Topic Last Modified: 2014-02-05

By default, Lync client applications can use any port between ports 1024 and 65535 when involved in a communication session; this is because specific port ranges are not automatically enabled for clients. In order to use Quality of Service, however, you will need to reassign the various traffic types (audio, video, media, application sharing, and file transfer) to a series of unique port ranges. This can be done by using the Set-CsConferencingConfiguration cmdlet.

You can determine which port ranges are currently used for communication sessions by running the following command from within the Microsoft Lync Server 2013 Management Shell:

Assuming that you have not made any changes to your conferencing settings since you installed Lync Server 2013, you should get back information that includes these property values:

If you look closely at the preceding output, you'll see two things of importance. First, the ClientMediaPortRangeEnabled property is set to False:

That's important because, when this property is set to False, Lync clients will use any available port between ports 1024 and 65535 when involved in a communication session; this is true regardless of any other port settings (for example, ClientMediaPort or ClientVideoPort). If you want to restrict usage to a specified set of ports (and this is something you do want to do if you plan on implementing Quality of Service) then you must first enable client media port ranges. That can be done using the following Windows PowerShell command:

The preceding command enables client media port ranges for the global collection of conferencing configuration settings; however, these settings can also be applied to the site scope and/or the service scope (for the Conferencing Server service only). To enable client media port ranges for a specific site or server, specify the Identity of that site or server when calling Set-CsConferencingConfiguration:

Alternatively, you can use this command to simultaneously enable port ranges for all your conferencing configuration settings:

The second thing of importance you will notice is that the sample output shows that, by default, the media port ranges set for each type of network traffic are identical:

In order to implement QoS, each of these port ranges will need to be unique. For example, you might configure the port ranges like this:

Client Traffic Type	Port Start	Port Range
Audio	50020	20
Video	58000	20
Application sharing	42000	20
File transfer	42020	20

In the preceding table, client port ranges represent a subset of the port ranges configured for your servers. For example, on the servers, application sharing was configured to use ports 40803 through 49151; on the client computers, application sharing is configured to use ports 42000 through 42019. This, too is done primarily to make administration of QoS easier: client ports do not have to represent a subset of the ports used on the server. (For example, on the client computers you could configure application sharing to use, say, ports 10000 through 10019.) However, it is recommended that you make your client port ranges a subset of your server port ranges.

In addition, you might have noticed that 8348 ports were set aside for application sharing on the servers, but only 20 ports were set aside for application sharing on the clients. This, too is recommended, but is not a hard-and-fast rule. In general, you can consider each available port to represent a single communication session: if you have 100 ports available in a port range that means that the computer in question could participate in, at most, 100 communication sessions at any given time. Because servers will likely take part in many more conversations than clients, it makes sense to open many more ports on servers than on clients. Setting aside 20 ports for application sharing on a client means that a user could participate in 20 application sharing sessions on the specified device, and all at the same time. That should prove sufficient for the vast majority of your users.

To assign the preceding port ranges to your global collection of conferencing configuration settings you can use the following Lync Server Management Shell command:

Or, use this command to assign these same port ranges for all your conferencing configuration settings:

Individual users must log off from Lync and then log back on before these changes will actually take effect.