Although the news that L M Ericsson Telefon AB and Novell Inc are planning to develop multimedia workgroup products based on isochronous Ethernet (CI No 2,439) may do something to give the technology a higher profile, the National Semiconductor Corp-developed technology has suffered from the image of the poor relation compared with other next-generation local area network technologies. While Fast Ethernet, 100Base-VG AnyLAN and Asynchronous Transfer Mode have hogged the limelight over recent months, little has been heard from IsoEthernet since it was first announced in December 1992 (CI No 2,071). Despite this, progress has quietly been continuing. The technology, which is claimed to add 6.144Mbps of bandwidth to existing Ethernet local area networks – is expected to be ratified by the IEEE’s 802 plenary committee next month, and the first products were launched last month the by the Incite division of Dallas, Texas-based Intecom Inc. Isochronous Ethernet – which was formerly nicknamed IsoEnet and has now been mysteriously rechristened IsoEthernet – uses a different encoding scheme to that used by standard Ethernet.

50% efficiency

According to Mike Sodergren, strategic marketing director for National Semiconductor’s Interactive Multimedia Group, one major criterion for developing the Manchester scheme on which Ethernet is based, was to maximise the distances over which it could operate. However, the trade off with this is that the scheme finally adopted had only around a 50% efficiency rate. By modifying the Manchester scheme, said Sodergren, 80% efficiency can be achieved – yielding the extra 6.144Mbps of bandwidth. IsoEthernet has not received the same attention as Fast Ethernet and AnyLAN, Sodergren said, since it has largely been compared with the two 100Mbps technologies solely on speed. However he feels that such comparisons are unfair, since they ignore a couple of key advantages that IsoEthernet has over its faster rivals. Firstly, he said, IsoEthernet guarantees the delivery of time-sensitive traffic, where the 100Mbps technologies cannot: this is because the 6.144Mbps bandwidth that is freed up by the encoding scheme is allocated solely to time-sensitive traffic, whereas with AnyLAN and Fast Ethernet, such data is only prioritised, meaning that during times of heavy network usage, contention can still occur. This guaranteed delivery gives IsoEthernet what is potentially its greatest advantage over other technologies: use for speech traffic. The 6.144Mbps is divided up into 97 64Kbps data channels, 96 of which are ISDN-compatible bearer channels, with the 97th as the signalling D channel, allowing IsoEthernet networks to be connected to ISDN networks. While Sodergren recognises that IsoEthernet is essentially a niche technology – he admitted that the average guy is not going to need to consolidate speech, video and data over a single network – he nevertheless believes that for those people that need the integrated services, this is the only choice they have.

By Matthew Woollacott

For this reason, NatSemi says that it is focussing its efforts on the desktop conferencing, collaborative computing, and multimedia computer telephony integration markets. Paradoxically, IsoEthernet’s speech capability has in itself contributed to its low profile: while vendors of speech products have shown a lot of interest in the technology, support from the data communications community – notably hub manufacturers – has not been strong. Sodergren claimed not to be worried by this, but blamed it on the fact that a lot of these guys don’t understand telephony. Compounding this, he said, is the fact that there is a huge and booming data-only local network market and demand has not abated, providing little incentive for hub manufacturers to diversify into speech technologies. However, he added that he had been in contact with many of the major hub vendors and that, given time, they will climb on board. To increase take-up of the technology, a new industry forum to promote it will shortly be

announced, said Sodergren, and although he would not name names, he added that founder members will include more companies planning to implement it. While he said he didn’t expect to see any huge name hub guys in that first release, he added that hub vendors are among those who will be involved, along with coder-decoder and application companies. Indeed, with the ratification of the standard approaching, interest in IsoEthernet does seem to be increasing: Dialogic Corp is one of the newest supporters, and last month announced that, along with NatSemi and QuickNet Corp, it is planning joint development of a server adaptor board connecting its Signal Computing System Architecture computer telephony integration system with IsoEthernet. Similarly, other long-time supporters have been demonstrating IsoEthernet products in an effort to talk up the technology. At the Intermedia show in February, for example, Apple Computer Inc demonstrated its QuickTime Conferencing product operating over IsoEthernet, while AT&T Corp demonstrated IsoEthernet’s compatibility with its WorldWorx Network Services at the Computer Telephony Expo in Dallas: the demonstration involved video conferencing calls from the Dallas Convention Center to H.320-based equipment from Compression Labs Inc and PictureTel Corp in New Jersey, using an Ericsson IsoEthernet workgroup hub and 80486 personal computer. In terms of products, Sodergren says NatSemi has been shipping the silicon for hubs and interface boards in pre-production quantities for some time now, while it is also planning to develop network interface cards, including a NuBus board for the Apple Macintosh, and an AT board for iAPX86.

Call control

For its part, Incite announced three initial IsoEthernet products incorporating MPEG and H.320 image compression schemes for 30 frames per second video: the Multimedia Hub, which provides 12 IsoEthernet ports according to the company; Multimedia Manager server software, a Windows NT-based package designed to provide call control and the management of speech, data and video; and the WAN Hub for communication across the wide area. The WAN Hub is claimed to provide up to four interfaces for connection to Primary Rate ISDN services or to a PABX. The products are due to ship in July, and while specific pricing has yet to be decided, the company says that it will start at a cost of around $450 per port. For the future, Incite says that it is developing additional telephony interfaces for both digital and analogue telephones; an Asynchronous Transfer Mode backbone interface; and additional server software and desktop applications. No other details were forthcoming, but IsoEthernet may at last be on its way.