Last revised on: February 13, 2008
The Cisco Unified Communications System delivers fully integrated communications by enabling data, voice, and video to be transmitted over a single network infrastructure using standards-based Internet Protocol (IP). Leveraging the framework provided by Cisco IP hardware and software products, the Cisco Unified Communications System delivers unparalleled performance and capabilities to address current and emerging communications needs in the enterprise environment. The Cisco Unified Communications family of products is designed to optimize feature functionality, reduce configuration and maintenance requirements, and provide interoperability with a wide variety of other applications. The Cisco Unified Communications System provides this capability while maintaining a high level of availability, quality of service (QoS), and security for your network.
The Cisco Unified Communications System incorporates and integrates the following major communications technologies:
IP telephony refers to technology that transmits voice communications over a network using IP standards. Cisco Unified Communications includes a wide array of hardware and software products such as call processing agents, IP phones (both wired and wireless), voice messaging systems, video devices, and many special applications.
•Customer contact center
Cisco IP Contact Center products are a combination of strategy and architecture that promote efficient and effective customer communications across a globally capable network by enabling organizations to draw from a broader range of resources to service customers. They include access to a large pool of agents and multiple channels of communication as well as customer self-help tools.
The Cisco Unified Video Advantage products enable real-time video communications and collaboration using the same IP network and call processing agent as Cisco Unified Communications. With Cisco Unified Video Advantage, making a video call is now as easy as dialing a phone number.
Cisco Conference Connection and Cisco Unified MeetingPlace enhance the virtual meeting environment with a integrated set of IP-based tools for voice, video, and web conferencing.
Cisco works with leading-edge companies to provide the broadest selection of innovative third-party IP communications applications and products focused on critical business needs such messaging, customer care, and workforce optimization.
The remainder of this document focuses on system design considerations for the following components of the Cisco Unified Communications System:
•Cisco Unified CallManager
•Cisco Unified Video Advantage
•Cisco Unified MeetingPlace
For information about other aspects of the Cisco Unified Communications System, such as Cisco IP Contact Center, refer to the documentation available at the following locations:
You can also find additional documentation for the Cisco Unified Communications family of products at the following location:
Overview of Cisco Unified Communications
Cisco IP Telephony is the leading converged network IP telephony solution for organizations that want to increase productivity and reduce the costs associated with managing and maintaining separate voice and data networks. The flexibility and sophisticated functionality of the Cisco IP network infrastructure provides the framework that permits rapid deployment of emerging applications such as desktop IP Telephony, unified messaging, video telephony, desktop collaboration, enterprise application integration with IP phone displays, and collaborative IP contact centers. These applications enhance productivity and increase enterprise revenues.
Figure 1-1 illustrates a typical IP Telephony deployment employing the Cisco IP network infrastructure, with Cisco Unified CallManager as the call processing agent.
Figure 1-1 Typical IP Telephony Deployment
The foundation architecture for Cisco IP Telephony includes of the following major components (see Figure 1-1):
•Cisco IP Network Infrastructure
•Quality of Service
•Call Processing Agent
•Conferencing, Messaging, and Collaboration Capabilities
Cisco IP Network Infrastructure
The network infrastructure includes public switched telephone network (PSTN) gateways, analog phone support, and digital signal processor (DSP) farms. The infrastructure can support multiple client types such as hardware phones, software phones, and video devices. The infrastructure also includes the interfaces and features necessary to integrate legacy PBX, voicemail, and directory systems. Typical products used to build the infrastructure include Cisco voice gateways (non-routing, routing, and integrated), Cisco IOS and Catalyst switches, and Cisco routers.
For more information about the IP network infrastructure, see the chapter on Network Infrastructure, page 3-1.
Quality of Service
Voice, as a class of IP network traffic, has strict requirements concerning packet loss, delay, and delay variation (also known as jitter). To meet these requirements for voice traffic, Cisco Unified Communications includes Quality of Service (QoS) features such as traffic classification, queuing, traffic shaping, compressed Real-Time Transport Protocol (cRTP), and Transmission Control Protocol (TCP) header compression.
The QoS components for Cisco Unified Communications are provided through the rich IP traffic management, queueing, and shaping capabilities of the Cisco IP network infrastructure. Key elements of this infrastructure that enable QoS for IP Telephony include:
•Enhanced queuing services
•Link fragmentation and interleaving (LFI)
•Compressed RTP (cRTP)
•Low-latency queuing (LLQ)
•Call admission control (bandwidth allocation)
For more information about QoS, see the various sections on QoS in the chapter on Network Infrastructure, page 3-1.
Call Processing Agent
Cisco Unified CallManager is the core call processing software for Cisco IP Telephony. It builds call processing capabilities on top of the Cisco IP network infrastructure. Cisco Unified CallManager software extends enterprise telephony features and capabilities to packet telephony network devices such as IP phones, media processing devices, voice gateways, and multimedia applications.
You can deploy the call processing capabilities of Cisco Unified CallManager according to one of the following models, depending on the size, geographical distribution, and functional requirements of your enterprise:
•Single-site call processing model
In the single-site model, each site or campus has its own Cisco Unified CallManager or cluster of Cisco Unified CallManagers to perform call processing functions. No voice traffic travels over the IP WAN; instead, external calls or calls to remote sites use the public switched telephone network (PSTN).
