Mobile Ad hoc Networks Working Group S. Ratliff
Internet-Draft VT iDirect
Intended status: Standards Track B. Berry
Expires: January 7, 2016
S. Jury
Cisco Systems
D. Satterwhite
Broadcom
R. Taylor
Airbus Defence & Space
July 6, 2015
Dynamic Link Exchange Protocol (DLEP)
draft-ietf-manet-dlep-15
Abstract
When routing devices rely on modems to effect communications over
wireless links, they need timely and accurate knowledge of the
characteristics of the link (speed, state, etc.) in order to make
routing decisions. In mobile or other environments where these
characteristics change frequently, manual configurations or the
inference of state through routing or transport protocols does not
allow the router to make the best decisions. A bidirectional, event-
driven communication channel between the router and the modem is
necessary.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 7, 2016.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Protocol Overview . . . . . . . . . . . . . . . . . . . . 7
1.2. Requirements . . . . . . . . . . . . . . . . . . . . . . 8
2. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 8
3. Core Features and Extensions . . . . . . . . . . . . . . . . 10
3.1. Experiments . . . . . . . . . . . . . . . . . . . . . . . 10
4. Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1. Mandatory Metrics . . . . . . . . . . . . . . . . . . . . 12
5. DLEP Session Flow . . . . . . . . . . . . . . . . . . . . . . 12
5.1. Peer Discovery State . . . . . . . . . . . . . . . . . . 12
5.2. Session Initialization State . . . . . . . . . . . . . . 13
5.3. In-Session State . . . . . . . . . . . . . . . . . . . . 14
5.4. Session Termination State . . . . . . . . . . . . . . . . 16
6. DLEP Signal and Message Processing . . . . . . . . . . . . . 16
7. DLEP Signal and Message Structure . . . . . . . . . . . . . . 17
7.1. DLEP Signal Header . . . . . . . . . . . . . . . . . . . 18
7.2. DLEP Message Header . . . . . . . . . . . . . . . . . . . 18
7.3. DLEP Generic Data Item . . . . . . . . . . . . . . . . . 19
8. DLEP Signals and Messages . . . . . . . . . . . . . . . . . . 19
8.1. Peer Discovery Signal . . . . . . . . . . . . . . . . . . 20
8.2. Peer Offer Signal . . . . . . . . . . . . . . . . . . . . 21
8.3. Session Initialization Message . . . . . . . . . . . . . 21
8.4. Session Initialization Response Message . . . . . . . . . 22
8.5. Session Update Message . . . . . . . . . . . . . . . . . 24
8.6. Session Update Response Message . . . . . . . . . . . . . 25
8.7. Session Termination Message . . . . . . . . . . . . . . . 25
8.8. Session Termination Response Message . . . . . . . . . . 26
8.9. Destination Up Message . . . . . . . . . . . . . . . . . 26
8.10. Destination Up Response Message . . . . . . . . . . . . . 27
8.11. Destination Down Message . . . . . . . . . . . . . . . . 28
8.12. Destination Down Response Message . . . . . . . . . . . . 28
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8.13. Destination Update Message . . . . . . . . . . . . . . . 29
8.14. Heartbeat Message . . . . . . . . . . . . . . . . . . . . 30
8.15. Link Characteristics Request Message . . . . . . . . . . 30
8.16. Link Characteristics Response Message . . . . . . . . . . 31
9. DLEP Data Items . . . . . . . . . . . . . . . . . . . . . . . 32
9.1. Status . . . . . . . . . . . . . . . . . . . . . . . . . 33
9.2. IPv4 Connection Point . . . . . . . . . . . . . . . . . . 35
9.3. IPv6 Connection Point . . . . . . . . . . . . . . . . . . 36
9.4. Peer Type . . . . . . . . . . . . . . . . . . . . . . . . 37
9.5. Heartbeat Interval . . . . . . . . . . . . . . . . . . . 38
9.6. Extensions Supported . . . . . . . . . . . . . . . . . . 39
9.7. MAC Address . . . . . . . . . . . . . . . . . . . . . . . 39
9.8. IPv4 Address . . . . . . . . . . . . . . . . . . . . . . 40
9.9. IPv6 Address . . . . . . . . . . . . . . . . . . . . . . 41
9.10. IPv4 Attached Subnet . . . . . . . . . . . . . . . . . . 42
9.11. IPv6 Attached Subnet . . . . . . . . . . . . . . . . . . 42
9.12. Maximum Data Rate (Receive) . . . . . . . . . . . . . . . 43
9.13. Maximum Data Rate (Transmit) . . . . . . . . . . . . . . 44
9.14. Current Data Rate (Receive) . . . . . . . . . . . . . . . 44
9.15. Current Data Rate (Transmit) . . . . . . . . . . . . . . 45
9.16. Latency . . . . . . . . . . . . . . . . . . . . . . . . . 46
9.17. Resources (Receive) . . . . . . . . . . . . . . . . . . . 47
9.18. Resources (Transmit) . . . . . . . . . . . . . . . . . . 47
9.19. Relative Link Quality (Receive) . . . . . . . . . . . . . 48
9.20. Relative Link Quality (Transmit) . . . . . . . . . . . . 49
9.21. Link Characteristics Response Timer . . . . . . . . . . . 49
10. Credit-Windowing . . . . . . . . . . . . . . . . . . . . . . 50
10.1. Credit-Windowing Messages . . . . . . . . . . . . . . . 51
10.1.1. Destination Up Message . . . . . . . . . . . . . . . 51
10.1.2. Destination Up Response Message . . . . . . . . . . 51
10.1.3. Destination Update Message . . . . . . . . . . . . . 51
10.2. Credit-Windowing Data Items . . . . . . . . . . . . . . 52
10.2.1. Credit Grant . . . . . . . . . . . . . . . . . . . . 52
10.2.2. Credit Window Status . . . . . . . . . . . . . . . . 53
10.2.3. Credit Request . . . . . . . . . . . . . . . . . . . 54
11. Security Considerations . . . . . . . . . . . . . . . . . . . 55
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 55
12.1. Registrations . . . . . . . . . . . . . . . . . . . . . 55
12.2. Expert Review: Evaluation Guidelines . . . . . . . . . . 56
12.3. Signal/Message Type Registration . . . . . . . . . . . . 56
12.4. DLEP Data Item Registrations . . . . . . . . . . . . . . 56
12.5. DLEP Status Code Registrations . . . . . . . . . . . . . 56
12.6. DLEP Extensions Registrations . . . . . . . . . . . . . 56
12.7. DLEP Well-known Port . . . . . . . . . . . . . . . . . . 57
12.8. DLEP Multicast Address . . . . . . . . . . . . . . . . . 57
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 57
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 57
14.1. Normative References . . . . . . . . . . . . . . . . . . 57
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14.2. Informative References . . . . . . . . . . . . . . . . . 57
Appendix A. Discovery Signal Flows . . . . . . . . . . . . . . . 58
Appendix B. Peer Level Message Flows . . . . . . . . . . . . . . 58
B.1. Session Initialization . . . . . . . . . . . . . . . . . 58
B.2. Session Initialization - Refused . . . . . . . . . . . . 59
B.3. Router Changes IP Addresses . . . . . . . . . . . . . . . 59
B.4. Modem Changes Session-wide Metrics . . . . . . . . . . . 59
B.5. Router Terminates Session . . . . . . . . . . . . . . . . 60
B.6. Modem Terminates Session . . . . . . . . . . . . . . . . 60
B.7. Session Heartbeats . . . . . . . . . . . . . . . . . . . 61
B.8. Router Detects a Heartbeat timeout . . . . . . . . . . . 62
B.9. Modem Detects a Heartbeat timeout . . . . . . . . . . . . 63
Appendix C. Destination Specific Signal Flows . . . . . . . . . 63
C.1. Common Destination Signaling . . . . . . . . . . . . . . 63
C.2. Multicast Destination Signaling . . . . . . . . . . . . . 64
C.3. Link Characteristics Request . . . . . . . . . . . . . . 64
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 65
1. Introduction
There exist today a collection of modem devices that control links of
variable datarate and quality. Examples of these types of links
include line-of-sight (LOS) terrestrial radios, satellite terminals,
and cable/DSL modems. Fluctuations in speed and quality of these
links can occur due to configuration, or on a moment-to-moment basis,
due to physical phenomena like multipath interference, obstructions,
rain fade, etc. It is also quite possible that link quality and
datarate vary with respect to individual destinations on a link, and
with the type of traffic being sent. As an example, consider the
case of an 802.11 access point, serving 2 associated laptop
computers. In this environment, the answer to the question "What is
the datarate on the 802.11 link?" is "It depends on which associated
laptop we're talking about, and on what kind of traffic is being
sent." While the first laptop, being physically close to the access
point, may have a datarate of 54Mbps for unicast traffic, the other
laptop, being relatively far away, or obstructed by some object, can
simultaneously have a datarate of only 32Mbps for unicast. However,
for multicast traffic sent from the access point, all traffic is sent
at the base transmission rate (which is configurable, but depending
on the model of the access point, is usually 24Mbps or less).
In addition to utilizing variable datarate links, mobile networks are
challenged by the notion that link connectivity will come and go over
time, without an effect on a router's interface state (Up or Down).
Effectively utilizing a relatively short-lived connection is
problematic in IP routed networks, as routing protocols tend to rely
on interface state and independent timers at OSI Layer 3 to maintain
network convergence (e.g., HELLO messages and/or recognition of DEAD
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routing adjacencies). These dynamic connections can be better
utilized with an event-driven paradigm, where acquisition of a new
neighbor (or loss of an existing one) is signaled, as opposed to a
paradigm driven by timers and/or interface state.
Another complicating factor for mobile networks are the different
methods of physically connecting the modem devices to the router.
Modems can be deployed as an interface card in a router's chassis, or
as a standalone device connected to the router via Ethernet or serial
link. In the case of Ethernet attachment, with existing protocols
and techniques, routing software cannot be aware of convergence
events occurring on the radio link (e.g., acquisition or loss of a
potential routing neighbor), nor can the router be aware of the
actual capacity of the link. This lack of awareness, along with the
variability in datarate, leads to a situation where finding the
(current) best route through the network to a given destination is
difficult to establish and properly maintain. This is especially
true of demand-based access schemes such as Demand Assigned Multiple
Access (DAMA) implementations used on some satellite systems. With a
DAMA-based system, additional datarate may be available, but will not
be used unless the network devices emit traffic at a rate higher than
the currently established rate. Increasing the traffic rate does not
guarantee additional datarate will be allocated; rather, it may
result in data loss and additional retransmissions on the link.
