PPP Over Ethernet (PPPoE) Extensions for Credit Flow and Link Metrics
RFC 4938
Document | Type |
RFC - Informational
(June 2007; Errata)
Obsoleted by RFC 5578
Was draft-bberry-pppoe-credit (int)
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Authors | Bo Berry , Howard Holgate | ||
Last updated | 2020-01-21 | ||
Stream | Independent Submission | ||
Formats | plain text html pdf htmlized (tools) htmlized with errata bibtex | ||
Stream | ISE state | (None) | |
Consensus Boilerplate | Unknown | ||
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 4938 (Informational) | |
Action Holders |
(None)
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Telechat date | |||
Responsible AD | Mark Townsley | ||
Send notices to | (None) |
Network Working Group B. Berry Request for Comments: 4938 H. Holgate Category: Informational Cisco Systems,Inc. June 2007 PPP Over Ethernet (PPPoE) Extensions for Credit Flow and Link Metrics Status of This Memo This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The IETF Trust (2007). IESG Note The PPP Extensions Working Group (PPPEXT) has reservations about the desirability of the feature described in this document. In particular, it solves a general problem at an inappropriate layer and it may have unpredictable interactions with higher and lower level protocols. The techniques described in this document are intended for use with a particular deployment technique that uses a PPP termination separated from a radio termination by an Ethernet, and that has radio-side flow control for a slower PPP-only link to remote nodes. Implementors are better advised to avoid split termination with inter-media protocol translation, and use standard Internet Protocol routing instead. Abstract This document extends the Point-to-Point over Ethernet (PPPoE) Protocol with a credit-based flow control mechanism and Link Quality Metric report. This optional extension should improve the performance of PPPoE over media with variable bandwidth and limited buffering, such as mobile radio links. Berry & Holgate Informational [Page 1] RFC 4938 PPPoE with Credit Flow and Metrics June 2007 Table of Contents 1. Introduction ....................................................2 2. Payload .........................................................3 3. Overview of Protocol Extensions .................................3 4. Discovery Stage .................................................3 4.1. PPPoE Active Discovery Request (PADR) ......................4 4.2. PPPoE Active Discovery Session-confirmation (PADS) .........4 4.3. PPPoE Active Discovery Session-Grant (PADG) ................5 4.4. PPPoE Active Discovery Session-Credit Response (PADC) ......5 4.5. PPPoE Active Discovery Quality (PADQ) ......................6 5. PPP Session Stage ...............................................7 6. Credit Flow Considerations ......................................7 7. PADG and PADC Retransmission ....................................8 8. Other Considerations ............................................9 9. IANA Considerations .............................................9 10. Security Considerations ........................................9 Appendix A: Tag Values.............................................10 Appendix B: Example Message Formats................................11 Acknowledgements...................................................15 Normative References...............................................15 1. Introduction PPP over Ethernet (PPPoE) [2] is a protocol for establishing and encapsulating sessions between hosts and traffic aggregators (Access Concentrators) for PPP [1] transport over real or emulated Ethernet. PPPoE works well when both session endpoints have similar bandwidth, forwarding, and buffering capabilities that do not vary over time. However, it is insufficient for applications with variable bandwidth and limited buffering (for example, mobile radio links). This document addresses this problem by suggesting an extension to PPPoE to support credit-based session flow control and session-based link metric exchanges. The diagram below illustrates the problem that this extension is intended to solve, for the case of a radio link. Here PPPoE sessions are used between access concentrators (routers) and radio transmission systems that are shown as radio neighbors. Each radio transmission system establishes point-to-point Radio Link Protocol (RLP) sessions with its neighbors and establishes a corresponding PPPoE session for each neighbor with the transmission system's associated access concentrator (router). The radio logically associates the PPPoE session with the corresponding RLP session. Berry & Holgate Informational [Page 2] RFC 4938 PPPoE with Credit Flow and Metrics June 2007 +--------+ +-------+ +-------+ +--------+ | Access | | Host | | Host | | Access | | Conc. |=======| Radio |~~~~~~~| Radio |=======| Conc. | +--------+ +-------+ +-------+ +--------+ | | | | | |Show full document text