[rohc] RE: TCP/IP EPIC profile

["Surtees, Abigail" <[e-mail]>]

Hi Maja,
 
Thanks for your email.  The U method is a new one which is defined in the latest version of the EPIC-LITE draft.  This can be found at http://www.dmn.tzi.org/ietf/rohc/draft-ietf-rohc-epic-lite-01.txt <http://www.dmn.tzi.org/ietf/rohc/draft-ietf-rohc-epic-lite-01.txt> .
 
You are correct tcp-generic-co is called that because it isn't defined by any of the 6 values so it can be any other tcp option.  Each item in LIST can only occur once so if there were to be 2 tcp options which weren't any of the specified 6 then 2 generic option items are needed.  A similar thing happens in the LIST for sack blocks.
 
I hope this answers your questions.
 
Regards,
 
Abbie
 
 

-----Original Message-----
From: Maja [mailto:[e-mail]]
Sent: 04 March 2002 16:33
To: rohc
Cc: Surtees, Abigail; West, Mark (ITN)
Subject: TCP/IP EPIC profile



Hi all,
some points in the latest TCP/IP Header Compression for ROHC (ROHC-TCP) <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
draft from January are not clear (OK. Not clear to me ).
 
First is the definition of the U ( ) method called for TCP options, for example:
 
  tcp-options-co  =    ROTATE(3,1) ; get TCP data offset 
                        LIST(4,1,32,-160,8, 
                           U(OPTIONAL(tcp-sack-co)), 
                           U(OPTIONAL(tcp-timestamp-co)), 
                           U(OPTIONAL(tcp-mss)), 
                           U(OPTIONAL(tcp-end)), 
                           U(OPTIONAL(tcp-wscale)), 
                           U(OPTIONAL(sack-permitted)), 
                           U(OPTIONAL(tcp-generic-co)), 
                           U(OPTIONAL(tcp-generic-co)), 
                           5,8,2,0,3,4) 
 
We couldn't find it in none of the EPIC or ROHC drafts.
And the second point is why is it, in the method LIST, twice included tcp-generic-co ( OR for IR/DYN tcp-generic-dyn).
We suppose that is the method which is called if the value in 8 bits is none of 6 values stated at the end of method, but why twice?
 
Cheers,
 
Maja & Ivana