Question : Problem: Gigabit vs 10/100 bottlenecks

I've been trying to eliminate periodic lagging in my network (Server 2003 on (1) Fileserver, 6-8 XP-Pro PC's).  It does not seem to affect internet connectivity, just lagging with files that reside on the fileserver and are being accessed by PC's.  I realize that there are many possible casues for this, but I started troubleshooting by upgrading to a Gigabit router, a Gigabit switch, and a gigabit NIC in the FS machine.  I'm making several assumptions:

1.  Individual machines accessing FS files are not pushing the capacity of a 100MBPS connection.
2.  The FS is being simultaneously accessed by several machines, the sum of these connections may or may not approach 100MBPS.
3.   By increasing the connection speed between the FS and the router, the FS can better handle the combined traffic of multiple machines.

#3 seems to be the big assumption, because I'm guessing that the router combines all the network data flow much like a manifold would combine water flow into a single large pipe.  I have been advised that this is not actually the case, and that the network switch does not allow all the PC's to communicate simultaneoulsy.  Instead, the machines are rapidly taking turns making solo connections to the server, in which case the data transfer is limited by the 100MBPS connection of each PC as it takes its turn.  Is this accurate?

The hardware changes seem to have improved the connection speeds, but I realize that this could be a conicindence if the original problem was something as simple as a bad NIC card in the FS (before the gigabit upgrade).  

I guess what I'm looking for is an explanation of how the gigabit router & switch handle multiple machines connecting to the single fileserver.  Does the gigabit hardware allow for greater throughput of several 100 MBPS machines communicating simultaneously, or are they all taking turns connecting to the FS with a 100MBPS bottleneck created by their individual NIC cards?

If in anyone wants to throw in any other likely causes for the lagging I would very much appreciate it...

Thanks in advance.

jdj

Answer : Problem: Gigabit vs 10/100 bottlenecks

Duplex - yes, configured on the NICs in their properties.  If there isn't anywhere to do it on your switch, odds are they're AUTONEGOTIATE.  Make them the same on the computers.

Water is actually a pretty good analogy - except for bits on the wire - then it's one bit at a time and the faster the gear can do the encoding the faster the throughput.    It's more like Possibility 2.  Having a bunch of small connections to clients and fat pipe (fast) connections to servers is good and a common practice.