RE: [rohc] Constant IP-ID in the RTP Profile(0x0001)

[Biplab Sarkar <[e-mail]>]

Hi Kristofer,

Thanks for the recommendation.

I think, if we can ignore the "transparency" criteria, we can set IP-ID
to RTP-SN and DF=1  (RFC791) and compress it using ROHC. At the peer
end, seeing DF=1 will suggest the packet is not a fragmented packet so
IP-ID is not "well-defined" for that case. The IP-ID should be ignored.
Its just a way to force the receiver to ignore the IP-ID field.

It might help in a lot of situations.

Thanks & Regards
Biplab Sarkar


On Thu, 2008-01-03 at 13:01 +0100, Kristofer Sandlund wrote:

> Biplab,
> 
> I would not recommend such a behavior since that break compression
> transparency, which is bad. You can't just assume that the endpoint
> does ignore the IP-ID although that is the likely behavior.
> For 3095-based profiles, a zero IP-ID should be compressed using RND=1.
> 
> /Kristofer
> 
> Biplab Sarkar <mailto:[e-mail]> wrote on den 3
> januari 2008 12:48 :
> 
> > * PGP Signed by an unknown key: 01/03/2008 at 12:47:59 PM
> > 
> > Hi Gangadharan,
> > 
> > IP-ID can be over-written with the value of RTP-SN at the
> > compressor before compression for all "un-fragmented" IPv4
> > packets. This will enhance the compression.  Since IP-ID is
> > used in IP fragmentation, we can basically ignore its real
> > value for "un-fragmented" IP packets.
> > 
> > Thanks & Regards,
> > Biplab Sarkar
> > 
> > On Thu, 2008-01-03 at 17:07 +0530, Gangadharan G, TLS-Chennai wrote:
> > 
> > 	Hi All,
> > 
> > 
> > 
> > 	In the Linux Suse 10.1 machine, the value of the IP-ID
> > in the IPv4 header is always zero (i.e., constant) in the
> > entire IP datagrams.
> > 
> > 	The IP-ID Encoding, as per RFC 3095, of the RTP profile
> > doesn't handle this case (constant IP-ID).
> > 
> > 
> > 
> > 	Also this issue had been discussed in the mailing list.
> > 
> > 	http://www1.ietf.org/mail-archive/web/rohc/current/msg01502.html
> > 
> > 
> > 
> > 	When I searched in the Internet, I found few proposed
> > solutions (yet to read them).
> > 
> > 
> > (draft-ietf-rohc-rfc3095bis-improvements-03.txt,
> > draft-kapoor-rohc-rtp-new-requirements-00.txt
> > <http://www.potaroo.net/ietf/idref/draft-kapoor-rohc-rtp-new-r
> equirements/rfcmarkup?repository=/away/ietf&url=/away/ietf/all-ids/draft
> ->
> kapoor-rohc-rtp-new-requirements-00.txt> , 
> > 
> > 	 RFC 3643 -- A Compression Profile for IP)
> > 
> > 
> > 
> > 	Please let me know the solution/standard that everyone
> > is following for this issue in the RTP Profile.
> > 
> > 
> > 
> > 	Thanks,
> > 
> > 	Gangadharan
> > 
> > 
> > 
> > 
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