RFC 8757 PROPOSED STANDARD DLEP · LATENCY
Dynamic Link Exchange Protocol (DLEP) Latency Range Extension
A DLEP extension that reports minimum and maximum link latency instead of a single value.
RFC EDITOR
Cheng, B. and L. Berger, Ed., "Dynamic Link Exchange Protocol (DLEP) Latency Range Extension", RFC 8757, DOI 10.17487/RFC8757, March 2020, <https://www.rfc-editor.org/info/rfc8757>.
BIBTEX
@misc{rfc8757,
series = {Request for Comments},
number = 8757,
howpublished = {RFC 8757},
publisher = {RFC Editor},
doi = {10.17487/RFC8757},
url = {https://www.rfc-editor.org/info/rfc8757},
author = {B. Cheng and L. Berger},
title = {{Dynamic Link Exchange Protocol (DLEP) Latency Range Extension}},
pagetotal = 5,
year = 2020,
month = mar,
} RFC text
Contents
Internet Engineering Task Force (IETF) B. Cheng
Request for Comments: 8757 MIT Lincoln Laboratory
Category: Standards Track L. Berger, Ed.
ISSN: 2070-1721 LabN Consulting, L.L.C.
March 2020
Dynamic Link Exchange Protocol (DLEP) Latency Range Extension
Abstract
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.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8757.
Copyright Notice
Copyright (c) 2020 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
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction
1.1. Key Words
2. Extension Usage and Identification
3. Latency Range Data Item
4. Security Considerations
5. IANA Considerations
5.1. Extension Type Value
5.2. Data Item Value
6. References
6.1. Normative References
6.2. Informative References
Acknowledgments
Authors' Addresses
1. Introduction
The Dynamic Link Exchange Protocol (DLEP) is defined in [RFC8175].
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 Section 2. A new DLEP Data
Item is defined in Section 3.
1.1. 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 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. 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 [RFC8175].
Note: The usage of the extension defined in this document does not
impact processing associated with the Latency Data Item defined in
[RFC8175].
The Latency Range Extension Type Value is 4; see Section 5.
3. Latency Range Data Item
The Latency Range Data Item serves much the same purpose as the
Latency Data Item defined in [RFC8175] 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 [RFC8175]
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 [RFC8175].
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.
4. Security Considerations
The extension introduces a new Data Item for DLEP. The extension
does not inherently introduce any additional vulnerabilities above
those documented in [RFC8175]. The approach taken to security in
that document applies equally when running the extension defined in
this document.
5. IANA Considerations
As described below, IANA has assigned two values per this document.
Both assignments are to registries defined by [RFC8175].
5.1. 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" [RFC8126] policy:
+------+---------------+
| Code | Description |
+======+===============+
| 4 | Latency Range |
+------+---------------+
Table 1: New Extension
Type Value
5.2. 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" [RFC8126] policy:
+-----------+---------------+
| Type Code | Description |
+===========+===============+
| 28 | Latency Range |
+-----------+---------------+
Table 2: New Data Item Value
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8175] Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and B.
Berry, "Dynamic Link Exchange Protocol (DLEP)", RFC 8175,
DOI 10.17487/RFC8175, June 2017,
<https://www.rfc-editor.org/info/rfc8175>.
6.2. Informative References
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
Acknowledgments
Helpful comments were received from members of the MANET working
group, including Ronald in 't Velt, Henning Rogge, and Victoria
Pritchard.
Authors' Addresses
Bow-Nan Cheng
MIT Lincoln Laboratory
Massachusetts Institute of Technology
244 Wood Street
Lexington, MA 02421-6426
United States of America
Email: bcheng@ll.mit.edu
Lou Berger (editor)
LabN Consulting, L.L.C.
Email: lberger@labn.net
AI ELI5
On this page
PROBLEMThe base Dynamic Link Exchange Protocol (DLEP) Latency Data Item gives only one implementation-dependent latency value for a link.
MECHANISMA Latency Range extension (Extension Type Value 4) adds a Latency Range Data Item (type 28) carrying a 64-bit maximum and a 64-bit minimum latency in microseconds.
WHY IT MATTERSRouters can learn the range of delay seen on a link. Use of the extension SHOULD be configurable.
§1A Range Instead of One Number
DLEP (RFC 8175) exchanges link control information between a modem and a router. It supports extensions, and this document defines one, called Latency Range.
The base specification has a Latency Data Item with a single latency value. This extension adds the minimum and maximum latency seen on a link.
The old way gave one number for delay. The new way gives the shortest and the longest.
§2Turning the Extension On
Use of the extension SHOULD be configurable. To use it, an implementation MUST include the Latency Range Extension Type Value, which is 4, in the Extensions Supported Data Item, which is handled as in RFC 8175.
Using the extension does not change how the base Latency Data Item is processed.
Both sides announce that they speak this extra feature, and the old way of reporting still works.
§3The Latency Range Data Item
The Latency Range Data Item MUST be included in the Session Initialization Response Message, with default values used session-wide. It MAY also appear in any message where the Latency Data Item is allowed, as an additional data item, and is processed by the same rules.
Its Data Item Type is 28 and its Length is 16. It holds a 64-bit unsigned Maximum Latency, the longest delay a packet encounters on the link, followed by a 64-bit unsigned Minimum Latency, the shortest delay a packet can encounter. Both are in microseconds.
It is a small note with two numbers: the longest wait and the shortest wait for a message to cross the link.
| Field | Name | Size | Value | Description |
|---|---|---|---|---|
TYPE | Data Item Type | 2 bytes | 28 | Identifies the data item. |
LENGTH | Length | 2 bytes | 16 | Length of the data item value. |
MAX | Maximum Latency | 8 bytes | Longest transmission delay a packet encounters, in microseconds. | |
MIN | Minimum Latency | 8 bytes | Shortest transmission delay a packet can encounter, in microseconds. |
§4Security and IANA
The extension adds no vulnerabilities beyond those in RFC 8175, and that document's approach to security applies. IANA assigned Extension Type Value 4 and Data Item Type 28, both named Latency Range.
The extra note adds no new risks, and it got its own official numbers.