination", it
refers to the addressable locations, either logical or physical, that
are accessible by the radio link(s).
2.2. Conventions and Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Requirements
DLEP MUST be implemented on a single Layer 2 domain. The protocol
identifies next-hop destinations by using the MAC address for
delivering data traffic. No manipulation or substitution is
performed; the MAC address supplied in all DLEP Messages is used as
the Destination MAC address for frames emitted by the participating
router. MAC addresses MUST be unique within the context of the
router-modem session.
To enforce the single Layer 2 domain, implementations MUST support
the Generalized TTL Security Mechanism [RFC5082], and implementations
MUST adhere to this specification for all DLEP Messages.
DLEP specifies UDP multicast for single-hop discovery signaling and
TCP for transport of the Messages. Modems and routers participating
in DLEP sessions MUST 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.
DLEP relies on the guaranteed delivery of its Messages between router
and modem, once the 1-hop discovery process is complete -- hence, the
specification of TCP to carry the Messages. Other reliable
transports for the protocol are possible but are outside the scope of
this document.
Ratliff, et al. Standards Track [Page 9]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
4. Implementation Scenarios
During development of this specification, two types of deployments
were discussed.
The first can be viewed as a "dedicated deployment". In this mode,
DLEP routers and modems are either directly connected (e.g., using
crossover cables to connect interfaces) or connected to a dedicated
switch. An example of this type of deployment would be a router with
a line-of-sight radio connected into one interface, with a satellite
modem connected into another interface. In mobile environments, the
router and the connected modem (or modems) are placed into a mobile
platform (e.g., a vehicle, boat, or airplane). In this mode, when a
switch is used, it is possible that a small number of ancillary
devices (e.g., a laptop) are also plugged into the switch. But in
either event, the resulting network segment is constrained to a small
number of devices and is not generally accessible from anywhere else
in the network.
The other type of deployment envisioned can be viewed as a "networked
deployment". In this type of scenario, the DLEP router and modem
(or modems) are placed on a segment that is accessible from other
points in the network. In this scenario, not only are the DLEP
router and modem(s) accessible from other points in the network; the
router and a given modem could be multiple physical hops away from
each other. This scenario necessitates the use of Layer 2 tunneling
technology to enforce the single-hop requirement of DLEP.
5. Assumptions
DLEP assumes that a signaling protocol exists between modems
participating in a network. This specification does not define the
character or behavior of this over-the-air signaling but does expect
some information to be carried (or derived) by the signaling,
such as the arrival and departure of modems from this network,
and the variation of the link characteristics between modems.
This information is then assumed to be used by the modem to
implement DLEP.
This specification assumes that the link between router and modem is
static with respect to data rate and latency and that this link is
not likely to be the cause of a performance bottleneck. In
deployments where the router and modem are physically separated by
multiple network hops, served by Layer 2 tunneling technology, DLEP
statistics on the RF links could be insufficient for routing
protocols to make appropriate routing decisions. This would
Ratliff, et al. Standards Track [Page 10]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
especially become an issue in cases where the Layer 2 tunnel between
router and modem is itself served in part (or in total) with a
wireless backhaul link.
6. Metrics
DLEP includes the ability for the router and modem to communicate
metrics that reflect the characteristics (e.g., data rate, 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 by a "best effort", incorporating
all pertinent data that is available to the modem device. Metrics
based on large-enough sample sizes will preclude short traffic bursts
from adversely skewing reported values.
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 the session
level, the router propagates the metrics to all entries in its
information base for destinations that are accessed via the modem.
DLEP modems announce all metric Data Items that will be reported
during the session, and provide default values for those metrics, in
the Session Initialization Response Message (Section 12.6). In order
to use a metric type that was not included in the Session
Initialization Response Message, modem implementations terminate the
session with the router (via the Session Termination Message
(Section 12.9)) and establish a new session.
A DLEP modem can send metrics in both (1) a session context, via the
Session Update Message (Section 12.7) and (2) a specific destination
context, via the Destination Update Message (Section 12.17), at any
time. The most recently received metric value takes precedence over
any earlier value, regardless of context -- that is:
1. If the router receives metrics in a specific destination context
(via the Destination Update Message), then the specific
destination is updated with the new metric.
2. If the router receives metrics in a session-wide context (via the
Session Update Message), then the metrics for all destinations
accessed via the modem are updated with the new metric.
Ratliff, et al. Standards Track [Page 11]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
It is left to implementations to choose sensible default values based
on their specific characteristics. Modems having static
(non-changing) link metric characteristics can report metrics only
once for a given destination (or once on a session-wide basis, if all
connections via the modem are of this static nature).
In addition to communicating existing metrics about the link, DLEP
provides a Message allowing a router to request a different data rate
or latency from the modem. This Message is the Link Characteristics
Request Message (Section 12.18); it gives the router the ability to
deal with requisite increases (or decreases) of allocated
data rate/latency in demand-based schemes in a more deterministic
manner.
7. DLEP Session Flow
All DLEP participants of a session transition through a number of
distinct states during the lifetime of a DLEP session:
o Peer Discovery
o Session Initialization
o In-Session
o Session Termination
o Session Reset
Modems, and routers supporting DLEP discovery, transition through all
five of the above states. Routers that rely on preconfigured TCP
address/port information start in the Session Initialization state.
Modems MUST support the Peer Discovery state.
7.1. Peer Discovery State
Modems MUST support DLEP Peer Discovery; routers MAY support the
discovery signals or rely on a priori configuration to locate modems.
If a router chooses to support DLEP discovery, all signals MUST be
supported.
In the Peer Discovery state, routers that support DLEP discovery MUST
send Peer Discovery Signals (Section 12.3) to initiate modem
discovery.
Ratliff, et al. Standards Track [Page 12]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
The router implementation then waits for a Peer Offer Signal
(Section 12.4) response from a potential DLEP modem. While in the
Peer Discovery state, Peer Discovery Signals MUST be sent repeatedly
by a DLEP router, at regular intervals. It is RECOMMENDED that this
interval be set to 60 seconds. The interval MUST be a minimum of
1 second; it SHOULD be a configurable parameter. Note that this
operation (sending Peer Discovery and waiting for Peer Offer) is
outside the DLEP transaction model (Section 8), as the transaction
model only describes Messages on a TCP session.
Routers receiving a Peer Offer Signal MUST use one of the modem
address/port combinations from the Peer Offer Signal to establish a
TCP connection to the modem, even if a priori configuration exists.
If multiple Connection Point Data Items exist in the received Peer
Offer Signal, routers SHOULD prioritize IPv6 connection points over
IPv4 connection points. If multiple connection points exist with the
same transport (e.g., IPv6 or IPv4), 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 Connection Point
Data Items are included in the Peer Offer Signal, the router MUST use
the source address of the UDP packet containing the Peer Offer Signal
as the IP address, and the DLEP well-known port number.
In the Peer Discovery state, the modem implementation MUST listen for
incoming Peer Discovery Signals on the DLEP well-known IPv6 and/or
IPv4 link-local multicast address and port. On receipt of a valid
Peer Discovery Signal, it MUST reply with a Peer Offer Signal.
Modems MUST 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 preceding Peer Discovery Signal.
Implementations of DLEP SHOULD implement, and use, Transport Layer
Security (TLS) [RFC5246] to protect the TCP session. The "dedicated
deployments" discussed in "Implementation Scenarios" (Section 4) MAY
consider the use of DLEP without TLS. For all "networked
deployments" (again, discussed in "Implementation Scenarios"), the
implementation and use of TLS are STRONGLY RECOMMENDED. If TLS is to
be used, then the TLS session MUST be established before any Messages
are passed between peers. Routers supporting TLS MUST prioritize
connection points using TLS over those that do not.
Upon establishment of a TCP connection, and the establishment of a
TLS session if TLS is in use, both modem and router enter the Session
Initialization state. It is up to the router implementation if Peer
Discovery Signals continue to be sent after the device has
Ratliff, et al. Standards Track [Page 13]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
transitioned to the Session Initialization state. Modem
implementations MUST silently ignore Peer Discovery Signals from a
router with which a given implementation already has a TCP
connection.
7.2. Session Initialization State
On entering the Session Initialization state, the router MUST send a
Session Initialization Message (Section 12.5) to the modem. The
router MUST then wait for receipt of a Session Initialization
Response Message (Section 12.6) from the modem. Receipt of the
Session Initialization Response Message containing a Status Data Item
(Section 13.1) with status code set to 0 'Success' (see Table 2 in
Section 13.1) 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 of a Session Initialization Message, the modem MUST send a
Session Initialization Response Message, and the session MUST
transition to the In-Session 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 it MUST terminate
the TCP connection and transition to the Session Reset state.
DLEP provides an extension negotiation capability to be used in the
Session Initialization state; see Section 9. Extensions supported by
an implementation MUST be declared to potential DLEP participants
using the Extensions Supported Data Item (Section 13.6). Once both
DLEP participants 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.
7.3. In-Session State
In the In-Session state, Messages can flow in both directions between
DLEP participants, 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. Standards Track [Page 14]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
The In-Session state is maintained until one of the following
conditions occurs:
o The implementation terminates the session by sending a Session
Termination Message (Section 12.9), or
o Its peer terminates the session, indicated by receiving a Session
Termination Message.
The implementation MUST then transition to the Session Termination
state.
7.3.1. Heartbeats
In order to maintain the In-Session state, periodic Heartbeat
Messages (Section 12.20) MUST be exchanged between router and modem.
These Messages are intended to keep the session alive and to verify
bidirectional connectivity between the two DLEP participants. It is
RECOMMENDED that the interval timer between Heartbeat Messages be set
to 60 seconds. The interval MUST be a minimum of 1 second; it SHOULD
be a configurable parameter.
Each DLEP participant 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, additional Heartbeat Messages).
An implementation MUST allow a minimum of 2 heartbeat intervals to
expire with no Messages from its peer before terminating the session.
When terminating the session, a Session Termination Message
containing a Status Data Item (Section 13.1) with status code set to
132 'Timed Out' (see Table 2) MUST be sent, and then the
implementation MUST transition to the Session Termination state.
7.4. Session Termination State
When an implementation enters the Session Termination state after
sending a Session Termination Message (Section 12.9) as the result of
an invalid Message or error, it MUST wait for a Session Termination
Response Message (Section 12.10) from its peer. A sender SHOULD
allow 4 heartbeat intervals to expire before assuming that its peer
is unresponsive and before continuing with session termination. Any
other Message received while waiting MUST be silently ignored.
