In a message dated: Mon, 08 Oct 2001 14:22:14 EDT Brian Chabot said: >I have an odd question related to network performance... > >In general, do most current Linux NIC drivers default to full-duplex or >half-duplex?
Well, in theory, I think it depends upon the protocol, but I think in general, the cards will auto-negotiate with whatever network equipment they're connected to. The 10Mb ethernet spec I believe calls for 10Mb HD, whereas the 100Mb spec calls for 100Mb FD. I'm not sure what the 1000Mb calls for, but I would imagine that it would be FD as well. Additionally, any of them *can* be run in both FD and HD provided the media (i.e. cabling) and network gear are capable of doing so. 10Mb ethernet is traditionally HD I think because the media at that time was co-axial cable, which was only capable of HD. Once you move to UTP (or multi-mode fiber), though, you now have 2 channels for the datastream to travel over, thus allowing for FD connectivity. So, you could easily (again, in theory) have 1 NIC[1] in your Linux box and move the system from a 10Mb HD network to a 100Mb FD network and, in theory, the OS wouldn't know, because all that negotiation is performed at the physical layer of the NIC itself. [1] This is assuming you can find a 10/100Mb ethernet *combo* card which comes with both BNC or AUI *and* UTP ports on it. These "combo" cards were quite abundant a few years back when 10Mb ethernet was considered "State of the Art", however since UTP has pretty much taken over everywhere but where fiber makes more sense, I don't think anyone is still manufacturing combo cards! So, to make a long answer a little longer, I don't think the Linux drivers are responsible for either the 10 vs 100 Mb or the HD vs FD negotiation of a network connection, it's all done at the physical layer between the card and the equipment it's connected to. That being said, auto-negotiation is a horrible and bug-ridden spec. And it's not uncommon at all to see a card at one end negotiation a 100Mb HD connection while the switch at the other end thinks it should be using a 100Mb FD connection. I've even seen a 10Mb FD to 100Mb HD negotiation before! It seems the worst occurences take place when connecting Bay/Nortel Networks switches to Cisco switches/routers. Could just be me :) Hope that helps, and if someone who knows more about the ethernet device drivers than I can correct me, I'd be quite grateful :) ********************************************************** To unsubscribe from this list, send mail to [EMAIL PROTECTED] with the following text in the *body* (*not* the subject line) of the letter: unsubscribe gnhlug **********************************************************
