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Features - February 2000 - A guide to RAS
ComCat offers a guide to choosing between proprietary RAS box or open RAS solution

IBM’s tele-cottage experiment suggested that in order for companies to cut overheads it was not vital for everyone to work from their office desk. Some companies today operate a process of ‘hot-desking’ - whereby a worker could go to any ‘free’ desk in the company, plug their laptop into the corporate LAN with access to all documents, data and peripherals on the LAN. The tele-cottage principal proposed that it could be done from a series of shared smaller office buildings within an easy, short commute from home.But how is this possible?

The in-house RAS solution

The options are a closed box proprietary hardware and software, or an ‘open’ solution based on existing industry-standard hardware and o/s software such as NT. With Windows NT Server 4.0, RAS allows multi-link channel aggregation, enabling desktop clients dialling in (on an ISDN Basic Rate line) to combine two or more ISDN B channels to achieve speeds of 128kbps or greater. NT Server 4.0 also contains Point-to-Point Tunnelling Protocol (PPTP), allowing users the cheaper choice of using the Internet as a virtual private network (VPN) to reduce erstwhile expensive long-distance dial-up calls to cheap local calls. RAS is a sub-set of RRAS (RRAS adds routing to RAS).

It is also possible to provide remote access for a number of employees and possibly also certain business partners, customers or suppliers with a proprietary RAS ‘box’ or an ‘open’ RAS solution.

Proprietary RAS box vs. open RAS solution?

As with any proprietary vs. open solution, you have to carefully consider whether the in-house IT/IS expertise and resources are sufficient to cope with setting up your own in-house RAS solution – or whether you would rather buy in a turnkey bespoke proprietary solution. Of course historically, with specialist exceptions, the IT world has moved away from proprietary ‘locked-in’ solutions, to ‘open’ future-proofed solutions. Cost considerations include looking carefully at the cost of initial installation and the total cost of ownership (TCO). This should include any external consultancy costs and on-going service or maintenance contracts over time. Of course if you already have competent NT-qualified staff, then they should be able to rapidly and cost effectively exploit the RAS benefits of NT. You should also consider a tightly defined corporate policy on remote LAN access and information access.

Those who will benefit are organisations with staff who need access to the central HQ’s LAN resources and data from regional offices, from a small-office-home-office (SOHO), from a hotel during travels, and suppliers or strategic partners. These include laptop users wanting GSM cellular phone connection to their HQ LAN, V.90 modem SOHO workers, and RRAS routers or proprietary ISDN routers for connecting at 64Kbps. Often a key driver for RAS is merely the ability for remote or travelling staff to access their emails - and faxes if you have a network fax server - off the corporate LAN. This improves customer service and responsiveness.

Deciding factors

Issues to consider when choosing a proprietary vs. ‘open’ RAS solution include: cost of initial purchase, total cost of ownership, support cost, ease of installation, ease of configuration, staff training, speed and size of scalability, performance improvement opportunities, manageability and integration with other ‘open’ software applications (for management, security authentication, modem pooling etc). Open RAS also offers the advantage of using complementary off-the-shelf software such as Citrix WinFrame and MetaFrame, Lansource WinPort for modem pooling, Spartacom MPNT, and RADIUS (Remote Authentication Dial-In User Service) security packages.

Possibly the very first consideration should be whether the number of remote access users is likely to be consistently less than or greater than 256 ports on one RRAS server or 48 demand-dial users. Above these numbers and you’ll probably benefit more from a proprietary RAS ‘hotbox’ that could give your RAS service slightly greater security and management flexibility. Cisco and 3Com are such solution suppliers.

However, below these numbers and with a WindowsNT 4.0 server and in-house NT skills, you are more likely to benefit most from using the indigenous NT RAS or RRAS service. Why buck the industry trend to open systems with all its flexibility, cost effectiveness and independence? RAS is based on open PC systems for maximum LAN/WAN interface choice.

Other benefits

Ease of use
- While proprietary systems are usually plug’n’play to install, they may take more system management time once up and running. IS staff familiar with NT configurations and management are more likely to make installation, configuration and management in their stride longer term.

- Proprietary systems such as those used by large enterprises and ISPs or the new generations of ASPs (Application Service Providers) and RASPs (Remote Access Service Providers) can offer several hundreds of RAS ports. Open RAS solutions are good at offering a rapid start of a remote access service to corporate users with existing hardware and software, and with the system expansion speed and flexibility using good multi-port digital/analogue modem cards.

