4.2.6 SLIP and PPP

Ethernet connections are not always practical for computers at a distance, or when network-

ing hardware is not available. A common alternative is to use a serial connection, such as a tele-

phone modem. Network data packets are passed using a protocol such as Serial Line Internet

Protocol (SLIP) and Point to Point Protocol (PPP).

At present the alternatives for data transfer are listed below. This is a short list, but it can be

expected to grow quickly over time.

Phone lines with modem (dial up) - this runs at speeds up to 56Kbaud, with a peak data rate of about 3KB/sec. These are used for network connection that lasts from a few minutes to hours. This is very widespread and universally supported, but expect this 40 year old technology to be phased out over the next decade.

Direct serial connection - this can be done with a direct connection between serial ports on two computers using SLIP or PPP. The peak rates can reach over 6KB/sec. This method can also be done using a low speed radio modem.

Direct parallel connection - this is done by connecting the parallel ports on two computers together and using Parallel Line Interface Protocol (PLIP). Data rates approaching 1MB/sec are possible.

ISDN - Integrated Services Digital Network (ISDN) uses dedicated phone lines that