Addressing the challenges listed above, the co-authors have developed
the Dynamic Link Exchange Protocol, or DLEP. The DLEP protocol runs
between a router and its attached modem devices, allowing the modem
to communicate link characteristics as they change, and convergence
events (acquisition and loss of potential routing destinations). The
following diagrams are used to illustrate the scope of DLEP packets.
|-------Local Node-------| |-------Remote Node------|
| | | |
+--------+ +-------+ +-------+ +--------+
| Router |=======| Modem |{~~~~~~~~}| Modem |=======| Router |
| | | Device| | Device| | |
+--------+ +-------+ +-------+ +--------+
| | | Link | | |
|-DLEP--| | Protocol | |-DLEP--|
| | | (e.g. | | |
| | | 802.11) | | |
Figure 1: DLEP Network
In Figure 1, when the local modem detects the presence of a remote
node, it (the local modem) sends a message to its router via the DLEP
protocol. The message consists of an indication of what change has
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occurred on the link (e.g., presence of a remote node detected),
along with a collection of DLEP-defined Data Items that further
describe the change. Upon receipt of the message, the local router
may take whatever action it deems appropriate, such as initiating
discovery protocols, and/or issuing HELLO messages to converge the
network. On a continuing, as-needed basis, the modem devices use
DLEP to report any characteristics of the link (datarate, latency,
etc.) that have changed. DLEP is independent of the link type and
topology supported by the modem. Note that the DLEP protocol is
specified to run only on the local link between router and modem.
Some over the air signaling may be necessary between the local and
remote modem in order to provide some parameters in DLEP messages
between the local modem and local router, but DLEP does not specify
how such over the air signaling is carried out. Over the air
signaling is purely a matter for the modem implementer.
Figure 2 shows how DLEP can support a configuration where routers are
connected with different link types. In this example, Modem A
implements a point-to-point link, and Modem B is connected via a
shared medium. In both cases, the DLEP protocol is used to report
the characteristics of the link (datarate, latency, etc.) to routers.
The modem is also able to use the DLEP session to notify the router
when the remote node is lost, shortening the time required to re-
converge the network.
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+--------+ +--------+
+----+ Modem A| | Modem A+---+
| | Device | <===== // ======> | Device | |
| +--------+ P-2-P Link +--------+ |
+---+----+ +---+----+
| Router | | Router |
| | | |
+---+----+ +---+----+
| +--------+ +--------+ |
+-----+ Modem B| | Modem B| |
| Device | o o o o o o o o | Device +--+
+--------+ o Shared o +--------+
o Medium o
o o
o o
o o
o
+--------+
| Modem B|
| Device |
+---+----+
|
|
+---+----+
| Router |
| |
+--------+
Figure 2: DLEP Network with Multiple Modem Devices
1.1. Protocol Overview
As mentioned earlier, DLEP defines a set of messages used by modems
and their attached routers. The messages are used to communicate
events that occur on the physical link(s) managed by the modem: for
example, a remote node entering or leaving the network, or that the
link has changed. Associated with these messages are a set of data
items - information that describes the remote node (e.g., address
information), and/or the characteristics of the link to the remote
node.
The protocol is defined as a collection of type-length-value (TLV)
based formats, specifying the messages that are exchanged between a
router and a modem, and the data items associated with the message.
This document specifies transport of DLEP messages and data items via
the TCP transport, with a UDP-based discovery mechanism. Other
transports for the protocol are possible, but are outside the scope
of this document.
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DLEP uses a session-oriented paradigm between the modem device and
its associated router. If multiple modem devices are attached to a
router (as in Figure 2), or the modem supports multiple connections
(via multiple logical or physical interfaces), then separate DLEP
sessions exist for each modem or connection. This router/modem
session provides a carrier for information exchange concerning
'destinations' that are available via the modem device. A
'destination' can be either physical (as in the case of a specific
far-end router), or a logical destination (as in a Multicast group).
As such, all of the destination-level exchanges in DLEP can be
envisioned as building an information base concerning the remote
nodes, and the link characteristics to those nodes.
Multicast traffic destined for the variable-quality network (the
network accessed via the DLEP modem) is handled in IP networks by
deriving a Layer 2 MAC address based on the Layer 3 address.
Leveraging on this scheme, multicast traffic is supported in DLEP
simply by treating the derived MAC address as any other 'destination'
(albeit a logical one) in the network. To support these logical
destinations, one of the DLEP participants (typically, the router)
informs the other as to the existence of the logical destination.
The modem, once it is aware of the existence of this logical
destination, reports link characteristics just as it would for any
other destination in the network. The specific algorithms a modem
would use to derive metrics on multicast (or logical) destinations
are outside the scope of this specification, and is left to specific
implementations to decide.
1.2. Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14, RFC 2119 [RFC2119].
2. Assumptions
Routers and modems that exist as part of the same node (e.g., that
are locally connected) can use a discovery technique to locate each
other, thus avoiding a priori configuration. The router is
responsible for initializing the discovery process, using the Peer
Discovery signal (Section 8.1).
DLEP uses a session-oriented paradigm. A router and modem form a
session by completing the discovery and initialization process. This
router-modem session persists unless or until it either (1) times
out, based on the timeout values supplied, or (2) is explicitly torn
down by one of the participants. Note that while use of timers in
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DLEP is optional, it is strongly RECOMMENDED that implementations
choose to run with timers enabled.
DLEP assumes that the MAC address for delivering data traffic is the
MAC specified in the Destination Up message (Section 8.9). No
manipulation or substitution is performed; the MAC address supplied
in Destination Up is used as the OSI Layer 2 Destination MAC address.
DLEP also assumes that MAC addresses MUST be unique within the
context of a router-modem session. Additionally, DLEP can support
MAC addresses in either EUI-48 or EUI-64 format, with the restriction
that ALL MAC addresses for a given DLEP session MUST be in the same
format, and MUST be consistent with the MAC address format of the
connected modem (e.g., if the modem is connected to the router with
an EUI-48 MAC, all destination addresses via that modem MUST be
expressed in EUI-48 format).
DLEP uses UDP multicast for single-hop discovery signalling, and TCP
for transport of the control messages. Therefore, DLEP assumes that
the modem and router have topologically consistent IP addresses
assigned. It is RECOMMENDED that DLEP implementations utilize IPv6
link-local addresses to reduce the administrative burden of address
assignment.
Destinations can be identified by either the router or the modem, and
represent a specific destination (e.g., an address) that exists on
the link(s) managed by the modem. A destination MUST contain a MAC
address, it MAY optionally include a Layer 3 address (or addresses).
Note that since a destination is a MAC address, the MAC could
reference a logical destination, as in a derived multicast MAC
address, as well as a physical device. As destinations are
discovered, DLEP routers and modems build an information base on
destinations accessible via the modem.
The DLEP messages concerning destinations thus become the way for
routers and modems to maintain, and notify each other about, an
information base representing the physical and logical (e.g.,
multicast) destinations accessible via the modem device. The
information base would contain addressing information (i.e. MAC
address, and OPTIONALLY, Layer 3 addresses), link characteristics
(metrics), and OPTIONALLY, flow control information (credits).
DLEP assumes that any message not understood by a receiver MUST
result in an error indication being sent to the originator, and also
MUST result in termination of the session between the DLEP peers.
Any DLEP data item not understood by a receiver MUST also result in
termination of the session.
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DLEP assumes that security on the session (e.g., authentication of
session partners, encryption of traffic, or both) is dealt with by
the underlying transport mechanism (e.g., by using a transport such
as TLS [RFC5246]).
This document specifies an implementation of the DLEP messages
running over the TCP transport. It is assumed that DLEP running over
other transport mechanisms would be documented separately.
3. Core Features and Extensions
DLEP has a core set of signals, messages and data items that MUST be
parsed without error by an implementation in order to guarantee
interoperability and therefore make the implementation DLEP
compliant. This document defines this set of signals, messages and
data items, listing them as 'core'. It should be noted that some
core signals, messages and data items might not be used during the
lifetime of a single DLEP session, but a compliant implementation
MUST support them.
While this document represents the best efforts of the working group
to be functionally complete, it is recognized that extensions to DLEP
will in all likelihood be necessary as more link types are used.
If interoperable protocol extensions are required, they MUST be
standardized either as an update to this document, or as an
additional stand-alone specification. The requests for IANA-
controlled registries in this document contain sufficient Reserved
space, in terms of DLEP signals, messages, data items and status
codes, to accommodate future extensions to the protocol and the data
transferred.
All extensions are considered OPTIONAL. Extensions may be negotiated
on a per-session basis during session initialization via the
Extensions Supported mechanism. Only the DLEP functionality listed
as 'core' is required by an implementation in order to be DLEP
compliant.
This specification defines one extension, Credit Windowing, that
devices MAY choose to implement.
3.1. Experiments
This document requests Private Use numbering space in the DLEP
signal/message, data item and status code registries for experimental
items. The intent is to allow for experimentation with new signals,
messages, data items, and/or status codes, while still retaining the
documented DLEP behavior.
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Use of the experimental signals, messages, data items, status codes,
or behaviors MUST be announced as Extensions, using extension
identifiers from the Private Use space in the Extensions Supported
registry (Table 4), during session initialization with a value agreed
upon (a priori) between the participating peers.
Multiple experiments MAY be announced in the Session Initialization
messages. However, use of multiple experiments in a single session
could lead to interoperability issues or unexpected results (e.g.,
clashes of experimental signals, messages, data items and/or status
code types), and is therefore discouraged. It is left to
implementations to determine the correct processing path (e.g., a
decision on whether to terminate the session, or to establish a
precedence of the conflicting definitions) if such conflicts arise.
4. Metrics
DLEP includes the ability for the router and modem to communicate
metrics that reflect the characteristics (e.g., datarate, latency) of
the variable-quality link in use. DLEP does not specify how a given
metric value is to be calculated, rather, the protocol assumes that
metrics have been calculated with a 'best effort', incorporating all
pertinent data that is available to the modem device.
DLEP allows for metrics to be sent within two contexts - metrics for
a specific destination within the network (e.g., a specific router),
and per-session (those that apply to all destinations accessed via
the modem). Most metrics can be further subdivided into transmit and
receive metrics. In cases where metrics are provided at session
level, the receiver MUST propagate the metrics to all entries in its
information base for destinations that are accessed via the
originator.
DLEP modem implementations MUST announce all metric items that will
be reported during the session, and provide default values for those
metrics, in the Session Initialization Response message
(Section 8.4). In order to use a metric type that was not included
in the Session Initialization Response message, modem implementations
MUST terminate the session with the router (via the Session Terminate
message (Section 8.7)), and establish a new session.
It is left to implementations to choose sensible default values based
on their specific characteristics. Modems having static (non-
changing) link metric characteristics MAY report metrics only once
for a given destination (or once on a modem-wide basis, if all
connections via the modem are of this static nature).
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A DLEP participant MAY send metrics both in a session context (via
the Session Update message) and a specific destination context (via
Destination Update) at any time. The heuristics for applying
received metrics is left to implementations.
4.1. Mandatory Metrics
As mentioned above, DLEP modem implementations MUST announce all
supported metric items during the Session Initialization state.
However, a modem MUST include the following list of metrics in the
Session Initialization Response message (Section 8.4):
o Maximum Data Rate (Receive) (Section 9.12)
o Maximum Data Rate (Transmit) (Section 9.13)
o Current Data Rate (Receive) (Section 9.14)
o Current Data Rate (Transmit) (Section 9.15)
o Latency (Section 9.16)
5. DLEP Session Flow
All DLEP peers transition through four (4) distinct states during the
lifetime of a DLEP session:
o Peer Discovery
o Session Initialization
o In-Session
o Session Termination
The Peer Discovery state is OPTIONAL to implement for routers. If it
is used, this state is the initial state. If it is not used, then
one or more preconfigured address/port combinations SHOULD be
provided to the router, and the device starts in the Session
Initialization state.
