The printing route (using Citrix Universal Print Server or standard Windows Print Server)

Imagined how a printing works in Citrix if compared with a standard print job in windows. Here are the scenarios.

Client devices with locally attached printers such as USB, LPT, TCP/IP etc. will route print jobs directly from their Citrix session through to the client device then on to the printer. The print job from the Citrix session is sent via the ICA protocol and the print data is compressed. Outside of locally attached printers, Citrix has two different methods for sending your print job to a networked printer. The default route sends the print job direct from Citrix session to print server. This is enabled by default but configurable via a Citrix policy named Direct connections to print servers.

Consider the following scenarios if you have not disabled this policy:

Print server and Worker VM in same LAN, client device and printer in remote office

1. Worker VM sends print job direct to print server via LAN
   
2. Print server sends job to printer in remote office via WAN
   

Result = One LAN route and one WAN route taken. 

Print server and Worker VM not in same LAN. Print server, client device and printer in same LAN

1. Worker VM sends print direct to print server in remote office via WAN
   
2. Print server sends job to printer via LAN
   

Result = One WAN route and one LAN route taken. 

Now think of the following scenarios if you do have Direct connections to print servers disabled. This results in print jobs being routed through the client device.

Print server and Worker VM in same LAN. Client device and printer in remote office 

1. Worker VM sends print job to client device via ICA (over WAN)
   
2. Client device sends print job to print server (back over WAN)
   
3. Print server sends job to printer in remote office (back over WAN again)
   

Result = Three WAN routes taken. ICA compression is used from Worker VM to client device. 

Print server and Worker VM not in same LAN. Print server, client device and printer in same LAN 

1. Worker VM sends client print job in remote office via ICA (over WAN)
   
2. Client sends job to local print server via LAN
   
3. Print server sends job to local printer via LAN
   

Result = One WAN route and two LAN routes taken. WAN route compressed via ICA. 

Citrix recommend that you disable Direct connections to print servers if your Worker VMs and print servers are not in the same LAN. This is because in this situation the print job sent direct to the print server is not compressed. When the print job is routed via ICA it is compressed. If you decide to leave the Direct connections to print servers setting enabled the print job will and can take a fall-back route through the client device if needed. Fall-back will occur if the XenApp/XenDesktop session cannot contact the print server, the print server is on a different domain without a trust, or the native print driver is not available on the master image used by the XenApp/XenDesktop VMs. In this scenario the print job will then be routed from Worker VM to client, then from client to print server and finally to printer