Copyright (c) 1996 Ziff-Davis Publishing Company
PC Magazine -- April 9, 1996
Les Freed
New ISDN products provide seamless, secure LAN remote access without the hassles that plagued their predecessors.
If you need to connect a few remote PCs to your IPX-based LAN, we have a pleasant surprise for you. There's a new generation of ISDN remote-access products that can pave the way. These routers are similar to their leased-line relatives, except that they use an ISDN line in place of a more expensive--and less flexible--dedicated point-to-point leased line. And they're much better behaved than before.
ISDN routers provide an on-demand link between two points. You can use them to connect multiple LANs on an as-needed basis, or you can connect smaller branch-office LANs and even single-workstation, work-at-home users.
For this article, we took a close look at several remote-access products, focusing on those suitable for the small-office and home-office market: Ascend Communications' MAX 4000 and Pipeline 25 ISDN Router, Gandalf Technologies' XpressStack BRI and XpressConnect LANline 5242i, and Symplex Communications Corp.'s DirectRoute DR-1 and DirectRoute Remote RO-1. The Ascend solution will also work for larger installations.
ISDN remote-access products have come a very long way in a very short time. Early ISDN remote-access products had a well-deserved reputation for being difficult to configure. Not surprisingly, all of this progress is in part the result of the remarkably rapid growth in popularity of the Internet, which created a huge demand for faster, easier-to-use routing products.
Internet service providers, for example, are clamoring for flexible, easily configurable routers to get their customers connected. In response to all of this demand, Ascend, Gandalf, 3Com, and other companies have developed relatively user-friendly ISDN routers. Interestingly, it's an IP trend that has benefited the IPX world.
The new Internet routers' first cousins, the products we tested here for the remote site, are equally easy to use. They can be used to route Internet IP traffic as well as NetWare IPX traffic, so you give your remote users a much faster route for connecting to the corporate LAN. And once installed, they provide a nearly seamless link between the remote PC and the host LAN.
The solutions we tested provide remote Ethernet connections over basic rate interface (BRI) ISDN lines. They each consist of a host unit and one or more client units. The host-side unit connects directly to the main-office LAN and to one or more ISDN lines, providing access for two remote users per BRI line. All of the host-side units we tested support multiple BRI connections: the Ascend and Gandalf each have eight ports, and the Symplex unit has four. Ascend also supports PRI links.
The client-side units are modem-size boxes, each with an ISDN-line interface and a 10Base-T Ethernet connector. The client router's 10Base-T connection provides a single Ethernet port, but you can connect the client router to an Ethernet hub to provide multiple ports to service several PCs.
These products require no additional software at either end of the connection, and they make no resource demands on the host LAN, the file server, or the client PC. The remote PC needs an Ethernet NIC and the appropriate LAN driver software--just as it would if it were connected directly to the main office LAN. (See the related sidebar "Who Needs Ethernet Anyway?" for products that connect differently.)
These ISDN remote-access units have a lot that recommends them beyond ease of use. First, they're enormously cost-effective when compared with dedicated lines, which are very expensive. Programmed to dial up the main office automatically when they detect outbound LAN traffic, these products will also disconnect the ISDN line--saving time charges--when LAN traffic drops to zero for a predetermined period of time. All three products use a technique called protocol spoofing to prevent the constant server and router broadcast messages from bringing up the link.
In addition, the host-side routers are not limited to ISDN clients. All three vendors offer a choice of connectivity options ranging from analog lines (Ascend offers built-in V.34 modem modules) to T1 leased lines, letting you mix and match media to meet your company's needs.
An extra bonus for SOHO installations is voice service. One of ISDN's big attractions is that it provides two channels per line. Either channel can be used for voice or data traffic. Two vendors here, Ascend and Gandalf, provide an analog voice port on the remote unit. This allows you to maximize your use of the ISDN phone line by opening it up for voice calls.
