Sometimes it is not feasible or cost-effective to have a full-blown Cisco Unified Communications Manager (CUCM) solution for remote sites or smaller office locations. To integrate these remote sites, small to medium-size businesses (SMBs), or small office/home office (SOHO) with enterprise networks, Cisco IOS Unified Communications (UC) gateways offers a wide variety of functionality, ranging from call control features, survivability features, and redundancy options for remote site infrastructure.
This chapter covers the fundamentals of Cisco remote site telephony options and survivable remote site telephony (SRST) and its variations.
Upon completing this chapter, you will be able to meet these objectives:
- Describe remote site telephony options
- Describe Cisco SRST
- Describe Cisco E-SRST
- Describe Cisco SIP SRST
- Describe MGCP fallback
- Describe CFUR
Cisco Unified Communications Manager Express
Cisco Unified Communications Manager Express (Cisco Unified CME) is the express version of Cisco’s enterprise call control solution. A Cisco Unified CME-based solution is ideal for small businesses or remote sites in an enterprise environment. Figure 5-1 illustrates a Cisco Unified CME-based telephony solution connecting two SOHO/SMB sites.
Figure 5-1 Cisco Unified CME-Based Telephony Solution
A Cisco Unified CME is capable of the following:
- Supporting Skinny Client Control Protocol (SCCP) and Session Initiation Protocol (SIP) phones
- Terminating public switched telephone network (PSTN) (traditional E1/T1) or SIP trunks
- Tight integration with CUCM and Unity Connection
- Integrating with Cisco Unity Express
- Offering features like Call-Park, Ad-Hoc, or Meet-Me conferences, and Transcoding
- Offering an interactive self-service solution: Basic Automatic Call Distribution (B-ACD)
Hence, Cisco Unified CME can successfully service a site ranging from 25 to 1500 users (or even more depending on the model of router and licenses chosen). As discussed later in this chapter, Cisco Unified CME supports both SIP and SCCP endpoints and enterprise-grade features during regular and survivability mode, including video endpoints, conferencing, music on hold (MOH), paging, call-park, and so on.