Cisco Unified Communications Solutions unify voice, video, data, and mobile applications on fixed and mobile networks, enabling easy collaboration every time from any workspace.
As the enterprise extends its IP telephony deployments from central sites to remote branch offices and teleworkers, a critical factor in achieving a successful deployment is the capability to support backup call control at these remote locations. Cisco Unified Survivable Remote Site Telephony (SRST) provides a cost-effective solution for supporting redundant call control in remote branch offices and the homes of teleworkers.
Benefits of Centralized Call-Processing Architecture
Cisco Unified SRST is a critical component of a centralized call-processing architecture in which a Cisco Unified Communications Manager cluster, located at a central site, provides telephony services for all sites of an organization. The architecture provides numerous benefits for enterprises, including centralized and simplified management. Table 1 lists the benefits of a centralized call-processing architecture.
Table 1. Benefits of Centralized Call-Processing Architecture
|
Centralized Call Processing
|
Features and Benefits
|
|
Delivery of full feature set to remote locations, next-generation call centers, unified messaging services, embedded directory services, and mobility
|
Improved productivity
|
|
Centralized configuration and management
|
Reduced operating expenses
|
|
Simplified maintenance and troubleshooting
|
Reduced operating expenses
|
|
Converged voice and data network
|
Reduced operating expenses
|
|
Reduced installation cost (shared Cisco Unified Communications Manager resource)
|
Reduced initial expense
|
However, a centralized call-processing architecture must include a strategy for survivability of telephony service at the remote locations (that is, at branch offices and the homes of teleworkers) when access to the centralized call-processing services is interrupted because of a WAN outage or other factors. Call-processing redundancy in the remote location is particularly critical during an emergency (which may be the actual cause of the WAN outage).
Components of Centralized Call-Processing Architecture
The Cisco Unified Communications Solution uses Cisco Unified Communications Manager in combination with Cisco Unified SRST, which is embedded in the Cisco IOS Software, to help provide high-availability IP telephony to remote locations. When access to Cisco Unified Communications Manager from a remote location is impeded, for example, as a result of a WAN link failure, Cisco Unified SRST provides telephony backup services to help ensure that the remote location has continuous telephony service over the Cisco network infrastructure deployed in the remote location. The enhanced reliability provided by Cisco Unified SRST makes Cisco Unified Communications a cost-effective solution to help ensure telephony operation for all users in an organization, whether they are located in the headquarters or in a remote location.
Furthermore, in certain environments, the security of telephony communication is a critical requirement. The Cisco Unified Communications Solution supports secure telephony communication between any two phones in the network, whether those phones are in the headquarters facility or at a remote location. Cisco Unified SRST contributes to this secure telephony communication solution by supporting the same secure telephony protocols in a remote location when that location loses communication with the centralized Cisco Unified Communications Manager.
How It Works
Cisco developed Cisco Unified SRST technology for all Cisco IOS Software platforms that support call processing (refer to Table 2 for a complete list of supported platforms). Cisco Unified SRST integrates network intelligence into Cisco IOS Software, which acts as the call-processing engine for IP phones located in the remote locations during a WAN outage (Figure 1).
Figure 1. Centralized Cisco Unified Communications Manager Deployment with Remote Site Experiencing a WAN Failure and Cisco Integrated Services Router Using Cisco Unified SRST
Cisco Unified SRST functions in the remote location router to automatically detect a failure in the network and initiate a process to autoconfigure the router, providing call-processing backup redundancy for the IP phones in that location and helping ensure that the telephony capabilities stay operational. Upon restoration of WAN connectivity, the system intelligently and automatically shifts call processing back to the primary Cisco Unified Communications Manager cluster. The Cisco Unified SRST configuration needs to be completed only once, during the initial installation, simplifying deployment, administration, and maintenance. No IT staff is required at the remote sites to manage the Cisco Unified SRST application.
Cisco routers running Cisco Unified SRST also offer a secure voice mode with Cisco Unified SRST 3.3 and later. If you deploy secure voice with Cisco Unified Communications Manager at your central site, secure Cisco Unified SRST allows you to keep calls secure during Cisco Unified SRST mode with Transport Layer Security (TLS) and Secure Real-Time Transport Protocol (SRTP) for signaling and media encryption, respectively. When the WAN link or Cisco Unified Communications Manager service is restored, Cisco Unified Communications Manager resumes secure call-handling capabilities.
