Implementing Tail-End Hop-Off cisco ccie training center in delhi gurgaon

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When you implement TEHO, PSTN breakout occurs at the gateway that is closest to the
dialed PSTN destination. You do this by creating a route pattern for each destination area
that can be reached at different costs. These route patterns are required once per site and
have to be put into different partitions by identifying the site that should use a particular
route pattern.
As illustrated in Figure 4-10, each route pattern points to a route list and route group or
groups and has an ordered list of PSTN gateways that includes the cheapest gateway first,
the local gateway next, and optionally a third gateway for additional backup. IP Phones
have a CSS that selects the route patterns built for their site. This way, per originating site
and per destination number, a different first-choice gateway can be selected, and the local
gateway is the second option.
Figure 4-10 Implementing Tail-End Hop-Off (TEHO)
Chapter 4: Implementing a Dial Plan for Multisite Deployments
NOTE You also must consider call admission control (CAC) when implementing
TEHO. When the primary (TEHO) path is not admitted as a result of reaching the CAC
call limit, calls should be routed through the local gateway. More information about CAC
is provided in Chapter 9, "Implementing Call Admission Control."
Summary
The following key points were discussed in this chapter:
• Multisite dial plans should support selective PSTN breakout with backup gateways,
PSTN backup for on-net calls, TEHO, and intersite calls using access codes and site
codes.
• If you add an access code and site code to directory numbers at each site, directory
numbers do not have to be globally unique anymore.
Considerations When Using TEHO
When using backup TEHO, consider the following potential issues:
• Consider what number you want to use for the ANI of the outgoing call. The factors
you must consider are the same that have been discussed for PSTN backup.
• With TEHO, calls are routed based on the source (physical location) and based on the
dialed number. This can require a huge number of route patterns, resulting in complex
dial plans. Such dial plans are difficult to maintain and troubleshoot.
• CUCM has no automated technique to enter all the remote route patterns for TEHO.
They all must be entered manually based on a specific study of area codes in different
geographic regions and their associated toll charges.
• The primary purpose of TEHO is to reduce operating costs by increasing WAN
utilization and decreasing PSTN toll charges. For example, PSTN long-distance toll
charges within the contiguous 48 United States have dropped considerably in the last
few decades, hence reducing the TEHO cost savings. However, TEHO cost savings for
international calls can be considerable.
CAUTION The use of TEHO might not be permitted in your country or by your
provider. There also can be issues with emergency calls. Therefore, ensure that your
planned deployment complies with legal requirements.