Exact meaning of rx_bytes and tx_bytes

Exact meaning of rx_bytes and tx_bytes

[Jean Delvare]

Hi all,

I am wondering what exactly the rx_bytes and tx_bytes values exported 
under statistics/ in sysfs are supposed to represent.

Most popular ethernet drivers (8139too, e100, 3c59x) count the bytes in 
software, so they only take into account the bytes they actually send and 
receive. This excludes the 4-byte ethernet CRC if I understand correctly.

Other drivers, on the other hand, get the transfered bytes statistics from 
hardware registers, and these appear to include the 4-byte CRC in the 
total count. This is the case of sk98lin and e1000, for example.

So my question is, which drivers are right? Are we counting the emitted 
and received bytes at software level or at hardware level? Or do we just 
not care about the 4-byte/packet difference and both are acceptable?

Thanks,
-- 
Jean Delvare
Suse L3

Re: Exact meaning of rx_bytes and tx_bytes

[Stephen Hemminger]

On Mon, 9 Oct 2006 17:39:02 +0200
Jean Delvare <jdelvare@suse.de> wrote:

> Hi all,
> 
> I am wondering what exactly the rx_bytes and tx_bytes values exported 
> under statistics/ in sysfs are supposed to represent.
> 
> Most popular ethernet drivers (8139too, e100, 3c59x) count the bytes in 
> software, so they only take into account the bytes they actually send and 
> receive. This excludes the 4-byte ethernet CRC if I understand correctly.
> 
> Other drivers, on the other hand, get the transfered bytes statistics from 
> hardware registers, and these appear to include the 4-byte CRC in the 
> total count. This is the case of sk98lin and e1000, for example.
> 
> So my question is, which drivers are right? Are we counting the emitted 
> and received bytes at software level or at hardware level? Or do we just 
> not care about the 4-byte/packet difference and both are acceptable?
> 
> Thanks,

Does it really mater that much, unless you are charging people per
byte.


-- 
Stephen Hemminger <shemminger@osdl.org>