4 Realms and Nested Realms

This chapter explains how to configure realms and nested realms, and specialized media-related features.

A realm is a logical definition of a network or groups of networks made up in part by devices that provide real-time communication sessions comprised of signaling messages and possibly media flows. These network devices might be call agents, registrars, SIP proxies, IP PBXs, etc., that are statically defined by IPv4 addresses. These network devices might also be IPv4 endpoints: SIP phones, IADs, MAs, media gateways, etc., that are defined by an IPv4 and IPv6 address prefix.

Realms support bandwidth-based call admission control and QoS marking for media. They are the basis for defining egress and ingress traffic to the —which supports the ’s topology hiding capabilities.

This chapter also explains how to configure media ports (steering pools). A steering pool exists within a realm and contains a range of ports that have a common address (for example, a target IPv4/IPv6 address). The range of ports contained in the steering pool are used to steer media flows from one realm, through the , to another.