Dialup
A dialup is a WAN connection technique that is established using a modem and Active PSTN line. The modem dials a number that is attached to another computer at the destination end and establishes a connection capable of transfer a data. The modem and telephone lines are working as a data transfer medium.
Usually, dial-up connection is used as connectivity medium with ISP for internet services; user initiate a dialup connection, the modem dials a phone number of an Internet Service Provider (ISP) that is designated to receive dial-up calls. The ISP receives the call and then establishes the connection, which usually takes about 5 to 10 seconds and is accompanied by several beep and buzzers sounds.
History of Dialup Modem
A modem is an important object of the dialup network. The first modems were developed during the 1950s for military usage between North American Air Defense bases. These early modems were only available for military uses and the maximum data rate of these modems are 300bps.
In 1962, AT&T introduces the first commercial modem known as Bell 103. The maximum data sending rate of this modem is also 300 bps. The modem providing full-duplex transmission capabilities, along with a frequency shift keying (FSK) feature.
In the 1990s modem become a popular commercial technology. The majority of peoples start using the modem for internet and intranet connections. Dr Brent Townshend introduced the 56K Modem in 1996, which offered bandwidth of 56Kbps. At that time 56 Kbps speed was the fast internet connection for general peoples.
The Function of Dialup Modem
Dialup WAN connection is important when no other WAN technology is available. For example, a remote location, where an only telephone line is available, can use a dialup modem and analogue telephone lines for WAN connection. It is appropriate when irregular, low-volume data transfers are needed.
The dialup modem can transport binary data of computer through the voice telephone network. The modem does this using two technique, Modem = Modulate and Modem = Demodulate. It modulates the binary data of a computer into an analogue signal at the source and demodulates the signal back to binary data at the receiving side. The physical characteristics of the analogue lines limit the rate of the signal up to 56 kbps.
The dialup modem becomes popular due to the simplicity of analogue lines including availability, and low cost. The low data rates and relatively long connection time is the main disadvantages of dialup network connection. Due to dedicated circuit, the delay or jitter for point-to-point traffic become less, but it is not a better solution for real-time traffic like voice and video calls, online gaming, etc.
At present very only some enterprises maintain dialup access, it is still a feasible solution for remote areas with limited WAN access options. For small enterprises, dialup connections are enough for the exchange of sales figures, prices, and reports. It is also enough for email service at remote locations.