Well... both.

Server-side: ASP.NET will only allow the web method to process for the
time specified in the executionTimeout setting in the web.config
(inherits from the machine's setting's in the root config file if not
specified):
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpgenref/html/g
ngrfhttpruntimesection.asp.

Client-side: The client web service proxy will also have a default
timeout but this can easily be changed programmatically using the
Timeout property (inherited from SoapHttpClientProtocol):
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpgenref/html/g
ngrfhttpruntimesection.asp

e.g.

MyServiceProxy.Timeout = 60000 // 1 minute

Josh
http://www.thejoyofcode.com/