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c097687 Tue, 12/03/2002 - 07:30
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We currently have 4 PPP T1's in service between Chicago and Denver.

The T1's connect 2 routers on each side, 2 from CHIA to DENA, 1 from CHIA to DENB and 1 from CHIB to DENB.

A proposal has been made to replace this scenario with 1 router in each city, and installing 4 port T1 ATM network modules with IMA in each router. The idea is to build one 6mb pipe and the theory is better throughput.

Has anyone done this? Was there a significant service improvement?

m.venkatesan Tue, 12/03/2002 - 08:43
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We have implemented it in our network and we love it. U can have a single pipe and have better perfomance, not to worry about load balancing, etc.


pschneck Tue, 12/03/2002 - 12:25
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I have 7 sites running IMA using 3662 routers and 8 port IMA Network Modules aggregating back to our TX location via a DS3. A couple of things to keep in mind:

1.) You will lose some T1capacity due to ATM IMA overhead.

2.) Ask your provider what bursting percentage they will allow above the PVC size you have chosen.

IMAs do bounce in and out of the IMA group but, matching your differential delay with your providers and keeping your carriers accountable should solve the problem.

bacarpenter Tue, 12/03/2002 - 10:38
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We had tried this once and due to links falling out of the group and increased latency and response time, pulled all IMA out of our network. We switched to hardware IMUX instead, which was much better.

demiller Thu, 12/19/2002 - 06:01
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There was a site in our network that had 3 T1s supporting 3 separate business units. IMA was implemented on a 3640 with no problems and increased throughput to each business unit. Let me know if you need configuration information.


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