Dynamic Link Exchange Protocol (DLEP)
draft-ietf-manet-dlep-05
The information below is for an old version of the document.
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| Authors | Stan Ratliff , Cisco Cisco , Greg Harrison , Shawn Jury , Darryl Satterwhite | ||
| Last updated | 2014-02-10 | ||
| Replaces | draft-sratliff-manet-dlep | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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draft-ietf-manet-dlep-05
Mobile Ad hoc Networks Working S. Ratliff
Group B. Berry
Internet-Draft G. Harrison
Intended status: Standards Track S. Jury
Expires: August 14, 2014 Cisco Systems
D. Satterwhite
Broadcom
Febuary 10, 2014
Dynamic Link Exchange Protocol (DLEP)
draft-ietf-manet-dlep-05
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
forwarding 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 to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on August 14, 2014.
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Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Requirements . . . . . . . . . . . . . . . . . . . . . . . 8
2. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3. Credits . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4. Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5. Extensions to DLEP . . . . . . . . . . . . . . . . . . . . . . 10
6. Normal Session Flow . . . . . . . . . . . . . . . . . . . . . 11
6.1 DLEP Modem session flow - Discovery case . . . . . . . . . . 11
6.2 DLEP Modem session flow - Configured case . . . . . . . . . 11
6.3 DLEP Router session flow . . . . . . . . . . . . . . . . . 12
6.4 Common Session Flow . . . . . . . . . . . . . . . . . . . . 12
7. Mandatory Signals and Data Items . . . . . . . . . . . . . . . 13
8. Generic DLEP Message Definition . . . . . . . . . . . . . . . . 14
9. DLEP Data Items . . . . . . . . . . . . . . . . . . . . . . . . 15
9.1 DLEP Version . . . . . . . . . . . . . . . . . . . . . . . 16
9.2 DLEP Port . . . . . . . . . . . . . . . . . . . . . . . . . 17
9.3 Peer Type . . . . . . . . . . . . . . . . . . . . . . . . . 17
9.4 MAC Address . . . . . . . . . . . . . . . . . . . . . . . . 18
9.5 IPv4 Address . . . . . . . . . . . . . . . . . . . . . . . 18
9.6 IPv6 Address . . . . . . . . . . . . . . . . . . . . . . . 19
9.7 Maximum Data Rate (Receive) . . . . . . . . . . . . . . . . 20
9.8 Maximum Data Rate (Transmit) . . . . . . . . . . . . . . . 20
9.9 Current Data Rate (Receive) . . . . . . . . . . . . . . . . 21
9.10 Current Data Rate (Transmit) . . . . . . . . . . . . . . . 22
9.11 Expected Forwarding Time . . . . . . . . . . . . . . . . . 23
9.12 Latency . . . . . . . . . . . . . . . . . . . . . . . . . 23
9.13 Resources (Receive) . . . . . . . . . . . . . . . . . . . 24
9.14 Resources (Transmit) . . . . . . . . . . . . . . . . . . . 25
9.15 Relative Link Quality (Receive) . . . . . . . . . . . . . 25
9.16 Relative Link Quality (Transmit) . . . . . . . . . . . . . 26
9.17 Status . . . . . . . . . . . . . . . . . . . . . . . . . . 26
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9.18 Heartbeat Interval . . . . . . . . . . . . . . . . . . . . 27
9.19 Link Characteristics ACK Timer . . . . . . . . . . . . . . 28
9.20 Credit Window Status . . . . . . . . . . . . . . . . . . . 28
9.21 Credit Grant Request . . . . . . . . . . . . . . . . . . . 29
9.22 Credit Request . . . . . . . . . . . . . . . . . . . . . . 30
10. DLEP Protocol Messages . . . . . . . . . . . . . . . . . . . . 31
10.1 Signal TLV Values . . . . . . . . . . . . . . . . . . . . 31
10.2 Peer Discovery Message . . . . . . . . . . . . . . . . . . 32
10.3 Peer Offer Message . . . . . . . . . . . . . . . . . . . . 32
10.4 Peer Initialization Message . . . . . . . . . . . . . . . . 33
10.5 Peer Initialization ACK Message . . . . . . . . . . . . . . 33
10.6 Peer Update Message . . . . . . . . . . . . . . . . . . . . 34
10.7 Peer Update ACK Message . . . . . . . . . . . . . . . . . . 35
10.8 Peer Termination Message . . . . . . . . . . . . . . . . . 35
10.9 Peer Termination ACK Message . . . . . . . . . . . . . . . 36
10.10 Destination Up Message . . . . . . . . . . . . . . . . . . 36
10.11 Destination Up ACK Message . . . . . . . . . . . . . . . . 37
10.12 Destination Down Message . . . . . . . . . . . . . . . . . 37
10.13 Destination Down ACK Message . . . . . . . . . . . . . . . 37
10.14 Destination Update Message . . . . . . . . . . . . . . . . 38
10.15 Heartbeat Message . . . . . . . . . . . . . . . . . . . . 38
10.16 Link Characteristics Request Message . . . . . . . . . . . 39
10.17 Link Characteristics ACK Message . . . . . . . . . . . . . 40
11. Security Considerations . . . . . . . . . . . . . . . . . . . 40
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 40
12.1 Registrations . . . . . . . . . . . . . . . . . . . . . . 41
12.2 Expert Review: Evaluation Guidelines . . . . . . . . . . . 41
12.3 Message (Signal) TLV Type Registration . . . . . . . . . . 41
12.4 DLEP Data Item Registrations . . . . . . . . . . . . . . . 42
12.5 DLEP Well-known Port . . . . . . . . . . . . . . . . . . . 42
12.6 DLEP Multicast Address . . . . . . . . . . . . . . . . . . 42
13. Appendix A. . . . . . . . . . . . . . . . . . . . . . . . . . 42
13.1 Peer Level Message Flows . . . . . . . . . . . . . . . . . 42
13.1.1 Modem Device Restarts Discovery . . . . . . . . . . . 43
13.1.2 Modem Device Detects Peer Offer Timeout . . . . . . . 43
13.1.3 Router Peer Offer Lost . . . . . . . . . . . . . . . . 44
13.1.4 Discovery Success . . . . . . . . . . . . . . . . . . 44
29.1.5 Router Detects a Heartbeat timeout . . . . . . . . . . 45
29.1.6 Modem Detects a Heartbeat timeout . . . . . . . . . . 45
29.1.7 Peer Terminate (from Modem) Lost . . . . . . . . . . . 46
29.1.8 Peer Terminate (from Router) Lost . . . . . . . . . . 46
29.2 Destination Specific Message Flows . . . . . . . . . . . . 46
29.2.1 Modem Destination Up Lost . . . . . . . . . . . . . . 47
29.2.2 Router Detects Duplicate Destination Ups . . . . . . . 47
29.2.3 Destination Up, No Layer 3 Addresses . . . . . . . . . 48
29.2.4 Destination Up with IPv4, No IPv6 . . . . . . . . . . 48
29.2.5 Destination Up with IPv4 and IPv6 . . . . . . . . . . 48
29.2.6 Destination Session Success . . . . . . . . . . . . . 49
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Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . 49
Normative References . . . . . . . . . . . . . . . . . . . . . . . 50
Informative References . . . . . . . . . . . . . . . . . . . . . . 50
Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . . 50
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) radios, satellite terminals, and
cable/DSL modems. Fluctuations in speed and quality of these links
can occur due to configuration (in the case of cable/DSL modems), 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 varies with respect to individual
destinations on a link, and with the type of traffic being sent. As
an example, consider the case of an 802.11g access point, serving 2
associated laptop computers. In this environment, the answer to the
question "What is the datarate on the 802.11g 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. Effectively utilizing a relatively short-lived connection is
problematic in IP routed networks, as routing protocols tend to rely
on independent timers at OSI Layer 3 to maintain network convergence
(e.g. HELLO messages and/or recognition of DEAD routing adjacencies).
These short-lived 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 timer-driven paradigm.
