The
Gigabit Ethernet standard (802.3z) should be officially approved in the first quarter of 1998. However, chip makers have already spun silicon, and equipment makers are turning out products based on the evolving standard. Lacking an approved standard, vendors must prove that the present standard is workable by doing interoperability tests.
Tests were done at Networld+Interop in Las Vegas in May by 28 vendors, among them Alteon Networks, Cisco Systems, Extreme Networks, Foundry Networks, Hewlett-Packard, IBM, Packet Engines, Rapid City Communications (acquired by Bay Networks in June), and 3Com. While the tests were encouraging, they were based on the D2 draft of the standard, which was frozen in March.
Gigabit Ethernet products that vendors are releasing will typically feature new silicon and firmware/software based on the draft that was frozen in July. Fall Networld+Interop in Atlanta will provide a public forum for tests of products based on the current draft. In July, the Gigabit Ethernet Allian
ce, representing the industry, announced the formation of a Gigabit Ethernet Consortium at the University of New Hampshire interoperability lab. At press time, the consortium was preparing for testing at the lab this fall.
Although many of them are sworn to secrecy by their testing partners, ask vendors whom they've tested with and what the results were. Knowing whom people are testing with is important. The more testing being done with the product you're considering, the better. Also, you may get a sense of the overall problems with Gigabit Ethernet interoperability and problems involving particular products.
Another useful strategy when it comes to interoperability: Buy multiple network components from the same vendor. For instance, Alteon sells both a Gigabit switch, the AceSwitch 110 (OEMed by Sun Microsystems as the SunSwitch), and Gigabit Ethernet network interface cards (NICs). You know they have been thoroughly tested together, so you have one less element of interoperability to worry abou
t.
Find Out What 100-Mbps Ethernet Will Do
You'll probably want to
compare
Gigabit Ethernet-based solutions with 100-Mbps Ethernet. Start now by looking at all the available 100-Mbps solutions.
If you will be testing Gigabit Ethernet cards for servers, know what you can do with multiple 100-Mbps Ethernet cards. To save slots in the server, consider solutions such as the quad-Fast Ethernet adapter from Sun, which gives you four 100-Mbps Ethernet ports on one card. With new trunking software from Sun, you'll be able to aggregate those four ports into one channel, though you'll still need a 100-Mbps switch port for each connection.
Similarly, Cisco Systems' Fast EtherChannel technology connects switches, routers, and servers with up to four 100- Mbps Ethernet links. You can aggregate the links or use them in redundant, parallel fashion. (Cisco will upgrade EtherChannel to support multiple Gigabit links in the future.)
Although price/performance is a big attr
action of Gigabit Ethernet, this is still a leading-edge technology. Adapter cards may cost $1200-$1500 or more. Switches may cost $2500-$3000 per Gigabit Ethernet port. Gigabit Ethernet often costs around four times more than 100-Mbps Ethernet. If you can get four times the performance, lowered management and equipment costs (e.g., fewer switch ports) may make the jump worthwhile.
What kind of performance improvement can you expect with Gigabit Ethernet? Due to the limitations of most of today's servers (e.g., CPU, bus, OS, and protocol stack), you will probably not get 10 times the application throughput you got with 100-Mbps Ethernet. A Gigabit Ethernet connection on a 7.88 SPECint95 Unix server can deliver three to five times more TCP throughput than 100-Mbps Ethernet before the server CPU runs out of cycles, according to tests done by Alteon.
Whether you are better off upgrading your server adapter to Gigabit Ethernet or going with a quad-Fast Ethernet card depends largely on the horsepower o
f the server, but also on the adapter you use. A high-end server will be able to take better advantage of the Gigabit card. Intelligent adapters, which off-load host processing functions such as TCP/IP checksum computation, can also maximize host CPU availability and increase throughput.
"Performance varies tremendously from server to server, and only testing can give you a realistic idea of what Gigabit Ethernet can really do for your applications," says Selina Lo, Alteon's vice president of product management.
When you start pushing 100-Mbps technology, testing may show that you don't have the traffic or the servers to justify Gigabit speeds. Again, multiple 100- Mbps links may be all you need for now. You can afford to wait while prices drop and the technology matures. On the other hand, with high-end servers, you may find that Gigabit Ethernet will speed things up, save you money, and simplify management, even if it delivers only half its nominal throughput.