Cisco Unified SRST 3.4 and later versions support Session Initiation Protocol (SIP) for Cisco Unified IP Phones, providing basic telephony functions when the network SIP proxy or Cisco Unified Communications Manager is no longer available. The Cisco Unified SRST router with SIP enabled provides SIP registrar services during the outage and supports a back-to-back user agent, allowing for supplementary features such as call transfer and forwarding. Cisco Unified IP Phones register using SIP to the Cisco Unified SRST-enabled router when the WAN link is out of service.
Cisco Unified SRST offers fault monitoring using Simple Network Management Protocol (SNMP) with the SRST MIB, which allows you to remotely monitor the Cisco Unified SRST site using existing SNMP tools or CiscoWorks. The Cisco SRST MIB provides the network operations center details about Cisco Unified SRST activity, including duration of Cisco Unified SRST use, IP phones registered or registration failure, and calls processed during SRST mode. A backup WAN link connection is required to receive Cisco SRST MIB data at the central site in SRST mode.
Tables 2 and 3 list the platforms that support Cisco Unified SRST.
Table 2. Cisco Unified SRST ISR Platform Density and Feature License Part Numbers
|
Platform
|
Number of Phones Supported*
|
Part Number
|
Part Number (Spare)
|
|
Cisco 800 Series Integrated Services SRST Router
|
Up to 4 phones
|
Included
|
-
|
|
Cisco 1861 Integrated Services Router
|
Up to 15 phones
|
Included
|
-
|
|
Cisco 2801 Integrated Services Router
|
Up to 25 phones
|
FL-SRST-25
|
FL-SRST-25=
|
|
Cisco 2811 Integrated Services Router
|
Up to 35 phones
|
FL-SRST-35
|
FL-SRST-35=
|
|
Cisco 2821 Integrated Services Router
|
Up to 50 phones
|
FL-SRST-50
|
FL-SRST-50=
|
|
Cisco 2851 Integrated Services Router
|
Up to 100 phones
|
FL-SRST-100
|
FL-SRST-100=
|
|
Cisco 3825 Integrated Services Router
|
Up to 350 phones
|
-**
|
-**
|
|
Cisco 3845 Integrated Services Router
|
Up to 730 phones
|
-**
|
-**
|
* The numbers of phones supported by SRST have been changed to multiples of 5 starting with Cisco IOS Software Release 12.4(15)T3.
** There are no corresponding part numbers, but you can purchase multiple parts to reach the desired phone count.
Table 3. Cisco Unified SRST on Cisco Integrated Services Routers Generation 2 (ISR G2) Platform Density and Feature License Part Numbers
|
Platform
|
Number of Phones Supported
|
Cisco IOS Technology Package License
|
Cisco IOS Feature License* (CME-SRST License)
|
Cisco IOS Feature License* (CME-SRST User License**)
|
|
Cisco 2901 Integrated Services Router G2
|
35
|
SL-29-UC-K9
|
FL-SRST
|
FL-CME-SRST-5
FL-CME-SRST-25
|
|
Cisco 2911 Integrated Services Router G2
|
50
|
SL-29-UC-K9
|
FL-SRST
|
FL-CME-SRST-5
FL-CME-SRST-25
|
|
Cisco 2921 Integrated Services Router G2
|
100
|
SL-29-UC-K9
|
FL-SRST
|
FL-CME-SRST-5
FL-CME-SRST-25
FL-CME-SRST-100
|
|
Cisco 2951 Integrated Services Router G2
|
250
|
SL-29-UC-K9
|
FL-SRST
|
FL-CME-SRST-5
FL-CME-SRST-25
FL-CME-SRST-100
|
|
Cisco 3925 Integrated Services Router G2
|
730
|
SL-39-UC-K9
|
FL-SRST
|
FL-CME-SRST-5
FL-CME-SRST-25
FL-CME-SRST-100
|
|
Cisco 3945 Integrated Services Router G2
|
1200
|
SL-39-UC-K9
|
FL-SRST
|
FL-CME-SRST-5
FL-CME-SRST-25
FL-CME-SRST-100
|
*In order to enable the SRST feature license, select Cisco IOS Technology License UC package.
