6LoWPAN Fragment Forwarding
draft-ietf-6lo-minimal-fragment-04

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6lo                                                     T. Watteyne, Ed.
Internet-Draft                                            Analog Devices
Intended status: Informational                                C. Bormann
Expires: March 2, 2020                           Universitaet Bremen TZI
                                                              P. Thubert
                                                                   Cisco
                                                         August 30, 2019

                      6LoWPAN Fragment Forwarding
                   draft-ietf-6lo-minimal-fragment-04

Abstract

   This document provides a simple method to forwarding 6LoWPAN
   fragments.  When employing adaptation layer fragmentation in 6LoWPAN,
   it may be beneficial for a forwarder not to have to reassemble each
   packet in its entirety before forwarding it.  This has always been
   possible with the original fragmentation design of RFC4944.  This
   method reduces the latency and increases end-to-end reliability in
   route-over forwarding.  It is the companion to the virtual Reassembly
   Buffer which is a pure implementation technique.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on March 2, 2020.

Copyright Notice

   Copyright (c) 2019 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
   (https://trustee.ietf.org/license-info) in effect on the date of

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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Overview of 6LoWPAN Fragmentation . . . . . . . . . . . . . .   2
   2.  Limits of Per-Hop Fragmentation and Reassembly  . . . . . . .   4
     2.1.  Latency . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Memory Management and Reliability . . . . . . . . . . . .   4
   3.  Virtual Reassembly Buffer (VRB) Implementation  . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   6
   7.  Informative References  . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Overview of 6LoWPAN Fragmentation

   The original 6LoWPAN fragmentation is defined in [RFC4944] and it is
   implicitly defined for use over a single IP hop though possibly
   multiple Layer-2 hops in a meshed 6LoWPAN Network.  Although
   [RFC6282] updates [RFC4944], it does not redefine 6LoWPAN
   fragmentation.

   We use Figure 1 to illustrate 6LoWPAN fragmentation.  We assume node
   A forwards a packet to node B, possibly as part of a multi-hop route
   between IPv6 source and destination nodes which are neither A nor B.

                  +---+                     +---+
           ... ---| A |-------------------->| B |--- ...
                  +---+                     +---+
                                 # (frag. 5)

                123456789                 123456789
               +---------+               +---------+
               |   #  ###|               |###  #   |
               +---------+               +---------+
                  outgoing                incoming
             fragmentation                reassembly
                    buffer                buffer

         Figure 1: Fragmentation at node A, reassembly at node B.

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   Node A starts by compacting the IPv6 packet using the header
   compression mechanism defined in [RFC6282].  If the resulting 6LoWPAN
   packet does not fit into a single link-layer frame, node A's 6LoWPAN