In its simplest form, a wide-area network (WAN) is a collection of local-area networks (LANs) or other networks that communicate with one another.
A WAN is essentially a network of networks, with the Internet the world's largest WAN.
A WAN operates beyond the geographic scope of a LAN.
WANs are used to interconnect the HQ LAN to remote LANs in branch sites and telecommuter sites.
A WAN is owned by a service provider.
A user must pay a fee to use the provider’s network services to connect remote sites.
WAN service providers include carriers, such as a MPLS network, telephone network, cable company, or satellite service.
Service providers provide links to interconnect remote sites for the purpose of transporting data, voice, and video.
In contrast, LANs are typically owned by an organization. They are used to connect local computers, peripherals, and other devices within a single building or other small geographic area.
Are WANs Necessary?
Without WANs, LANs would be a series of isolated networks.
LANs provide both speed and cost-efficiency for transmitting data over relatively small geographic areas.
However, as organizations expand, businesses require communication among geographically separated sites.
The following are some examples where we need wan.
Regional or branch offices of an organization need to be able to communicate and share data with the central site or HQ.
Employees who travel on company business frequently need to access information that resides on their corporate networks.
WAN Topologies
Interconnecting multiple sites across WANs can involve a variety of service provider technologies and WAN topologies.
There are four Common WAN topologies.
Point-to-point topology -:•Employs a point-to-point circuit between two endpoints
Hub-and-spoke topology -:•Applicable when a private network connection between multiple sites is required
Full mesh topology -:•With a full mesh topology using virtual circuits, any site can communicate directly with any other site.
Dual-homed topology -:•Provides redundancy and load balancing however they are more expensive to implement than single-homed topologies.
WAN technologies are either
Circuit-switched-: Such as PSTN or ISDN
Packet-switched. -:MPLS,Metro Ethernet WAN, ATM, or Frame Relay.
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