IP Telephony Applications

Types of Deployment

When deploying VoIP technologies, design decisions should take into account the environment in which VoIP is being installed. This section considers three typical environments: the campus LAN, enterprise, and service provider environments.


Campus LAN Environment

Campus LAN environments, an example of which is illustrated in Figure 1-24, have grown tremendously in the past several years due to the demand for networked resources, instant business communication, and VoIP applications.


Components for integrated voice and data campus networks, as discussed previously in the "Packet Telephony Components" section, include the following:

• IP Phone

• Gateway

• MCU

• Application server

When you are designing the campus infrastructure for voice, you must consider the following key issues:

• Robust, fault-tolerant, highly available network design

• Ability to power IP phones

• Redundant power supply for network components

• Ease of IP addressing

• QoS enhancements

Cisco Systems' internal telephone network in San Jose can be considered a campus LAN environment. All desktop phones connect to Ethernet switches and are controlled by Unified CallManager applications. Unified CallManager also controls the gateways and other application servers, such as the Unity server.


Enterprise Environment

Enterprise networks grow and evolve as company services and locations change and expand. Heavy reliance on information processing and universal access to corporate information has driven network designs to provide reliable access, redundancy, reachability, and manageability. These same principles apply to designing corporation-wide voice access in the enterprise environment.

Enterprise networks can be either centralized or distributed call processing environments. In the centralized call processing environment, all of the components of the voice system are controlled by a single centralized call agent, such as Unified CallManager, regardless of their physical location. In a distributed call processing environment, the components of the voice network at each location can act independently.

Figure 1-25 depicts an enterprise centralized call processing environment. Centralized voice networks provide enterprise-wide voice access for calls and voice services controlled from a central site. In this environment, the central site provisions all voice services, such as Cisco Unified CallManager, voice mail, and unified messaging. IP phones at remote sites connect to Cisco Unified CallManager through the IP WAN for call processing.


Components for centralized voice enterprise networks include the following:

• IP phone

• Cisco Unified CallManager cluster (central site only)

• Gateway (all sites)

• MCU (central site only)

• Application server (central site only)

• SRST based on Cisco IOS software (remote sites only)

• IP WAN

Figure 1-26 shows an enterprise distributed call processing environment. Distributed voice networks place voice components at each site and utilize the WAN for intersite calls only.


Components for distributed voice enterprise networks include the following:

• IP phone

• Cisco Unified CallManager cluster

• Gateway

• MCU

• Application server (all sites)

• IP WAN

Modern enterprise network applications include:

• E-business

• E-learning

• Customer care

• Unified messaging

• Videoconferencing

• Voice calls placed from web pages

Service Provider Environment

Service provider environments, an example of which is illustrated in Figure 1-27, add another level of complexity to the voice environment. To be competitive, service providers must provide their business customers with more efficient, less expensive alternatives to the PSTN for voice and data services.


Requirements in the service provider arena include:

• Carrier class performance Voice gateways must provide service that minimizes latency and controls jitter. This level of performance allows customers to maintain voice quality as they migrate from circuit-switched voice to IP-based services.

• Scalability Design must accommodate rapid growth to enable service providers to grow with their customer base. An important aspect of scalability is the automation, configuration, and administration of IP networks and gateways for seamless expansion.

• Comprehensive call records supporting flexible service pricing This is the ability to extract IP session and transaction information from multiple network devices and from all layers of the network, in real time, to produce detailed billing records.

• Signaling System 7 (SS7) interconnect capabilities Tariffs favor interconnection using SS7 signaling because Inter-Machine Trunks (IMTs) are less expensive than ISDN-based facilities. This financial benefit equates to lower monthly expenses, reduced cost of goods that are sold, and higher margins for service providers.