Check Your Fiber
The
initial 802.3z standard prescribes a Fibre Channel physical layer, which means it requires fiber-optic cabling for cable runs that are longer than 25 meters. (Up to 25 meters, there is also a shielded-twisted-pair [STP] option, 1000Base-CX. An unshielded-twisted-pair [UTP] standard is still under development. Current UTP Gigabit Ethernet products are proprietary.)
With 62.5/125-micron multimode fiber, the most commonly installed fiber in the U.S. (and the fiber used in most FDDI installations), the 802.3z standard allows runs of up to 300 meters with a short-wavelength (e.g., 850 nanometers) 1000Base-SX transceiver or 550 meters with a long- wavelength (1300 nanometers) 1000Base-LX transceiver. Single-mode fiber, which is customarily used in conjunction with long-wavelength transceivers, is good for distances of 2 to 3 kilometers.
A potential problem arises because FDDI supports 2-kilometer runs on 62.5/125- micron multimode fiber. If you have fiber that was installed for FDDI, check the length o
f the runs. If they're in the 300- to 550-meter range, look for Gigabit Ethernet products that support long-wavelength transceivers. If the runs are over 550 meters, you must use single-mode fiber. If you're installing cabling now, include single-mode fiber for backbone links over 550 meters.
Plan to Recycle
What will you do with 100-Mbps backbone equipment when you replace it with Gigabit Ethernet? Plan redeployment now.
Perhaps you are still extending 100- Mbps Ethernet backbones today but expect to be deploying Gigabit Ethernet backbones in 12 to 18 months. After the coming of Gigabit, 100-Mbps Ethernet backbone switches may be reassigned to workgroup LANs.
Consider ATM Replacement
You're probably not in any rush to throw away ATM equipment that's doing an adequate job or to replace it with new and largely untested Gigabit Ethernet. However, there are arguments for migrating toward a purer Ethernet environment over the long run. Management will be simplified. Equipment t
hat supports only Ethernet will probably be much less expensive than equipment that supports ATM. In addition, translating Ethernet frames into ATM cells and back again increases the latency of the network (see the sidebar "Adding Up the Cell Tax").
However, there are good arguments for sticking with ATM in the long run, too. Carriers aren't offering Gigabit Ethernet WAN services yet. For now, ATM may be the best way to interface with the WAN (see the article "ATM's Shrinking Role").
Plan ATM Coexistence
If you have ATM, how are you going to integrate it with Gigabit Ethernet? The solution may involve switches, routers, multiplexers, and hubs that support both technologies.
Alteon's AceSwitch is a Gigabit Ethernet switch that will offer ATM links later this year. In addition to the ATM option, which is being jointly developed with NEC America, Alteon plans to support FDDI links. The switch offers eight half- or full-duplex 10/100 Ethernet ports, a full-duplex Gigabit Ethernet port,
and a PCI option port that you can currently configure as a second Gigabit Ethernet port. The PCI port will also support the ATM and FDDI options when they are released.
Find Management Tools
Management often lags behind when new technologies arrive, especially when they emerge as fast as Gigabit Ethernet has. Some current approaches may be hard-pressed to handle Gigabit Ethernet.
"Some tools don't work well at that speed," says Nate Walker, Cisco's product line manager for Gigabit Ethernet. "For example, an RMON probe that has to examine every packet may not be designed to do it at Gigabit speeds."
Many early products have only basic management capabilities, says Walker. "Most companies have thought about managing the physical and media access control (MAC) layers, but some have done very little about layer 3 and switching. That's one of the risks of looking at early products."
A third-party market for Gigabit Ethernet management is emerging, however. LANQuest is trying to fi
ll the gap with version 4.0 of Windows NT-based Net/WRx (pronounced "networks") traffic generation and analysis software. Net/WRx can generate and analyze not only Gigabit Ethernet but also ATM traffic. Its focus is capacity planning. By generating traffic using Net/WRx, the network designer can see how much more traffic the network can handle before users see a slowdown.
Learn About Routing Switches
With high-bandwidth technologies such as Gigabit Ethernet, routing functions are increasingly likely to create a bottleneck. There are half a dozen proposals for new interswitch protocols or modifications of the IP protocol that will give customers the performance enhancements that come with layer 2 switching, while retaining the services that routers perform, such as security, traffic prioritization, and policy management.
Initially, most of these proposals target ATM, including Ipsilon Networks' IP switching, Cisco's tag switching, and the ATM Forum's Multiprotocol Over ATM (MPOA), which t
he ATM Forum adopted as a standard in July. For Ethernet, Bay Networks' acquisition Rapid City Communications has implemented IP routing in silicon, permitting switch-speed routing without introducing any new protocols between switches.
