Subject: I-D Action: draft-bormann-intarea-alfi-03.txt

From: [email-masked]
Date: Sun, 10 Mar 2013 18:27:25 -0700

A New Internet-Draft is available from the on-line Internet-Drafts directories.

	Title           : Adaptation Layer Fragmentation Indication
	Author(s)       : Carsten Bormann
	Filename        : draft-bormann-intarea-alfi-03.txt
	Pages           : 10
	Date            : 2013-03-10

Abstract:
   IPv6 defines a minimum MTU of 1280 bytes.  Many link layers are more
   limited in the maximum size of packets they can communicate.  In
   order to enable the transport of IP packets that are too large for
   these link layers, typically their IP adaptation layers define a
   segmentation or fragmentation scheme to transport an IP packet in a
   sequence of multiple link layer packets.

   Often, adaption layer fragmentation schemes reduce some performance
   metric, such as the packet delivery probability.  Application or
   transport protocols may be able to reduce the maximum size of packets
   they send, e.g.  by transport layer segmentation or choice of
   application layer data object size, which may have less of a
   performance impact.  It would therefore be desirable for them to know
   about any adaptation layer fragmentation that is going on, so they
   can choose packet sizes that minimize adaptation layer fragmentation.

   At the IP layer, fragmentation can be detected using a number of
   mechanisms used in Packetization Layer Path MTU Discovery [RFC4821].
   However, adaptation layer fragmentation schemes are often designed to
   be "transparent", i.e.  there is no way at higher layers to find out
   whether they had to be employed (except maybe by elaborate
   measurement schemes targeting one of the impacted performance
   metrics; this approach does not appear to be viable) [WEI].

   The present specification defines a mechanism for IPv6 adaptation
   layers to indicate the presence of adaptation layer fragmentation on
   one or more hops on the path from an IP sender to an IP receiver, and
   to provide an indication of preferred (smaller) packet sizes on these
   hops.

   The main objective of this version of the draft is to present a
   complete design in order to be able to gauge the complexity of the
   approach against the gains to be expected from implementing it.

   Comments are appreciated and should go to the [email-masked]
   mailing list.

The IETF datatracker status page for this draft is:
https://datatracker.ietf.org/doc/draft-bormann-intarea-alfi

There's also a htmlized version available at:
http://tools.ietf.org/html/draft-bormann-intarea-alfi-03

A diff from the previous version is available at:
http://www.ietf.org/rfcdiff?url2=draft-bormann-intarea-alfi-03

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/