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[Richard Carlson <>]

Hi Lalit;

The IEEE 802.3 Ethernet spec describes how hosts can auto negotiate the speed and duplex settings between a host NIC and the peer switch port.  Most NICs will auto select the speed (10/100 or 10/100/1000) and the duplex setting (full or half).  In full duplex mode the NIC can send and receive data simultaneously.  In half duplex mode the NIC will alternate between send and receive mode.  As you have observed there are options inside the NIC driver to allow you to select the auto-negotiate or one of several fixed configs.   It should be noted that the switch port has these same options.

if the auto-negotiate option is selected the, the NIC communicates with the switch and automatically determines the speed and duplex settings.  If either the switch or NIC is set to a fixed config, then the auto-negotiation function will be disabled and the system will fall back to half-duplex mode.  

The best step is to contact the campus network operations help desk and report a problem.  Ask them to check the switch port settings.  If they are set to a fixed config, then your NIC must be set to match.   The campus staff should be able to tell you what the switch port is set to, and what it's current settings are.

Rich 

On Feb 17, 2009, at 3:06 PM, lalit kumar wrote:

hi
 i am in a college and there is a  100Mbps/full duplex LAN and my problem is that i have uploading problem,when LAN connection is 100Mbps/full duplex then if i try to upload data then it usually starts with 500KBbps and soon it starts decreasing and finally reducing upto 3-4 Kbps.but i have no problem in downloading normal downloading speed within LAN is 11.3MBps(close to 100Mbps).same problem arises when link speed is set to 100Mbps/half duplex and 10Mbps/full duplex.but when link speed is set to 10Mbps/half duplex then there seems to be no problem with uploading and downloading.
please help, i have tried everything i could and its so frustrating, i don't know how to fix this duplex mismatch problem
i am using windows xp /SP2 professional edition with Compaq 6409TU laptop.
i have 100Mbps LAN card with Intel(R) PRO/100 VE Network Connection Driver in my laptop.

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Richard Carlson

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