[mrtg] Re: Explanation of Graph

Peter Glanville peter_glanville at cuk.canon.co.uk
Fri Jun 13 13:24:30 MEST 2003

>HI All
>Please can the table below be explained. I am trying to find out the spped
>at which the device hanging onto the port 6/11 of our switch is going at.
>WHat does the In/Out mean and there is also Max Speed: 12.5 MBytes/s. What
>does this reference mean?
>Does the mean 24.kb is going into the port from the switch and 1.2 kb is
>going out into the network from the device??? Please explain??

Firstly, there is a difference between bits and Bytes.
Simply, a Byte (B) is 8 bits (b)

Your system is 12.5 MB/s, ie it can put through 12.5 Million Bytes per
second (OK, purist may say that is not "million" by 1024x1024, but lets not
12.5 MB = 12.5 x 8 = 100 Megabits per second
Beware. This number is read from a comment field in the switch. It can lie.
And it may be what the switch is capable of, and not what it is actually
doing (plug a 10Mb device in, the switch will slow down, but the litteral
may not change)

"In" refers to Into the port you are measuring.
"Out" is out of that port.
If you are looking at a port connected to a server, "IN" is from the server
Into the switch.

Old networks ran at half duplex, ie they talked OR listened (ethernet
collision avoidance etc)
Modern kit often supports Full duplex, ie send and receive simultaneously,
and so 100Mb network can send 100Mb/sec and receive 100mb/sec as well.
Servers, by their nature, tend to send more traffic than they receive.
So over the 5 minute period that you are averaging, you see more In to the
switch than Out of the switch to the server.
Current is the last 5 mins, max was the busiest 5 mins during the period
covered by the graph, average is the overall average for the same period.


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