Microsoft KB Archive/278887

= MSN Messenger Service Cannot Perform File Transfers or Make Voice Connections Through NAT =

PSS ID Number: 278887

Article Last Modified on 11/20/2003

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The information in this article applies to:


 * Microsoft Windows 2000 Server SP1
 * Microsoft Windows 2000 Advanced Server SP1
 * Microsoft Windows 2000 Professional

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This article was previously published under Q278887



SYMPTOMS
After you configure Windows 2000 Server to serve as a Network Address Translation (NAT) router, client computers that use the NAT router are not able to use MSN, The Microsoft Network Messenger Service version 3.0 program to transfer files or establish voice connections. This problem also occurs when you are using Windows 2000 Professional with Internet Connection Sharing (ICS).



CAUSE
This problem occurs because MSN Messenger file transfer and voice features do not work through NAT routers because there is no NAT editor to correctly translate the IP header information.



RESOLUTION
To work around this problem, install Proxy server, create a Winsock protocol definition for TCP ports, and then install the Winsock proxy client on the computers that use the proxy server.

Winsock Protocol Definitions
To enable voice communications, make sure that outgoing TCP connections from port 6901 are enabled. Also enable UDP packets where either the source or the destination port is 6901.

To enable file transfers, enable both incoming and outgoing TCP connections to the 6891-6900 range of TCP ports. This allows each sender to perform up to 10 simultaneous file transfers. Note that if only TCP port 6891 is open, users are only able to perform one file transfer at a time.

To enable messaging, enable outgoing TCP connections to TCP port 1863.

NOTE: On the Connections tab in the MSN Messenger Options dialog box, make sure that the I use a Proxy Server check box is not selected.



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.



MORE INFORMATION
By default, a NAT router translates IP addresses and TCP/UDP ports. If the IP address and port information is only in the IP and TCP/UDP headers, then the application protocol can be translated properly.

Some programs and protocols (such as FTP) store IP address or TCP/UDP port information within their own headers. For these protocols or programs to be able to work through a NAT router, there has to be a method of opening the packet to translate the address or port information that is contained in the payload. To accomplish this requires a NAT editor.

Windows 2000 Server has NAT editors for the following protocols:
 * FTP
 * ICMP
 * PPTP

Windows 2000 Server does not include NAT editors for the following protocols:
 * SNMP
 * LDAP
 * IPSec
 * Microsoft COM
 * RPC
 * H.323

Keywords: kbnetwork kbprb KB278887

Technology: kbwin2000AdvServ kbwin2000AdvServSearch kbWin2000AdvServSP1 kbwin2000Pro kbwin2000ProSearch kbwin2000Search kbwin2000Serv kbwin2000ServSearch kbwin2000ServSP1 kbWinAdvServSearch

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