Enumerate the various internetworking facility

1.) Give a link among networks. At minimum, a physical and link control connection is required.  

(2) Provide for the routing and delivery of data among processes on dissimilar networks.

(3) Provide an accounting service that keeps track of the use of the many networks and routers and handles status information.

(4) Provide the services just listed in such a way as not to need modifications to the networking architecture of any of the constituent networks. This means that the internetworking facility must accommodate a number of differences between networks.