** CME-SRST User License counts can be a summary of three part numbers: FL-CME-SRST-5, FL-CME-SRST-25, and FL-CME-SRST-100, depending on the platform capacity.
Cisco Unified SRST Platform Information
Cisco Unified SRST supports from 4 to 730 phones on Cisco 2800 and 3800 Series ISR platforms. On Cisco Integrated Services Routers Generation 2 (ISR G2) platforms (Cisco 2900 and 3900 Series ISR G2 platforms), SRST supports from 35 to 1200 phones. Details about currently supported platforms and the number of phones per platform are provided in the Cisco Unified SRST specifications sheet for each version, which is available online at:
https://www.cisco.com/en/US/products/sw/voicesw/ps2169/products_device_support_tables_list.html.
Cisco offers integrated services router bundles with Cisco Unified SRST at a discount when compared to separate purchase of bundle components. These bundles are listed in Tables 4 (for Cisco ISR platforms) and 5 (for Cisco ISR G2 platforms).
Table 4. Cisco Unified SRST Bundles for Cisco ISR platforms
|
Bundle Part Number
|
Includes
|
|
CISCO3845-SRST/K9
|
Cisco 3845 voice bundle with packet voice digital signal processor (DSP) module (PVDM2-64), Cisco Unified SRST license for 250 phones, and Cisco IOS SP Services feature set
|
|
CISCO3825-SRST/K9
|
Cisco 3825 voice bundle with packet voice DSP module (PVDM2-64), Cisco Unified SRST license for 175 phones, and Cisco IOS Software SP Services feature set
|
|
CISCO2851-SRST/K9
|
Cisco 2851 voice bundle with packet voice DSP module (PVDM2-48), Cisco Unified SRST license for 100 phones, and Cisco IOS Software SP Services feature set
|
|
CISCO2821-SRST/K9
|
Cisco 2821 voice bundle with packet voice DSP module (PVDM2-32), Cisco Unified SRST license for 50 phones, and Cisco IOS Software SP Services feature set
|
|
CISCO2811-SRST/K9
|
Cisco 2811 voice bundle with packet voice DSP module (PVDM2-16), Cisco Unified SRST license for 35 phones, and Cisco IOS Software SP Services feature set
|
|
CISCO2801-SRST/K9
|
Cisco 2801 voice bundle with packet voice DSP module (PVDM2-8), Cisco Unified SRST license for 25 users, and Cisco IOS Software SP Services feature set
|
|
C1861-SRST-C-F/K9
|
Cisco 1861 voice bundle with 8 Power over Ethernet (PoE) ports, 4 foreign-exchange-station (FXS) ports, 4 foreign-exchange-office (FXO) ports, Cisco Unity Express, Cisco Unified SRST license for 8 users, and Cisco IOS Software SP Services feature set
|
|
C1861-SRST-C-B/K9
|
Cisco 1861 voice bundle with 8 PoE ports, 4 FXS ports, 2 Basic Rate Interface (BRI) ports, Cisco Unity Express, Cisco Unified SRST license for 8 users, and Cisco IOS Software SP Services feature set
|
|
C1861-SRST-F/K9,
|
Cisco 1861 voice bundle with 8 PoE ports, 4 FXS ports, 4 FXO ports, Cisco Unified SRST license for 8 users, and Cisco IOS Software SP Services feature set
|
|
C1861-SRST-B/K9
|
Cisco 1861 voice bundle with 8 PoE ports, 4 FXS ports, 2 BRI ports, Cisco Unified SRST license for 8 users, and Cisco IOS Software SP Services feature set
|
|
C881SRST-K9
|
Cisco 881 SRST Ethernet Security Router with 4 FXS ports, 1 FXO port, Cisco Unified SRST license for 4 users, and Cisco IOS Software Advanced IP Services feature set
|
|
C881SRSTW-GN-A-K9
|
Cisco 881 SRST Ethernet Security Router with 4 FXS ports, 1 FXO port, Cisco Unified SRST license for 4 users, Cisco IOS Software Advanced IP Services feature set, and wireless IEEE 802.11n FCC compliance
|
|
C881SRSTW-GN-E-K9
|
Cisco 881 SRST Ethernet Security Router with 4 FXS ports, 1 FXO port, Cisco Unified SRST license for 4 users, Cisco IOS Software Advanced IP Services feature set, and wireless IEEE 802.11n ETSI compliance
|
|
C888SRST-K9
|
Cisco 888 SRST G.SHDSL Router with 4 FXS ports, 1 BRI port, Cisco Unified SRST license for 4 users, and Cisco IOS Software Advanced IP Services feature set
|
|
C888SRSTW-GN-A-K9
|
Cisco 888 SRST G.SHDSL Router with 4 FXS ports, 1 BRI port, Cisco Unified SRST license for 4 users, Cisco IOS Software Advanced IP Services feature set, and IEEE 802.11n FCC compliance
|
|
C888SRSTW-GN-E-K9
|
