Dynamic Link Exchange Protocol (DLEP) Latency Range Extension MIT Lincoln Laboratory
Massachusetts Institute of Technology 244 Wood Street Lexington MA 02421-6426 USA bcheng@ll.mit.edu
LabN Consulting, L.L.C.
lberger@labn.net
MANET 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 .
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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
References Normative References Key words for use in RFCs to Indicate Requirement Levels In 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 Words RFC 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 References Guidelines for Writing an IANA Considerations Section in RFCs Many 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' Addresses MIT Lincoln Laboratory
Massachusetts Institute of Technology 244 Wood Street Lexington MA 02421-6426 USA bcheng@ll.mit.edu
LabN Consulting, L.L.C.
lberger@labn.net