Case Study: Your Turn to Be Trilingual | Voice over IP First-Step

The case study in Chapter 4, "Meet the 'Brain' of the Voice over IP Network," directed you to design an IP telephony solution for the XYZ Company. Your next design decision involves selecting a gateway protocol for the gateways you specified in Chapter 4's case study. These gateways are the routers or switches located at each site that connect out to the local central office (CO) (that is, the PSTN).

Realize that your selection of a gateway protocol might differ from the suggested solution. Just know why you selected the gateway protocol.

Identify your gateway protocol recommendation for the XYZ Company (that is, H.323, MGCP, or SIP), and discuss the rationale for your selection in the following section.

Design Description for XYZ Company:

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Suggested Solution

Chapter 4's suggested solution used a distributed deployment model, with CCM clusters located at XYZ Headquarters and XYZ Remote Office 1. Also, XYZ Remote Office 2 contained a CallManager Express (CME) router, as shown in Figure 5-8.

Figure 5-8. Chapter 4's Suggested Solution

Because the suggested solution only contained Cisco call processing equipment (that is, the design did not use any third-party hardware) and because a distributed deployment model and a CME router were used, the suggested gateway protocol is H.323.

However, if XYZ Company used a centralized deployment model (that is, where all CCM servers reside at XYZ Headquarters), MGCP might be an appropriate gateway protocol choice. MGCP lends itself well to a centralized environment because the MGCP model specifies a centralized call agent with which remote MGCP gateways register. SIP is often used in a CCM environment when connecting a CallManager cluster to a third-party SIP solution.