On Forwarding 6LoWPAN Fragments over a Multihop IPv6 Network
draft-ietf-6lo-minimal-fragment-07

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6lo                                                     T. Watteyne, Ed.
Internet-Draft                                            Analog Devices
Intended status: Standards Track                         P. Thubert, Ed.
Expires: 31 May 2020                                       Cisco Systems
                                                              C. Bormann
                                                 Universitaet Bremen TZI
                                                        28 November 2019

      On Forwarding 6LoWPAN Fragments over a Multihop IPv6 Network
                   draft-ietf-6lo-minimal-fragment-07

Abstract

   This document introduces the capability to forward 6LoWPAN fragments.
   This method reduces the latency and increases end-to-end reliability
   in route-over forwarding.  It is the companion to using virtual
   reassembly buffers which is a pure implementation technique.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 31 May 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 publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Simplified BSD License text

Watteyne, et al.           Expires 31 May 2020                  [Page 1]
Internet-Draft             fragment forwarding             November 2019

   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.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  BCP 14  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Referenced Work . . . . . . . . . . . . . . . . . . . . .   3
     2.3.  New Terms . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Overview of 6LoWPAN Fragmentation . . . . . . . . . . . . . .   4
   4.  Limits of Per-Hop Fragmentation and Reassembly  . . . . . . .   6
     4.1.  Latency . . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.2.  Memory Management and Reliability . . . . . . . . . . . .   6
   5.  Forwarding Fragments  . . . . . . . . . . . . . . . . . . . .   7
   6.  Virtual Reassembly Buffer (VRB) Implementation  . . . . . . .   9
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  11
   10. Normative References  . . . . . . . . . . . . . . . . . . . .  11
   11. Informative References  . . . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

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

   This means that over a Layer-3 (route-over) network, an IP packet is
   expected to be reassembled at every hop at the 6LoWPAN sublayer,
   pushed to Layer-3 to be routed, and then fragmented again if the next
   hop is another similar 6LoWPAN link.  This draft introduces an
   alternate approach called 6LoWPAN Fragment Forwarding (FF) whereby an
   intermediate node forwards a fragment as soon as it is received if
   the next hop is a similar 6LoWPAN link.  The routing decision is made
   on the first fragment, which has all the IPv6 routing information.
   The first fragment is forwarded immediately and a state is stored to
   enable forwarding the next fragments along the same path.

   Done right, 6LoWPAN Fragment Forwarding techniques lead to more
   streamlined operations, less buffer bloat and lower latency.  It may
   be wasteful if some fragments are missing after the first one since
   the first fragment will still continue till the 6LoWPAN endpoint that