Switching Hubs: The New Network Frontier

by Art Wittmann and Robert J. Kohlhepp

Even since last September, when we told you switching hubs offered more bandwidth at lower prices, with crucial infrastructure features (see "The Switching Hub Era Begins!" September 1, 1994, page 62), we've seen fasteraction in this market segment than a busy Ethernet segment. So we asked vendors to provide us with products in what we think is the most promising area: Those with at least eight switched ports and at least one high-speed port running at 100 Mbps or faster. Thirteen vendors came through, and we tested those offerings in our University of Wisconsin lab.

Because of the variety of products, we broke them into two subcategories: fixed configuration hubs and stackable or chassis-based systems. The fixed configuration systems included products from Grand Junction, PlainTree, SysKonnect (an OEM of Plain Tree), Network Peripherals, NetWorth (an OEM of Network Peripherals) and Cisco. Slotted or stackable systems came from UB Networks, Chipcom, LANNET, 3Com, Digital Equipment Corp., Alantec and SMC. SynOptics and Cabletron were invited but did not provide test units.

We tested for functionality and interoperability, and considered flexibility, cost of ownership and ease of operation. We did not test for performance. Next month we will publish Scott Bradner's router and bridge performance test results, where most of these systems will have been tested exhaustively.

The fixed configuration systems all worked extremely well right out of the box. Cisco has done a wonderful job integrating the most useful features into its Catalyst hub. For chassis-based systems, Chipcom and 3Com have extremely well-built systems that will meet the needs of most corporate users. But Alantec's PowerHub has flexibility, expandability and a feature-set that makes it too hard to pass up.

How We Tested

With the exception of the Grand Junction FastSwitch, all of the hubs use FDDI for their high-speed port. So we tested interoperability by building an FDDI ring with each of the systems and some servers. Our servers consisted of Sun Unix servers configured for NFS and NetWare servers configured to support IPX and AppleTalk. Our FDDI ring worked immediately and we encountered no problems with any of the systems on the FDDI ring.

For Grand Junction and LANNET, we used only a Novell server for testing. While LANNET supplied both FDDI and Fast Ethernet interfaces, they asked that we only test the Fast Ethernet interface. Since Fast Ethernet uses the same frame type as standard Ethernet, there is less concern for protocol handling problems.

We also asked the vendors to supply network management applications for each of their products. For this test, we accepted software that ran on either HP OpenView for Windows, SunNet Manager on a SparcStation, or standalone on Windows or SparcStation machines.

FIXED CONFIGURATION SYSTEMS

The Cisco Catalyst Workgroup Switch

For a small switch, the Catalyst really packs some great features. You can get the 8-port unit with or without an FDDI card, and setup is fairly straightforward. Those who are used to configuring Cisco routers will find configuration very familiar. We had no problems getting the system up and running, using the serial interface to set an IP number and then finishing the configuration via telnet. Configuration can also be done with the workgroup director -- Cisco's SNMP software.

Cisco's heritage in the router market clearly shows. The Catalyst supports filters based on protocols, vendor-specific MAC addresses and bit pat-

terns. It supports broadcast limiting and suppression as well as IP Multicasts, IP route groups and bridge groups. In our tests, the Catalyst handled AppleTalk, TCP/IP and IPX without a problem.

IP route groups, and bridge groups are much like virtual LANs. Ports can be arbitrarily segregated so that broadcasts and multicasts that originate on one port will only be replicated to other ports within its router/bridge group. The Catalyst's ability to route IP between interfaces is also unique, and of course the catalyst was able to fragment IP packets.

Finally, the Catalyst's embedded RMON agent tracks the activity on each port. We've long thought that it would be best to implement RMON this way and Cisco is the first to do it.

PlainTree WaveSwitch 100/SysKonnect SK-NETSwitch 6616

The WaveSwitch 100 is a 16-port 10BASE-T unit that can support a variety of 100-Mbps interfaces. The unit is also licensed by SysKonnect, which contributed to the design and firmware used on the FDDI interface. The system is simple -- particularly when compared to the Catalyst -- yet still very usable.

We had no trouble configuring the system, which really amounted to little more than setting an IP number. The WaveSwitch is a simple bridge and supports no routing. It does support IP fragmentation.

It was simple to check our WaveSwitch's status with either a serial connection or using telnet. Neither PlainTree nor SysKonnect have a specific GUI-based configuration utility, relying instead on software like Castle Rock Computing's SNMPc -- a product we find unusable, since it requires the use of an external parallel port key.

