Other Translations

SIP NAT Translations

There are other translations that occur by way of SIP NAT functionality acting on the SIP R-URI, From-URI, and To URI headers. The translation of URIs in the SIP message occurs as messages are received and sent from the Oracle® Enterprise Session Border Controller’s SIP proxy. These translations create a bridge between the external and home realms and remove all references to the original IPv4 addressing from the packets sent to the destination network.

The purpose of this translation is to prevent private IPv4 addresses from appearing in SIP message URIs while traveling through the public network. This aspect of the SIP NAT’s functionality involves either translating the private address to a public address or encrypting the private address into the URI.

FQDN Mapping

The Oracle® Enterprise Session Border Controller maps FQDNs that appear in certain headers of incoming SIP messages to the IPv4 address that the Oracle® Enterprise Session Border Controller inserts in outgoing SIP contact headers. The mapped FQDNs are restored in the SIP headers in messages that are sent back to the originator.

This feature is useful to carriers that use IPv4 addresses in the SIP From address to create trunk groups in a PSX for routing purposes. When the carrier’s peer uses FQDNs, the carrier is forced to create trunk groups for each possible FQDN that it might receive from a given peer. Similarly, this can apply to SIP Contact and P-asserted-identity headers.