Subject: [rohc] Clarrification needed regarding Multiple IP levels handling in IP Profile.

From: "narendranv" <[email-masked]>
Date: Mon, 6 Apr 2009 15:22:45 +0530

Dear RoHCers,

I need clarrification regarding handling of Multiple IP Levels in
Profile -0x0004.

Let us assume 3 level IP as Input IP Packet:

            Outermost Ip        Outer IP level            Innermost IP level

RFC3843 says : Sec3.2. Handling Multiple Levels of IP Headers:

"   The IP-only profile defined in this document goes one step further

   and supports compression of an arbitrary number of IP levels.  This

   is achieved by adding a dynamic chain to the general format of

   compressed headers, to include the header part of each IP level in

   excess of the first two."

 "   For compressed headers, the information related to the initial two IP

   headers is carried as for the IP/UDP profile, and a chain of dynamic

   header information is added to the end of the compressed header for

   each and every additional IP header.  "

Q.1) Which IP level should be considered as Additional IP Level in Profile-
0x004.

     Is "IP1" considered as Additional level or "IP3" should be considered
as Additional

     level for Implementation?

Q.2) Is this interpretation correct?

     IP2 and IP3 levels are compressed and respective fileds are filled in
the compressed header

     and IP1 is added as additonal dynamic chain at the end of general
format of compressed header.

Pls share your valuable opinions on the same.

Thanks & Regards,

Narendran.

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