Is broadband the technology you can't do without or an expense you don't need? We examine the alternatives, pitfalls, myths, and benefits.

Traditional 56K modems and ISDN just don't cut it any more. Compared with the speeds we're all used to over a LAN, these connections seem snail-paced. ISDN is also not what we'd call cheap, especially compared to some of the new broadband options available.

So what exactly is broadband? It depends who you ask. In general, "broadband" refers to telecommunication in which a wide band of frequencies is available to transmit information. Because a wide band of frequencies is available, information can be multiplexed and sent over many different frequencies or channels within the band concurrently. This allows more information to be transmitted in a given amount of time.

So far so good, but when you start trying to define how much throughput makes a connection broadband, that's when the fun begins.

There are various definitions of what actually constitutes broadband. They usually range from 256Kbps up to IBM's definition of a broadband channel being 6MHz wide (this is around 2000 times an average voice-grade line). Under this definition, ADSL and cable would be considered broadband--at least in the downstream direction. However, Telstra claims anything faster than 128Kbps is broadband, and as a consequence even its basic two-channel ISDN service sneaks into its realm.

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Assessing the options

Availability for broadband is still a big issue, and some locations may have very few options available to them.

Cable rollout has pretty much stalled. ADSL only works up to a set distance from your local exchange, and even then only if the exchange is equipped with a DSLAM.

So how can you tell which options are available in your area?

Most of the vendors include a search tool to confirm that your address is able to access their service. For example, the Telstra Cable search tool is located at http://www.bigpond.com/broadband/cable/CableSQ.asp .

Even if this search comes up as positive, don't get too excited. Technical issues can sometimes affect even an individual building or phone line, meaning you may not be eligible. It also pays to check that the vendor's acceptable usage policies are going to allow you to use the service in the way you wish. For instance, the Optus@Home policy is available at www.optushome.excite.com.au/obligations.html. Calling it "@Home" is a bit of a giveaway that this service is not available for business use--the entire Optus cable system is for residential use only. However, after long and enlightening conversations with Optus' technical staff, the story is not as dire as one might imagine.

Optus appears to have no problem with customers taking out the service in their own name and then working from home with say their employer footing the bill--as long as the billing address is Joe Bloggs c/o Company Z. Optus staff told us that quite a few Web designers run their business over Optus cable quite happily, and it's OK to run a Netware client, for example, so you can log into your work server. However, you cannot run FTP servers and the like.

What are the different technologies?

ISDN

The important thing to note is that ISDN is point-to-point and as a consequence is very secure; it also allows the user to run VPN.

A new flavour called Broadband ISDN (BISDN) will utilise fibre optic and wireless technology and encompass a frame relay service for large bursts of high-speed data. BISDN will support transmission rates from 2Mbps and above.

There are some important factors to remember when considering ISDN. While your monthly line rental is only the same as two phone lines, there is also a capped data charge per month (it is a permanent connection so there are effectively no per-call charges). This capped charge is based on distance and is more expensive in country areas, but can typically start at around AU$440 per month in the city.

Because ISDN is point to point, an ISP cannot just tap into your line--you must set up a dedicated ISDN line that terminates at your ISP, which will levy a monthly charge on top of the capped monthly charge of your carrier.

A final detail to be aware of is that although ISDN connections use a standard RJ-45 connector, if you happen to plug a PC or switch into the connector by accident, the 100V ISDN connection will not be very friendly to your equipment.

ADSL

The asymmetrical nature of ADSL stems from the fact that the downstream channel steals the major part of the bandwidth. For example, the downstream channel may be 256Kbps while the upstream channel is only 64Kbps. In common with cable, the asymmetric nature of ADSL exploits the fact that when surfing the Web, for instance, most of the multimedia information flows downstream to the user.

