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List:       sip-implementors
Subject:    Re: [Sip-implementors] Re-transmission in T.38
From:       "Kevin P. Fleming" <kpfleming () digium ! com>
Date:       2011-01-21 13:25:48
Message-ID: 4D39895C.5080606 () digium ! com
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On 01/20/2011 11:57 PM, Manoj Priyankara [TG] wrote:

> 1. How many packets are supposed to be repeated and is the number of
> repeated packets are different from different fax signal to fax signal?
> (such as V21-preamable, cng etc)

This is not really a SIP question, it's a T.38 question.

You can choose to employ either FEC or redundancy for error protection, 
and if you choose redundancy you can choose which packets to 'repeat' 
and how many of them to 'repeat'. Many implementations do choose 
different redundancy levels for signal and data frames as you suggest.

> 2. Is this packet repetition is only relevant to the emulated modem
> signals? ( Not for the actual media)

No. You can choose to use it for either or both as your network 
requirements dictate.

-- 
Kevin P. Fleming
Digium, Inc. | Director of Software Technologies
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
skype: kpfleming | jabber: kfleming@digium.com
Check us out at www.digium.com & www.asterisk.org

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