TECHNOLOGY - Remotely Possible

02 Jun 1998 View Comments
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Since the beginning of the decade, everyone said it would happen. They said it in 1990, 1991, 1992, 1993 ... for year after year most of us agreed, it has to happen this year ... and it didn't. But now it has. What has? ISDN has. At last it is officially here big time and as a result is no longer the preserve of the rich and/or stupid. Even BT is finally doing its job and vendors have helped things along by bringing product prices down to rock bottom. Whereas a couple of years ago you might expect to pay the best part of a grand for a basic ISDN bridge/router and #500 or more for a terminal adaptor (TA) or simple PC ISDN card, now those costs have been reduced dramatically. PC cards start at well under #100, routers can be yours for around #500 and the ISDN TAs are far more fully featured than of old, but half the price.

High bandwidth required

Of course, the internet has clearly had something to do with this. People want high bandwidth access to the internet but don't want to pay high prices for the privilege. So, hardware prices have come down accordingly and ISDN products have been re-focused on internet access. The realisation that businesses are taking the internet seriously enough to want high-speed access to it has resulted in a number of entry-level boxes, or even complete packages being hastily delivered to market; cheap and simple to use. All across Europe, meantime, ISDN line rental prices have been falling. Timing or what?

So does this finally mean the death of the modem? Don't make us laugh!

Love 'em or loathe 'em, modems are going to be around for a long time yet, the emerging V.90 standard - unifying the rival x2 and K56Flex 56K modem technologies - has ensured that. What this means, then, is that business users and service providers alike must be in a position to support both analog and digital dial-up connections, and lots of them. Consequently, we've seen the emergence of the remote access concentrator; a modular chassis typically supporting a combination of digital modem and Primary Rate ISDN cards and capable of managing 100-plus concurrent calls, either analog or digital.

Here we're taking a look at product examples from both ends of the equation; the end user in the remote office with the ISDN TA and the central office or ISP with the big box taking in thousands of dial-up calls a day.


Over the past 12 months Racal Data has made real attempts to shake off its old fuddy-duddy image with a series of internet-oriented product launches.

Among these is the WINstream ISDN terminal adaptor. This is a small, standalone device which provides support for Basic Rate ISDN, with the option of dual analog ports for connecting your old handsets, modems and fax machines.

Protocol support includes PPP, MLPPP with PAP/CHAP as well as V.120 and X.75. WINstream provides its own PPP server option for use within Windows 95 and NT, for applications such as dial-up networking.

Given Microsoft's less than perfect track record where protocol handling and remote access are concerned, this is a very sensible addition, especially when looking towards the complexities of ML-PPP operation. The provision of two LEDs on the front panel for each ISDN B channel is a simple but very useful feature - one which the other TAs tested here lacked. Such features make life so much easier when configuring and testing the TA and their value should not be overlooked.

The installation for the WINstream continues Racal's much improved install routines in recent times; plug 'n' play auto-detection of the device under Windows 95 appeared to work without problems. One slight irritation - for attaching the WINstream to the PC, Racal supplies you with a 25-9 serial cable and the manual instructs you to buy a 25-25 lead if you need this format. In contrast, the Motorola BitSURFR Pro, also reviewed here, includes a 9-25 converter, so saving you potential hassle. A small point maybe, but they all count. Overall the installation and configuration of the WINstream is as simple as it is possible to be, given the range of features and options it has. A very good effort overall.

Voice operations were tested on the WINstream and proved to be very effective in all modes. Starting with a single B channel in both V.120 and PPP mode, file downloads were activated, after which a voice call was initiated which worked without any problems. Moving then to ML-PPP mode the voice continued to work without any obvious problems or degradation.



In Brief: Basic Rate ISDN terminal adaptor with analog port options, Wizard-based installation and excellent PPP/ML-PPP support.