Ratliff, et al. Standards Track [Page 15]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
When the sender of the Session Termination Message receives a Session
Termination Response Message from its peer or times out, it MUST
transition to the Session Reset state.
When an implementation receives a Session Termination Message from
its peer, it enters the Session Termination state, and then it MUST
immediately send a Session Termination Response and transition to the
Session Reset state.
7.5. Session Reset State
In the Session Reset state, the implementation MUST perform the
following actions:
o Release all resources allocated for the session.
o Eliminate all destinations in the information base represented by
the session. Destination Down Messages (Section 12.15) MUST NOT
be sent.
o Terminate the TCP connection.
Having completed these actions, the implementation SHOULD return to
the relevant initial state:
o For modems: Peer Discovery.
o For routers: either Peer Discovery or Session Initialization,
depending on configuration.
7.5.1. Unexpected TCP Connection Termination
If the TCP connection between DLEP participants is terminated when an
implementation is not in the Session Reset state, the implementation
MUST immediately transition to the Session Reset state.
8. Transaction Model
DLEP defines a simple Message transaction model: only one request per
destination may be in progress at a time per session. A Message
transaction is considered complete when a response matching a
previously issued request is received. If a DLEP participant
receives a request for a destination for which there is already an
outstanding request, the implementation MUST terminate the session by
issuing a Session Termination Message (Section 12.9) containing a
Status Data Item (Section 13.1) with status code set to
129 'Unexpected Message' (see Table 2) and transition to the Session
Ratliff, et al. Standards Track [Page 16]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
Termination state. There is no restriction on the total number of
Message transactions in progress at a time, as long as each
transaction refers to a different destination.
It should be noted that some requests may take a considerable amount
of time for some DLEP participants to complete; for example, a modem
handling a multicast Destination Up request may have to perform a
complex network reconfiguration. A sending implementation MUST be
able to handle such long-running transactions gracefully.
Additionally, only one session request, e.g., a Session
Initialization Message (Section 12.5), may be in progress at a time
per session. As noted above for Message transactions, a session
transaction is considered complete when a response matching a
previously issued request is received. If a DLEP participant
receives a session request while there is already a session request
in progress, it MUST terminate the session by issuing a Session
Termination Message containing a Status Data Item with status code
set to 129 'Unexpected Message' and transition to the Session
Termination state. Only the Session Termination Message may be
issued when a session transaction is in progress. Heartbeat Messages
(Section 12.20) MUST NOT be considered part of a session transaction.
DLEP transactions do not time out and are not cancellable, except for
transactions in flight when the DLEP session is reset. If the
session is terminated, canceling transactions in progress MUST be
performed as part of resetting the state machine. An implementation
can detect if its peer has failed in some way by use of the session
heartbeat mechanism during the In-Session state; see Section 7.3.
9. Extensions
Extensions MUST be negotiated on a per-session basis during session
initialization via the Extensions Supported mechanism.
Implementations are not required to support any extensions in order
to be considered DLEP compliant.
If interoperable protocol extensions are required, they will need to
be standardized as either (1) an update to this document or (2) an
additional standalone specification. The IANA registries defined in
Section 15 of this document contain sufficient unassigned space for
DLEP Signals, Messages, Data Items, and status codes to accommodate
future extensions to the protocol.
As multiple protocol extensions MAY be announced during session
initialization, authors of protocol extensions need to consider the
interaction of their extensions with other published extensions and
specify any incompatibilities.
Ratliff, et al. Standards Track [Page 17]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
9.1. Experiments
This document registers Private Use [RFC5226] numbering space in the
DLEP Signal, Message, Data Item, and status code registries for
experimental extensions. The intent is to allow for experimentation
with new Signals, Messages, Data Items, and/or status codes while
still retaining the documented DLEP behavior.
During session initialization, the use of the Private Use Signals,
Messages, Data Items, status codes, or behaviors MUST be announced as
DLEP extensions, using extension identifiers from the Private Use
space in the "Extension Type Values" registry (Table 3), with a value
agreed upon (a priori) between the participants. DLEP extensions
using the Private Use numbering space are commonly referred to as
"experiments".
Multiple experiments MAY be announced in the Session Initialization
Messages. However, the 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 establish a
precedence of the conflicting definitions) if such conflicts arise.
10. Scalability
The protocol is intended to support thousands of destinations on a
given modem/router pair. On a large scale, an implementation should
consider employing techniques to prevent flooding its peer with a
large number of Messages in a short time. For example, a dampening
algorithm could be employed to prevent a flapping device from
generating a large number of Destination Up / Destination Down
Messages.
Also, the use of techniques such as a hysteresis can lessen the
impact of rapid, minor fluctuations in link quality. The specific
algorithms for handling flapping destinations and minor changes in
link quality are outside the scope of this specification.
11. 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 bidirectionally over
a TCP connection between the participants, in the Session
Initialization, In-Session, and Session Termination states.
Ratliff, et al. Standards Track [Page 18]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
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 acceptability 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.
11.1. 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 following characters:
U+0044, U+004C, U+0045, U+0050.
Signal Type: A 16-bit unsigned integer containing one of the DLEP
Signal 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 contained in this Signal.
This length MUST NOT include the length of the Signal Header
itself.
The DLEP Signal Header is immediately followed by zero or more DLEP
Data Items, encoded in TLVs, as defined in this document.
Ratliff, et al. Standards Track [Page 19]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
11.2. 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: A 16-bit unsigned integer containing one of the DLEP
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 contained in this Message.
This length MUST NOT include the length of the Message Header
itself.
The DLEP Message Header is immediately followed by zero or more DLEP
Data Items, encoded in TLVs, as defined in this document.
11.3. 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: A 16-bit unsigned integer field specifying the type
of Data Item being sent.
Length: The length in octets, expressed as a 16-bit unsigned
integer, of the Value field of the Data Item. This length
MUST NOT include the length of the Data Item Type and Length
fields.
Value: A field of <Length> octets that contains data specific to a
particular Data Item.
Ratliff, et al. Standards Track [Page 20]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
12. DLEP Signals and Messages
12.1. General Processing Rules
If an unrecognized or unexpected Signal is received or if a received
Signal contains unrecognized, invalid, or disallowed duplicate Data
Items, the receiving implementation MUST ignore the Signal.
If a Signal is received with a TTL value that is NOT equal to 255,
the receiving implementation MUST ignore the Signal.
If an unrecognized Message is received, the receiving implementation
MUST issue a Session Termination Message (Section 12.9) containing a
Status Data Item (Section 13.1) with status code set to 128 'Unknown
Message' (see Table 2) and transition to the Session Termination
state.
If an unexpected Message is received, the receiving implementation
MUST issue a Session Termination Message containing a Status Data
Item with status code set to 129 'Unexpected Message' and transition
to the Session Termination state.
If a received Message contains unrecognized, invalid, or disallowed
duplicate Data Items, the receiving implementation MUST issue a
Session Termination Message containing a Status Data Item with status
code set to 130 'Invalid Data' and transition to the Session
Termination state.
If a packet in the TCP stream is received with a TTL value other than
255, the receiving implementation MUST immediately transition to the
Session Reset state.
Prior to the exchange of Destination Up (Section 12.11) and
Destination Up Response (Section 12.12) Messages, or Destination
Announce (Section 12.13) and Destination Announce Response
(Section 12.14) Messages, no Messages concerning a destination may be
sent. An implementation receiving any Message with such an
unannounced destination MUST terminate the session by issuing a
Session Termination Message containing a Status Data Item with status
code set to 131 'Invalid Destination' and transition to the Session
Termination state.
After exchanging Destination Down (Section 12.15) and Destination
Down Response (Section 12.16) Messages, no Messages concerning a
destination may be sent until a new Destination Up or Destination
Announce Message is sent. An implementation receiving a Message
about a destination previously announced as 'down' MUST terminate the
Ratliff, et al. Standards Track [Page 21]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
session by issuing a Session Termination Message containing a Status
Data Item with status code set to 131 'Invalid Destination' and
transition to the Session Termination state.
12.2. Status Code Processing
The behavior of a DLEP participant receiving a Message containing a
Status Data Item (Section 13.1) is defined by the failure mode
associated with the value of the status code field; see Table 2. All
status code values less than 100 have a failure mode of 'Continue';
all other status codes have a failure mode of 'Terminate'.
A DLEP participant receiving any Message apart from a Session
Termination Message (Section 12.9) containing a Status Data Item with
a status code value with failure mode 'Terminate' MUST immediately
issue a Session Termination Message echoing the received Status Data
Item and then transition to the Session Termination state.
A DLEP participant receiving a Message containing a Status Data Item
with a status code value with failure mode 'Continue' can continue
normal operation of the session.
12.3. Peer Discovery Signal
A Peer Discovery Signal SHOULD be sent by a DLEP router to discover
DLEP modems in the network; see Section 7.1.
A Peer Discovery Signal MUST be encoded within a UDP packet. The
destination MUST be set to the DLEP well-known address and port
number. For routers supporting both IPv4 and IPv6 DLEP operation, it
is RECOMMENDED that IPv6 be selected as the transport. The source IP
address MUST be set to the router IP address associated with the DLEP
interface. There is no DLEP-specific restriction on source port.
To construct a Peer Discovery Signal, the Signal Type value in the
Signal Header is set to 1 (see "Signal Type Registration"
(Section 15.2)).
The Peer Discovery Signal MAY contain a Peer Type Data Item
(Section 13.4).
Ratliff, et al. Standards Track [Page 22]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
12.4. Peer Offer Signal
A Peer Offer Signal MUST be sent by a DLEP modem in response to a
properly formatted and addressed Peer Discovery Signal
(Section 12.3).
A Peer Offer Signal MUST be encoded within a UDP packet. The IP
source and destination fields in the packet MUST be set by swapping
the values received in the Peer Discovery Signal. The Peer Offer
Signal completes the discovery process; see Section 7.1.
To construct a Peer Offer Signal, the Signal Type value in the Signal
Header is set to 2 (see "Signal Type Registration" (Section 15.2)).
The Peer Offer Signal MAY contain a Peer Type Data Item
(Section 13.4).
The Peer Offer Signal MAY contain one or more of any of the following
Data Items, with different values:
o IPv4 Connection Point (Section 13.2)
o IPv6 Connection Point (Section 13.3)
The IPv4 and IPv6 Connection Point Data Items indicate the unicast
address the router MUST use when connecting the DLEP TCP session.