Modems MUST support the Peer Discovery state.
5.1. Peer Discovery State
In the Peer Discovery state, routers send UDP packets containing a
Peer Discovery signal (Section 8.1) to the DLEP well-known multicast
address (Section 12.8) and port number (Section 12.7) then await a
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unicast UDP packet containing a Peer Offer signal (Section 8.2) from
a modem. While in the Peer Discovery state, Peer Discovery signals
MUST be sent repeatedly by a router, at regular intervals; every
three (3) seconds is RECOMMENDED.
In the Peer Discovery state, the modem waits for incoming Peer
Discovery signals on the DLEP well-known multicast address and port.
On receipt of a valid signal, it MUST unicast a Peer Offer signal to
the source address of the received UDP packet. Peer Offer signals
MAY contain the unicast address and port for TCP-based communication
with a modem, via the IPv4 Connection Point data item (Section 9.2)
or the IPv6 Connection Point data item (Section 9.3), on which it is
prepared to accept an incoming TCP connection. The modem then begins
listening for incoming TCP connections, and, having accepted one,
enters the Session Initialization state. Anything other than Peer
Discovery signals received on the UDP socket MUST be silently
dropped.
Modems SHOULD be prepared to accept a TCP connection from a router
that is not using the Discovery mechanism, i.e. a connection attempt
that occurs without a preceeding Peer Discovery signal. The modem
MUST accept a TCP connection on only one (1) address/port combination
per session.
Routers MUST use one or more of the modem address/port combinations
from the Peer Offer signal or from a priori configuration to
establish a new TCP connection to the modem. If more than one modem
address/port combinations is available, router implementations MAY
use their own heuristics to determine the order in which they are
tried. If a TCP connection cannot be achieved using any of the
address/port combinations and the Discovery mechanism is in use, then
the router SHOULD resume issuing Peer Discovery signals. If no IP
Connection Point data items are included in the Peer Offer signal,
the router MUST use the origin address of the signal as the IP
address, and the DLEP well-known port number.
Once a TCP connection has been established with the modem, the router
begins a new session and enters the Session Initialization state. It
is up to the router implementation if Peer Discovery signals continue
to be sent after the device has transitioned to the Session
Initialization state.
5.2. Session Initialization State
On entering the Session Initialization state, the router MUST send a
Session Initialization message (Section 8.3) to the modem. The
router MUST then wait for receipt of a Session Initialization
Response message (Section 8.4) from the modem. Receipt of the
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Session Initialization Response message containing a Status data item
(Section 9.1) with value 'Success', see Table 3, indicates that the
modem has received and processed the Session Initialization message,
and the router MUST transition to the In-Session state.
On entering the Session Initialization state, the modem MUST wait for
receipt of a Session Initialization message from the router. Upon
receipt and successful parsing of a Session Initialization message,
the modem MUST send a Session Initialization Response message, and
the session MUST transition to the In-Session state.
As mentioned before, DLEP provides an extension negotiation
capability to be used in the Session Initialization state.
Extensions supported by an implementation MUST be declared to
potential DLEP peers using the Extensions Supported data item
(Section 9.6).
Once both peers have exchanged initialization messages, an
implementation MUST NOT emit any message, signal, data item or status
code associated with an extension that was not specified in the
received initialization message from its peer.
If the router receives any message other than a valid Session
Initialization Response, it MUST send a Session Termination message
(Section 8.7) with a relevant status code, e.g. 'Unexpected
Message', see Table 3, and transition to the Session Termination
state.
If the modem receives any message other than Session Initialization,
or it fails to parse the received message, it MUST NOT send any
message, and MUST terminate the TCP connection, then restart at the
Peer Discovery state.
As mentioned before, the Session Initialization Response message MUST
contain metric data items for ALL metrics that will be used during
the session. If an additional metric is to be introduced after the
session has started, the session between router and modem MUST be
terminated and restarted, and the new metric described in the next
Session Initialization Response message.
5.3. In-Session State
In the In-Session state, messages can flow in both directions between
peers, indicating changes to the session state, the arrival or
departure of reachable destinations, or changes of the state of the
links to the destinations.
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In order to maintain the In-Session state, periodic Heartbeat
messages (Section 8.14) MAY be exchanged between router and modem.
These messages are intended to keep the session alive, and to verify
bidirectional connectivity between the two participants. Each DLEP
peer is responsible for the creation of heartbeat messages. Receipt
of any valid DLEP message MUST reset the heartbeat interval timer
(i.e., valid DLEP messages take the place of, and obviate the need
for, Heartbeat messages).
DLEP provides a Session Update message (Section 8.5), intended to
communicate some change in status (e.g., a change of layer 3 address
parameters, or a modem-wide link change).
In addition to the session messages, the participants will transmit
messages concerning destinations in the network. These messages
trigger creation/maintenance/deletion of destinations in the
information base of the recipient. For example, a modem will inform
its attached router of the presence of a new destination via the
Destination Up message (Section 8.9). Receipt of a Destination Up
causes the router to allocate the necessary resources, creating an
entry in the information base with the specifics (i.e. MAC Address,
Latency, Data Rate, etc.) of the destination. The loss of a
destination is communicated via the Destination Down message
(Section 8.11), and changes in status to the destination (e.g.,
varying link quality, or addressing changes) are communicated via the
Destination Update message (Section 8.13). The information on a
given destination will persist in the router's information base until
(1) a Destination Down message is received, indicating that the modem
has lost contact with the remote node, or (2) the router/modem
transitions to the Session Termination state.
In addition to receiving metrics about the link, DLEP provides a
message allowing a router to request a different datarate, or
latency, from the modem. This message is referred to as the Link
Characteristics Request message (Section 8.15), and gives the router
the ability to deal with requisite increases (or decreases) of
allocated datarate/latency in demand-based schemes in a more
deterministic manner.
The In-Session state is maintained until one of the following
conditions occur:
o The implementation terminates the session by sending a Session
Termination message (Section 8.7)), or
o The DLEP peer terminates the session, indicated by receiving a
Session termination message.
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The implementation MUST then transition to the Session Termination
state.
5.4. Session Termination State
When a DLEP implementation enters the Session Termination state after
sending a Session Termination message (Section 8.7) as the result of
an invalid message or error, it MUST wait for a Session Termination
Response message (Section 8.8) from its peer. If Heartbeat messages
(Section 8.14) are in use, senders SHOULD allow four (4) heartbeat
intervals to expire before assuming that the peer is unresponsive,
and continuing with session termination. If Heartbeat messages are
not in use, then if is RECOMMENDED that an interval of eight (8)
seconds be used.
When a DLEP implementation enters the Session Termination state
having received a Session Termination message from its peer, it MUST
immediately send a Session Termination Response.
The sender and receiver of a Session Termination message MUST release
all resources allocated for the session, and MUST eliminate all
destinations in the information base accessible via the peer
represented by the session. No Destination Down messages
(Section 8.11) are sent.
Any messages received after either sending or receiving a Session
Termination message MUST be silently ignored.
Once Session Termination messages have been exchanged, or timed out,
the device MUST terminate the TCP connection to the peer, and return
to the relevant initial state.
6. DLEP Signal and Message Processing
Most messages in DLEP are members of a request/response pair, e.g.
Destination Up message (Section 8.9), and Destination Up Response
message (Section 8.10). These pairs of messages define an implicit
transaction model for both session messages and destination messages.
As mentioned before, session message pairs control the flow of the
session through the various states, e.g. an implementation MUST NOT
leave the Session Initialization state until a Session Initialization
message (Section 8.3) and Session Initialization Response message
(Section 8.4) have been exchanged.
Destination message pairs describe the arrival and departure of
logical destinations, and control the flow of information about the
destinations in the several ways.
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Prior to the exchange of a pair of Destination Up and Destination Up
Response messages, no messages concerning the logical destination
identified by the MAC Address data item (Section 9.7) may be sent.
An implementation receiving a message with such an unannounced
destination MUST terminate the session by issuing a Session
Termination message (Section 8.7) with a status code of 'Invalid
Destination', see Table 3, and transition to the Session Termination
state.
The receiver of a Destination Up message MAY decline further messages
concerning a given destination by sending a Destination Up Response
with a status code of 'Not Interested', see Table 3. Receivers of
such responses MUST NOT send further messages concerning that
destination to the peer.
After exchanging a pair of Destination Down (Section 8.11) and
Destination Down Response (Section 8.12) messages, no messages
concerning the logical destination identified by the MAC Address data
item may be a sent without a previously sending a new Destination Up
message. An implementation receiving a message about a down
destination MUST terminate the session by issuing a Session
Termination message with a status code of 'Invalid Destination' and
transition to the Session Termination state.
7. DLEP Signal and Message Structure
DLEP defines two protocol units used in two different ways: Signals
and Messages. Signals are only used in the Discovery mechanism and
are carried in UDP datagrams. Messages are used bi-directionally
over a TCP connection between two peers, in the Session
Initialization, In-Session and Session Termination states.
Both signals and messages consist of a header followed by an
unordered list of data items. Headers consist of Type and Length
information, while data items are encoded as TLV (Type-Length-Value)
structures. In this document, the data items following a signal or
message header are described as being 'contained in' the signal or
message.
There is no restriction on the order of data items following a
header, and the multiplicity of duplicate data items is defined by
the definition of the signal or message declared by the type in the
header.
All integers in header fields and values MUST be in network byte-
order.
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7.1. DLEP Signal Header
The DLEP signal header contains the following fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 'D' | 'L' | 'E' | 'P' |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Signal Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: DLEP Signal Header
"DLEP": Every signal MUST start with the characters: U+44, U+4C,
U+45, U+50.
Signal Type: An 16-bit unsigned integer containing one of the DLEP
Signal/Message Type values defined in this document.
Length: The length in octets, expressed as a 16-bit unsigned
integer, of all of the DLEP data items associated with this
signal. This length SHALL NOT include the length of the header
itself.
The DLEP signal header is immediately followed by one or more DLEP
data items, encoded in TLVs, as defined in this document.
If an unrecognized, or unexpected signal is received, or a received
signal contains unrecognized, invalid, or disallowed duplicate data
items, the receiving peer MUST ignore the signal.
7.2. DLEP Message Header
The DLEP message header contains the following fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: DLEP Message Header
Message Type: An 16-bit unsigned integer containing one of the DLEP
Signal/Message Type values defined in this document.
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Length: The length in octets, expressed as a 16-bit unsigned
integer, of all of the DLEP data items associated with this
message. This length SHALL NOT include the length of the header
itself.
The DLEP message header is immediately followed by one or more DLEP
data items, encoded in TLVs, as defined in this document.
If an unrecognized, or unexpected message is received, or a received
message contains unrecognized, invalid, or disallowed duplicate data
items, the receiving peer MUST issue a Session Termination message
(Section 8.7) with a Status data item (Section 9.1) containing the
most relevant status code, and transition to the Session Termination
state.
7.3. DLEP Generic Data Item
All DLEP data items contain the following fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value... :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: DLEP Generic Data Item
Data Item Type: An 16-bit unsigned integer field specifying the type
of data item being sent.
Length: The length in octets, expressed as an 16-bit unsigned
integer, of the value field of the data item. This length SHALL
NOT include the length of the header itself.
Value: A field of <Length> octets, which contains data specific to a
particular data item.
