On Forwarding 6LoWPAN Fragments over a Multihop IPv6 Network
draft-ietf-6lo-minimal-fragment-15
6lo T. Watteyne, Ed.
Internet-Draft Analog Devices
Intended status: Standards Track P. Thubert, Ed.
Expires: 24 September 2020 Cisco Systems
C. Bormann
Universitaet Bremen TZI
23 March 2020
On Forwarding 6LoWPAN Fragments over a Multihop IPv6 Network
draft-ietf-6lo-minimal-fragment-15
Abstract
This document provides generic rules to enable the forwarding of
6LoWPAN fragment over a route-over network. Forwarding fragments can
improve both the end-to-end latency and reliability, and reduce the
buffer requirements in intermediate nodes; it may be implemented
using RFC 4944 and virtual reassembly buffers.
Status of This Memo
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This Internet-Draft will expire on 24 September 2020.
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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. Limitations 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 . . . . . . . . . . . . . . . . . . . . . 11
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
10. Normative References . . . . . . . . . . . . . . . . . . . . 11
11. Informative References . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
The original 6LoWPAN fragmentation is defined in [RFC4944] for use
over a single Layer 3 hop, though possibly multiple Layer 2 hops in a
mesh-under network, and was not modified by the [RFC6282] update.
6LoWPAN operations including fragmentation depend on a Link-Layer
security that prevents any rogue access to the network.
In a route-over 6LoWPAN network, an IP packet is expected to be
reassembled at each intermediate hop, uncompressed, pushed to Layer 3
to be routed, and then compressed and fragmented again. This draft
introduces an alternate approach called 6LoWPAN Fragment Forwarding
(6FF) whereby an intermediate node forwards a fragment (or the bulk
thereof, MTU permitting) without reassembling if the next hop is a
similar 6LoWPAN link. The routing decision is made on the first
fragment of the datagram, which has 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. But it
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