LLN Minimal Fragment Forwarding
draft-ietf-6lo-minimal-fragment-00
6lo T. Watteyne, Ed.
Internet-Draft Analog Devices
Intended status: Informational C. Bormann
Expires: April 21, 2019 Universitaet Bremen TZI
P. Thubert
Cisco
October 18, 2018
LLN Minimal Fragment Forwarding
draft-ietf-6lo-minimal-fragment-00
Abstract
This document gives an overview of LLN Minimal Fragment Forwarding.
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 been always possible
with the original fragmentation design of RFC4944. This document is
a companion document to [I-D.ietf-lwig-6lowpan-virtual-reassembly],
which details the virtual Reassembly Buffer (VRB) implementation
technique which reduces the latency and increases end-to-end
reliability in route-over forwarding.
Status of This Memo
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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 . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
7. Informative References . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Overview of 6LoWPAN Fragmentation
6LoWPAN fragmentation is defined in [RFC4944]. 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.
Node A starts by compacting the IPv6 packet using header compression
defined in [RFC6282]. If the resulting 6LoWPAN packet does not fit
into a single link-layer frame, node A's 6LoWPAN sublayer cuts it
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into multiple 6LoWPAN fragments, which it transmits as separate link-
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