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, USB, or
even a serial link. In the case of Ethernet or serial 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
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awareness, along with the variability in datarate, leads to a
situation where quality of service (QoS) profiles are extremely
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 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 authors have developed
the Data Link Exchange Protocol, or DLEP. The DLEP protocol runs
between a router and its attached modem devices, allowing the modem
to communicate link characteristics as they change, and convergence
events (acquisition and loss of potential routing destinations). The
following diagrams are used to illustrate the scope of DLEP packets.
|-------Local Node-------| |-------Remote Node------|
| | | |
+--------+ +-------+ +-------+ +--------+
| Router |=======| Modem |{~~~~~~~~}| Modem |=======| Router |
| | | Device| | Device| | |
+--------+ +-------+ +-------+ +--------+
| | | Link | | |
|-DLEP--| | Protocol | |-DLEP--|
| | | (e.g. | | |
| | | 802.11) | | |
Figure 1: DLEP Network
In Figure 1, when the local modem detects the presence of a remote
node, it (the local modem) sends a signal to its router via the DLEP
protocol. 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 utilize DLEP to
report any characteristics of the link (datarate, latency, etc) that
have changed. DLEP is independent of the link type and topology
supported by the modem. Note that the DLEP protocol is specified to
run only on the local link between router and modem. Some over the
air signaling may be necessary between the local and remote modem in
order to provide some parameters in DLEP messages between the local
modem and local router, but DLEP does not specify how such over the
air signaling is carried out. Over the air signaling is purely a
matter for the modem implementer.
Figure 2 shows how DLEP can support a configuration where routers are
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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.
+--------+ +--------+
+----+ 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
DLEP defines a set of messages used by modems and their attached
routers. The messages are used to communicate events that occur on
the physical link(s) managed by the modem: for example, a remote node
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entering or leaving the network, or that the link has changed.
Associated with these messages are a set of data items - information
that describes the remote node (e.g., address information), and/or
the characteristics of the link to the remote node.
The protocol is defined as a collection of type-length-value (TLV)
based messages, 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.
DLEP signals are further defined as mandatory or optional. Signals
will additionally have mandatory and optional data items.
Implementations MUST support all mandatory messages and their
mandatory data items to be considered compliant. Implementations MAY
also support some, or all, of the optional messages and data items.
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), a separate DLEP session MUST exist for each
modem. If a modem device supports multiple connections to a router
(via multiple logical or physical interfaces), or supports
connections to multiple routers, a separate DLEP session MUST exist
for each 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 neighbor. The
modem, once it is aware of the existence of this logical neighbor,
reports link characteristics just as it would for any other
destination in the network. The specific algorithms a modem would use
to report metrics on multicast (or logical) destinations is outside
the scope of this specification, and is left to specific
implementations to decide.
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1.1 Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD 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 utilize a discovery technique to locate
each other, thus avoiding a-priori configuration. The modem is
responsible for initialing the discovery process, using the Peer
Discovery message.
DLEP utilizes a session-oriented paradigm. A router and modem form a
session by completing the discovery 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 DLEP is OPTIONAL,
it is strongly recommended that implementations choose to run with
timers enabled.
DLEP assumes that participating modems, and their physical links, act
as a transparent bridge. Specifically, the assumption is that the
destination MAC address for data traffic in any frame emitted by the
router should be the MAC address of a device in the remote node. DLEP
also assumes that MAC addresses are unique within the context of the
router-modem session.
This document refers to a remote node as a "Destination".
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).
Destinations MAY refer either to physical devices in the network, or
to logical destinations, as in a multicast group. As "destinations"
are discovered, DLEP routers and modems build an information base on
destinations accessible via the modem. Changes in link
characteristics MAY then be reported as being "modem-wide" (effecting
ALL destinations accessed via the modem) or MAY be neighbor
(destination) specific.
The DLEP messages concerning destinations thus become the way for
routers and modems to maintain, and notify each other about, an
information base representing the physical and logical (e.g.,
multicast) destinations accessible via the modem device. The
information base would contain addressing information (e.g., MAC
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address, and OPTIONALLY, Layer 3 addresses), link characteristics
(metrics), and OPTIONALLY, flow control information (credits).
DLEP assumes that security on the session (e.g. authentication of
session partners, encryption of traffic, or both) is dealt with by
the underlying transport mechanism (e.g., by using a transport such
as TLS [TLS]).
This document specifies an implementation of the DLEP messages and
data items running over the TCP transport, utilizing a well-known TCP
Port number. It is assumed that DLEP running over other transport
mechanisms would be documented separately.
3. Credits
DLEP includes an OPTIONAL 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", or
MRW, and the "Router Receive Window", or RRW.
If credits are used, they 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.
DLEP expresses all credit data in number of octets. The total number
of credits on a window, and the increment to add to a grant, are
always expressed as a 64-bit unsigned quantity.
If used, credits are managed on a neighbor-specific basis; that is,
separate credit counts are maintained for each neighbor requiring the
service. Credits do not apply to the DLEP session that exists between
routers and modems.
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.
As mentioned in the introduction section of this document, metrics
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have to be used within a context - for example, metrics to a unicast
address in the network. 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 the modem). Metrics are further subdivided
into transmit and receive metrics. Metrics supplied on DLEP Peer
signals are, by definition, modem-wide; metrics supplied on
Destination messages signals are, by definition, used for the
specific neighbor only.
DLEP modem implementations MUST announce all supported metric items,
and provide default values for those metrics, in the Peer
Initialization message. In order to introduce a new metric type, DLEP
modem implementations MUST terminate the session with the router (via
the Peer Terminate message), and re-establish the session.
It is left to implementations to choose sensible default values based
on their specific characteristics. Modems having static (non-
changing) link metric characteristics MAY report metrics only once
for a given neighbor (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 is out of scope and not addressed
by this document.
5. Extensions to DLEP
While this draft represents the best efforts of the co-authors, and
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 utilized. To allow for future innovation, the draft
allocates numbering space for experimental implementations of both
signals and data items.
DLEP implementations MUST be capable of parsing and acting on the
mandatory messages and data items as documented in this
specification. DLEP messages/data items that are optional, or are in
the experimental numbering range SHOULD be silently dropped by an
implementation if they are not understood.
The intent of the optional messages and data items, as well as the
experimental numbering space, is to allow for further development of
DLEP protocol features and function. Having experimental space
reserved for both signals and data items gives maximum flexibility
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for extending the protocol as conditions warrant. For example,
experimental data items could be used by implementations to send
additional metrics. A combination of experimental messages, and
associated data items, could be used to implement new flow control
schemes. If subsequent research and development define new features
and function, then it should be standardized either as an update to
this document, or as an additional stand-alone specification.
6. Normal Session Flow
Normal session flow is slightly different, depending on whether the
implementation represents a modem or a router, and whether discovery
techniques are used. The normal flow by DLEP partner type is:
6.1 DLEP Modem session flow - Discovery case
If the DLEP modem 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 message to the DLEP link-local multicast address and
port (TBD). The implementation then waits on receipt of a Peer Offer
message, which MUST contain the unicast address and port for TCP-
based communication with a DLEP router. The Peer Offer message MAY
contain multiple address/port combinations. If more than one
address/port combination is in the Peer Offer, the DLEP modem
implementation SHOULD consider the list to be in priority sequence,
with the "most desired" address/port combination listed first.
However, modem implementations MAY use their own heuristics to
determine the best address/port combination. At this point, the modem
implementation MAY either destroy the UDP socket, or continue to
issue Peer Discovery messages to the link-local address/port
combination. In either case, the TCP session initialization occurs as
in the configured case.