The WaveSwitch is unique in its support of 100-Mbps technologies, supporting FDDI, 100BASE-T (Fast Ethernet), 100VG-anyLAN and PlainTree's proprietary WaveBus. Each is priced differently and can be added to the basic 16-port system. At just under $14,500, our unit was equipped with a dual-attach FDDI module. That price makes the system quite economical.

Network Peripherals EIFO Client/Server Switching Hub/NetWorth PowerPipes

The EIFO contains 12 Ethernet ports and one FDDI port. It can also accommodate a 4-port FDDI concentrator with either fiber or twisted-pair ports. NetWorth licenses the EIFO and offers some different management options as well as an extra-cost NetWare Loadable Module (NLM) that is supposed to improve performance by negotiating flow control between the switch and a NetWare server.

The EIFO was intended for the NetWare environment and doesn't support IP fragmentation. We found that while IPX and AppleShare worked well through the switch, NFS traffic would not flow. You can change the maximum transmission unit (MTU) on NFS servers from FDDI's default of 4,500 bytes to Ethernet's MTU of 1,500 bytes. But this will adversely affect FDDI-to-FDDI traffic.

Configuring the EIFO is easy. Its menu-driven interface can be accessed via serial port or Telnet, and the unit can also be configured from SNMP. Unlike some of the other fixed configuration systems, Network Peripherals has a very nice application that integrates into SunNet Manager.

The EIFO is the best bargain of the FDDI-to-Ethernet fixed configuration systems. At $8,995 for 12 Ethernet ports and a dual-attached FDDI interface, the EIFO is about $150 per port cheaper than any others, except Grand Junction.

The Grand Junction FastSwitch 10/100AG

The FastSwitch 10/100 is a unique system. It supports only one Mac address on each of its 25 Ethernet ports. Depending on the version you buy, the FastSwitch also offers private and shared Fast Ethernet ports. It may seem that the ability to attach only one device per port is restrictive, but the savings could actually make you think twice! Each Ethernet port is priced at roughly $300, or about half the price of other products. The FastSwitch also comes with a substantial three-year warranty.

The Fast Ethernet ports are also a bargain, running from $500 to $1,000 per port. Since the high-speed media are all Fast Ethernet, which uses the same framing as standard Ethernet, there's no concern wit h IP fragmentation or frame translation. However, it may be hard to find a router that can accommodate a Fast Ethernet connection. We had no problems running IPX or AppleShare through the FastSwitch. We did not test TCP/IP because we did not have an SBus Fast Ethernet board for our Sun.

Configuring the FastSwitch is easy, using a menu-driven system accessed from a serial port. You can configure the Fast Switch for three different switching modes, including cut-through (switch as soon as the destination address is known), store and forward (store the entire packet before forwarding) and fragment free mode. In fragment free mode, the switch will read at least 64 bytes of the packet before beginning to transmit data. Since the collision window for Ethernet is less than 64 bytes, this virtually assures that all transmitted packets will be good packets. These modes are only useful when data travels from standard Ethernet to standard Ethernet, or from Fast Ethernet to Fast Ethernet.

CHASSIS BASED SYSTEMS

The Alantec PowerHub 3150

Alantec's newest switching hub-the 3150-comes in at $15,000. Alantec's 3000 and 5000 series use a shared memory architecture, while the 7000 series uses a packet channel and is a truly stackable system with exchangeable backplanes and sheet metal cases.

For management, Alantec supports SunNet Manager, HP OpenView and IBM NetView/6000. Alantec also offers its PowerSight software as a standalone application that runs on Unix workstations from all three companies. Alantec's management software is very functional and usable. Best of all, the PowerHub can also be fully configured from a serial port and via telnet.

Perhaps PowerHub's most outstanding features are its support for routing, virtual LANs and bridging. For routing, the PowerHub supports IP-including IP multicast-IPX, DECnet and AppleTalk, and it does so with modules that are fully integrated into the system. We tested NFS, IPX and AppleShare on the system and found no problems. The 400-Mbps backplane o f the 3000and 5000 is fine for most organizations; the 3.2-Gbps backplane of the 7000 chassis can accommodate as many as 16 FDDI interfaces, which should satisfy the most bandwidth-hungry environment.

In the past, the PowerHub was out of the reach of most budgets, but the 3150 was one of the more cost-effective hubs we tested.

3Com LANplex 6004

The LANplex 6000 series design boasts a backplane that has a sustained throughput of 3.5 Gbps. But that backplane isn't used with the current generation of cards. Rather, you can create up to three individual 100-Mbps FDDI loops. 3Com says that an FDDI switching module due out toward the end of 1995 will take advantage of the high-speed bus.

