Choosing an ISP

Choose a dial-in Internet Service Provider (ISP) by the subscriber to modem ratio and service capacity. Price should be the last criteria for choosing an ISP.

Modem ratio

Modems are the devices that connect to the phone lines to allow data communications between computers. ISPs install multiple modems into groups called modem banks or modem pools. This group of modems services one or more dial-in phone lines used for subscriber access to the Internet.

Similar to the telephone company, all ISPs overbook the number of subscribers using the modem pool at any given time. This system works well because not every subscriber is using a connection at any given time.

The symptom of over-use for the phone company is the "all circuits are busy" message that is occasionally received during peak holiday calling times. For Internet users, this symptom is a busy signal.

At the peak of its subscriber problems, America Online had a ratio of 80:1 subscribers for each modem. When one subscriber was online, 79 others received a busy signal. Significantly better modem ratios are available from regional competitors.

The ideal modem ratio in the real world is 9:1 or less. This means that only 8 subscribers will receive a busy signal while the 9^th user is online. In practice, a modem ratio of 9:1 rarely presents the user with busy signals.

Modem Hardware Selection

Prior to the adoption of the V.90 standard, 56k modems were available in the X2 and K56flex technologies. These technologies are mutually incompatible. Subscribers purchasing an X2 modem would find themselves at odds with an ISP using the K56flex technology.

Today, the V.90 standard for 56k modems is in place. Despite the adoption of this standard, high speed modem communication is still fragile. The subscriber can reduce compatibility issues by using the same type of modem that is used by the ISP.

This does not mean other modems won’t work. It simply means that if the subscriber has not yet purchased a modem, buying the same type as used by the ISP will reduce potential compatibility problems between modems. Contact the ISP for their modem recommendation.

Service Capacity

Bandwidth is the size of the data ‘pipe’ the ISP uses to connect the subscribers to the Internet. Similar to modem pools, bandwidth is also over booked. The ISP depends upon subscribers not being online constantly. This is the reason many ISPs automatically disconnect users who show no activity after a short period of time. Camping out ties up both an ISP modem and a telephone company dedicated circuit. This abuse of flat-rate Internet access is a growing concern for both telephone companies and ISPs.

A T1 line is advertised as 1.544000 Mbps but is spec'ed as 24 x 64kbps DS-0 channels, or 1.536000 Mbps. The missing 8Kbps is the minimum required for framing and control bits need to keep the T1 working end to end. These bits are exclusively used by the T1 control circuits and not available as user bandwidth.

To further muddy the waters, 1.536 Mbps is available only from a B8ZS framed T1, which is not available from many TelCo providers. A T1 purchased from PacBell will default to 24 X 56kbps lines, or 1.344 Mbps. By FCC mandate, the maximum connect speed is 53,000 bps. The math resolves to a T1 supporting a maximum of 25 simultaneous users at full bandwidth.

A T3 connection consists of 28 T1 circuits. In theory, a T3 installation will support 710 users (25 users * 28 circuits) simultaneously transferring data at 53 Kbps. Large providers use fiber optics and multiple T3s to achieve sufficient bandwidth for their needs.

In practice, the number of users supported by a T3 facility is substantially higher than the theoretical maximum. Internet users spend most of their time reading screens rather that transferring data. While users read their screens, they are not consuming bandwidth. When one user pushes a screen button, another user is idle and not consuming bandwidth while reading their screen.

The ideal is realized when multiple users make data requests between each other. One user requests data while the others are reading their screens or typing. The Internet slows to a crawl when the number of users requesting data exceeds the available bandwidth.

Total Connections

The ISP must provide sufficient bandwidth to support Internet access to web sites hosted on the ISP’s computers. A popular site can receive hundreds of thousands of accesses each day and will consume bandwidth accordingly. The number of simultaneous connections to the ISPs computers far exceeds the maximum number of dial-in modem lines.

The ISP must have sufficient hardware processing power to accommodate both external Internet access and local subscriber dial-in lines. High capacity ISPs will use many industrial-strength, multi-processor UNIX machines to handle this type of load. Many UNIX installations can accommodate more than 20 processors in a single computer.

Ease of Access

Larger ISPs have points of presence (POPs) located throughout a geographic area. Some are statewide, others provide POPs on a nation-wide basis. These ISPs allow their subscribers to have local access outside of their local area. Many hotels provide data jacks in their telephones to provide business travelers Internet access from their hotel room for the price of a local call.

Price

Avoid choosing an ISP primarily by price. The pleasure of a low price will soon give way to the pain of chronic busy signals, poor service, and non-existent technical support.

A low price does not necessarily signify a poor product, nor does a high price guarantee excellence. Users paying a premium price for Internet services from telephone companies often report more problems than those experienced with regional ISPs.