SIP Duplicate SDP Suppression

Using the strip-dup-sdp option in the SIP configuration, you can enable your Oracle® Enterprise Session Border Controller to suppress a duplicate SDP answer in the reliable responses (1xx and 2xx) in an INVITE transaction.

During INVITE transactions in certain networks, SDP answers in reliable provisional responses (1xx) can cause interoperability issues. This issue occurs when the UAS includes the SDP answer in subsequent 1xx responses or in the final 2xx response, and the UAC views that inclusion as a protocol violation. The UAC does so based on the fact that the SDP answer was reliably delivered to it in a 1xx response, and so it views additional SDP information as unnecessary in and ensuing reliable 1xx or 200 OK responses.

RFCs 3216 and 3262 do not specifically call out the UAS’s including SDP information in this way as a protocol violation. Still, the system allows you set enable the strip-dup-sdp option as a means of preventing the UAC from terminating sessions. With this option enabled, the Oracle® Enterprise Session Border Controller removes the SDP answer in subsequent reliable provisional or final 200 OK responses if it is identical to the SDP answer previously received.

SIP Duplicate SDP Suppression Configuration

To enable duplicate SDP suppression for SIP sessions:

In Superuser mode, type configure terminal and press Enter.
```
ORACLE# configure terminal
```

Type session-router and press Enter.

ORACLE(configure)# session-router
ORACLE(session-router)#

Type sip-config and press Enter.
```
ORACLE(session-router)# sip-config
ORACLE(sip-config)#
```
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.
options—Set the options parameter by typing options, a Space, and then the option name strip-dup-sdp. Then press Enter.
```
ORACLE(sip-config)# 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.