Mobile Ad hoc Networks Working Group S. Ratliff
Internet-Draft VT iDirect
Intended status: Standards Track B. Berry
Expires: November 14, 2015
S. Jury
Cisco Systems
D. Satterwhite
Broadcom
R. Taylor
Airbus Defence & Space
May 13, 2015
Dynamic Link Exchange Protocol (DLEP)
draft-ietf-manet-dlep-14
Abstract
When routing devices rely on modems to effect communications over
wireless links, they need timely and accurate knowledge of the
characteristics of the link (speed, state, etc.) in order to make
routing decisions. In mobile or other environments where these
characteristics change frequently, manual configurations or the
inference of state through routing or transport protocols does not
allow the router to make the best decisions. A bidirectional, event-
driven communication channel between the router and the modem is
necessary.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 14, 2015.
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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 Optional Extensions . . . . . . . . . . . . 10
3.1. Negotiation of Optional Extensions . . . . . . . . . . . 10
3.2. Protocol Extensions . . . . . . . . . . . . . . . . . . . 11
3.3. Experimental Signals and Data Items . . . . . . . . . . . 11
4. Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1. Mandatory Metrics . . . . . . . . . . . . . . . . . . . . 12
5. DLEP Session Flow . . . . . . . . . . . . . . . . . . . . . . 12
5.1. DLEP Router session flow - Discovery case . . . . . . . . 13
5.2. DLEP Router session flow - Configured case . . . . . . . 13
5.3. DLEP Modem session flow . . . . . . . . . . . . . . . . . 14
5.4. Common Session Flow . . . . . . . . . . . . . . . . . . . 15
6. DLEP Signal Structure and Processing . . . . . . . . . . . . 16
6.1. DLEP Signal Header . . . . . . . . . . . . . . . . . . . 16
6.2. DLEP Generic Data Item . . . . . . . . . . . . . . . . . 17
7. DLEP Signals . . . . . . . . . . . . . . . . . . . . . . . . 17
7.1. Peer Discovery Signal . . . . . . . . . . . . . . . . . . 18
7.2. Peer Offer Signal . . . . . . . . . . . . . . . . . . . . 19
7.3. Peer Initialization Signal . . . . . . . . . . . . . . . 19
7.4. Peer Initialization ACK Signal . . . . . . . . . . . . . 20
7.5. Peer Update Signal . . . . . . . . . . . . . . . . . . . 22
7.6. Peer Update ACK Signal . . . . . . . . . . . . . . . . . 23
7.7. Peer Termination Signal . . . . . . . . . . . . . . . . . 24
7.8. Peer Termination ACK Signal . . . . . . . . . . . . . . . 25
7.9. Destination Up Signal . . . . . . . . . . . . . . . . . . 25
7.10. Destination Up ACK Signal . . . . . . . . . . . . . . . . 26
7.11. Destination Down Signal . . . . . . . . . . . . . . . . . 27
7.12. Destination Down ACK Signal . . . . . . . . . . . . . . . 27
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7.13. Destination Update Signal . . . . . . . . . . . . . . . . 28
7.14. Heartbeat Signal . . . . . . . . . . . . . . . . . . . . 29
7.15. Link Characteristics Request Signal . . . . . . . . . . . 29
7.16. Link Characteristics ACK Signal . . . . . . . . . . . . . 30
8. DLEP Data Items . . . . . . . . . . . . . . . . . . . . . . . 31
8.1. DLEP Version . . . . . . . . . . . . . . . . . . . . . . 32
8.2. Status . . . . . . . . . . . . . . . . . . . . . . . . . 33
8.3. IPv4 Connection Point . . . . . . . . . . . . . . . . . . 34
8.4. IPv6 Connection Point . . . . . . . . . . . . . . . . . . 35
8.5. Peer Type . . . . . . . . . . . . . . . . . . . . . . . . 36
8.6. Heartbeat Interval . . . . . . . . . . . . . . . . . . . 36
8.7. Extensions Supported . . . . . . . . . . . . . . . . . . 37
8.8. Experimental Definition . . . . . . . . . . . . . . . . . 38
8.9. MAC Address . . . . . . . . . . . . . . . . . . . . . . . 38
8.10. IPv4 Address . . . . . . . . . . . . . . . . . . . . . . 39
8.11. IPv6 Address . . . . . . . . . . . . . . . . . . . . . . 40
8.12. IPv4 Attached Subnet . . . . . . . . . . . . . . . . . . 40
8.13. IPv6 Attached Subnet . . . . . . . . . . . . . . . . . . 41
8.14. Maximum Data Rate (Receive) . . . . . . . . . . . . . . . 42
8.15. Maximum Data Rate (Transmit) . . . . . . . . . . . . . . 43
8.16. Current Data Rate (Receive) . . . . . . . . . . . . . . . 43
8.17. Current Data Rate (Transmit) . . . . . . . . . . . . . . 44
8.18. Latency . . . . . . . . . . . . . . . . . . . . . . . . . 45
8.19. Resources (Receive) . . . . . . . . . . . . . . . . . . . 46
8.20. Resources (Transmit) . . . . . . . . . . . . . . . . . . 46
8.21. Relative Link Quality (Receive) . . . . . . . . . . . . . 47
8.22. Relative Link Quality (Transmit) . . . . . . . . . . . . 48
8.23. Link Characteristics ACK Timer . . . . . . . . . . . . . 48
9. Credit-Windowing . . . . . . . . . . . . . . . . . . . . . . 49
9.1. Credit-Windowing Signals . . . . . . . . . . . . . . . . 49
9.1.1. Destination Up Signal . . . . . . . . . . . . . . . . 49
9.1.2. Destination Up ACK Signal . . . . . . . . . . . . . . 50
9.1.3. Destination Update Signal . . . . . . . . . . . . . . 50
9.2. Credit-Windowing Data Items . . . . . . . . . . . . . . . 50
9.2.1. Credit Grant . . . . . . . . . . . . . . . . . . . . 51
9.2.2. Credit Window Status . . . . . . . . . . . . . . . . 52
9.2.3. Credit Request . . . . . . . . . . . . . . . . . . . 52
10. Security Considerations . . . . . . . . . . . . . . . . . . . 53
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 53
11.1. Registrations . . . . . . . . . . . . . . . . . . . . . 53
11.2. Expert Review: Evaluation Guidelines . . . . . . . . . . 54
11.3. Signal Type Registration . . . . . . . . . . . . . . . . 54
11.4. DLEP Data Item Registrations . . . . . . . . . . . . . . 55
11.5. DLEP Status Code Registrations . . . . . . . . . . . . . 56
11.6. DLEP Extensions Registrations . . . . . . . . . . . . . 56
11.7. DLEP Well-known Port . . . . . . . . . . . . . . . . . . 57
11.8. DLEP Multicast Address . . . . . . . . . . . . . . . . . 57
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 57
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13. References . . . . . . . . . . . . . . . . . . . . . . . . . 57
13.1. Normative References . . . . . . . . . . . . . . . . . . 57
13.2. Informative References . . . . . . . . . . . . . . . . . 57
Appendix A. Peer Level Signal Flows . . . . . . . . . . . . . . 57
A.1. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 57
A.2. Session Initialization . . . . . . . . . . . . . . . . . 58
A.3. Session Initialization - Refused . . . . . . . . . . . . 59
A.4. Router Changes IP Addresses . . . . . . . . . . . . . . . 59
A.5. Modem Changes Session-wide Metrics . . . . . . . . . . . 59
A.6. Router Terminates Session . . . . . . . . . . . . . . . . 60
A.7. Modem Terminates Session . . . . . . . . . . . . . . . . 60
A.8. Session Heartbeats . . . . . . . . . . . . . . . . . . . 61
A.9. Router Detects a Heartbeat timeout . . . . . . . . . . . 62
A.10. Modem Detects a Heartbeat timeout . . . . . . . . . . . . 63
Appendix B. Destination Specific Signal Flows . . . . . . . . . 63
B.1. Common Destination Signaling . . . . . . . . . . . . . . 63
B.2. Multicast Destination Signaling . . . . . . . . . . . . . 64
B.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
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on interface state and independent timers at OSI Layer 3 to maintain
network convergence (e.g., HELLO messages and/or recognition of DEAD
routing adjacencies). These dynamic connections can be better
utilized with an event-driven paradigm, where acquisition of a new
neighbor (or loss of an existing one) is signaled, as opposed to a
paradigm driven by timers and/or interface state.
