[rohc] Clarification Required regarding the Context Replication

Anil Maguluri <Anil.Maguluri@lntinfotech.com> Fri, 25 June 2010 12:09 UTC

From: Anil Maguluri <Anil.Maguluri@lntinfotech.com>
To: "rohc@ietf.org" <rohc@ietf.org>
Date: Fri, 25 Jun 2010 17:39:13 +0530
Thread-Topic: Clarification Required regarding the Context Replication
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Cc: Anil Kumar Maguluri <anilmaguluri@gmail.com>
Subject: [rohc] Clarification Required regarding the Context Replication
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Hi All,

I am implementing the Context Replication mechanism for TCP (ROHCv2 Profile-6).
Please clarify me whether my understanding is right or not.

1. When Base CID will be same as CID ?

As per my understanding the scenario will be: All the CID's are used at the compressor

and it received a new flow. At that time compressor will check which CID is idle, so that

it can use that CID for the new flow instead of sending as Profile-4 or Profile-0 based on

the supported profiles.

a. Is my understanding is right?

b. Is there any other scenario where Base CID = CID?

c. Should I reset the compressor/decompressor context (Mode, State, Counters) if the

Base CID = CID?

As per my understanding, we should not reset the context (Mode, State, Counters).

"RFC 4996,

6.1.1. Master Sequence Number (MSN):

When the MSN is initialized, it SHOULD be initialized to a random value. The compressor should

only initialize a new MSN for the initial IR or IR-CR packet sent for a CID that corresponds to a

context that is not already associated with this profile. In other words, if the compressor reuses

the same CID to compress many TCP flows one after the other, the MSN is not reinitialized but

rather continues to increment monotonically.

For context replication, the compressor does not use the MSN of the base context when sending

the IR-CR packet, unless the replication process overwrites the base context (i.e., Base CID == CID).

Instead, the compressor uses the value of the MSN if it already exists in the ROHC-TCP context

being associated with the new flow (CID); otherwise, the MSN is initialized to a new value.

d. Should we start the Heuristics for the new flow if BCID = CID?

As per my understanding, we should not start the Heuristics in case of BCID = CID, but we should do the Heuristics is BCID != CID?

Is my understanding is right?

Thanks for your support.

Regards,
Anil Kumar Maguluri

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[rohc] Clarification Required regarding the Conte… Anil Maguluri