Network resources in SNA are managed (that is, known and operated) from a central point of control that is aware of all the activity in the network, whether a resource is operational, and the connectivity status of the resource. The resources can send reports on their status to the control point. Based on networking and
organizational requirements, a hierarchical network can be divided into sub-networks, where every sub-network has a control point with its controlled resources.
We can use an airport control tower as an example to explain the centrally-managed approach. All airplanes in the control tower sphere of control (a sub-network) are controlled and report to the control tower. The control tower also "operates" the resources (airplanes and runways) by granting landing and takeoff authorization.
In a peer network, every resource is self-contained and controls its own resources. Most of the time a networking resource in a peer network is not aware of its network peers, and learns about their existence when it starts to communicate with the peer resources. We can use a Windows workstation as an example. We define only the local network of the workstation.
A national real estate franchise is good illustration of a peer network. Every local real estate office maintains the listing in its area and is not aware of the information stored in other offices. If a customer who plans to relocate asks for service from the local office, the office will call (connect to) the office in the city his customer plans to move to and get the listing from the remote location. If the customer had not made this request, the local office would not be aware of the remote office, and would learn about the remote office only when there was a need to access data that was stored remotely.
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