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
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In Figure 1, when the local modem detects the presence of a remote
node, it (the local modem) sends a signal to its router via the DLEP
protocol. The signal consists of an indication of what change has
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 signal, 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 signals
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 signals used by modems
and their attached routers. The signals 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 signals 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 signals that are exchanged between a
router and a modem, and the data items associated with the signal.
This document specifies transport of DLEP signals 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 7.1).
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 signal (Section 7.9). 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, and TCP for
transport of the control signals. 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 signals 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 signal 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.
DLEP assumes that security on the session (e.g., authentication of
session partners, encryption of traffic, or both) is dealt with by
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the underlying transport mechanism (e.g., by using a transport such
as TLS [RFC5246]).
This document specifies an implementation of the DLEP signals and
data items running over the TCP transport. It is assumed that DLEP
running over other transport mechanisms would be documented
separately.
3. Core Features and Optional Extensions
DLEP has a core set of signals and data items that MUST be processed
without error by an implementation in order to guarantee
interoperability and therefore make the implementation DLEP
compliant. This document defines the core set of signals and data
items, listing them as 'mandatory'. It should be noted that some
core signals 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. To
support future extension of DLEP, this document describes an
extension negotiation capability to be used during session
initialization via the Extensions Supported data item, documented in
Section 8.7 of this document.
All extensions are considered OPTIONAL. Only the DLEP functionality
listed as 'mandatory' is required by implementation in order to be
DLEP compliant.
This specification defines one extension, Credit windowing, exposed
via the Extensions Supported mechanism that implementations MAY
choose to implement, or to omit.
3.1. Negotiation of Optional Extensions
Optional extensions supported by an implementation MUST be declared
to potential DLEP peers using the Extensions Supported data item
(Section 8.7) during the session initialization sequence. Once both
peers have exchanged initialization signals, an implementation MUST
NOT emit any signal or data item associated with an optional
extension that was not specified in the received initialization
signal from its peer.
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3.2. Protocol Extensions
If/when protocol extensions are required, they should 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, both in terms of DLEP
signals and DLEP data items, to accommodate future extensions to the
protocol and the data transferred.
3.3. Experimental Signals and Data Items
This document requests numbering space in both the DLEP signal and
data item registries for experimental items. The intent is to allow
for experimentation with either (1) new signals, (2) new data items,
or (3) both new signals and new data items, while still retaining the
documented DLEP behavior. If a given experiment proves successful,
it SHOULD be documented as an update to this document, or as a stand-
alone specification.
Use of the experimental signals, data items, or behaviors MUST be
announced by inclusion of an Experimental Definition data item
(Section 8.8) with a value agreed upon (a priori) between the
participating peers. The exact mechanism for a priori communication
of the experimental definition formats is beyond the scope of this
document.
Multiple Experimental Definition data items MAY appear in the Peer
Initialization/Peer Initialization ACK sequence. However, use of
multiple experiments in a single peer session could lead to
interoperability issues or unexpected results (e.g., redefinition of
experimental signals and/or data items), and is therefore
discouraged. It is left to implementations to determine the correct
processing path (e.g., a decision on whether to terminate the peer
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 'modem-wide' (those that apply to all destinations accessed via
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the modem). Most metrics can be further subdivided into transmit and
receive metrics. Metrics supplied on DLEP Peer signals are, by
definition, modem-wide; metrics supplied on Destination signals are,
by definition, used for the specific logical destination only.
DLEP modem implementations MUST announce all supported metric items,
and provide default values for those metrics, in the Peer
Initialization ACK signal (Section 7.4). In order to introduce a new
metric type, DLEP modem implementations MUST terminate the session
with the router (via the Peer Terminate signal (Section 7.7)), and
allow for session re-establishment.
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).
The approach of allowing for different contexts for metric data
increases both the flexibility and the complexity of using metric
data. This document details the mechanism whereby the data is
transmitted, however, the specific algorithms (precedence, etc.) for
utilizing the dual-context metrics are out of scope and not addressed
by this document.
4.1. Mandatory Metrics
As mentioned above, DLEP modem implementations MUST announce all
supported metric items during session initialization. However, an
implementation MUST include the following list of metrics:
o Maximum Data Rate (Receive) (Section 8.14)
o Maximum Data Rate (Transmit) (Section 8.15)
o Current Data Rate (Receive) (Section 8.16)
o Current Data Rate (Transmit) (Section 8.17)
o Latency (Section 8.18)
5. DLEP Session Flow
For routers supporting DLEP, support of Discovery is optional.
Discovery is initiated in the DLEP modem by sending the Peer
Discovery Signal (Section 7.1) to a well-known multicast address.
However, support for receipt and processing of the signal is optional
in the router (see Appendix A for flow diagrams of the discovery
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signal). Due to the optional (on the router) support for discovery,
normal session flow is described for both the 'Discovery case', and
the 'Configured case'. Again, for modem implementations of DLEP,
support of Discovery is mandatory; therefore, that is the only case
to be described.
5.1. DLEP Router session flow - Discovery case
If the DLEP router implementation is utilizing the optional discovery
mechanism, then the implementation will initialize a UDP socket,
binding it to an arbitrary port. This UDP socket is used to send the
Peer Discovery signal (Section 7.1) to the DLEP link-local multicast
address and port (TBD). The implementation then waits on receipt of
a Peer Offer signal (Section 7.2), which MAY contain the unicast
address and port for TCP-based communication with a DLEP modem, via
the IPv4 Connection Point data item (Section 8.3) or the IPv6
Connection Point data item (Section 8.4). The Peer Offer signal MAY
contain multiple IP Connection Point data items. If more than one IP
Connection Point data items is in the Peer Offer, router
implementations MAY use their own heuristics to determine the best
address/port combination. 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 11.7) to establish the TCP connection. At this
point, the router implementation MAY either destroy the UDP socket,
or continue to issue Peer Discovery signals to the link-local
address/port combination. In either case, the TCP session
initialization occurs as in the configured case.
5.2. DLEP Router session flow - Configured case
When a DLEP router implementation has the address and port
information for a TCP connection to a modem (obtained either via
configuration or via the discovery process described above), the
router will initialize and bind a TCP socket. This socket is used to
connect to the DLEP modem software. After a successful TCP connect,
the router implementation MUST issue a Peer Initialization signal
(Section 7.3) to the DLEP modem. After sending the Peer
Initialization, the router implementation MUST wait for receipt of a
Peer Initialization ACK signal (Section 7.4) from the modem. Receipt
of the Peer Initialization ACK signal containing a Status data item
(Section 8.2) with value 'Success', indicates that the modem has
received and processed the Peer Initialization, and the session MUST
transition to the 'in session' state. At this point, signals
regarding destinations in the network, and/or Peer Update signals
(Section 7.5), can flow on the DLEP session between modem and router,
and Heartbeat signals can begin to flow, if Heartbeats are used. The
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'in session' state is maintained until one of the following
conditions occur:
o The session is explicitly terminated (using Peer Termination), or
o The session times out, based on supplied timeout values.
5.3. DLEP Modem session flow
DLEP modem implementations MUST support the discovery mechanism.
Therefore, the normal flow is as follows:
The implementation will initialize a UDP socket, binding that socket
to the DLEP link-local multicast address (TBD) and the DLEP well-
known port number (also TBD). The implementation will then
initialize a TCP socket, on a unicast address and port. This socket
is used to listen for incoming TCP connection requests.
When the modem implementation receives a Peer Discovery signal
(Section 7.1) on the UDP socket, it responds by issuing a Peer Offer
signal (Section 7.2) to the sender of the Peer Discovery signal. The
Peer Offer signal MAY contain the unicast address and port of the
listening TCP socket, as described above. A DLEP modem
implementation MAY respond with ALL address/port combinations that
have an active TCP listen posted. Anything other than Peer Discovery
signals received on the UDP socket MUST be silently dropped.
