what is dial up modem

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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