Pseudowire Congestion Considerations
RFC 7893
Document | Type | RFC - Informational (June 2016; No errata) | |
---|---|---|---|
Authors | Yaakov Stein , David Black , Bob Briscoe | ||
Last updated | 2016-06-29 | ||
Replaces | draft-ietf-pwe3-congcons | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Reviews | |||
Stream | WG state | Submitted to IESG for Publication | |
Document shepherd | Andy Malis | ||
Shepherd write-up | Show (last changed 2015-10-06) | ||
IESG | IESG state | RFC 7893 (Informational) | |
Action Holders |
(None)
|
||
Consensus Boilerplate | Yes | ||
Telechat date | |||
Responsible AD | Deborah Brungard | ||
Send notices to | (None) | ||
IANA | IANA review state | Version Changed - Review Needed | |
IANA action state | No IANA Actions |
Internet Engineering Task Force (IETF) Y(J) Stein Request for Comments: 7893 RAD Data Communications Category: Informational D. Black ISSN: 2070-1721 EMC Corporation B. Briscoe BT June 2016 Pseudowire Congestion Considerations Abstract Pseudowires (PWs) have become a common mechanism for tunneling traffic and may be found in unmanaged scenarios competing for network resources both with other PWs and with non-PW traffic, such as TCP/IP flows. Thus, it is worthwhile specifying under what conditions such competition is acceptable, i.e., the PW traffic does not significantly harm other traffic or contribute more than it should to congestion. We conclude that PWs transporting responsive traffic behave as desired without the need for additional mechanisms. For inelastic PWs (such as Time Division Multiplexing (TDM) PWs), we derive a bound under which such PWs consume no more network capacity than a TCP flow. For TDM PWs, we find that the level of congestion at which the PW can no longer deliver acceptable TDM service is never significantly greater, and is typically much lower, than this bound. Therefore, as long as the PW is shut down when it can no longer deliver acceptable TDM service, it will never do significantly more harm than even a single TCP flow. If the TDM service does not automatically shut down, a mechanism to block persistently unacceptable TDM pseudowires is required. Status of This Memo This document is not an Internet Standards Track specification; it is published for informational purposes. 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). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see 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 http://www.rfc-editor.org/info/rfc7893. Stein, et al. Informational [Page 1] RFC 7893 Pseudowire Congestion June 2016 Copyright Notice Copyright (c) 2016 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 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 . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. PWs Comprising Elastic Flows . . . . . . . . . . . . . . . . 6 4. PWs Comprising Inelastic Flows . . . . . . . . . . . . . . . 7 5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 19 6. Security Considerations . . . . . . . . . . . . . . . . . . . 19 7. Informative References . . . . . . . . . . . . . . . . . . . 19 Appendix A. Loss Probabilities for TDM PWs . . . . . . . . . . . 22 Appendix B. Effect of Packet Loss on Voice Quality for Structure-Aware TDM PWs . . . . . . . . . . . . . . 23 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 Stein, et al. Informational [Page 2] RFC 7893 Pseudowire Congestion June 2016 1. Introduction A pseudowire (PW) (see [RFC3985]) is a construct for tunneling a native service, such as Ethernet or TDM, over a Packet Switched Network (PSN), such as IPv4, IPv6, or MPLS. The PW packet encapsulates a unit of native service information by prepending the headers required for transport in the particular PSN (which must include a demultiplexer field to distinguish the different PWs) and preferably the 4-byte Pseudowire Emulation Edge-to-Edge (PWE3) control word. PWs have no bandwidth reservation or control mechanisms, meaning that when multiple PWs are transported in parallel, and/or in parallel with other flows, there is no defined means for allocating resourcesShow full document text