Cisco 888 SRST G.SHDSL Router with 4 FXS ports, 1 BRI port, Cisco Unified SRST license for 4 users, Cisco IOS Software Advanced IP Services feature set, and IEEE 802.11n ETSI compliance
|
Table 5. Cisco Unified SRST Bundles for Cisco ISR G2 platforms
|
Bundle Part Number
|
Includes
|
|
C2901-CME-SRST/K9
|
Cisco 2901 voice bundle with packet voice DSP module (PVDM3-16), Cisco Unified SRST license for 25 phones, and Cisco IOS UC technology license package
|
|
C2911-CME-SRST/K9
|
Cisco 2911 voice bundle with packet voice DSP module (PVDM3-32), Cisco Unified SRST license for 25 phones, and Cisco IOS UC technology license package
|
|
C2921-CME-SRST/K9
|
Cisco 2921 voice bundle with packet voice DSP module (PVDM3-32), Cisco Unified SRST license for 25 phones, and Cisco IOS UC technology license package
|
|
C2951-CME-SRST/K9
|
Cisco 2951 voice bundle with packet voice DSP module (PVDM3-32), Cisco Unified SRST license for 25 phones, and Cisco IOS UC technology license package
|
|
C3925-CME-SRST/K9
|
Cisco 3925 voice bundle with packet voice DSP module (PVDM3-64), Cisco Unified SRST license for 25 phones, and Cisco IOS UC technology license package
|
|
C3945-CME-SRST/K9
|
Cisco 3945 voice bundle with packet voice DSP module (PVDM3-64), Cisco Unified SRST license for 25 phones, and Cisco IOS UC technology license package
|
Cisco Unified IP Phone Support
Cisco Unified SRST is supported with Cisco CallManager Version 3.01 and later. Cisco Unified SRST is not dependent on Cisco Unified Communications Manager versions but on IP phone loads. (Beginning with Version 4.3, Cisco Unified CallManager is called Cisco Unified Communications Manager.)
Table 6 lists the Cisco Unified IP Phones supported by Cisco Unified SRST with Skinny Client Control Protocol (SCCP) phone loads.
Table 6. Cisco Unified IP Phone Support Using SCCP
|
Phone
|
Cisco Unified SRST 3.3
|
Cisco Unified SRST 3.4
|
Cisco Unified SRST 4.0
|
Cisco Unified SRST 4.1
|
Cisco Unified SRST 4.2
|
Cisco Unified SRST 4.3
|
Cisco Unified SRST 7.0
|
Cisco Unified SRST 7.1
|
|
Cisco Unified IP Conference Station 7937G
|
-
|
-
|
-
|
-
|
-
|
X
|
X
|
X
|
|
Cisco Unified IP Phone 7975G, 7965G, 7962G, 7945G, and 7942G models
|
-
|
-
|
-
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Phone 7970G and 7971G-GE models
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Phone 7960G and 7940G models
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Phone 7961G, 7941G, 7961G-GE, and 7941G-GE models
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Phone 7931G
|
-
|
-
|
-
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Conference Station 7935
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Conference Station 7936
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Phone 7912G
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Phone 7911G
|
-
|
-
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Phone 7905G
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Phone 7906G
|
-
|
-
|
-
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Phone 7902G
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified Wireless IP Phone 7920
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified Wireless IP Phone 7921G
|
-
|
-
|
-
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified Wireless IP Phone 7925G
|
_
|
_
|
_
|
_
|
_
|
X
|
X
|
X
|
|
Cisco Unified IP Phone 7985G
|
-
|
-
|
Audio calls only
|
Audio calls only
|
Audio and video calls
|
Audio and video calls
|
Audio and video calls
|
X
|
|
Cisco Unified IP Phone Expansion Module 7914
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Phone Expansion Module 7915 and 7916 modules
|
_
|
_
|
_
|
X*
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Phone 6921, 6941, and 6961 models
|
_
|
_
|
_
|
_
|
_
|
_
|
_
|
_
|
|
Cisco VG248 48-Port Analog Voice Gateway
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco ATA 180 Series Analog Telephone Adaptors
|
-
|
-
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco IP Communicator
|
-
|
-
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified Video Advantage
|
-
|
-
|
X
|
X
|
X
|
X
|
X
|
X
|
*The support started from Cisco IOS Software Release 12.4(15)T8.