8. DLEP Signals and Messages
As mentioned above, all DLEP signals begin with the DLEP signal
header, and all DLEP messages begin with the DLEP message header.
Therefore, in the following descriptions of specific signals and
messages, this header is assumed, and will not be replicated.
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Following is the set of core signals and messages that MUST be
recognized by a DLEP compliant implementation. As mentioned before,
not all messages may be used during a session, but an implementation
MUST correctly process these messages when received.
The core DLEP signals and messages are:
+-------------+-----------------------------------------------------+
| Type Code | Description |
+-------------+-----------------------------------------------------+
| 0 | Reserved |
| 1 | Peer Discovery signal (Section 8.1) |
| 2 | Peer Offer signal (Section 8.2) |
| 3 | Session Initialization message (Section 8.3) |
| 4 | Session Initialization Response message (Section |
| | 8.4) |
| 5 | Session Update message (Section 8.5) |
| 6 | Session Update Response message (Section 8.6) |
| 7 | Session Termination message (Section 8.7) |
| 8 | Session Termination Response message (Section 8.8) |
| 9 | Destination Up message (Section 8.9) |
| 10 | Destination Up Response message (Section 8.10) |
| 11 | Destination Down message (Section 8.11) |
| 12 | Destination Down Response message (Section 8.12) |
| 13 | Destination Update message (Section 8.13) |
| 14 | Heartbeat message (Section 8.14) |
| 15 | Link Characteristics Request message (Section 8.15) |
| 16 | Link Characteristics Response message (Section |
| | 8.16) |
| 17-65519 | Reserved for future extensions |
| 65520-65534 | Private Use. Available for experiments |
| 65535 | Reserved |
+-------------+-----------------------------------------------------+
Table 1: DLEP Signal/Message types
8.1. Peer Discovery Signal
A Peer Discovery signal SHOULD be sent by a router to discover DLEP
modems in the network. The Peer Offer signal (Section 8.2) is
required to complete the discovery process. Implementations MAY
implement their own retry heuristics in cases where it is determined
the Peer Discovery signal has timed out.
To construct a Peer Discovery signal, the Signal Type value in the
signal header is set to 1, from Table 1.
The Peer Discovery signal MAY contain the following data item:
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o Peer Type (Section 9.4)
8.2. Peer Offer Signal
A Peer Offer signal MUST be sent by a DLEP modem in response to a
valid Peer Discovery signal (Section 8.1).
The Peer Offer signal MUST be sent to the unicast address of the
originator of the Peer Discovery signal.
To construct a Peer Offer signal, the Signal Type value in the signal
header is set to 2, from Table 1.
The Peer Offer signal MAY contain the following data item:
o Peer Type (Section 9.4)
The Peer Offer signal MAY contain one or more of any of the following
data items, with different values:
o IPv4 Connection Point (Section 9.2)
o IPv6 Connection Point (Section 9.3)
The IP Connection Point data items indicate the unicast address the
receiver of Peer Offer MUST use when connecting the DLEP TCP session.
If multiple IP Connection Point data items are present in the Peer
Offer signal, implementations MAY use their own heuristics to select
the address to connect to. If no IP Connection Point data items are
included in the Peer Offer signal, the receiver MUST use the origin
address of the signal as the IP address, and the DLEP well-known port
number (Section 12.7) to establish the TCP connection.
8.3. Session Initialization Message
A Session Initialization message MUST be sent by a router as the
first message of the DLEP TCP session. It is sent by the router
after a TCP connect to an address/port combination that was obtained
either via receipt of a Peer Offer, or from a priori configuration.
If any optional extensions are supported by the implementation, they
MUST be enumerated in the Extensions Supported data item. If an
Extensions Supported data item does not exist in a Session
Initialization message, the receiver of the message MUST conclude
that there is no support for extensions in the sender.
Implementations supporting the Heartbeat Interval (Section 9.5)
should understand that heartbeats are not fully established until
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receipt of Session Initialization Response message (Section 8.4), and
should therefore implement their own timeout and retry heuristics for
this message.
To construct a Session Initialization message, the Message Type value
in the message header is set to 3, from Table 1.
The Session Initialization message MUST contain one of each of the
following data items:
o Heartbeat Interval (Section 9.5)
The Session Initialization message MAY contain one of each of the
following data items:
o Peer Type (Section 9.4)
o Extensions Supported (Section 9.6)
A Session Initialization message MUST be acknowledged by the receiver
issuing a Session Initialization Response message (Section 8.4).
8.4. Session Initialization Response Message
A Session Initialization Response message MUST be sent in response to
a received Session Initialization message (Section 8.3). The Session
Initialization Response message completes the DLEP session
establishment; the sender of the message should transition to the In-
Session state when the message is sent, and the receiver should
transition to the In-Session state upon receipt (and successful
parsing) of an acceptable Session Initialization Response message.
All supported metric data items MUST be included in the Session
Initialization Response message, with default values to be used on a
'modem-wide' basis. This can be viewed as the modem 'declaring' all
supported metrics at DLEP session initialization. Receipt of any
DLEP message containing a metric data item not included in the
Session Initialization Response message MUST be treated as an error,
resulting in the termination of the DLEP session between router and
modem.
If any optional extensions are supported by the modem, they MUST be
enumerated in the Extensions Supported data item. If an Extensions
Supported data item does not exist in a Session Initialization
Response message, the receiver of the message MUST conclude that
there is no support for extensions in the sender.
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After the Session Initialization/Session Initialization Response
messages have been successfully exchanged, implementations MUST only
use extensions that are supported by BOTH peers.
To construct a Session Initialization Response message, the Message
Type value in the message header is set to 4, from Table 1.
The Session Initialization Response message MUST contain one of each
of the following data items:
o Heartbeat Interval (Section 9.5)
o Maximum Data Rate (Receive) (Section 9.12)
o Maximum Data Rate (Transmit) (Section 9.13)
o Current Data Rate (Receive) (Section 9.14)
o Current Data Rate (Transmit) (Section 9.15)
o Latency (Section 9.16)
The Session Initialization Response message MUST contain one of each
of the following data items, if the data item will be used during the
lifetime of the session:
o Resources (Receive) (Section 9.17)
o Resources (Transmit) (Section 9.18)
o Relative Link Quality (Receive) (Section 9.19)
o Relative Link Quality (Transmit) (Section 9.20)
The Session Initialization Response message MAY contain one of each
of the following data items:
o Status (Section 9.1)
o Peer Type (Section 9.4)
o Extensions Supported (Section 9.6)
A receiver of a Session Initialization Response message without a
Status data item MUST behave as if a Status data item with code
'Success' had been received.
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8.5. Session Update Message
A Session Update message MAY be sent by a DLEP peer to indicate local
Layer 3 address changes, or metric changes on a modem-wide basis.
For example, addition of an IPv4 address to the router MAY prompt a
Session Update message to its attached DLEP modems. Also, for
example, a modem that changes its Maximum Data Rate (Receive) for all
destinations MAY reflect that change via a Session Update message to
its attached router(s).
Concerning Layer 3 addresses, if the modem is capable of
understanding and forwarding this information (via proprietary
mechanisms), the address update would prompt any remote DLEP modems
(DLEP-enabled modems in a remote node) to issue a Destination Update
message (Section 8.13) to their local routers with the new (or
deleted) addresses. Modems that do not track Layer 3 addresses
SHOULD silently parse and ignore Layer 3 data items. The Session
Update message MUST be acknowledged with a Session Update Response
message (Section 8.6).
If metrics are supplied with the Session Update message (e.g.,
Maximum Data Rate), these metrics are considered to be modem-wide,
and therefore MUST be applied to all destinations in the information
base associated with the router/modem session.
Supporting implementations are free to employ heuristics to
retransmit Session Update messages. The sending of Session Update
messages for Layer 3 address changes SHOULD cease when either
participant (router or modem) determines that the other
implementation does not support Layer 3 address tracking.
To construct a Session Update message, the Message Type value in the
message header is set to 5, from Table 1.
The Session Update message MAY contain one of each of the following
data items:
o Maximum Data Rate (Receive) (Section 9.12)
o Maximum Data Rate (Transmit) (Section 9.13)
o Current Data Rate (Receive) (Section 9.14)
o Current Data Rate (Transmit) (Section 9.15)
o Latency (Section 9.16)
o Resources (Receive) (Section 9.17)
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o Resources (Transmit) (Section 9.18)
o Relative Link Quality (Receive) (Section 9.19)
o Relative Link Quality (Transmit) (Section 9.20)
The Session Update message MAY contain one or more of the following
data items, with different values:
o IPv4 Address (Section 9.8)
o IPv6 Address (Section 9.9)
A Session Update message MUST be acknowledged by the receiver issuing
a Session Update Response message (Section 8.6).
8.6. Session Update Response Message
A Session Update Response message MUST be sent by implementations to
indicate whether a Session Update message (Section 8.5) was
successfully received.
To construct a Session Update Response message, the Message Type
value in the message header is set to 6, from Table 1.
The Session Update Response message MAY contain one of each of the
following data items:
o Status (Section 9.1)
A receiver of a Session Update Response message without a Status data
item MUST behave as if a Status data item with code 'Success' had
been received.
8.7. Session Termination Message
A Session Termination message MUST be sent by a DLEP participant when
the router/modem session needs to be terminated.
To construct a Session Termination message, the Message Type value in
the message header is set to 7, from Table 1.
The Session Termination message MAY contain one of each of the
following data items:
o Status (Section 9.1)
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A receiver of a Session Termination message without a Status data
item MUST behave as if a Status of 'Unknown reason for Session
Termination' has been received.
A Session Termination message MUST be acknowledged by the receiver
issuing a Session Termination Response message (Section 8.8).
8.8. Session Termination Response Message
A Session Termination Response message MUST be sent by a DLEP peer in
response to a received Session Termination message (Section 8.7).
Receipt of a Session Termination Response message completes the
teardown of the router/modem session.
To construct a Session Termination Response message, the Message Type
value in the message header is set to 8, from Table 1.
The Session Termination Response message MAY contain one of each of
the following data items:
o Status (Section 9.1)
A receiver of a Session Termination Response message without a Status
data item MUST behave as if a Status data item with status code
'Success', implying graceful termination, had been received.
8.9. Destination Up Message
A Destination Up message can be sent either by the modem, to indicate
that a new remote node has been detected, or by the router, to
indicate the presence of a new logical destination (e.g., a Multicast
group) in the network.
A Destination Up message MUST be acknowledged by the receiver issuing
a Destination Up Response message (Section 8.10). The sender of the
Destination Up message is free to define its retry heuristics in
event of a timeout. When a Destination Up message is received and
successfully processed, the receiver should add knowledge of the new
destination to its information base, indicating that the destination
is accessible via the modem/router pair.
To construct a Destination Up message, the Message Type value in the
message header is set to 9, from Table 1.
