LLN Fragment Forwarding and Recovery
draft-thubert-6lo-forwarding-fragments-05

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6lo                                                      P. Thubert, Ed.
Internet-Draft                                             Cisco Systems
Updates: 4944 (if approved)                                       J. Hui
Intended status: Standards Track                               Nest Labs
Expires: October 8, 2017                                   April 6, 2017

                  LLN Fragment Forwarding and Recovery
               draft-thubert-6lo-forwarding-fragments-05

Abstract

   Considering that an LLN link-layer frame can have a payload below 100
   bytes, an IPv6 packet might be fragmented more than 10 fragments at
   the 6LoWPAN layer.  In a 6LoWPAN mesh-under mesh network, the
   fragments can be forwarded individually across the mesh, whereas a
   route-over mesh network, a fragmented 6LoWPAN packet must be
   reassembled at every hop, which causes latency and congestion.  This
   draft introduces a simple protocol to forward individual fragments
   across a route-over mesh network, and, regardless of the type of
   mesh, recover the loss of individual fragments across the mesh and
   protect the network against bloat with a minimal flow control.

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   Copyright (c) 2017 IETF Trust and the persons identified as the
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   This document is subject to BCP 78 and the IETF Trust's Legal
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   (http://trustee.ietf.org/license-info) in effect on the date of

Thubert & Hui            Expires October 8, 2017                [Page 1]
Internet-Draft    LLN Fragment Forwarding and Recovery        April 2017

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Updating RFC 4944 . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Terminology and Referenced Work . . . . . . . . . . . . . . .   4
   4.  New Dispatch types and headers  . . . . . . . . . . . . . . .   5
     4.1.  Recoverable Fragment Dispatch type and Header . . . . . .   5
     4.2.  RFRAG Acknowledgment Dispatch type and Header . . . . . .   6
   5.  Fragments Recovery  . . . . . . . . . . . . . . . . . . . . .   8
   6.  Forwarding Fragments  . . . . . . . . . . . . . . . . . . . .   9
     6.1.  Upon the first fragment . . . . . . . . . . . . . . . . .  10
     6.2.  Upon the next fragments . . . . . . . . . . . . . . . . .  11
     6.3.  Upon the RFRAG Acknowledgments  . . . . . . . . . . . . .  11
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  12
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  12
     10.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Appendix A.  Rationale  . . . . . . . . . . . . . . . . . . . . .  14
   Appendix B.  Requirements . . . . . . . . . . . . . . . . . . . .  16
   Appendix C.  Considerations On Flow Control . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   In most Low Power and Lossy Network (LLN) applications, the bulk of
   the traffic consists of small chunks of data (in the order few bytes
   to a few tens of bytes) at a time.  Given that an IEEE Std. 802.15.4
   [IEEE.802.15.4] frame can carry 74 bytes or more in all cases,
   fragmentation is usually not required.  However, and though this
   happens only occasionally, a number of mission critical applications
   do require the capability to transfer larger chunks of data, for
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