6.2 DLEP Modem session flow - Configured case
When a DLEP modem implementation has the address and port information
for a TCP connection to the router (obtained either via configuration
or via the discovery process described above), the modem will
initialize and bind a TCP socket. This socket is used to connect to
the DLEP router software. After a successful TCP connect, the modem
implementation MUST issue a Peer Initialization message to the DLEP
router. The Peer Initialization message MUST contain TLVs for ALL
supported metrics from this modem (e.g. all MANDATORY metrics plus
all OPTIONAL metrics supported by the implementation), along with the
default values of those metrics. After sending the Peer
Initialization, the modem implementation should wait for receipt of a
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Peer Initialization ACK message from the router. Receipt of the Peer
Initialization ACK indicates that the router has received and
processed the Peer Initialization, and the session MUST transition to
the "in session" state. At this point, messages regarding
destinations in the network, and/or Peer Update messages, can flow on
the DLEP session between modem and router. The "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.
6.3 DLEP Router session flow
DLEP router 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 router implementation receives a Peer Discovery message on
the UDP socket, it responds by issuing a Peer Offer message to the
sender of the Peer Discovery. The Peer Offer message MUST contain the
unicast address and port of the TCP listen socket, described above. A
DLEP router implementation MAY respond with ALL address/port
combinations that have an active TCP listen posted. If multiple
address/port combinations are listed, the receiver of the Peer Offer
MAY connect on any available address/port pair. Anything other than
Peer Discovery messages received on the UDP socket MUST be silently
dropped.
When the DLEP router implementation accepts a connection via TCP, it
will wait for receipt of a Peer Initialization message. The received
Peer Initialization MUST contain metric TLVs for ALL mandatory
metrics, and MUST contain metric TLVs for ANY optional metrics
supported by the modem. If a new 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 message.
6.4 Common Session Flow
In order to maintain the session between router and modem, periodic
"Heartbeat" messages SHOULD be exchanged. These messages are intended
to keep the session alive, and to verify bidirectional connectivity
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between the two participants. DLEP also provides for an OPTIONAL Peer
Update message, 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 messages above, the participants will transmit
DLEP messages concerning destinations in the network. These messages
trigger creation/maintenance/deletion of destinations in the
information base of the recipient. For example, a modem will inform
its attached router of the presence of a new destination via the
"Destination Up" signal. Receipt of a Destination Up causes the
router to allocate the necessary resources, creating an entry in the
information base with the specifics (e.g., MAC Address, Latency, Data
Rate, etc) of the neighbor. The loss of a destination is communicated
via the "Neighbor Down" signal, and changes in status to the
destination (e.g. varying link quality, or addressing changes) are
communicated via the "Neighbor Update" signal. The information on a
given neighbor will persist in the router's information base until
(1) a "Neighbor Down" 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.
Again, metrics can be expressed within the context of a specific
neighbor via the Neighbor Update message, or on a modem-wide basis
via the Peer Update message. In cases where metrics are provided on
the router/modem session, the receiver MUST propagate the metrics to
all destinations in its information base that are accessed via the
originator. A DLEP participant MAY send metrics both in a
router/modem session context (via the Peer Update message) and a
specific neighbor context (via Neighbor Update) at any time. The
heuristics for applying received metrics is left to implementations.
In addition to receiving metrics about the link, DLEP provides an
OPTIONAL signal allowing a router to request a different datarate, or
latency, from the modem. This signal is referred to as the Link
Characteristics Message, 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.
7. Mandatory Signals and Data Items
The following DLEP signals are considered core to the specification;
implementations MUST support these signals, and the associated data
items, in order to be considered compliant:
Signal Data Items
====== ==========
Peer Discovery (Modem Only) DLEP Version
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Peer Offer (Router Only) DLEP Version
IPv4 or IPv6 address(es)
DLEP Port
Peer Initialization DLEP Version
Maximum Data Rate (Receive)
Maximum Data Rate (Transmit)
Current Data Rate (Receive)
Current Data Rate (Transmit)
Latency
Relative Link Quality (Receive)
Relative Link Quality (Transmit)
Peer Initialization ACK Status
Peer Termination None
Peer Termination ACK Status
Destination Up MAC Address
Maximum Data Rate (Receive)
Maximum Data Rate (Transmit)
Current Data Rate (Receive)
Current Data Rate (Transmit)
Latency
Relative Link Quality (Receive)
Relative Link Quality (Transmit)
Destination Update MAC Address
Maximum Data Rate (Receive)
Maximum Data Rate (Transmit)
Current Data Rate (Receive)
Current Data Rate (Transmit)
Latency
Relative Link Quality (Receive)
Relative Link Quality (Transmit)
Destination Down MAC Address
All other DLEP signals and data items are OPTIONAL. Implementations
MAY choose to provide them. Implementations that do not support
optional signals and data items SHOULD parse, and silently drop, all
unsupported messages and/or data items.
8. Generic DLEP Message Definition
The Generic DLEP Message consists of a sequence of TLVs. The first
TLV represents the signal being communicated (e.g., a "Destination
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Up", or a "Peer Offer"). Subsequent TLVs contain the data items
pertinent to the signal (e.g., Maximum Data Rate, or Latency, etc).
The Generic DLEP Packet Definition 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Signal TLV Type | Length | DLEP data items... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Signal - One of the DLEP Message TLV type values
defined in this document.
Length - The length, expressed as a 16-bit
quantity, of all of the DLEP data items
associated with this signal.
DLEP data items - One or more data items, encoded in TLVs,
as defined in this document.
9. DLEP Data Items
As mentioned earlier, DLEP protocol messages are transported as a
collection of TLVs. The first TLV present in a DLEP message MUST be
one of the Signal TLVs, documented in section 10. The signals are
followed by one or more data items, indicating the specific changes
that need to be instantiated in the receiver's information base.
Valid DLEP Data Items are:
TLV TLV
Value Description
=========================================
TBD DLEP Version
TBD DLEP Port
TBD Peer Type
TBD IPv4 Address
TBD IPv6 Address
TBD Maximum Data Rate (Receive) (MDRR)
TBD Maximum Data Rate (Transmit) (MDRT)
TBD Current Data Rate (Receive) (CDRR)
TBD Current Data Rate (Transmit) (CDRT)
TBD Latency
TBD Receive Resources
TBD Transmit Resources
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TBD Expected Forwarding Time (EFT)
TBD Relative Link Quality (Receive) (RLQR)
TBD Relative Link Quality (Transmit) (RLQT)
TBD Status
TBD Heartbeat Interval/Threshold
TBD Neighbor down ACK timer
TBD Link Characteristics ACK timer
TBD Credit Window Status
TBD Credit Grant
TBD Credit Request
DLEP data item TLVs 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV Type | Length | Value... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - An 8-bit unsigned integer field specifying the data
item being sent.
Length - An 8-bit length of the value field of the data item
Value - A field of length <Length> which contains data
specific to a particular data item.
9.1 DLEP Version
The DLEP Version TLV is a MANDATORY TLV in Peer Discovery, Peer
Offer, and Peer Initialization messages. The Version TLV is used to
indicate the version of the protocol running in the sender. The
receiver SHOULD use this information to decide if the potential
session partner is running at a supported level.
The DLEP Version TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length=4 | Major Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minor Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
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Length - Length is 4
Major Version - Major version of the modem or router protocol.
Minor Version - Minor version of the modem or router protocol.
Support of this draft is indicated by setting the Major Version
to '1', and the Minor Version to '5' (i.e. Version 1.5).
9.2 DLEP Port
The DLEP Port TLV is a MANDATORY TLV in the Peer Offer message. The
DLEP Port TLV is used to indicate the TCP Port number on the DLEP
server available for connections. The receiver MUST use this
information to perform the TCP connect to the DLEP server.
The DLEP Port TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length=2 | TCP Port Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
Length - Length is 2
TCP Port Number - TCP Port number on the DLEP server.
Minor Version - Minor version of the modem or router protocol.
9.3 Peer Type
The Peer Type TLV is an OPTIONAL TLV in both the Peer Discovery and
Peer Offer messages. The Peer Type TLV 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 TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length= peer |Peer Type String |
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| |type string len| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
Length - Length of peer type string.
Peer Type String - Non-Null terminated string, using UTF-8 encoding.
For example, a satellite modem might set this
variable to 'Satellite terminal'.