Our testing showed that these products are surprisingly fast and flexible. All of the products here can work as routers; we tested them, however, as IPX bridges, because bridging is typically more efficient when there are a very small number of client PCs at the remote site. Our test-bed setup had only a single client PC on the remote side.
We found all three units fairly easy to set up and configure. Typically, you connect the LAN and ISDN lines, then configure the router through a terminal attached to the router's serial port. If you're running TCP/IP on your LAN, you can link to the routers from the LAN via telnet--but you'll still need a terminal to perform the initial setup.
The Ascend and Gandalf host-side routers communicate using both Point-to-Point Protocol (PPP) and Multilink PPP, which are industry-standard protocols. This means that--with the proper client software--you can concurrently use several vendors' client-side products to connect to one host LAN.
We were able to connect to the Ascend and Gandalf routers with a Motorola BitSurfr Pro using Microsoft Windows 95's built-in dial-up networking facility. Though the Symplex product used a proprietary protocol at the time we tested, the company says that it is working on PPP and Multilink PPP options for its routers.
All three products provide data-compression to maximize the throughput on the ISDN line. Ascend uses the Stac data-compression coprocessor, and Symplex uses a proprietary data-compression scheme. Gandalf hedges its bets by using both Stac's and a proprietary compression scheme. The approach works well: Gandalf's products led Ascend's and Symplex's on our File Throughput test for all three file types.
Good data compression--combined with ISDN's fast call-setup times--means that your remote users may not even feel that they're remote. ISDN remote-access routers could be the key to stepping up your remote users' productivity.
Editors' Choice
These two products from Gandalf Technologies are impressive. They're easy to use, and they scored highest in our performance testing. But that's only half the story. Gandalf pays close attention to details. The status LEDs on the XpressStack host-site router are a nice touch and a useful troubleshooting tool, and they're on the front panel where you can actually see them. We also liked the XpressStack's eight-port configuration. It's just the right size for small-business and departmental LAN access.
The 5242i remote unit has its share of convenient features too--a quick-connect button, excellent analog voice support, and a hefty metal cabinet that is well shielded against RF emissions.
We liked Symplex's ease of configuration and low price tag. If you can live without voice support for your client units, it's a fine product that's easy both to configure and to use.
Ascend Communications' duo might have walked away with our Editors' Choice if it didn't have such a high price tag. Ascend's MAX 4000 supports many more clients than the Gandalf and Symplex products. Used with PRI lines, the MAX's price per port is in line with the competition's. So if you need to start big and grow bigger, the MAX 4000 could be the right choice. We'll keep a close eye on its smaller brother--the MAX 1800--for our next review of these products.
The ISDN You May Not Know
By Les Freed
ISDN has been on the scene for nearly ten years, but its slow adoption has meant that it remains a mystery to many. Although most of you know that ISDN is a digital service that provides faster throughput than a modem, beyond that the definitions get much fuzzier. To keep you at the bleeding edge of this technology, we've compiled a list of the top ten things you should know about ISDN.
You may have heard that ISDN is difficult to order, that your ISDN equipment must be carefully configured to work with the phone company's switch, and that the whole thing is generally a pain in the neck to set up. This was true up until about a year ago, when the local phone companies and equipment makers finally began to get their acts together. Ordering ISDN is now fairly simple. Most telcos now have special ISDN ordering lines, and most equipment is flexible enough to operate on virtually any ISDN line.
There are two types of ISDN lines. The first type, a basic rate interface (BRI) line, provides three data channels. The two B (for bearer) channels are typically 64-Kbps, but in some places they run at 56 Kbps because of limitations of the phone company switch. The D (for data) channel carries call-setup and signaling data at 16 Kbps between your ISDN device and the phone company, and it is not normally used for anything else.
The second type of ISDN line, a primary rate interface (PRI) line--also called a channelized T1 line--provides 23 B channels and one D channel. In most places, one PRI line is much cheaper than 111/2 BRI lines. If you need a large number of ISDN lines in one place, PRI is the way to go.