When the DLEP modem implementation accepts a connection via TCP, it
MUST wait for receipt of a Peer Initialization signal (Section 7.3),
sent by the router. Upon receipt and successful parsing of a Peer
Initialization signal, the modem MUST respond with a Peer
Initialization ACK signal (Section 7.4). The Peer Initialization ACK
signal MUST contain metric data items for ALL supported metrics. If
an additional metric is to be introduced, the DLEP session between
router and modem MUST be terminated and restarted, and the new metric
described in a Peer Initialization ACK signal. Once the Peer
Initialization signal (Section 7.3) and Peer Initialization ACK
signal (Section 7.4) have been exchanged, the session is transitioned
to the 'in session' state. As in the router case, when the 'in
session' state is reached, signals regarding destinations in the
network, and/or Peer Update signals (Section 7.5), can flow on the
DLEP session between modem and router, and Heartbeat signals can
begin to flow, if Heartbeats are used. The 'in session' state
persists until the session is explicitly terminated (using Peer
Termination), or it times out (based on timeout values).
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5.4. Common Session Flow
In order to maintain the session between router and modem, periodic
Heartbeat signals (Section 7.14) MAY be exchanged. These signals are
intended to keep the session alive, and to verify bidirectional
connectivity between the two participants. If heartbeat signals are
exchanged, they do not begin until the DLEP peer session has entered
the 'in session' state. Each DLEP peer is responsible for the
creation of heartbeat signals. Receipt of any DLEP signal SHOULD
reset the heartbeat interval timer (i.e., valid DLEP signals take the
place of, and obviate the need for, Heartbeat signals).
DLEP also provides a Peer Update signal (Section 7.5), 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 local (Peer level) signals above, the participants
will transmit DLEP signals concerning destinations in the network.
These signals 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 signal (Section 7.9). 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 signal
(Section 7.11), and changes in status to the destination (e.g.,
varying link quality, or addressing changes) are communicated via the
Destination Update signal (Section 7.13). The information on a given
destination will persist in the router's information base until (1) a
Destination Down signal is received, indicating that the modem has
lost contact with the remote node, or (2) the router/modem session
terminates, indicating that the router has lost contact with its own
local modem.
Metrics can be expressed within the context of a specific destination
via the Destination Update signal, or on a modem-wide basis via the
Peer Update signal. In cases where metrics are provided at peer
level, the receiver MUST propagate the metrics to all entries in its
information base for destinations that are accessed via the
originator. A DLEP participant MAY send metrics both in a router/
modem session context (via the Peer Update signal) and a specific
destination context (via Destination Update) at any time. The
heuristics for applying received metrics is left to implementations.
In addition to receiving metrics about the link, DLEP provides a
signal allowing a router to request a different datarate, or latency,
from the modem. This signal is referred to as the Link
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Characteristics Request signal (Section 7.15), 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.
6. DLEP Signal Structure and Processing
Communication between DLEP peers consists of a bidirectional stream
of signals (messages), each signal consisting of a signal header and
an unordered list of data items. Signal 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 the
signal header are described as being 'contained in' the signal.
All integer values structures MUST be in network byte-order.
There is no restriction on the order of data items following a
signal, and the multiplicity of duplicate data items is defined by
the definition of the signal declared by the type in the signal
header.
If an unrecognized, or unexpected signal is received, or a received
signal contains unrecognized, invalid, or disallowed duplicate data
items, the receiving peer MUST terminate the session by issuing a
Peer Termination signal (Section 7.7) with a Status data item
(Section 8.2) containing the most relevant status code, and then
close the TCP connection.
6.1. DLEP Signal Header
The DLEP signal header contains the following fields:
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Signal Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: DLEP Signal Header
Signal Type: An 8-bit unsigned integer containing one of the DLEP
Signal Type values defined in this document.
Length: The length, expressed as a 16-bit unsigned integer, of all
of the DLEP data items associated with this signal. This length
does not include the length of the header itself
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The DLEP Signal Header is immediately followed by one or more DLEP
data items, encoded in TLVs, as defined in this document.
6.2. 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 4: DLEP Generic Data Item
Data Item Type: An 8-bit unsigned integer field specifying the data
item being sent.
Length: The length, expressed as an 8-bit unsigned integer, of the
value field of the data item.
Value: A field of length <Length> which contains data specific to a
particular data item.
7. DLEP Signals
As mentioned above, all DLEP signals begin with the DLEP signal
header structure. Therefore, in the following descriptions of
specific signals, this header structure is assumed, and will not be
replicated.
Following is the set of MANDATORY signals that must be recognized by
a DLEP compliant implementation. As mentioned before, not all
signals may be used during a session, but an implementation MUST
correctly process these signals when received.
The mandatory DLEP signals are:
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+--------+--------------------+----------------------+--------------+
| Signal | Description | Mnemonic | Section |
+--------+--------------------+----------------------+--------------+
| TBD | Peer Discovery | DLEP_PEER_DISCOVERY | Section 7.1 |
| TBD | Peer Offer | DLEP_PEER_OFFER | Section 7.2 |
| TBD | Peer | DLEP_PEER_INIT | Section 7.3 |
| | Initialization | | |
| TBD | Peer | DLEP_PEER_INIT_ACK | Section 7.4 |
| | Initialization ACK | | |
| TBD | Peer Update | DLEP_PEER_UPDATE | Section 7.5 |
| TBD | Peer Update ACK | DLEP_PEER_UPDATE_ACK | Section 7.6 |
| TBD | Peer Termination | DLEP_PEER_TERM | Section 7.7 |
| TBD | Peer Termination | DLEP_PEER_TERM_ACK | Section 7.8 |
| | ACK | | |
| TBD | Destination Up | DLEP_DEST_UP | Section 7.9 |
| TBD | Destination Up ACK | DLEP_DEST_UP_ACK | Section 7.10 |
| TBD | Destination Down | DLEP_DEST_DOWN | Section 7.11 |
| TBD | Destination Down | DLEP_DEST_DOWN_ACK | Section 7.12 |
| | ACK | | |
| TBD | Destination Update | DLEP_DEST_UPDATE | Section 7.13 |
| TBD | Heartbeat | DLEP_PEER_HEARTBEAT | Section 7.14 |
| TBD | Link | DLEP_LINK_CHAR_REQ | Section 7.15 |
| | Characteristics | | |
| | Request | | |
| TBD | Link | DLEP_LINK_CHAR_ACK | Section 7.16 |
| | Characteristics | | |
| | ACK | | |
+--------+--------------------+----------------------+--------------+
Table 1: DLEP Signal Values
7.1. 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 7.2) 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 DLEP_PEER_DISCOVERY in Table 1.
The Peer Discovery signal MUST contain the following data item:
o DLEP Version (Section 8.1)
The Peer Discovery signal MAY contain the following data item:
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o Peer Type (Section 8.5)
7.2. Peer Offer Signal
A Peer Offer signal MUST be sent by a DLEP modem in response to a
valid Peer Discovery signal (Section 7.1).
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 DLEP_PEER_OFFER in Table 1.
The Peer Offer signal MUST contain the following data item:
o DLEP Version (Section 8.1)
The Peer Offer signal MAY contain the following data item:
o Peer Type (Section 8.5)
The Peer Offer signal MAY contain one or more of any of the following
data items, with different values:
o IPv4 Connection Point (Section 8.3)
o IPv6 Connection Point (Section 8.4)
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 11.7) to establish the TCP connection.
7.3. Peer Initialization Signal
A Peer Initialization signal MUST be sent by a router as the first
signal 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 Peer
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Initialization signal, the receiver of the signal MUST conclude that
there is NO support for extensions in the sender.
If any experimental signals or data items are used by the
implementation, they MUST be enumerated in one or more Experimental
Definition data items. If there are no Experimental Definition data
items in a Peer Initialization signal, the receiver of the signal
MUST conclude that no experimental definitions are in use by the
sender.