The Destination Up message MUST contain one of each of the following
data items:
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o MAC Address (Section 9.7)
The Destination Up message MAY contain one of each of the following
data items:
o Maximum Data Rate (Receive) (Section 9.12)
o Maximum Data Rate (Transmit) (Section 9.13)
o Current Data Rate (Receive) (Section 9.14)
o Current Data Rate (Transmit) (Section 9.15)
o Latency (Section 9.16)
o Resources (Receive) (Section 9.17)
o Resources (Transmit) (Section 9.18)
o Relative Link Quality (Receive) (Section 9.19)
o Relative Link Quality (Transmit) (Section 9.20)
The Destination Up message MAY contain one or more of the following
data items, with different values:
o IPv4 Address (Section 9.8)
o IPv6 Address (Section 9.9)
o IPv4 Attached Subnet (Section 9.10)
o IPv6 Attached Subnet (Section 9.11)
If the sender has IPv4 and/or IPv6 address information for a
destination it SHOULD include the relevant data items in the
Destination Up message, reducing the need for the receiver to probe
for any address.
8.10. Destination Up Response Message
A DLEP participant MUST send a Destination Up Response message to
indicate whether a Destination Up message (Section 8.9) was
successfully processed.
To construct a Destination Up Response message, the Message Type
value in the message header is set to 10, from Table 1.
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The Destination Up Response message MUST contain one of each of the
following data items:
o MAC Address (Section 9.7)
The Destination Up Response message MAY contain one of each of the
following data items:
o Status (Section 9.1)
A receiver of a Destination Up Response message without a Status data
item MUST behave as if a Status data item with status code 'Success'
had been received.
8.11. Destination Down Message
A DLEP peer MUST send a Destination Down message to report when a
destination (a remote node or a multicast group) is no longer
reachable. A Destination Down Response message (Section 8.12) MUST
be sent by the recipient of a Destination Down message to confirm
that the relevant data has been removed from the information base.
The sender of the Destination Down message is free to define its
retry heuristics in event of a timeout.
To construct a Destination Down message, the Message Type value in
the message header is set to 11, from Table 1.
The Destination Down message MUST contain one of each of the
following data items:
o MAC Address (Section 9.7)
8.12. Destination Down Response Message
A DLEP participant MUST send a Destination Down Response message to
indicate whether a received Destination Down message (Section 8.11)
was successfully processed. If successfully processed, the sender of
the Response MUST have removed all entries in the information base
that pertain to the referenced destination.
To construct a Destination Down Response message, the Message Type
value in the message header is set to 12, from Table 1.
The Destination Down Response message MUST contain one of each of the
following data items:
o MAC Address (Section 9.7)
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The Destination Down Response message MAY contain one of each of the
following data items:
o Status (Section 9.1)
A receiver of a Destination Down Response message without a Status
data item MUST behave as if a Status data item with status code
'Success' had been received.
8.13. Destination Update Message
A DLEP participant SHOULD send the Destination Update message when it
detects some change in the information base for a given destination
(remote node or multicast group). Some examples of changes that
would prompt a Destination Update message are:
o Change in link metrics (e.g., Data Rates)
o Layer 3 addressing change
To construct a Destination Update message, the Message Type value in
the message header is set to 13, from Table 1.
The Destination Update message MUST contain one of each of the
following data items:
o MAC Address (Section 9.7)
The Destination Update message MAY contain one of each of the
following data items:
o Maximum Data Rate (Receive) (Section 9.12)
o Maximum Data Rate (Transmit) (Section 9.13)
o Current Data Rate (Receive) (Section 9.14)
o Current Data Rate (Transmit) (Section 9.15)
o Latency (Section 9.16)
o Resources (Receive) (Section 9.17)
o Resources (Transmit) (Section 9.18)
o Relative Link Quality (Receive) (Section 9.19)
o Relative Link Quality (Transmit) (Section 9.20)
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The Destination Update message MAY contain one or more of the
following data items, with different values:
o IPv4 Address (Section 9.8)
o IPv6 Address (Section 9.9)
8.14. Heartbeat Message
A Heartbeat message SHOULD be sent by a DLEP participant every N
seconds, where N is defined in the Heartbeat Interval data item of
the Session Initialization message (Section 8.3) or Session
Initialization Response message (Section 8.4).
Note that implementations setting the Heartbeat Interval to 0
effectively sets the interval to an infinite value, therefore this
message SHOULD NOT be sent.
The message is used by participants to detect when a DLEP session
partner (either the modem or the router) is no longer communicating.
Participants SHOULD allow two (2) heartbeat intervals to expire with
no traffic on the router/modem session before initiating DLEP session
termination procedures.
To construct a Heartbeat message, the Message Type value in the
message header is set to 14, from Table 1.
There are no valid data items for the Heartbeat message.
8.15. Link Characteristics Request Message
The Link Characteristics Request message MAY be sent by the router to
request that the modem initiate changes for specific characteristics
of the link. The request can reference either a real destination
(e.g., a remote node), or a logical destination (e.g., a multicast
group) within the network.
The Link Characteristics Request message MAY contain either a Current
Data Rate (CDRR or CDRT) data item to request a different datarate
than what is currently allocated, a Latency data item to request that
traffic delay on the link not exceed the specified value, or both. A
Link Characteristics Response message (Section 8.16) is required to
complete the request. Issuing a Link Characteristics Request with
ONLY the MAC Address data item is a mechanism a peer MAY use to
request metrics (via the Link Characteristics Response) from its
partner.
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The sender of a Link Characteristics Request message MAY attach a
timer to the request using the Link Characteristics Response Timer
data item. If a Link Characteristics Response message is received
after the timer expires, the sender MUST NOT assume that the request
succeeded. Implementations are free to define their retry heuristics
in event of a timeout.
To construct a Link Characteristics Request message, the Message Type
value in the message header is set to 15, from Table 1.
The Link Characteristics Request message MUST contain one of each of
the following data items:
o MAC Address (Section 9.7)
The Link Characteristics Request message MAY contain one of each of
the following data items:
o Link Characteristics Response Timer (Section 9.21)
o Current Data Rate (Receive) (Section 9.14)
o Current Data Rate (Transmit) (Section 9.15)
o Latency (Section 9.16)
8.16. Link Characteristics Response Message
A DLEP participant MUST send a Link Characteristics Response message
to indicate whether a received Link Characteristics Request message
(Section 8.15) was successfully processed. The Link Characteristics
Response message SHOULD contain a complete set of metric data items,
and MUST contain a full set (i.e. those declared in the Session
Initialization Response message (Section 8.4)), if metrics were
requested by only including a MAC address data item. It MUST contain
the same metric types as the request. The values in the metric data
items in the Link Characteristics Response message MUST reflect the
link characteristics after the request has been processed.
If an implementation is not able to alter the characteristics of the
link in the manner requested, then a Status data item with status
code 'Request Denied', see Table 3, MUST be added to the message.
To construct a Link Characteristics Response message, the Message
Type value in the message header is set to 16, from Table 1.
The Link Characteristics Response message MUST contain one of each of
the following data items:
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o MAC Address (Section 9.7)
The Link Characteristics Response message SHOULD contain one of each
of the following data items:
o Maximum Data Rate (Receive) (Section 9.12)
o Maximum Data Rate (Transmit) (Section 9.13)
o Current Data Rate (Receive) (Section 9.14)
o Current Data Rate (Transmit) (Section 9.15)
o Latency (Section 9.16)
The Link Characteristics Response message MAY contain one of each of
the following data items:
o Resources (Receive) (Section 9.17)
o Resources (Transmit) (Section 9.18)
o Relative Link Quality (Receive) (Section 9.19)
o Relative Link Quality (Transmit) (Section 9.20)
o Status (Section 9.1)
A receiver of a Link Characteristics Response message without a
Status data item MUST behave as if a Status data item with status
code 'Success' had been received.
9. DLEP Data Items
Following is the list of core data items that MUST be recognized by a
DLEP compliant implementation. As mentioned before, not all data
items need be used during a session, but an implementation MUST
correctly process these data items when correctly associated with a
signal or message.
The core DLEP data items are:
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+-------------+-----------------------------------------------------+
| Type Code | Description |
+-------------+-----------------------------------------------------+
| 0 | Reserved |
| 1 | Status (Section 9.1) |
| 2 | IPv4 Connection Point (Section 9.2) |
| 3 | IPv6 Connection Point (Section 9.3) |
| 4 | Peer Type (Section 9.4) |
| 5 | Heartbeat Interval (Section 9.5) |
| 6 | Extensions Supported (Section 9.6) |
| 7 | MAC Address (Section 9.7) |
| 8 | IPv4 Address (Section 9.8) |
| 9 | IPv6 Address (Section 9.9) |
| 10 | IPv4 Attached Subnet (Section 9.10) |
| 11 | IPv6 Attached Subnet (Section 9.11) |
| 12 | Maximum Data Rate (Receive) MDRR) (Section 9.12) |
| 13 | Maximum Data Rate (Transmit) (MDRT) (Section 9.13) |
| 14 | Current Data Rate (Receive) (CDRR) (Section 9.14) |
| 15 | Current Data Rate (Transmit) (CDRT) (Section 9.15) |
| 16 | Latency (Section 9.16) |
| 17 | Resources (Receive) (RESR) (Section 9.17) |
| 18 | Resources (Transmit) (REST) (Section 9.18) |
| 19 | Relative Link Quality (Receive) (RLQR) (Section |
| | 9.19) |
| 20 | Relative Link Quality (Transmit) (RLQT) (Section |
| | 9.20) |
| 21 | Link Characteristics Response Timer (Section 9.21) |
| 22-24 | Credit Windowing (Section 10) extension data items |
| 25-65407 | Reserved for future extensions |
| 65408-65534 | Private Use. Available for experiments |
| 65535 | Reserved |
+-------------+-----------------------------------------------------+
Table 2: DLEP Data Item types
9.1. Status
The Status data item MAY appear in the Session Initialization
Response (Section 8.4), Session Termination (Section 8.7), Session
Termination Response (Section 8.8), Session Update Response
(Section 8.6), Destination Up Response (Section 8.10), Destination
Down Response (Section 8.12) and Link Characteristics Response
(Section 8.16) messages.
For the Session Termination message (Section 8.7), the Status data
item indicates a reason for the termination. For all acknowledgement
messages, the Status data item is used to indicate the success or
failure of the previously received message.
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The status data item includes an optional Text field that can be used
to provide a textual description of the status. The use of the Text
field is entirely up to the receiving implementation, i.e., it could
be output to a log file or discarded. If no Text field is supplied
with the Status data item, the Length field MUST be set to 1.
The Status data item contains the following fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Text... :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 1 + Length of text, in octets
Status Code: One of the codes defined in Table 3 below.
Text: UTF-8 encoded string, describing the cause, used for
implementation defined purposes. Since this field is used for
description, implementations SHOULD limit characters in this field
to printable characters. Implementations receiving this data item
SHOULD check for printable characters in the field.
An implementation MUST NOT assume the Text field is NUL-terminated.
