IP Telephony Components

Key Point

IP telephony components include a robust IP infrastructure, IP phones, a video telephony option, a call-processing engine, applications, and optionally a voice gateway to the PSTN.

Note

More information on Cisco IP telephony is available at http://www.cisco.com/go/ipc.

IP Infrastructure

The IP infrastructure requirements noted in the previous section apply equally to an IP telephony implementation. However, additional items must be considered in this environment because of the other components, including the following:

• The LAN access switches to which IP phones and users' PCs are connected should define two separate virtual LANs (VLANs) each, one for data and one for voice, allowing easier implementation of QoS tools. (VLANs are described in Chapter 2, "Switching Design.") Recall from Chapter 1 that the LAN access switches are interconnected by distribution Layer 3 switches (routers) to provide communication between the workgroups.

• As discussed in Chapter 6, while the network administrator might not want to trust end users to classify and set QoS markings consistent with the organization's policy, the access switches to which they are connected could perform this task.

• Access switches can provide in-line power for the IP phones.

• Consideration should be given to deploying resources over WANs in a distributed design, rather than a centralized design. For example, the CCM application should be distributed when possible so that the voice network remains available if the WAN fails.

IP Phones

Key Point

IP phones digitize and packetize voice. They connect to the network through an Ethernet cable (or through a wireless network), just as a PC does. Many different types of IP phones are available, including both hardware-and software-based.

The following are some of the features available on Cisco IP phones:

• Support for power over Ethernet (PoE), to allow the phone to be powered from the switch to which it is connected (if it supports in-line power) rather than from a power outlet.

• Extensible markup language (XML) support enables access to applications; new features and applications can be added easily. The IP phone contains a micro-browser that enables limited web-browsing capability. Higher-end phones have web-client capabilities, while lower-end phones support text-based XML applications.

• Display and audio features include liquid crystal displays (LCDs), speakerphones, and audible and visual alerts.

• Some models have integrated Ethernet switches, with speeds up to 1 gigabit per second (Gbps).

• Some models support multiple phone lines.

The Cisco portfolio also includes IP Communicator, a software-based IP phone, and a wireless IP phone (which is discussed in Chapter 5, "Wireless LAN Design"). IP Communicator runs on a PC to give users the flexibility of having their IP phone wherever they can access the network.

Cisco also has analog telephone adapters and gateways, allowing analog phones to be connected to a network as though they were IP phones.

Note

More information about Cisco IP phones is available at http://www.cisco.com/en/US/products/hw/phones/ps379/index.html.

Video Telephony

The Cisco VT Advantage product provides Cisco IP phone users with the ability to add video telephony to their phone calls. VT Advantage includes the Cisco VT Advantage software application and a video telephony Universal Serial Bus (USB) camera. With the camera attached to a PC that is colocated with a Cisco IP phone, a user can place and receive video calls on his enterprise IP telephony network using the phone interface.

Call Processing

CCM is a software-based call-processing system that provides enterprise telephony features to an IP network. CCM can be installed on a Cisco Media Convergence Server (MCS) and selected third-party servers. The software also provides a suite of integrated voice applications and utilities, including a software-only manual attendant console and an auto-attendant; a software-only conferencing application; tools for detailed reporting and analysis of calls, adding and deleting users, and configuring phones; and tools for monitoring the CCM components. Multiple CCM servers can be clustered to support up to 30,000 IP phones per cluster; multiple clusters can also be integrated to support up to 1 million users. In networks with up to 2500 phones, two servers are typically deployed: One acts as a publisher (to store the master copy of the configuration database), and the other acts as a subscriber (the device with which phones register).^[4] The subscriber also acts as a backup to the publisher in this scenario.

CCM can be configured to route calls in various ways, using a dial plan. For example, some phones might be allowed to only reach certain destinations within a building and local PSTN calls, while others might have unlimited access. As another example, different paths, such as the PSTN or the WAN, can be selected to reach the same destination, depending on which device is placing the call.

Applications

Voice applications are independent from the call-processing and voice-processing infrastructure, and can reside anywhere within the network. The main applications available from Cisco include the following:

• Cisco IP Contact Center (IPCC) (available in Enterprise and Express editions) For managing customer voice contacts and deploying a distributed contact center infrastructure. For example, IPCC Enterprise provides intelligent contact routing, call treatment, network-to-desktop computer telephony integration (CTI), and multichannel automatic call distributor (ACD) functionality.

• Cisco MeetingPlace A rich-media conferencing solution that integrates voice, video, and web-conferencing capabilities. This application uses existing corporate voice (IP and circuit-switched) and data networks to reduce or eliminate toll charges and conferencing charges.

• Cisco Unity This unified messaging solution delivers e-mail, voice mail, and fax messages to a single inbox so that users can, for example, listen to their e-mail over the telephone, check voice messages from the Internet, and forward faxes to wherever they might be.

• Cisco Personal Assistant A personal productivity application that helps users manage how and where they want to be reached. For example, it provides speech-enabled access to Cisco Unity voice messages, a corporate directory, and personal contact lists, from any telephone. The web-based and telephone user administration interfaces help prevent missed calls or interruptions by allowing calls to be forwarded or screened, in advance or in real time.

Voice Gateway

A voice gateway to the PSTN can be implemented with a variety of devices. For example, the Cisco 3700 Series multiservice access routers communicate directly with CCM and support a range of interfaces and signaling protocols. Voice gateway modules can also be installed in Cisco switches, including the Catalyst 4000 and 6000 Series.

These gateways could communicate with CCM using the H.323 protocol, the Session Initiation Protocol (SIP), or the Media Gateway Control Protocol (MGCP). H.323 is a standard protocol for packet-based audio, video, and data communications over IP. SIP is a standard application layer protocol for multimedia conferencing over IP. MGCP is a standard protocol that allows call agents, such as CCM, to control specific ports on a gateway.