Does rohc place an upper bound on the compressed header size? It seems the easiest/safest thing to do will be to use this in the determination of MTU, and apply this MTU uniformly.
-John On Mon, May 18, 2009 at 6:33 AM, Magnus Westerlund <[email protected]> wrote: > This email is BCC to a number of list. Please respond to the TSV-area list. > > In the AD review of the documents for defining Robust Header Compression > (ROHC) over IPsec: http://tools.ietf.org/wg/rohc/draft-ietf-rohc-hcoipsec/ > > I picked up on a issue that has been mentioned before but not really > been dealt with. Namely the varying MTU for packets entering this tunnel. > > So this work is to enable so that ROHC can compress the inner IP, > transport, etc headers inside an IPsec tunnel to save bandwidth that > way. ROHC is a stateful compression technology which can result in that > the headers being compressed can be both slightly bigger as well as much > smaller. Thus the effective MTU for a particular packet inside an IPsec > tunnel with ROHC varies depending on which packet in a sequence it is. > This will create some issues for any path MTU discovery mechanism, where > a smaller packet may result in a ICMP TOO BIG while a slightly larger > packet doesn't. > > So I am interested in what issues you see arising with this technology > and what you think should be done about it. > > Cheers > > Magnus Westerlund > > IETF Transport Area Director & TSVWG Chair > ---------------------------------------------------------------------- > Multimedia Technologies, Ericsson Research EAB/TVM > ---------------------------------------------------------------------- > Ericsson AB | Phone +46 10 7148287 > Färögatan 6 | Mobile +46 73 0949079 > SE-164 80 Stockholm, Sweden| mailto: [email protected] > ---------------------------------------------------------------------- >