Implementations supporting the Heartbeat Interval (Section 8.6)
should understand that heartbeats are not fully established until
receipt of Peer Initialization ACK Signal (Section 7.4), and should
therefore implement their own timeout and retry heuristics for this
signal.
To construct a Peer Initialization signal, the Signal Type value in
the signal header is set to DLEP_PEER_INIT in Table 1.
The Peer Initialization signal MUST contain one of each of the
following data items:
o DLEP Version (Section 8.1)
o Heartbeat Interval (Section 8.6)
The Peer Initialization signal MAY contain one of each of the
following data items:
o Peer Type (Section 8.5)
o Extensions Supported (Section 8.7)
The Peer Initialization signal MAY contain one or more of any of the
following data items, with different values:
o Experimental Definition (Section 8.8)
A Peer Initialization signal MUST be acknowledged by the receiver
issuing a Peer Initialization ACK signal (Section 7.4).
7.4. Peer Initialization ACK Signal
A Peer Initialization ACK signal MUST be sent in response to a
received Peer Initialization signal (Section 7.3). The Peer
Initialization ACK signal completes the DLEP session establishment;
the sender of the signal should transition to an 'in-session' state
when the signal is sent, and the receiver should transition to the
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'in-session' state upon receipt (and successful parsing) of an
acceptable Peer Initialization ACK signal.
All supported metric data items MUST be included in the Peer
Initialization ACK signal, 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 signal containing a metric data item NOT included in the Peer
Initialization ACK signal 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 Peer Initialization ACK
signal, the receiver of the signal MUST conclude that there is NO
support for extensions in the sender.
If any experimental signals or data items are used by the
implementation, they MUST be enumerated in one or more Experimental
Definition data items. If there are no Experimental Definition data
items in a Peer Initialization ACK signal, the receiver of the signal
MUST conclude that NO experimental definitions are in use by the
sender.
After the Peer Initialization/Peer Initialization ACK signals have
been successfully exchanged, implementations MUST only use extensions
and experimental definitions that are supported by BOTH peers.
To construct a Peer Initialization ACK signal, the Signal Type value
in the signal header is set to DLEP_PEER_INIT_ACK in Table 1.
The Peer Initialization ACK signal MUST contain one of each of the
following data items:
o DLEP Version (Section 8.1)
o Heartbeat Interval (Section 8.6)
o Maximum Data Rate (Receive) (Section 8.14)
o Maximum Data Rate (Transmit) (Section 8.15)
o Current Data Rate (Receive) (Section 8.16)
o Current Data Rate (Transmit) (Section 8.17)
o Latency (Section 8.18)
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The Peer Initialization ACK signal 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 8.19)
o Resources (Transmit) (Section 8.20)
o Relative Link Quality (Receive) (Section 8.21)
o Relative Link Quality (Transmit) (Section 8.22)
The Peer Initialization ACK signal MAY contain one of each of the
following data items:
o Status (Section 8.2)
o Peer Type (Section 8.5)
o Extensions Supported (Section 8.7)
The Peer Initialization ACK signal MAY contain one or more of any of
the following data items, with different values:
o Experimental Definition (Section 8.8)
7.5. Peer Update Signal
A Peer Update signal 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
Peer Update signal 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 Peer Update signal 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
signal (Section 7.13) 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 Peer Update
Signal MUST be acknowledged with a Peer Update ACK signal
(Section 7.6).
If metrics are supplied with the Peer Update signal (e.g., Maximum
Data Rate), these metrics are considered to be modem-wide, and
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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 Peer Update signals. The sending of Peer Update signals
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 Peer Update signal, the Signal Type value in the
signal header is set to DLEP_PEER_UPDATE in Table 1.
The Peer Update signal MAY contain one of each of the following data
items:
o Maximum Data Rate (Receive) (Section 8.14)
o Maximum Data Rate (Transmit) (Section 8.15)
o Current Data Rate (Receive) (Section 8.16)
o Current Data Rate (Transmit) (Section 8.17)
o Latency (Section 8.18)
o Resources (Receive) (Section 8.19)
o Resources (Transmit) (Section 8.20)
o Relative Link Quality (Receive) (Section 8.21)
o Relative Link Quality (Transmit) (Section 8.22)
The Peer Update signal MAY contain one or more of the following data
items, with different values:
o IPv4 Address (Section 8.10)
o IPv6 Address (Section 8.11)
A Peer Update signal MUST be acknowledged by the receiver issuing a
Peer Update ACK signal (Section 7.6).
7.6. Peer Update ACK Signal
A Peer Update ACK signal MUST be sent by implementations to indicate
whether a Peer Update signal (Section 7.5) was successfully received.
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To construct a Peer Update ACK signal, the Signal Type value in the
signal header is set to DLEP_PEER_UPDATE_ACK in Table 1.
The Peer Update ACK signal MAY contain one of each of the following
data items:
o Status (Section 8.2)
A receiver of a Peer Update ACK signal without a Status data item
MUST behave as if a Status data item with code 'Success' had been
received.
7.7. Peer Termination Signal
A Peer Termination signal MUST be sent by a DLEP participant when the
router/modem session needs to be terminated. Implementations
receiving a Peer Termination signal MUST send a Peer Termination ACK
signal (Section 7.8) to confirm the termination process.
The receiver of a Peer Termination signal MUST release all resources
allocated for the router/modem session, and MUST eliminate all
destinations in the information base accessible via the router/modem
pair represented by the session. Router and modem state machines are
returned to the 'discovery' state. No Destination Down signals
(Section 7.11) are sent.
The sender of a Peer Termination signal is free to define its
heuristics in event of a timeout. It may resend the Peer Termination
or free resources and return to the 'discovery' state.
To construct a Peer Termination signal, the Signal Type value in the
signal header is set to DLEP_PEER_TERM in Table 1.
The Peer Termination signal MAY contain one of each of the following
data items:
o Status (Section 8.2)
A receiver of a Peer Termination signal without a Status data item
MUST behave as if a Status of 'Unknown reason for Peer Termination'
has been received.
A Peer Termination signal MUST be acknowledged by the receiver
issuing a Peer Termination ACK signal (Section 7.8).
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7.8. Peer Termination ACK Signal
A Peer Termination ACK signal MUST be sent by a DLEP peer in response
to a received Peer Termination signal (Section 7.7). Receipt of a
Peer Termination ACK signal completes the teardown of the router/
modem session.
To construct a Peer Termination ACK signal, the Signal Type value in
the signal header is set to DLEP_PEER_TERM_ACK in Table 1.
The Peer Termination ACK signal MAY contain one of each of the
following data items:
o Status (Section 8.2)
A receiver of a Peer Termination ACK signal without a Status data
item MUST behave as if a Status data item with status code 'Success',
implying graceful termination, had been received.
7.9. Destination Up Signal
A Destination Up signal 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 signal MUST be acknowledged by the receiver issuing
a Destination Up ACK signal (Section 7.10). The sender of the
Destination Up signal is free to define its retry heuristics in event
of a timeout. When a Destination Up signal 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 signal, the Signal Type value in the
signal header is set to DLEP_DEST_UP in Table 1.
The Destination Up signal MUST contain one of each of the following
data items:
o MAC Address (Section 8.9)
The Destination Up signal MAY contain one of each of the following
data items:
o Maximum Data Rate (Receive) (Section 8.14)
o Maximum Data Rate (Transmit) (Section 8.15)
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o Current Data Rate (Receive) (Section 8.16)
o Current Data Rate (Transmit) (Section 8.17)
o Latency (Section 8.18)
o Resources (Receive) (Section 8.19)
o Resources (Transmit) (Section 8.20)
o Relative Link Quality (Receive) (Section 8.21)
o Relative Link Quality (Transmit) (Section 8.22)
The Destination Up signal MAY contain one or more of the following
data items, with different values:
o IPv4 Address (Section 8.10)
o IPv6 Address (Section 8.11)
o IPv4 Attached Subnet (Section 8.12)
o IPv6 Attached Subnet (Section 8.13)
If the sender has IPv4 and/or IPv6 address information for a
destination it SHOULD include the relevant data items in the
Destination Up signal, reducing the need for the receiver to probe
for any address.