A NT-based RAS system can start with one analogue modem on your COM1 port to take calls from the PSTN (Public Switched Telephone Network). This can be rapidly scaled up to a maximum of 256 ports per RRAS server, or for 48 demand-dial users, simply by adding more multi-line intelligent RAS cards. Smarter users will opt for high-density multi-port intelligent RAS (modem) cards such as those offered by Brooktrout Technology, instead of adding 4- or 8-port serial cards and more external modems. For example, Brooktrout’s ‘Instant-RAS’ IRAS-30 card offers any combination of up to 30 simultaneous analogue or digital channels with its intelligent ‘AnyCall’ technology.

A RAS system based on such multi-line RAS server modem boards often cost (port-for-port) 30-60% less than proprietary modular hotbox RAS solution, depending on whose research you read. IRAS cards offer unassailable speed of scalability - simply installing multiple cards in a single RAS server can take you from two to a couple hundred ports in minutes -- DIY-style. Proprietary RAS boxes often scale more slowly in 4-port increments.

- Using an open approach to your RAS challenge can enable you to exploit existing IT infrastructure. For example, you can easily add RAS cards to an NT server that hosts other network services, though you can’t get a hot-swap ability for RAS cards (but do you need it?). Fault tolerance is typically an advantage of a hotbox RAS solution, but some lack a redundant power supply, while a RAS service based on NT-servers could be configured using several RAS servers spread throughout the enterprise (or country) for added resilience.

- Open RAS or IRAS card solutions link into NT’s own services for security and management, including callback security, NT user authentication, multi-line connectivity and encryption - such as Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP).

- Within an Open RAS solution, WindowsNT’s RRAS includes the fixed dial-back security function, enabling your HQ’s RRAS server to dial back the specific phone number that dialled it and only then complete the network logon. This is in addition to a number of different encryption and authentication settings.

- Depending on the number of anticipated simultaneous dial-in users and their file transfer sizes, ensure that your RRAS server has sufficient bandwidth. While you could get away with a 10MB Network Interface Card (NIC) for perhaps, two or three users accessing files of a few hundred kilobytes, you probably need a 100MB NIC and an ISDN adapter for dozens of remote users simultaneously sending and receiving files of several megabytes each. Also consider then, the IRAS card which can handle both digital and analogue calls simultaneously and automatically, since you won’t always know which users or how many will be using which modem type. Also remember that unless one end of your connection (usually that at your HQ) has a digital (ISDN) adapter installed, your remote users will never get a faster analogue connection than 33.6Kbps - even if they do have the latest V.90 56k modem.

However, RRAS includes a Multi-link PPP feature that enables the multiplexing of two lines to achieve enough bandwidth to transform a 33.6Kbps (one-line analogue) connection into a 67Kbps (two-line analogue) connection. This is configured on the RRAS server. SOHO remote workers in the UK should ensure that BT has not put a DACS box on their domestic phone line - this multiplexes two domestic phone numbers onto one line, which limits connection speed of even a fast 56k V.90 modem to a mere 33.6Kbps or less.

This brings us to compression and connection costs. Microsoft’s Point-to-Point Compression (MPPC) provides file compression within RRAS. Independent tests have shown MPPC to double the file throughput of a WindowsRRAS-server-to-WindowsRAS client connection, when compared with a proprietary RAS solution. MPPC is the RRAS default compression algorithm, offering the automatic benefit of reduced call charges and increased file transfer speeds.

Tunnel your costs
- Tunnelling enables you create your own private connection using the Internet and to pay only a local call charge for long-distance connections. Using the same Point-of-Presence (POP) connection between your remote SOHO to ISP, it then entails changing your call connection protocol between your ISP to your RAS server using PPTP/VPN (Virtual Private Network). This then becomes a secure, encrypted ‘tunnel’ connection to your corporate RRAS server. This can be anywhere in the world - but it must have a leased line Internet connection. It also gives you the power of the Internet’s redundancy and universality.

This article was contributed by ComCat, High Wycombe-based supplier of Instant RAS boards, voice/ fax boards, Keyboard-Video-Mouse (KVM) switching and Computer Telephony Integration (CTI) products. www.comcat.co.uk and info@techland.co.uk

IRAS - Instant RAS; RAS - Remote Access Server
RRAS - Routing & Remote Access Service
RASP - Remote Access Service Provider.