+-------------+---------+-----------+-------------------------------+
| Status Code | Value | Failure | Reason |
| | | Mode | |
+-------------+---------+-----------+-------------------------------+
| Success | 0 | Success | The message was processed |
| | | | successfully. |
| Unknown | 1 | Terminate | The message was not |
| Message | | | recognized by the |
| | | | implementation. |
| Unexpected | 2 | Terminate | The message was not expected |
| Message | | | while the device was in the |
| | | | current state, e.g., a |
| | | | Session Initialization |
| | | | message (Section 8.3) in the |
| | | | In-Session state. |
| Invalid | 3 | Terminate | One or more data items in the |
| Data | | | message are invalid, |
| | | | unexpected or incorrectly |
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| | | | duplicated. |
| Invalid | 4 | Terminate | The destination provided in |
| Destination | | | the message does not match a |
| | | | previously announced |
| | | | destination. For example, in |
| | | | the Link Characteristic |
| | | | Response message (Section |
| | | | 8.16). |
| <Reserved> | 5-90 | Terminate | Reserved for future |
| | | | extensions. |
| <Private | 91-99 | Terminate | Available for experiments. |
| Use> | | | |
| Not | 100 | Continue | The receiver is not |
| Interested | | | interested in this message |
| | | | subject, e.g. a Destination |
| | | | Up Response message (Section |
| | | | 8.10) to indicate no further |
| | | | messages about the |
| | | | destination. |
| Request | 101 | Continue | The receiver refuses to |
| Denied | | | complete the request. |
| Timed Out | 102 | Continue | The operation could not be |
| | | | completed in the time |
| | | | allowed. |
| <Reserved> | 103-243 | Continue | Reserved for future |
| | | | extensions. |
| <Private | 244-254 | Continue | Available for experiments. |
| Use> | | | |
| <Reserved> | 255 | Terminate | Reserved. |
+-------------+---------+-----------+-------------------------------+
Table 3: DLEP Status Codes
A failure mode of 'Terminate' indicates that the session MUST be
terminated after sending a response containing the status code. A
failure mode of 'Continue' indicates that the session SHOULD continue
as normal.
9.2. IPv4 Connection Point
The IPv4 Connection Point data item MAY appear in the Peer Offer
signal (Section 8.2).
The IPv4 Connection Point data item indicates the IPv4 address and,
optionally, the TCP port number on the DLEP modem available for
connections. If provided, the receiver MUST use this information to
perform the TCP connect to the DLEP server.
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TCP Port Number (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 4 (or 6 if TCP Port included)
IPv4 Address: The IPv4 address listening on the DLEP modem.
TCP Port Number: TCP Port number on the DLEP modem.
If the Length field is 6, 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 4, the receiver MUST use the DLEP well-known port
number (Section 12.7) to establish the TCP connection.
9.3. IPv6 Connection Point
The IPv6 Connection Point data item MAY appear in the Peer Offer
signal (Section 8.2).
The IPv6 Connection Point data item indicates the IPv6 address and,
optionally, the TCP port number on the DLEP modem available for
connections. If provided, the receiver MUST use this information to
perform the TCP connect to the DLEP server.
The IPv6 Connection Point data item contains the following fields:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Address :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Address :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Address :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Address :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TCP Port Number (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 16 (or 18 if TCP Port included)
IPv6 Address: The IPv6 address listening on the DLEP modem.
TCP Port Number: TCP Port number on the DLEP modem.
If the Length field is 18, 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 16, the receiver MUST use the DLEP well-known
port number (Section 12.7) to establish the TCP connection.
9.4. Peer Type
The Peer Type data item MAY appear in the Peer Discovery
(Section 8.1) and Peer Offer (Section 8.2) signals, and the Session
Initialization (Section 8.3) and Session Initialization Response
(Section 8.4) messages.
The Peer Type data item is used by the router and modem to give
additional information as to its type. The peer type is a string and
is envisioned to be used for informational purposes (e.g., as output
in a display command).
The Peer Type data item contains the following fields:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Peer Type... :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: Length of peer type string, in octets.
Peer Type: UTF-8 encoded string. For example, a satellite modem
might set this variable to "Satellite terminal". Since this data
item is intended to provide additional information for display
commands, sending implementations SHOULD limit the data to
printable characters, and receiving implmentations SHOULD check
the data for printable characters.
An implementation MUST NOT assume the Peer Type field is NUL-
terminated.
9.5. Heartbeat Interval
The Heartbeat Interval data item MUST appear in both the Session
Initialization (Section 8.3) and Session Initialization Response
(Section 8.4) messages to indicate the Heartbeat timeout window to be
used by the sender.
The Interval is used to specify a period (in seconds) for Heartbeat
messages (Section 8.14). By specifying an Interval value of 0,
implementations MAY indicate the desire to disable Heartbeat messages
entirely (i.e., the Interval is set to an infinite value). However,
it is RECOMMENDED that implementations use non-0 timer values.
The Heartbeat Interval data item contains the following fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 2
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Interval: 0 = Do not use heartbeats on this DLEP session. Non-zero
= Interval, in seconds, for heartbeat messages.
9.6. Extensions Supported
The Extensions Supported data item MAY be used in both the Session
Initialization (Section 8.3) and Session Initialization Response
(Section 8.4) messages.
The Extensions Supported data item is used by the router and modem to
negotiate additional optional functionality they are willing to
support. The Extensions List is a concatenation of the types of each
supported extension, found in the IANA DLEP Extensions repository.
Each Extension Type definition includes which additional signals and
data-items are supported.
The Extensions Supported data item contains the following fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extensions List...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: Length of the extensions list in octets. This is twice (2x)
the number of extensions.
Extension List: A list of extensions supported, identified by their
2-octet value as listed in the extensions registry.
9.7. MAC Address
The MAC address data item MUST appear in all destination-oriented
messages (i.e., Destination Up (Section 8.9), Destination Up Response
(Section 8.10), Destination Down (Section 8.11), Destination Down
Response (Section 8.12), Destination Update (Section 8.13), Link
Characteristics Request (Section 8.15), and Link Characteristics
Response (Section 8.16)).
The MAC Address data item contains the address of the destination on
the remote node. The MAC address MAY be either a physical or a
virtual destination, and MAY be expressed in EUI-48 or EUI-64 format.
Examples of a virtual destination would be a multicast MAC address,
or the broadcast MAC (FF:FF:FF:FF:FF:FF).
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: MAC Address :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: MAC Address : (if EUI-64 used) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 6 for EUI-48 format, or 8 for EUI-64 format
MAC Address: MAC Address of the destination.
9.8. IPv4 Address
The IPv4 Address data item MAY appear in the Session Update
(Section 8.5), Destination Up (Section 8.9) and Destination Update
(Section 8.13) messages.
When included in Destination messages, this data item contains the
IPv4 address of the destination. When included in the Session Update
message, this data item contains the IPv4 address of the peer. In
either case, the data item also contains an indication of whether
this is a new or existing address, or is a deletion of a previously
known address.
The IPv4 Address data item contains the following fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Add/Drop | IPv4 Address :
| Indicator | :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv4 |
: Address |
+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 5
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Add/Drop: Value indicating whether this is a new or existing address
(1), or a withdrawal of an address (0). Values other than 0 or 1
MUST be considered as invalid.
IPv4 Address: The IPv4 address of the destination or peer.
9.9. IPv6 Address
The IPv6 Address data item MAY appear in the Session Update
(Section 8.5), Destination Up (Section 8.9) and Destination Update
(Section 8.13) messages. When included in Destination messages, this
data item contains the IPv6 address of the destination. When
included in the Session Update message, this data item contains the
IPv6 address of the peer. In either case, the data item also
contains an indication of whether this is a new or existing address,
or is a deletion of a previously known address.
The IPv6 Address data item contains the following fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Add/Drop | IPv6 Address :
| Indicator | :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Address :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Address :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Address :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Address |
+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 17
Add/Drop: Value indicating whether this is a new or existing address
(1), or a withdrawal of an address (0). Values other than 0 or 1
MUST be considered as invalid.
IPv6 Address: IPv6 Address of the destination or peer.
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9.10. IPv4 Attached Subnet
The DLEP IPv4 Attached Subnet allows a device to declare that it has
an IPv4 subnet (e.g., a stub network) attached, or that it has become
aware of an IPv4 subnet being present at a remote destination. The
IPv4 Attached Subnet data item MAY appear in the Destination Up
(Section 8.9) message. Once an IPv4 Subnet has been declared on a
device, the declaration SHALL NOT be withdrawn without withdrawing
the destination (via the Destination Down message (Section 8.11)) and
re-issuing the Destination Up message.
The DLEP IPv4 Attached Subnet data item contains the following
fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Attached Subnet |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Len. |
+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 5
IPv4 Subnet: The IPv4 subnet reachable at the destination.
Prefix Length: Length of the prefix (1-32) for the IPv4 subnet. A
prefix length outside the speficied range MUST be considered as
invalid.
9.11. IPv6 Attached Subnet
The DLEP IPv6 Attached Subnet allows a device to declare that it has
an IPv6 subnet (e.g., a stub network) attached, or that it has become
aware of an IPv6 subnet being present at a remote destination. The
IPv6 Attached Subnet data item MAY appear in the Destination Up
(Section 8.9) message. As in the case of the IPv4 attached Subnet
data item above, once an IPv6 attached subnet has been declared, it
SHALL NOT be withdrawn without withdrawing the destination (via the
Destination Down message (Section 8.11)) and re-issuing the
Destination Up message.
The DLEP IPv6 Attached Subnet data item contains the following
fields:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Attached Subnet :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Attached Subnet :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Attached Subnet :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: IPv6 Attached Subnet |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Len. |
+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 17
IPv4 Subnet: The IPv6 subnet reachable at the destination.
Prefix Length: Length of the prefix (1-128) for the IPv6 subnet. A
prefix length outside the specified range MUST be considered as
invalid.
9.12. Maximum Data Rate (Receive)
The Maximum Data Rate (Receive) (MDRR) data item MUST appear in the
Session Initialization Response message (Section 8.4), and MAY appear
in the Session Update (Section 8.5), Destination Up (Section 8.9),
Destination Update (Section 8.13) and Link Characteristics Response
(Section 8.16) messages to indicate the maximum theoretical data
rate, in bits per second, that can be achieved while receiving data
on the link.
The Maximum Data Rate (Receive) data item contains the following
fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MDRR (bps) :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: MDRR (bps) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Data Item Type: TBD
Length: 8
Maximum Data Rate (Receive): A 64-bit unsigned integer, representing
the maximum theoretical data rate, in bits per second (bps), that
can be achieved while receiving on the link.
9.13. Maximum Data Rate (Transmit)
The Maximum Data Rate (Transmit) (MDRT) data item MUST appear in the
Session Initialization Response message (Section 8.4), and MAY appear
in the Session Update (Section 8.5), Destination Up (Section 8.9),
Destination Update (Section 8.13) and Link Characteristics Response
(Section 8.16) messages to indicate the maximum theoretical data
rate, in bits per second, that can be achieved while transmitting
data on the link.
The Maximum Data Rate (Transmit) data item contains the following
fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MDRT (bps) :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: MDRT (bps) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 8
Maximum Data Rate (Transmit): A 64-bit unsigned integer,
representing the maximum theoretical data rate, in bits per second
(bps), that can be achieved while transmitting on the link.
9.14. Current Data Rate (Receive)
The Current Data Rate (Receive) (CDRR) data item MUST appear in the
Session Initialization Response message (Section 8.4), and MAY appear
in the Session Update (Section 8.5), Destination Up (Section 8.9),
Destination Update (Section 8.13) and Link Characteristics Response
(Section 8.16) messages to indicate the rate at which the link is
currently operating for receiving traffic.
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When used in the Link Characteristics Request message (Section 8.15),
CDRR represents the desired receive rate, in bits per second, on the
link.