12.5. Session Initialization Message
A Session Initialization Message MUST be sent by a DLEP 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.
To construct a Session Initialization Message, the Message Type value
in the Message Header is set to 1 (see "Message Type Registration"
(Section 15.3)).
The Session Initialization Message MUST contain one of each of the
following Data Items:
o Heartbeat Interval (Section 13.5)
o Peer Type (Section 13.4)
If DLEP extensions are supported, the Session Initialization Message
MUST contain an Extensions Supported Data Item (Section 13.6).
Ratliff, et al. Standards Track [Page 23]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
The Session Initialization Message MAY contain one or more of each of
the following Data Items, with different values and with the Add/Drop
(A) flag (Section 13) set to 1:
o IPv4 Address (Section 13.8)
o IPv6 Address (Section 13.9)
o IPv4 Attached Subnet (Section 13.10)
o IPv6 Attached Subnet (Section 13.11)
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 modem MUST conclude that there is no
support for extensions in the router.
DLEP Heartbeats are not started until receipt of the Session
Initialization Response Message (Section 12.6), and therefore
implementations MUST use their own timeout heuristics for this
Message.
As an exception to the general rule governing an implementation
receiving an unrecognized Data Item in a Message (see Section 12.1),
if a Session Initialization Message contains one or more Extensions
Supported Data Items announcing support for extensions that the
implementation does not recognize, then the implementation MAY ignore
Data Items it does not recognize.
12.6. Session Initialization Response Message
A Session Initialization Response Message MUST be sent by a DLEP
modem in response to a received Session Initialization Message
(Section 12.5).
To construct a Session Initialization Response Message, the Message
Type value in the Message Header is set to 2 (see "Message Type
Registration" (Section 15.3)).
The Session Initialization Response Message MUST contain one of each
of the following Data Items:
o Status (Section 13.1)
o Peer Type (Section 13.4)
o Heartbeat Interval (Section 13.5)
Ratliff, et al. Standards Track [Page 24]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
o Maximum Data Rate (Receive) (Section 13.12)
o Maximum Data Rate (Transmit) (Section 13.13)
o Current Data Rate (Receive) (Section 13.14)
o Current Data Rate (Transmit) (Section 13.15)
o Latency (Section 13.16)
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 (Section 13.17)
o Relative Link Quality (Receive) (Section 13.18)
o Relative Link Quality (Transmit) (Section 13.19)
o Maximum Transmission Unit (MTU) (Section 13.20)
If DLEP extensions are supported, the Session Initialization Response
Message MUST contain an Extensions Supported Data Item
(Section 13.6).
The Session Initialization Response Message MAY contain one or more
of each of the following Data Items, with different values and with
the Add/Drop (A) flag (Section 13) set to 1:
o IPv4 Address (Section 13.8)
o IPv6 Address (Section 13.9)
o IPv4 Attached Subnet (Section 13.10)
o IPv6 Attached Subnet (Section 13.11)
The Session Initialization Response Message completes the DLEP
session establishment; the modem should transition to the In-Session
state when the Message is sent, and the router should transition to
the In-Session state upon receipt 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
session-wide basis. This can be viewed as the modem "declaring" all
supported metrics at DLEP session initialization. Receipt of any
Ratliff, et al. Standards Track [Page 25]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
further 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 router MUST conclude that there is no support
for extensions in the modem.
After the Session Initialization / Session Initialization Response
Messages have been successfully exchanged, implementations MUST only
use extensions that are supported by both DLEP participants; see
Section 7.2.
12.7. Session Update Message
A Session Update Message MAY be sent by a DLEP participant, on a
session-wide basis, to indicate local Layer 3 address changes and/or
metric changes.
To construct a Session Update Message, the Message Type value in the
Message Header is set to 3 (see "Message Type Registration"
(Section 15.3)).
The Session Update Message MAY contain one or more of each of the
following Data Items, with different values:
o IPv4 Address (Section 13.8)
o IPv6 Address (Section 13.9)
o IPv4 Attached Subnet (Section 13.10)
o IPv6 Attached Subnet (Section 13.11)
When sent by a modem, the Session Update Message MAY contain one of
each of the following Data Items:
o Maximum Data Rate (Receive) (Section 13.12)
o Maximum Data Rate (Transmit) (Section 13.13)
o Current Data Rate (Receive) (Section 13.14)
Ratliff, et al. Standards Track [Page 26]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
o Current Data Rate (Transmit) (Section 13.15)
o Latency (Section 13.16)
When sent by a modem, the Session Update Message MAY contain one of
each of the following Data Items, if the Data Item is in use by the
session:
o Resources (Section 13.17)
o Relative Link Quality (Receive) (Section 13.18)
o Relative Link Quality (Transmit) (Section 13.19)
o Maximum Transmission Unit (MTU) (Section 13.20)
If metrics are supplied with the Session Update Message (e.g.,
Maximum Data Rate), these metrics are considered to be session-wide
and therefore MUST be applied to all destinations in the information
base associated with the DLEP session. This includes destinations
for which metrics may have been stored based on received Destination
Update messages.
It should be noted that Session Update Messages can be sent by both
routers and modems. For example, the addition of an IPv4 address on
the router MAY prompt a Session Update Message to its attached
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 and subnets: if the modem is capable of
understanding and forwarding this information (via mechanisms not
defined by DLEP), the update would prompt any remote DLEP-enabled
modems to issue a Destination Update Message (Section 12.17) to their
local routers with the new (or deleted) addresses and subnets.
12.8. Session Update Response Message
A Session Update Response Message MUST be sent by a DLEP participant
when a Session Update Message (Section 12.7) is received.
To construct a Session Update Response Message, the Message Type
value in the Message Header is set to 4 (see "Message Type
Registration" (Section 15.3)).
The Session Update Response Message MUST contain a Status Data Item
(Section 13.1).
Ratliff, et al. Standards Track [Page 27]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
12.9. Session Termination Message
When a DLEP participant determines that the DLEP session needs to be
terminated, the participant MUST send (or attempt to send) a Session
Termination Message.
To construct a Session Termination Message, the Message Type value in
the Message Header is set to 5 (see "Message Type Registration"
(Section 15.3)).
The Session Termination Message MUST contain a Status Data Item
(Section 13.1).
It should be noted that Session Termination Messages can be sent by
both routers and modems.
12.10. Session Termination Response Message
A Session Termination Response Message MUST be sent by a DLEP
participant when a Session Termination Message (Section 12.9) is
received.
To construct a Session Termination Response Message, the Message Type
value in the Message Header is set to 6 (see "Message Type
Registration" (Section 15.3)).
There are no valid Data Items for the Session Termination Response
Message.
Receipt of a Session Termination Response Message completes the
teardown of the DLEP session; see Section 7.4.
12.11. Destination Up Message
Destination Up Messages MAY be sent by a modem to inform its attached
router of the presence of a new reachable destination.
To construct a Destination Up Message, the Message Type value in the
Message Header is set to 7 (see "Message Type Registration"
(Section 15.3)).
The Destination Up Message MUST contain a MAC Address Data Item
(Section 13.7).
Ratliff, et al. Standards Track [Page 28]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
The Destination Up Message SHOULD contain one or more of each of the
following Data Items, with different values:
o IPv4 Address (Section 13.8)
o IPv6 Address (Section 13.9)
The Destination Up Message MAY contain one of each of the following
Data Items:
o Maximum Data Rate (Receive) (Section 13.12)
o Maximum Data Rate (Transmit) (Section 13.13)
o Current Data Rate (Receive) (Section 13.14)
o Current Data Rate (Transmit) (Section 13.15)
o Latency (Section 13.16)
The Destination Up Message MAY contain one of each of the following
Data Items, if the Data Item is in use by the session:
o Resources (Section 13.17)
o Relative Link Quality (Receive) (Section 13.18)
o Relative Link Quality (Transmit) (Section 13.19)
o Maximum Transmission Unit (MTU) (Section 13.20)
The Destination Up Message MAY contain one or more of each of the
following Data Items, with different values:
o IPv4 Attached Subnet (Section 13.10)
o IPv6 Attached Subnet (Section 13.11)
A router receiving a Destination Up Message allocates the necessary
resources, creating an entry in the information base with the
specifics (MAC Address, Latency, Data Rate, etc.) of the destination.
The information about this destination will persist in the router's
information base until a Destination Down Message (Section 12.15) is
received, indicating that the modem has lost contact with the remote
node or that the implementation transitions to the Session
Termination state.
Ratliff, et al. Standards Track [Page 29]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
12.12. Destination Up Response Message
A router MUST send a Destination Up Response Message when a
Destination Up Message (Section 12.11) is received.
To construct a Destination Up Response Message, the Message Type
value in the Message Header is set to 8 (see "Message Type
Registration" (Section 15.3)).
The Destination Up Response Message MUST contain one of each of the
following Data Items:
o MAC Address (Section 13.7)
o Status (Section 13.1)
A router that wishes to receive further information concerning the
destination identified in the corresponding Destination Up Message
MUST set the status code of the included Status Data Item to
0 'Success'; see Table 2.
If the router has no interest in the destination identified in the
corresponding Destination Up Message, then it MAY set the status code
of the included Status Data Item to 1 'Not Interested'.
A modem receiving a Destination Up Response Message containing a
Status Data Item with a status code of any value other than
0 'Success' MUST NOT send further Destination Messages about the
destination, e.g., Destination Down (Section 12.15) or Destination
Update (Section 12.17) with the same MAC address.
12.13. Destination Announce Message
Usually, a modem will discover the presence of one or more remote
router/modem pairs and announce each destination's arrival by sending
a corresponding Destination Up Message (Section 12.11) to the router.
However, there may be times when a router wishes to express an
interest in a destination that has yet to be announced, typically a
multicast destination. Destination Announce Messages MAY be sent by
a router to announce such an interest.
A Destination Announce Message MAY also be sent by a router to
request information concerning a destination (1) in which the router
has previously declined interest, via the 1 'Not Interested' status
code in a Destination Up Response Message (Section 12.12) (see
Table 2) or (2) that was previously declared as 'down', via the
Destination Down Message (Section 12.15).
Ratliff, et al. Standards Track [Page 30]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
To construct a Destination Announce Message, the Message Type value
in the Message Header is set to 9 (see "Message Type Registration"
(Section 15.3)).
The Destination Announce Message MUST contain a MAC Address Data Item
(Section 13.7).
