Scrambled Network Data Problems

Hello Everyone,

Thanks again Newt for the help last time it worked out great . I have a different problem now with another network. The problem I have is that sometimes my data gets scrambled in the transfer and sometimes it doesn't. Could this be a virus? Can you run a network cable near electrial power or does it scramble the data sometimes and if you can't is there a type of network cable that I can get that will work good next to eletrical power lines? What other things will interfere with network cables? The server is a 133mhz and it feeds up to 5 comps at the same time. Is this computer capable of doing this well or do I need to upgrade? The comps pull the data from the server as they need it. The scrambled problem only happens when the comps are pulling data continuously from the server and then it only does it sometimes and not all the time. So in conclusion:

Scrambled Data Causes:

133mhz server feeding 5 comps at the same time - do I need to upgrade?

Network Cables near power lines or other interferance?

Virus?

Any suggestions would be appreciated.

Thank you for your help everyone

 

A few problems that I've encounted are florescent light ballasts, fan motors, server not on it's own dedicated circuit, and a server that was way too hot, (hot room).

 

A more descriptive post would be of some help, scrambeled data could be due to hte peice of flesh sitting between hte keyboard and the chair !!!

 

Strictly, collisions should not be a problem and wouldn't cause the problems described. Collisions are a normal part of ethernet operation and there are systems to catch them and deal with them. Excessive collisions (greater than 5% of traffic) can occur, and this is indicative of too many nodes on the network, or possibly a hardware fault. If excessive collisions is the only problem, all you should see at the client is poor performance rather than coruption of data.

The symptoms are more akin to network packets being corrupted. The resulting errors tend to be CRC checksum errors and runts (see this link to a Cisco help page.

Likely causes are:

• faulty network card or network hardware. Try disconnecting equipment and testing to see if fault goes away
• faulty cabling. Tell tale signs are: individual wires protruding from patch points and cable ends where sheilding has been cut too short; Over tight cable ties (you should be able to move the cables through the tie. If they pinch the cable and stop movement, they are too tight).
• overlong network cabling. CAT5/6 ethernet cable runs should not be longer than 100m
• interferance from noisy electrical sources such as florecent lights, welding kit, radio systems, fridges, mains systems (network cable runs should never share the same conduits as mains cable).

Your best bet is to get a network analyser and have a look at the packets. The cheapest way to do this is with ethereal, but note the FAQ: you won't be able to detect CRC errors with it. However, it will give you more information about the packets that are getting through. To analyse deeper you need kit that will capture the raw network data and that can get expensive (for professionals, I would recommend Fluke network analysers).

If you check the network with ethereal, and all is ok there, then there is also the possibility that the application is at fault and is corupting the data. However, use of Ethereal should help you detect that.

 

Thanks guys I have a starting point now. I have lots of interferance (network cables are run on electrical conduit, 220 power on the machines that the comps are in) I have long cables with tight zip ties on them, a 133 mhz comp running windows 98 as my server. The data that im sending are cnc programs so that one error in the data causes a mill to crash. So I will do the following upgrade the server comp, check cables for length, interferance and tightness. Thanks for the help guys.

 

I suggest it would be well worth your while to find a good computer network cabler. Network cabling is a skill that takes training and study to perfect. It is not just another job for an ordinary electrician. Getting cabling wrong, will cause you all sorts of problems. Running a fast ethernet network over poor cabling is like running a ferrari over a dirt track.

If your not sure where to start in finding a good cabler, I'd suggest your best bet is to contact one of the big cable manufactures such as Krone or Molex and ask them to recommend a cabler in your area. The big firms run training events, and will recommend cablers who have been trained to install their products correctly.

A good cabler should also be able to advise as to how to avoid noise problems - perhaps by using fibre runs through particular "noisy" areas.

If you do cabling right, you only need to do it once and it will last 3 or 4 times longer than any other component on the network. Invest in good cabling is ALWAYS a good investment in my experience.

Remember, as the cabling will last a long time it is better to add extra capacity when you install it. A good rule of thumb is to put two points in everywhere you think you currently need one.

And last - good network cablers are not necessarily good computer network engineers (in fact in my experience they never are). Go somewhere else for your switches, routers and servers.