These questions are old, dating back to the early 2000s, so pardon some of the dated material. Enter some of your own questions here to be answered and we'll see if I or someone else can provide some more up-to-date topics.

If you are providing dial-up service, you need one line for each subscriber on-line simultaneously. For example, a small ISP with 96 phone lines can typically sell eight subscriptions for every phone line (an 8:1 ratio), thus serving about 768 subscribers. An 8:1 ratio means that one out of every eight subscribers is expected to be on-line at any given time. With digital lines, you will order blocks of 24 (T1 or PRI in North America) or 30 (E1 or PRI in Europe and elsewhere). ISP Ltd. will help you determine the proper number of lines for your projected subscriber base.

Your IP addresses come from the backbone provider (unless you are a large ISP, in which case you wouldn't be reading this). In most countries, the addresses have no additional cost over your backbone connection.

In the USA and Canada, the cost of a T1 wire from your telephone company will run $700 to $1,500 per month. For the backbone (Internet) connection, you will further need that T1 line to run to your backbone provider, which will cost an additional $500 to $2,000 per month. ISP Ltd. will assist you in obtaining these lines.

A T3 line to the Internet will run anywhere from $17,000 to $45,000 per month, including the backbone fee.

Satellite may be a good choice for areas where there is no other high-speed service, but the cost is generally much higher in North America than wired service. In Africa, satellite is often the less expensive choice with the exception of the cost of the Earth Station. Dedicated two-way satellite service runs from around $3,500/month for 128kbps to over $10,000/month for 512kbps. Typically you will need to pay for the first 3 months in advance along with some setup fees. Satellite equipment (the Earth Station) costs around $30,000 to over $60,000 to purchase.

An ISP that implements a wireless network has a chance to own their own infrastructure, which is virtually impossible in the wired networking arena. As you can probably imagine, placing your ISP on an equal level with the telco has tremendous potential and advantages.

In addition to owning your infrastructure, going with wireless provides the opportunity to offer broadband access with the limitations and requirements of such technologies as xDSL. Most often, wireless access points can reach subscribers 20km (12 miles) away compared with xDSL's ~3km (2 mile) limitation.

Although implementing a wireless network involves construction that is not required when using the telco's infrastructure, the potential pay-off dwarfs that of wired technologies. Add VOIP to this scenario and your ISP suddenly can offer services approaching those of the telco.

You can read a March 2002 ISP Planet article regarding this topic here.

A GNU/Linux-based router is the most flexible and cost-effective solution. Your backbone provider may recommend and wish to rent you a proprietary router. This is fine if you have a system administrator who knows how to operate it; otherwise decline their offer and stick to a GNU/Linux router.

The advantage of using a GNU/Linux router is that the system administrator does not need to learn the management software of the router. As your ISP grows, the GNU/Linux router can be scaled upward with no change in operating procedure.

The advantage of using a proprietary router on very large systems is that the data transmission speed can be better since large routers integrate the fibre-optic WAN port into the same unit.

You could use one computer and two modems to create the world's smallest ISP. It would be a fun experiment or hobby, but as a business it is a dead end, not a starting point.

To operate an ISP with any profit requires at least 48 analogue lines and at least 350 subscribers, operated by one person. With more than one person or higher-cost digital lines the revenue needs naturally increase.

DSL is a fine starting point, but remember you will have to get a resale contract (a home DSL account will almost certainly not allow you to resell the bandwidth). In general, DSL is only suitable for relatively small numbers of subscribers (perhaps as many as one thousand, depending on the speed of DSL service you get and the speed you offer to subscribers).

Frame relay is a burst data transmission method, as opposed to T1 which gives you the full bandwidth all the time. With a 1.5Mbps frame relay line, your actual bandwidth could be well under the full T1 line speed. On the other hand, if your telco has an under-utilised circuit using frame relay could give you T1 speeds for less money.

SCSI is still the speed champion, although you might not think so by reading marketing hype.

In a given server, the actual speed you get from a hard disk depends on head speed, rotational speed, data density, interface speed, and host adapter speed. In the real world (as opposed to “on paper”), PATA and SATA offer the same speed; the potential of SATA (let alone SATA-2) have not materialised. A hard disk drive with a 100Mb/s ATA/100 interface will most likely yield the same throughput as the same drive with a 1.5Gb/s SATA interface.

If you read the full specifications of hard disk drives, you will see that PATA and SATA drives both have the same maximum sustained data rate, which is generally between 30 and 60 megabytes per second. SCSI drives, on the other hand, have an approximately 50 percent higher maximum sustained data rate of 60 to 90 megabytes per second. While SCSI host bus adapters have an interface speed of 320 megabytes per second, SATA has a maximum speed of 150 megabytes per second, but as you can see, both of these far exceed the potential of today's hard disk drives. In addition, many systems which use the same chipset for PATA and SATA interfaces do not actually provide the speed potential of SATA.

The average access time is the average time it takes for the heads to position themselves on a desired track and sector. For ATA drives this figure is around 10 milliseconds, some drives are as low as 8.9ms. SCSI drives are two to three times faster – generally around 4 milliseconds with some drives approaching 3ms. However, placing SATA drives in a RAID-5 or RAID-10 configuration can nearly make the two equal.

If you need maximum speed and reliability from every drive, use SCSI/SAS. If you want the most storage possible, will be placing the drives in a RAID-5 or RAID-10 configuration, and/or want to keep spending down, then ATA drives are the right choice.