7.10. Destination Up ACK Signal
A DLEP participant MUST send a Destination Up ACK signal to indicate
whether a Destination Up signal (Section 7.9) was successfully
processed.
To construct a Destination Up ACK signal, the Signal Type value in
the signal header is set to DLEP_DEST_UP_ACK in Table 1.
The Destination Up ACK signal MUST contain one of each of the
following data items:
o MAC Address (Section 8.9)
The Destination Up ACK signal MAY contain one of each of the
following data items:
o Status (Section 8.2)
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A receiver of a Destination Up ACK signal without a Status data item
MUST behave as if a Status data item with status code 'Success' had
been received. Implementations are free to define retry heuristics
when receiving a Destination Up ACK signal indicating an error.
7.11. Destination Down Signal
A DLEP peer MUST send a Destination Down signal to report when a
destination (a remote node or a multicast group) is no longer
reachable. A Destination Down ACK signal (Section 7.12) MUST be sent
by the recipient of a Destination Down signal to confirm that the
relevant data has been removed from the information base. The sender
of the Destination Down signal is free to define its retry heuristics
in event of a timeout.
To construct a Destination Down signal, the Signal Type value in the
signal header is set to DLEP_DEST_DOWN in Table 1.
The Destination Down signal MUST contain one of each of the following
data items:
o MAC Address (Section 8.9)
7.12. Destination Down ACK Signal
A DLEP participant MUST send a Destination Down ACK signal to
indicate whether a received Destination Down signal (Section 7.11)
was successfully processed. If successfully processed, the sender of
the ACK MUST have removed all entries in the information base that
pertain to the referenced destination.
To construct a Destination Down ACK signal, the Signal Type value in
the signal header is set to DLEP_DEST_DOWN_ACK in Table 1.
The Destination Down ACK signal MUST contain one of each of the
following data items:
o MAC Address (Section 8.9)
The Destination Down ACK signal MAY contain one of each of the
following data items:
o Status (Section 8.2)
A receiver of a Destination Down ACK signal without a Status data
item MUST behave as if a Status data item with status code 'Success'
had been received. Implementations are free to define retry
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heuristics when receiving a Destination Down ACK signal indicating an
error.
7.13. Destination Update Signal
A DLEP participant SHOULD send the Destination Update signal 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 signal are:
o Change in link metrics (e.g., Data Rates)
o Layer 3 addressing change
To construct a Destination Update signal, the Signal Type value in
the signal header is set to DLEP_DEST_UPDATE in Table 1.
The Destination Update signal MUST contain one of each of the
following data items:
o MAC Address (Section 8.9)
The Destination Update signal MAY contain one of each of the
following data items:
o Maximum Data Rate (Receive) (Section 8.14)
o Maximum Data Rate (Transmit) (Section 8.15)
o Current Data Rate (Receive) (Section 8.16)
o Current Data Rate (Transmit) (Section 8.17)
o Latency (Section 8.18)
o Resources (Receive) (Section 8.19)
o Resources (Transmit) (Section 8.20)
o Relative Link Quality (Receive) (Section 8.21)
o Relative Link Quality (Transmit) (Section 8.22)
The Destination Update signal MAY contain one or more of the
following data items, with different values:
o IPv4 Address (Section 8.10)
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o IPv6 Address (Section 8.11)
o IPv4 Attached Subnet (Section 8.12)
o IPv6 Attached Subnet (Section 8.13)
7.14. Heartbeat Signal
A Heartbeat signal SHOULD be sent by a DLEP participant every N
seconds, where N is defined in the Heartbeat Interval data item of
the Peer Initialization signal (Section 7.3) or Peer Initialization
ACK signal (Section 7.4). Note that implementations setting the
Heartbeat Interval to 0 effectively set the interval to an infinite
value, therefore, in those cases, this signal SHOULD NOT be sent.
The signal 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 signal, the Signal Type value in the signal
header is set to DLEP_PEER_HEARTBEAT in Table 1.
There are no valid data items for the Heartbeat signal.
7.15. Link Characteristics Request Signal
The Link Characteristics Request signal 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 signal 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 ACK signal (Section 7.16) 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 ACK) from its partner.
The sender of a Link Characteristics Request signal MAY attach a
timer to the request using the Link Characteristics ACK Timer data
item. If a Link Characteristics ACK signal is received after the
timer expires, the sender MUST NOT assume that the request succeeded.
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Implementations are free to define their retry heuristics in event of
a timeout.
To construct a Link Characteristics Request signal, the Signal Type
value in the signal header is set to DLEP_LINK_CHAR_REQ in Table 1.
The Link Characteristics Request signal MUST contain one of each of
the following data items:
o MAC Address (Section 8.9)
The Link Characteristics Request signal MAY contain one of each of
the following data items:
o Link Characteristics ACK Timer (Section 8.23)
o Current Data Rate (Receive) (Section 8.16)
o Current Data Rate (Transmit) (Section 8.17)
o Latency (Section 8.18)
7.16. Link Characteristics ACK Signal
A DLEP participant MUST send a Link Characteristics ACK signal to
indicate whether a received Link Characteristics Request signal
(Section 7.15) was successfully processed. The Link Characteristics
ACK signal SHOULD contain a complete set of metric data items, and
MUST contain a full set (i.e. those declared in the Peer
Initialization ACK signal (Section 7.4)), 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 ACK signal 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' MUST be added to the signal.
To construct a Link Characteristics Request ACK signal, the Signal
Type value in the signal header is set to DLEP_LINK_CHAR_ACK in
Table 1.
The Link Characteristics ACK signal MUST contain one of each of the
following data items:
o MAC Address (Section 8.9)
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The Link Characteristics ACK signal SHOULD contain one of each of the
following data items:
o Maximum Data Rate (Receive) (Section 8.14)
o Maximum Data Rate (Transmit) (Section 8.15)
o Current Data Rate (Receive) (Section 8.16)
o Current Data Rate (Transmit) (Section 8.17)
o Latency (Section 8.18)
The Link Characteristics ACK signal MAY contain one of each of the
following data items:
o Resources (Receive) (Section 8.19)
o Resources (Transmit) (Section 8.20)
o Relative Link Quality (Receive) (Section 8.21)
o Relative Link Quality (Transmit) (Section 8.22)
o Status (Section 8.2)
A receiver of a Link Characteristics ACK signal without a Status data
item MUST behave as if a Status data item with status code 'Success'
had been received.
8. DLEP Data Items
Following is the list of MANDATORY 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.
The DLEP data items are:
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+------------+--------------------------------------+---------------+
| Data Item | Description | Section |
+------------+--------------------------------------+---------------+
| TBD | DLEP Version | Section 8.1 |
| TBD | Status | Section 8.2 |
| TBD | IPv4 Connection Point | Section 8.3 |
| TBD | IPv6 Connection Point | Section 8.4 |
| TBD | Peer Type | Section 8.5 |
| TBD | Heartbeat Interval | Section 8.6 |
| TBD | Extensions Supported | Section 8.7 |
| TBD | Experimental Definition | Section 8.8 |
| TBD | MAC Address | Section 8.9 |
| TBD | IPv4 Address | Section 8.10 |
| TBD | IPv6 Address | Section 8.11 |
| TBD | IPv4 Attached Subnet | Section 8.12 |
| TBD | IPv6 Attached Subnet | Section 8.13 |
| TBD | Maximum Data Rate (Receive) MDRR) | Section 8.14 |
| TBD | Maximum Data Rate (Transmit) (MDRT) | Section 8.15 |
| TBD | Current Data Rate (Receive) (CDRR) | Section 8.16 |
| TBD | Current Data Rate (Transmit) (CDRT) | Section 8.17 |
| TBD | Latency | Section 8.18 |
| TBD | Resources (Receive) (RESR) | Section 8.19 |
| TBD | Resources (Transmit) (REST) | Section 8.20 |
| TBD | Relative Link Quality (Receive) | Section 8.21 |
| | (RLQR) | |
| TBD | Relative Link Quality (Transmit) | Section 8.22 |
| | (RLQT) | |
| TBD | Link Characteristics ACK Timer | Section 8.23 |
+------------+--------------------------------------+---------------+
Table 2: DLEP Data Item Values
8.1. DLEP Version
The DLEP Version data item MUST appear in the Peer Discovery
(Section 7.1), Peer Offer (Section 7.2), Peer Initialization
(Section 7.3) and Peer Initialization ACK (Section 7.4) signals. The
Version data item is used to indicate the version of the protocol
running in the originator. A DLEP implementation SHOULD use this
information to decide if the potential session partner is running at
a supported level.