Each B channel operates independently of the other and can carry voice or data. On a BRI line, you can place two separate calls to two different locations at the same time, and in most places each B channel can have its own phone number. This means that your remote-office computer can be talking to the office LAN on one B channel while you're having a voice conversation on the other.
There is no interference between the two channels. Your voice call doesn't slow down the data transfer, and in turn, the data transfer doesn't interfere with your voice call. ISDN terminal equipment can tell the difference between an incoming voice call and an incoming data call, so voice calls ring your phone but data calls are automatically answered by the computer.
If you need to, you can combine the bandwidth of both B channels to get 128-Kbps data throughput. Keep in mind, though, that if you go this route you cannot talk on the phone at the same time. Some ISDN units offer a feature called bandwidth-on-demand (BOND), which allows you to use 128 Kbps for data until you pick up the phone. When you begin a voice call, the bandwidth will drop to 64 Kbps for the duration of the call. Standards for BOND are still evolving, but virtually all vendors are working toward a standard protocol.
Many people still believe that ISDN phones can call only other ISDN phones. This was true once, but now you can call any voice telephone anywhere in the world from any ISDN telephone and vice versa. ISDN voice calls are startlingly clear, especially on long-distance calls. When you call ISDN-to-ISDN, the voice quality is so good that it's almost spooky.
Local utility rates vary widely, but in many places one ISDN line costs the same as or less than two analog phone lines. Some phone companies charge by the minute for ISDN usage, some charge only for data calls, and some offer unlimited calling. Check with your local phone company or your state's public utilities commission for the rates in your area. ISDN long-distance rates are usually the same as those for normal analog calls.
There's bad news and good news about ISDN. The bad news first: You can't plug analog telephones, fax machines, modems, or answering machines directly into an ISDN line. Even worse, ISDN telephones are horribly expensive, and we've never even heard of an ISDN answering machine. Now for the good news: Most ISDN routers and terminal adapters include one or two RJ-11 analog telephone jacks. The terminal adapter generates a dial tone when you pick up the line, and it converts Touch-tone signals into the equivalent ISDN dialing codes. So you can keep your old office equipment after all.
Analog telephone lines work when the power goes off. ISDN lines do too--but your ISDN equipment doesn't. If you plan to use an ISDN line as your only voice phone line, invest in a small standby power supply so you can keep talking through those inevitable power outages. (You should have standby power for your PC, anyway.)
There are two types of ISDN line interfaces in use in the U.S. and Canada. Both use the same 8-pin RJ-45 connector, so it's easy to get them confused. The U interface is the actual line interface provided by your phone company. Unlike an analog phone line, a U interfaces can have only one device connected. Virtually all ISDN equipment sold for the SOHO market includes a U interface jack: You simply plug the line into the jack and forget about it.
The S/T interface, your second option, is more flexible, although now that most TA units include analog phone jacks, it's fading away. The S/T interface allows up to eight devices to be connected to a single ISDN line. To use it, you need a device called a network terminator, or NT-1. Included on some ISDN products and optional on others, the NT-1 box plugs into the ISDN U interface and provides two or more S/T jacks for you to connect to your equipment. Normally, you'd use the S/T interface to connect two or more devices--for example, your terminal adapter and one of those overpriced ISDN phones mentioned earlier.
Some detractors argue that ISDN offers too little, too late.
They point to up-and-coming technologies such as cable modems and asymmetric subscriber digital line (ASDL)--both of which offer bandwidth many times that of ISDN--and ask why anyone should bother with ISDN. Well, ISDN was an up-and-coming technology once too, and it took nearly ten years to reach its present status, where it is universally available. Remember that telephone companies take a long time to adopt any new technology. ISDN is here now, backed by international standards and ready to go.
Who Needs Ethernet Anyway?
