Chapter 10. Network Terminal Option (NTO) 227
As shown in Figure 10-1 on page 226, NTO running under NCP can take
non-SNA start-stop and non-SNA BSC input and convert it to a line-by-line mode
SNA stream. NTO support also includes ASCII-to-EBCDIC conversion. This
enables the non-SNA devices mentioned above to communicate with VTAM host
applications such as CICS and TSO. NTO is also used for SNA device
connections using NRF (discussed further in Chapter 11, “Network Routing
Facility (NRF)” on page 237). The SNA LU presented by NTO to the SNA
application on behalf of the non-SNA device is an LU Type 1 (IBM 3767). The
3767 is a keyboard and printer-type device. It does not have a display, so the
SNA application will be sending and receiving printer-like blocks of (often) 132
characters representing one line of print. In other words, the application treats
the terminal much more like a printer than, say, a 3270-type display.
For additional technical information about NTO function and setup, see Network
Terminal Option Planning, Migration, and Resource Definition (Release 11),
10.2 Functions and alternatives
NTO usage generally falls into one of the following three functional categories:
1. Connecting start-stop terminals to SNA mainframe applications
2. Connecting computer systems using non-SNA BSC RJE protocols to SNA
mainframe applications
3. Connecting non-SNA computer systems peer-to-peer using NTO with NRF
We discuss alternatives for each of these functions below.
10.2.1 Start-stop terminal connection to SNA host applications
Following are the alternatives for the NTO function that supports connecting
start-stop terminals to SNA mainframe applications.
Protocol conversion
As shown in Figure 10-2 on page 228, start-stop terminals can be supported by a
special-purpose hardware device that converts start-stop to SNA 3767 protocol.
The protocol conversion can also include ASCII-to-EBCDIC data stream
conversion. For example, the INETCO Connect product from INETCO Systems
provides this type of protocol conversion. See:
228 IBM Communication Controller Migration Guide
Figure 10-2 Start-stop terminal support
Using X.25-specific protocol conversion functions
Historically, X.25 support for start-stop terminal access to SNA host applications
has included PCNE functionality, which converts start-stop over X.25 into SNA
3767 (see also Chapter 6, “X.25 NCP Packet Switching Interface (NPSI)” on
page 187). This function is very similar to NTO conversion of start-stop directly to
SNA 3767. It is therefore possible that you could preserve your current
NTO-supported start-stop terminal to SNA host application environment by
adding an X.25 component to your network and replacing NTO with a
non-communication-controller-based program that includes PCNE support.
For example, both Comm-Pro Associates, Inc. ( and
Computer Associates ( appear to provide host-based programs
that include PCNE support. As illustrated in Figure 10-3 on page 229, you could
use an X.3 PAD function (available in RS/6000® software, in special-purpose
hardware devices, and in some routers) and connect start-stop terminals to a
router, such as those from Cisco Systems, Inc., that supports X.25 over TCP/IP
(XOT). The encapsulated start-stop traffic can then be transported across your
IP network and delivered through your host IP access infrastructure where the
Comm-Pro HNAS product, or the Computer Associates Unicenter TCPaccess
X.25 Server (formerly known as Solve:X.25) product, will provide PCNE support
to deliver the start-stop terminal traffic to VTAM applications as SNA 3767 LU1
devices (the same format used by NTO).
SNA Applications
SNA 3767
Chapter 10. Network Terminal Option (NTO) 229
Figure 10-3 Host XOT solution
If you are using Cisco routers, according to Cisco Systems, you can connect the
start-stop terminals directly into an asynchronous port on the router and the
router software can perform both the X.3 PAD function and the XOT
Both the hardware-based protocol conversion and the X.25 host software
protocol conversion can preserve your existing user devices and applications.
The hardware solution is probably the easiest. However, you might select the
X.25 solution if X.25 networking of your devices provides your organization with
cost or connectivity benefits.
10.2.2 BSC RJE connection to SNA host applications
BSC RJE is most often associated with IBM 2780 and 3780 device protocols.
While the original 2780 and 3780 devices were introduced in the late 1960s to
support remote job entry applications (such as submitting punched-card batch
programs for execution), the communication protocols that IBM developed for
them became the de facto standard for file transfer for much of the computing
industry and is still widely used today, almost 40 years later. BSC RJE protocols
are also used in some bank teller machines and store cash registers. Following
X.25 over TCP/IP
IP Network
Host XOT
SNA Applications
(OSA or
Host Access)

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