Dynamic Link Exchange Protocol (DLEP) Latency Range ExtensionMIT Lincoln LaboratoryMassachusetts Institute of Technology244 Wood StreetLexingtonMA02421-6426USAbcheng@ll.mit.eduLabN Consulting, L.L.C.lberger@labn.netMANET
This document defines an extension to the Dynamic Link Exchange Protocol (DLEP) to provide the
range of latency that can be experienced on a link.
Status of This Memo
This is an Internet Standards Track document.
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(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by
the Internet Engineering Steering Group (IESG). Further
information on Internet Standards is available in Section 2 of
RFC 7841.
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Table of Contents
. Introduction
. Key Words
. Extension Usage and Identification
. Latency Range Data Item
. Security Considerations
. IANA Considerations
. Extension Type Value
. Data Item Value
. References
. Normative References
. Informative References
Acknowledgments
Authors' Addresses
Introduction
The Dynamic Link Exchange Protocol (DLEP) is defined in .
It provides the exchange of link-related control information between DLEP peers. DLEP peers are
comprised of a modem and a router. DLEP defines a base set of
mechanisms as well as support for possible extensions. This
document defines one such extension.
The base DLEP specification includes the Latency Data Item, which
provides a single, implementation-dependent latency value on a
link. This document adds the ability to relay
the minimum and maximum latency range seen on a link. The extension
defined in this document is referred to as "Latency Range".
This document defines a new DLEP Extension Type Value that is used to
indicate the use of the extension; see . A new DLEP Data Item is defined in .
Key Words
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
when, and only when, they appear in all capitals, as shown here.
Extension Usage and Identification
The use of the Latency Range Extension SHOULD be configurable. To
indicate that the Latency Range Extension is to be used, an
implementation MUST include the Latency Range Extension Type Value in
the Extensions Supported Data Item. The Extensions Supported Data
Item is sent and processed according to .
Note: The usage of the extension defined in this document does not
impact processing associated with the Latency Data Item defined in
.
The Latency Range Extension Type Value is 4; see .
Latency Range Data Item
The Latency Range Data Item serves much the same purpose as the
Latency Data Item defined in with
the addition of being able to communicate the latency range that can
be experienced by traffic on a link. The Latency Range Data Item
MUST be included in the Session Initialization Response Message, with
default values to be used on a session-wide basis.
The Latency Range Data Item also MAY be
carried in any message where the Latency Data Item is
allowed and is carried as an additional data item. When present, the
Latency Range Data Item MUST be processed according to the same rules
as the Latency Data Item defined in .
The format of the Latency Range Data Item is:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Latency :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: Maximum Latency |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum Latency :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: Minimum Latency |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type:
28
Length:
16
Maximum Latency:
A 64-bit unsigned integer, representing the longest transmission
delay, in microseconds, that a packet encounters as it is
transmitted over the link.
Minimum Latency:
A 64-bit unsigned integer, representing the shortest transmission
delay, in microseconds, that a packet can encounter as it is
transmitted over the link.
Security Considerations
The extension introduces a new Data Item
for DLEP. The
extension does not inherently introduce any additional vulnerabilities
above those documented in .
The approach taken to security in that document applies equally
when running the extension defined in this document.
IANA Considerations
As described below, IANA has assigned two values per this document. Both assignments are to
registries defined by .
Extension Type Value
IANA has assigned the following value in the
"Extension Type Values" registry within the "Dynamic Link Exchange Protocol
(DLEP) Parameters" registry. The new value is in the range with the
"Specification Required" policy:
New Extension Type Value
Code
Description
4
Latency Range
Data Item Value
IANA has assigned the following value in the "Data Item Type Values" registry
within the "Dynamic Link Exchange Protocol (DLEP) Parameters" registry. The new
value is in the range with the "Specification Required" policy:
New Data Item Value
Type Code
Description
28
Latency Range
ReferencesNormative ReferencesKey words for use in RFCs to Indicate Requirement LevelsIn many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.Ambiguity of Uppercase vs Lowercase in RFC 2119 Key WordsRFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.Dynamic Link Exchange Protocol (DLEP)When routing devices rely on modems to effect communications over wireless links, they need timely and accurate knowledge of the characteristics of the link (speed, state, etc.) in order to make routing decisions. In mobile or other environments where these characteristics change frequently, manual configurations or the inference of state through routing or transport protocols does not allow the router to make the best decisions. This document introduces a new protocol called the Dynamic Link Exchange Protocol (DLEP), which provides a bidirectional, event-driven communication channel between the router and the modem to facilitate communication of changing link characteristics.Informative ReferencesGuidelines for Writing an IANA Considerations Section in RFCsMany protocols make use of points of extensibility that use constants to identify various protocol parameters. To ensure that the values in these fields do not have conflicting uses and to promote interoperability, their allocations are often coordinated by a central record keeper. For IETF protocols, that role is filled by the Internet Assigned Numbers Authority (IANA).To make assignments in a given registry prudently, guidance describing the conditions under which new values should be assigned, as well as when and how modifications to existing values can be made, is needed. This document defines a framework for the documentation of these guidelines by specification authors, in order to assure that the provided guidance for the IANA Considerations is clear and addresses the various issues that are likely in the operation of a registry.This is the third edition of this document; it obsoletes RFC 5226.Acknowledgments
Helpful comments were received from members of the MANET working
group, including , , and .
Authors' AddressesMIT Lincoln LaboratoryMassachusetts Institute of Technology244 Wood StreetLexingtonMA02421-6426USAbcheng@ll.mit.eduLabN Consulting, L.L.C.lberger@labn.net