By Les Freed
The three solutions in our main roundup provide remote Ethernet connections in the physical sense: Each includes a 10Base-T connector on the rear panel of its client-side unit. Other ISDN products out there connect directly to a single PC, bypassing Ethernet altogether in favor of a less expensive software solution.
Interestingly, the two products we consider in this sidebar couldn't be more different, despite their fundamental operational similarities. 3Com's AccessBuilder 4000 ISDN, like the routers in our main roundup, is a freestanding box that attaches to your LAN via Ethernet or Token-Ring cable. Digi International's Datafire/4, on the other hand, is an internal card that you install in a server or dedicated LAN gateway PC.
The AccessBuilder remote server is a flexible host-side router that can talk to a variety of ISDN, analog, and leased-line devices. At $3,495 for the basic unit, the AccessBuilder is reasonably priced. A four-line ISDN interface card costs an additional $3,495. The unit can host two cards, providing connections for as many as 16 clients at once. If you need a mix of analog modems and ISDN, you can install one ISDN card and one eight-port RS-232 interface card. You can connect up to eight external modems to the RS-232 interfaces.
The supplied Windows-based configuration software, 3Com Transcend AccessBuilder Manager, is a pleasure to use. You can run it from any computer on the LAN. When you start the program, it automatically locates any AccessBuilder units connected to the LAN. A step-by-step guided configuration makes the initial setup as painless as possible. What's more, Transcend's troubleshooting suite includes diagnostic and monitoring tools that really stand out from the competition's.
3Com bills the AccessBuilder as a multiplatform, open solution for remote access. It supports 3Com's own client solutions as well as virtually any PPP- or SLIP-compliant client, including Apple's MacTCP, many Unix clients, Windows 95 Dial-Up Networking, and Windows NT Remote Access Service. On the first try, we were able to connect the AccessBuilder to a Windows 95 PC with a Motorola BitSurfr Pro installed. That's no mean feat, for any of these products.
3Com's client offering combines its AccessBuilder Remote software for DOS and Windows and the 3Com Impact ISDN ISA Adapter. The Impact is available as a modem-size package or as an internal card (for more information, see "3Com Makes an Impact on ISDN," Network Edition, November 21, 1995). It provides PPP and Multilink PPP ISDN connectivity as well as an analog telephone port and optional V.32-compatible modem. The AccessBuilder client software can operate with virtually any ISDN terminal adapter or analog modem, so you're not locked into using 3Com's client products.
There's only one weak spot in the AccessBuilder lineup: performance. We didn't include the AccessBuilder in our product comparison charts, but it was significantly slower than any of the three solutions in the main roundup. Part of the problem is the AccessBuilder's lack of data compression, and part is the 115.2-Kbps limitation of the PC's serial port. Given 3Com's technical prowess, we don't expect this performance gap to last for long. Even without compression, the AccessBuilder is not a bad choice for companies that need a mix of modem and ISDN access ports.
Digi International offers an interesting, low-cost alternative to a traditional LAN router with its Datafire ISDN LAN adapters. These products combine one or four ISDN-line interfaces and a LAN adapter on a single card. At the host side, you install one of the four-line Digi Datafire/4 cards in a LAN file or communications server. The card appears to the server as an additional LAN card. A single-line Datafire card installed in the client PC connects to the host system over the ISDN line. The client card also appears to the client OS as a LAN adapter card and requires that you install LAN drivers.
Digi's software provides dial-on-demand connectivity between the server and up to four clients. Digi provides server drivers for NetWare 3.x and 4.x, Windows for Workgroups, and Windows NT Server. The Datafire server can talk to any PPP-compliant client as well as to other Datafire products. It's a very flexible system.
Because it's an internal card, the Digi Datafire/4 requires a bit more installation work than the other products we tested. And because the Datafire host software runs on the server, it makes some resource demands. Still, the performance penalty is minimal.
