[c-nsp] Latency on ATM IMA circuits

[John Neiberger]

This is a Cisco 8-port IMA card, using four of the ports.

John
--

>>> Peyton Koran <pkoran at uplogix.com> 2/21/05 3:46:39 PM >>>
What are you using for you IMA translation?  Are you using the IMA
cards for
Cisco's, or are you using a real switch, like a Marconi?


----------------------------------------------------------------------------
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Peyton Koran
Uplogix, Inc.
512-857-7026
pkoran at uplogix.com 


> From: "John Neiberger" <John.Neiberger at efirstbank.com>
> Date: Mon, 21 Feb 2005 15:39:04 -0700
> To: <vandusb at attens.com>
> Cc: cisco-nsp at puck.nether.net 
> Subject: Re: [c-nsp] Latency on ATM IMA circuits
> 
> All of these locations are in the same geographic area, not more than
20
> miles apart.
> 
> Round trip times to the first hop on the IMA are averaging 35 ms,
which
> seems awfully high. I would expect less then 10 ms to the first hop,
but
> perhaps my expectations are too high.
> 
> Hmm...interesting. I just took a look at the RTT to the first hop at
my
> T1 sites and it's pretty high there, as well. It's averaging close to
30
> ms just to the first hop! Man, that's slow. It's interesting that a
ping
> to another T1 site is only a few milliseconds longer than to my
first
> hop. I would expect the first hop RTT to be considerably lower than
that
> of other sites.
> 
> I guess I need to do some research to figure out how high my
> expectations should actually be.
> 
> Thanks,
> John
> --
> 
>>>> Brent Van Dussen <vandusb at attens.com> 2/21/05 3:32:56 PM >>>
> Geographic differences wouldn't account for that added latency would
> it?  What do pings look like to the first hop of your IMA link?
> 
> -Brent
> 
> 
> At 02:26 PM 2/21/2005, you wrote:
>> I'm beginning to migrate our sites to an MPLS-based VPN product.
All
> but
>> one of our sites has a full T-1, but one site has an ATM IMA
circuit
>> composed of four T1s. When I ping from a T1 site to another T1 site
I
>> see an average round-trip time of about 32 ms. However, when I ping
> from
>> or to the site with the IMA, the round-trip time ranges between 65
> and
>> 80 ms. That's a pretty big jump! And one I wouldn't have expected.
>> 
>> Is this type of added latency to be expected with IMA circuits?
This
> is
>> the first one I've ever used before so I have no frame of
reference.
> I'm
>> wondering if the multiplexing functions add some latency that isn't
>> present on our other circuits.
>> 
>> Any thoughts?
>> 
>> Thanks!
>> John
>> --
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