The only disadvantage to using a direct TCP/IP connection is that there are a few printers that do not support this type of connection.
SENDING PRINT FILES USING OTHER PROTOCOLS
Other protocols can be used to deliver print jobs to remote TCP/IP hosts. Some vendors have implemented their own protocols for print file delivery to print servers on other platforms. Control information to describe the file and how it should be processed can be sent, along with the print file. In some cases, the data can be compressed and encrypted.
As an alternative, e-mail protocols can be used to deliver print files to e-mail recipients who can then decide whether it is necessary to print the file. Files that were manually decollated and mailed to various sites can be automatically sent by e-mail, saving time and printing costs. In many cases, the recipient only needs to browse the data and no printing is required.
SECURE PRINT FILE DELIVERY
One of the concerns for TCP/IP printing is that the print file may flow over public networks and might be captured and read by someone other than the intended recipient. Some print servers and printers support encryption and decryption of print files, which can eliminate this problem. The sender encrypts the print file using a special algorithm and the encryption key that is defined at the printer. The receiving printer decrypts the print file before printing.
TCP/IP PRINTING IN THE z/OS ENVIRONMENT
The print servers on z/OS must be able to send to TCP/IP devices print files that were originally meant for SNA printers, including normal line data (EBCDIC) and Advanced Function Presentation (AFP) files. In some cases, the files must be converted to other printer languages (e.g., PCL or IPDS) and delivered to TCP/IP printers.
Special problems arise when a mainframe application creates print files designed for a VTAM printer, but which now should be delivered to a printer on the TCP/IP network. For example, it may be necessary to redirect a report to a TCP/IP device that CICS or IMS is currently sending to a VTAM-controlled printer. There are print server applications available which emulate a VTAM printer to receive a report and modify the print file so that the report can be queued for delivery to a TCP/IP device. Functions performed could include data translation, processing form feed, line feed and carriage restore characters, understanding commands for vertical or horizontal formatting, handling transparency sequences (for embedded printer commands that are already ASCII), etc.
Tracking files received from other TCP/IP hosts can also be a requirement. Operators need to be able to track files that are queued for a TCP/IP printer to determine the current print status. When a user sends a print file to the z/OS system, that user would like to be able to determine if the file is still queued, is currently printing, or has been printed successfully. In some cases, the person who created the report would like to be notified when the report has printed or when an error has occurred. Print servers running in the z/OS environment should support these tracking options.
The z/OS system is a very large and sophisticated TCP/IP host. Therefore, print servers running in the z/OS environment must be able to handle large volumes of print data as well as large numbers of printers. There may be thousands of printers to support and millions of lines of print data. Accounting for the printing of these reports to bill the appropriate users may be a requirement. In order to quickly diagnose problems with printers in the TCP/IP network, a print server should incorporate a sophisticated monitor and control facility to allow operators and end users to respond to printing problems as they occur.
In order to provide TCP/IP printing in a z/OS environment, you need the flexibility to be able to send print files using different protocols, and in the proper printer languages and character sets. This may mean datastream conversion as well as character-set translation. Your print server should be able to ensure that each file has been received and printed successfully, has the capability to track print files that are queued for a printer, and can monitor the status of each printer. In addition, your print server should provide sophisticated error recovery and be able to handle the large number of print files and TCP/IP printers that the enterprise requires.
TCP/IP printing protocols have evolved over the last decade and many changes will be coming in the next few years. A print server running in the z/OS environment should support the older TCP/IP protocols while embracing any recently developed protocols that could improve performance, reliability, or security. Z