The concept of a switch that performs optimized IP routing is one whose time has come. If nothing else, it lets you get the speed benefits of switching without having to totally rearchitect your IP addressing scheme, as you would have to if you flattened your network architecture by just substituting switches for routers.
Unfortunately, most of the layer 3 switching technologies are immature. Products also may lack essential features. A vendor may claim that its product is a switch router even if the only routing protocol it supports is RIP. That won't do for many customers.
To prepare for Gigabit Ethernet, customers need to educate themselves about the various layer 3 switching technologies. However, you may not be able to pick a clear winner, either in the
market in general or for your application.
You don't necessarily have to think in terms of picking one layer 3 switching technology, which today implies committing to a particular vendor, because standards are unfinished or too new. Nor is your only alternative avoiding all layer 3 switching schemes for the time being. Instead, you can buy only products that require no change in the routing protocol between switches.
It's also possible to deploy multiple layer 3 switching schemes. In that case, equipment running each scheme forms an
island
. Islands are connected by ordinary IP routing. You might use tag switching in an area of the network that is based primarily on Cisco routers, MPOA in an area that's dominated by Fore Systems' ATM switches, and ordinary IP for backbone extensions based on the Bay Networks F1200 Gigabit Ethernet switch (which was formerly Rapid City's flagship product).
Clearly, that adds management complexity, but it may make sense to go with the technology each ven
dor favors in areas of the network dominated by those vendors. There may be only minimal management integration between these parts of the network anyway.
Upgrade Servers
The first application that comes to mind for Gigabit Ethernet is often the backbone, where the increased bandwidth yields the most benefit for the most users. However, the backbone is also a single point of failure for the entire network. Servers can be a safer place for your first production rollouts of Gigabit Ethernet. To stay even further from the limelight, you could start by implementing Gigabit Ethernet only for server-to-server links, for functions such as backup, replication, shadowing, and synchronization, suggests Alteon's Lo. If anything goes wrong with these back-end server connections, it's less likely to have a direct and dramatic impact on users.
Server-to-server traffic is growing as fast if not faster than client/server traffic, according to Alteon. It also may be characterized by long frames that are w
ell suited to Gigabit Ethernet technology.
If you implement Gigabit links to today's PC servers, the servers will be much slower than the network. This is an opportunity to get better performance by upgrading servers. You may just want to install faster storage. Perhaps you want to consider the Fibre Channel-based disk interfaces on Compaq's newest ProLiant servers. You can also look for Gigabit Ethernet products that target servers, such as Alteon's NICs and switches. The NICs off-load protocol processing from servers; the switches offer features such as dual homing, extended frame size, and server-to-server load balancing, improving server reliability and performance.
However, even the fastest of today's PC servers can't get past the 1-Gbps data rate of the 32-bit PCI bus, which limits throughput on their network connections to perhaps 300-400 Mbps, according to Jeff Wilbur, director of hub products in Compaq's networking products division. That will change in the first half of next year, with a
64-bit PCI bus boasting a 4-Gbps data rate.
"Even Gigabit Ethernet might not be fast enough for servers with a 64-bit PCI bus," says Steven Moustakas, director of network products marketing for Sun. Sun plans to introduce servers with the new bus, though a date had not been announced at press time.
The bottom line: If you are going to give a server a Gigabit connection, consider upgrading the server to take advantage of it.
Accelerate IP Convergence
Many Gigabit Ethernet products are optimized for IP. For instance, Bay Networks' F1200 Gigabit Ethernet switch routes only IP. Other protocols, such as AppleTalk and IPX, are bridged. Because routing functions have been implemented in silicon, the F1200 can route just as fast as it can bridge. So you can get the management and security benefits of routing with no performance penalty -- but only if you feed the switch IP packets.
You can enable or disable IP routing on a per-port basis, so you can migrate to IP at your own pace. Ho
wever, you can prepare to take full advantage of the F1200's capabilities by converting as many networks to IP as possible. The F1200 has six slots, each of which can support either two Gigabit Ethernet ports or 16 10/100-Mbps Ethernet ports.
Where to Find
Alteon Networks
San Jose, CA
Phone: 888-258-3661
Phone: 408-360-5500
Internet:
http://www.alteon.com
Preparing for Gigabit Ethernet
