The connection types described in thefollowing table represent typical levels of service for full Internet connections. The Internet services offered through Internet service providers in your area may differ greatly. These figures are approximate and do not include the cost of required hardware.
| Connection |
Bits per second |
Simultaneous users supported |
Approximate monthly cost |
Modem |
28,800 |
5-10 |
Under $100 |
| Leased Line |
56,000-2,100,000 |
10-20 |
$150-300 |
| ISDN |
128,000-1,544,000 |
10-50 |
$70-100 |
| T1 |
1,500,000 |
100-500 |
$1,500-2,000 |
| Fractional T1 |
Varies as needed |
||
| T3 |
45,000,000 |
5,000+ |
$65,000-80,000 |
A light-duty server can use frame relay or ISDN. A server with medium traffic might have a T1 line or some fraction of a T1 line installed. Large businesses that expect heavy Internet traffic may need fractional or multiple T1 lines or even T3 service in order to handle thousands of users.
Traditional proprietary network service providers such as Prodigy, America OnLine, and CompuServe provide gateway services to the Internet. A gateway service does not provide a direct Internet connection, but a connection to a computer at the service provider's site which is connected to the Internet. However, with the tremendous growth and popularity of the Internet and the World Wide Web, all of these service providers are developing expanded Internet services. Even so, these services target consumers and are not appropriate for organizations interested in connecting their Web servers to the Internet.
Dial-Up Direct Connection service is available over a standard phone line and modem or through an ISDN connection. Modem connections use standard telephone lines, but require software conforming to either the SLIP or PPP standard. Although a computer with a SLIP or PPP connection has full Internet access, bandwidth over the fastest available modems is limited to 28.8 kbps. We do not recommend this type of connection to connect a Web server.
ISDN connection, on the other hand, requires a special telephone line, but offers higher speeds over a digital link and a better quality connection than with modems. The drawbacks to ISDN are that 1) the service is not available in all areas, 2) the data rate is limited to 128 kpbs, or 112 kbps in some locations, and 3) the Internet connection breaks when the dial-up connection is terminated. Although maintaining a constant connection over ISDN is possible, it may not be cost effective because users are typically charged based on usage. In general, ISDN connection is not recommended to maintain a constant connection to the Internet.
Dedicated lines are most appropriate for sites with a large number of users or with a lot of data to offer to other users on the Internet. Using a dedicated line connection, a Web server can offer a full-time, uninterrupted connection to the Internet, for a flat rate from an Internet Service Provider (ISP). This is the recommended type of connection for a company Web server. There are hundreds of ISPs that offer dedicated line access to the Internet. Most are small local or regional providers.
The appropriate bandwidth for customers will obviously vary, depending on their expected use of the Web. FRS Associates recommends at least a 56 kbps dedicated line connection for commercial Web servers. Bandwidth requirements can range upto multiple T-1 lines (E-1 in Europe), 10 mbps Ethernet connection (for internal web serving), a T-3 line (45 mbps), and even 100 mbps or higher on high speed internal FDDI, HPPI or ATM networks.
Calculating the amount of bandwidth required for a Web server is not at all an exact science. However, one can make estimates based on assumptions of:
This is the thought process: first, make a guess as to how many users will be making concurrent requests. Then determine whether or not you want to design the Web server to handle peak loads or some percentage of peak (which means that during peak times, server response will be slow and some users may not be able to access the system).
Second, make an assumption of the average size of file to be transferred based on the content that will be created for the server. A server with lots of multimedia content will have larger file sizes than one with mostly text. Finally, multiplying the number of simultaneous requests and average file size will provide an estimate of how much information must be transferred during peak periods (i.e. bandwidth required).
For instance, a JPEG image might consist of 150 kilobytes of information (or 150 * 8 = 1,200 bits). A dedicated T-1 link which transfers data at 1.544 mbps would transfer this in about a second (1,200 bits / 1,544 bits/sec = 0.8 seconds). On the other hand, if 100 people were trying to access images at once, the response time would be well over a minute, which might be extremely annoying to some customers. A movie file will take much more bandwidth to transmit quickly since each frame of the movie might use 150 kilobytes of information.
Another factor to consider in determining bandwidth is the type of transaction to be conducted. As mentioned earlier, transferring large images, audio or movie files can take a great deal of bandwidth to transmit quickly. On the other hand, online transactions and other services generally do not require much bandwidth. However, users will get annoyed much more quickly if transaction requests take too long.
For example, if users have to wait 30 seconds for an image to appear on the screen and they see the picture appearing as they wait, they don't become anxious. On the other hand, if users have to wait 30 seconds for a credit card transaction, they may worry that their transaction did not go through, or that their credit card number is flying around the Internet unprotected. Therefore, Web servers conducting financial transactions must be able to process requests much more quickly.
Hardware required for a typical dedicated line Internet connection include:
Except for the computer, all of the equipment listed above are usually available through an ISP for rent or for purchase. There are many companies that build routers: Cisco, Bay Networks, and 3Com are among the market leaders. CSU/DSU companies are too numerous to list. CSU/DSU functionality may even be built-in to a router as is with the Ascend Pipeline 130 product. If purchasing a router and CSU/DSU from a source other than the ISP, it is still a good idea to get recommendations from the ISP to ensure compatibility of equipment.
A connection to the Internet will come to your site in the form of a dedicated telephone line. The line then connects to a CSU/DSU. The CSU/DSU will have a connector for RS-232, V.35 or some similar serial connection to connect with the appropriate cable to a router. The router then connects to the Web server (typically via Ethernet connection).
The software required for a typical Internet connection for a Web server and Internet gateway are:
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