LRT Lookup Key Creation

This section describes the Oracle® Enterprise Session Border Controller’s LRT lookup key creation capability.

Arbitrary LRT Lookup Key

In addtion to the standard From, To, and and P-Asserted-Identity header fields the Oracle® Enterprise Session Border Controller can now use the values from any arbitrary SIP header as an LRT or ENUM lookup key. This is preformed by prepending a dollar sign $ by the header name whose value’s userinfo portion of the URI will be used as the lookup key. For example, key=$Refer-To would use the userinfo portion of the URI in the Refer-To header of the request as the lookup key.

An ampersand & followed by a header name will use the whole value of the header as the lookup key. For example, key=&X-Route-Key would use the whole value of the X-Route-Key as the lookup key. As a shortcut, an ampersand is not required for a "hidden" header. For example, "key=@LRT-Key" would use the value of the @LRT-Key header as the lookup key.

Hidden Headers for HMR and LRT lookup

When an LRT lookup key is more complex than just the URI’s userinfo or a Tel-URI, HMR can be used to extract the data and build a special header.

By using a header name that begins with the at-sign ”@” (e.g. @lrt-key), the header can be hidden and not included in outgoing SIP message, thus eliminating the need for an extra HMR rule to remove it.

Since '@' is not a valid character in a header name as defined by RFC 3261, there is no possibility of a collision between a header name defined in the future and a hidden header name beginning with @.

Compound Key LRT Lookup

LRT lookup keys can be combinations of more than one key value. For example, "key=$FROM,$TO" would construct a compound key with the userinfo of the From URI followed by a comma flowed by the userinfo of the To URI.

If the request message contained:

From: <sip:[e-mail]>
To: <sip:[e-mail]>

The compound key to match this From/To pair is "1234,5678".

In the table lookup, the compound key is a single key value and there is no special treatment of the comma in key matching. The comma is simply an ordinary additional character that is matched like any letter or digit (i.e. the comma must appear in the LRT entry's "type" element data). For example, if the table were configured for "best" match-mode, the lookup key "1234,5678" would match a table entry of "1234,567", but it would not match a table entry of "123,5678".