Availability: Racal (01256) 763911

Price: From #200

Features: *****

Documentation: ****

Build Quality: ***

Value for Money: ****

Overall: ****


For the benchmarking we used four specific access methods, two to the internet, one to a bulletin board and a fourth via a remote access server to the internal network. The connections to the internet were made via Unet, a northern-based ISP, and Bracknell-based Netcom. The latter has recently become a user of BT's Cellstream ATM service, in order to provide an ATM Wan backbone between the company's UK and US networks and therefore provides optimal access to US-based websites. It is worth noting that in back-to-back tests, carried out immediately after each other, internet performance (for file downloads, for example) via Netcom was typically twice that when going via Unet, though the latter was more than adequate. Therefore, all published benchmarks are based on Netcom connections.

For the record, the company uses a USR Total Control Hub as its remote access server.

Early signs during benchmarking showed the BitSURFR Pro to be performing well overall. The Zyxel TA did noticeably better, in relative terms, on the bulletin board access tests than it did in the internet-based tests.

While we tried to ensure similar test conditions on the internet tests across all products, obviously this is not an exact science, so possible variations must be allowed for to some extent. It was noticeable, however, that the Zyxel TA was not 'talking' as well to the ISP host as the other products. It would not stay on-line in PPP mode (PAP/CHAP problems suspected) and was reticent in disconnecting under V.120, needing several attempts to enable this in each session.

PPP testing proved to be something of a nightmare. In the case of the Motorola it simply would not switch into PPP mode and the Zyxel product would not log onto any service correctly in PPP mode. With the BitSURFR we attempted to switch it into PPP mode using AT commands, as laid out in the manual, but still it would not talk to the remote end - for example, the Netcom ISP host. A query with Motorola regarding PAP/CHAP support indicated that it was provided but we could not get it to work correctly during testing. In the case of the Zyxel product, again PAP/CHAP support appears to be at the heart of the problem, though again it is specified.

The WINstream was therefore the only TA we got working properly under both PPP and ML-PPP. It showed good performance with a 50 per cent or so improvement when the second B channel kicked in. This was testing with a 115.2K baud serial port. With a reliable 230K baud serial port (not easy to source) we expect that the device should get close to its maximum 128Kbps throughput (without compression). Overall, in V.120 mode, there was little to choose between the products.


The BitSURFR is a neat standalone black box - almost cute looking if you can say such a thing about what is basically a posh modem.

Like the WINstream, the BitSURFR Pro has two analog ports in addition to a Basic Rate ISDN port. Protocol support includes both V.110 and V.120 rate adaptions as well as PPP and MLPPP. However, with respect to PPP, there was no mention of PAP/CHAP support in any of the literature or configuration/management screens which means problems when trying to talk to an ISPs' RAS hosts.

The BitSURFR uses Windows 95's default PPP server when using dial-up networking. No indicators are available on the TA to tell you whether one or two B channels are in use. This made the implementation of ML-PPP operation something of a guessing game. Motorola bundles copies of Hyper-Access Lite and the Chameleon TCP/IP suite with its TA. The latter proved a dog to install, however, and effected a hard disk crash. In truth the value of this kind of bundled software is minimal, at best.

Like the WINstream, the BitSURFR Pro followed the plug 'n' play, auto-installation route under Windows 95, with no apparent problems. After this followed the installation of the Configuration Manager, an A:Setup job. Interestingly, when bringing up the Configuration Manager, once installed, the device options brought up the BitSURFR and ControlWare - do these guys badge the BitSURFR as well or is it a case of one software manager for two separate products?

Now here is where it gets interesting, but not necessarily for the right reasons, especially if you're Motorola. While Configuration Manager appeared easy to use - point 'n' click stuff, with a gauge showing you when you're downloading a new configuration to the device - it appears that it wasn't really talking to the BitSURFR Pro, even though it said it was. This was proven several times over by setting the configuration to PPP mode, then downloading it, only to find out - see performance tests - that it was still operating in V.120 mode, ignoring the configuration revisions.

