Call Routing

CallManager provides an extremely flexible set of tools with which you can control call routing in your enterprise, but this flexibility comes with a price: complexity. This chapter covers routing from the very beginning. It discusses the route pattern, which is CallManager's central routing concept, and it discusses wildcards, which are the basic building blocks of the route pattern. It discusses how CallManager uses route patterns to select destinations based on the digits that users dial.

From this foundation, the chapter delves further into ever more complex topics. This chapter consists of the following sections:

• "The Three Responsibilities of Call Routing" briefly discusses the tasks that CallManager's routing logic must accomplish.
• "The Seven Fundamentals of Call Routing" elaborates on the seven basic featuresroute patterns, route filters, dialing transformations, translation patterns, route lists, calling search spaces, and partitionsthat CallManager uses to solve call routing problems.
• "Route Patterns and Route Filters" talks about the route pattern, CallManager's fundamental call routing concept, by which you can assign addresses to devices in your network.
• "Dialing Transformations" discusses the mechanisms by which you can alter the calling and called numbers as CallManager routes them during calls.
• "Translation Patterns" defines a method by which you can assign aliases to other route patterns. This method is often called on to resolve thorny call routing problems.
• "Call Hunting Constructs" describes two technologies that allow you to configure CallManager to intelligently route a callroute lists and hunt lists. Route lists allow you to organize your gateways into ordered lists so that you can ensure both that your gateways are fully utilized and that you use them in the most cost-efficient manner. Hunt lists allow you to serially or simultaneously offer calls to a group of related phones.
• "Calling Search Spaces and Partitions" defines a method by which you can customize routing on a device-by-device basis to accomplish complex tasks, such as routing calls by the type or the geographic location of the calling user. Partitions can also be associated with time schedules to provide time-of-day routing.
• "Case Studies" provides some extensive examples by which you can see how all the call routing concepts work together to solve complex problems.
• "Miscellaneous Solutions" provides specific solutions for call routing problems that administrators are commonly called on to solve. The solutions in this section often did not fit nicely in other sections of this chapter.
• "International Numbering Plans" covers how CallManager knows how to route calls for which you have selected a numbering plan. This section also describes how you can download additional country-specific numbering plans.
• "Troubleshooting" covers some common problems that administrators encounter when configuring their enterprise dial plans.

Figure 2-1 shows the block structure of CallManager. The shaded parts of Figure 2-1 are covered in this chapter.

Figure 2-1. CallManager Block Structure Diagram

This chapter is sprinkled with numerous examples throughout. These examples might be difficult to wade through, but they provide solutions to many common problems. By fully understanding how the examples work, you will be able both to improve on them and to discover solutions to problems that this chapter does not fully address.