This blog will discuss some uses of the E.164 plus (+) character that Cisco began to fully support in Cisco Unified Communications Manager (CUCM) 7.0.
The + character appears on many GSM phones sold internationally, but cannot be dialed from a hardware of software based Cisco IP phone. When a + is prefixed before dialed digit, the carrier recognizes the call as an International call without the country specific international operator dial string. International calls in the United States typically require a prefix of 011 to be recognized as an International call, while calls from Germany use the 00 digit prefix string. Both of these dial prefixes can be replaced with a + to indicate an International call as shown in the examples below:
A call from the United States to Germany without E.164 support would require the following dialed digits:
011 49 40 4589555
The same phone call with E.164 support results in the following dialed digits:
+ 49 40 4589555
Cisco phones do not support users dialing the + character, but the + character can be used in speed dials. SIP trunks and MGCP gateways support the + character used in E.164 dial plans. H.323 gateways support the International numbering plan type sent in Q.931 type of network (TON) signaling, but H.323 gateways do NOT support the + character in the calling or called party number.
Cisco Unified Communication Manager E.164 support in 7.0 and later versions include the following elements:
Route Pattern (RP)
Translation Pattern (TP)
Hunt Pilot (HP)
Directory Number (DN)
Calling and Called Party Transformations
External Phone Number Mask
CUCM has long supported the + character in the regular expression context which indicates the previous digit repeated one or more times (e.g. 9+ equals 99 or 999999). The back slash character (\) is used in many elements in CUCM to override the default regular expression behavior CUCM has typically used. The following route pattern will route calls for any pattern that begins with the + character:
\+!
The exclamation point (!) usage in CUCM indicates one or more dialed digits to match on any dial string. Exclamation points are typically used in International dial plans due to their variable length nature. The E.164 standard supports dial strings up to 15 digits in length. Feel free to share any experiences you may have had with International dial plans.