Very Computer

by **Cheng Kwok Wing, Willi** » Tue, 09 Jul 2002 11:40:15

Hi,

I've questions regarding half-duplex and full duplex of network cards.
What is the difference between these two modes??

How can I config it??

Is it set automatically according to the other end of the network,
i.e. NIC that you connect to ??

Thanks,
William

by **Yuan Li** » Tue, 09 Jul 2002 12:53:34

Quote:> Hi,

> I've questions regarding half-duplex and full duplex of network cards.
> What is the difference between these two modes??

Half duplex is like your FRS radio; full duplex is like your cell phone.

Quote:> How can I config it??

It used to be driver loading time only. But other OS' have runtime tool
to configure this, I'd think that Linux should have. Just don't see one.

Quote:> Is it set automatically according to the other end of the network,
> i.e. NIC that you connect to ??

> Thanks,
> William

Most cards attempt to auto negociate with its terminating party (not usually a NIC, but most often a hub or a switch).

Yuan Liu

by **YAMABANA Kengo** » Tue, 09 Jul 2002 14:30:30

Quote:> I've questions regarding half-duplex and full duplex of network cards.
> What is the difference between these two modes??

When full-duplex mode, collision-detection line is used for
data-transmission.
Full-duplex mode can theoretically be twice as fast as half-duplex.

Quote:> How can I config it??

If your nic driver is compiled in kernel, add parameter(s) to
/etc/lilo.conf and run lilo.
If your nic driver is linked as a module, add parameter(s) to
/etc/modules.conf.
Different nics have different parameter configs.

YAMABANA Kengou

by **Eric P. McC** » Tue, 09 Jul 2002 14:39:38

Quote:> I've questions regarding half-duplex and full duplex of network cards.
> What is the difference between these two modes??

Half-duplex means that only one side can be talking at a given time.
When both sides try talking at once, you get a collision. Both sides
then wait a (more or less) random period of time, then try talking
again. The wait interval increases (geometrically?) every time
there's another collision, until eventually only one side will be
talking at a particular time.

Full-duplex means that both sides can talk at once. There are no
collisions and no fallbacks.

Quote:> How can I config it??
> Is it set automatically according to the other end of the network,

Yes.

Quote:> i.e. NIC that you connect to ??

If you're plugged into a hub, you are using half-duplex. It is not
possible to use full-duplex on a hub, by definition. If you're
plugged into a switch and your NIC supports full-duplex operation,
then your NIC should auto-negotiate to full-duplex (that is, it should
not require any configuration on your part unless something is
wrong). One thing to note: there's no reason all NICs on a switch
_have_ to use full-duplex mode.

--

"Last I checked, it wasn't the power cord for the Clue Generator that
was sticking up your ass." - John Novak, rasfwrj

by **Michael Heimin** » Tue, 09 Jul 2002 15:18:35

[..]

Quote:> It used to be driver loading time only. But other OS' have
> runtime tool
> to configure this, I'd think that Linux should have. Just don't
> see one.

Try:
www.scyld.com

There are mii-diag/mii-tool and other diag tools, running on every
NIC/driver that is mii status register aware, enabling to set this
on the fly.

Case yours is not mii aware, you can set speed/FD/HD during module
load, try 'modinfo -p <Your_NIC_module>', you need to edit
/etc/modules.conf, (depmod -a), stop the network device, unload the
module and finally start the network device again, it should pick
the module, with the changed params now...

Good luck

Michael Heiming
--
Remove the +SIGNS case mail bounces.

by **Joerg Morbitze** » Tue, 09 Jul 2002 17:13:09

: Hi,
:
: I've questions regarding half-duplex and full duplex of network cards.
: What is the difference between these two modes??
:
: How can I config it??

With most cards you can use "mii-tool" to see/adjust the speed...

Regards, Joerg.

: Is it set automatically according to the other end of the network,
: i.e. NIC that you connect to ??
:
: Thanks,
: William
:

Very Computer

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