The Digi Datafire client does not provide a voice port, however--a feature we think is essential for products in the SOHO market. Still, if you need to connect just a few remote users, the Datafire is worth a look.
AccessBuilder 4000 ISDN. List price: $3,495; four-line ISDN interface card, $3,495. 3Com Impact ISDN ISA Adapter. List price: $599. 3Com Impact ISDN External Digital Modem. List price: $499. 3Com Corp., Santa Clara, CA; 800-638-3266, 408-764-5000; http://www.3com.com.
Digi Datafire/4. List price: $2,995. Digi Datafire U Client. List price: $595. Digi International Inc., Eden Prairie, MN; 800-344-4237, 612-943-9020; info@digi.com.
Each of these products connects directly to a PC, bypassing Ethernet in favor of a less expensive solution. But the similarities stop there.
Performance Tests
During testing, we looked at both the performance and the interoperability of these multiple-BRI central-site ISDN products. All performed well, but the Gandalf product, which uses twin RISC processors for compression, bested the others on every version of the test. Ascend's and Symplex's compression technologies depend on third-party and software solutions, respectively.
We found that the three solutions we tested--the Ascend MAX 4000 and Pipeline 25 ISDN Router, the Gandalf XpressStack BRI and XpressConnect LANline 5242i, and the Symplex DirectRoute DR-1 and DirectRoute RO-1--performed differently depending on the type of file we were transferring. We tested using compressible files, such as a text or vector graphics file; moderately compressible files, such as an executable file; and noncompressible files, such as JPEG files.
The Gandalf router was equipped with twin Intel i960 RISC processors to handle data compression. It was the best performer on our file-transfer test, no matter the file type.
Close inspection revealed that the Ascend solution, which uses a Stac compression chip, suffered when tested with our noncompressible file. This product's compression algorithm examined each data packet in each file, whether it was compressible or not--a process that wasted a lot of time. A smart compression algorithm should detect noncompressible files, suspend compression in order to save time, and reenable the compression as soon as the next compressible file comes in.
The Symplex product did not use a dedicated hardware compression chip. It performed software compression using its own AMD 29000 RISC CPU, which made it less efficient than the other two products in transferring the highly compressible file. In general, our test results showed that a file's compression ratio directly affects its transfer performance. The higher a file's compression ratio, the higher the file-transfer speed it will achieve. This happens because the compression engines in ISDN routers do not need to repeat the compression process for files that are already highly compressed.
We created a central-office network, including a NetWare 4.1 server and a Windows for Workgroups 3.11 local client. We also set up a Windows for Workgroups 3.11 remote client over an ISDN network. In some additional testing not reported here, we used a Windows 95 client. In general, Windows 95 provides a more robust base operating system for communications. All clients were running VLM 1.2.
We asked each vendor to submit its multiple-BRI ISDN product for our central office network, as well as a single-BRI ISDN unit for a remote client. We tested each vendor's central product with its client unit, connecting each product to the test-bed via an RJ-45 connection.
To simulate typical remote users downloading files from their central offices over an IPX connection, we ran our File Throughput test with the following three files: a 983K vector graphics file that could be highly compressed (up to a 7.7:1 compression ratio), a 327K executable file that could be compressed moderately (up to a 2.5:1 compression ratio), and a 131K JPEG noncompressible file.
We transferred the three files from the network to the remote client and measured the speed of each transmission. We ran each version of the test three times to confirm the results.
For our interoperability tests, we connected the products to a Motorola BitSurfr Pro installed in the remote client. The BitSurfr Pro is fully compliant with Multilink 6. We tested each product's ability to complete an ISDN call, to perform PAP and CHAP authentication, and to utilize both B channels successfully.
The MAX 4000 and Pipeline 25 gave the illusion of a direct connection to the main-office LAN.
Symplex takes a more transparent approach to ISDN routing than the others. And the difference pays off.
Copyright (c) 1996
Ziff-Davis Publishing Company