LCS - Windows Messenger port information for IM, File Transfer, Audio and Video

This post is about the ports in use for Windows Messenger and Live Communications Server.

VERY IMPORTANT: only the IM traffic goes through the LCS server, all other traffic is peer to peer.

Firewalls and Windows Messenger
Options exist for using the advanced features of Windows Messenger with a non-UPNP firewall. Points to consider on this topic include:

  • Peers on the same side of the firewall can use all of the features of Windows Messenger.
  • IM and Presence will work through most firewall configurations.
  • Ports can be opened to allow the peer to peer protocol to function via a firewall.
  • Port ranges can be set to fixed ranges using group policy.

This section will document the basic protocol port usage for the Windows Messenger client used in the Microsoft Live Communications Server enterprise scenario.

Instant Messaging
IM and presence are carried over SIP signaling.  The SIP signaling can be carried over TCP in clear text or encrypted in a TLS session.
TCP Mode
The clients send and listen on a dynamic port for SIP traffic. The client will send to the server port.

The server listens on the default port of 5060(TCP). Server will send notifications to a client’s dynamic port. The dynamic port range can be controlled via policy but the use of TLS is recommended instead.

TLS Mode
Client will listen over the same connection that is open to the server.
The server listens on port 5061(TCP) by default. Server will send to client only over the client’s TLS session.

Whiteboard and Application Sharing
The Whiteboard and Application Sharing components of messenger use the T.120 protocol.
The port used is fixed and can not be changed.
Protocol    Port
T.120        1503(TCP)

File Transfer
The messenger file transfer protocol uses the TFTP running over TCP.
The port range used is fixed and can not be changed.
Protocol    Ports 
TFTP        6891 – 6900 (TCP)

Audio and Video
Audio and video each use a pair of UDP ports for a RTP (Real Time Protocol) stream to transmit data and RTCP (Real Time Transport Protocol) to control the session stream.  The ports used are dynamic by default but can be controlled via group policy registry settings.
Policies to control port usage:
Policy                          Description                                                                                Default    Min    Max
MinSipDynamicPort    Specifies the lower port used SIP                                               7100       1024  65535
MaxSipDynamicPort   Specifies the highest port used for SIP                                        7103       1024  65535
MinMediaPort             Specifies the lower port used for Audio and Video signaling        5350       1024  65535
MaxMediaPort            Specifies the highest port used for Audio and Video signaling      5353       1024  65535

Toml LCSKid

Happy Birthday lil sis