•Multisite WAN model with centralized call processing
In the multisite WAN model with centralized call processing, the Cisco Unified CallManager cluster resides at the main (or central) campus, and communication with remote branch offices normally takes place over the IP WAN. If either the central site or the IP WAN is down, the remote sites can continue to have service through a feature called Survivable Remote Site Telephony (SRST). The remote sites can also place calls over the PSTN if the IP WAN is temporarily oversubscribed, and you can interconnect a number of central sites through intercluster trunks.
•Multisite WAN model with distributed call processing
In the multisite WAN model with distributed call processing, each site has its own Cisco Unified CallManager cluster for call processing. Communication between sites normally takes place over the IP WAN, with the PSTN serving as a backup voice path. With this model, you can interconnect any number of sites across the IP WAN.
•Clustering over the IP WAN
You may deploy a single Cisco Unified CallManager cluster across multiple sites that are connected by an IP WAN with QoS features enabled. To provide call processing redundancy, you can deploy backup servers either locally at each site or at a remote site across the WAN. Clustering over the WAN is well suited as a disaster recovery plan for business continuance sites or as a single solution for small or medium sites.
For information on how to apply these deployment models in designing your Cisco IP Telephony network, see IP Telephony Deployment Models, page 2-1.
A communication endpoint is a user instrument such as a desk phone or even a software phone application that runs on a PC. In the IP environment, each phone has an Ethernet connection. IP phones have all the functions you expect from a telephone, as well as more advanced features such as the ability to access World Wide Web sites.
In addition to various models of desktop Cisco Unified IP Phones, IP Telephony endpoints include the following devices:
Cisco IP Communicator and Cisco Unified Personal Communicator are desktop applications that turn your computer into a full-featured IP phone with the added advantages of call tracking, desktop collaboration, and one-click dialing from online directories. Cisco IP Communicator is a software-based application that delivers enhanced telephony support through the PC. It is designed to meet diverse customer needs by serving as a supplemental telephone when traveling, as a telecommuting device, or as a primary desktop telephone. Cisco Unified Personal Communicator integrates a wide variety of communications applications and services into a single desktop computer application to provide quick and easy access to powerful communications tools for voice, video, web conferencing, call management, directories, and presence information.
•Video telephony endpoints
Video telephony capability is now fully integrated with Cisco Unified CallManager. In addition, Cisco Unified Video Advantage brings video telephony functionality to Cisco Unified IP Phones and the Cisco IP Communicator softphone application. The video telephony solution consists of a Windows-based application and USB camera. Users make calls from their Cisco Unified IP Phones using the familiar phone interface, and calls are displayed with video on their PCs without requiring any extra button pushes or mouse clicks.
The Cisco Wireless IP Phone 7920 extends the Cisco family of IP Phones from 10/100 Ethernet to 802.11 wireless LAN (WLAN). The Cisco Wireless IP Phone 7920 provides multiple line appearances with functionality similar to other Cisco Unified IP Phones. In addition, the Cisco Wireless IP Phone 7920 provides enhanced WLAN security and Quality of Service (QoS) for operation in 802.11b networks, and it provides support for XML-based data access and services.
For more information about the various types of endpoints, see IP Telephony Endpoints, page 21-1.
Conferencing, Messaging, and Collaboration Capabilities
Cisco Unified Communications supports the following additional features and applications to provide conferencing, voice messaging, and multi-media collaboration functionality:
Cisco Unified CallManager can interface with a number of other Cisco software and hardware devices to provide complete conferencing capability, including annunciator functions and music on hold. For more information about designing and provisioning conference capabilities in Cisco Unified CallManager, see Media Resources, page 6-1.
Cisco Unified CallManager is capable of integrating with third-party voicemail systems and with Cisco Unity and Unity Connection to provide a full range of voicemail and voice messaging functionality. For more information about integrating third-party voicemail systems with Cisco Unified CallManager, see Third-Party Voicemail Design, page 12-1. For more information about integrating Cisco Unity and Unity Connection with Cisco Unified CallManager, see Cisco Unity, page 13-1.
Video telephony capability is now fully integrated into Cisco Unified CallManager, and there are also new video endpoints available from Cisco and its strategic partners. Video calls and conferences are now just as easy to make as a voice call on an IP phone. For more information about video capability with Cisco Unified CallManager, see IP Video Telephony, page 17-1.
Cisco Unified MeetingPlace is a complete rich-media conferencing application that integrates voice, video, and web conferencing capabilities to make remote meetings as natural and effective as face-to-face meetings. For more information about integrating MeetingPlace with Cisco Unified CallManager, see Cisco Unified MeetingPlace Integration, page 15-1.
Security for a Cisco Unified Communications deployment involves the following main considerations, among others:
•Physical security for restricting physical access to important application servers and network components
•Network access security to prevent hostile logins or attacks
•Security measures for Cisco Unified CallManager, endpoint devices, and various directories and databases
•Mechanisms for defining calling privileges for various classes of users
•Careful network design and management to enhance security
For more information about security for IP Telephony networks, see Voice Security, page 20-1.