SAN JOSE, Calif., Nov. 14, 1994 -- A new software architecture thatmakes accessing IBM SNA applications over routed internetworks morescalable and flexible -- combining the benefits of the native SNA interfaceat end stations and mainframes with those of TCP/IPacross the network backbone -- has been introduced by Cisco Systems.
Cisco's Native Client Interface Architecture (NCIA) extends the use ofthe TCP/IP protocol all the way to the SNA end station. Because of thewide range of media supported by TCP/IP, including dial-up telephone linesfor remotely located users, this makes multiprotocol access to corporatebackbone networks much more flexible for SNA users.
Designed to be implemented in SNA host access client software products,NCIA will initially be brought to market as part of
In conjunction with NCIA, Cisco has introduced a new software feature,DownstreamPhysical Unit (DSPU) concentration, which will allow Ciscorouters to assume the physical unit (PU) concentration functions normallyperformed by an SNA-LAN gateway.
Combining the Best of SNA, TCP/IP
NCIA works by enabling SNA end stations (e.g., PCs or workstations) toencapsulate SNA traffic in TCP/IP, rather than requiring the traffic totravel to the router before being encapsulated. Today Cisco Remote SourceRoute Bridging (RSRB) encapsulation is used; DLSw+encapsulation (see accompanying release) will be supported in thefuture.Nick Francis, Cisco director of IBM internetworking, said, "As usersmigrate to client-server routed internetworks, it's vital that they retainaccess to their legacy SNA applications. In the past there were threeoptions: install a separate and costly SNA link to the mainframe; use astand-alone SNA gateway device, which complicated network design andmanagement and increased cost; or run tn3270 emulation, which compromisedsuch functions as printer support and still required a gateway whichlimited scalability.
"With NCIA, the SNA end station connects directly to the multiprotocolnetwork, and TCP/IP takes the SNA traffic all the way from the end stationto the mainframe-site router. Because SNA end stations have full physicalunit status and can communicate directly over TCP/IP, no SNA-LAN gateway isneeded. The user gets the best of all worlds: the full richness of thenative SNA interface in the end station, efficient, gateway-less, scalablemainframe SNA access, and the flexibility and performance of TCP/IP acrossthe entire enterprise backbone."
Because NCIA provides a common connection mechanism and look-and-feelfor accessing the mainframe -- whether from local or remote sites -- it isespecially effective for remote users connected via dial-up telephonelines, who previously had no practical means of dialing into an integratedLAN/SNA network. These users can now dial in using TCP/IP andindustry-standard serial protocols such as PPP (Point-to-Point Protocol),and have full native multiprotocol applications access over the sameconnection.
DSPU Concentration: Optimizing SNA Host Access
Cisco also has introduced Downstream Physical Unit (DSPU)concentration, to be implemented as a standard software feature of Cisco'sInternetwork OperatingSystem in first quarter 1995. DSPU can be usedalong with, or independently of, the NCIA architecture. DSPU concentratesmultiple downstream PUs and their associated logical units (LUs), providinga single PU image to the host. In addition to significantly reducing WANoverhead, this simplifies host configuration, allowing devices to be movedwithout changing host definitions."DSPU is ideal for users accustomed to defining all of their endstations as distinct full-stack SNA physical units in the mainframetables," Francis said, "because it eliminates the need for the stand-alonegateway that would ordinarily be installed just to perform theconcentration function. DSPU can be especially effective when used inconjunction with the NCIA architecture, in which each end station acts as afull PU."
DSPU concentration also facilitates fast recovery from FEP failuresbecause it reduces the number of routes that must be discovered and thenumber of mainframe sessions that must be reestablished before SNA sessionsare recovered. With DSPU, only one route is discovered and onePU-to-mainframe session is reestablished for all of the downstream SNAsessions.
DSPU concentration will be a standard no-extra-cost feature in Cisco'sEnterprise IOS feature set on the 2500 series,4000 series andAccessPro PCCard,and in the bridging software option on the 7000 series andAGS+.
Cisco Systems,Inc., headquartered in San Jose, Calif., is the leadingglobal supplier of internetworkingproducts, including routers, bridges,workgroup systems, ATM and Ethernet switches, dial-up access servers,software routers and router management software. These products are used tobuild enterprise-wide internetworks linking an unlimited number ofgeographically dispersed LANs, WANs and IBM SNA networks. Cisco'sInternetwork Operating System (IOS) technology, found in more than 250,000installed Cisco units and in the products of over 20 partners, is the defacto industry standard for data transmission. In the U.S., Cisco istraded over the counter under the Nasdaq symbol CSCO. A member of the S&P500 and Fortune 500, Cisco in fiscal 1994 logged sales of $1.2 billion.
Posted: Nov 14 11:15:29 1994
