6LoWPAN Fragment Forwarding
draft-ietf-6lo-minimal-fragment-03
6lo T. Watteyne, Ed.
Internet-Draft Analog Devices
Intended status: Informational C. Bormann
Expires: January 22, 2020 Universitaet Bremen TZI
P. Thubert
Cisco
July 21, 2019
6LoWPAN Fragment Forwarding
draft-ietf-6lo-minimal-fragment-03
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.
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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 . . . . . . . . . . . . . . . . . . . 6
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
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