The latest hot topic – or nine-day wonder – in the computer industry is videoconferencing. The pitch is that the larger the distance over which people wish to communicate, the larger the advantage in terms of time and money – especially when expensive flights would otherwise be involved. Even over local area networks, the ability to see each other face to face is slowly being perceived as a logical progression. It seems like new technology now and demand is still scarce, but in a few years many network users will doubtless look back on simple text-based electronic mail with the same blank expression presently reserved for rotary telephones. There are, of course, a number of obstacles to be overcome for many companies before they can consider implementing real-time videoconferencing over a network. One of the largest of those obstacles would seem to be Ethernet’s lack of capacity.
Israeli
Ethernet delivers 10Mbits per second, which is only just enough to deliver moving images down the line when using very heavy compression. If users want to put other traffic on the network, (which is likely, after all), then it becomes pretty prohibitive. Some work is being conducted into increasing network capacity by some IEEE committees, which are researching 100Mbps networking systems. One or two products have already rolled off the line, but the selection is limited. Asychronous Transfer Mode communications is another answer, but again few products have made it to the market and users of existing networks wanting to switch to Asynchronous Mode may not be able to preserve their existing investment. One company that claims to have the answer is Lannet Data Communications Inc, an Israeli firm which is getting its hooks into the UK market with a vengeance. Simultaneously setting up a UK office and signing up with Sun Microsystems Inc’s SunConnect, the firm has also conducted a series of industry seminars championing its network switching system, which can be programmed to give priority to live video data and other time-critical communications. The Tel Aviv-based firm is an independant member of the RAD Group, a collection of Israeli companies that has been doing some interesting performance enhancement work with networks. Lannet’s answer is, it claims, less costly than fast Ethernet, FDDI or Asynchronous Transfer Mode. It also offers the advantage of dynamic switching and cuts down the network traffic by using what Lannet calls virtual networks. The company says that simply by using a switching device users can reduce the amount of congestion on a network because every device can talk to every other device directly through the hub rather than talking through other machines. It also enables users to do away with physical port switching, where cables must be pulled and reconnected to hook up workstations to different ports.
By Danny Bradbury
With static and dynamic switching, users can do it all from a central console. The LANswitch system runs various shared networks through a 1.28Gbps backbone (CI No 2,334); this is over 12 times the speed of the fast Ethernet methodologies proposed by members of the IEEE committee. The backbone can handle any combination of Ethernet, Fast Ethernet, Token Ring, Asynchronous Transfer Mode or FDDI communications, and can set up multiple parallel sessions for users to communicate. The LANswitch is self switching, so that it breaks up packets into different-sized sections which are a standard 64 bytes long for Ethernet. The method for transmitting the packets to the relevant workstation is proprietary. One added feature of the switch is that when it’s concentrating more than one client down a wire, (to a file server, for example), and the buffer starts to fill up, the switch can send a signal to the workstations concerned telling them to wait up while it clears its banks. This way, fewer if any packets get dropped. It also prioritises various different inputs, so that video servers can be allowed to pull rank over normal local area network clients, for example. The virtual network feature allows user
s on different networks to be segregated, for security reasons. Lannet claims that this enhances performance by localising network traffic where possible. The virtual network is a subset of the whole, such as a workgroup, where communication is largely with other machines in the workgroup. Any client-server information or communications from workgroup to workgroup still goes up the hierarchy.
Partnerships
With the dynamic switching feature, users can be shunted in and out of the virtual workgroups at will from one point of control. The LSE-108 feeds eight ports through one 10Mbps line into the high speed backbone, and costs $2,000. The LSE-208 feeds the eight ports into two 10Mbps lines onto the backbone and will set you back $3,000. The $6,000 LSE-808 connects eight ports of 10Mbps each into the backbone. The firm also produces LHB/LHS 100Mbps hub-to-hub and hub-to-video server modules. Lannet like many others – is touting the products as compatible with Asynchronous Transfer Mode, meaning that customers could buy the hubs now and then bolt Asynchronous Mode products into them in the future, as and when they appear. This is quite probably true, although it is worth pointing out that none of the customers that have bought the four-month-old boards have tried it yet. As for Lannet, it will have its Asynchronous Transfer Mode products out in the first quarter of 1995. So if, in these essentially pre-Asynchronous Mode times, people want something closer to bandwidth on demand, (up to 10Mbps for a single workstation), then perhaps they should be coming to Lannet and companies like it. Lannet itself seems to be going through an adjustment phase at present, with profits plummeting 69% to 1.1m. Maybe its existing partnerships with SunConnect, along with others from IBM Corp, Hewlett-Packard Co and Welfleet Communications Corp will help see it through what seems to be a difficult period, and help it take advantage of this window in the networking world.