The DLEP Version 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 | Major Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minor Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 4
Major Version: The major version of the DLEP protocol, expressed as
an 16-bit unsigned integer.
Minor Version: The minor version of the DLEP protocol, expressed as
an 16-bit unsigned integer.
Support of this draft is indicated by setting the Major Version to
'1', and the Minor Version to '0' (i.e. Version 1.0).
8.2. Status
The Status data item MAY appear in the Peer Initialization ACK
(Section 7.4), Peer Termination (Section 7.7), Peer Termination ACK
(Section 7.8), Peer Update ACK (Section 7.6), Destination Up ACK
(Section 7.10), Destination Down ACK (Section 7.12) and Link
Characteristics ACK (Section 7.16) signals. For the Peer Termination
Signal (Section 7.7), the Status data item indicates a reason for the
termination. For all acknowledgement signals, the Status data item
is used to indicate the success or failure of the previously received
signal.
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
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Length: 1 + Length of text
Status Code: One of the codes defined below.
Text: UTF-8 encoded string, describing an problem, used for
implementation defined purposes. Since this field is used for a
description of the problem, 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 | Reason |
+----------------+-------+------------------------------------------+
| Success | 0 | The signal was processed successfully. |
| Unknown Signal | TBD | The signal was not recognized by the |
| | | implementation. |
| Invalid Data | TBD | One or more data items in the signal are |
| | | invalid, unexpected or duplicated. |
| Unexpected | TBD | The signal was not expected while the |
| Signal | | machine was in this state, e.g., a Peer |
| | | Initialization signal after session |
| | | establishment. |
| Request Denied | TBD | The receiver has not completed the |
| | | request. |
| Timed Out | TBD | The request could not be completed in |
| | | the time allowed. |
| Invalid | TBD | The destination provided in the signal |
| Destination | | does not match a previously announced |
| | | destination. For example, in the Link |
| | | Characteristic Request ACK signal |
| | | (Section 7.16). |
+----------------+-------+------------------------------------------+
8.3. IPv4 Connection Point
The IPv4 Connection Point data item MAY appear in the Peer Offer
signal (Section 7.2). 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.
The IPv4 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 | IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 11.7) to establish the TCP connection.
8.4. IPv6 Connection Point
The IPv6 Connection Point data item MAY appear in the Peer Offer
signal (Section 7.2). 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:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Address | TCP Port Number (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 16 (or 18 if TCP Port included)
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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 11.7) to establish the TCP connection.
8.5. Peer Type
The Peer Type data item MAY appear in the Peer Discovery
(Section 7.1), Peer Offer (Section 7.2), Peer Initialization
(Section 7.3) and Peer Initialization ACK (Section 7.4) signals. 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:
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.
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.
8.6. Heartbeat Interval
The Heartbeat Interval data item MUST appear in both the Peer
Initialization (Section 7.3) and Peer Initialization ACK
(Section 7.4) signals to indicate the Heartbeat timeout window to be
used by the sender.
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The Interval is used to specify a period (in seconds) for Heartbeat
signals (Section 7.14). By specifying an Interval value of 0,
implementations MAY indicate the desire to disable Heartbeat signals
entirely (i.e., the Interval is set to an infinite value). However,
it is strongly recommended that implementations use non-0 timer
values. Implementations MUST implement heuristics such that DLEP
signals sent/received reset the timer interval.
A DLEP session will be considered inactive, and MUST be torn down,
via the Peer Termination procedure, by an implementation detecting
that two (2) Heartbeat intervals have transpired without receipt of
any DLEP signals.
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
Interval: 0 = Do NOT use heartbeats on this DLEP session. Non-zero
= Interval, in seconds, for heartbeat signals.
8.7. Extensions Supported
The Extensions Supported data item MAY be used in both the Peer
Initialization and Peer Initialization ACK signals. 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.
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: Number of Extensions supported.
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Extension List: A list of extensions supported, identified by their
1-octet value as listed in the extensions registry.
8.8. Experimental Definition
The Experimental Definition data item MAY be used in both the Peer
Initialization and Peer Initialization ACK signals. The Experimental
Definition data item is used by the router and modem to indicate the
formats to be used for experimental signals and data items for the
given peer session. The formats are identified by using a string
that matches the 'name' given to the experiment.
The Experimental Definition 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 | Experiment Name |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: Length of the name string for the Experiment.
Experiment Name: UTF-8 encoded string, containing the name of the
experiment being implemented.
An implementation receiving this data item MUST compare the received
string to a list of experiments that it supports.
An implementation MUST NOT assume the Experiment Name field is NUL-
terminated.
8.9. MAC Address
The MAC address data item MUST appear in all destination-oriented
signals (i.e., Destination Up (Section 7.9), Destination Up ACK
(Section 7.10), Destination Down (Section 7.11), Destination Down ACK
(Section 7.12), Destination Update (Section 7.13), Link
Characteristics Request (Section 7.15), and Link Characteristics ACK
(Section 7.16)). 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 6 for EUI-48 format, or 8 for EUI-64 format
MAC Address: MAC Address of the destination.
8.10. IPv4 Address
The IPv4 Address data item MAY appear in the Peer Update
(Section 7.5), Destination Up (Section 7.9) and Destination Update
(Section 7.13) signals. When included in Destination signals, this
data item contains the IPv4 address of the destination. When
included in the Peer Update signal, 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
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.
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8.11. IPv6 Address
The IPv6 Address data item MAY appear in the Peer Update
(Section 7.5), Destination Up (Section 7.9) and Destination Update
(Section 7.13) signals. When included in Destination signals, this
data item contains the IPv6 address of the destination. When
included in the Peer Update signal, 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.
8.12. 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 7.9) and Destination Update (Section 7.13) signals. Once an
IPv4 Subnet has been declared on a device, the declaration can NOT be
withdrawn without terminating the destination (via the Destination
Down signal (Section 7.11)) and re-issuing the Destination Up signal.
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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.
8.13. 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 7.9) and Destination Update (Section 7.13) signals. As in
the case of the IPv4 attached Subnet data item above, once an IPv6
attached subnet has been declared, it can NOT be withdrawn without
terminating the destination (via the Destination Down signal
(Section 7.11)) and re-issuing the Destination Up signal.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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.
8.14. Maximum Data Rate (Receive)
The Maximum Data Rate (Receive) (MDRR) data item MUST appear in the
Peer Initialization ACK signal (Section 7.4), and MAY appear in the
Peer Update (Section 7.5), Destination Up (Section 7.9), Destination
Update (Section 7.13) and Link Characteristics ACK (Section 7.16)
signals 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) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MDRR (bps) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
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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.
8.15. Maximum Data Rate (Transmit)
The Maximum Data Rate (Transmit) (MDRT) data item MUST appear in the
Peer Initialization ACK signal (Section 7.4), and MAY appear in the
Peer Update (Section 7.5), Destination Up (Section 7.9), Destination
Update (Section 7.13) and Link Characteristics ACK (Section 7.16)
signals 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) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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.
8.16. Current Data Rate (Receive)
The Current Data Rate (Receive) (CDRR) data item MUST appear in the
Peer Initialization ACK signal (Section 7.4), and MAY appear in the
Peer Update (Section 7.5), Destination Up (Section 7.9), Destination
Update (Section 7.13) and Link Characteristics ACK (Section 7.16)
signals to indicate the rate at which the link is currently operating
for receiving traffic.