The Current Data Rate (Receive) data item contains the following
fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CDRR (bps) :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: CDRR (bps) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 8
Current Data Rate (Receive): A 64-bit unsigned integer, representing
the current data rate, in bits per second, that can currently be
achieved while receiving traffic on the link.
If there is no distinction between current and maximum receive data
rates, current data rate receive MUST be set equal to the maximum
data rate receive.
9.15. Current Data Rate (Transmit)
The Current Data Rate Transmit (CDRT) data item MUST appear in the
Session Initialization Response message (Section 8.4), and MAY appear
in the Session Update (Section 8.5), Destination Up (Section 8.9),
Destination Update (Section 8.13), and Link Characteristics Response
(Section 8.16) messages to indicate the rate at which the link is
currently operating for transmitting traffic.
When used in the Link Characteristics Request message (Section 8.15),
CDRT represents the desired transmit rate, in bits per second, on the
link.
The Current Data Rate (Transmit) data item contains the following
fields:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CDRT (bps) :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: CDRT (bps) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 8
Current Data Rate (Transmit): A 64-bit unsigned integer,
representing the current data rate, in bits per second, that can
currently be achieved while transmitting traffic on the link.
If there is no distinction between current and maximum transmit data
rates, current data rate transmit MUST be set equal to the maximum
data rate transmit.
9.16. Latency
The Latency data item MUST appear in the Session Initialization
Response message (Section 8.4), and MAY appear in the Session Update
(Section 8.5), Destination Up (Section 8.9), Destination Update
(Section 8.13), and Link Characteristics Response (Section 8.16)
messages to indicate the amount of latency, in microseconds, on the
link.
When used in the Link Characteristics Request message (Section 8.15),
Latency represents the maximum latency desired on the link.
The Latency value is reported as delay. The calculation of latency
is implementation dependent. For example, the latency may be a
running average calculated from the internal queuing.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Latency :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: Latency |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Data Item Type: TBD
Length: 8
Latency: A 64-bit unsigned integer, representing the transmission
delay, in microseconds, that a packet encounters as it is
transmitted over the link.
9.17. Resources (Receive)
The Resources (Receive) (RESR) data item MAY appear in the Session
Initialization Response message (Section 8.4), Session Update
(Section 8.5), Destination Up (Section 8.9), Destination Update
(Section 8.13) and Link Characteristics Response (Section 8.16)
messages to indicate the amount of resources for reception (with 0
meaning 'no resources available', and 100 meaning 'all resources
available') at the destination. The list of resources that might be
considered is beyond the scope of this document, and is left to
implementations to decide.
The Resources (Receive) data item contains the following fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESR |
+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 1
Resources (Receive): An 8-bit integer percentage, 0-100,
representing the amount of resources allocated to receiving data.
Any value greater than 100 MUST be considered as invalid.
If a device cannot calculate RESR, this data item SHOULD NOT be
issued.
9.18. Resources (Transmit)
The Resources (Transmit) (REST) data item MAY appear in the Session
Initialization Response message (Section 8.4), Session Update
(Section 8.5), Destination Up (Section 8.9), Destination Update
(Section 8.13) and Link Characteristics Response (Section 8.16)
messages to indicate the amount of resources for transmission (with 0
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meaning 'no resources available', and 100 meaning 'all resources
available') at the destination. The list of resources that might be
considered is beyond the scope of this document, and is left to
implementations to decide.
The Resources (Transmit) data item contains the following fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| REST |
+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 1
Resources (Transmit): An 8-bit integer percentage, 0-100,
representing the amount of resources allocated to transmitting
data. Any value greater than 100 MUST be considered as invalid.
If a device cannot calculate REST, this data item SHOULD NOT be
issued.
9.19. Relative Link Quality (Receive)
The Relative Link Quality (Receive) (RLQR) data item MAY appear in
the Session Initialization Response message (Section 8.4), Session
Update (Section 8.5), Destination Up (Section 8.9), Destination
Update (Section 8.13) and Link Characteristics Response
(Section 8.16) messages to indicate the quality of the link for
receiving data.
The Relative Link Quality (Receive) data item contains the following
fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RLQR |
+-+-+-+-+-+-+-+-+
Data Item Type: TBD
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Length: 1
Relative Link Quality (Receive): A non-dimensional 8-bit integer,
0-100, representing relative link quality. A value of 100
represents a link of the highest quality. Any value greater than
100 MUST be considered as invalid.
If a device cannot calculate the RLQR, this data item SHOULD NOT be
issued.
9.20. Relative Link Quality (Transmit)
The Relative Link Quality (Transmit) (RLQT) data item MAY appear in
the Session Initialization Response message (Section 8.4), Session
Update (Section 8.5), Destination Up (Section 8.9), Destination
Update (Section 8.13) and Link Characteristics Response
(Section 8.16) messages to indicate the quality of the link for
transmitting data.
The Relative Link Quality (Transmit) data item contains the following
fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RLQT |
+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 1
Relative Link Quality (Transmit): A non-dimensional 8-bit integer,
0-100, representing relative link quality. A value of 100
represents a link of the highest quality. Any value greater than
100 MUST be considered as invalid.
If a device cannot calculate the RLQT, this data item SHOULD NOT be
issued.
9.21. Link Characteristics Response Timer
The Link Characteristics Response Timer data item MAY appear in the
Link Characteristics Request message (Section 8.15) to indicate the
desired number of seconds the sender will wait for a response to the
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request. If this data item is omitted, implementations supporting
the Link Characteristics Request SHOULD choose a default value.
The Link Characteristics Response Timer data item contains the
following fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interval |
+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 1
Interval: 0 = Do not use timeouts for this Link Characteristics
request. Non-zero = Interval, in seconds, to wait before
considering this Link Characteristics Request lost.
10. Credit-Windowing
DLEP includes an optional Protocol Extension for a credit-windowing
scheme analogous to the one documented in [RFC5578]. In this scheme,
data plane traffic flowing between the router and modem is controlled
by the availability of credits. Credits are expressed as if two
unidirectional windows exist between the modem and router. This
document identifies these windows as the 'Modem Receive Window'
(MRW), and the 'Router Receive Window' (RRW).
If the credit-windowing extension is used, credits MUST be granted by
the receiver on a given window - that is, on the 'Modem Receive
Window' (MRW), the modem is responsible for granting credits to the
router, allowing it (the router) to send data plane traffic to the
modem. Likewise, the router is responsible for granting credits on
the RRW, which allows the modem to send data plane traffic to the
router.
Credits are managed on a destination-specific basis; that is,
separate credit counts are maintained for each destination requiring
the service. Credits do not apply to the DLEP session that exists
between routers and modems; they are applied only to the data plane
traffic.
Credits represent the number of octets, or an increment in the number
of octets, that MAY be sent on the given window. When sending data
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plane traffic to a credit-enabled peer, the sender MUST decriment the
appropriate window by the size of the data being sent. For example,
when sending data plane traffic via the modem, the router MUST
decriment the 'Modem Receive Window' (MRW) for the corresponding
destination. When the number of available credits to the destination
reaches 0, a sender MUST stop sending data plane traffic to the
destination, until additional credits are supplied.
If a peer is able to support the optional credit-windowing extension
then it MUST include an Extensions Supported data item (Section 9.6)
including the value 1, from Table 4, in the appropriate Session
Initialization (Section 8.3) and Session Initialization Response
(Section 8.4) message.
10.1. Credit-Windowing Messages
The credit-windowing extension introduces no additional DLEP signals
or messages. However, if a peer has advertised during session
initialization that it supports the credit-windowing extension then
the following DLEP messages MAY contain additional credit-windowing
data items:
10.1.1. Destination Up Message
The Destination Up message MAY contain one of each of the following
data items:
o Credit Grant (Section 10.2.1)
If the Destination Up message does not contain the Credit Grant data
item, credits MUST NOT be used for that destination.
10.1.2. Destination Up Response Message
If the corresponding Destination Up message contained the Credit
Grant data item, the Destination Up Response message MUST contain one
of each of the following data items:
o Credit Window Status (Section 10.2.2)
10.1.3. Destination Update Message
If the corresponding Destination Up message contained the Credit
Grant data item, the Destination Update message MUST contain one of
each of the following data items:
o Credit Window Status (Section 10.2.2)
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If the corresponding Destination Up message contained the Credit
Grant data item, the Destination Update message MAY contain one of
each of the following data items:
o Credit Grant (Section 10.2.1)
o Credit Request (Section 10.2.3)
10.2. Credit-Windowing Data Items
The credit-windowing extension introduces 3 additional data items.
If a peer has advertised during session initialization that it
supports the credit-windowing extension then it MUST correctly
process the following data items:
+------------+------------------------------------------------------+
| Type Code | Description |
+------------+------------------------------------------------------+
| 23 | Credit Grant (Section 10.2.1) |
| 24 | Credit Window Status (Section 10.2.2) |
| 25 | Credit Request (Section 10.2.3) |
+------------+------------------------------------------------------+
10.2.1. Credit Grant
The Credit Grant data item is sent from a DLEP participant to grant
an increment to credits on a window. The Credit Grant data item MAY
appear in the Destination Up (Section 8.9) and Destination Update
(Section 8.13) messages. The value in a Credit Grant data item
represents an increment to be added to any existing credits available
on the window. Upon successful receipt and processing of a Credit
Grant data item, the receiver MUST respond with a message containing
a Credit Window Status data item to report the updated aggregate
values for synchronization purposes, and if initializing a new credit
window, granting initial credits.
When DLEP peers desire to employ the credit-windowing extension, the
peer originating the Destination Up message MUST supply an initial,
non-zero value as the credit increment of the receive window it
controls (i.e., the Modem Recive Window, or Router Receive Window).
When receiving a Credit Grant data item on a Destination Up
(#msg_dest_up) message, the receiver MUST take one of the following
actions:
1. Reject the use of credits for this destination, via the
Destination Up Response message containing a Status data item
(Section 9.1) with a status code of 'Request Denied'. (See
Table 3), or
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2. Initialize the appropriate window value of zero, then apply the
increment specified in the Credit Grant data item.
If the initialization completes successfully, the receiver MUST
respond to the Destination Up message with a Destination Up Response
message that contains a Credit Window Status data item, initializing
its receive window.
The Credit Grant data item contains the following fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Credit Increment :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: Credit Increment |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 8
Reserved: A 64-bit unsigned integer representing the additional
credits to be assigned to the credit window.
Since credits can only be granted by the receiver on a window, the
applicable credit window (either the MRW or the RRW) is derived from
the sender of the grant. The Credit Increment MUST NOT cause the
window to overflow; if this condition occurs, implementations MUST
set the credit window to the maximum value contained in a 64-bit
quantity.
10.2.2. Credit Window Status
If the credit-window extension is supported by the DLEP participants
(both the router and the modem), the Credit Window Status data item
MUST be sent by the participant receiving a Credit Grant for a given
destination.
The Credit Window Status data item contains the following fields:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Modem Receive Window Value :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: Modem Receive Window Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router Receive Window Value :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: Router Receive Window Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 16
Modem Receive Window Value: A 64-bit unsigned integer, indicating
the current number of credits available on the Modem Receive
Window, for the destination referred to by the message.
Router Receive Window Value: A 64-bit unsigned integer, indicating
the current number of credits available on the Router Receive
Window, for the destination referred to by the message.
