100mbit lan

[bobsmith1492]

From what I've seen, this seems to be the case. I was transferring files from comp to comp via a crossover cable and the network usage maxed out at about 83 +/- a couple, usually minus. This converts to a transfer rate of about 10.5MB/s. When transferring directly from one hard drive to another, however, they averaged 27MB/s, so the HDDs aren't the bottleneck there. Why can't LANs transfer at their rated speed?

 

[halfadder]

That's not too bad. The 100 Mbit speed is the total wire speed per direction. Your data will be wrapped in at least two packet formats (an Ethernet packet and then the format packet). In the case of FTP between two machines you have Ethernet->IP->TCP->FTP, four layers of packet wrappers. These all add to the overhead. There's also error checking and correcting, pings between the two machines, ARP/RARP requests, and other stuff going on within the network, even if it's just two machines and a crossover cable.

From my real world experience, I've seen as much as 90 Mbit/sec transfer rate between two machines, but never faster than that. (That's not too bad, considering that in the very early days of 100Mbit, people with slower CPUs and ISA cards were lucky to see 25 Mbit tranfers!)

Gigabit is even more depressing. Even with jumboframes, you still won't even hit 500 Mbit between two machines. There's just too many packets to handle and too much overhead.

 

[Vegito]

Exactly

In real world nothing measures up, IDE does not hit their Ultra 133 limit, SCSI does not reach their Ultra 320 limit, etc, etc, etc.

Go gigabit, I think earlier gigabit card/switches never hit more than 65% of total speed, it might be higher now

 

[V00D00]

There's a lot of TCP overhead. If you really want to get the most out of your transfers try switching the protocol. You can usually use UDP packets if it's a stable network. They have very low overhead, so you'd probably see that transfer rate go up.

 

[Anubis]

thats about normal, my 100mbit home network maxes out at between 8.5-9.5 MB/s

 

[VirtualLarry]

Yeah, that's pretty good, I usually only hit 6MB/s over the LAN, but then again, my onboard Via Rhine II NIC is poor. (I got better xfer rates using a USB1.1 10/100 NIC, sometimes as high as 8MB/s.)

Edit: After I posted that, I realized, that *can't* be right, for the USB NIC. I'm going to have to dig that out and re-test it again, perhaps it's really a USB2.0 NIC, even though it was packaged for the PS2 console, which I think is only USB1.1.

 

[jvarszegi]

Originally posted by: V00D00
There's a lot of TCP overhead. If you really want to get the most out of your transfers try switching the protocol. You can usually use UDP packets if it's a stable network. They have very low overhead, so you'd probably see that transfer rate go up.

What??? With no delivery guarantee??? You want this guy to trust his files to that? I thought it was only suitable for things like streaming media.

 

[VirtualLarry]

Yeah. I'd take the TCP overhead any day, rather than simply pass NetBUEI frames directly on the wire. You get a little noise on the wire, your packets spoil along the way, and you end up with corrupted files. (True story. I always file-compare stuff after copying over the network, or ZIP/RAR it first, now.)