Full Duplex vs Half Duplex

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PawsForThought - 16 Aug 2005 18:50 GMT

I have been experiencing a problem where I get a balloon pop up saying
"a network cable has become unplugged". I have DSL using SBC's
services. I have a 2Wire modem/router that is connected to the Gigabit
LAN on my motherboard with an ethernet cable. I contacted SBC's tech
support and did some trouble shooting such as replacing the cable,
checking settings, etc. The problem is not always happening, so
sometimes I can connect to the internet and other times not.

I went into the network adapter's properties (Intel 1000 Pro, I
believe) and it gave me the option instead of Auto negotiation, to
change speed to 100/Full duplex or 100/Half duplex. I changed from
Auto to 100/Full Duplex, and so far, it seems to have cured the
problem, but I only tested for one day. Anyway, my question is what is
the difference between Half Duplex and Full Duplex?

thanks very much.

P4 3.2C; P4C800-E Deluxe;Corsair TWINX1024-3200XL (2X512); BFG GeForce
5900Ultra; Audigy; 2 WD SE 80G hdd in RAID 0; BenQ DVD Writer, CDRW &
Lite On DVD Rom; Tt Purepower 560 psu; WinXP Pro

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Steve Winograd [MVP] - 16 Aug 2005 19:00 GMT

>I have been experiencing a problem where I get a balloon pop up saying
>"a network cable has become unplugged". I have DSL using SBC's
[quoted text clipped - 12 lines]
>
>thanks very much.

A web search for "Half Duplex" and/or "Full Duplex" shows millions of
pages with the answer. Here are two of them:

http://www.webopedia.com/TERM/f/full_duplex.html
http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212221,00.html

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Steve Winograd, MS-MVP (Windows Networking)

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PawsForThought - 16 Aug 2005 20:27 GMT

> A web search for "Half Duplex" and/or "Full Duplex" shows millions of
> pages with the answer. Here are two of them:
>
> http://www.webopedia.com/TERM/f/full_duplex.html
> http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212221,00.html
> --

Thanks for your reply, Steve. I think I understand the definitions so
my question is more particularly which one would I use with DSL? I
would think full duplex but just want to be sure.

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Richard G. Harper - 16 Aug 2005 23:29 GMT

You want to use whichever one your network hardware supports - in this case
it appears that full duplex is the proper choice.

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>> A web search for "Half Duplex" and/or "Full Duplex" shows millions of
>> pages with the answer. Here are two of them:
[quoted text clipped - 6 lines]
> my question is more particularly which one would I use with DSL? I
> would think full duplex but just want to be sure.

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Alan Strassberg - 16 Aug 2005 23:57 GMT

>Thanks for your reply, Steve. I think I understand the definitions so
>my question is more particularly which one would I use with DSL? I
>would think full duplex but just want to be sure.

    You should set it to auto-negotiate. If you hard code
    one side of a link to full-duplex the rule is the other side
    will go to half-duplex. When this happens you have a mismatch
    and lots of collisions. So, you eith hard-code BOTH sides to
    full duplex, or set to auto. I only hard code if auto doesn't work.

                    alan

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PawsForThought - 17 Aug 2005 14:22 GMT

> >Thanks for your reply, Steve. I think I understand the definitions so
> >my question is more particularly which one would I use with DSL? I
[quoted text clipped - 7 lines]
>
> alan

Thanks for your reply, Alan. The reason I was hard coding it was
because of my "a network cable has become unplugged" problem. I had
read that hard coding it may correct the problem. Do you know how I
would hard code my 2Wire router/modem (model 1701HG)? or, do you think
I should change the network adapter back to Automatic? I did have Zone
Alarm on this computer, and even though it wasn't running, I understand
it can impact the network stacks, so it can cause problems. I have
completely uninstalled it, manually, per the instructions from Zone
Alarm. I also rebuilt the winsock.

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