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RE: Overflow circuit

  • From: Michel Py
  • Date: Fri Mar 26 18:49:54 2004

> Joe wrote:
> I am looking for advice on technique or products that can
> solve the following challenge ...
> Two private line T1's between A and B - one terrestial T1
> with >200 ms RTT, the other T1 is over satellite with ~500
> ms RTT. The circuits are being used for mixed VoIP (70%)
> and data (30%) applications. To achieve optimal voice
> quality, we want to route all VoIP calls over the terrestrial
> T1 until it is "full", then divert all subsequent VoIP calls
> over the satellite T1 (**while existing VoIP calls continue
> to be routed over the terrestial T1).

I have a cheesy solution.....

1. You need a routing protocol that load-balances. I have done it before
with EIGRP, you mileage may vary with others IGPs.

2. Cook a custom metric that will prefer the terrestrial link until full
(a mix of delay and load will likely do).

3. Use policy routing to send anything but voice to the satellite link.
There's a catch here: even if there is no voice, your data is limited to
satellite, which works with your traffic pattern.
Your data is forced to the sat, your voice picks the best path as per
your custom metric.

4. On the satellite link, prioritize voice over data.

5. Fine-tune the variance.


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