When used in the Link Characteristics Request signal (Section 7.15),
CDRR represents the desired receive rate, in bits per second, on the
link.
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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) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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.
8.17. Current Data Rate (Transmit)
The Current Data Rate Transmit (CDRT) data item MUST appear in the
Peer Initialization ACK signal (Section 7.4), and MAY appear in the
Peer Update (Section 7.5), Destination Up (Section 7.9), Destination
Update (Section 7.13), and Link Characteristics ACK (Section 7.16)
signals to indicate the rate at which the link is currently operating
for transmitting traffic.
When used in the Link Characteristics Request signal (Section 7.15),
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) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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.
8.18. Latency
The Latency data item MUST appear in the Peer Initialization ACK
signal (Section 7.4), and MAY appear in the Peer Update
(Section 7.5), Destination Up (Section 7.9), Destination Update
(Section 7.13), and Link Characteristics ACK (Section 7.16) signals
to indicate the amount of latency, in microseconds, on the link.
When used in the Link Characteristics Request signal (Section 7.15),
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 (cont.) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Latency (cont.) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
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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.
8.19. Resources (Receive)
The Resources (Receive) (RESR) data item MAY appear in the Peer
Initialization ACK signal (Section 7.4), Peer Update (Section 7.5),
Destination Up (Section 7.9), Destination Update (Section 7.13) and
Link Characteristics ACK (Section 7.16) signals 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
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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.
8.20. Resources (Transmit)
The Resources (Transmit) (REST) data item MAY appear in the Peer
Initialization ACK signal (Section 7.4), Peer Update (Section 7.5),
Destination Up (Section 7.9), Destination Update (Section 7.13) and
Link Characteristics ACK (Section 7.16) signals to indicate the
amount of resources for transmission (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.
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The Resources (Transmit) data item contains the following fields:
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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.
8.21. Relative Link Quality (Receive)
The Relative Link Quality (Receive) (RLQR) data item MAY appear in
the Peer Initialization ACK signal (Section 7.4), Peer Update
(Section 7.5), Destination Up (Section 7.9), Destination Update
(Section 7.13) and Link Characteristics ACK (Section 7.16) signals to
indicate the quality of the link for receiving data.
The Relative Link Quality (Receive) data item contains the following
fields:
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type| Length | RLQR |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
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.
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8.22. Relative Link Quality (Transmit)
The Relative Link Quality (Transmit) (RLQT) data item MAY appear in
the Peer Initialization ACK signal (Section 7.4), Peer Update
(Section 7.5), Destination Up (Section 7.9), Destination Update
(Section 7.13) and Link Characteristics ACK (Section 7.16) signals to
indicate the quality of the link for transmitting data.
The Relative Link Quality (Transmit) data item contains the following
fields:
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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.
8.23. Link Characteristics ACK Timer
The Link Characteristics ACK Timer data item MAY appear in the Link
Characteristics Request signal (Section 7.15) to indicate the desired
number of seconds the sender will wait for a response to the request.
If this data item is omitted, implementations supporting the Link
Characteristics Request SHOULD choose a default value.
The Link Characteristics ACK Timer data item contains the following
fields:
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type| Length | Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
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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.
9. Credit-Windowing
DLEP includes an OPTIONAL Protocol Extension for a credit-windowing
scheme analogous to the one documented in [RFC5578]. In this scheme,
traffic between the router and modem is treated as two unidirectional
windows. This document identifies these windows as the 'Modem
Receive Window' (MRW), and the 'Router Receive Window' (RRW).
If the OPTIONAL 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 to the modem.
Likewise, the router is responsible for granting credits on the RRW,
which allows the modem to send data 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.
Credits represent the number of octets, or an increment in the number
of octets, that MAY be sent on the given window. When the number of
available credits reaches 0, a sender MUST stop sending data, 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 8.7)
including the value DLEP_EXT_CREDITS (value TBD) in the appropriate
Peer Initialization or Peer Initialization ACK signal.
9.1. Credit-Windowing Signals
The credit-windowing extension introduces no additional DLEP signals.
However, if a peer has advertised during session initialization that
it supports the credit-windowing extension then the following DLEP
signals MAY contain additional credit-windowing data items:
9.1.1. Destination Up Signal
The Destination Up signal MAY contain one of each of the following
data items:
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o Credit Grant (Section 9.2.1)
If the Destination Up signal does not contain the Credit Grant data
item, credits MUST NOT be used for that destination.
9.1.2. Destination Up ACK Signal
If the corresponding Destination Up signal contained the Credit Grant
data item, the Destination Up ACK signal MUST contain one of each of
the following data items:
o Credit Window Status (Section 9.2.2)
9.1.3. Destination Update Signal
If the corresponding Destination Up signal contained the Credit Grant
data item, the Destination Update signal MUST contain one of each of
the following data items:
o Credit Window Status (Section 9.2.2)
If the corresponding Destination Up signal contained the Credit Grant
data item, the Destination Update signal MAY contain one of each of
the following data items:
o Credit Grant (Section 9.2.1)
o Credit Request (Section 9.2.3)
9.2. 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.
+------------+-----------------------+----------------+
| Data Item | Description | Section |
+------------+-----------------------+----------------+
| TBD | Credit Grant | Section 9.2.1 |
| TBD | Credit Window Status | Section 9.2.2 |
| TBD | Credit Request | Section 9.2.3 |
+------------+-----------------------+----------------+
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9.2.1. 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 7.9) and Destination Update
(Section 7.13) signals. 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 signal 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.
In the Destination Up signal, when credits are desired, the
originating peer MUST set the initial credit value of the window it
controls (i.e., the Modem Receive Window, or Router Receive Window)
to an initial, non-zero value. If the receiver of a Destination Up
signal with a Credit Grant data item supports credits, the receiver
MUST either reject the use of credits for this destination, via a
Destination Up ACK response containing a Status data item
(Section 8.2) with a status code of 'Request Denied', or set the
initial value from the data contained in the Credit Window Status
data item. If the initialization completes successfully, the
receiver MUST respond to the Destination Up signal with a Destination
Up ACK signal 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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
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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.
9.2.2. 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:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Modem Receive Window Value | Router 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 signal.
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 signal.
9.2.3. Credit Request
The Credit Request data item MAY be sent from either DLEP
participant, via the Destination Update signal (Section 7.13), 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 signal (Section 7.9) for this session
did NOT contain a Credit Window Status data item, indicating that
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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
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type| Length | Reserved, MUST|
| | | be set to 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBD
Length: 1
Reserved: This field is currently unused and MUST be set to 0.
10. Security Considerations
The protocol does not contain any mechanisms for security (e.g.,
authentication or encryption). The protocol assumes that any
security would be implemented in the underlying transport (for
example, by use of TLS or some other mechanism), and is therefore
outside the scope of this document.
11. IANA Considerations
This section specifies requests to IANA.
11.1. Registrations
This specification defines:
o A new repository for DLEP signals, with sixteen values currently
assigned.
o Reservation of numbering space for Experimental DLEP signals.
o A new repository for DLEP data items, with twenty-six values
currently assigned.
o Reservation of numbering space in the data items repository for
experimental data items.
o A new repository for DLEP status codes, with seven currently
assigned.
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o A new repository for DLEP extensions, with one value currently
assigned.
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.
11.2. Expert Review: Evaluation Guidelines
No additional guidelines for expert review are anticipated.
11.3. Signal Type Registration
A new repository must be created with the values of the DLEP signals.
All signal values are in the range [0..255].
Valid signals are:
o Peer Discovery
o Peer Offer
o Peer Initialization
o Peer Initialization ACK
o Peer Update
o Peer Update ACK
o Peer Termination
o Peer Termination ACK
o Destination Up
o Destination Up ACK
o Destination Down
o Destination Down ACK
o Destination Update
o Heartbeat
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o Link Characteristics Request
o Link Characteristics ACK
It is also requested that the repository contain space for
experimental signal types.
11.4. DLEP Data Item Registrations
A new repository for DLEP data items must be created.
