Complied by Heng Sovannarith
The physical topology of a network refers to the configura@on of cables, computers, and other peripherals.
Physical topology should not be confused with logical topology which is the method used to pass informa@on between worksta@ons.
Logical topology was discussed in the Protocol chapter.
Topology - Physical and logical network layout Physical actual layout of the computer cables and other network devices
Logical the way in which the network appears to the devices that use it
Common topologies: Bus, ring, star, mesh, tree and wireless
Uses a trunk or backbone to which all of the computers on the network connect
Computers connect to this backbone using T connectors or taps
Coaxial cablings ( 10Base-2, 10Base5) were popular op@ons years ago
Bus Topology (cont.) Advantages Disadvantages
Easy to implement and extend. Limited cable length and number of sta@ons.
Require less cable If there is a problem with the cable, the en@re network breaks down.
Easy iden@fica@on of cable faults. Performance degrades as addi@onal computers are added or on heavy traffic
less expensive than other topologies Commonly has a slower data transfer rate than other topologies.
Cost effec@ve; only a single cable is used. Maintenance costs may be higher in the long run.
Ring Topology Meaning that data travels in circular fashion from one computer to another on the network.
Typically Fiber Distributed Data Interface (FDDI), Synchronous Op@cal Network (SONET) or Token Ring technology are used to implement a ring network
Ring networks are most commonly wired in a star configura@on Token Ring has mul@-sta@on access unit (MSAU),equivalent to hub or switch. MSAU performs the token circula@on internally.
Cable faults are easily located, making troubleshoo@ng easier
Moves, adds and changes of devices can affect the network
Ring networks are moderately easy to install
One worksta@on can create problems for the en@re network
Performs be]er than a bus topology under heavy network load
Bandwidth is shared on all links between devices
All computers/devices connect to a central device called hub or switch.
Each device requires a single cable. point-to-point connec@on between the device and hub
Most widely implemented Hub is the single point of failure
Easily expanded without interrup@on
Requires more cable to the network
Cable failure affects only a single computer
A central connec@ng device allows for a single point of failure
Easy to troubleshoot and isolate problem
More difficult to implement
Each computer connects to every other. High level of redundancy. Rarely used.
Wiring is very complicated Cabling cost is high Troubleshoo@ng a failed cable is trick
Mesh Topology (cont.)
Provides redundant paths between devices
Requires more cable than the other LAN topologies
Implementa@on without disrup@on to current uses
Tree or Extended Star
A tree topology combines characteris@cs of bus and star topologies.
It consists of groups of star-configured worksta@ons connected to a linear bus backbone cable.
Tree topologies allow for the expansion of an exis@ng network, and enable to configure a network to meet their needs.
Tree or Extended Star (cont.) Advantages Disadvantages
Point-to-point wiring for individual segments.
Overall length of each segment is limited by the type of cabling used.
Supported by several hardware and so`ware venders.
If the backbone line breaks, the en@re segment goes down.
More difficult to configure and wire than other topologies.
Do not require physical cabling Par@cularly useful for remote access for laptop users
Eliminate cable faults and cable breaks. Signal interference and security issue.
Wireless networking (cont.)
Allows for wireless remote access Poten@al security issues associated with wireless transmission
Network can be expanded without interrupt to current users
Limited speed in comparison to other network topologies
Considera@ons When Choosing a Topology
Money. A bus network may be the least expensive way to install a network.
Length of cable needed. The bus network uses shorter lengths of cable.
Future growth. With a star topology, expanding a network is easily done by adding another concentrator.
Cable type. The most common cable is unshielded twisted pair, which is most o`en used with star topologies.