Understanding the network.pdf - Back to Home

their destination, type, and content. Routers can look forspecific types of data, or
packets from a particular source or destination, and discard them. Packet filtering is
a popular form of network security.
Routers are a large element in LAN, WAN, and MAN network operations. Routing
protocols (how routers exchange network reachability information), router
configuration, and implementation will be dealt with at great length later in this
book.
NOTE
Joining different media types together can also be accomplished with a special
bridge called a translation bridge. Translation bridges repackage network data from
one media frame type to another. However, although a translation bridge will create
two collision domains, the broadcast domain is unaffected because the network's
structure is at least logically a single transmission segment.
NOTE
Broadcast storms happen when the network is saturated with collisions or broadcast
packets, and no data can be transmitted.
Data Communication Reference Models
Although each data communication protocol has its own operational reference
model, all are contrasted to the Open Systems Interconnect Reference Model
(OSI-RM) and the Institute of Electrical and Electronics Engineers (IEEE) model. The
OSI-RM is the basis for discussing the various elements of the data communication
process. The IEEE extension model defines the operational specifications for the
transport layer protocols.
An understanding of these models and their relationship to the logical computer
network elements, which was already covered, is crucial to forming an
understanding of internetworking. Protocol reference models exist to serve as road
maps to illustrate how the different protocols perform in relation to one another.
Computer networking hardware and software vendors use the definitions contained
in the reference models to ensure interoperability with other network elements.
Most of the basic elements of network design and implementation can be
accomplished without any detailed knowledge of the OSI-RM or protocols in general.
Network troubleshooting and network security and management, however, are
difficult without some understanding of the protocols in use and their
interrelationships.