Symmetric Latching

Symmetric latching, or forced HNT, ensures that symmetric RTP/RTCP is used for a SIP endpoint. Symmetric RTP/RTCP means that the IP address and port pair used by an outbound RTP/RTCP flow is reused for the inbound flow. The IP address and port are learned when the initial RTP/RTCP flow is received by the Oracle® Enterprise Session Border Controller. The flow's source address and port are latched onto and used as the destination for the RTP/RTCP sourced by the other side of the call. The IP address and port in the c line and m line respectively in the SDP message are ignored.

If your network is configured with nested realms in order to separate signalling from media, make sure that the symmetric latching feature is enabled on the signaling realm.

Note:

This description is applicable to RTCP only when you also enable the HNT RTCP option in the media-manager configuration. Do not enable symmetric latching on core-facing interfaces.

Symmetric Latching Configuration

To configure symmetric latching:

1. Access the realm-config configuration element.

   ORACLE# configure terminal
   ORACLE(configure)# media-manager
   ORACLE(media-manager)# realm-config
   ORACLE(realm-config)# 

2. Select the realm-config object to edit.

   ORACLE(realm-config)# select
   identifier:
   1: realm01 left-left:0 0.0.0.0
   
   selection: 1
   ORACLE(realm-config)#

3. symmetric-latching — identifies whether and how to enable symmetric latching on the SBC. This completes the configuration of forced Hosted NAT Traversal (HNT). The default value for this parameter is disabled. The valid values are:
   • disabled —
   • enabled —

   • pre-emptive —

     ORACLE(realm-config)# symmetric-latching pre-emptive

4. Type done to save your configuration.

Enabling RTCP Latching

To enable RTCP symmetric latching:

1. In Superuser mode, type configure terminal and press Enter.

   ORACLE# configure terminal

2. Type media-manager and press Enter to access the media-level configuration elements.

   ORACLE(configure)# media-manager
   ORACLE(media-manager)#

3. Type media-manager and press Enter. The system prompt changes to let you know that you can begin configuring individual parameters.

   ORACLE(media-manager)# media-manager
   ORACLE(media-manager-config)#

4. Select the media manager configuration so that you can enable HNT RTCP.

   ORACLE(media-manager-config)# select

5. hnt-rtcp — Enable support of RTCP when the SBC performs HNT. The default value is disabled. The valid values are:

   • enabled | disabled

     ORACLE(media-manager-config)# hnt-rtcp enabled

6. Save your work using either the ACLI save or done command.