Subject: [rohc] S-NACK pkt

From: "Sarkar, Biplab" <[email-masked]>
Date: Tue, 10 Oct 2006 18:23:16 +0530

ROCHers,

I have a doubt. 

What is the significance of "SN" field in a feedback-2 pkt for RTP
profile when STATIC_NACK is sent? 

I think SN has some significance only for ACK pkts. 

When STATIC_NACK is sent, does it mean the decompressor has lost all
context information (CIDs)? Or just a particular context (CID) has gone
corrupt? 

Please clarify.

Thanks

Biplab

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From: "Lars-Erik Jonsson \(LU/EAB\)" <[email-masked]>
Date: Tue, 10 Oct 2006 15:15:44 +0200

> What is the significance of "SN" field in a feedback-2 pkt
> for RTP profile when STATIC_NACK is sent?

According to 3095: "...the sequence number to use is that
of the last successfully decompressed header. If no sequence
number is available, the feedback MUST carry a SN-NOT-VALID
option."

How the compressor make use of the ACK/NACK/S-NACK information
is up to implementation. 

> When STATIC_NACK is sent, does it mean the decompressor has
> lost all context information (CIDs)? Or just a particular
> context (CID) has gone corrupt?

All ACKs and NACKs are referring to a specific context.

BR
/L-E