The Destination Announce Message MAY contain zero or more of the
following Data Items, with different values:
o IPv4 Address (Section 13.8)
o IPv6 Address (Section 13.9)
One of the advantages of implementing DLEP is to leverage the modem's
knowledge of the links between remote destinations, allowing routers
to avoid using probed neighbor discovery techniques; therefore, modem
implementations SHOULD announce available destinations via the
Destination Up Message, rather than relying on Destination Announce
Messages.
12.14. Destination Announce Response Message
A modem MUST send a Destination Announce Response Message when a
Destination Announce Message (Section 12.13) is received.
To construct a Destination Announce Response Message, the Message
Type value in the Message Header is set to 10 (see "Message Type
Registration" (Section 15.3)).
The Destination Announce Response Message MUST contain one of each of
the following Data Items:
o MAC Address (Section 13.7)
o Status (Section 13.1)
The Destination Announce Response Message MAY contain one or more of
each of the following Data Items, with different values:
o IPv4 Address (Section 13.8)
o IPv6 Address (Section 13.9)
o IPv4 Attached Subnet (Section 13.10)
o IPv6 Attached Subnet (Section 13.11)
Ratliff, et al. Standards Track [Page 31]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
The Destination Announce Response Message MAY contain one of each of
the following Data Items:
o Maximum Data Rate (Receive) (Section 13.12)
o Maximum Data Rate (Transmit) (Section 13.13)
o Current Data Rate (Receive) (Section 13.14)
o Current Data Rate (Transmit) (Section 13.15)
o Latency (Section 13.16)
The Destination Announce Response Message MAY contain one of each of
the following Data Items, if the Data Item is in use by the session:
o Resources (Section 13.17)
o Relative Link Quality (Receive) (Section 13.18)
o Relative Link Quality (Transmit) (Section 13.19)
o Maximum Transmission Unit (MTU) (Section 13.20)
If a modem is unable to report information immediately about the
requested information -- for example, if the destination is not
currently reachable -- the status code in the Status Data Item MUST
be set to 2 'Request Denied'; see Table 2.
After sending a Destination Announce Response Message containing a
Status Data Item with a status code of 0 'Success', a modem then
announces changes to the link to the destination via Destination
Update Messages.
When a successful Destination Announce Response Message is received,
the router should add knowledge of the available destination to its
information base.
12.15. Destination Down Message
A modem MUST send a Destination Down Message to report when a
destination (a remote node or a multicast group) is no longer
reachable.
A router MAY send a Destination Down Message to report when it
no longer requires information concerning a destination.
Ratliff, et al. Standards Track [Page 32]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
To construct a Destination Down Message, the Message Type value in
the Message Header is set to 11 (see "Message Type Registration"
(Section 15.3)).
The Destination Down Message MUST contain a MAC Address Data Item
(Section 13.7).
It should be noted that both modem and router may send a Destination
Down Message to their peer, regardless of which participant initially
indicated the destination to be 'up'.
12.16. Destination Down Response Message
A Destination Down Response Message MUST be sent by the recipient of
a Destination Down Message (Section 12.15) to confirm that the
relevant data concerning the destination has been removed from the
information base.
To construct a Destination Down Response Message, the Message Type
value in the Message Header is set to 12 (see "Message Type
Registration" (Section 15.3)).
The Destination Down Response Message MUST contain one of each of the
following Data Items:
o MAC Address (Section 13.7)
o Status (Section 13.1)
12.17. Destination Update Message
A modem SHOULD send a 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 as follows:
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 (see "Message Type Registration"
(Section 15.3)).
The Destination Update Message MUST contain a MAC Address Data Item
(Section 13.7).
Ratliff, et al. Standards Track [Page 33]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
The Destination Update Message MAY contain one of each of the
following Data Items:
o Maximum Data Rate (Receive) (Section 13.12)
o Maximum Data Rate (Transmit) (Section 13.13)
o Current Data Rate (Receive) (Section 13.14)
o Current Data Rate (Transmit) (Section 13.15)
o Latency (Section 13.16)
The Destination Update Message MAY contain one of each of the
following Data Items, if the Data Item is in use by the session:
o Resources (Section 13.17)
o Relative Link Quality (Receive) (Section 13.18)
o Relative Link Quality (Transmit) (Section 13.19)
o Maximum Transmission Unit (MTU) (Section 13.20)
The Destination Update Message MAY contain one or more of each of the
following Data Items, with different values:
o IPv4 Address (Section 13.8)
o IPv6 Address (Section 13.9)
o IPv4 Attached Subnet (Section 13.10)
o IPv6 Attached Subnet (Section 13.11)
Metrics supplied in this Message overwrite metrics provided in a
previously received Session Message, Destination Message, or Link
Characteristics Message (e.g., Session Initialization,
Destination Up, Link Characteristics Response).
It should be noted that this Message has no corresponding response.
Ratliff, et al. Standards Track [Page 34]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
12.18. Link Characteristics Request Message
The Link Characteristics Request Message MAY be sent by a 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.
To construct a Link Characteristics Request Message, the Message Type
value in the Message Header is set to 14 (see "Message Type
Registration" (Section 15.3)).
The Link Characteristics Request Message MUST contain a MAC Address
Data Item (Section 13.7).
The Link Characteristics Request Message MUST also contain at least
one of each of the following Data Items:
o Current Data Rate (Receive) (Section 13.14)
o Current Data Rate (Transmit) (Section 13.15)
o Latency (Section 13.16)
The Link Characteristics Request Message MAY contain either a Current
Data Rate (Receive) (CDRR) or Current Data Rate (Transmit) (CDRT)
Data Item to request a different data rate than is currently
allocated, a Latency Data Item to request that traffic delay on the
link not exceed the specified value, or both.
The router sending a Link Characteristics Request Message should be
aware that a request may take an extended period of time to complete.
12.19. Link Characteristics Response Message
A modem MUST send a Link Characteristics Response Message when a Link
Characteristics Request Message (Section 12.18) is received.
To construct a Link Characteristics Response Message, the Message
Type value in the Message Header is set to 15 (see "Message Type
Registration" (Section 15.3)).
The Link Characteristics Response Message MUST contain one of each of
the following Data Items:
o MAC Address (Section 13.7)
o Status (Section 13.1)
Ratliff, et al. Standards Track [Page 35]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
The Link Characteristics Response Message SHOULD contain one of each
of the following Data Items:
o Maximum Data Rate (Receive) (Section 13.12)
o Maximum Data Rate (Transmit) (Section 13.13)
o Current Data Rate (Receive) (Section 13.14)
o Current Data Rate (Transmit) (Section 13.15)
o Latency (Section 13.16)
The Link Characteristics Response Message MAY contain one of each of
the following Data Items, if the Data Item is in use by the session:
o Resources (Section 13.17)
o Relative Link Quality (Receive) (Section 13.18)
o Relative Link Quality (Transmit) (Section 13.19)
o Maximum Transmission Unit (MTU) (Section 13.20)
The Link Characteristics Response Message MUST contain a complete set
of metric Data Items, referencing all metrics declared in the Session
Initialization Response Message (Section 12.6). 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 the status code of the Status Data
Item MUST be set to 2 'Request Denied'; see Table 2.
12.20. Heartbeat Message
A Heartbeat Message MUST be sent by a DLEP participant every
N milliseconds, where N is defined in the Heartbeat Interval Data
Item (Section 13.5) of the Session Initialization Message
(Section 12.5) or Session Initialization Response Message
(Section 12.6).
To construct a Heartbeat Message, the Message Type value in the
Message Header is set to 16 (see "Message Type Registration"
(Section 15.3)).
There are no valid Data Items for the Heartbeat Message.
Ratliff, et al. Standards Track [Page 36]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
The Heartbeat Message is used by DLEP participants to detect when a
DLEP session peer (either the modem or the router) is no longer
communicating; see Section 7.3.1.
13. DLEP Data Items
The core DLEP Data Items are as follows:
+-------------+-----------------------------------------------------+
| Type Code | Description |
+-------------+-----------------------------------------------------+
| 0 | Reserved |
| | |
| 1 | Status (Section 13.1) |
| | |
| 2 | IPv4 Connection Point (Section 13.2) |
| | |
| 3 | IPv6 Connection Point (Section 13.3) |
| | |
| 4 | Peer Type (Section 13.4) |
| | |
| 5 | Heartbeat Interval (Section 13.5) |
| | |
| 6 | Extensions Supported (Section 13.6) |
| | |
| 7 | MAC Address (Section 13.7) |
| | |
| 8 | IPv4 Address (Section 13.8) |
| | |
| 9 | IPv6 Address (Section 13.9) |
| | |
| 10 | IPv4 Attached Subnet (Section 13.10) |
| | |
| 11 | IPv6 Attached Subnet (Section 13.11) |
| | |
| 12 | Maximum Data Rate (Receive) (MDRR) (Section 13.12) |
| | |
| 13 | Maximum Data Rate (Transmit) (MDRT) (Section 13.13) |
| | |
| 14 | Current Data Rate (Receive) (CDRR) (Section 13.14) |
| | |
| 15 | Current Data Rate (Transmit) (CDRT) (Section 13.15) |
| | |
| 16 | Latency (Section 13.16) |
| | |
| 17 | Resources (RES) (Section 13.17) |
| | |
Ratliff, et al. Standards Track [Page 37]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
| 18 | Relative Link Quality (Receive) (RLQR) |
| | (Section 13.18) |
| | |
| 19 | Relative Link Quality (Transmit) (RLQT) |
| | (Section 13.19) |
| | |
| 20 | Maximum Transmission Unit (MTU) (Section 13.20) |
| | |
| 21-65407 | Unassigned (available for future extensions) |
| | |
| 65408-65534 | Reserved for Private Use (available for |
| | experiments) |
| | |
| 65535 | Reserved |
+-------------+-----------------------------------------------------+
Table 1: DLEP Data Item Types
13.1. Status
For the Session Termination Message (Section 12.9), the Status Data
Item indicates a reason for the termination. For all response
messages, the Status Data Item is used to indicate the success or
failure of the previously received Message.
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, e.g., 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status Code | Text... :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: 1
Length: 1 + Length of Text, in octets.
Status Code: One of the status codes defined in Table 2 below.
Ratliff, et al. Standards Track [Page 38]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
Text: UTF-8 encoded string of Unicode [RFC3629] characters,
describing the cause, used for implementation-defined purposes.
Since this field is used for description purposes, implementations
SHOULD limit characters in this field to printable characters.