9.4 MAC Address
The MAC address TLV MUST appear in all destination-oriented signals
(e.g. Destination Up, Destination Up ACK, Destination Down,
Destination Down ACK, Destination Update, Link Characteristics
Request, and Link Characteristics ACK). The MAC Address TLV contains
the address of the destination on the remote node. The MAC address
MAY be either a physical or a virtual destination. Examples of a
virtual destination would be a multicast MAC address, or the
broadcast MAC (0xFFFFFFFFFFFF).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length = 6 | MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
Length - 6
MAC Address - MAC Address of the destination (either physical or
virtual).
9.5 IPv4 Address
The IPv4 Address TLV is an OPTIONAL TLV. If supported, it MAY appear
in Destination Up, Destination Update, and Peer Update messages. When
included in Destination messages, the IPv4 Address TLV contains the
IPv4 address of the destination, as well as a subnet mask value. In
the Peer Update message, it contains the IPv4 address of the
originator of the message. In either case, the TLV also contains an
indication of whether this is a new or existing address, or is a
deletion of a previously known address.
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The IPv4 Address TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length = 6 | Add/Drop | IPv4 Address |
| | | Indicator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address | Subnet Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
Length - 6
Add/Drop - Value indicating whether this is a new or existing
address (0x01), or a withdrawal of an address (0x02).
IPv4 Address - The IPv4 address of the destination or peer.
Subnet Mask - A subnet mask (0-32) to be applied to the IPv4
address.
9.6 IPv6 Address
The IPv6 Address TLV is an OPTIONAL TLV. If supported, it MAY be used
in the Destination Up, Destination Update, Peer Discovery, and Peer
Update Messages. When included in Destination messages, this data
item contains the IPv6 address of the destination. In the Peer
Discovery and Peer Update, it contains the IPv6 address of the
originating 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, as well as a subnet mask.
The IPv6 Address TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length = 18 | Add/Drop | IPv6 Address |
| | | Indicator | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Address |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Address | Subnet Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
Length - 18
Add/Drop - Value indicating whether this is a new or existing
address (0x01), or a withdrawal of an address (0x02).
IPv6 Address - IPv6 Address of the destination or peer.
Subnet Mask - A subnet mask value (0-128) to be applied to the Ipv6
address.
9.7 Maximum Data Rate (Receive)
The Maximum Data Rate Receive (MDRR) TLV is used in Destination Up,
Destination Update, Peer Discovery, Peer Update, and Link
Characteristics ACK Messages to indicate the maximum theoretical data
rate, in bits per second, that can be achieved while receiving data
on the link. When metrics are reported via the messages listed above,
the maximum data rate receive MUST be reported.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length = 8 | MDRR (bps) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MDRR (bps) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MDRR (bps) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
Length - 8
Maximum Data Rate Receive - A 64-bit unsigned number, representing
the maximum theoretical data rate, in bits per
second (bps), that can be achieved while
receiving on the link.
9.8 Maximum Data Rate (Transmit)
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The Maximum Data Rate Transmit (MDRT) TLV is used in Destination Up,
Destination Update, Peer Discovery, Peer Update, and Link
Characteristics ACK Messages to indicate the maximum theoretical data
rate, in bits per second, that can be achieved while transmitting
data on the link. When metrics are reported via the messages listed
above, the maximum data rate transmit MUST be reported.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length = 8 | MDRT (bps) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MDRT (bps) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MDRT (bps) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
Length - 8
Maximum Data Rate Transmit - A 64-bit unsigned number, representing
the maximum theoretical data rate, in bits per
second (bps), that can be achieved while
transmitting on the link.
9.9 Current Data Rate (Receive)
The Current Data Rate Receive (CDRR) TLV is used in Destination Up,
Destination Update, Peer Discovery, Peer Update, Link Characteristics
Request, and Link Characteristics ACK messages to indicate the rate
at which the link is currently operating for receiving traffic. The
Current Data Rate Receive is a MANDATORY data item. In the case of
the Link Characteristics Request, CDRR represents the desired receive
data rate for the link. When metrics are reported via the messages
above (e.g. Destination Update), the current data rate receive MUST
be reported.
The Current Data Rate Receive TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |TLV Flags=0x10 |Length = 8 |CDRR (bps) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CDRR (bps) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| CDRR (bps) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
Length - 8
Current Data Rate Receive - A 64-bit unsigned number, representing
the current data rate, in bits per second, that
is currently be achieved while receiving traffic
on the link. When used in the Link
Characteristics Request, CDRR represents the
desired receive rate, in bits per second, on the
link. If there is no distinction between current
and maximum receive data rates, current data
rate receive SHOULD be set equal to the maximum
data rate receive.
9.10 Current Data Rate (Transmit)
The Current Data Rate Receive (CDRT) TLV is used in Destination Up,
Destination Update, Peer Discovery, Peer Update, Link Characteristics
Request, and Link Characteristics ACK messages to indicate the rate
at which the link is currently operating for transmitting traffic.
Current Data Rate Transmit is a MANDATORY data item. In the case of
the Link Characteristics Request, CDRT represents the desired
transmit data rate for the link. When metrics are reported via the
messages above (e.g. Destination Update), the current data rate
transmit MUST be reported.
The Current Data Rate Transmit TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |TLV Flags=0x10 |Length = 8 |CDRT (bps) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CDRT (bps) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CDRT (bps) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
Length - 8
Current Data Rate Transmit - A 64-bit unsigned number, representing
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the current data rate, in bits per second, that
is currently be achieved while transmitting
traffic on the link. When used in the Link
Characteristics Request, CDRT represents the
desired transmit rate, in bits per second, on
the link. If there is no distinction between
current and maximum transmit data rates, current
data rate transmit MUST be set equal to the
maximum data rate transmit.
9.11 Expected Forwarding Time
The Expected Forwarding Time (EFT) TLV is is an OPTIONAL data item.
If supported, it MAY be used in Destination Up, Destination Update,
Peer Discovery, and Peer Update messages to indicate the typical
latency between the arrival of a given packet at the transmitting
device and the reception of the packet at the other end of the link.
EFT combines transmission time, idle time, waiting time, freezing
time, and queuing time to the degree that those values are meaningful
to a given transmission medium.
The Expected Forwarding Time TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length = 4 | EFT (ms) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EFT (ms) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
Length - 4
EFT - A 32-bit unsigned number, representing the expected
forwarding time, in milliseconds, on the link.
9.12 Latency
The Latency TLV is an MANDATORY data item. It is used in Peer
Initialization, Destination Up, Destination Update, Peer Discovery,
Peer Update, Link Characteristics Request, and Link Characteristics
ACK messages to indicate the amount of latency on the link, or in the
case of the Link Characteristics Request, to indicate the maximum
latency required on the link.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length = 2 | Latency (ms) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
Length - 2
Latency - A 16-bit unsigned value, representing the transmission
delay that a packet encounters as it is transmitted
over the link. In Destination Up, Destination Update,
and Link Characteristics ACK, this value is reported
as delay, in milliseconds. The calculation of latency
is implementation dependent. For example, the latency
may be a running average calculated from the internal
queuing. If a device cannot calculate latency, this
TLV SHOUD NOT be issued. In the Link Characteristics
Request Message, this value represents the maximum
delay, in milliseconds, expected on the link.
9.13 Resources (Receive)
The Receive Resources TLV is an OPTIONAL data item. If supported, it
is used in Destination Up, Destination Update, Peer Discovery, Peer
Update, and Link Characteristics ACK messages to indicate a
percentage (0-100) amount of resources (e.g. battery power),
committed to receiving data, remaining on the originating peer.
The Resources TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length = 1 | Rcv Resources|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
Length - 1
Receive Resources - A percentage, 0-100, representing the amount
of remaining resources, such as battery power,
allocated to receiving data. If a device cannot
calculate receive resources, this TLV SHOULD NOT be
issued.
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9.14 Resources (Transmit)
The Transmit Resources TLV is an OPTIONAL data item. If supported, it
is used in Destination Up, Destination Update, Peer Discovery, Peer
Update, and Link Characteristics ACK messages to indicate a
percentage (0-100) amount of resources (e.g. battery power),
committed to transmitting data, remaining on the originating peer.
