T-1 Slowness (weird slowness issue) please help!

[mbroberson1]

Just curious if any one has seen this or could offer any tips. We have a weird issue with a remote site over a T-1. We have a full point-to-point T-1 with a remote site to the main facility. The T-1 is in no way over utilized, users experience issues with their TCP based application when there is only 4% or so of traffic on the T-1. The site really doesn't ever come close to over utilizing the T-1. Now the weird part is this seems to only happen around the HOT months, but can happen at other times. The equipment and both sides has been checked and there seem to be no environmental issues. There are no errors on either serial of routers at either end. We have had both carriers test their ends of the T-1 and they come back clean and no issues or errors. Any suggestions would be greatly appreciated.

Thanks

[Joseph W. Doherty]

Transient congestion can often be an issue even when the link's average utilization is low. The connection to HOT months is interesting, unless it's the users are HOT too. (Users less tolerant of variable network performance if they're also uncomfortably warm.)

Assuming you're already using WFQ on both ends of the link, to minimize the impact of transient congestion, you might implement SLA tests on the link and see what those stats show. With your overall low link utilization, you might be able to be aggressive in your SLA testing.

[mbroberson1]

Joseph,

Is this what you are referring to?

http://www.cisco.com/en/US/docs/switches/lan/catalyst4500/12.2/44sg/configuration/guide/swipsla.html

[Joseph W. Doherty]

For SLAs, yes.

[mbroberson1]

What's even weireder is that we have several other site also connected by T-1 that access the same server using the same application and they have no issues. Even stranger the T-1 has a backup DSL connection (DMVPN) and when we switch the site for traffic to run over the backup VPN the application works...it's slow, but workable atleast.

Thanks