We are looking at Tail end Hop Off for least cost routing in our countries of presence.
My question is how do we protect the local sites PSTN trunks from being over subscribed
by the rest of the global sites.
ie. Assess the current capacity and projected impact on the local site’s PSTN Voice trunks.
The last thing i want is Madrid cant make a call out, because the rest of the world is calling
spain, and the Trunks are all utilised !
Any thoughts ?
This is a good question and I am not sure I have a viable answer for you. On one hand, you didn't specify if you were using a centralized call processing solution (e.g. Cisco Unified Communications Manager) or not. From a design standpoint I would recommend considering a model where you have two or more trunks and that only a subset of those trunks are made available for TEHO.
For example, configure two PRIs in New York. Both PRIs are available to the New York site, while one PRI is also used for TEHO. In a CUCM/MGCP model, this can be done with Route Lists/Route Groups. In a H.323 model, you would need to leverage your dial plan components to apply a prefix which clues the H.323 gateway into what you want it to do.
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I think the best solution is to use the "max connections" on the dial
Dial-peer voice 1 pots
Description TEHO National calls to France
Limit 10 calls before failing back to the local route group.
And a bit of proactive monitoring on your trunk busy hours !
You could use locations based CAC in CUCM to limit how many calls could go to that site. So if you have 10 lines in Spain, maybe only allow 5-6 calls to the location at a time. As long as that site is set up as a separate location, you should be able to get that working with or without centralized call processing.