An implementation MUST NOT assume that the Text field is a
NUL-terminated string of printable characters.
+----------+-------------+------------------+-----------------------+
| Status | Failure | Description | Reason |
| Code | Mode | | |
+----------+-------------+------------------+-----------------------+
| 0 | Continue | Success | The Message was |
| | | | processed |
| | | | successfully. |
| | | | |
| 1 | Continue | Not Interested | The receiver is not |
| | | | interested in this |
| | | | Message subject, |
| | | | e.g., in a |
| | | | Destination Up |
| | | | Response Message |
| | | | (Section 12.12) to |
| | | | indicate no further |
| | | | Messages about the |
| | | | destination. |
| | | | |
| 2 | Continue | Request Denied | The receiver refuses |
| | | | to complete the |
| | | | request. |
| | | | |
| 3 | Continue | Inconsistent | One or more Data |
| | | Data | Items in the Message |
| | | | describe a logically |
| | | | inconsistent state in |
| | | | the network -- for |
| | | | example, in the |
| | | | Destination Up |
| | | | Message |
| | | | (Section 12.11) when |
| | | | an announced subnet |
| | | | clashes with an |
| | | | existing destination |
| | | | subnet. |
| | | | |
Ratliff, et al. Standards Track [Page 39]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
| 4-111 | Continue | <Unassigned> | Available for future |
| | | | extensions. |
| | | | |
| 112-127 | Continue | <Reserved for | Available for |
| | | Private Use> | experiments. |
| | | | |
| 128 | Terminate | Unknown Message | The Message was not |
| | | | recognized by the |
| | | | implementation. |
| | | | |
| 129 | Terminate | Unexpected | The Message was not |
| | | Message | expected while the |
| | | | device was in the |
| | | | current state, e.g., |
| | | | a Session |
| | | | Initialization |
| | | | Message |
| | | | (Section 12.5) in |
| | | | the In-Session state. |
| | | | |
| 130 | Terminate | Invalid Data | One or more Data |
| | | | Items in the Message |
| | | | are invalid, |
| | | | unexpected, or |
| | | | incorrectly |
| | | | duplicated. |
| | | | |
| 131 | Terminate | Invalid | The destination |
| | | Destination | included in the |
| | | | Message does not |
| | | | match a previously |
| | | | announced destination |
| | | | -- for example, in |
| | | | the Link |
| | | | Characteristics |
| | | | Response Message |
| | | | (Section 12.19). |
| | | | |
| 132 | Terminate | Timed Out | The session has |
| | | | timed out. |
| | | | |
| 133-239 | Terminate | <Unassigned> | Available for future |
| | | | extensions. |
| | | | |
Ratliff, et al. Standards Track [Page 40]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
| 240-254 | Terminate | <Reserved for | Available for |
| | | Private Use> | experiments. |
| | | | |
| 255 | Terminate | Shutting Down | The peer is |
| | | | terminating the |
| | | | session, as it is |
| | | | shutting down. |
+----------+-------------+------------------+-----------------------+
Table 2: DLEP Status Codes
13.2. IPv4 Connection Point
The IPv4 Connection Point Data Item indicates the IPv4 address and,
optionally, the TCP port number on the modem available for
connections. If provided, the router MUST use this information to
initiate the TCP connection to the modem.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | IPv4 Address... :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: ...cont. | TCP Port Number (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: 2
Length: 5 (or 7 if TCP Port Number included).
Flags: Flags field, defined below.
IPv4 Address: The IPv4 address listening on the modem.
TCP Port Number: TCP port number on the 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 router MUST use the DLEP well-known port
number (Section 15.14) to establish the TCP connection.
Ratliff, et al. Standards Track [Page 41]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
The Flags field is defined as:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Reserved |T|
+-+-+-+-+-+-+-+-+
T: Use TLS flag, indicating whether the TCP connection to the given
address and port requires the use of TLS [RFC5246] (1) or
not (0).
Reserved: MUST be zero. Left for future assignment.
13.3. IPv6 Connection Point
The IPv6 Connection Point Data Item indicates the IPv6 address and,
optionally, the TCP port number on the modem available for
connections. If provided, the router MUST use this information to
initiate the TCP connection to the modem.
The IPv6 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | IPv6 Address :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Address :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Address :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Address :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: ...cont. | TCP Port Number (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: 3
Length: 17 (or 19 if TCP Port Number included).
Flags: Flags field, defined below.
IPv6 Address: The IPv6 address listening on the modem.
TCP Port Number: TCP port number on the modem.
Ratliff, et al. Standards Track [Page 42]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
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 router MUST use the DLEP well-known port
number (Section 15.14) to establish the TCP connection.
The Flags field is defined as:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Reserved |T|
+-+-+-+-+-+-+-+-+
T: Use TLS flag, indicating whether the TCP connection to the given
address and port requires the use of TLS [RFC5246] (1) or
not (0).
Reserved: MUST be zero. Left for future assignment.
13.4. Peer Type
The Peer Type Data Item is used by the router and modem to give
additional information as to its type and the properties of the
over-the-air control plane.
With some devices, access to the shared RF medium is strongly
controlled. One example of this would be satellite modems -- where
protocols, proprietary in nature, have been developed to ensure that
a given modem has authorization to connect to the shared medium.
Another example of this class of modems is governmental/military
devices, where elaborate mechanisms have been developed to ensure
that only authorized devices can connect to the shared medium.
Contrasting with the above, there are modems where no such access
control is used. An example of this class of modem would be one that
supports the 802.11 ad hoc mode of operation. The Secured Medium (S)
flag is used to indicate if access control is in place.
The Peer Type Data Item includes a textual description of the peer;
it is envisioned that the text will be used for informational
purposes (e.g., as output in a display command).
Ratliff, et al. Standards Track [Page 43]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
The Peer Type 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Description... :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: 4
Length: 1 + Length of Description, in octets.
Flags: Flags field, defined below.
Description: UTF-8 encoded string of Unicode [RFC3629] characters.
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.
An implementation MUST NOT assume that the Description field is a
NUL-terminated string of printable characters.
The Flags field is defined as:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Reserved |S|
+-+-+-+-+-+-+-+-+
S: Secured Medium flag, used by a modem to indicate whether the
shared RF medium implements access control (1) or not (0). The
Secured Medium flag only has meaning in Signals and Messages sent
by a modem.
Reserved: MUST be zero. Left for future assignment.
Ratliff, et al. Standards Track [Page 44]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
13.5. Heartbeat Interval
The Heartbeat Interval Data Item is used to specify a period in
milliseconds for Heartbeat Messages (Section 12.20).
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Heartbeat Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: 5
Length: 4
Heartbeat Interval: The interval in milliseconds, expressed as a
32-bit unsigned integer, for Heartbeat Messages. This value
MUST NOT be 0.
As mentioned before, 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, additional Heartbeat Messages).
13.6. Extensions Supported
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 registry titled "Extension
Type Values". Each Extension Type definition includes which
additional Signals and Data Items are supported.
Ratliff, et al. Standards Track [Page 45]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
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.
Extensions List: A list of extensions supported, identified by their
2-octet values as listed in the "Extension Type Values" registry.
13.7. MAC Address
The MAC Address Data Item contains the address of the destination on
the remote node.
DLEP can support MAC addresses in either EUI-48 or EUI-64 format
("EUI" stands for "Extended Unique Identifier"), 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).
Examples of a virtual destination would be (1) a multicast MAC
address or (2) the broadcast MAC address (FF:FF:FF:FF:FF:FF).
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 : (if EUI-64 used) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Ratliff, et al. Standards Track [Page 46]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
Data Item Type: 7
Length: 6 for EUI-48 format or 8 for EUI-64 format.
MAC Address: MAC address of the destination.
13.8. IPv4 Address
When included in the Session Update Message, this Data Item contains
the IPv4 address of the peer. When included in Destination Messages,
this Data Item contains the IPv4 address of the destination. In
either case, the Data Item also contains an indication of whether
this is (1) a new or existing address or (2) 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | IPv4 Address :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: ...cont. |
+-+-+-+-+-+-+-+-+
Data Item Type: 8
Length: 5
Flags: Flags field, defined below.
IPv4 Address: The IPv4 address of the destination or peer.
The Flags field is defined as:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Reserved |A|
+-+-+-+-+-+-+-+-+
A: Add/Drop flag, indicating whether this is a new or existing
address (1) or a withdrawal of an address (0).
Reserved: MUST be zero. Reserved for future use.
Ratliff, et al. Standards Track [Page 47]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
13.8.1. IPv4 Address Processing
Processing of the IPv4 Address Data Item MUST be done within the
context of the DLEP peer session on which it is presented.
The handling of erroneous or logically inconsistent conditions
depends upon the type of the message that contains the Data Item,
as follows:
If the containing message is a Session Message, e.g., a Session
Initialization Message (Section 12.5) or Session Update Message
(Section 12.7), the receiver of inconsistent information MUST issue a
Session Termination Message (Section 12.9) containing a Status Data
Item (Section 13.1) with status code set to 130 'Invalid Data' and
transition to the Session Termination state. Examples of such
conditions are:
o An address Drop operation referencing an address that is not
associated with the peer in the current session.
o An address Add operation referencing an address that has already
been added to the peer in the current session.
If the containing message is a Destination Message, e.g., a
Destination Up Message (Section 12.11) or Destination Update Message
(Section 12.17), the receiver of inconsistent information MAY issue
the appropriate response message containing a Status Data Item with
status code set to 3 'Inconsistent Data' but MUST continue with
session processing. Examples of such conditions are:
o An address Add operation referencing an address that has already
been added to the destination in the current session.
o An address Add operation referencing an address that is associated
with a different destination or the peer in the current session.
o An address Add operation referencing an address that makes no
sense -- for example, defined as not forwardable in [RFC6890].
o An address Drop operation referencing an address that is not
associated with the destination in the current session.
If no response message is appropriate -- for example, the Destination
Update Message -- then the implementation MUST continue with session
processing.
Modems that do not track IPv4 addresses MUST silently ignore IPv4
Address Data Items.
Ratliff, et al. Standards Track [Page 48]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
13.9. IPv6 Address
When included in the Session Update Message, this Data Item contains
the IPv6 address of the peer. When included in Destination Messages,
this Data Item contains the IPv6 address of the destination. In
either case, the Data Item also contains an indication of whether
this is (1) a new or existing address or (2) 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | IPv6 Address :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Address :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Address :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Address :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Address |
+-+-+-+-+-+-+-+-+
Data Item Type: 9
Length: 17
Flags: Flags field, defined below.