LANplex boasts sophisticated virtual LAN and broadcast control technology. Currently, the LANplex can route IP and is scheduled to route IPX and AppleTalk by July. A Token-Ring module is scheduled for later this year.

LANplex was one of the easier systems to configure, partially because of its front-panel LCD display. 3Com shipped its management software for SunNet Manager, for which 3Com recommended 48 MB of memory in the management station. The speed on our machine, which has only 32 MB, was less than impressive.

IPX, AppleShare and NFS all worked well through the LANplex, with its proper IP fragmentation. The smooth operation doesn't come cheaply. Our system came with an FDDI interface, an 8-port switched Ethernet module and a 12-port CDDI concentrator, for an overall price of just over $38,000. The CDDI concentrator added about $10,000 to the price.

Digital Equipment Corp.'s DEChub 900 MultiSwitch

The DEChub 900 is marketed as a unique stackable switching hub. It isn't unique or stackable. The large backplane module is about the same as any other, except the backplane doesn't have sides to hold the cards. Instead, they snap into the backplane. It's a much more cost-effective system. A DEChub 900 with two power supplies, an FDDI-to-Ethernet module with six Ethernet ports and an additional Ethernet module with six ports costs only $18,455.

You cannot fully configure the DEChub 900 from either its serial port or by telnet. We needed Digital's HubWatch to finish the job. With HubWatch, you can configure the DEChub 900 modules to form a FDDI ring through the backplane. DEC lists the backbone performance as 3 Gbps, however each ring is truly a 100-Mbps FDDI ring, even for traffic that only goes between Ethernet modules.

Our IPX, AppleShare and NFS trials all worked. While our switch came with only a bridge module, Digital does offer full routing with the DECBrouter90 module. We found the design very serviceable. The modules can be easily hot swapped.

SMC EliteSwitch ES/1

The EliteSwitch was the first to offer Token-Ring switching and SMC plans to follow up with Fast Ethernet and eventually ATM. SMC also offers support for FDDI, HSSI and Ethernet. Our system came with two four-segment Ethernet cards and one FDDI card. The ES/1's backplane has a potential throughput of 800 Mbps, but with the cost of the base hub, the unit tipped the price scale at $31,100.

ES/1 management and configuration are straightforward. SMC offers good SNMP-based GUI tools at an extra cost, and supports telnet and serial port configuration. SMC's command-line interface is easy to follow. ES/1 cards are hot swappable.

The ES/1 will bridge any protocol, as well as route TCP/IP and IPX. Filtering support includes a number of flexible options like per port, per port group and by MAC address. You can also configure virtual LANs or port groups. Other hubs may offer configuration of more virtual LANs, but SMC offers enough for functionality.

While we encountered no problems with the ES/1, we would have liked to have seen higher port density on the ES/1's interface cards.

The Chipcom Galactica Hub

If you want solid construction, the Galactica is for you. Chipcom sent the Galactica five-slot chassis and the boards to populate the chassis separately. We can see why: After populating the unit, it was a two-person job to lift i t. Each card is metal-clad on both sides and could probably withstand the force of a small nuclear explosion.

The Galactica supports only bridging across its 1-Gbps backplane and has only FDDI and Ethernet modules. However, it does support multicast and broadcast filtering as well as a number of other filter types. We had no problem running NFS, AppleShare and IPX through the switch.

Configuring the switch is not trivial. While it supports configuration through its serial port, by telnet and through GUIs, each card in the switch is configured individually.

LANNET MultiNet LET-36 LANswitch

LANNET's LET-36 chassis can accept switching and nonswitching modules. The result is a product that is not quite a hub in the classic sense, but neither is it in the same category as the other switching hubs.

The LET-36 has a high-speed channel on its backplane, as well as four Ethernet speed channels. The high-speed bus accommodates only Ethernet and Fast Ethernet modules. You can install a Wellfleet FDDI router module, but it interfaces only the four Ethernet buses. To go from FDDI to the switching fabric requires external cables to connect between the different modules that LANNET supports.

LANNET refers to its switching architecture as protocol-independent; that means no routing support and only topologies that use Ethernet frame styles. Unlike the other switches, the LET-36 doesn't support the spanning tree protocol. Instead, LANNET supports something it calls hardware-based redundant links. So use caution before adding this switch into a bridged network dependent on a spanning tree.

Because LANNET's switching modules include only Ethernet and Fast Ethernet, we were only able to test IPX and AppleShare protocols, which worked well. Configuring the LET-36 was difficult. LANNET has chosen to incorporate modules for a number of other vendors, each with their own configuration interface. On the positive side, LANNET's GUI configuration utility that runs under HP OpenView allows for easy configuration of virt ual LANs and the switching bus. You should know exactly what you're doing; the software provides no feedback on why certain operations cannot be completed.

