A very Strange Probelm

[abey.rajan]

I have a customer who is having a 512kbps leased line from us. He is riding on a cisco 1721 series router with RAD HTU E1 modems to terminated the line. The problem he is facing is like he is not able to attach any Microsoft Office fiels like doc,excel,powerpoint to any of the webmails like yahoo,rediffmail,hotmail etc. But if he is sending thorugh outlook express it is going. I tried back to back of the routers avoiding the leased line modems and found attachements are happening over webmail. But once it is connected to the line it will give a request times out error like, when we attach the ie explorer will give website found waiting for reply and will give a page cannot displayed message after sometime. It happens even if the size of the file is 1kb of dox or excel but i am able to attach any size of file say 1.5mb of mpeg file to these webmails at the same time. No idea where exactly is the problem.

If it is happening through smtp it should also happen through http. And when i tried to upload doc or excel file to a ftp server it is stopping after first 7 packets.

And i cannot download these formats from the ftp server, when all other formats are downloading. The objects connecting the routers are line and the leased line modems, so line is a layer one object which only carries the signals and modems are layer 2 device which will transmitt and recives data.

They are not intelligent enough to diffenentiate the format as all are changed into ip packet and signals. And also if over smtp is happening why should it blocks http. Any one can help me on this.

regards

Abey

[lgijssel]

When you tested back-to-back, were you using the same PC to transfer data?

If not, I would suggest you use another PC at the customers site (i.e. using the line & modems) to see if the results are the same.

This focus on Microsoft files can hardly be caused by a network problem, I rather suspect that you have some kind of virus on the PC's.

[abey.rajan]

I used the same machine, in both back to back and at customer end. I was able to attach over the backup isdn line which is provided to the customer in case of leased line failure, throught the same pc. The PC is fully protected for viruses, All the pc's inside the customer LAN is facing the same problem, and one more thing does the attachement is having any thing to do with the clockrate of the modems.

[lgijssel]

If this is the case, you should be able to see this happening with a scope or another instrument to check the clock rate.

I consider this possibility higly unlikely. When you are using the backup path, do you use EXACTLY the same route as over the leased line?

The problem does not nescessarily have to reside at your customers premises. Some node at the other side could be causing this as well.

The way you reported this issue gives the impression that you suspect the link although you cannot rationally explain it. Do not stare yourself blind at the link issue! When you assume that the cause is somewhere else, what are the next things that you can check? I suggest that you start to look at the matter from this point of view.

[abey.rajan]

I resolved the problem using the compression technique in router. When i forced the router for software compression the attachement happened. But without comporession it didnot worked. So is it a issue with the router..? Can anyone help me..?

[uniemeyer]

Hi,

it seems that the leased line has problems with long series of "0" or "1" and looses the synchronisation. We had ones the same problem with a leased line. The customer could not do a FTP File transfere but if he compresses

the file with WinZip ( avoiding of long series of "0" and "1") he was able to send the file.

This can be tested with the extended ping feature. Disable the compression

and send pings of e.g. 1500 Byte and set the data pattern to 0x0000 to send

long series of zeros and oxFFFF to send long series of ones. You should experience ping losses in one of the cases. If this is the case, you should check if you can enable scramblers on the leased line modems. This is the

normal technique to avoid long series of "0" or "1". Otherwise ask your provider or manifactur of the modems.

Hope this helps

regards Ulrich Marzoli

www.netaid.de