ADSL simultaneously accommodates an analogue voice channel on the line by dividing up the copper wire's 1.1MHz frequency spectrum. There are a couple of caveats: the bottom 4KHz is reserved for POTS and the amplification on the POTS segment is not the same over the various frequency ranges. There is a large guard band or separator between the POTS and data bands with the data consisting of 256 4KHz frequency domains from 64KHz to 1.1MHz. This separation of frequency domains is known as Discrete MultiTone (DMT).

Even though ADSL uses your existing POTS copper pair, it is not simply a matter of plugging in an ADSL modem and off you go. At your local exchange, which must be less than 3.5km away for ADSL to work, your copper pair is unplugged from the POTS and plugged into a DSLAM (Digital Subscriber Line Access Multiplexer).

Obviously in many rural areas you will be very lucky to be this close to an exchange, so in many cases ADSL may not be available (presuming of course that the local exchange does in fact have a DSLAM).

While we're on the subject of DSLAMs, many ADSL providers actually resell access to Telstra's infrastructure. However, this is changing as more and more providers, such as Pacific Internet, are renting space at Telstra's exchanges and installing their own DSLAMs. (Pacific Internet advised ZDNet Australia  subsequent to publication of this article that they were not undertaking this activity.) Other providers that are also rolling out their own DSLAMs include XYZed (which has over 100), RequestDSL (over 30), iPrimus (around 20), and AAPT.

Basically, ADSL speeds range from 256Kbps to 6Mbps downstream and 64Kbps to 640Kbps upstream. As you effectively have your own dedicated line, this performance is pretty much assured. At some of the higher data rates, though, the price can rise quite dramatically.

HDSL

There are vendors offering HDSL in Australia at the moment. However, they don't widely promote it as the infrastructure is so limited that many potential customers are likely to be disappointed by the lack of support in their area. The CBDs of capital cities such as Sydney, Melbourne, and Brisbane have HDSL service but it is limited to just 1.9km from an enabled exchange. Telstra is the only provider of the service, but does not sell directly to end-users, instead wholesaling it to other vendors.

SHDSL

Yet another DSL, Symmetrical High bit rate Digital Subscriber Line (SHDSL) is also known as G.SHDSL and G.991.2. It has the distinction of being the first of the DSLs to have been designed from the ground up as an international standard.

This has been a fairly new development as the standard ITU G991.2 was only defined in February this year. Like the other DSL technologies, SHDSL sends and receives symmetrical data streams over a single copper pair at rates between 192Kbps and 2.31Mbps. SHDSL also has the ability to transport T1, E1, ISDN, ATM, and IP signals.

Because of the symmetrical nature of this technology and its high speed, it is better suited to the needs of remote LAN access, Web hosting and videoconferencing, for example. It also has the ability to transport multiple voice and data channels simultaneously.

LMDS

Even though LMDS involves the installation by the service provider of relatively expensive transmitters, and the purchase of a transceiver by the user, LMDS can potentially be a less expensive alternative to installing optic fibre or cable.

Depending on the implementation, LMDS offers a bandwidth of up to 1.5Gbps downstream and 200Mbps upstream. However, a more typical data rate is 38Mbps downstream--still a good deal faster than typical ADSL or cable implementations.

The service should be available in both symmetrical and asymmetrical formats and may only be offered with downstream capability, in some cases with the slower upstream connection provided over a phone line.

LMDS typically uses the frequency range around 28GHz, although the precise allocation range differs from country to country. Even though LMDS is similar to cellular phone technologies, it is not viewed as a replacement for GSM, for example. It is however seen as a component of the convergence of data and telephony services.

Satellite

However, Telstra is about to introduce a two-way satellite broadband service. The satellite dish for this service will have to be aligned very accurately--you are after all trying to hit a target a few metres across from 36,000km away.

Security is a fairly large issue with satellite, because the signals are relatively easy to tap into. Considering this, all the vendors utilise some form of encryption on the data stream. Telstra's Satellite Internet download is provided through a secure system and uses 56-bit DES (Digital Encryption Standard). The data is encrypted with unique keys preventing other members of the network, who use a different key, from listening in.

