i [1] (if available in caller's RPID AVP after authentication) or From URI and user part of Request-URIi [2] (telephone number). Gateway patterns matching RPID or From URI and telephone number are ordered for forwarding purposes as follows:

• According to longest user part match
• According to priority
• Randomly

Each gateway belongs to a gateway group either alone or among other gateways. All gateways in a group share the same priority. Gateway and routing information is kept in two tables: gw and lcr.

When a gateway is selected, Request-URI is rewritten with information from gw table: URI scheme, prefix, IP address, port, and transport protocol. Valid URI scheme values are:

• NULL = sip
• 1 = sip
• 2 = sips.

If a prefix is specified it will be prepended to the Request-URI user part.

Currently valid transport protocol values are:

• NULL = none
• 1 = udp
• 2 = tcp
• 3 = tls

Table lcr contains any prefix to be applied to the user part of Request-URI, the From URI, the gateway group id, and the priority. The From URI can contain special characters % and _ matching any number of any characters and any one character, respectively.

In addition to gw and lcr tables there is third table gw_grp that is used for administrative purposes only. In this table you may map names to the gateway group ids.