General view of LANs
- A LAN or Local Area Network is a computer network (or data
communications network) which is confined in a limited
geographical area.
- Six types of LAN topologies: star, point to point, multipoint,
hierarchical, bus, ring.
- There are three basic types of cables: twisted pair, coaxial,
and fiber optic.
- OSI/ISO network standard model defines a foundamental representation
of networking. There are seven layers, each of which presents
a distinct functionality and interface of networking.
- The demands of multimedia have driven existing LAN standards being
modified. Also, extensive changes in communicating media coordinate
with advances in networking capabilities.
Ethernet
- Ethernet is one of the most commonly used network configuration.
- Network repeaters are used to extend trunk segments.
- Multiple access to the network is solved by CSMA/CD protocol, which
senses when the network is free and detects collisions.
Token Ring
- Network workstations are hooked up by some physical media into a
ring configuration. Data are transmited sequentially downstream.
- A special packet, called token, circulates the ring. Only the node
that possesses the token may transmit information. Token passing
is a collision-prevention scheme.
FDDI (Fiber-Distributed Data Interface)
- FDDI can transport data at 100 Mbps, can support up to 500 stations,
and can cover 2 kilometers in length.
- FDDI was designed to run through optic fiber cables. (It can also
run on copper using electrical signals.)
- FDDI network consists of two counter-rotating rings (one primary and
one secondary) to maintain a high reliability.
- FDDI network uses token passing to control all stations to share the
network bandwidth in an orderly and efficient manner.
- Some FDDI terminologies:
- Station: An addressable node on an FDDI network capable of
transmitting, repeating, and receiving information.
- A dual-attached station on the ring has at least tow ports -
an A port, where the primary ring comes in and secondary ring
goes out, and a B port where the secondary ring comes in and
the primary goes out.
- Concentrator: An FDDI node that has additional ports beyond
those required for its own attachment to the network.
Topologies (Star, Bus, Ring and Hierarchical)
Hierarchical
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