This also explains why it was possible to have the configuration manager loaded while using the TA to access the internet, when with the Racal and Zyxel TAs this was not possible, the configuration manager in each case hogging the connection to the TA, preventing access from another application. At first we thought this was a major plus for the Motorola but, in hindsight, it clearly wasn't working correctly. The other options for managing the BitSURFR - terminal access or AT commands - are hardly ideal for the kind of inexperienced users this product is surely aimed at.

The BitSURFR Pro is now sold as part of the BT Ignition package. This all-in-one combination of hardware and software also includes a configuration manager software for easy installation, HyperAccess Lite for file transfer, BT ISDN internet software for web access.



In Brief: ISDN terminal adaptor with dual integrated analog ports. Performs well in V.120 mode but had problems with PPP.

Availability: BT (0800) 800 800

Price: #259

Features: ***

Documentation: ****

Build Quality: ****

Value for Money: ***

Overall: ***


The follows the basic hardware specification of its rivals here, with one ISDN Basic Rate interface and two analog ports.

Both V.110 and V.120 rate adaptions are supported, as is X.75 and PPP/MLPPP protocols. Both the AT command set and the CAPI (1.1/2.0) interface are supported. As with the Motorola product, with respect to PPP, there was no mention of PAP/CHAP support in any of the literature or configuration/management screens which, again, meant problems when trying to talk to ISPs' RAS hosts. Like Motorola's BitSURFR, the Zyxel product uses Windows 95's default PPP server when using dial-up networking. However, at least here - as with Racal's WINstream, there are two LED indicators on the TA to tell you whether one or two B channels are in use.

The Zyxel was another plug 'n' play installation under Windows 95. As with the other devices, the PC picked up its existence and prompted for the manufacturer's driver disk. This is where the installation fell down a little.

First, the .INF files which Windows 95 was seeking were not on the root directory of the supplied floppy, so it was necessary to browse for them, finding them in a sub-directory on the floppy. The second complication was that Zyxel provides specific drivers for specific operational modes, which could confuse an inexperienced user. There is a catch-all option, Zyxel's configuration manager which appears as a separate driver option during the installation.

In accordance with advice from the manual, this is the option we chose and worked with throughout the testing. Zyxel has now made a revised manager available on the internet but this was not tested.

The configuration manager was not dissimilar in principle to that supplied with the WINstream, but neither as easy to use, nor as informative. As a result, we were always left hoping, rather than confident, that the TA was configured as required. Falling back to AT commands was the only play-safe alternative, far from ideal for inexperienced users.



In Brief: Basic Rate ISDN terminal adaptor with two analog port option. Not as easy to use as the best of the competing TAs, especially when trying to use PPP mode.

Availability: Zyxel (0118) 981 0600

Price: #229

Features: ***

Documentation: ****

Build Quality: ****

Value for Money: ****

Overall: ***


The first point we need to make about remote access servers is that it is very easy to assume that they're all much the same - a chassis supporting a number of modem or ISDN modules with some kind of management interface and little else to distinguish one from another. So, in an area where the hardware can pretty much look like 'me too' boxes on the surface, it is important to be able to provide distinguishing features deep inside the product.

What, then, can the PortMaster 3 offer as a distinctive alternative to the Ascends of this world? We can start by seeing how the PortMaster 3's specification looks on paper and the answer is that it holds plenty of promise. Basically, Lucent has combined access server and router into a single device with the obvious key feature of supporting both modem and ISDN as a single entity. This means you can support both analog (originally up to the Rockwell/Lucent designed K56flex 56K modem standard, but now with support for the emerging V.90 standard) and ISDN (V.120, PPP or ML-PPP) access with a single incoming phone number. And you don't need to worry about differentiating between ISDN and modem calls. The PortMaster 3 intelligently switches between ISDN, ISDN data over voice, and analog modem calls over the same PRI line.

On the subject of Wan support, this is further extended to Frame Relay and synchronous leased lines, including T1 or E1 signalling, the latter being the key where Europe is concerned.

