the voice numbers appear as additional IP hosts, either as an extension of the existing scheme
or with new IP addresses.
The destination telephone number, or some portion of the number, is mapped to the destination
IP address. When the number is received from the PBX, the router compares the number to
those mapped in the router table. If a match is found, the call is routed to the IP host. After the
connection is established, the corporate intranet connection is transparent to the subscriber.
routing protocol such as EIGRP can take delay into consideration in calculating the best path.
EIGRP can typically converge in less than a second, which allows voice traffic to take
advantage of the self-healing capabilities of IP networks. Advanced features such as policy
routing and access lists make it possible to create highly sophisticated and secure routing
schemes for voice traffic.
gateways to ensure that voice traffic can use the best path through the network. This can include
segments of arbitrary media, such as switched LANs or ATM networks. Some of the most
interesting developments in IP routing are the development of Tag Switching and other IP
switching disciplines. Tag Switching provides a way to extend IP routing, policy, and RSVP
functionality over ATM and other high-speed transports. Another benefit of Tag Switching is its
traffic-engineering capabilities, which are needed for the efficient use of network resources.
Traffic engineering can be used to shift traffic load based on different predicates, such as time
of day.
different classes of service by making the most of each underlying network type. RSVP lets the
participants advise the network of their needs, allowing the network to configure itself to meet
those needs. For example, an application can signal the network about the level of service it
requires. To guarantee this level across the entire flow of the application, RSVP lets the network
reserve resources from end to end, using Frame Relay techniques on Frame Relay networks,
ATM techniques on ATM, and so on. RSVP is beneficial when occasional bandwidth needs to
be reserved for non-voice applications. If priority queuing is enabled for voice at all
checkpoints, RSVP might not add value to your QoS configuration.