All data item values are in the range [0..255].
Valid data items are:
o DLEP Version
o Status
o IPv4 Connection Point
o IPv6 Connection Point
o Peer Type
o Heartbeat Interval
o Extensions Supported
o Experimental Definition
o MAC Address
o IPv4 Address
o IPv6 Address
o IPv4 Attached Subnet
o IPv6 Attached Subnet
o Maximum Data Rate (Receive)
o Maximum Data Rate (Transmit)
o Current Data Rate (Receive)
o Current Data Rate (Transmit)
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o Latency
o Resources (Receive)
o Resources (Transmit)
o Relative Link Quality (Receive)
o Relative Link Quality (Transmit)
o Link Characteristics ACK Timer
o Credit Window Status
o Credit Grant
o Credit Request
It is also requested that the registry allocation contain space for
experimental data items.
11.5. DLEP Status Code Registrations
A new repository for DLEP status codes must be created.
All status codes are in the range [0..255].
Valid status codes are:
o Success (value 0)
o Unknown Signal
o Invalid Data
o Unexpected Signal
o Request Denied
o Timed Out
o Invalid Destination
11.6. DLEP Extensions Registrations
A new repository for DLEP extensions must be created.
All extension values are in the range [0..255].
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Valid extensions are:
o DLEP_EXT_CREDITS - Credit windowing
11.7. DLEP Well-known Port
It is requested that IANA allocate a well-known port number for DLEP
communication.
11.8. DLEP Multicast Address
It is requested that IANA allocate a multicast address for DLEP
discovery signals.
12. 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.
13. References
13.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
13.2. 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.
Appendix A. Peer Level Signal Flows
A.1. Discovery
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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.
A.2. Session Initialization
Router Modem Signal Description
========================================================================
| Router connects to discovered or
| pre-configured Modem Connection
|---------TCP connect----------> Point.
|
| Router sends Peer Initialization
|-------Peer Initialization----->| signal.
|
| Modem receives Peer Initialization
| signal.
|
| Modem sends Peer Initialization
| ACK, with compatible extensions,
|<----Peer Initialization ACK----| and Success status data item.
| |
|<<============================>>| Session established. Heartbeats
: : begin.
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A.3. Session Initialization - Refused
Router Modem Signal Description
========================================================================
| Router connects to discovered or
| pre-configured Modem Connection
|---------TCP connect----------> Point.
|
| Router sends Peer Initialization
|-------Peer Initialization----->| signal.
|
| Modem receives Peer Initialization
| signal, and will not support the
| advertised version, experiment or
| extensions.
|
| Modem sends Peer Initialization
| ACK, with 'Request Denied' status
|<----Peer Initialization ACK----| data item.
| |
| <---- TCP shutdown (send)-----| Modem closes TCP connection.
|
| Router receives negative Peer
| Initialization ACK, closes
|---------TCP close-----------> TCP connection.
|
||------------------------------|| Session not started.
A.4. Router Changes IP Addresses
Router Modem Signal Description
========================================================================
| Router sends Peer Update signal to
|--------Peer Update------------>| announce change of IP address
|
| Modem receives Peer Update signal
| and updates internal state.
|
|<-------Peer Update ACK---------| Modem sends Peer Update ACK.
A.5. Modem Changes Session-wide Metrics
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Router Modem Signal Description
========================================================================
| Modem sends Peer Update signal to
| announce change of modem-wide
|<--------Peer Update------------| metrics
|
| Router receives Peer Update signal
| and updates internal state.
|
|-------Peer Update ACK--------->| Router sends Peer Update ACK.
A.6. Router Terminates Session
Router Modem Signal Description
========================================================================
| Router sends Peer Termination
|-------Peer Termination-------->| signal with Status data item.
| |
|-------TCP shutdown (send)---> | Router stops sending signals.
|
| Modem receives Peer Termination,
| stops counting received heartbeats
| and stops sending heartbeats.
|
| Modem sends Peer Termination ACK
|<-----Peer Termination ACK------| with Status 'Success'.
| |
| <----TCP shutdown (send)------| Modem stops sending signals.
|
||------------------------------|| Session terminated.
A.7. Modem Terminates Session
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Router Modem Signal Description
========================================================================
| Modem sends Peer Termination
|<------Peer Termination---------| signal with Status data item.
| |
| <----TCP shutdown (send)------| Modem stops sending signals.
|
| Router receives Peer Termination,
| stops counting received heartbeats
| and stops sending heartbeats.
|
| Router sends Peer Termination ACK
|------Peer Termination ACK----->| with Status 'Success'.
| |
|-------TCP shutdown (send)---> | Router stops sending signals.
|
||------------------------------|| Session terminated.
A.8. Session Heartbeats
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Router Modem Signal Description
========================================================================
|----------Heartbeat------------>| Router sends heartbeat signal
|
| Modem resets heartbeats missed
| counter.
~ ~ ~ ~ ~ ~ ~
|----------[Any signal]--------->| When the Modem receives any signal
| from the Router.
|
| Modem resets heartbeats missed
| counter.
~ ~ ~ ~ ~ ~ ~
|<---------Heartbeat-------------| Modem sends heartbeat signal
|
| Router resets heartbeats missed
| counter.
~ ~ ~ ~ ~ ~ ~
|<---------[Any signal]----------| When the Router receives any
| signal from the Modem.
|
| Modem resets heartbeats missed
| counter.
A.9. Router Detects a Heartbeat timeout
Router Modem Signal Description
========================================================================
||<----------------------| Router misses a heartbeat
| ||<----------------------| Router misses too many heartbeats
|
|
|-------Peer Termination-------->| Router sends Peer Termination
| signal with 'Timeout' Status
| data item.
:
: Termination proceeds as above.
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A.10. Modem Detects a Heartbeat timeout
Router Modem Signal Description
========================================================================
|---------------------->|| Modem misses a heartbeat
|---------------------->|| | Modem misses too many heartbeats
|
|
|<-------Peer Termination--------| Modem sends Peer Termination
| signal with 'Timeout' Status
| data item.
:
: Termination proceeds as above.
Appendix B. Destination Specific Signal Flows
B.1. Common Destination Signaling
Router Modem Signal Description
========================================================================
| Modem detects a new logical
| destination is reachable, and
|<-------Destination Up----------| sends Destination Up signal.
|
|--------Destination Up ACK----->| Router sends Destination Up ACK.
~ ~ ~ ~ ~ ~ ~
| Modem detects change in logical
| destination metrics, and sends
|<-------Destination Update------| Destination Update signal.
~ ~ ~ ~ ~ ~ ~
| Modem detects change in logical
| destination metrics, and sends
|<-------Destination Update------| Destination Update signal.
~ ~ ~ ~ ~ ~ ~
| Modem detects logical destination
| is no longer reachable, and sends
|<-------Destination Down--------| Destination Down signal.
|
| Router receives Destination Down,
| updates internal state, and sends
|--------Destination Down ACK--->| Destination Down ACK signal.
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B.2. Multicast Destination Signaling
Router Modem Signal Description
========================================================================
| Router detects a new multicast
| destination is in use, and sends
|--------Destination Up--------->| Destination Up signal.
|
| Modem updates internal state to
| monitor multicast destination, and
|<-------Destination Up ACK------| sends Destination Up ACK.
~ ~ ~ ~ ~ ~ ~
| Modem detects change in multicast
| destination metrics, and sends
|<-------Destination Update------| Destination Update signal.
~ ~ ~ ~ ~ ~ ~
| Modem detects change in multicast
| destination metrics, and sends
|<-------Destination Update------| Destination Update signal.
~ ~ ~ ~ ~ ~ ~
| Router detects multicast
| destination is no longer in use,
|--------Destination Down------->| and sends Destination Down signal.
|
| Modem receives Destination Down,
| updates internal state, and sends
|<-------Destination Down ACK----| Destination Down ACK signal.
B.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 signal.
|
| Modem attempts to adjust link
| status to meet the received
| request, and sends a Link
| Characteristics Request ACK
|<---Link Char. Request ACK------| signal 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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