Acme Packet 4600
 

PLA-Support>Sun Systems>CommsGBU>Session Delivery Network>SN-SND: Acme Service Provider
 

SBC is not forwarding media from core to access.

In this Document

Symptoms

Changes

Cause

Solution

Created from <SR 3-14011312558>

Applies to:

Symptoms

 One-way Audio. SBC is not forwarding the audio from IVR to endpoints.

Changes

New implementation

Cause

Customer is having the below call flow :

A --------| x--- SBC ----y | ----------- B

A is behind NAT, as the Layer 3 IP is public and the application IP's are private - such as contact and via.
x and y are sip interface of SBC respectively.

Here the sip-interface x's realm also has NAT-TRAVERSAL enabled.

Since the endpoint is behind NAT and even though the sip-interface realm - x has symmetric-latching disabled, SBC will use symmteric latching as NAT Traversal is enabled.

In this case it will wait for the first RTP from A, so that it can update the CAM table with ip and port details.

Now A is calling B and B is sending 183 with SDP - sendonly and start sending RTP. Since, SBC is waiting for RTP from A, it will not forward the RTP from B till it receives A details (symmetric latching effect).

If customer makes call from B to A there is no issue as A sends the RTP and the media is exchanged in both directions.

Solution

Please navigate to configure terminal -> session-router -> sip-config. In sip-config you need to add drain-sendonly under option* parameter.

By this, SBC will change 183 - sendonly to 183 - sendrcv and then A will send RTP or RTCP details.

The SBC cam will have endpoint A's ip-address and port details to forward the media.

*P.S - If you type the option without the plus sign, you will overwrite any previously configured options. In order to append the new options to this configuration’s options list, you must prepend the new option with a plus sign as shown in the previous example.

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