Cisco Unified Communications

This chapter covers the following topics:

• An introduction to the Cisco Unified Communications strategy (formerly Cisco AVVID) and Cisco Unified CallManager technology
• An understanding of the placement of Cisco Unified CallManager in an IP telephony design
• The interaction between Cisco Unified CallManager and Cisco IP Phones
• Cisco Unified CallManager server platforms

When Microsoft announced their new .NET platform, there was a huge amount of confusion in the industry. Systems administrators did not know if they were to expect a new operating system, programming language, or company direction. The same effect happened when Cisco announced the Architecture for Voice, Video, and Integrated Data (AVVID), now known as Cisco Unified Communications. Network administrators did not understand if this was a new router type, IOS feature set, or marketing campaign. Cisco Unified Communications is not any of these things. Instead, it is a company strategy that provides the foundation for converged networks. The goal of Cisco Unified Communications is to create network equipment that has the capability to handle voice, video, and data traffic within a single network infrastructure.

Figure 1-1 shows the four standard layers of the Cisco Unified Communications voice infrastructure model: the infrastructure layer, which lays the foundation for network components; the call-processing layer, which maintains PBX-like functions; the applications layer, where applications that provide additional network functionality reside; and the client layer, where end-user devices reside.

Figure 1-1. The Cisco Unified Communications Model for Voice Networks

Each of the major areas of the Cisco Unified Communications architecture has a similar model focused around the technologies of voice, video, and data. The key points about the four standard layers of the voice model are as follows:

• Infrastructure layer The infrastructure carries data between all network devices and applications and consists of routers, switches, and voice gateways.
• Call-processing layer Call processing is physically independent of the infrastructure. Thus, a Cisco CallManager in Chicago can provide call control for a bearer channel in Phoenix.
• Applications layer Applications are physically independent of call-processing functions and the physical voice-processing infrastructure; that is, they can reside anywhere within the network.
• Client layer The client layer makes the voice applications available to the user, whether the end device is a Cisco IP Phone, a PC using a Cisco IP Communicator, or a PC delivering converged messaging.

At first, this might seem like just another model to commit to memory; however, understanding Cisco's design of this model allows you to make the most of your voice network. The OSI model creates a standard for communication across networks. In addition, it allows vendors to isolate network functionality and specialize in equipment working at a specific layer. Likewise, one of the huge benefits of using an IP telephony system over a PBX system is the open standards for protocols and equipment. A vendor could specialize and design devices that work only at the client layer of the Cisco Unified Communications voice model. These devices could use an open standard protocol to communicate with the Cisco CallManager at the applications layer.

Note

Because of the flexibility of the Cisco IP telephony network, many organizations have created their own custom applications for the voice network. Cisco has made a Cisco CallManager Software Development Kit (SDK) freely available to aid in the process of creating custom Extensible Markup Language (XML) applications.