The Resources TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length = 1 | Xmt Resources|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
Length - 1
Transmit Resources - A percentage, 0-100, representing the amount
of remaining resources, such as battery power,
allocated to transmitting data. If the transmit
resources cannot be calculated, then the TLV SHOULD
NOT be issued.
9.15 Relative Link Quality (Receive)
The Relative Link Quality Receive (RLQR) TLV is a MANDATORY data
item. If supported, it is used in Peer Initialization, Destination
Up, Destination Update, Peer Discovery, Peer Update, and Link
Characteristics ACK messages to indicate the quality of the link for
receiving data as calculated by the originating peer.
The Relative Link Quality (Receive) TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length = 1 |RCV Rel. Link |
| | |Quality (RLQR) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
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Length - 1
Relative Link Quality (Receive) - A non-dimensional number, 1-100,
representing relative link quality. A value of
100 represents a link of the highest quality.
If a device cannot calculate the RLQR, this
TLV SHOULD NOT be issued.
9.16 Relative Link Quality (Transmit)
The Transmit Link Quality Receive (RLQT) TLV is a MANDATORY data
item. It is used in Peer Initialization, Destination Up, Destination
Update, Peer Discovery, Peer Update, and Link Characteristics ACK
messages to indicate the quality of the link for transmitting data as
calculated by the originating peer.
The Relative Link Quality (Transmit) TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length = 1 |XMT Rel. Link |
| | |Quality (RLQR) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
Length - 1
Relative Link Quality (Transmit) - A non-dimensional number, 1-100,
representing relative link quality. A value of
100 represents a link of the highest quality.
If a device cannot calculate the RLQT, this
TLV SHOULD NOT be issued.
9.17 Status
The Status TLV is sent as part of an acknowledgement message, from
either the modem or the router, to indicate the success or failure of
a given request.
The Status TLV 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
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length = 1 | Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
Length - 1
Termination Code - 0 = Success, Non-zero = Failure. Specific values
of a non-zero termination code depend on the
operation requested (e.g. Destination Up,
Destination Down, etc).
9.18 Heartbeat Interval
The Heartbeat Interval TLV is a MANDATORY TLV. It MUST be sent during
Peer Initialization to indicate the desired Heartbeat timeout window.
The router MUST either accept the timeout interval supplied by the
modem, or reject the Peer Initialization, and close the socket.
Implementations MUST implement heuristics such that DLEP signals
sent/received reset the timer interval.
The Interval is used to specify a period (in seconds) for Heartbeat
Messages (See Section 23). By specifying an Interval value of 0,
implementations MAY indicates the desire to disable Heartbeat
messages entirely (e.g., the Interval is set to an infinite value),
however, it is strongly recommended that implementations use non 0
timer values.
A DLEP session will be considered inactive, and MUST be torn down, by
an implementation detecting that two (2) Heartbeat intervals have
transpired without receipt of any DLEP messages.
The Heartbeat Interval TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length = 2 | Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
Length - 2
Interval - 0 = Do NOT use heartbeats on this peer-to-peer
session. Non-zero = Interval, in seconds, for
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heartbeat messages.
9.19 Link Characteristics ACK Timer
The Link Characteristics ACK Timer TLV is an OPTIONAL TLV. If
supported, it MAY be sent during Peer Initialization to indicate the
desired number of seconds to wait for a response to a Link
Characteristics Request. If a router receives this TLV from a modem
during Peer Discovery, the router MUST either accept the timeout
value, or reject the Peer Discovery. If this TLV is omitted,
implementations supporting the Link Characteristics Request SHOULD
choose a default value.
The Link Characteristics ACK Timer TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length = 1 | Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
Length - 1
Interval - 0 = Do NOT use timeouts for Link Characteristics
requests on this router/modem session. Non-zero =
Interval, in seconds, to wait before considering a
Link Characteristics Request has been lost.
9.20 Credit Window Status
The Credit Window Status TLV is an OPTIONAL TLV. If credits are
supported by the DLEP participants (both the router and the modem),
the Credit Window Status TLV MUST be sent by the participant
receiving a Credit Grant Request for a given destination.
The Credit Window Status TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length = 16 | Modem Receive Window Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Modem Receive Window Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Modem Receive Window Value | Router Receive Window Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Router Receive Window Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router Receive Window Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
Length - 16
Modem Receive Window Value - A 64-bit unsigned number, indicating
the current (or initial) number of
credits available on the Modem Receive
Window.
Router Receive Window Value - A 64-bit unsigned number, indicating
the current (or initial) number of
credits available on the Router Receive
Window.
9.21 Credit Grant Request
The Credit Grant Request TLV is an OPTIONAL TLV. If credits are
supported, the Credit Grant Request TLV is sent from a DLEP
participant to grant an increment to credits on a window. The Credit
Grant TLV is sent as a data item in either the Destination Up or
Destination Update messages. The value in a Credit Grant TLV
represents an increment to be added to any existing credits available
on the window. Upon successful receipt and processing of a Credit
Grant TLV, the receiver MUST respond with a message containing a
Credit Window Status TLV to report the updated aggregate values for
synchronization purposes.
In the Destination Up message, when credits are desired, the
originating peer MUST set the initial credit value of the window it
controls (e.g. the Modem Receive Window, or Router Receive Window) to
an initial, non-zero value. If the receiver of a Destination Up
message with a Credit Grant Request TLV supports credits, the
receiver MUST either reject the use of credits, via a Destination Up
ACK response with the correct Status TLV, or set the initial value
from the data contained in the Credit Window Status TLV. If the
initialization completes successfully, the receiver MUST respond to
the Destination Up message with a Destination Up ACK message that
contains a Credit Window Status TLV, initializing its receive window.
The Credit Grant TLV contains the following fields:
0 1 2 3
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length = 8 | Credit Increment |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Credit Increment |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Credit Increment |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
Length - 8
Reserved - A 64-bit unsigned number representing the
additional credits to be assigned to the credit
window. Since credits can only be granted by the
receiver on a window, the applicable credit window
(either the MRW or the RRW) is derived from the
sender of the grant. The Credit Increment MUST NOT
cause the window to overflow; if this condition
occurs, implementations MUST set the credit window
to the maximum value contained in a 64-bit
quantity.
9.22 Credit Request
The Credit Request TLV is an OPTIONAL TLV. If credits are supported,
the Credit Request TLV MAY be sent from either DLEP participant, via
a Destination Update signal, to indicate the desire for the partner
to grant additional credits in order for data transfer to proceed on
the session. If the corresponding Destination Up message for this
session did NOT contain a Credit Window Status TLV, indicating that
credits are to be used on the session, then the Credit Request TLV
MUST be rejected by the receiver via a Destination Update ACK
message.
The Credit Request TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TLV Type =TBD |Length = 0 | Reserved, MUST|
| | | be set to 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Type - TBD
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Length - 0
Reserved - This field is currently unused and MUST be set to 0.
10. DLEP Protocol Messages
DLEP messages are encoded as a string of Type-Length-Value (TLV)
constructs. The first TLV in a DLEP message MUST be a valid DLEP
signal, as defined in section 11.1 of this document. The second TLV
MUST be the Identification data item, defined in section 10.1
Following those two TLVs are 0 or more TLVs, representing the data
items that are appropriate for the signal. The layout of a DLEP
message is thus:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DLEP Signal |DLEP Message |Identification |Identification |
| Type value |length (9 + |TLV Type |TLV length |
| (value TBD) |optional TLVs) |(TBD) |(8) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Modem ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Start of optional DLEP |
| TLVs... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
All DLEP messages (signals) begin with this structure. Therefore, in
the following descriptions of specific messages, this header
structure is assumed, and will not be replicated.