IPv6 Address: The IPv6 address of the destination or peer.
The Flags field is defined as:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Reserved |A|
+-+-+-+-+-+-+-+-+
A: Add/Drop flag, indicating whether this is a new or existing
address (1) or a withdrawal of an address (0).
Reserved: MUST be zero. Reserved for future use.
Ratliff, et al. Standards Track [Page 49]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
13.9.1. IPv6 Address Processing
Processing of the IPv6 Address Data Item MUST be done within the
context of the DLEP peer session on which it is presented.
The handling of erroneous or logically inconsistent conditions
depends upon the type of the message that contains the Data Item,
as follows:
If the containing message is a Session Message, e.g., a Session
Initialization Message (Section 12.5) or Session Update Message
(Section 12.7), the receiver of inconsistent information MUST issue a
Session Termination Message (Section 12.9) containing a Status Data
Item (Section 13.1) with status code set to 130 'Invalid Data' and
transition to the Session Termination state. Examples of such
conditions are:
o An address Drop operation referencing an address that is not
associated with the peer in the current session.
o An address Add operation referencing an address that has already
been added to the peer in the current session.
If the containing message is a Destination Message, e.g., a
Destination Up Message (Section 12.11) or Destination Update Message
(Section 12.17), the receiver of inconsistent information MAY issue
the appropriate response message containing a Status Data Item with
status code set to 3 'Inconsistent Data' but MUST continue with
session processing. Examples of such conditions are:
o An address Add operation referencing an address that has already
been added to the destination in the current session.
o An address Add operation referencing an address that is associated
with a different destination or the peer in the current session.
o An address Add operation referencing an address that makes no
sense -- for example, defined as not forwardable in [RFC6890].
o An address Drop operation referencing an address that is not
associated with the destination in the current session.
If no response message is appropriate -- for example, the Destination
Update Message -- then the implementation MUST continue with session
processing.
Modems that do not track IPv6 addresses MUST silently ignore IPv6
Address Data Items.
Ratliff, et al. Standards Track [Page 50]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
13.10. IPv4 Attached Subnet
The DLEP IPv4 Attached Subnet Data Item allows a device to declare
that it has an IPv4 subnet (e.g., a stub network) attached, that it
has become aware of an IPv4 subnet being present at a remote
destination, or that it has become aware of the loss of a subnet at
the remote destination.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | IPv4 Attached Subnet :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: ...cont. |Prefix Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: 10
Length: 6
Flags: Flags field, defined below.
IPv4 Attached Subnet: The IPv4 subnet reachable at the destination.
Prefix Length: Length of the prefix (0-32) for the IPv4 subnet. A
prefix length outside the specified range MUST be considered as
invalid.
The Flags field is defined as:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Reserved |A|
+-+-+-+-+-+-+-+-+
A: Add/Drop flag, indicating whether this is a new or existing
subnet address (1) or a withdrawal of a subnet address (0).
Reserved: MUST be zero. Reserved for future use.
Ratliff, et al. Standards Track [Page 51]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
13.10.1. IPv4 Attached Subnet Processing
Processing of the IPv4 Attached Subnet Data Item MUST be done within
the context of the DLEP peer session on which it is presented.
If the containing message is a Session Message, e.g., a Session
Initialization Message (Section 12.5) or Session Update Message
(Section 12.7), the receiver of inconsistent information MUST issue a
Session Termination Message (Section 12.9) containing a Status Data
Item (Section 13.1) with status code set to 130 'Invalid Data' and
transition to the Session Termination state. Examples of such
conditions are:
o A subnet Drop operation referencing a subnet that is not
associated with the peer in the current session.
o A subnet Add operation referencing a subnet that has already been
added to the peer in the current session.
If the containing message is a Destination Message, e.g., a
Destination Up Message (Section 12.11) or Destination Update Message
(Section 12.17), the receiver of inconsistent information MAY issue
the appropriate response message containing a Status Data Item with
status code set to 3 'Inconsistent Data' but MUST continue with
session processing. Examples of such conditions are:
o A subnet Add operation referencing a subnet that has already been
added to the destination in the current session.
o A subnet Add operation referencing a subnet that is associated
with a different destination in the current session.
o A subnet Add operation referencing a subnet that makes no sense --
for example, defined as not forwardable in [RFC6890].
o A subnet Drop operation referencing a subnet that is not
associated with the destination in the current session.
If no response message is appropriate -- for example, the Destination
Update Message -- then the implementation MUST continue with session
processing.
Modems that do not track IPv4 subnets MUST silently ignore IPv4
Attached Subnet Data Items.
Ratliff, et al. Standards Track [Page 52]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
13.11. IPv6 Attached Subnet
The DLEP IPv6 Attached Subnet Data Item allows a device to declare
that it has an IPv6 subnet (e.g., a stub network) attached, that it
has become aware of an IPv6 subnet being present at a remote
destination, or that it has become aware of the loss of a subnet at
the remote destination.
The DLEP IPv6 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | IPv6 Attached Subnet :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Attached Subnet :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Attached Subnet :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Attached Subnet :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: ...cont. | Prefix Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: 11
Length: 18
Flags: Flags field, defined below.
IPv6 Attached Subnet: The IPv6 subnet reachable at the destination.
Prefix Length: Length of the prefix (0-128) for the IPv6 subnet. A
prefix length outside the specified range MUST be considered as
invalid.
Ratliff, et al. Standards Track [Page 53]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
The Flags field is defined as:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Reserved |A|
+-+-+-+-+-+-+-+-+
A: Add/Drop flag, indicating whether this is a new or existing
subnet address (1) or a withdrawal of a subnet address (0).
Reserved: MUST be zero. Reserved for future use.
13.11.1. IPv6 Attached Subnet Processing
Processing of the IPv6 Attached Subnet Data Item MUST be done within
the context of the DLEP peer session on which it is presented.
If the containing message is a Session Message, e.g., a Session
Initialization Message (Section 12.5) or Session Update Message
(Section 12.7), the receiver of inconsistent information MUST issue a
Session Termination Message (Section 12.9) containing a Status Data
Item (Section 13.1) with status code set to 130 'Invalid Data' and
transition to the Session Termination state. Examples of such
conditions are:
o A subnet Drop operation referencing a subnet that is not
associated with the peer in the current session.
o A subnet Add operation referencing a subnet that has already been
added to the peer in the current session.
If the containing message is a Destination Message, e.g., a
Destination Up Message (Section 12.11) or Destination Update Message
(Section 12.17), the receiver of inconsistent information MAY issue
the appropriate response message containing a Status Data Item with
status code set to 3 'Inconsistent Data' but MUST continue with
session processing. Examples of such conditions are:
o A subnet Add operation referencing a subnet that has already been
added to the destination in the current session.
o A subnet Add operation referencing a subnet that is associated
with a different destination in the current session.
Ratliff, et al. Standards Track [Page 54]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
o A subnet Add operation referencing a subnet that makes no sense --
for example, defined as not forwardable in [RFC6890].
o A subnet Drop operation referencing a subnet that is not
associated with the destination in the current session.
If no response message is appropriate -- for example, the Destination
Update Message -- then the implementation MUST continue with session
processing.
Modems that do not track IPv6 subnets MUST silently ignore IPv6
Attached Subnet Data Items.
13.12. Maximum Data Rate (Receive)
The Maximum Data Rate (Receive) (MDRR) Data Item is used to indicate
the maximum theoretical data rate, in bits per second (bps), 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) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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, that can be
achieved while receiving on the link.
Ratliff, et al. Standards Track [Page 55]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
13.13. Maximum Data Rate (Transmit)
The Maximum Data Rate (Transmit) (MDRT) Data Item is used 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, that can be achieved while transmitting on the link.
13.14. Current Data Rate (Receive)
The Current Data Rate (Receive) (CDRR) Data Item is used to indicate
the rate at which the link is currently operating for receiving
traffic.
When used in the Link Characteristics Request Message
(Section 12.18), Current Data Rate (Receive) represents the desired
receive rate, in bits per second, on the link.
Ratliff, et al. Standards Track [Page 56]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
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 Data Rate (Receive) and
Maximum Data Rate (Receive) (Section 13.12), Current Data Rate
(Receive) MUST be set equal to Maximum Data Rate (Receive). Current
Data Rate (Receive) MUST NOT exceed Maximum Data Rate (Receive).
13.15. Current Data Rate (Transmit)
The Current Data Rate (Transmit) (CDRT) Data Item is used to indicate
the rate at which the link is currently operating for transmitting
traffic.
When used in the Link Characteristics Request Message
(Section 12.18), Current Data Rate (Transmit) represents the desired
transmit rate, in bits per second, on the link.
The Current 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CDRT (bps) :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: CDRT (bps) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Ratliff, et al. Standards Track [Page 57]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
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 Data Rate (Transmit) and
Maximum Data Rate (Transmit) (Section 13.13), Current Data Rate
(Transmit) MUST be set equal to Maximum Data Rate (Transmit).
Current Data Rate (Transmit) MUST NOT exceed Maximum Data Rate
(Transmit).
13.16. Latency
The Latency Data Item is used to indicate the amount of latency, in
microseconds, on the link.
The Latency value is reported as transmission delay. The calculation
of latency is implementation dependent. For example, the latency may
be a running average calculated from the internal queuing.
The Latency 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Latency :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: Latency |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.
Ratliff, et al. Standards Track [Page 58]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
13.17. Resources
The Resources (RES) Data Item is used to indicate the amount of
finite resources available for data transmission and reception at the
destination as a percentage, with 0 meaning 'no resources remaining'
and 100 meaning 'a full supply', assuming that when Resources reaches
0 data transmission and/or reception will cease.
An example of such resources is battery life, but this could also
include resources such as available memory for queuing, or CPU idle
percentage. The specific criteria to be used for this metric is out
of scope for this specification and is implementation specific.
This Data Item is designed to be used as an indication of some
capability of the modem and/or router at the destination.
The Resources 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RES |
+-+-+-+-+-+-+-+-+
Data Item Type: 17
Length: 1
Resources: An 8-bit unsigned integer percentage, 0-100, representing
the amount of resources available. Any value greater than 100
MUST be considered as invalid.
If a device cannot calculate Resources, this Data Item MUST NOT
be issued.
