As we saw before, these networks are collections of widely scattered computers connected by a common communication network. Communication in such systems is relatively slow (9.6 to 56 Kbps) and unreliable and typically through telephone lines, microwave links, and satellite channels.
Long-haul networks provide several services to their users:
The ability to mail information from one site to another.
The ability to post news on bulletin boards, which may be read by any user on the system.
The ability to find information about users on different computers through services such as finger.
The ability to copy files from one system to another.
The ability to logon at a remote site. The local computer directs user input to the remote site and displays output received from the remote computer.
WWW access.
The notion of a long-haul network requires the ability to communicate among
remote processes.
It also requires schemes such as replication/caching
for overcoming the lack of speed and reliability
of the network and also the absence of a global clock.
It does not, however,
require a special organization and any operating system that
communicate across the network can offer these services.