10.1 Signal TLV Values
As mentioned above, all DLEP messages begin with the Type value of
the appropriate DLEP signal. Valid DLEP signals are:
TLV TLV
Value Description
=========================================
TBD Peer Discovery
TBD Peer Offer
TBD Peer Initialization
TBD Peer Update
TBD Peer Update ACK
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TBD Peer Termination
TBD Peer Termination ACK
TBD Destination Up
TBD Destination Up ACK
TBD Destination Down
TBD Destination Down ACK
TBD Destination Update
TBD Heartbeat
TBD Link Characteristics Request
TBD Link Characteristics ACK
10.2 Peer Discovery Message
The Peer Discovery Message is sent by a modem to discover DLEP
routers in the network. The Peer Offer message is required to
complete the discovery process. Implementations MAY implement their
own retry heuristics in cases where it is determined the Peer
Discovery Message has timed out.
Given the packet format described in section 11, the initial TLV Type
value is set to DLEP_PEER_DISCOVERY (value TBD).
There are NO Data Item TLVs associated with the Peer Discovery
message.
10.3 Peer Offer Message
The Peer Offer Message is sent by a DLEP router in response to a Peer
Discovery Message. Upon receipt, and processing, of a Peer Offer
message, the modem responds by issuing a TCP connect to the
address/port combination specified in the received Peer Offer.
The Peer Offer message MUST be sent to the unicast address of the
originator of Peer Discovery.
To construct a Peer Offer message, the initial TLV type value is set
to DLEP_PEER_OFFER (value TBD). The signal TLV is then followed by
all MANDATORY Data Item TLVs, then by any OPTIONAL Data Item TLVs the
implementation supports:
Mandatory Data Item TLVs:
- DLEP Version
- Heartbeat Interval
- At least one (1) IPv4 or IPv6 Address TLV
- DLEP Port
Optional Data Item TLVs:
- Peer Type
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- Status
10.4 Peer Initialization Message
The Peer Initialization message is sent by a modem to start the DLEP
TCP session. It is sent by the modem after a TCP connect to the
address/port combination in a received Peer Offer, or to an
address/port obtained from a-priori configuration.
All supported metric data items MUST be included in the Peer
Initialization message, with default values to be used on a "modem-
wide" basis. This can be viewed as the modem "declaring" all
supported metrics at DLEP session initialization. Receipt of any DLEP
message containing a metric data item NOT included in Peer
Initialization MUST be treated as an error, resulting in termination
of the DLEP session between router and modem.
To construct a Peer Initialization message, the initial TLV type
value is set to DLEP_PEER_INIT (value TBD). The signal TLV is then
followed by the required data items:
Mandatory Data Item TLVs:
- DLEP Version
- Heartbeat Interval
- Maximum Data Rate Receive
- Maximum Data Rate Transmit
- Current Data Rate Receive
- Current Data Rate Transmit
- Latency
- Relative Link Quality Receive
- Relative Link Quality Transmit
Optional Data Item TLVs:
- Peer Type
Note that metric data items MUST be supplied with the Peer
Initialization, in order to populate default metric values. If, at
any time, metrics are reported that were NOT in Peer Initialization,
the receiving DLEP peer MUST treat this as a fatal error requiring
termination of the DLEP session.
10.5 Peer Initialization ACK Message
The Peer Initialization ACK message is a MANDATORY message, sent in
response to a received Peer Initialization message. The Peer
Initialization ACK message completes the TCP-level DLEP session
establishment; the sender of the message should transition to an "in-
session" state when the message is sent, and the receiver should
transition to the "in-session" state upon receipt (and successful
parsing) of Peer Initialization ACK.
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To construct a Peer Initialization ACK message, the initial TLV type
value is set to DLEP_PEER_INIT_ACK (value TBD). The signal TLV is
then followed by the required data items:
Mandatory Data Item TLVs:
- Status
Optional Data Item TLVs:
- Peer Type
10.6 Peer Update Message
The Peer Update message is an OPTIONAL message, sent by a DLEP peer
to indicate local Layer 3 address changes, or for metric changes on a
modem-wide basis. For example, addition of an IPv4 address to the
router MAY prompt a Peer Update message to its attached DLEP modems.
Also, a modem that changes its Maximum Data Rate for all destinations
MAY reflect that change via a Peer Update Message to its attached
router(s).
Concerning Layer 3 addresses, if the modem is capable of
understanding and forwarding this information (via proprietary
mechanisms), the address update would prompt any remote DLEP modems
(DLEP-enabled modems in a remote node) to issue a "Destination
Update" message to their local routers with the new (or deleted)
addresses. Modems that do not track Layer 3 addresses SHOULD silently
parse and ignore the Peer Update Message. Modems that track Layer 3
addresses MUST acknowledge the Peer Update with a Peer Update ACK
message. Routers receiving a Peer Update with metric changes MUST
apply the new metric to all destinations (remote nodes) accessible
via the modem. Supporting implementations are free to employ
heuristics to retransmit Peer Update messages. The sending of Peer
Update Messages for Layer 3 address changes SHOULD cease when a
either participant (router or modem) determines that the other
implementation does NOT support Layer 3 address tracking.
If metrics are supplied with the Peer Update message (e.g. Maximum
Data Rate), these metrics are considered to be modem-wide, and
therefore MUST be applied to all destinations in the information base
associated with the router/modem session.
To construct a Peer Update message, the initial TLV type value is set
to DLEP_PEER_UPDATE (value TBD). The Signal TLV is followed by any
OPTIONAL Data Item TLVs.
Optional Data Item TLVs:
- IPv4 Address
- IPv6 Address
- Maximum Data Rate (Receive)
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- Maximum Data Rate (Transmit)
- Current Data Rate (Receive)
- Current Data Rate (Transmit)
- Latency
- Expected Forwarding Time
- Resources (Receive)
- Resources (Transmit)
- Relative Link Quality (Receive)
- Relative Link Quality (Transmit)
10.7 Peer Update ACK Message
The Peer Update ACK message is an OPTIONAL message, and is sent by
implementations supporting Layer 3 address tracking and/or modem-wide
metrics to indicate whether a Peer Update Message was successfully
processed. If the Peer Update ACK is issued, it MUST contain a Status
data item, indicating the success or failure of processing the
received Peer Update.
To construct a Peer Update ACK message, the initial TLV type value is
set to DLEP_PEER_UPDATE_ACK (value TBD). The Status data item TLV is
placed in the packet next, completing the Peer Update ACK.
Mandatory Data Item TLVs:
- Status
Note that there are NO OPTIONAL data item TLVs specified for this
message.
10.8 Peer Termination Message
The Peer Termination Message is sent by a DLEP participant when the
router/modem session needs to be terminated. Implementations
receiving a Peer Termination message MUST send a Peer Termination ACK
message to confirm the termination process. The sender of a Peer
Termination message is free to define its heuristics in event of a
timeout. The receiver of a Peer Termination Message 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
messages are sent.
To construct a Peer Termination message, the initial TLV type value
is set to DLEP_PEER_TERMINATION (value TBD). The Signal TLV is
followed by any OPTIONAL Data Item TLVs the implementation supports:
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Optional Data Item TLVs:
- Status
10.9 Peer Termination ACK Message
The Peer Termination Message ACK is sent by a DLEP peer in response
to a received Peer Termination order. Receipt of a Peer Termination
ACK message completes the teardown of the router/modem session.
To construct a Peer Termination ACK message, the initial TLV type
value is set to DLEP_PEER_TERMINATION_ACK (value TBD). The
Identification data item TLV is placed in the packet next, followed
by any OPTIONAL TLVs the implementation supports:
Optional Data Item TLVs:
- Status
10.10 Destination Up Message
A DLEP participant sends the Destination Up message to report that a
new destination has been detected. A Destination Up ACK Message is
required to confirm a received Destination Up. A Destination Up
message can be sent either by the modem, to indicate that a new
remote node has been detected, or by the router, to indicate the
presence of a new logical destination (e.g., a Multicast group)
exists in the network.
The sender of the Destination Up Message is free to define its retry
heuristics in event of a timeout. When a Destination Up message is
received and successfully parsed, the receiver should add knowledge
of the new destination to its information base, indicating that the
destination is accessible via the modem/router pair.
