[openbeosnetteam] Re: header files
- From: "Bebert" <info@xxxxxxxxxxxxxx>
- To: openbeosnetteam@xxxxxxxxxxxxx
- Date: Sat, 9 Feb 2002 17:18:37 GMT
>But is it correct that 1500 bytes is the maximum size=3D3F I often got
>more, and IIRC the network card specs said something of 1536 or 1518.
>We should just use the ether frame size returned by the driver and
make
>no assumptions about it (if it's in the area about 1500)=3D3F
See http://www.cisco.com/warp/public/105/encheat.html. The spec is
1518 for Ethernet, which is 1500 for data, 12 for src and dst mac, 2
for type and 4 for CRC =3D 1500+12+2+4=3D1518. So if you strip off the
misc ethernet data, then the frame will be 1500 bytes max.
Incidentally, there was a discussion earlier about whether it was 802.3
or Ethernet. Ethernet has a "type" field and 802.3 has a "length"
field. I did a bunch of packet captures on my network and it's all
Ethernet with a type field for IP. IPX on the other hand can use any
of 4 different frame types, but I doubt we'll ever mess with that.
>AFAIK IF=3D5FSETPROMISC is not implemented in every driver, at least not
in
>mine yet :-)
>So that could be the reason why it fails.
>BTW what exactly is the promiscuous mode=3D3F
Typically a NIC card will only pick up broadcasts or packets that are
destined for it. Promiscuous mode tells it to grab all packets. This
is necessary for "sniffer" applications.
Peder
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