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dial-up modem

Dialup

Dialup

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Dialup is a WAN connection technique established using a modem and Active PSTN line. The modem dials a number attached to another computer at the destination end and establishes a connection capable of transferring data. The modem and telephone lines work as a data transfer medium.

Usually, a dial-up connection is used as a connectivity medium with an ISP for Internet services; the user initiates a dial-up connection, and the modem dials an Internet Service Provider (ISP) phone number designated to receive dial-up calls. The ISP gets the call and establishes the connection, which usually takes about 5 to 10 seconds and is accompanied by several beep and buzzer sounds.

History of Dialup Modem

A modem is an essential object of the dial-up network. The first modems were developed during the 1950s for military use between North American Air Defense bases. These early modems were only available for military use, and their maximum data rate was 300bps.

In 1962, AT&T introduced the first commercial modem, Bell 103. This modem’s maximum data-sending rate is also 300 bps. It provides full-duplex transmission capabilities and a frequency shift keying (FSK) feature.

Modems became a popular commercial technology in the 1990s. Most people started using modems for internet and intranet connections. Dr Brent Townshend introduced the 56K Modem in 1996, which offered a bandwidth of 56Kbps. At that time, 56 Kbps speed was the fastest internet connection for general people.

The Function of Dialup Modem

Dialup WAN connection is essential when no other WAN technology is available. For example, a remote location where only a telephone line is available can use a dial-up modem and analog telephone lines for a WAN connection. It is appropriate when irregular, low-volume data transfers are needed.

The dialup modem can transport computer binary data through the voice telephone network. The modem does this using two techniques: Modem = Modulate and Modem = Demodulate. It modulates the binary data of a computer into an analog signal at the source and demodulates the signal back to binary data at the receiving side. The physical characteristics of the analog lines limit the rate of the signal up to 56 kbps.

Dialup modems became popular due to the simplicity of analog lines, availability, and low cost. The main disadvantages of dialup network connections are the low data rates and relatively long connection time. Due to the dedicated circuit, the delay or jitter for point-to-point traffic became less, but it is not a better solution for real-time traffic like voice and video calls, online gaming, etc.

At present, only some enterprises maintain dial-up access. However, it is still a feasible solution for remote areas with limited WAN access options. Dial dial-up connections are enough for small enterprises to exchange sales figures, prices, and reports and for email service at remote locations.

WAN Devices

WAN Devices

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There are many types of specially designed WAN devices used in networks. These devices require expert skills for configuring and management. The important WAN devices are:

Dialup modem

Dialup Modems allow digital data to be sent over an analogue medium during the transmission and receiving of information. The dial-up modem is a legacy WAN technology. It is a voice band modem that converts the digital signals of a computer into voice frequencies that can be transmitted over the analogue lines of the public telephone network. At the destination end, another modem converts analogue signals back into digital signals for input to a computer or network devices.

Access server

An access server is very important among WAN devices. It may have a combination of analogue and digital interfaces. The access server gives dial-in and dial-out rights and supports hundreds of real-time users.

Broadband modem

It is a modem used to connect cable or DSL internet service to the computer or network devices. Both cable and internet services work in a similar way to the dial-up modem. The difference between the broadband modem and dial-up modem is frequency and speed. Broadband modem uses high frequencies and provides high transmission speeds.

CSU/DSU

CSU means Channel Service Unit and DSU means Data Service Unit. Digital-leased lines require a CSU and DSU. It can be a separate device like a modem or it can be an interface on a router. It is used for monitoring clocking and frame synchronization on digital lines. It also performs error detection at the physical layer.

WAN Switch

It is a multiport internetworking device that is used by carrier networks. The device is working on layer 2 and usually switches traffic, such as Frame Relay, or ATM. PSTN switches may also be used within the cloud for circuit-switched connection like ISDN.

Router

It provides internetworking between the Local Area Network (LAN), and Wide Area Network (WAN) access interface ports that are used to connect to the service provider network. The interfaces may be Ethernet, serial interface or WAN interface. Some WAN interfaces required analogue modem, cable modem or DSL modem to connect the router to the local service provider.

Core router

A router installed within the middle or backbone of the WAN is known as a core router. To perform this role, a router must be able to support multiple telecommunications interfaces of the highest speed used in the WAN core. The router must be able to forward IP packets at full speed on all of those interfaces and also required to support the routing protocols being used in the core.

Multilayer switch

A multilayer switch that installed within the middle or backbone of the WAN. It is working just like the core switch. The switch must be able to support multiple telecommunication interfaces like core router. It is the replacement of the core router.

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