So what is inside the box? The PortMaster 3's architecture is based round a PC-like bus supporting a central AMD 486 processor running Lucent's own ComOS remote access operating system - standard across all Lucent products, as well as originally within USR's Total Control Hub - and supported by 4MB of memory, expandable to 32MB maximum, and 1MB of Flash memory.

The 486 processor, running at an internal clock speed of 66MHz, is solely responsible for routing. All other processing is offloaded to other distributed processors. For example, PPP framing is handled by either the Wan interface chipset or the 'True Digital Modem' DSPs (digital signal processors).

Six internal slots are available for what Lucent terms its 'True Digital Modem' cards, with up to 10 modems per card, 60 per device. Even without digital modems installed, the PortMaster 3 can be used for ISDN calls, Frame Relay, or leased line service without any additional equipment (Terminal Adaptors or CSU/DSUs).

The PortMaster 3 can also be used as a dial-out modem server. It allows users on the Lan to establish a Telnet or Rlogin session for accessing dial-out modems or outbound ISDN lines.

An optional hardware module provides Stac-based data compression. This provides compression for up to 60 concurrent sessions and high-speed dedicated links. One selectable Ethernet port is provided (10BaseT, 10Base2 or 10Base5), along with one 115.2Kbps asynchronous port.

All-important resilience is provided in the form of 'hot' spare modem pooling, whereby each chassis can be over-populated with modems beyond the total addressable ports, which act as on-line spares in the event of a modem failure.

A redundant PSU option, per device, is also available. Lucent's digital modems process all modem signals in a pure digital state throughout the entire communication, eliminating analog drawbacks. Each modem uses only a single DSP, so heat dissipation is reduced by up to 90 per cent, always good for reliability. And, in the - let's be honest here - always possible event of modem failure, an automatic self-busy-out feature ensures that failed modems are removed from the incoming call hunt group, eliminating the risk of an unresponsive modem.

Other than the still dubious merits - when considered against ISDN - of 56K modem technology, other modem support covers everything you could want, right down to V.22bis and all stops in-between. Lucent is also keen to make the point that its true digital modems ensure near-zero obsolescence by using Flash memory for easy upgrades to new modem standards.

In-built routing support includes RIP, OSPF and variable-length subnet masking (VLSM), which means with IP you can segment one class A, B, or C address into many subnet addresses of different sizes for use in multiple points-of-presence - ideal for an ISP. Wan Protocols cover PPP, ML-PPP, SLIP, CSLIP and Frame Relay PVCs. Lan protocols are restricted to IP and IPX, so no surprises there!

Performance-wise, during testing we ran analog then ISDN connections into the PortMaster 3, using Windows NT4 servers and clients (running dial-up networking) and were able to achieve over three times the performance using a single 64Kbps ISDN channel than we achieved with modem-based connections, even with a 56K modem. The problem here was that we used a USR V.Everything modem, which could only talk to the Flex-standard Lucent cards at 33.6Kbps max.

Even so, with data compression we were able to get in excess of 42Kbps transferring PowerPoint slide presentations (.PPT files) using modem-based access. However, this paled into insignificance compared with the 130Kbps-plus that we managed to achieve with a single ISDN B channel and PPP, while a switch to ML-PPP, using both B channels increased this further, though you never quite get double the throughput again.

Management-wise, any number of PortMaster 3s can be configured and managed from a single, central site. The device can be set up in three distinct ways - via a direct comms port connection, by a telnet session, or through a Windows 95-based application PMconsole. SNMP is also supported. The first two methods use a character-based system aimed at terminal users which follows many of the same rules as those of its competitors. Namely these are a Unix oriented combination of command line and simple (but obscure if you're not familiar with them) parameter additions. A very basic help function - again typical of the genre - is available.