To construct a Destination Up message, the initial TLV type value is
set to DLEP_Destination_UP (value TBD). The MAC Address data item TLV
is placed in the packet next, followed by any supported OPTIONAL Data
Item TLVs into the packet:
Optional Data Item TLVs:
- IPv4 Address
- IPv6 Address
- Maximum Data Rate (Receive)
- Maximum Data Rate (Transmit)
- Current Data Rate (Receive)
- Current Data Rate (Transmit)
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- Latency
- Expected Forwarding Time
- Resources (Receive)
- Resources (Transmit)
- Relative Link Factor (Receive)
- Relative Link Factor (Transmit)
- Credit Window Status
10.11 Destination Up ACK Message
A DLEP participant sends the Destination Up ACK Message to indicate
whether a Destination Up Message was successfully processed.
To construct a Destination Up ACK message, the initial TLV type value
is set to DLEP_Destination_UP_ACK (value TBD). The MAC Address data
item TLV is placed in the packet next, containing the MAC address of
the DLEP destination. The implementation would then place any
supported OPTIONAL Data Item TLVs into the packet:
Optional Data Item TLVs:
- Credit Window Status
10.12 Destination Down Message
A DLEP peer sends the Destination Down message to report when a
destination (a remote node or a multicast group) is no longer
reachable. The Destination Down message MUST contain the MAC Address
data item TLV. Other TLVs as listed are OPTIONAL, and MAY be present
if an implementation supports them. A Destination Down ACK Message
MUST be sent by the recipient of a Destination Down message to
confirm that the relevant data has been removed from the information
base. The sender of the Destination Down message is free to define
its retry heuristics in event of a timeout.
To construct a Destination Down message, the initial TLV type value
is set to DLEP_Destination_DOWN (value TBD). The signal TLV is
followed by the mandatory MAC Address data item TLV.
Note that there are NO OPTIONAL data item TLVs for this message.
10.13 Destination Down ACK Message
A DLEP participant sends the Destination Down ACK Message to indicate
whether a received Destination Down Message 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. As with the Destination Down message, there
are NO OPTIONAL Data Item TLVs defined for the Destination Down ACK
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message.
To construct a Destination Down message, the initial TLV type value
is set to DLEP_Destination_DOWN_ACK (value TBD). The mandatory data
item TLVs follow:
- MAC Address Data item
- Status data item
10.14 Destination Update Message
A DLEP participant sends the Destination Update message when it
detects some change in the information base for a given destination
(remote node or multicast group). Some examples of changes that would
prompt a Destination Update message are:
- Change in link metrics (e.g., Data Rates)
- Layer 3 addressing change (for implementations that support it)
To construct a Destination Update message, the initial TLV type value
is set to DLEP_Destination_UPDATE (value TBD). Following the signal
TLV are the mandatory Data Item TLVs:
MAC Address data item TLV
After placing the mandatory data item TLV into the packet, the
implementation would place any supported OPTIONAL data item TLVs.
Possible OPTIONAL data item TLVs are:
- IPv4 Address
- IPv6 Address
- Maximum Data Rate (Receive)
- Maximum Data Rate (Transmit)
- Current Data Rate (Receive)
- Current Data Rate (Transmit)
- Latency
- Resources (Receive)
- Resources (Transmit)
- Relative Link Quality (Receive)
- Relative Link Quality (Transmit)
- Credit Window Status
- Credit Grant
- Credit Request
10.15 Heartbeat Message
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A Heartbeat Message is sent by a DLEP participant every N seconds,
where N is defined in the "Heartbeat Interval" field of the discovery
message. Note that implementations setting the Heartbeat Interval to
0 effectively set the interval to an infinite value, therefore, in
those cases, this message would NOT be sent.
The message is used by participants to detect when a DLEP session
partner (either the modem or the router) is no longer communicating.
Participants SHOULD allow two (2) heartbeat intervals to expire with
no traffic on the router/modem session before initiating DLEP session
termination procedures.
To construct a Heartbeat message, the initial TLV type value is set
to DLEP_PEER_HEARTBEAT (value TBD). The signal TLV is followed by the
mandatory Heartbeat Interval/Threshold data item.
Note that there are NO OPTIONAL data item TLVs for this message.
10.16 Link Characteristics Request Message
The Link Characteristics Request Message is an OPTIONAL message, and
is sent by the router to request that the modem initiate changes for
specific characteristics of the link. The request can reference
either a real (e.g., a remote node), or a logical (e.g., a multicast
group) destination within the network.
The Link Characteristics Request message contains either a Current
Data Rate (CDRR or CDRT) TLV to request a different datarate than
what is currently allocated, a Latency TLV to request that traffic
delay on the link not exceed the specified value, or both. A Link
Characteristics ACK Message is required to complete the request.
Implementations are free to define their retry heuristics in event of
a timeout. Issuing a Link Characteristics Request with ONLY the MAC
Address TLV is a mechanism a peer MAY use to request metrics (via the
Link Characteristics ACK) from its partner.
To construct a Link Characteristics Request message, the initial TLV
type value is set to DLEP_Destination_LINK_CHAR_REQ (value TBD).
Following the signal TLV is the mandatory Data Item TLV:
MAC Address data item TLV
After placing the mandatory data item TLV into the packet, the
implementation would place any supported OPTIONAL data item TLVs.
Possible OPTIONAL data item TLVs are:
Current Data Rate - If present, this value represents the NEW (or
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unchanged, if the request is denied) Current
Data Rate in bits per second (bps).
Latency - If present, this value represents the maximum
desired latency (e.g., it is a not-to-exceed
value) in milliseconds on the link.
10.17 Link Characteristics ACK Message
The LInk Characteristics ACK message is an OPTIONAL message, and is
sent by modems supporting it to the router letting the router know
the success or failure of a requested change in link characteristics.
The Link Characteristics ACK message SHOULD contain a complete set
of metric data item TLVs. It MUST contain the same TLV types as the
request. The values in the metric data item TLVs in the Link
Characteristics ACK message MUST reflect the link characteristics
after the request has been processed.
To construct a Link Characteristics Request ACK message, the initial
TLV type value is set to DLEP_Destination_LINK_CHAR_ACK (value TBD).
Following the signal TLV is the mandatory Data Item TLV:
MAC Address data item TLV
After placing the mandatory data item TLV into the packet, the
implementation would place any supported OPTIONAL data item TLVs.
Possible OPTIONAL data item TLVs are:
Current Data Rate - If present, this value represents the requested
data rate in bits per second (bps).
Latency - If present, this value represents the NEW
maximum latency (or unchanged, if the request
is denied), expressed in milliseconds, on the
link.
11. 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 DTLS or some other mechanism), and is therefore outside the scope
of this document.
12. IANA Considerations
This section specifies requests to IANA.
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12.1 Registrations
This specification defines:
o A new repository for DLEP signals, with fifteen values currently
assigned.
o Reservation of numbering space for Experimental DLEP signals.
o A new repository for DLEP Data Items, with twenty-one values
currently assigned.
o Reservation of numbering space in the Data Items repository for
experimental data items.
o A request for allocation of a well-known port for DLEP
communication.
o A request for allocation of a multicast address for DLEP
discovery.
12.2 Expert Review: Evaluation Guidelines
No additional guidelines for expert review are anticipated.
12.3 Message (Signal) TLV Type Registration
A new repository must be created with the values of the DLEP
messages. 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
o Link Characteristics Request
o Link Characteristics ACK
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It is also requested that the repository contain space for
experimental signal types.
12.4 DLEP Data Item Registrations
A new repository for DLEP Data Items must be created. Valid Data
Items are:
o DLEP Version
o Peer Type
o MAC Address
o IPv4 Address
o IPv6 Address
o Maximum Data Rate (Receive)
o Maximum Data Rate (Transmit)
o Current Data Rate (Receive)
o Current Data Rate (Transmit)
o Latency
o Expected Forwarding Time
o Resources (Receive)
o Resources (Transmit)
o Relative Link Quality (Receive)
o Relative Link Quality (Transmit)
o Status
o Heartbeat Interval/Threshold
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.
