UNIT 5MANAGING COMPUTER NETWORKS

LEVEL 3 NETWORK TOPOLOGIES AND LAYOUT

NETWORK TOPOLOGY

• Network Topology refers to layout of a network and how different nodes in a

network are connected to each other and how they communicate.

• Topologies are either physical (the physical layout of devices on a network) or

logical (the way that the signals act on the network media, or the way that the

data passes through the network from one device to the next).

LINEAR BUS TOPOLOGY

• Bus Topology: In networking a bus is the central cable -- the main wire -- that

connects all devices on a local-area network (LAN). It is also called the backbone.

• This is often used to describe the main network connections composing the

Internet. Bus networks are relatively inexpensive and easy to install for small

networks. Ethernet systems use a bus topology.

LINEAR BUS – PROS & CONS

• Easy to set up and add new devices

• Reliable network connection

• Only one main cable is required

• All nodes have equal status so transmissions have to wait their turn

• If too many workstations are connected, the system will become very slow and the work rate will

not be efficient

• It can be difficult to locate a problem in the network – parts of network are easily cut off.

STAR TOPOLOGY

Star Topology: In a star network devices are connected to a central

computer, called a hub.

Nodes communicate across the network by passing data through the

hub.

STAR TOPOLOGY – PROS & CONS

• A number of repeaters are used for Ring topology with large number of nodes,

because if someone wants to send some data to the last node in the ring topology

with 100 nodes, then the data will have to pass through 99 nodes to reach the 100th

node. Hence to prevent data loss repeaters are used in the network.

• The transmission is unidirectional, but it can be made bidirectional by having 2

connections between each Network Node, it is called Dual Ring Topology.

• In Dual Ring Topology, two ring networks are formed, and data flow is in opposite

direction in them. Also, if one ring fails, the second ring can act as a backup, to keep

the network up.

• Data is transferred in a sequential manner that is bit by bit. Data transmitted, has to

pass through each node of the network, till the destination node.

RING TOPOLOGY

RING TOPOLOGY – PROS & CONS• No single node should hold up other users as all nodes can use a token as it passes around

the ring – equal share of bandwidth

• Easy to set up and manage

• Cheap to set up

• No Collisions

• Slower than a star topology under normal load

• If the cable fails anywhere in the ring then the whole network will fail

• If a node fails then the token cannot be passed - the whole network fails

• The hardest topology to troubleshoot because it can be hard to track down where in the ring the failure

has occurred

• Harder to modify or expand because to add or remove a node you must shut down the network

temporarily

• In order for the nodes to communicate with each other they must all be switched on

MESH TOPOLOGY

MESH TOPOLOGY – PROS & CONS

• Multiple connections / Multiple routes for data

• Direct connections to many other devices

• Loss of a line does not affect communication

• Alternative lines available

• Complex management issues

• Costs – expensive number of connections

• Repeated Information

TREE TOPOLOGY

TREE TOPOLOGY

Advantages of a Tree Topology

Point-to-point wiring for individual segments.

Supported by several hardware and software venders.

Easily extendable – add new components

Disadvantages of a Tree Topology

Overall length of each segment is limited by the type of cabling used.

If the backbone line breaks, the entire segment goes down.

More difficult to configure and wire than other topologies.

COMBINED TOPOLOGIES - HYBRID• multiple physical

topologies are combined

to form one large network

• Each topology has its own

strengths and weakness

• Objective: total strength

improves the network

performance

LAYOUT

• Although LANs come in many different shapes and sizes, they generally use

similar technologies and components.

• The most common type of LAN is based on Ethernet technology, as originally

devised by Digital, Intel and Xerox.

• This was used as the blueprint for the IEEE’s (Institute of Electrical and

Electronics Engineers) 802.3 specification, which was released back in 1980.

• Over the years a number of improvements have been made to Ethernet

technology.

LAYOUT• One of the most challenging and disruptive elements of networking is installing the cabled infrastructure.

• In simple terms, a WAN connection will enter the building on the ground floor.

• This is then piped to each floor using vertical cabling (also called the backbone wiring).

• As we have seen, backbones typically use Gigabit Ethernet.

• On each floor a room (wiring closet) is set aside to distribute the backbone signals via hubs and switches.

• Fast Ethernet/Ethernet cables from these run from special patch panels into the walls and throughout the

entire floor.

• From here, Ethernet/ Fast Ethernet patch leads are connected from RJ45 wall sockets to individual

workstations, servers, shared printers, photocopiers and so on.

• In this way, each floor operates like a separate star topology, all connected via the same backbone.

• Wireless technologies can provide multiple wireless access points through an organisation’s building but the

need for wired infrastructure will typically still exist.

LAYOUTTASK

Research the following,

• Application server

• Proxy server

• Workstations

• Thick client

• Thin client

• Network Computer

• Explain their role in a network, use the diagram to give you

a starting point.

TYPES OF NETWORK

• LAN - Local Area Network.

• WAN - Wide Area Network.

• WLAN - Wireless Local Area Network.

• MAN - Metropolitan Area Network.

• PAN – Personal Area Network

• SAN - Storage Area Network, System Area Network, Server Area Network, or

sometimes Small Area Network.

TASK

• Using the list of network setups

• Draw each network

• Provide an example of where it would be used

• A description of how it works.

CONCLUSION

• Discussed network topologies..

• Discussed the functions of network infrastructure.

• Considered the purpose of network topologies and network layout/design.…