Cisco Unified SIP SRST 4.1
Information About Cisco Unified SIP SRST 4.1
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Cisco Unified SCCP and SIP SRST System Administrator Guide
OL-13143-04
Digit Collection on SIP Phones
Digit strings dialed by phone users must be collected and matched against predefined patterns to place
calls to the destination corresponding to the user's input. Previously, SIP phones in a
Cisco Unified SRST system required users to press the DIAL soft key or # key, or wait for the
interdigit-timeout to trigger call processing. This could cause delays in processing the call.
Two new methods of collecting and matching digits are supported for SIP phones depending on the
model of the phone:
•
KPML Digit Collection, page 77
•
SIP Dial Plans, page 77
KPML Digit Collection
The Key Press Markup Language (KPML) uses SIP SUBSCRIBE and NOTIFY methods to report user
input digit by digit. Each digit dialed by the phone user generates its own signaling message to
Cisco Unified SRST, which performs pattern recognition by matching a destination pattern to a dial peer
as it collects the dialed digits. This process of relaying each digit immediately is similar to the process
used by SCCP phones. It eliminates the need for the user to press the Dial soft key or wait for the
interdigit timeout before the digits are sent to the Cisco Unified SRST for processing.
KPML is supported on Cisco Unified IP Phones 7911G, 7941G, 7941GE, 7961G, 7961GE, 7970G, and
7971GE. For configuration information, see the
“Enabling KPML for SIP Phones” section on page 79
.
SIP Dial Plans
A dial plan is a set of dial patterns that SIP phones use to determine when digit collection is complete
after a user goes off-hook and dials a destination number. Dial plans enable SIP phones to perform local
digit collection and recognize dial patterns as user input is collected. After a pattern is recognized, the
SIP phone sends an INVITE message to Cisco Unified SRST to initiate the call to the number matching
the user's input. All of the digits entered by the user are presented as a block to Cisco Unified SRST for
processing. Because digit collection is done by the phone, dial plans reduce signaling messages overhead
compared to KPML digit collection.
SIP dial plans eliminate the need for a user to press the Dial soft key or # key or to wait for the interdigit
timeout to trigger an outgoing INVITE. You configure a SIP dial plan and associate the dial plan with a
SIP phone. The dial plan is downloaded to the phone in the configuration file.
You can configure SIP dial plans and associate them with the following SIP phones:
•
Cisco Unified IP Phone 7911G, 7941G, 7941GE, 7961G, 7961GE, 7970G, and 7971GE: These
phones use dial plans and support KPML. If both a dial plan and KPML are enabled, the dial plan
has priority.
If a matching dial plan is not found and KPML is disabled, the user must wait for the interdigit
timeout before the SIP NOTIFY message is sent to Cisco Unified SRST. Unlike other SIP phones,
these phones do not have a Dial soft key to indicate the end of dialing, except when on-hook dialing
is used.
•
Cisco Unified IP Phone 7905, 7912, 7940, and 7960: These phones use dial plans and do not support
KPML. If you do not configure a SIP dial plan for these phones, or if the dialed digits do not match
a dial plan, the user must press the Dial soft key or wait for the interdigit timeout before digits are
sent to Cisco Unified SRST for processing.
