ServersBack To Basics: Troubleshooting Proxy Server 2.0 -- Part 2 ...

Back To Basics: Troubleshooting Proxy Server 2.0 — Part 2 Page 3




Thomas Shinder

WinSock Proxy Related Problems

The WinSock Proxy service is used to provide access for
WinSock programs that are not able to use the Web Proxy service. Since the Web
Proxy service supports only CERN compliant applications and only the FTP, HTTP,
HTTPS and gopher protocols, you must use the WinSock Proxy service to support
any other application layer protocols you want to put into service. Common
examples would be for SMTP, POP3, and NNTP.

The WinSock Proxy service is able to accomplish this amazing
feat by replacing the winsock.dll’s on the client machines that need to use the
WinSock Proxy service. This is one of the major sticking points for many
administrators. They are loath to add client
software because of concern over how the client software will interact with
other software installed on the client machine. In our experience, the WinSock
client has little or no effect on the overall performance of client workstations
on which it is installed.

The WinSock Proxy client .dll’s will pick up the request
made from user agents on the client workstations and forward those requests to the WinSock
Proxy service on the Proxy server. All this takes place in the background and
the users are not aware of the process. There is no application
configuration required in most cases.

WinSock Proxy related problems often can be traced back to the
Local Address Table or LAT. The LAT is used to determine if a request should be
handled by the WinSock Proxy service, or if the request can be forwarded directly
to the server. The LAT therefore should contain address ranges
that encompass your internal network. If a foreign address is included in the
LAT, requests to that address will not be subjected to WinSock Proxy service
access controls.

Common service requests such as DNS must go through the
WinSock Proxy client software. If the machine tries to make a DNS query and it does not
have permission to do so, the DNS query will fail. Normally, the DNS Server is
on the internal network, therefore access permissions are not an issue. If
DNS queries are failing, make sure that the DNS Server is included on the LAT so
that WinSock Proxy access controls are not applied.

You can also use the chkwsp32.exe application on the
WinSock Proxy clients to check out the connection status between the WinSock
Proxy client and server. Often you’ll find out that the WSP Service has been
disabled in the Control Panel, and its just a matter of turning the client back
on and everything is fine. Also, make sure that the Internet connection is
actually functional by going to the Proxy Server itself and confirming that
Internet access is possible.

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