TCP/IP-to-SNA Connectivity from Network Software Associates
(Product Line Backgrounder -- October 19, 1992)

Many of our largest customers continue to express a need for products that
integrate different networking methodologies into a single enterprise
network. At Network Software Associates, we focus on delivering PC based
SNA services in a network and hardware independent fashion. We see the
growth in TCP/IP networks and the requirement for SNA and TCP/IP
integration as evidence that PC based SNA services should be adaptive to
the local or wide area networking methodology that makes sense to a given
customer.

TCP/IP gained popularity as a networking methodology in the department of
defense, commercial aerospace, and educational community. Its primary
function was to provide networking between UNIX systems. In the past five
years, commercial use of TCP/IP has spread quickly beyond aerospace into
other business sectors. And while once restricted to UNIX based systems,
TCP/IP is now widely available for PC-DOS, Windows, OS/2, and Macintosh
systems.

Hence we have noticed some very large users of SNA examining whether or how
to integrate growing TCP/IP user communities into an existing SNA
enterprise network. The alternatives can seem rather complex, especially
since they involve a mixture of both SNA and internetworking concepts.

Customer Alternatives

One of the alternatives is to allow for the growth and management of dual
networks. Customers may not see a need for users in the TCP/IP network to
access SNA hosts. They may not find any efficacy in building and managing
a single enterprise network. Or the function of building and managing
networks is handled by two different organizations: one is historically
committed to SNA and the other to TCP/IP. This situation is reflected in
the diagram on the following page.

A second alternative is to pursue the integration of both networks into a
single TCP/IP based environment. Such an approach may involve
encapsulating (or tunneling) SNA/SDLC traffic within IP. This
configuration (or a variation on it for 802.2) is currently recommended by
various bridge and router vendors.

The SNA/SDLC encapsulation approach has the benefit of eliminating the need
for dual networks. However, it can produce a high amount of WAN overhead
(in the form of SDLC traffic) while slowing down the performance of IP
routers.

A third alternative involves the use of host based Telnet and PC based
TN3270 emulators. This is the most common approach used to provide TCP/IP
users with 3270 host access. The upper layers of the 3270/LU 2 protocol
are encapsulated within IP, providing PC users with basic 3270 display
emulation over the IP network.

The use of TN 3270 and Telnet allows a partial integration of SNA and
TCP/IP. An IBM host will appear as an IP address to the TN 3270 user. PCs
can access 3270 display applications. However, some critical network and
end user functions are not supported by Telnet and TN 3270. These include
NetView management, printer datastreams (LU 1 and LU 3), APPC protocol and
applications, HLLAPI applications, standard file transfer (IND$FLE), and
certain 3270 display attributes. In addition, the host site must take on
the burden of installing and maintaining the Telnet server application.
Telnet and TN 3270 as a solution for TCP/IP to SNA integration can
severely limit the scope of SNA services for the PC user.

TCP/IP-to-SNA Solutions From Network Software Associates

As specialists in network independent SNA connectivity for PCs, we have
many years of experience with an architecture that is ideally suited for
TCP/lP-to-SNA integration. Our first offering consists of TCP/IP drivers
for our AdaptSNA LAN Gateway and Elite client products. These drivers are
provided for popular off-the-shelf, third party TCP/IP products (such as
Novell's LAN Workplace and SUN's PC-NFS) to provide a complete set of SNA
services for the PC user.

SNA services provided to the PC user in the configuration above are no
different than the services that an 802.2 or coax connected user can get
from NSA's Elite emulators. HLLAPI applications run unaffected. LU1 and LU
3 printer emulation is fully supported. All 3270 display attributes and
keyboard functions work properly. And users can transfer files to and from
the host using the industry standard IND$FILE program.

IBM and third-party developers are offering an increasing number of APPC
applications for the mainframe environment. With the NSA solution, these
APPC applications can run across the IP backbone to PCs running NSA
software. PCs can even run the APPC applications concurrently with 3270
emulation.

The NSA solution also provides important network management capabilities.
Through new support of the NetView Response Time Monitor (RTM), network
managers for the first time can measure the end-to-end network performance
of 3270 sessions running across the IP backbone from a central NetView
console.

One of the most substantial benefits offered by the NSA solution is its
negligible impact on backone overhead and router performance. Each IP
packet sent from the Elite emulators to the AdaptSNA LAN Gateway only
contains SNA data. Hence the IP routers forward standard IP packets with
SNA data across the WAN. And there is no encapsulation of link level SNA
protocols such as SDLC or 802.2.

Future NSA Efforts

At NSA we have aggressive plans to expand our support of PC based SNA
services for the multivendor LAN environment. We are currently engaged
with several industry groups in the definition and development of an SNA
Management Information Base (MIB) that will support Simple Network
Management Protocol (SNMP) management of SNA devices. We are also working
on extensions to our TCP/IP drivers that will provide support for several
industry leading gateway and controller products.

NSA plans to continue the focus on meeting the evolving need of enterprise
networking customers. Increasingly we find these needs embracing open,
multivendor, heterogeneous systems. We expect to continue to play a
leading role in the development of solutions that make SNA more open and
more flexible.

The company is headquartered at 39 Argonaut, Laguna Hills, CA 92656. Phone:
(714) 768-4013 or (800) 352-3270. Federal Systems Division: (703)
875-0444

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