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Early Media enable/disable

Alan Couto
Level 1
Level 1

Hello friends,

About Early Media:

Early Media allows the sending of media from the called party or an application server to the caller, even before
the call is accepted. The most common reasons for using Early Media include the following:
• The called device might want to establish an Early Media RTP path to reduce the effects of audio cut-through
delay (clipping) for calls experiencing long signaling delays or to provide a network-based voice message
to the caller.

Question: There's any way to check if Early Media is enabled or not at the router?  Aditionally, there's any command to enable/disable Early Media?

Thanks,

Alan.

2 Accepted Solutions

Accepted Solutions

Abdel.

Early offer and early media are two totally different things.

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View solution in original post

If you are not receiving 183 with SDP, then you cant do early media. You need either 180 with sdp or 183 with SDP. Your sip server need to send 183 with SDP..

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View solution in original post

20 Replies 20

is this what are you looking for?

http://www.cisco.com/c/en/us/td/docs/ios/voice/command/reference/vr_book/vr_d2.html#wp1452642

Hello Rolando,

As I understood about this document is to disable the SDP at the 180 Ringing, right? This is not a problem at this moment. I can't even see the 183 Session Progress. And according to this document this is normal call flow with Early media:

http://www.cisco.com/c/en/us/td/docs/routers/asr1000/configuration/guide/sbcu/2_xe/sbcu_2_xe_book/sbc_ear.html

Hello Alan, 

I think Jaime provided you a good link to check and enable/enforce Earlly media on 4451. It is in the Command of Voice-class "voice-class sip early-offer forced " per dial-peer or "early-offer forced" in global configurations . 

Abdel-moniem E. REZK

http://ucjournal.net

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Abdel.

Early offer and early media are two totally different things.

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Hi Ayodeji, 

Thank you, true yes. I got distracted here. The Early Media should be supported by default I believe, Provisional responses enforcement can be enabled here as you have shown. 

Thanks for the correction

Abdel-moniem E. REZK

If you are not receiving 183 with SDP, then you cant do early media. You need either 180 with sdp or 183 with SDP. Your sip server need to send 183 with SDP..

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Hello aokanlawon,

Thanks again for the attention at this discussion. May help lots of people.

One more question: Is there any parameter received by router that confirms that the call is a early media session? Or just the presence of 183 or 180 with SDP already justify it?

See attached debug where client not sure if sip server is sending or not early media to router.

This trace you provide shows the inbound direction of the call..In this we can see that the gateway sends a normal 180 ringing. We need to see what the SIP server sends in response to an outbound call to it. Thats when we will know if it sends early media or not..

000136: *Nov 13 14:10:26.016: //168/1EE9F0B180AD/SIP/Msg/ccsipDisplayMsg:
Sent:
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP 172.17.240.49:5069;branch=z9hG4bK051b615swcizbkcx0x0xz106y
From: <sip:2121011554@172.26.0.142;user=phone>;tag=1bsxxss0-CC-22
To: <sip:37991400@172.17.240.49;user=phone>;tag=32FA24-16FC
Date: Fri, 13 Nov 2015 14:10:25 GMT
Call-ID: kw6bkmcmu6mkikc6jc5j10jjiky0sj61@SoftX3000
CSeq: 1 INVITE
Require: 100rel
RSeq: 8328
Allow: INVITE, OPTIONS, BYE, CANCEL, ACK, PRACK, UPDATE, REFER, SUBSCRIBE, NOTIFY, INFO, REGISTER
Allow-Events: telephone-event
Remote-Party-ID: <sip:37991400@192.168.15.18>;party=called;screen=no;privacy=off
Contact: <sip:37991400@192.168.15.18:5060>
Server: Cisco-SIPGateway/IOS-15.5.2.S
Content-Length: 0


000137: *Nov 13 14:10:26.310: //-1/xxxxxxxxxxxx/SIP/Msg/ccsipDisplayMsg:
Received:
PRACK sip:37991400@192.168.15.18:5060 SIP/2.0
Via: SIP/2.0/UDP 172.17.240.49:5069;branch=z9hG4bK0ikji5mws1iy05mysk5sk5j0k
Call-ID: kw6bkmcmu6mkikc6jc5j10jjiky0sj61@SoftX3000
From: <sip:2121011554@172.26.0.142;user=phone>;tag=1bsxxss0-CC-22
To: <sip:37991400@172.17.240.49;user=phone>;tag=32FA24-16FC
CSeq: 2 PRACK
Max-Forwards: 70
RAck: 8328 1 INVITE
Content-Length: 0

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Hello aokanlawon,

See the outbound call debug attached. Also without 183/180 with SDP.

Thanks,

Alan.

Hi Alan,

As we can see now, there is no early media in the response. its only 180 ringing..

So you need to enage your sip server providers on this..

Received:
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP 192.168.15.18:5060;branch=z9hG4bK2BDE
Call-ID: C6BA7046-8D4711E5-8073B143-7C278D9C@192.168.15.18
From: <sip:2137991400@192.168.15.18>;tag=1C17B9-AF5
To: <sip:21011554@172.17.240.49>;tag=0sckwuym-CC-22
CSeq: 101 INVITE
Contact: <sip:21011554@172.17.240.49:5060;user=phone>
Allow: INVITE,ACK,OPTIONS,BYE,CANCEL,REGISTER,INFO,PRACK,SUBSCRIBE,NOTIFY,UPDATE,MESSAGE,REFER
Content-Length: 0

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Hello aokanlawon,

Thanks again. I took a look at this documment. This may don't accur because it is configured as Early Media (early offer) ? I tried to find any command to force Early Media with delayed offer but didn't find.

"With Early Offer (default on Cisco gateways), the SDP offer is carried in the INVITE message. In Early Media with Delayed Offer, both messages can transport the initial SDP offer: 183 Session Progress response or
180 Ringing response. 183 Session Progress is stipulated by the IETF and is more common."

Alan.

Both calls in the logs use early offer so this is not an issue. The SIP server needs to send early offer and then the gateway will cut through audio and listen to whatever the far end is sending..

Please read more here..

http://www.cisco.com/c/en/us/td/docs/routers/asr1000/configuration/guide/sbcu/2_xe/sbcu_2_xe_book/sbc_ear.html

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Hello aokanlawon,

Just to clarify.

Accordig to the documments, the called device decides if the call will be early media or not, right?

So I understand that if sip-server respond a 183 Session Progress with SDP. Cisco router will treat the call as early media. (Cisco router - to sip-server) - OK.

How about when the call is inbound (sip server to Cisco router). The Cisco router can also "start" Early Media and respond to a 183 Session Progress with SDP? This make sense?

Thanks again for your patience.

Alan.

That is a good question, however I don't think that the gateway can do that on its own. With cucm you can enabled early media and thus the gateway would initiate early media. If you read that documentation again you will notice it keeps inferring that the gateway will respond when it gets early media, not initiate it. 

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