Question : Network transmission speed

Hi Experts,

I'm in the process of trying to measure the transmission speed of my network. I have difficulty understanding the correlation between the network capability (1 gigabit Ethernet) and the transmission speed of data (35 megabyte per second). What should the transmission speed be in megabyte per second on a 1 gig capable network (1 gig switch and 1 gig NICs in both servers)?

Also, I've found some tools that can do point to point testing on a LAN - does anyone know where I can find a tool that can show me the possible network capacity, the network usage and also the type of data that is occupying the LAN?  

If someone could perhaps help regards the above questions I'd be grateful. Many thanks!

Answer : Network transmission speed

Break it down to bits.

GB      1
MB      1,024 (x1024)
KB      1,048,576 (x1024)
B      1,073,741,824 (x1024)
b      8,589,934,592 (x8)

You have roughly 8.5 billion bits.  Your network can move 1Gb in one second.  (One Billion bits in one second).  So, therefore, a 1Gb network can move 8.5 Billion bits in about 8.5 seconds.

Note - that is a maximum THEORETICAL speed.  You have to add protocol overhead - which is layer 2 headers, layer 3 headers, etc.  So, say you lose 20% efficiency - because not all of that going through will be data - a lot will be protocol information.  So, multiply your 8.5 seconds by 1.2 and you're up to 10 seconds.

Again - this assumes max theoretical.  You will also be limited by hardware - disk i/O, RAM, CPU, NIC efficiency, other traffic on the network, etc.

Now, if you just want to see utilization, cpu, memory, errors, etc. you can use an SNMP monitoring tool like SolarWinds http://www.solarwinds.net.

If you want to see protocol information, this is a little more involved and requires equipment which actually sees the data and monitors it - sort of like a sniffer or packet capture.  If you're using Cisco gear, you could use programs/utilities like Netflow and NTOP and MRTG.

Hope this helps.