Ratliff, et al. Standards Track [Page 59]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
13.18. Relative Link Quality (Receive)
The Relative Link Quality (Receive) (RLQR) Data Item is used to
indicate the quality of the link to a destination for receiving
traffic, with 0 meaning 'worst quality' and 100 meaning 'best
quality'.
Quality in this context is defined as an indication of the stability
of a link for reception; a destination with high Relative Link
Quality (Receive) is expected to have generally stable DLEP metrics,
and the metrics of a destination with low Relative Link Quality
(Receive) can be expected to rapidly fluctuate over a wide range.
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: 18
Length: 1
Relative Link Quality (Receive): A non-dimensional unsigned 8-bit
integer, 0-100, representing relative quality of the link for
receiving traffic. Any value greater than 100 MUST be considered
as invalid.
If a device cannot calculate Relative Link Quality (Receive), this
Data Item MUST NOT be issued.
13.19. Relative Link Quality (Transmit)
The Relative Link Quality (Transmit) (RLQT) Data Item is used to
indicate the quality of the link to a destination for transmitting
traffic, with 0 meaning 'worst quality' and 100 meaning 'best
quality'.
Quality in this context is defined as an indication of the stability
of a link for transmission; a destination with high Relative Link
Quality (Transmit) is expected to have generally stable DLEP metrics,
and the metrics of a destination with low Relative Link Quality
(Transmit) can be expected to rapidly fluctuate over a wide range.
Ratliff, et al. Standards Track [Page 60]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
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: 19
Length: 1
Relative Link Quality (Transmit): A non-dimensional unsigned 8-bit
integer, 0-100, representing relative quality of the link for
transmitting traffic. Any value greater than 100 MUST be
considered as invalid.
If a device cannot calculate Relative Link Quality (Transmit), this
Data Item MUST NOT be issued.
13.20. Maximum Transmission Unit (MTU)
The Maximum Transmission Unit (MTU) Data Item is used to indicate the
maximum size, in octets, of an IP packet that can be transmitted
without fragmentation, including headers, but excluding any
lower-layer headers.
The Maximum Transmission Unit 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MTU |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: 20
Length: 2
Maximum Transmission Unit: The maximum size, in octets, of an
IP packet that can be transmitted without fragmentation, including
headers, but excluding any lower-layer headers.
Ratliff, et al. Standards Track [Page 61]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
If a device cannot calculate Maximum Transmission Unit, this Data
Item MUST NOT be issued.
14. Security Considerations
The potential security concerns when using DLEP are as follows:
1. An attacker might pretend to be a DLEP participant, either at
DLEP session initialization or by injection of DLEP Messages once
a session has been established.
2. DLEP Data Items could be altered by an attacker, causing the
receiving implementation to inappropriately alter its information
base concerning network status.
3. An attacker could join an unsecured radio network and inject
over-the-air signals that maliciously influence the information
reported by a DLEP modem, causing a router to forward traffic to
an inappropriate destination.
The implications of attacks on DLEP peers are directly proportional
to the extent to which DLEP data is used within the control plane.
While the use of DLEP data in other control-plane components is out
of scope for this document, as an example, if DLEP statistics are
incorporated into route cost calculations, adversaries masquerading
as a DLEP peer and injecting malicious data via DLEP could cause
suboptimal route selection, adversely impacting network performance.
Similar issues can arise if DLEP data is used as an input to policing
algorithms -- injection of malicious data via DLEP can cause those
policing algorithms to make incorrect decisions, degrading network
throughput.
For these reasons, security of the DLEP transport must be considered
at both the transport layer and Layer 2.
At the transport layer, when TLS is in use, each peer SHOULD check
the validity of credentials presented by the other peer during TLS
session establishment. Implementations following the "dedicated
deployments" model attempting to use TLS MAY (1) need to consider the
use of pre-shared keys for credentials, (2) provide specialized
techniques for peer identity validation, and (3) refer to [RFC5487]
for additional details. Implementations following the "networked
deployment" model described in "Implementation Scenarios" (Section 4)
SHOULD refer to [RFC7525] for additional details.
Ratliff, et al. Standards Track [Page 62]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
At Layer 2, since DLEP is restricted to operation over a single
(possibly logical) hop, implementations SHOULD also secure the
Layer 2 link. Examples of technologies that can be deployed to
secure the Layer 2 link include [IEEE-802.1AE] and [IEEE-802.1X].
By examining the Secured Medium flag in the Peer Type Data Item
(Section 13.4), a router can decide if it is able to trust the
information supplied via a DLEP modem. If this is not the case, then
the router SHOULD consider restricting the size of attached subnets,
announced in IPv4 Attached Subnet Data Items (Section 13.10) and/or
IPv6 Attached Subnet Data Items (Section 13.11), that are considered
for route selection.
To avoid potential denial-of-service attacks, it is RECOMMENDED that
implementations using the Peer Discovery mechanism (1) maintain an
information base of hosts that persistently fail Session
Initialization, even though those hosts have provided an acceptable
Peer Discovery Signal and (2) ignore any subsequent Peer Discovery
Signals from such hosts.
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.
15. IANA Considerations
15.1. Registrations
IANA has created a new protocol registry for the Dynamic Link
Exchange Protocol (DLEP). The remainder of this section details the
new DLEP-specific registries.
15.2. Signal Type Registrations
IANA has created a new DLEP registry, named "Signal Type Values".
Ratliff, et al. Standards Track [Page 63]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
The following table provides initial registry values and the
policies, as defined by [RFC5226], that apply to the registry:
+--------------+--------------------------------------+
| Type Code | Description/Policy |
+--------------+--------------------------------------+
| 0 | Reserved |
| 1 | Peer Discovery Signal |
| 2 | Peer Offer Signal |
| 3-65519 | Unassigned / Specification Required |
| 65520-65534 | Reserved for Private Use |
| 65535 | Reserved |
+--------------+--------------------------------------+
15.3. Message Type Registrations
IANA has created a new DLEP registry, named "Message Type Values".
The following table provides initial registry values and the
policies, as defined by [RFC5226], that apply to the registry:
+--------------+------------------------------------------+
| Type Code | Description/Policy |
+--------------+------------------------------------------+
| 0 | Reserved |
| | |
| 1 | Session Initialization Message |
| | |
| 2 | Session Initialization Response Message |
| | |
| 3 | Session Update Message |
| | |
| 4 | Session Update Response Message |
| | |
| 5 | Session Termination Message |
| | |
| 6 | Session Termination Response Message |
| | |
| 7 | Destination Up Message |
| | |
| 8 | Destination Up Response Message |
| | |
| 9 | Destination Announce Message |
| | |
| 10 | Destination Announce Response Message |
| | |
| 11 | Destination Down Message |
| | |
Ratliff, et al. Standards Track [Page 64]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
| 12 | Destination Down Response Message |
| | |
| 13 | Destination Update Message |
| | |
| 14 | Link Characteristics Request Message |
| | |
| 15 | Link Characteristics Response Message |
| | |
| 16 | Heartbeat Message |
| | |
| 17-65519 | Unassigned / Specification Required |
| | |
| 65520-65534 | Reserved for Private Use |
| | |
| 65535 | Reserved |
+--------------+------------------------------------------+
15.4. DLEP Data Item Registrations
IANA has created a new DLEP registry, named "Data Item Type Values".
The following table provides initial registry values and the
policies, as defined by [RFC5226], that apply to the registry:
+-------------------+------------------------------------------+
| Type Code | Description/Policy |
+-------------------+------------------------------------------+
| 0 | Reserved |
| | |
| 1 | Status |
| | |
| 2 | IPv4 Connection Point |
| | |
| 3 | IPv6 Connection Point |
| | |
| 4 | Peer Type |
| | |
| 5 | Heartbeat Interval |
| | |
| 6 | Extensions Supported |
| | |
| 7 | MAC Address |
| | |
| 8 | IPv4 Address |
| | |
| 9 | IPv6 Address |
| | |
| 10 | IPv4 Attached Subnet |
Ratliff, et al. Standards Track [Page 65]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
| | |
| 11 | IPv6 Attached Subnet |
| | |
| 12 | Maximum Data Rate (Receive) (MDRR) |
| | |
| 13 | Maximum Data Rate (Transmit) (MDRT) |
| | |
| 14 | Current Data Rate (Receive) (CDRR) |
| | |
| 15 | Current Data Rate (Transmit) (CDRT) |
| | |
| 16 | Latency |
| | |
| 17 | Resources (RES) |
| | |
| 18 | Relative Link Quality (Receive) (RLQR) |
| | |
| 19 | Relative Link Quality (Transmit) (RLQT) |
| | |
| 20 | Maximum Transmission Unit (MTU) |
| | |
| 21-65407 | Unassigned / Specification Required |
| | |
| 65408-65534 | Reserved for Private Use |
| | |
| 65535 | Reserved |
+-------------------+------------------------------------------+
15.5. DLEP Status Code Registrations
IANA has created a new DLEP registry, named "Status Code Values".
The following table provides initial registry values and the
policies, as defined by [RFC5226], that apply to the registry:
+--------------+---------------+------------------------------------+
| Status Code | Failure Mode | Description/Policy |
+--------------+---------------+------------------------------------+
| 0 | Continue | Success |
| | | |
| 1 | Continue | Not Interested |
| | | |
| 2 | Continue | Request Denied |
| | | |
| 3 | Continue | Inconsistent Data |
| | | |
| 4-111 | Continue | Unassigned / Specification |
| | | Required |
Ratliff, et al. Standards Track [Page 66]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
| | | |
| 112-127 | Continue | Private Use |
| | | |
| 128 | Terminate | Unknown Message |
| | | |
| 129 | Terminate | Unexpected Message |
| | | |
| 130 | Terminate | Invalid Data |
| | | |
| 131 | Terminate | Invalid Destination |
| | | |
| 132 | Terminate | Timed Out |
| | | |
| 133-239 | Terminate | Unassigned / Specification |
| | | Required |
| | | |
| 240-254 | Terminate | Reserved for Private Use |
| | | |
| 255 | Terminate | Shutting Down |
+--------------+---------------+------------------------------------+
15.6. DLEP Extension Registrations
IANA has created a new DLEP registry, named "Extension Type Values".
