Cisco Systems Inc has added new router features claimed to improve the ability of users to integrate Systems Network Architecture traffic into their local network internetworks. Central to the new capabilities is a new custom queuing feature – said to incorporate both advanced prioritisation and bandwidth reservation – while the company has also added Dynamic Spanning Tree, SDLC broadcast capability, and two-way simultaneous SDLC transmission. Cisco says it is the first company to offer such a custom queuing feature, which is said to go beyond existing methods of prioritising Systems Network Architecture traffic by enabling users to define up to 10 queues, specifying a minimum bandwidth that each should be allocated: in this way, says the Menlo Park, California company, other traffic does not get bandwidth-starved at the expense of Systems Network Architecture traffic. The company also claims to have further refined its protocol prioritisation by differentiating between Systems Network Architecture and NetBIOS protocols since NetBIOS is used for non-time-critical applications such as file transfers, electronic mail and printing, and should therefore not have the same priority as Systems Network Architecture traffic. Also new on the company’s routers is the incorporation of Dynamic Spanning Tree in order to provide enhanced interoperability with IBM Corp source-route bridges, and reduced administration time by eliminating the need to configure the router statistically. It is also said to reduce recovery time after link failures by making reconfiguration unnecessary. The company has also added SDLC Broadcast to its existing SDLC support: it had already had the ability to make multiple physical SDLC lines appear as a single virtual multidrop line in order to simplify front-end processor configuration, but, with the new feature, if a front-end processor sends an SDLC Broadcast to one of these virtual multidrop lines, the router will now propogate that broadcast to each physical SDLC line. Similarly, the company has added two-way simultaneous transmission enabling both ends of an SDLC line to send or receive data condurrently, which the company claims will increase throughput and reduce response time. For example, the company says, in multidrop 3270 controller environments, the 3745 can be receiving data from one device, while polling others. Similarly, the company says, where an SDLC line connects two 3745 front-end processors, neither of these has to wait while the other transmits data. Custom queuing is to be shipped as standard on Cisco’s routers from next month, while the other new features will ship in the autumn as part of the company’s bridging software option. Notable by its absence from the new announcements is support for the proposed DLSw Data Link Switching standard, and Cisco is continuing with its policy of waiting until specification is ratified before offering any products based on it. According to Michael Zadikian, Cisco’s Systems Network Architecture product manager, the key issue is functionality, and Data Link Switching is more an interoperability standard: Zadikian still maintains that the standard is not yet finalised enough to base products on it, and says that those companies that are claiming to have an implementation – for example Proteon Systems Inc – are doing so more for marketing reasons than because they have conformant products. Zadikian says that the first draft of the standard will be completed late this year, with ratification scheduled for early 1995, and that Cisco’s implementation will follow shortly afterwards.
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