Slow Data / Lots of Bandwidth

[NcCorduan]

Hello,

I work for a university with two campuses. Between campuses we have two leased T1's, each with about 960K available bandwidth for data. The traffic across the WAN is *incredibly* slow, even though our use of the bandwidth never exceeds 390K on one T1 and only spikes above 480K on the other one during the dead of the night.

I'm on the software / server / PC side of things. The network infrastructure guy I work with (who's on the other campus, so isn't affected by the slow WAN)insists that the very fact that we're not using our max bandwidth means that the slowness is not an issue with the T1's / network hardware.

To my way of thinking, this seems backwards. If our data transmission is so bogged down that our WAN performance is slow, then more of the bandwidth *should* be used.

Is there something you know of which could be damping out data transmission or preventing us from making use of the entire bandwidth?

Thanks!!

 

[workaholic24x7]

what's the application and protocol that you are running on this data link?

 

[craignl]

Firstly I'd identify when this slowness started and what changes were made around that time. You've probably tried that already, so if it has been consistently slow --

Are the clients local and servers on the other side of the WAN? If so checkout the traffic profile. Some "chatty" applications can produce lots of small frames on WAN links which can cause increased latency on routers. The result can be slow responses while using little bandwidth.

 

[thedaver]

I would also hunt down dropped packets/collisions. You may also have a routing issue if you are trying to multiplex/bind the T-1s together (did you say that?). You could potentially have some sort of physical fault in the lines, which a relatively simple loopback testing procedure should help eliminate.

Finally, a SMALL ROUTER, or at least a router with a small amount of memory trying to handle lots of distinct IP:MAC routing decisions at the same time could result in dropped/slowed traffic (it may throttle or simply drop). Take a look at the router logs on each end and make sure that they are not running near capacity.

I agree that your reasoning is correct, because you are not sending a full WAN pipe full of data does not correlate with you being disappointed that you cannot do so successfully.


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[julius1]

Your T-1, on the otherhand, if it was misoptioned or takin errors, would drop, or atleast you would see major re-trans. Errors on a T-1 generaly count on a threshold. Once the threshold is reached the T-1 shuts down and needs to be cleared of the errors before it will come up again. You can contact your telco and have them run a test long term in the evening to verify the cleanliness of your T-1. Unless this is a "frame relay" T-1, there are no options to it, it's just a pipe. If the pipe is not taking errors then the problem exists beyond that of the termination of the circuit itself. The T-1 is just a tube, it will send what you gave it at the speed it is given not to exceed 1.5MBS, especially if it is a point to point. Easiest way to rule out the medium and or confirm the problem is the medium is to have the test ran. If it is T-1 B8ZS, tell the telco to run "all 0's" for the test. It is the largest bit based test you can run on it. If it is AMI tell them to run "QRSS" (pronounced quasie) and "all 1's" for at least 30 minutes to an hour. This will again either eliminate the pipe and tell you to focus on equipment or settings beyond it or will prove it to be the problem.

julius.gazdag@centurytel.com
Im a Telco guy, I can get you where you want to go, but I can't guarantee it will work when you get there!