Table 7 lists the Cisco Unified IP Phones supported by Cisco Unified SRST with SIP phone loads.
Table 7. Cisco Unified IP Phone Support Using SIP
|
Phone
|
Cisco Unified SRST 4.0
|
Cisco Unified SRST 4.1
|
Cisco Unified SRST 4.2
|
Cisco Unified SRST 4.3
|
Cisco Unified SRST 7.0
|
Cisco Unified SRST 7.1
|
|
Cisco Unified IP Phone 8961, 9951, and 9971 models
|
_
|
_
|
_
|
_
|
_
|
X
|
|
Cisco Unified IP Phone 7975G, 7965G, 7962G, 7945G, and 7942G models
|
-
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Phone 7970G and 7971G-GE models
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Phone 7960G and 7940G models
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Phone 7961G, 7941G, 7961G-GE, and 7941G-GE models
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Conference Station 7935
|
-
|
-
|
-
|
-
|
-
|
-
|
|
Cisco Unified IP Conference Station 7936
|
-
|
-
|
-
|
-
|
-
|
-
|
|
Cisco Unified IP Phone 7912G
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Phone 7906G
|
-
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Phone 7911G
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Phone 7905G
|
X
|
X
|
X
|
X
|
X
|
X
|
|
Cisco Unified IP Phone 7902G
|
-
|
-
|
-
|
-
|
-
|
-
|
|
Cisco Unified Wireless IP Phone 7920 and 7921G models
|
-
|
-
|
-
|
-
|
-
|
-
|
|
Cisco Unified Wireless IP Phone 7925
|
_
|
_
|
_
|
_
|
_
|
_
|
|
Cisco Unified IP Phone Expansion Module 7914, 7915, and 7916 modules
|
-
|
-
|
-
|
-
|
-
|
-
|
|
Cisco Unified IP Phone 6921, 6941, and 6961 models
|
_
|
_
|
_
|
_
|
_
|
_
|
|
Cisco ATA 180 Series Analog Telephone Adaptors
|
-
|
-
|
-
|
-
|
-
|
-
|
Cisco IOS Software Image Support
Table 8 summarizes the correlation between the Cisco Unified SRST version and Cisco IOS Software.
Secure Cisco Unified SRST is available with Cisco Unified SRST 3.3 and later for Cisco Unified IP Phones using SCCP; it requires Cisco Unified CallManager 4.1(2) and later. (Beginning with Version 4.3, Cisco Unified CallManager is called Cisco Unified Communications Manager.)
Cisco Unified SRST for SIP phones is supported by Cisco Unified SRST 3.4 and later and only with Cisco Unified IP Phones.
For the latest Cisco IOS Software release and features, consult the Feature Navigator at: https://www.cisco.com/go/fn.
