Network Working Group                                      B. Aboba, Ed.
Request for Comments: 4907                   Internet Architecture Board
Category: Informational                                              IAB
                                                               June 2007


             Architectural Implications of Link Indications

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).

Abstract

   A link indication represents information provided by the link layer
   to higher layers regarding the state of the link.  This document
   describes the role of link indications within the Internet
   architecture.  While the judicious use of link indications can
   provide performance benefits, inappropriate use can degrade both
   robustness and performance.  This document summarizes current
   proposals, describes the architectural issues, and provides examples
   of appropriate and inappropriate uses of link indications.























IAB                          Informational                      [Page 1]

RFC 4907                    Link Indications                   June 2007


Table of Contents

   1. Introduction ....................................................3
      1.1. Requirements ...............................................3
      1.2. Terminology ................................................3
      1.3. Overview ...................................................5
      1.4. Layered Indication Model ...................................7
   2. Architectural Considerations ...................................14
      2.1. Model Validation ..........................................15
      2.2. Clear Definitions .........................................16
      2.3. Robustness ................................................17
      2.4. Congestion Control ........................................20
      2.5. Effectiveness .............................................21
      2.6. Interoperability ..........................................22
      2.7. Race Conditions ...........................................22
      2.8. Layer Compression .........................................25
      2.9. Transport of Link Indications .............................26
   3. Future Work ....................................................27
   4. Security Considerations ........................................28
      4.1. Spoofing ..................................................28
      4.2. Indication Validation .....................................29
      4.3. Denial of Service .........................................30
   5. References .....................................................31
      5.1. Normative References ......................................31
      5.2. Informative References ....................................31
   6. Acknowledgments ................................................40
   Appendix A. Literature Review .....................................41
     A.1. Link Layer .................................................41
     A.2. Internet Layer .............................................53