Satellite has a far greater latency or delay than most terrestrial systems. This is because the signal must travel 36,000km out to the satellite and then 36,000km back again resulting in around a half-second delay. This will not matter in most business applications as they are not time critical.

However, the delays are noticeable--for instance, Web pages take longer than you expect to start downloading, but go very quickly once they've started. Because of this delay, and other more pressing technical issues, some services--notably Telstra's two-way satellite--do not support videoconferencing, although Telstra says it will do so in the near future. There will still be a half-second delay (the speed of light being fairly constant) but the other technical problems will be resolved.

Satellite downstream speeds range from 64Kbps up to 400Kbps. Telstra's proposed two-way satellite service will also include a 64Kbps upstream as well.

The satellite dishes required are nowhere near the size of those huge ones on the top of buildings. The size of the dish depends on your location; while Telstra claims to cover the entire country, the satellite footprint means some areas have weaker signals than others. Also, if you live in the tropics, a really heavy downpour can attenuate the signal so you may need to install a larger dish to compensate. The dish typically ranges in size from a tiny 65cm up to around 1.2 metres--most urban and rural users will get a way with the smaller dish.

As a rule of thumb, those in the extremities of Australia such as the far north, southern WA and Tassie for example are probably going to need the larger dish. Naturally a larger dish will cost you more.

While Telstra covers all of Australia, many of the other satellite providers' coverage is nowhere near as extensive. Netspeed for example currently only covers Canberra and southern NSW.

As a part of the federal government's Special Digital Data Service Obligation, Broadband powered by satellite users who are unable to get access to a basic rate ISDN service, may be eligible for a 50 percent rebate off the cost of purchase and installation of satellite equipment, capped at $765. Typically, outback and remote customers are eligible for this rebate.

Cable

Cable modems use the Hybrid Fibre Coaxial networks laid by cable TV providers to transfer data at broadband rates. Although a cable modem modulates and demodulates between the analog cable medium and your PC's digital signals, it is a far more complex technology than a telephone modem.

A cable modem has two connections, one to the cable wall outlet and the other to your PC. The cable modem can be either an external or internal device with the former connecting to your PC with either the USB port or 10BaseT Ethernet. And, like ADSL, the cable modem is permanently connected to the network.

It's common knowledge that the speed of your cable modem depends largely on how many subscribers on your street (or in your node of the network) are currently online, as you all share a chunk of bandwidth. So, the more users online, the smaller your chunklet will be.

However, it is a misconception that the cable TV subscribers on your street also steal your cable modem's bandwidth: the different services within the physical cable are frequency divided. Your cable modem's upstream and downstream channels each have a dedicated frequency band that is completely different from the frequency bands allocated to cable TV.

Vendor-quoted cable speeds range from 256Kbps to 2Mbps downstream and 64Kbps to 128Kbps upstream--obviously the reality depends on the time of day you use the service and the load or number of subscribers connected at the time.

Some vendors, such as Optus, are hesitant to give firm download speeds but from other sources we are under the impression that it is in the region of 2Mbps. It is interesting to note that the DOCSIS standard--currently used on Optus' and Telstra's networks--allows for maximum cable speeds up to 10Mbps.

Leased line

The alternative is to buy and maintain their own private lines or, as is becoming increasingly more common, to use the public switched lines with secure message protocols or tunnelling.

Common leased lines options are T1 (aka DS1) which is a dedicated phone connection consisting of 24 individual channels, each of which can carry 64Kbps, giving a total bandwidth of 1.5Mbps. Each channel can be configured to carry voice or data traffic.

Another option is T3 (aka DS3), which is a beefier version of T1 and comprises 672 individual channels for a total capacity of 43Mbps. Both are popular amongst ISPs and the backbone of the Internet itself is made up of faster T3 connections.

Leased lines are not an inexpensive option, as you might guess, although prices have dropped over the years. A fibre-optic link at 10Mbps would cost between $4000 and $6000 to install and $800 a month in rental.