Table 8. Cisco IOS Software Release
|
Cisco Unified SRST Version
|
Cisco IOS Software Release(s)
|
|
Cisco Unified SRST 2.0
|
12.2(13)T
|
|
Cisco Unified SRST 2.1
|
12.2(15)T and 12.3 Mainline
|
|
Cisco Unified SRST 3.0
|
12.3(4)T
|
|
Cisco Unified SRST 3.1
|
12.3(8)T
|
|
Cisco Unified SRST 3.2
|
12.3(11)T
|
|
Cisco Unified SRST 3.3 plus Secure SRST
|
12.3(14)T and 12.4 Mainline
|
|
Cisco Unified SRST 3.4
|
12.4(4)T
|
|
Cisco Unified SRST 4.0
|
12.4(9)T
|
|
Cisco Unified SRST 4.1
|
12.4(14)T
|
|
Cisco Unified SRST 4.2
|
12.4(11)XW2
|
|
Cisco Unified SRST 4.3
|
12.4(11)XZ
|
|
Cisco Unified SRST 7.0
|
12.4(20)T
|
|
Cisco Unified SRST 7.1 (on Cisco ISR)
|
12.4(22)YB and 12.4(24)T
|
|
Cisco Unified SRST 7.1 (on Cisco ISR G2)
|
15.0(1)M
|
Supported Features
Cisco Unified SRST provides robust support for many IP phone features through the duration of a WAN failure, a feature that is not available from other traditional telephony solutions. Table 9 lists the features supported during failure.
Table 9. Cisco Unified SRST Features Supported During WAN Failure
|
Cisco Unified SRST Version
|
Feature Set
|
|
Cisco Unified SRST 2.0
|
Support for IP and analog phones
Rehoming of IP phones upon failure to branch-office router for call processing
Maintenance of local extension-to-extension calls upon failure*
Maintenance of extension-to-public switched telephone network (PSTN) calls upon failure
Up to 6 lines per phone
Call hold and pick up
Speed and last-number redial
Up to 24 line appearances per system
Primary line support
Maintenance of existing calls upon recovery
Analog FXO and FXS
Calling-party name
Caller ID and asynchronous-network-interface (ANI) support
WAN link support: Frame Relay, ATM, Multilink Point-to-Point Protocol (MLPPP), serial, ATM Adaption Layer 2 (AAL2), and DSL
Class of restriction
Music on hold (MoH), tone on hold, and music and tone on transfer (MoH for endpoint PSTN only)
Distinctive ringing
Direct inward dialing (DID) and direct outward dialing (DOD)
PSTN T1 and E1 channel-associated-signaling (CAS) trunks support
ISDN BRI and Primary Rate Interface (PRI) support
Call-detail recording and RADIUS server
Interworking with Cisco Gatekeeper
Transfer to voicemail pilot number using PSTN
Alias lists for unregistered phones
Translation rules support
Tool Command Language (TCL)-based simple Automated Attendant and interactive voice response (IVR) on local gateways
Transfer across H.323 network of Cisco endpoints
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Cisco Unified SRST 2.1
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Cisco Unified CallManager or Unified Communications Manager phone language support
Global-call-forwarding enhancement
In-band dual tone multifrequency (DTMF) voicemail integration
Enhanced dial-plan pattern
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Cisco Unified SRST 3.0
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E1-R2 signaling support
Secondary dial tone
Dual-line appearance per button
Three-party G711 temporary conferencing
Call transfer with consult
MoH multicast from flash .au file in Cisco Unified CallManager or Unified Communications Manager mode
Support for Cisco Unified IP Phone 7905G
European date formats
Enhanced dialplan-pattern command
Increased directory-number maximums
Additional language options for IP phone
Configurable system message
Improved debugging for phones
Symmetric SIP gateway-to-gateway DTMF relay
Ringing timeout for phones
Cisco SIP phone support of basic calls only
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Cisco Unified SRST 3.1
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Support for Cisco Unified Wireless IP Phone 7920
Support for Cisco Unified IP Conference Station 7935 or Cisco Unified IP Conference Station 7936
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Cisco Unified SRST 3.2
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Enhancement to the alias command
Enhancement to the cor command
Enhancement to the pickup command
Enhancement to the user-locale command
Increased number of phones supported on the Cisco 3745 Multiservice Access Router
MoH multicast from live feed in Cisco Unified CallManager or Unified Communications Manager mode
No timeout for call preservation*
RFC 2833 DTMF relay support
Translation profile support
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Cisco Unified SRST 3.3
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Support for Cisco Unified IP Phone 7970G, 7971G-GE, 7961G, 7941G, 7961G-GE, 7941G-GE, and 7911G models
Enhancement to the show ephone command (new Cisco Unified IP Phone model keywords)
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Secure Cisco Unified SRST 3.3 with Cisco Unified CallManager 4.1(2)
