Review: Gigabit Ethernet switches

Remember when Fast Ethernet first strolled into your office? It quickly found a comfortable home on your net. But that was many years and many nodes ago. Now Gigabit Ethernet has arrived, whispering the same seductive promises. Should you believe it?

Surprisingly, yes. Our tests showed Gigabit Ethernet is capable of supporting much higher volumes of traffic than most of today's networks. And thanks to vendor adherence to standards, we found good interoperability among products.

Two of the switches we examined led the pack - the eight-Gigabit port, stackable Summit1 switch from Extreme Networks, and the seven-slot, modular P550 Cajun Switch from Prominet Corp., which is expandable to 12 gigabit ports. These are both solid, stable products that can add a substantial backbone bandwidth boost to any 10/100Base-T switched network.

Foundry Networks, Inc.'s four- to six-Gigabit port TurboIron Switch also turned out to be a solid and stable switch, but at the lower end of the performance and throughput scale. Bay Networks, Inc.'s eight-slot, modular Accelar 1200 Routing Switch, the first product from Bay's acquisition of Rapid City Communications last June, exhibited numerous problems. However, we were able to test only a late beta version of the switch - it was not scheduled to begin shipping until this month.

Still, Bay gets credit for showing up. A number of vendors that claimed to be shipping Gigabit Ethernet switches by the end of last year were invited to participate, but declined. In many cases, we learned that these products either were not yet shipping, despite vendor claims to the contrary, or were still in beta testing and were not ready for an independent evaluation. Those that declined our invitations include Acacia Networks, Inc., Gigalabs, Inc., NBase Communications, Packet Engines, Inc., Plaintree Systems, Inc., XLNT, Inc. and YAGO Systems, Inc.

With so many vendors rushing to play in this market, you might wonder if any have cut corners. Our testing showed Gigabit Ethernet products interoperate adequately. And some switching products available now are delivering unprecedented, and indeed incredible, switching capacities.

Standards stand up

Still, those issues didn't affect our ability to get everything connected and working together. All of the switches we tested worked compatibly with at least two other vendors' 1000Base-SX interfaces. They could exchange data, ranging from minimum to maximum packet sizes, at the full 1G-bit/sec rate in both directions across a multimode-fiber patch cable with dual-SC connectors at each end.

We also found good interoperability between network interface cards (NIC) and switches from different vendors. Packet Engines' 1000BaseSX NICs, also running in full-duplex mode, worked with each of the switches tested with no problems.

We even tried piecing together a series of multimode-fiber patch cables - a total of six 50-foot cables, concatenated with ST connectors - to see if that would make a difference. We wondered if the distance or the slight differences in different cable manufacturers' tolerances might cause problems at gigabit rates.

They didn't. Every packet sent at up to 1G bit/sec arrived intact.

Extreme-ly impressive

There's no 10/100Base-T support with the Summit1, however, and that's an annoyance. You need one of Extreme's Summit2 switches to connect via a 10/100 port. Without 10/100Base-T support, an administrator, who's typically equipped with a laptop and a 10/100 network interface, can't readily access the switch for in-band SNMP management. But this shortcoming, and the absence of support for port mirroring, are really the only two notable laments with Extreme's switch. Most everything else was done impressively.

>From a performance perspective, everything with the Summit1 switch works as expected. Switching four 1G-bit/sec packet streams through the Summit1 posed no problems. It seems likely that the switch's 17.5G-bit/sec backplane should handily accommodate all eight Gigabit Ethernet ports (for as much as 8G bit/sec of load) without strain. Indeed, it would seem that even if the number of Gigabit ports were doubled, most of the full-rate load probably still could be accommodated across this switch's backplane.

Besides rock-solid performance, other notable pluses with the switch include an impressive multilink load-sharing capability. This enables you to pass loads of multiple gigabits per second between two switches, bidirectionally and concurrently, over multiple, load-shared and fault-tolerant links. It also offers a switching-table capacity of up to 128,000 media access control (MAC) addresses, which is an order of magnitude more than many high-end 10/100Base-T switches. For large networks, this keeps known nodes from being dropped from the switch's memory on an oldest-first basis.

We tested Extreme's multilink load-sharing and failover capability, which enables up to four ports to be aggregated as a logical group, allowing 4G bit/sec of data traffic to be blasted between two switches. As with everything else with this switch, it worked impressively. If one of the links went down, its traffic was rerouted almost instantaneously to the other links in the group.

Extreme uses a proprietary protocol to implement load sharing and failover, as do Foundry and Prominet for equivalent load-sharing features they support. Bay doesn't yet support load sharing over multiple links.

The Extreme switch's considerable MAC-address capacity is diminished by half when IP routing is running. The same generally is true for other Gigabit Ethernet switches that also can do routing. This trade-off is understandable because some part of the memory allocated to the switching MAC-address table is then typically put to use storing IP routes.

