[mrtg] Re: (no subject)

Alex van den Bogaerdt alex at slot.hollandcasino.nl
Wed Sep 8 00:22:33 MEST 1999

> Q:
> When looking at one (or many) of my routers on the graphs, the output
> line is less, sometimes far less, than the input line.  What does this
> mean?
You are not graphing a router. You are graphing an interface on that
router. A router has at least two interfaces. Traffic coming in on one
interface will go out on the other.
If you would run, for instance, a web service you will have far more
traffic going one way than the other.

webserver <---  router <---  internet            request from client
webserver  ---> router  ---> internet            answer to client

Traffic will be:
eth0  : low in, high out
eth1  : high in, low out
serial: low in, high out

>        Is the router buffering traffic?  If so, how do we determine if
> the router is performing at its best (input/output ratio)?

It will (most likely) be buffering however this does not show on your
graphs as it won't buffer for long periods of time.

Performance of a router has nothing to do with the in/out ratio. It has
to do with being able to forward packets. If you would like to transfer
some amount of data and the bottle neck would be the router, then it is
not performing well. Most likely other parts of the link will be the
bottle neck and your router is performing below maximum capacity.
At some amount of data, your router is at peak capacity and when you try
to push more data through it, the throughput will either stay the same
or it will even drop drasticly. When that happens, you should have done
an upgrade/replacement and you are already late.

I'm sure somebody will have comments on this but I'm also pretty sure
above lines will be true for the bigger part.


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