3G

3G is a term for third-generation wireless, and refers to up and coming developments in personal and business wireless technology, especially mobile communications. 3G is not expected to mature for up to four years. It is claimed 3G will provide data speeds of up to 2Mbps, although these claims are currently treated with some scepticism.

A bit of background on the technology: the first generation of wireless began in the late 70s and included cellular mobile phones using analog voice capability. The second generation is the one we are familiar with today and includes CDMA, TDMA, and GSM. Since its inception, 2G has improved with increased bandwidth and the introduction of multimedia capabilities through technologies such as GPRS and EDGE.

3G is effectively going the whole hog, supporting enhanced multimedia, e-mailing, fax, videoconferencing, and Web browsing. 3G will operate around the 2GHz frequency band and have a high degree of routing flexibility, so much so that eventually you should be able to roam all around the world and stay linked to the network. That's not to say it will be solely a mobile solution; it is also relevant to fixed wireless applications.

Rumour mill

Why is it that ADSL has been relatively unreliable? The scuttlebutt points to various problems. The first is the incompatibility between products from various vendors such as Cisco, Nortel, Alcatel, and Lucent that Telstra has liberally sprinkled around the network. This does not appear to be Telstra's fault: Telstra supplied all the vendors with very precise specifications that in some cases do not appear to have been adhered to.

The second possible cause is that many years ago, when the current digital industry was almost a twinkle in someone's eye, our telephone systems were experiencing all sorts of problems such as fade out. To correct this problem, tweaks were made to the copper wire by adding resistors, transformers and the like, literally millions of them, and now no one knows exactly where they all are. Admittedly the tweaks improved analog telephony, but they play havoc with modern ADSL.

Some vendors claim these two suggestions are just fluff, and the real reason for the ADSL problems is that the authentication servers are unable to cope with the load.

Broadband terminology

ATM: ATM (Asynchronous Transfer Mode) transfers data in small fixed-sized cells or packets. The small and even cell size allows ATM to transmit video, audio, and data without any one type of data hogging the connection. Currently ATM supports transfer rates up to 622Mbps. It differs from TCP/IP transport in that ATM creates a fixed channel between two points and all data therefore takes the same route while TCP/IP packets may take different routes to get to the destination.

While this may make ATM easier to track and bill, it does not have the flexibility to handle sudden changes in the network traffic as well as TCP/IP does. There are four main types of ATM:

• CBR: Constant Bit Rate.
• VBR: Variable Bit Rate provides a specific capacity but the data is not a steady stream, this is typically used for voice and videoconferencing.
• UBR: Unspecified Bit Rate has no guaranteed throughput levels which may be ideal for data such as file transfers etc that are not effected by delays.
• ABR: Available Bit Rate guarantees a minimum capacity but higher capacities are available when the network load is light.

DSL: Digital Subscriber Line.

DSLAM: Digital Subscriber Line Access Multiplexer.

E1: E1 is a European format and is similar to T1 although it has slightly higher bandwidth with 32 x 64Kbps channels for a total bandwidth of 2.048Mbps.

HDSL: High bit-rate DSL.

ISDN: Integrated Services Digital Network.

LMDS: Local Multipoint Distribution System.

PSTN or POTS: Public Switched Telephone Network is the worldwide conglomeration of public telephone infrastructure and is often known as POTS (plain old telephone service).

SHDSL: Symmetrical High bit-rate DSL.

TCP/IP: As the name suggests it's in two parts-IP or Internet Protocol, which defines the packets and addressing scheme, and TCP (Transport Control Protocol), which is a higher order protocol that establishes a connection between two hosts and guarantees the delivery of data packets and the delivery order.

VPN: A virtual private network (VPN) is a private data network that makes use of the public telecommunication infrastructure, maintaining privacy through the use of a tunnelling protocol and security procedures. The idea of the VPN is to give companies the same capabilities as a leased line at much lower cost by using the shared public infrastructure rather than a private one.

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