Re: {bb} netstat larrd graph on Linux incorrect

[Henrik Storner <henrik-bb@hswn.dk>]

In <4325FD50.4030600@micron.com> Tom Schmidt <tschmidt@micron.com> writes:

>Has anyone corrected the known issue on Linux where the "netstat -s" 
>output reports TCP throughput in segments rather than bytes?  This makes 
>the LARRD graphs reporting of bits/second incorrect.

This happens on other platforms also, I believe. In fact, as I recall the
LARRD code, the only platform where the netstat graphs are right are
Solaris.

The problem is that quite a few systems don't count the number of bytes
sent/received, but only the number of packets ("segments") going in and
out. And packets can var from 64-1500 bytes.

>A rough conversion of segments to bytes would be to multiply by the MSS 
>of 1460 (assuming MTU=1500).  Should this conversion go somewhere in the 
>netstat-bf.sh code or elsewhere?

If you want to use this guesstimate, then you can put it into the
calculations performed by RRD at the server end, in larrd-grapher.cgi.
It already performs a bytes->bits conversion. Personally, I think 
that would be misleading. Hobbit uses a different format of the
RRD file with separate counters for packets and bytes, so you can
get the correct BPS values for those platforms that report data, and
you'll know you're only counting packets on the other platforms. 


Henrik

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