10.2.3. Credit Request
The Credit Request data item MAY be sent from either DLEP
participant, via the Destination Update message (Section 8.13), to
indicate the desire for the partner to grant additional credits in
order for data transfer to proceed on the session. If the
corresponding Destination Up message (Section 8.9) for this session
did not contain a Credit Window Status data item, indicating that
credits are to be used on the session, then the Credit Request data
item MUST be silently dropped by the receiver.
The Credit Request data item contains the following fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 0
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11. Security Considerations
The potential security concerns when using DLEP are:
1. DLEP peers may be 'spoofed' by an attacker, either at DLEP
session initialization, or by injection of messages once a
session has been established, and/or
2. DLEP data items could be altered by an attacker, causing the
receiving peer to inappropriately alter its information base
concerning network status.
The protocol itself does not contain any mechanisms for security
(e.g., authentication or encryption), as it assumes that an
appropriate level of authentication and non-repudiation is acheived
by use of [TLS] when necessary. This specification does not address
security of the data plane, as it (the data plane) is not affected,
and standard security procedures can be employed.
12. IANA Considerations
This section specifies requests to IANA.
12.1. Registrations
This specification defines:
o A new repository for DLEP signals and messages, with sixteen (16)
values currently assigned.
o Reservation of a Private Use numbering space for experimental DLEP
signals and messages.
o A new repository for DLEP data items, with twenty-four (24) values
currently assigned.
o Reservation of a Private Use numbering space in the data items
repository for experimental data items.
o A new repository for DLEP status codes, with eight (8) currently
assigned.
o Reservation of a Private Use numbering space in the status codes
repository for experimental status codes.
o A new repository for DLEP extensions, with one (1) value currently
assigned.
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o Reservation of a Private Use numbering space in the extension
repository for experimental extensions.
o A request for allocation of a well-known port for DLEP TCP and UDP
communication.
o A request for allocation of a multicast IP address for DLEP
discovery.
12.2. Expert Review: Evaluation Guidelines
No additional guidelines for expert review are anticipated.
12.3. Signal/Message Type Registration
A new repository must be created with the values of the DLEP signals
and messages.
All signal and message values are in the range [0..65535], defined in
Table 1.
12.4. DLEP Data Item Registrations
A new repository for DLEP data items must be created.
All data item values are in the range [0..65535], defined in Table 2.
12.5. DLEP Status Code Registrations
A new repository for DLEP status codes must be created.
All status codes are in the range [0..255], defined in Table 3.
12.6. DLEP Extensions Registrations
A new repository for DLEP extensions must be created.
All extension values are in the range [0..65535]. Current
allocations are:
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+-------------+-----------------------------------------------------+
| Code | Description |
+-------------+-----------------------------------------------------+
| 0 | Reserved |
| 1 | Credit Windowing (Section 10) |
| 2-65519 | Reserved for future extensions |
| 65520-65534 | Private Use. Available for experiments |
| 65535 | Reserved |
+-------------+-----------------------------------------------------+
Table 4: DLEP Extension types
12.7. DLEP Well-known Port
It is requested that IANA allocate a well-known port number for DLEP
communication.
12.8. DLEP Multicast Address
It is requested that IANA allocate a multicast address for DLEP
discovery signals.
13. Acknowledgements
We would like to acknowledge and thank the members of the DLEP design
team, who have provided invaluable insight. The members of the
design team are: Teco Boot, Bow-Nan Cheng, John Dowdell, and Henning
Rogge.
We would also like to acknowledge the influence and contributions of
Greg Harrison, Chris Olsen, Martin Duke, Subir Das, Jaewon Kang,
Vikram Kaul, Nelson Powell and Victoria Mercieca.
14. References
14.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
14.2. Informative References
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC5578] Berry, B., Ratliff, S., Paradise, E., Kaiser, T., and M.
Adams, "PPP over Ethernet (PPPoE) Extensions for Credit
Flow and Link Metrics", RFC 5578, February 2010.
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Appendix A. Discovery Signal Flows
Router Modem Signal Description
========================================================================
| Router initiates discovery, starts
| a timer, send Peer Discovery
|-------Peer Discovery---->|| signal.
~ ~ ~ ~ ~ ~ ~ Router discovery timer expires
without receiving Peer Offer.
| Router sends another Peer
|-------Peer Discovery---------->| Discovery signal.
|
| Modem receives Peer Discovery
| signal.
|
| Modem sends Peer Offer with
|<--------Peer Offer-------------| Connection Point information.
:
: Router MAY cancel discovery timer
: and stop sending Peer Discovery
: signals.
Appendix B. Peer Level Message Flows
B.1. Session Initialization
Router Modem Signal Description
========================================================================
| Router connects to discovered or
| pre-configured Modem Connection
|---------TCP connect----------> Point.
|
| Router sends Session Initialization
|----Session Initialization----->| message.
|
| Modem receives Session Initialization
| message.
|
| Modem sends Session Initialization
|<--Session Initialization Resp.-| Response, with Success status data item.
| |
|<<============================>>| Session established. Heartbeats
: : begin.
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B.2. Session Initialization - Refused
Router Modem Signal Description
========================================================================
| Router connects to discovered or
| pre-configured Modem Connection
|---------TCP connect----------> Point.
|
| Router sends Session Initialization
|-----Session Initialization---->| message.
|
| Modem receives Session Initialization
| message, and will not support the
| advertised extensions.
|
| Modem sends Session Initialization
| Response, with 'Request Denied' status
|<-Session Initialization Resp.--| data item.
|
|
| Router receives negative Session
| Initialization Response, closes
||---------TCP close------------|| TCP connection.
B.3. Router Changes IP Addresses
Router Modem Signal Description
========================================================================
| Router sends Session Update message to
|-------Session Update---------->| announce change of IP address
|
| Modem receives Session Update message
| and updates internal state.
|
|<----Session Update Response----| Modem sends Session Update Response.
B.4. Modem Changes Session-wide Metrics
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Router Modem Signal Description
========================================================================
| Modem sends Session Update message to
| announce change of modem-wide
|<--------Session Update---------| metrics
|
| Router receives Session Update message
| and updates internal state.
|
|----Session Update Response---->| Router sends Session Update Response.
B.5. Router Terminates Session
Router Modem Signal Description
========================================================================
| Router sends Session Termination
|------Session Termination------>| message with Status data item.
| |
|-------TCP shutdown (send)---> | Router stops sending messages.
|
| Modem receives Session Termination,
| stops counting received heartbeats
| and stops sending heartbeats.
|
| Modem sends Session Termination Response
|<---Session Termination Resp.---| with Status 'Success'.
|
| Modem stops sending messages.
|
||---------TCP close------------|| Session terminated.
B.6. Modem Terminates Session
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Router Modem Signal Description
========================================================================
| Modem sends Session Termination
|<----Session Termination--------| message with Status data item.
|
| Modem stops sending messages.
|
| Router receives Session Termination,
| stops counting received heartbeats
| and stops sending heartbeats.
|
| Router sends Session Termination Response
|---Session Termination Resp.--->| with Status 'Success'.
|
| Router stops sending messages.
|
||---------TCP close------------|| Session terminated.
B.7. Session Heartbeats
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Router Modem Signal Description
========================================================================
|----------Heartbeat------------>| Router sends heartbeat message
|
| Modem resets heartbeats missed
| counter.
~ ~ ~ ~ ~ ~ ~
|---------[Any message]--------->| When the Modem receives any message
| from the Router.
|
| Modem resets heartbeats missed
| counter.
~ ~ ~ ~ ~ ~ ~
|<---------Heartbeat-------------| Modem sends heartbeat message
|
| Router resets heartbeats missed
| counter.
~ ~ ~ ~ ~ ~ ~
|<--------[Any message]----------| When the Router receives any
| message from the Modem.
|
| Modem resets heartbeats missed
| counter.
B.8. Router Detects a Heartbeat timeout
Router Modem Signal Description
========================================================================
||<----------------------| Router misses a heartbeat
| ||<----------------------| Router misses too many heartbeats
|
|
|------Session Termination------>| Router sends Session Termination
| message with 'Timeout' Status
| data item.
:
: Termination proceeds as above.
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B.9. Modem Detects a Heartbeat timeout
Router Modem Signal Description
========================================================================
|---------------------->|| Modem misses a heartbeat
|---------------------->|| | Modem misses too many heartbeats
|
|
|<-----Session Termination-------| Modem sends Session Termination
| message with 'Timeout' Status
| data item.
:
: Termination proceeds as above.
Appendix C. Destination Specific Signal Flows
C.1. Common Destination Signaling
Router Modem Signal Description
========================================================================
| Modem detects a new logical
| destination is reachable, and
|<-------Destination Up----------| sends Destination Up message.
|
|------Destination Up Resp.----->| Router sends Destination Up Response.
~ ~ ~ ~ ~ ~ ~
| Modem detects change in logical
| destination metrics, and sends
|<-------Destination Update------| Destination Update message.
~ ~ ~ ~ ~ ~ ~
| Modem detects change in logical
| destination metrics, and sends
|<-------Destination Update------| Destination Update message.
~ ~ ~ ~ ~ ~ ~
| Modem detects logical destination
| is no longer reachable, and sends
|<-------Destination Down--------| Destination Down message.
|
| Router receives Destination Down,
| updates internal state, and sends
|------Destination Down Resp.--->| Destination Down Response message.
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C.2. Multicast Destination Signaling
Router Modem Signal Description
========================================================================
| Router detects a new multicast
| destination is in use, and sends
|--------Destination Up--------->| Destination Up message.
|
| Modem updates internal state to
| monitor multicast destination, and
|<-----Destination Up Resp.------| sends Destination Up Response.
~ ~ ~ ~ ~ ~ ~
| Modem detects change in multicast
| destination metrics, and sends
|<-------Destination Update------| Destination Update message.
~ ~ ~ ~ ~ ~ ~
| Modem detects change in multicast
| destination metrics, and sends
|<-------Destination Update------| Destination Update message.
~ ~ ~ ~ ~ ~ ~
| Router detects multicast
| destination is no longer in use,
|--------Destination Down------->| and sends Destination Down message.
|
| Modem receives Destination Down,
| updates internal state, and sends
|<-----Destination Down Resp.----| Destination Down Response message.
C.3. Link Characteristics Request
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Router Modem Signal Description
========================================================================
Destination has already been
~ ~ ~ ~ ~ ~ ~ announced by either peer.
| Router requires different
| Characteristics for the
| destination, and sends Link
|--Link Characteristics Request->| Characteristics Request message.
|
| Modem attempts to adjust link
| status to meet the received
| request, and sends a Link
| Characteristics Response
|<---Link Characteristics Resp.--| message with the new values.
Authors' Addresses
Stan Ratliff
VT iDirect
13861 Sunrise Valley Drive, Suite 300
Herndon, VA 20171
USA
Email: sratliff@idirect.net
Bo Berry
Shawn Jury
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
USA
Email: sjury@cisco.com
Darryl Satterwhite
Broadcom
Email: dsatterw@broadcom.com
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Rick Taylor
Airbus Defence & Space
Quadrant House
Celtic Springs
Coedkernew
Newport NP10 8FZ
UK
Email: rick.taylor@airbus.com
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