12.5 DLEP Well-known Port
It is requested that IANA allocate a well-known port number for DLEP
communication.
12.6 DLEP Multicast Address
It is requested that IANA allocate a multicast address for DLEP
discovery messages.
13. Appendix A.
13.1 Peer Level Message Flows
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13.1.1 Modem Device Restarts Discovery
Router Modem Message Description
====================================================================
<-------Peer Discovery--------- Modem initiates discovery
---------Peer Offer-----------> Router detects a problem, sends
w/ Non-zero Status TLV Peer Offer w/Status TLV indicating
the error.
Modem accepts failure, restarts
discovery process.
<-------Peer Discovery--------- Modem initiates discovery
---------Peer Offer-----------> Router accepts, sends Peer Offer
w/ Zero Status TLV w/ Status TLV indicating success.
Discovery completed.
13.1.2 Modem Device Detects Peer Offer Timeout
Router Modem Message Description
====================================================================
<-------Peer Discovery--------- Modem initiates discovery, starts
a guard timer.
Modem guard timer expires. Modem
restarts discovery process.
<-------Peer Discovery--------- Modem initiates discovery, starts
a guard timer.
---------Peer Offer-----------> Router accepts, sends Peer Offer
w/ Zero Status TLV w/ Status TLV indicating success.
Discovery completed.
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13.1.3 Router Peer Offer Lost
Router Modem Message Description
====================================================================
<-------Peer Discovery--------- Modem initiates discovery, starts
a guard timer.
---------Peer Offer-------|| Router offers availability
Modem times out on Peer Offer,
restarts discovery process.
<-------Peer Discovery--------- Modem initiates discovery
---------Peer Offer-----------> Router detects subsequent
discovery, internally terminates
the previous, accepts the new
association, sends Peer Offer
w/Status TLV indicating success.
Discovery completed.
13.1.4 Discovery Success
Router Modem Message Description
====================================================================
<-------Peer Discovery--------- Modem initiates discovery
---------Peer Offer-----------> Router offers availability
<-----Peer Initialization------ Modem Connects on TCP Port
<------Peer Heartbeat----------
-------Peer Heartbeat--------->
<==============================> Message flow about destinations
(i.e. Destination Up, Destination
Down, Destination update)
<-------Peer Heartbeat---------
-------Peer Heartbeat--------->
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--------Peer Term Req---------> Terminate Request
<--------Peer Term Res--------- Terminate Response
29.1.5 Router Detects a Heartbeat timeout
Router Modem Message Description
====================================================================
<-------Peer Heartbeat---------
-------Peer Heartbeat--------->
||---Peer Heartbeat---------
~ ~ ~ ~ ~ ~ ~
-------Peer Heartbeat--------->
||---Peer Heartbeat---------
Router Heartbeat Timer expires,
detects missing heartbeats. Router
takes down all destination sessions
and terminates the Peer
association.
------Peer Terminate ---------> Peer Terminate Request
Modem takes down all destination
sessions, then acknowledges the
Peer Terminate
<----Peer Terminate ACK--------- Peer Terminate ACK
29.1.6 Modem Detects a Heartbeat timeout
Router Modem Message Description
====================================================================
<-------Peer Heartbeat---------
-------Peer Heartbeat------||
<-------Peer Heartbeat---------
~ ~ ~ ~ ~ ~ ~
-------Peer Heartbeat------||
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<-------Peer Heartbeat---------
Modem Heartbeat Timer expires,
detects missing heartbeats. Modem
takes down all destination sessions
<-------Peer Terminate-------- Peer Terminate Request
Router takes down all destination
sessions, then acknowledges the
Peer Terminate
------Peer Terminate ACK-----> Peer Terminate ACK
29.1.7 Peer Terminate (from Modem) Lost
Router Modem Message Description
====================================================================
||------Peer Terminate-------- Modem Peer Terminate Request
Router Heartbeat times out,
terminates association.
--------Peer Terminate-------> Router Peer Terminate
<-----Peer Terminate ACK------ Modem sends Peer Terminate ACK
29.1.8 Peer Terminate (from Router) Lost
Router Modem Message Description
====================================================================
-------Peer Terminate--------> Router Peer Terminate Request
Modem HB times out,
terminates association.
<------Peer Terminate-------- Modem Peer Terminate
------Peer Terminate ACK-----> Peer Terminate ACK
29.2 Destination Specific Message Flows
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29.2.1 Modem Destination Up Lost
Router Modem Message Description
====================================================================
||-----Destination Up ------------ Modem sends Destination Up
Modem timesout on ACK
<------Destination Up ------------ Modem sends Destination Up
------Destination Up ACK---------> Router accepts the destination
session
<------Destination Update--------- Modem Destination Metrics
. . . . . . . .
<------Destination Update--------- Modem Destination Metrics
29.2.2 Router Detects Duplicate Destination Ups
Router Modem Message Description
====================================================================
<------Destination Up ------------ Modem sends Destination Up
------Destination Up ACK-------|| Router accepts the destination
session
Modem timesout on ACK
<------Destination Up ------------ Modem resends Destination Up
Router detects duplicate
Destination, takes down the
previous, accepts the new
Destination.
------Destination Up ACK---------> Router accepts the destination
session
<------Destination Update--------- Modem Destination Metrics
. . . . . . . .
<------Destination Update--------- Modem Destination Metrics
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29.2.3 Destination Up, No Layer 3 Addresses
Router Modem Message Description
====================================================================
<------Destination Up ------------ Modem sends Destination Up
------Destination Up ACK---------> Router accepts the destination
session
Router ARPs for IPv4 if defined.
Router drives ND for IPv6 if
defined.
<------Destination Update--------- Modem Destination Metrics
. . . . . . . .
<------Destination Update--------- Modem Destination Metrics
29.2.4 Destination Up with IPv4, No IPv6
Router Modem Message Description
====================================================================
<------Destination Up ------------ Modem sends Destination Up with
the IPv4 TLV
------Destination Up ACK---------> Router accepts the destination
session
Router drives ND for IPv6 if
defined.
<------Destination Update--------- Modem Destination Metrics
. . . . . . . .
<------Destination Update--------- Modem Destination Metrics
29.2.5 Destination Up with IPv4 and IPv6
Router Modem Message Description
====================================================================
<------Destination Up ------------ Modem sends Destination Up with
the IPv4 and IPv6 TLVs
------Destination Up ACK---------> Router accepts the destination
session
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<------Destination Update--------- Modem Destination Metrics
. . . . . . . .
29.2.6 Destination Session Success
Router Modem Message Description
====================================================================
---------Peer Offer-----------> Router offers availability
-------Peer Heartbeat--------->
<------Destination Up ----------- Modem
------Destination Up ACK--------> Router
<------Destination Update--------- Modem
. . . . . . . .
<------Destination Update--------- Modem
Modem initiates the terminate
<------Destination Down ---------- Modem
------Destination Down ACK-------> Router
or
Router initiates the terminate
------Destination Down ----------> Router
<------Destination Down ACK------- Modem
Acknowledgements
The authors 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,
Henning Rogge, and Rick Taylor.
The authors would also like to acknowledge the influence and
contributions of Chris Olsen, Martin Duke, Subir Das, Jaewon Kang,
Vikram Kaul, and Nelson Powell.
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Normative References
[RFC5578] Berry, B., Ed., "PPPoE with Credit Flow and Metrics",
RFC 5578, February 2010.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Informative References
[TLS] Dierks, T. and Rescorla, E. "The Transport Layer Security
(TLS) Protocol", RFC 5246, August 2008.
Author's Addresses
Stan Ratliff
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
EMail: sratliff@cisco.com
Bo Berry
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
EMail: boberry@cisco.com
Greg Harrison
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
EMail: greharri@cisco.com
Shawn Jury
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Email: sjury@cisco.com
Darryl Satterwhite
Broadcom
USA
Email: dsatterw@broadcom.com
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