Here are two very different approaches to management. The command line-based access might be what the Unix gurus love, but there are plenty of potential ISPs who've come straight from the world of used-car selling and couldn't recognise a Unix kernel to save their lives. In truth, the command line approach is still what most pros will choose to use and follows the lines of most competing products over the years, so it's familiar enough to those with experience. Alternatively you can use the Windows or Unix-based PMconsole.

Lucent is in the process of releasing a revised Windows 95 version which we were able to look at and it really does simplify the configuration of a device for a less experienced user, to the point where you largely point 'n' click and drill down to get to the port, user or whatever it is you're trying to configure. It has also added some statistical and excellent debugging information which was previously only available at terminal-access level to the revised Windows version of PMconsole, making the latter a genuine alternative. Management options extend further to the use of Lucent's RADIUS authentication and accounting software.

The Lucent PortMaster 3 also includes ChoiceNet filter management software, a client-server-based application like RADIUS which lets you customise access to the internet on a per-user basis with the storage and management of all user filters and site lists, again centralised.

To date it's a case of so far so good, but what about scalability issues?

Well what at first looks like a neat but small - and therefore potentially limited - grey box, is far more expandable than meets the eye. There is the modularity within the box of six digital modem card slots with up to 10 K56flex modems per card.

And on the subject of 56K standards, or the lack of them, Lucent guarantees you a free upgrade to the forthcoming ITU-T 56K standard, as and when it finally appears. Better still, multiple PortMaster 3 servers can work together as a single virtual chassis, when all port resources can be pooled and made available for either ISDN or analog service at any time.

The PortMaster 3 allocates True Digital Modems in a first-available and fully verified fashion, not a random pooling technique. It also allows the central processor to perform a test on each DSP before every call.

The DSP memory is tested to verify that it is executing instructions properly.

The DSP is automatically removed from the pool if any error is detected.

The way in which it scales beyond just a single box, letting you set up multiple PortMaster 3 units to act as a single remote access server, is achieved using a methodology called MCPPP (Multi-Chassis PPP). Among other things, this solves a problem that many ISPs have found to date - that of guaranteeing high bandwidth (for example, 128Kbps ISDN) access to the internet, the kind of access capabilities typified by any old low-cost ISDN TA supporting MLPPP nowadays.

Often when an ISDN user dials into an ISP's PoP, each channel typically hits a rotary, or hunt group. The hunt group will send the channels to the same PoP Access Server or to different devices, depending on circuit availability. If the PoP is lightly loaded, then connecting either one or two ISDN B channels is not a problem. Generally, both channels will land on the same access server.

However, most ISPs generally stack several access servers in a single PoP, and problems arise when an ISDN user dials into a heavily loaded ISP PoP. Channels can easily land on different access servers within the PoP. Unless the access server has the ability to combine multiple ISDN B channels across multiple Access Servers, the result is a single 64Kbps connection, even though a 128Kbps connection is requested by a customer and is technically feasible.

For this reason, Lucent developed MCPPP to allow for hundreds of high-bandwidth dial-in connections to be provided across a single hunt group.

Smart thinking. MCPPP is a protocol that allows incoming ISDN BRI calls from any ISDN device using MLPPP to span multiple PortMaster 3 units that reside on the same Lan, since they are working together as a single logical stack.

This methodology is clearly effective when a rotary (or hunt group) is used to access multiple PortMaster 3 units at a central site or remote PoP. When a rotary is in place, the same telephone number is used for all calls dialling into multiple PRIs at the remote PoP. While rotaries provide an ISP with the ability to manage a single dial-in phone number, it is impossible to guarantee that the subsequent call be answered by the same PortMaster 3 as the first call, so MCPPP allows a single hunt group and phone number to be used across multiple PortMaster 3s. Which in turn means you can support more concurrent connections, and therefore more customers or users, than you could with a fixed, non-MCPPP solution with the same number of physical ports. Having multiple units working as a single entity also keeps management simple but removes the single point of failure common with a large, single-unit solution.

