Page 90 - DCAP104_EXPOSURE_TO_COMPUTER_DISCPLINES

Unit 5: Operations of Network

Protocols related to TCP/IP include the User Datagram Protocol (UDP), which is used Notes
instead of TCP for special purposes. Other protocols are used by network host computers for
exchanging router information. These include the Internet Control Message Protocol (ICMP),
the Interior Gateway Protocol (IGP), the Exterior Gateway Protocol (EGP), and the Border
Gateway Protocol (BGP).
5.2 Network Topology

Network topology is the layout pattern of interconnections of the various elements (links,
nodes, etc.) of a computer network. Network topologies may be physical or logical. Physical
topology means the physical design of a network including the devices, location and cable
installation. Logical topology refers to how data is actually transferred in a network as opposed
to its physical design. In general physical topology relates to a core network whereas logical
topology relates to basic network.
Topology can be considered as a virtual shape or structure of a network. This shape does
not correspond to the actual physical design of the devices on the computer network. The
computers on a home network can be arranged in a circle but it does not necessarily mean
that it represents a ring topology.

Any particular network topology is determined only by the graphical mapping of the
configuration of physical and/or logical connections between nodes. The study of network
topology uses graph theory. Distances between nodes, physical interconnections, transmission
rates, and/or signal types may differ in two networks and yet their topologies may be identical.

A local area network (LAN) is one example of a network that exhibits both a physical topology
and a logical topology. Any given node in the LAN has one or more links to one or more nodes
in the network and the mapping of these links and nodes in a graph results in a geometric shape
that may be used to describe the physical topology of the network. Likewise, the mapping of
the data flow between the nodes in the network determines the logical topology of the network.
The physical and logical topologies may or may not be identical in any particular network.

5.2.1 Basic Topology Types
The study of network topology recognizes seven basic topologies:
Point-to-point topology
Bus (point-to-multipoint) topology

Star topology
Ring topology
Tree topology
Mesh topology
Hybrid topology

This classification is based on the interconnection between computers—be it physical or logical.
The physical topology of a network is determined by the capabilities of the network access
devices and media, the level of control or fault tolerance desired, and the cost associated
with cabling or telecommunications circuits. Networks can be classified according to their
physical span as follows:
LANs (Local Area Networks)
Building or campus internetworks
Wide area internetworks

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