2008/6/26 Chris Mason <[EMAIL PROTECTED]>: > So, in order to answer the original question "So who is right? Can I open a TN > session to a host in another domain???" restated accurately as "Can I create a > TELNET connection using 3270 data stream from one Communications Server > IP component - using the TSO TELNET command - over an IP network to > another Communications Server IP component - using the TN3270 server?" the > answer is "Yes".
Well, the restatement is still rather overspecified. TN3270 is a protocol, not a particular set of client and server software, originally rather loosely specified, which has been more clearly and accurately defined over time in RFCs 1647 and 2355. The platforms the client and server run on have no real bearing on use of the protocol, and there are both clients and servers for System z and other platforms. Obviously TN3270 servers for non z platforms are fairly rare, since there is not often native application support for 3270 data streams, but they do exist as part of commercial products. The System z TN3270 clients for both z/OS and z/VM are a little unusual in two respects: They are both called TELNET rather than TN3270, though they behave about like any other TN3270 client; Since they are invoked from a terminal session that is already logged in to a 3270, they don't have to remap keyboard input and screen output to a foreign platform such as dumb ASCII datastreams or the Windows presentation interface; rather, they offer a "passthrough" or "transparent" mode, and rely on the existing 3270 session to understand the EBCDIC datastream with only the minimal unwrapping of the TN3270 protocol that is needed. There is also no need to bring SNA into the picture, except for those specifically SNA functions defined in newer versions of the protocol. Although the z/OS implementation of a TN3270 server does map the TN3270 session to an SNA one, this is not logically necessary. The z/VM server uses SNA, oddly enough, only for line mode, but uses VM's Logical Devices for 3270 mode. It really comes down to the terminal interface that the application program is expecting. On z/OS (and maybe VSE, which I know nothing about), SNA apps such as TSO and CICS are common; on VM, apps typically use the low-level DIAGNOSE interface or layered software that ultimately drives what it perceives to be a local, channel-attached 3270 device. (Of course on VM, that "app" could be an entire guest operating system.) On a non z platform, the server application interface is generally proprietary to the software vendor. Tony H. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