For all its strangeness, the LET-36 is a fairly economical system. Many of the modules can support only a few addresses per port and are meant to be directly connected to end-user systems.

UB Networks DragonSwitch for Ethernet

The UB Networks system does not have the bells and whistles of some of the other switches. However, UB is in the process of developing many critical features. Its Token-Ring and ATM modules will be available in the second half of 1995. UB's Ethernet DragonSwitch is its hub's centerpiece, along with an FDDI switch.

The DragonSwitch doesn't support any form of multicast or broadcast filtering-although it does support the creation of virtual LAN segments. All switching modules in the hub can communicate over the hub's 320-Mbps backplane. If you need routing, you can get FDDI and Ethernet router modules. The routing software is complete, supporting IP, IPX, AppleTalk, DECnet and XNS. UB did not provide routing software, so we couldn't test it.

Configuring UB's hub is not trivial. It can't be done from either a serial port or by telnet. UB actually shipped us a laptop with OS/2 and its management application installed. The management application works acceptably, and UB says it is moving toward Unix management platforms.

In our tests, all protocols except NFS passed from FDDI to Ethernet. The UB hub's FDDI module doesn't support IP fragmentation yet. The UB hub can support both switching modules and simple repeaters. Only switching modules communicate across the system's backplane. Our system, with an 8-port Ethernet switching module and the FDDI router/bridge, was $27,495.

Art Wittmann is a senior editor of Network Computing and associate director of the Computer Aided Engineering Center of the University of Wisconsin-Madison. He can be reached via the Internet at wittmann@engr.wisc.edu. Robert J. Kohlhepp can be rea ched at rkohlhepp@nwc.com.

VENDOR INFORMATION

Alantec PowerHub 3150 , Alantec,
70 Plumeria Dr., San Jose, CA 95134.
(800) ALANTEC; (408) 955-9000;
fax (408) 955-9500.
Circle reader service #408.

Chipcom Galactica Hub,
Chipcom Corp., 118 Turnpike Rd.,
Southborough, MA 01772.
(800) 228-9930; fax (508) 460-8950.
Circle reader service #409.

Cisco Systems Catalyst Workgroup
Switch , Cisco Systems, 170 W. Tasman Dr.,
San Jose, CA 95134-1706. (800) 859-2726;
(408) 526-4000; fax (408) 526-4100.
Circle reader service #410.

DEChub 900 MultiSwitch (including
DEChub 900, DECswitch 900
EF and PEswitch 900 TX),
Digital Equipment Corp., 550 King St.,
Littleton, MA 01460. (800) DIGITAL.
Circle reader service #411.

EliteSwitch ES/1 , Standard
Microsystems Corp., 80 Arkay
Dr., Hauppauge, NY 11788. (800) SMC4-YOU;
fax (516) 273-1803.
Circle reader service #412.

Grand Junction FastSwitch
10/100AG , Grand Junction Networks,
47281 Bayside Pkwy., Fremont, CA 94538.
(510) 252-0726; fax (510) 252-0915.
Circle reader service #413.

LANNET MultiNet LET-36
LANswitch , LANNET, 17942 Cowan Ave.,
Irvine, CA 92714. (714)
752-6638; fax (714) 752-6641.
Circle reader service #414.

Network Peripherals EIFO
Client/Server Switching Hub ,
Network Peripherals, 1371
McCarthy Blvd., Milpitas,
CA 95035. (408) 321-7300;
fax (408) 321-9218.
Circle reader service #415.

NetWorth PowerPipes ,
NetWorth, 8404 Esters Blvd.,
Irving, TX 75063. (800) 544-
5255; fax (214) 929-1720.
Circle reader service #416.

SK-NET Switch 6616 , SysKonnect,
1922 Zanker Rd., San Jose, CA 95112.
(800) 752-3334; fax (408) 437-3866.
Circle reader service #417.

3Com LANPlex 6004 , 3Com Corp.,
5400 Bayfront Plaza, S anta Clara, CA 95022.
(800) NET-3COM; fax (408) 764-5001.
Circle reader service #418.

UB Networks DragonSwitch
for Ethernet ,UB Networks,
3900 Freedom Cr., Santa Clara,
CA 95054. (800) 777-4LAN;
(408) 496-0111;fax (408) 970-7337.
Circle reader service #419.

WaveSwitch 100 , PlainTree Systems,
Nine Hillside Ave., Prospect Place,
Waltham, MA 02154. (800) 370-2724;
(617) 290-5800; fax (617) 290-0963.
Circle reader service #420.