Prominet: The strong, silent type

Whatever happens inside the P550 Cajun Switch, it definitely works. We experienced no hint of any problems with the mixed-packet-size load of four 1G-bit/sec traffic streams we delivered to the switch.

As with Bay's switch, the Prominet P550 Cajun Switch is based on a modular chassis with seven slots. We were happy to find a 10/100 port built into the control module that plugs into the first slot. There can be a second, redundant control module, or all six remaining slots can be used for interface modules - including a 20-port 10/100Base-T module.

A lot of desirable options still weren't available for the switch when we tested it in November. But some key ones - including 1000Base-LX support, IP routing and higher density, four-port Gigabit Ethernet modules (yielding a 24-gigabit-port switch capacity) - were expected to be delivered this month.

One flaw in Prominet's execution is its management software. The console's command-line interface is limited - you can't use it to retrieve any statistics, for example. And we found the main management interface, which is based on any frames-capable Web browser, to be kind of cheesy. We could not, for example, zero the statistics counters - this only can be done by cycling power to the switch - and statistics viewed through the Web browser aren't updated in real time.

The fact that some features weren't yet available and a less-than-optimal management interface don't detract too much from this switch, however. It's rock solid and an excellent performer. And a number of features that now are supported, such as its unique ability to let you tune the switch by allocating percentages of bandwidth to specific priorities and traffic types, are impressive. The fact that late last year Prominet was acquired by Lucent Technologies, Inc. also lends stability to this start-up vendor.

Foundry: A bit short on bandwidth

However, the total sustained switching throughput the TurboIron can handle is not quite 3G bit/sec, somewhat less than the switch's 4.2G-bit/sec backplane bandwidth. This is a problem because even in the switch's minimal configuration, as much as 4G bit/sec of packet traffic load could arrive at once via the system's four full-duplex gigabit ports. We clocked the switch's maximum throughput at about 2.9G bit/sec, with all traffic consisting of minimum-sized, 64-byte packets.

The throughput limit of Foundry's TurboIron Switch was our major concern. Another one, small by comparison, was that 10/100Base-T isn't supported anywhere in the switch. As with Extreme's Summit1, you need another switch supporting 10/100 ports and a gigabit uplink to gain in-band management access to the switch.

Foundry reportedly supports IP and IPX routing on the TurboIron Switch. However, to tap this capability you must load separate, extra-priced, operating software for the switch. The TurboIron Switches that Foundry sent us had only the base switching software loaded. The good news for Foundry, though, is that we consider this switch's management the best of all the switches we tested. The vendor's IronView software (Version 2.0), which runs only on Windows NT, provides intuitive, graphical management of the switch. Even virtual LAN setup and management is simple and fast.

Beta bugs bite Bay

The Accelar 1200 is an eight-slot chassis, which, with one or dual redundant control modules, leaves six slots for interface modules. The system wields a rated backplane switching capacity of 7.5G bit/sec in each direction, for a total of 15G bit/sec.

The Bay switch handled the four concurrent gigabit traffic streams we delivered to it. However, we noticed some loss with 1G-bit/sec traffic streams consisting of all large packets (1,518 bytes), on the order of about 2% of all packets.

We found, too, that broadcast packets would not be propagated properly by the switch if they came in at a high rate. When a stream of broadcast packets was delivered on one port at the full gigabit rate, only about half of these were retransmitted out on the switch's other ports. Bay claimed these were known problems with the beta software that would be fixed before final release.

Another major problem we encountered was with the Bay switch's Spanning Tree Protocol implementation. Increasingly, switches rely on Spanning Tree to prevent redundant data paths, or loops, from causing network crashes. Also, Spanning Tree provides a reliable, standard mechanism for automatically switching over from a primary path to a redundant path, if the primary path should go down. But Spanning Tree wasn't working right on the Bay switch, a problem the vendor acknowledged and said it was working on.

Bay offers a new Windows-based AccelarView package for managing this Gigabit Ethernet switch. It consists of separate Device Manager and VLAN Manager applications. We tested late beta Version 0.67.

As with the switch, we ran into a few problems with the management software. The graphical representation of the switch is super, and details are easily obtained by clicking on the switch part, or port, of interest. However, we couldn't get two key functions to work properly: the trap log part of Device Manager and the VLAN Manager.

Bay's Accelar 1200 has a lot of the makings of what could be a great switch. The price is disproportionately high, though, and Bay still needs to work out a few problems in the beta cycle before final release.

Wrapping up

Prominet's P550 Cajun Switch and Extreme's Summit1 switch led this pack. The Summit1, mainly because of its superior management software, edges out the competition and emerges as the Gigabit Ethernet switch to beat.