Subject: [rohc] Queries from a beginner

From: [email-masked]
Date: Fri, 24 Jul 2009 15:33:56 +0100 (BST)

Hello all,
          I am new to research in the Header Compression field and I have
been trying to get my head around the RFC. If anyone can answer
the following queries, it would be much appreciated.
Just to set the scenario first, I am at the moment just looking into IP
header compression in Uni-directional Mode.
1.)The RFC says that in Uni-directional mode, the compression moves
between IR and normal packet mode.
             a.)So my question is what is the packet header size for these
packets?
             b.) Can IR-Dyn packets be used as well?
2.) The RFC also says that for each compression mode there are three
states (IR,FO,SO),so if I were to apply this for Uni-directional mode.
            c.) What is the SO mode packet that will be sent?i.e., if IR=
normal packet, FO = IR packet, does SO = IR-Dyn packet?
3.) What are the respective header sizes for all these packets?
Cheers
Nikhil

---

From: Ang Way Chuang <[email-masked]>
Date: Sat, 25 Jul 2009 11:39:26 +0800

Hi Nikhil,

	Inlined are the brief explanations according to my limited 
understanding on the subject.

>              a.)So my question is what is the packet header size for these

It depends on the profile being used and the packet type.

>              b.) Can IR-Dyn packets be used as well?

IR-DYN is normally used when the compressor is in IR state.

> normal packet, FO = IR packet, does SO = IR-Dyn packet?

I may be wrong about this. IR = IR & IR-DYN, SO = type 0, FO = other 
type not covered by IR & SO. I think the RFC never explicitly state the 
packet types for SO and FO state. So, it is very subjective.

> 3.) What are the respective header sizes for all these packets?

It depends on the profile being used and the characteristics of the 
traffic. Section 5.7 explains the packet types for RTP profile.

> Cheers
> Nikhil
> 
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