PPP Over Ethernet (PPPoE) Extensions for Credit Flow and Link Metrics
RFC 4938
| Document | Type |
RFC - Informational
(June 2007; Errata)
Obsoleted by RFC 5578
|
|
|---|---|---|---|
| Last updated | 2015-10-14 | ||
| Stream | ISE | ||
| Formats | plain text pdf html bibtex | ||
| Stream | ISE state | (None) | |
| Consensus Boilerplate | Unknown | ||
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 4938 (Informational) | |
| 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 |
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