Re: Codec Negotiation Question

 
Hi Ramesh
I think you should send a "codec negotiation faliure" as response of Modify
since the codec list in modify doesnot intersect with the remote codec list
previously sent.
If you go by approach one and in your example case One gateway will move
from codec 18 to 8.
But the other gateway will not have any information about this codec change.
So, I think second approach is better.
 
Thanks
Priyanka

  _____  

From: [email protected] [mailto:[email protected]] On Behalf Of
Ramesh Babu Kuppili
Sent: Friday, October 10, 2008 10:27 AM
To: [email protected]
Cc: Murugesh Govindaraju
Subject: [Megaco] Codec Negotiation Question


Gurus,
 
I have a question about Codec Negotiation in Megaco.
 
Lets says the switch initially sends us local and remote codec list.  We
take a intersection of the both local and remote and respond to the request.
 
Then at a later stage lets says the switch sends another modify with only
local codec list.  And this time the local codec does not intersect with the
remote codec list that was received previously.
 
My question is, "How should the gateway behave to the the codec list in the
modify?".
 
1. Should it assume the the remote will also support all the codecs in the
list of Modify and respond to the modify with all supported codecs.
2. Should it send a "codec negotiation failure" as response for Modify since
the codec list in the modify does not intersect with the remote codec list
previously sent.
 
- ramesh
 
~~~~~~~~~~~~~~~~~~Example messages~~~~~~~~~~~~~~~~~~~
Request with both local and remote:
    MEGACO/1
    [172.16.43.151]
    Transaction = 58738{Context = 3{Modify = Eag26/ep2{Media{Stream =
1{LocalControl{Mode = SendReceive , ReservedValue = off , ReservedGroup =
off , tdmc/ec = on} , Local{v=0
    c=IN IP4 $
    m=audio $ RTP/AVP 18
    a=ptime:40
    v=0
    c=IN IP4 $
    m=audio $ RTP/AVP 101
    a=rtpmap:101 telephone-event/8000
    a=ptime:40
    } , Remote{v=0
    c=IN IP4 172.16.43.155
    m=audio 6024 RTP/AVP 18
    a=ptime:40
    v=0
    c=IN IP4 172.16.43.155
    m=audio 6024 RTP/AVP 101
    a=rtpmap:101 telephone-event/8000
    a=ptime:40
    }}}}}}

Request with local only:
    MEGACO/1
    [172.16.43.151]
    Transaction = 58741{Context = 3{Modify = AG26{Media{Stream =
1{LocalControl{Mode = SendReceive , tdmc/ec = off}} ,
TerminationState{Buffer = off , fax/faxstate = Negotiating}} , Events =
16777230{fax/faxconnchange , al/on , al/fl}} , Modif
    c=IN IP4 $
    m=audio $ RTP/AVP 8
    a=ptime:20
    }} , TerminationState{Buffer = off , ipfax/faxstate = Negotiating ,
ctyp/calltyp = FAX}}}}}

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