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Basic call
Call transfer (consult and blind)
Call forwarding (busy, no answer, and all)
Shared line (SCCP IP phones)
Hold and resume
Hold and pickup
Only secure calls between IP phones or Cisco Unified SRST routers
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Cisco Unified SRST 3.4
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Fault monitoring with SNMP Cisco SRST MIB, including:
Cisco Unified SRST state and duration
Phone registration and failure
Threshold unregistration
Total calls handled in Cisco Unified SRST mode
Cisco Unified SRST support for Cisco Unified IP Phones using SIP loads
SIP proxy and registrar services during Cisco Unified SRST mode plus back-to-back user agent for support of supplementary features
SIP features: Call forwarding, call hold, call transfer (blind and consult), distinctive ringing, time-based call blocking, and SIP phone-load features
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Cisco Unified SRST 4.0
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Support for video calls with Cisco Unified Video Advantage Client
Support for Cisco IP Communicator
Fax pass-though using SCCP with Cisco ATA 180 Series Analog Telephone Adaptors
Call preservation enhancements between IP phones and H.323-controlled voice gateways
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Cisco Unified SRST 4.1
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SIP line-side feature enhancements, including SIP line-side support for Cisco Unified IP Phone 7971G-GE, 7970G, 7941G, 7961G, 7911G, and 7906G models
Dial-plan pattern and Keypad Markup Language (KPML) for faster dialing for SIP phones
MoH for SIP phones
SIP caller ID update, status line update, and SRST status prompt with customizable message
E-911 support
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Cisco Unified SRST 4.2
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Support for Cisco 1861 Integrated Services Router
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Cisco Unified SRST 4.3
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Support for up to 8 active calls per line
Support for Cisco 880 Series routers
CDR enhancement
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Cisco Unified SRST 7.0
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Support for up to 8 active calls per line
Support for Cisco 880 Series routers
CDR enhancement
Cisco IOS Software Release 12.4(20)T
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Cisco Unified SRST 7.1
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Cisco IOS Software Release 12.4(22)YB and 12.4(24)T on Cisco ISR platforms, and 15.0(1)M on Cisco ISR G2 platforms
Increase of phone user scalability on Cisco ISR G2 platforms
International +E.164 registration and basic call dialing
New phone type: Cisco Unified IP Phone 8961, 9951, 9971 model support**
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* Prior to Cisco Unified SRST 3.2, active calls to the PSTN from Cisco Unified SRST IP Phones are maintained for most calls and dropped after approximately 3 minutes. Active calls between users on the same LAN are not affected by WAN failure, and security is maintained for the duration of the call.
Cisco Unified SRST 3.2 and later can preserve existing H.323 calls at the branch-office location if an outage occurs; disable the H.225 keepalive timer by entering the no h225 timeout keepalive command.
** Cisco IP phone 8961, 9951 and 9971 are support on SRST 7.1 with 12.4(24)T or later releases on ISR, and 15.0(1)M release on ISR G2.
Cisco Unified Communications Services and Support
Cisco Unified Communications Services allows you to accelerate cost savings and productivity gains associated with deploying a secure, resilient Cisco Unified Communications Solution. Delivered by Cisco and our certified partners, the Cisco portfolio of services is based on proven methodologies for unifying voice, video, data, and mobile applications on fixed and mobile networks. The unique Cisco lifecycle approach to services can enhance your technology experience and offer true business advantage.
Conclusion
Cisco Unified SRST, in combination with Cisco Unified Communications Manager, offers a simple, cost-effective solution for customers who want the benefits of a centralized call-processing architecture with redundancy at remote branch offices and the homes of teleworkers.
For More Information
For more information about the Cisco Unified Communications Solution, visit the following:
Cisco Unified SRST product and technical information: https://www.cisco.com/go/srst
Cisco Unified Communications products, including Cisco Unified Communications Manager: https://www.cisco.com/go/unifiedcommunications
Networking
