[c-nsp] Latency on ATM IMA circuits

Peyton Koran pkoran at uplogix.com
Mon Feb 21 17:54:51 EST 2005


Do you mind sharing the config that you have for the Cisco 8 port?
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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 15:50:52 -0700
> To: <pkoran at uplogix.com>
> Cc: <cisco-nsp at puck.nether.net>
> Subject: Re: [c-nsp] Latency on ATM IMA circuits
> 
> 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?
> 
> 
> ----------------------------------------------------------------------------
> ----------------------------------------------------------------------------
> 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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>> 
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> 
> 



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