Network disconnect

[grafx1]

we have a network and sharing ADSL

DLink switch / Router / DLink cards

Win XP Pro

sometimes i see the LAN icon disconnected and reconnect again !!

What's the reason ?

Thanks.

[grafx1]

I also have found that error in Event viwer:

((Your computer was not able to renew its address from the network (from the

DHCP Server) for the Network Card with network address 00xxxxxxx. The

following error occurred:

The semaphore timeout period has expired. . Your computer will continue to

try and obtain an address on its own from the network address (DHCP) server.))

Can any one explain that to me??

Thanks