Content

| 7.1 |  | Introduction to Cisco AVVID |
| 7.1.6 |  | Cisco AVVID network implementations example |

Figure illustrates a typical deployment of a converged network combining data, voice, and video over a single infrastructure. The network comprises a single or several large headquarters sites, a larger number of branch offices, and individual telecommuter sites. From a telephony point of view, whether a physical handset or a soft-phone application on a PC, the devices are treated as IP endpoints on an IP infrastructure typically serving Ethernet to the end user. Voice calls inside a site traverse the IP local-area network (LAN) until the exit point from the site where, as a first choice, it would cross the IP wide-area network (WAN) backbone to save in public network toll costs. If for some reason this IP WAN is "full" or unavailable, the call would automatically be rerouted across the Public Switched Telephone Network (PSTN). Either way, the path of the call is transparent to the end user. Gateways are used at the edge of each site to provide a path to the PSTN, which is also the primary path for local inbound and outbound calls. This level of integration allows for very simple coordinated dial plans where an entire enterprise can use four- or five-digit dialing, as appropriate, for internal calls.

The technology used in the IP WAN allows for tremendous flexibility in the design of the intranet. Because the IP protocol is the underlying carrier of data, voice, and video, any technology such as Point-to-Point Protocol (PPP), Frame Relay, Asynchronous Transfer Mode (ATM), dark fiber, digital subscriber line (DSL), Synchronous Optical Network (SONET), and wave-division multiplexing (WDM) may be used to construct the network. This allows for maximum flexibility and agility on the part of a network manager to take advantage of new high-speed WAN services from carriers, without making major changes to the converged IP network. However, routers at the edge of the WAN must employ the proper quality of service (QoS) techniques to ensure that voice traffic remains high quality, even in congested conditions. Techniques such as Low-Latency Queuing, Weighted Fair Queuing, and Priority Queuing are examples of necessary technologies in a converged network.

Familiar applications such as voice messaging are also easily integrated into this converged networking environment. Since the voice being carried across the network is encoded in IP, a new breed of IP-enabled unified-messaging solutions allows users to access both voice mail and e-mail from a common server. This can be accomplished with either the e-mail application or through a next-generation IP telephony handset.

While the nirvana of a converged network has widespread appeal to many, the reality is that every corporation already has existing voice and data networks, a scenario that requires finding simple ways to migrate to a converged network.