Electronic Design

WAN, MAN, LAN, PAN, And SAN: Evolution, Not Revolution

During the past several years of economic downturn, changes in networking technology have been incremental rather than major.

During the past several years of economic downturn, changes in networking technology have been incremental rather than major. Progress has been made by upgrading and fine-tuning the existing technologies or by applying existing technology to new applications. And it's pretty clear that we'll stay on that path for the immediate future.

The undisputed major trend in networking, as expected, is higher speeds. The increased use of fiber-optic links to get that extra speed supports that trend. High-speed digital chips with lower power consumption continue to flow out of the semiconductor companies, while optical component manufacturers who have survived the turmoil of the past years have produced improved higher-speed, multiwavelength parts including affordable tunable lasers.

Each of the popular communications networking systems has a unique place in the market today.

WANs
Wide-area networks mean Sonet and ATM. These long-haul rings and backbones are universally optical. The typical upper speed is 2.5 Gbits/s (OC-48). Today, with the telecom industry in the dumps and overcapacity the norm, carriers aren't spending the bucks to expand their networks. Instead, they're upgrading what they have. While 10-Gbit/s Sonet (OC-192) equipment is available, few are opting for it in any volume. Some work on 40-Gbit/s Sonet (OC-768) components continues in the background, but no commercial systems are yet available. It will take a return of the good times to see 10-Gbit/s systems widely adopted and 40-Gbit/s parts come to market. It will no doubt be another year or so before the good times roll again. In the meantime, software technologies like multiprotocol label switching (MPLS) will greatly improve the use of existing WANs. Another growth area is the implementation of security measures. Security is becoming easier with the new, faster encryption chips. Yet security is still mostly a software issue.

MANs
Metropolitan-area (metro) networks are doing only slightly better. While there are pockets of new MANs, mostly everyone is still hunkering down and waiting for better conditions. In the past, most MANs used Sonet. MANs implemented during this downturn are cheaper and made with 1-Gbit Ethernet (1GE) or 10-Gbit Ethernet (10GE). They're inexpensive and ideal for extending or interconnecting existing Ethernet LANs because they require no protocol conversion. The 1GE systems predominate, but 10GE systems are beginning to show up as prices of optical components begin to decline.

While quality of service (QoS) and compatibility with WANs and other MANs are issues, these are being overcome with new technologies and standards like resilient packet ring (RPR), which promises to improve the linkage of Ethernet and Sonet systems. With suitable changes and additions to the existing standards, the 1GE and 10GE systems may have won this space permanently over more complex and expensive Sonet systems.

LANs
Local-area networks continue to use the traditional 10/100-Mbit/s Ethernet over CAT5. 1GE over copper (CAT5E or CAT6) is slowly making its way into the LAN arena as 10/100/1000-Mbit/s network interfaces in PCs become standard and as 1GE switches decline in price. The 1GE connections are still mainly backbones for larger LANs, but 1GE to the desktop is increasing with the availability of 1GE over copper. All of this is a very mature business with only marginal growth expected.

One hot area, though, is power over Ethernet. This upcoming IEEE Ethernet standard (802.3af) defines how to supply dc power over Ethernet twisted pair to power voice-over-IP phones and wireless-LAN hot spots. The IEEE has established a working group to transmit 10 Gbits/s over copper by extending the XAUI interface over coax cable. A 10GBaseT study group has also been set up to investigate 10-Gbit/s Ethernet over twisted pair or other copper lines.

The major growth sector is wireless. Many organizations are adopting wireless LANs (IEEE 802.11b) to expand their networks and to provide mobile capability within the organization. While security is still an issue, that problem is being solved in the newer versions of the equipment. The current 11-Mbit/s speed is gradually being replaced in some cases by 802.11a systems that run to 54 Mbits/s. As the new 802.11g products become available, look for them to become the primary WLAN products in the enterprise. (For more on WLANs, see "Wireless LANs And Cell Phones Lead The Way," this issue, p. 65.)

PANs
Personal-area networks are a tiny niche in the overall networking world. They use wireless technology. Infrared (IR) systems started the trend with interfaces in laptops and PDAs. But they never became popular. The current PANs are mostly Bluetooth. While Bluetooth chips are now much lower in price, they have not been widely employed in PANs. Some laptops and PDAs have them, but the biggest use of Bluetooth so far has been in cell phones for cordless headsets. Currently, PANs seem to be a networking segment that is going nowhere. It is the classical technology looking for an application. There may never be a killer app beyond the cordless headset. PANs are expected to get a major boost in speed as faster Bluetooth chips eventually become available.

But there is a forthcoming bright spot in PANs: the ZigBee standard for short-range, low-speed ad hoc networks for monitoring and control operations. ZigBee may eat into the Bluetooth space, but in reality it is in a niche of its own. Silicon from several vendors is expected later this year.

The biggest boost in PANs, however, may come from the ultra-wideband (UWB) products that should become available later this year. Speeds of greater than 100 Mbits/s will be available for short ranges (up to 10 m). But again, what is the application? UWB PANs will no doubt find their greatest potential in the home for interconnecting video equipment.

SANs
Perhaps the brightest spot in networking is storage-area networks. These interconnections link large disk arrays to servers and other systems. The reigning technology is Fibre Channel (FC), an optical ring configuration that has become the de facto standard. FC continues to get faster as the newer versions of the standard have increased rates to 1.0625 Mbits/s and 2.125 Gbits/s, making this system even more desirable today. Faster 4G and 10G systems are in the works.

FC manufacturers have also felt increasing competition from a serial version of the popular SCSI parallel interface used for years to connect disk arrays. Known as Internet SCSI or iSCSI, this networking standard encapsulates SCSI commands into TCP and then transmits them over IP. This makes Ethernet a viable connection to the disk arrays. Both 1GE and 10GE systems are becoming available, and they are generally less expensive than FC systems because they use standard Ethernet hardware. But the FC vendors have joined the quest for lower costs and they will no doubt continue to dominate this field despite the rise of iSCSI.

In addition, there are efforts to transmit FC over IP. FCIP is Fibre Channel over TCP/IP that tunnels FC over existing IP networks. Another effort, iFCP, supports FC in Layer 4 TCP/IP transactions.

NETWORKED FUTURE
The general movement to network everything will continue. Manufacturing plants and factories are adopting Ethernet for monitoring and control. Most of the electronic functions within cars and trucks are being networked. And, home networks are growing in popularity. Further, work is being accomplished remotely more and more with Internet connections.

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