PPP over Ethernet (PPPoE) Extensions for Credit Flow and Link Metrics
RFC 5578

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Independent Submission                                     B. Berry, Ed.
Request for Comments: 5578                                    S. Ratliff
Obsoletes: 4938                                              E. Paradise
Category: Informational                                            Cisco
ISSN: 2070-1721                                                T. Kaiser
                                                      Harris Corporation
                                                                M. Adams
                                                       L3 Communications
                                                           February 2010

 PPP over Ethernet (PPPoE) Extensions for Credit Flow and Link Metrics

Abstract

   This document extends the Point-to-Point Protocol over Ethernet
   (PPPoE) with an optional credit-based flow control mechanism and an
   optional Link Quality Metric report.  These optional extensions
   improve the performance of PPPoE over media with variable bandwidth
   and limited buffering, such as mobile point-to-point radio links.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This is a contribution to the RFC Series, independently of any other
   RFC stream.  The RFC Editor has chosen to publish this document at
   its discretion and makes no statement about its value for
   implementation or deployment.  Documents approved for publication by
   the RFC Editor are not a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   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/rfc5578.

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

Berry, et al.                 Informational                     [Page 1]
RFC 5578           PPPoE with Credit Flow and Metrics      February 2010

   nodes.  Implementors are better advised to avoid split termination
   with inter-media protocol translation, and use standard Internet
   Protocol routing instead.

Copyright Notice

   Copyright (c) 2010 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.

Table of Contents

   1. Introduction ....................................................3
   2. Terminology .....................................................4
   3. Overview of Protocol Extensions .................................5
      3.1. TLVs .......................................................5
           3.1.1. Credits TLV .........................................5
           3.1.2. Metrics TLV .........................................6
           3.1.3. Sequence Number TLV .................................7
           3.1.4. Credit Scale Factor TLV .............................8
      3.2. Discovery Stage Extensions .................................8
           3.2.1. PPPoE Active Discovery Request (PADR) ...............9
           3.2.2. PPPoE Active Discovery Session-Confirmation
                  (PADS) .............................................11
           3.2.3. PPPoE Active Discovery Session-Grant (PADG) ........13
           3.2.4. PPPoE Active Discovery Session-Credit
                  Response (PADC) ....................................15
           3.2.5. PPPoE Active Discovery Quality (PADQ) ..............16
      3.3. PPP Session Stage Extensions ..............................18
   4. Credit Flow Considerations .....................................19
   5. PADG and PADC Retransmission ...................................20
   6. Other Considerations ...........................................20
   7. IANA Considerations ............................................21
   8. Security Considerations ........................................21
   9. References .....................................................21
      9.1. Normative References ......................................21
      9.2. Informative References ....................................21
   Appendix A. Examples of Session Credit Flows ......................22