Duplicate SDP suppression

Asset ID:	1-72-2218281.1
Update Date:	2017-06-01
Keywords:

Solution Type Problem Resolution Sure

Solution 2218281.1 : Duplicate SDP suppression

Applies to:

Net-Net 9200 - Version S-D7.1.0 to S-D7.2.3 [Release S-D7.0]
Net-Net OS - Version S-C6.0.x to S-Cz7.4.0 [Release S-C6.0 to S-Cz7.0]
Acme Packet OS

Symptoms

In the customer's environment it was seen that the SBC receives 2 identical SDPs from the peer realm, the first one in the provisional response 183 Session Progress and the second one in the final response 200 OK.

Cause

SBC was incrementing the session version value due to the difference between in the order of the 'b' lines (bandwidth info) in SDPs, but the values are exactly the same.This behavior was not accepted by the nodes of the mobile network and therefore leads to the release of the call.

Below we can see the difference in the order of Bandwidth information line (b) in SDP of 183 Session Progress and 200 OK.

183 Session progress SDP:

-----------------------------

SDP_in_183_Session_Progress

200 OK SDP:

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Solution

Issue solved after suggesting customer to suppress the duplicate SDP.
Using the strip-dup-sdp option in the SIP configuration, you can enable your Net-Net SBC to suppress a duplicate SDP answer in the responses (1xx and 2xx) in an INVITE transaction.
Steps:
=====
1> ACMEPACKET# configure terminal

2 > ACMEPACKET(configure)# session-router

3 > ACMEPACKET(session-router)# sip-interface

If you are adding support for this feature to a pre-existing configuration, then you must select (using the ACLI select command) the configuration that you want to edit.

Ex:

ACMEPACKET (sip-interface)# select

4 > Set the options parameter by typing options, a <Space>, and then the option name "strip-dup-sdp"

Then press <Enter>

Ex:

ACMEPACKET(sip-interface)# options +strip-dup-sdp

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.

5 > Type done to save your work and continue to save and activate the configuration.

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