Overall, Lucent seems to have provided a comprehensive ISP solution with the PortMaster 3. It is particularly ideal for those looking to start with a small system but who want to be unrestricted in their growth, without having to upgrade their box every few months. With the MCPPP technology you just attach another PortMaster 3 chassis in true stackable hub fashion.

From a futures point of view, it will be interesting to see how the company can support any emerging technologies, such as the xDSL or Nortel 1Mbps modem-based technologies, if and when they take off, within the PortMaster concept. Given the open architecture of the chassis, however, there is no reason any technology - ATM included - cannot be support by Lucent's PortMaster 3 in the future.



In Brief: Mid-range remote access chassis with many excellent features and easy management.

Availability: Lucent (00 33) 4 92 92 48 48

Price: from #2,000

Features: ****

Documentation: ****

Build Quality: *****

Value for Money: ****

Overall: ****


With the amount of activity currently in the service provider market, it is not unreasonable to expect serious levels of competition among the remote access vendors, vying for their fair share of emerging new markets.

New markets and new users there might be, but the major names who dominate have been established - except for one. Ascend was unknown until the internet boom, but it quickly established itself as a major presence in the ISP remote access chassis market with its Max and - latterly - TNT products.

The company did much to create the market for combined analog/digital port concentrators, but has recently seen something of a downturn in its fortunes.

Maybe this has something to do with a certain company called Cisco which now has a significant presence in the ISP market as well as its traditional corporate user base, most recently with its 5,300 access server. In line with the competition, the 5,300 supports both ISDN and 56K modem access, with up to four T1/E1/PRIs per chassis meaning up to 120 concurrent calls can theoretically be supported, and 1,680 when daisy-chained in Cisco's AccessPath integrated access system.

The architecture is based round a RISC processing engine, supported by DSPs controlling port activity. Both 10Mbps and switchable 10/100Mbps Ethernet ports are provided, providing secondary, redundant access to the Lan. Based on Cisco's IOS, the 5,300 supports the RSVP reservation protocol as well as WFQ (Weighted Fair Queuing) in an attempt to prevent bottleneck problems arising with different traffic types all being handled in the same way.

3Com is another major networking player who has an ISP-oriented remote access chassis, in the case of the US Robotics-originated Total Control concentrator. The product was designed to integrate the capabilities of channel banks, DSU/CSUs, modems, ISDN equipment, routers and terminal servers in a single chassis. It provides ISDN or analog dial access to asynchronous hosts, Frame Relay, and Ethernet or Token Ring networks.

The Total Control chassis has a modular architecture based on interface and application cards which can be hot-inserted or removed while the chassis remains on-line. The chassis' internal components include the capabilities of channel banks having integral DSU/CSUs, PRI signalling for connection to ISDN, analog or digital modem functionality - with full V.90 56K modem support - and Terminal Server and router functionality for IP and IPX protocols and Frame Relay connections.

Meanwhile, Lucent RABU - whose PortMaster 3 chassis is featured in the review section - has just introduced a high-end concentrator.

Called the PortMaster 4, it supports up to 864 simultaneous connections in a chassis, which is barely larger than a computer monitor.

Aimed at the public carrier, corporate and ISP markets, the PortMaster 4 supports ISDN, 56K (and below) modems, E1 and E3 leased lines, auto-detecting what type of incoming call is being received and switching the service on that port accordingly.

The system is modular in nature and takes up to 96 modems on a single module, with 10 slots available in total. Rather than having a classic bus-based backplane, the concentrator uses ATM switching technology to interconnect the various modules within the system. As well as providing high port concentration, the PortMaster 4 has also been designed to provide very high levels of resilience with redundant controller, switch fabric, power supplies and fans.


It is fair to say that Shiva is not exactly a name associated with high-end ISDN switches.

But for a couple of years now, the company, best known for its modem-oriented remote access servers has been looking to employ the ISDN technology it acquired from Spider Systems in 1995 in many new markets, one of which is the ISP niche. The result, product-wise, was the LanRover Access Switch; designed directly to take on the then clear market

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