In the World there is a lot of firms are doing business ,which have many branches in different countries and cities but these have only one HQ (head quarter ) .In the sence of security and safety purposes all the branches of the firm have to connected to the HQ all the time, So that the main server of HQ be updated all the time that whats happening in the branches.
To connect all the branches of any firm in different countries and cities is called WAN. There is many ways of WAN (wide area networking)
1.DXX
2.Radio links
3.VSAT
4.optical fiber
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