Poor network performance

What cabling have you got? Make sure all cables are CAT5 or 6. Also what speed are your switches? Make sure they are 100Mb switches. Also have you done any setup on the switches??

Make sure that there your cables are all in good repair, that they are not located near heavy machinery and are at least 3 feet away from any source of electromagnetic radiation, and that each cable is no longer than 100 meters (include the length of patch cables.)

You may want to get a lan tester and see if you are getting a good signal throughout your network. You may be able to diagnose problem areas. Be sure that cables to your server and between your switches especially are in good repair.

hoo boy. this will be fun (for us, anyway)...
has it always been like this?
what protocols are you running...
what is slow..everything? browsing? logons?
good move on increasing the RAM, did it help?
give us an example of 'falling off'...
whenit falls off, is everybody off the network or just some folks? the same folks every time?
is the server running a 10/100 nic card? can you force it to 10 only? and try that also on any problem machines?

Use Network Packet analyser to findout a real cause.
The cause could have been a falied network card (LAN/NIC card) on anyother your machines. or if you don't have any analyser software with you means try a failsafe method like disconnect each machine from your network and finally the server, one by one and check ur network performance.you might find out the exact culprit by this method

My suggestion is that if your network does only with TCP/IP protocol then remove all the other protocols from the network properties of all the machines including you Primary domain controller (Server). The other protocols, like IPX/SPX,etc., broadcast a lot on the network. Normally all applications & resources run only in TCP/IP protcol in present day scenario.

One thing that will kill a network is duplex mismatch. If one end is set (or autonegotiated) to half duplex and the other for full duplex you will have more collisions and retransmits than real data. Autonegotiation is great when it works but somemixed vendors (3Com NICs to Nortel switches in my experience) equipment don't seem to handle it properly.

Is the network "falling over" after the upgrade ?

Most people forget that there is paging file size in NT4 as well as W2K that need to be readjusted whenever they upgraded the memory.

When you initially installed NT4 with 128MB of RAM, paging file size is automatically set to 150-170MB on your (usually) C: drive. The paging size is needed to perform some memory swapping. Microsoft recommends that paging file size should be at least ( SIZE_OF_RAM + 12MB ). In your case, the paging file size should be readjusted to 524MB. Have you done that ?

When paging file size is smaller, memory couldn't be mirrored smoothly into paging file.

The paging size could be found in SYSTEM applet of Control Panel.

vh_s

Anyone running Kazaa type stuff on their system?

Also, is your server constantly paging to the HDD?

Increasing the server Ram should help some with 25 concurrent users.

Ok my 1p worth

are you running any Printer Server, or management switchs..

i notice my network was slowing down and it was because i didn't keep the printer servers and the swithc software uptodate it increase logon time once done my 2 mins.. that some different in education where we have 150 people logon every hour

Many thanks to all those that responded to this thread. There has been a great improvement since upgrading the memory and yes, I did alter the page size. Since my original posting I have been able to identify the "Falling over" problem as being specific to two particular, bespoke software packages which I have now fixed. Thanks all of you for your suggestions