Full Duplex and Half Duplex- How to utilize in a NIC

[Chowder]

I know my network cards support full duplex operating mode, instead of 10/100 is it 20/200? How do I set it up? Thanks dOOds.

 

[ravedave]

as far as I know "full duplex" means you can send AND recive.
so if you had this off you could only do one at a time.
you will only get 10/100 no matter what.

 

[Kill_Phil]

yes ravedave is right, full duplex lets you send and recive at the same time. it does not however allow you to send any faster than you normally would. it still uses the available bandwidth. half duplex only allows you to send or recive, not botha the same time and the bandwidth is still exactly the same.

 

[Sir Fredrick]

Full duplex IS considered "20/200", but it's a bit misleading. As has already been said, you can still only recieve at 10mbps, but you can send at 10mbps at the same exact time...simple math shows that 10+10=20, and that's where they get that number. I'm sure it does help performance if your computer doesn't have to wait before it can send data back, and it can send confirmations immediately and such...

If you have a two computer network: forget about a hub or switch and buy/make a crossover cable. If the NICs are communicating directly they can support 100BaseTX at full duplex.

If you have more than two computers on your network, your best bet is to get a switch. Hubs don't support full duplex, unfortunately.

 

[Chowder]

Thanks guys, yeah I have a hub and an internet cable modem router. I was thinking of getting a switch for the dedicated bandwidth and stuff. Thanks again.

 

[Auric]

Does this make any difference with connection to an ISP? My NIC was half duplex by default. I seem to remember someone recommending to leave it that way for cable but never really got a definitive answer.

 

[dszd0g]

Full duplex even makes more of a difference when a machine has heavy traffic. Since it is bi-directional packets can be sent and received at the same time as has been stated. The way 802.3 (and all the other ethernet standards for that matter) work is there isn't any sort of handshaking like on token ring, FDDI, CDDI, etc. When a machine wants to send a packet with ethernet it sends it. I believe, if a machine operating at half duplex send and recieves a packet at the exact same time it collides.

I know that when I monitor the ports on my Unix machines at work I see collisions on the machines running at half duplex but no collisions on the machines running at full duplex when using a switched network. To the best of my knowledge hubs only do half duplex (Basically a hub can only deal with one packet at a time from any machine in or out -- lots of collisions). Switches can do half or full duplex. When operating in half-duplex on a switch one only gets collisions when that machine sends and receives at the same time. I believe really early switches didn't buffer traffic well and one could get a collision if the same machine got traffic from more than one machine at the same time, however to the best of my knowledge this is not the case anymore.

 

[dszd0g]

<< Full duplex IS considered &quot;20/200&quot;, but it's a bit misleading. >>



I hate that naming scheme. Anyone who believes it is going to be just as happy as 56K modem users hoping to upload at 56K (Well, for almost everyone hoping to download at 56K for that matter.) Well, at least V.92 should be out at some point and improve the upstream for those poor modem users out there... Getting off topic.