The following table provides initial registry values and the
policies, as defined by [RFC5226], that apply to the registry:
+--------------+--------------------------------------+
| Code | Description/Policy |
+--------------+--------------------------------------+
| 0 | Reserved |
| 1-65519 | Unassigned / Specification Required |
| 65520-65534 | Reserved for Private Use |
| 65535 | Reserved |
+--------------+--------------------------------------+
Table 3: DLEP Extension Types
Ratliff, et al. Standards Track [Page 67]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
15.7. DLEP IPv4 Connection Point Flags
IANA has created a new DLEP registry, named "IPv4 Connection Point
Flags".
The following table provides initial registry values and the
policies, as defined by [RFC5226], that apply to the registry:
+------------+--------------------------------------+
| Bit | Description/Policy |
+------------+--------------------------------------+
| 0-6 | Unassigned / Specification Required |
| 7 | Use TLS [RFC5246] indicator |
+------------+--------------------------------------+
15.8. DLEP IPv6 Connection Point Flags
IANA has created a new DLEP registry, named "IPv6 Connection Point
Flags".
The following table provides initial registry values and the
policies, as defined by [RFC5226], that apply to the registry:
+------------+--------------------------------------+
| Bit | Description/Policy |
+------------+--------------------------------------+
| 0-6 | Unassigned / Specification Required |
| 7 | Use TLS [RFC5246] indicator |
+------------+--------------------------------------+
15.9. DLEP Peer Type Flags
IANA has created a new DLEP registry, named "Peer Type Flags".
The following table provides initial registry values and the
policies, as defined by [RFC5226], that apply to the registry:
+------------+--------------------------------------+
| Bit | Description/Policy |
+------------+--------------------------------------+
| 0-6 | Unassigned / Specification Required |
| 7 | Secured Medium indicator |
+------------+--------------------------------------+
Ratliff, et al. Standards Track [Page 68]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
15.10. DLEP IPv4 Address Flags
IANA has created a new DLEP registry, named "IPv4 Address Flags".
The following table provides initial registry values and the
policies, as defined by [RFC5226], that apply to the registry:
+------------+--------------------------------------+
| Bit | Description/Policy |
+------------+--------------------------------------+
| 0-6 | Unassigned / Specification Required |
| 7 | Add/Drop indicator |
+------------+--------------------------------------+
15.11. DLEP IPv6 Address Flags
IANA has created a new DLEP registry, named "IPv6 Address Flags".
The following table provides initial registry values and the
policies, as defined by [RFC5226], that apply to the registry:
+------------+--------------------------------------+
| Bit | Description/Policy |
+------------+--------------------------------------+
| 0-6 | Unassigned / Specification Required |
| 7 | Add/Drop indicator |
+------------+--------------------------------------+
15.12. DLEP IPv4 Attached Subnet Flags
IANA has created a new DLEP registry, named "IPv4 Attached Subnet
Flags".
The following table provides initial registry values and the
policies, as defined by [RFC5226], that apply to the registry:
+------------+--------------------------------------+
| Bit | Description/Policy |
+------------+--------------------------------------+
| 0-6 | Unassigned / Specification Required |
| 7 | Add/Drop indicator |
+------------+--------------------------------------+
Ratliff, et al. Standards Track [Page 69]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
15.13. DLEP IPv6 Attached Subnet Flags
IANA has created a new DLEP registry, named "IPv6 Attached Subnet
Flags".
The following table provides initial registry values and the
policies, as defined by [RFC5226], that apply to the registry:
+------------+--------------------------------------+
| Bit | Description/Policy |
+------------+--------------------------------------+
| 0-6 | Unassigned / Specification Required |
| 7 | Add/Drop indicator |
+------------+--------------------------------------+
15.14. DLEP Well-Known Port
IANA has assigned the value 854 in the "Service Name and Transport
Protocol Port Number Registry" found at
<http://www.iana.org/assignments/service-names-port-numbers/> for use
by "DLEP", as defined in this document. This assignment is valid for
TCP and UDP.
15.15. DLEP IPv4 Link-Local Multicast Address
IANA has assigned the IPv4 multicast address 224.0.0.117 in the
registry found at
<http://www.iana.org/assignments/multicast-addresses> for use as
"DLEP Discovery".
15.16. DLEP IPv6 Link-Local Multicast Address
IANA has assigned the IPv6 multicast address FF02:0:0:0:0:0:1:7 in
the registry found at
<http://www.iana.org/assignments/ipv6-multicast-addresses> for use as
"DLEP Discovery".
Ratliff, et al. Standards Track [Page 70]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
16. References
16.1. 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>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of
ISO 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629,
November 2003, <http://www.rfc-editor.org/info/rfc3629>.
[RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C.
Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007,
<http://www.rfc-editor.org/info/rfc5082>.
[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>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in
RFC 2119 Key Words", BCP 14, RFC 8174,
DOI 10.17487/RFC8174, May 2017,
<http://www.rfc-editor.org/info/rfc8174>.
16.2. Informative References
[IEEE-802.1AE]
"IEEE Standards for Local and Metropolitan Area Networks:
Media Access Control (MAC) Security",
DOI 10.1109/IEEESTD.2006.245590,
<http://ieeexplore.ieee.org/document/1678345/>.
[IEEE-802.1X]
"IEEE Standards for Local and metropolitan area networks--
Port-Based Network Access Control",
DOI 10.1109/IEEESTD.2010.5409813,
<http://ieeexplore.ieee.org/document/5409813/>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
Ratliff, et al. Standards Track [Page 71]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
[RFC5487] Badra, M., "Pre-Shared Key Cipher Suites for TLS with
SHA-256/384 and AES Galois Counter Mode", RFC 5487,
DOI 10.17487/RFC5487, March 2009,
<http://www.rfc-editor.org/info/rfc5487>.
[RFC6890] Cotton, M., Vegoda, L., Bonica, R., Ed., and B. Haberman,
"Special-Purpose IP Address Registries", BCP 153,
RFC 6890, DOI 10.17487/RFC6890, April 2013,
<http://www.rfc-editor.org/info/rfc6890>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525,
May 2015, <http://www.rfc-editor.org/info/rfc7525>.
Ratliff, et al. Standards Track [Page 72]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
Appendix A. Discovery Signal Flows
Router Modem Signal Description
========================================================================
| Router initiates discovery,
| starts a timer, sends Peer
|-------Peer Discovery---->X 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
Router Modem Message Description
========================================================================
| Router connects to discovered or
| preconfigured Modem Connection
|--TCP connection established---> Point.
|
| Router sends Session
|----Session Initialization----->| Initialization Message.
|
| Modem receives Session
| Initialization Message.
|
| Modem sends Session Initialization
|<--Session Initialization Resp.-| Response with 'Success' Status
| | Data Item.
| |
|<<============================>>| Session established.
: : Heartbeats begin.
Ratliff, et al. Standards Track [Page 73]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
B.2. Session Initialization - Refused
Router Modem Message Description
========================================================================
| Router connects to discovered or
| preconfigured Modem Connection
|--TCP connection established---> Point.
|
| Router sends Session
|-----Session Initialization---->| Initialization Message.
|
| Modem receives Session
| Initialization Message and
| will not support the advertised
| extensions.
|
| Modem sends Session Initialization
| Response with 'Request Denied'
|<-Session Initialization Resp.--| Status Data Item.
|
|
| Router receives negative Session
| Initialization Response, closes
||---------TCP close------------|| TCP connection.
B.3. Router Changes IP Addresses
Router Modem Message Description
========================================================================
| Router sends Session Update
|-------Session Update---------->| Message to announce change of
| IP address.
|
| Modem receives Session Update
| Message and updates internal
| state.
|
|<----Session Update Response----| Modem sends Session Update
| Response.
Ratliff, et al. Standards Track [Page 74]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
B.4. Modem Changes Session-Wide Metrics
Router Modem Message Description
========================================================================
| Modem sends Session Update Message
| to announce change of session-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 Message 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
|<---Session Termination Resp.---| Response with Status 'Success'.
|
| Modem stops sending Messages.
|
||---------TCP close------------|| Session terminated.
Ratliff, et al. Standards Track [Page 75]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
B.6. Modem Terminates Session
Router Modem Message 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
|---Session Termination Resp.--->| Response with Status 'Success'.
|
| Router stops sending Messages.
|
||---------TCP close------------|| Session terminated.
Ratliff, et al. Standards Track [Page 76]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
B.7. Session Heartbeats
Router Modem Message 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.
Ratliff, et al. Standards Track [Page 77]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
B.8. Router Detects a Heartbeat Timeout
Router Modem Message Description
========================================================================
X<----------------------| Router misses a heartbeat.
| X<----------------------| Router misses too many
| heartbeats.
|
|
|------Session Termination------>| Router sends Session Termination
| Message with 'Timeout' Status
| Data Item.
:
: Termination proceeds...
B.9. Modem Detects a Heartbeat Timeout
Router Modem Message Description
========================================================================
|---------------------->X Modem misses a heartbeat.
|---------------------->X | Modem misses too many
| heartbeats.
|
|
|<-----Session Termination-------| Modem sends Session Termination
| Message with 'Timeout' Status
| Data Item.
:
: Termination proceeds...
Ratliff, et al. Standards Track [Page 78]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
Appendix C. Destination-Specific Message Flows
C.1. Common Destination Notification
Router Modem Message 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. Standards Track [Page 79]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
C.2. Multicast Destination Notification
Router Modem Message Description
========================================================================
| Router detects a new multicast
| destination is in use and sends
|-----Destination Announce------>| Destination Announce Message.
|
| Modem updates internal state to
| monitor multicast destination and
|<-----Dest. Announce Resp.------| sends Destination Announce
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.
Ratliff, et al. Standards Track [Page 80]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
C.3. Link Characteristics Request
Router Modem Message 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
| properties to meet the received
| request and sends a Link
| Characteristics Response
|<---Link Characteristics Resp.--| Message with the new values.
Ratliff, et al. Standards Track [Page 81]
RFC 8175 Dynamic Link Exchange Protocol (DLEP) June 2017
Acknowledgments
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, Lou Berger, and Victoria Pritchard.
Authors' Addresses
Stan Ratliff
VT iDirect
13861 Sunrise Valley Drive, Suite 300
Herndon, VA 20171
United States of America
Email: sratliff@idirect.net
Shawn Jury
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
United States of America
Email: sjury@cisco.com
Darryl Satterwhite
Broadcom
Email: dsatterw@broadcom.com
Rick Taylor
Airbus Defence & Space
Quadrant House
Celtic Springs
Coedkernew
Newport NP10 8FZ
United Kingdom
Email: rick.taylor@airbus.com
Bo Berry
Ratliff, et al. Standards Track [Page 82]