NETWORKING HARDWARE

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NETWORKING HARDWARE
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What is a Computer Network?

• A network consists of two or more computers that
  are linked in order to share resources and
  devices, exchange files, or allow electronic
  communications.

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A computer network should have at least 

• Two computers.
• Network Interface Card (NIC) A network interface
  card serves as the means of communication between
  the nodes in the network.
• Transmission Media Such as wires, cables, radio
  waves or optical fibers.
• Protocol The protocol identifies the standards
  of communication between the components in a
  network. It also specifies the technical
  specifications in the network such as bandwidth,
  the way data is sent and routed, packet formats
  and others.
• Network Operating System (NOS) Software that
  controls and manages the different hardware and
  software used in the network and helps in setting
  the privileges and permissions for accessing
  resources and information. Among the widely used
  NOSs are MS Windows 2000, MS Windows NT and
  Novell NetWare.

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Relations between the different components of a
network

• Peer-to-peer Network The terminals in a
  peer-to-peer network have equal capability to
  share files, e-mails and other resources.
• Client/server Network A network, which has a
  powerful central computer called a server. The
  server has fast processing capability and can
  provide a high level of service in sharing
  resources.
• Clients, on the other hand, are PCs or
  workstations on which the users run applications.
  Clients rely on servers for resources (files,
  devices, etc.), and even processing ability. 
  Generally, a client/server network could have
  several servers such as 
• Printer Server
• File Server

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Types of Networks

• LAN (Local Area Network) A LAN is a network
  situated within a confined area such as one
  school or building.
• MAN (Metropolitan Area Network) Larger than a
  LAN, a MAN can be located in one city, group of
  schools or buildings.
• WAN (Wide Area Network) A WAN consists of linked
  LANs that are geographically widespread. It can
  be situated in several countries or even
  worldwide. The Internet is a WAN and is, so far
  considered as the largest network.

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What is a Network Topology?

• the connection configuration of networks
• arrangement or layout of computers, cables, and
  other components on a network. (MICROSOFT MCSE
  Training Kit Networking Essentials Plus, Third
  Edition).
• Networks basic design (MICROSOFT MCSE Training
  Kit Networking Essentials Plus, Third Edition).
• a physical arrangement of network nodes and media
  within an enterprise networking structure. (CISCO
  CNAP 1st yr. companion guide, 2nd Edition)

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Network Topology
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Bus Topology

• A linear bus topology consists of a main run of
  cable with a terminator at each end. All nodes
  (file server, workstations, and peripherals) are
  connected to the linear cable.

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Bus Topology

• Advantages
• Easy to connect a computer or peripheral to a
  linear bus.
• Requires less cable length than a star topology.
• Disadvantages
• Entire network shuts down if there is a break in
  the main cable.
• Terminators are required at both ends of the
  backbone cable.
• Difficult to identify the problem if the entire
  network shuts down.
• Not meant to be used as a stand-alone solution in
  a large building.

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Star Topology

• A star topology is designed with each node (file
  server, workstations, and peripherals) connected
  directly to a central network hub or concentrator

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Star Topology

• Advantages
• Easy to install and wire.
• No disruptions to the network when connecting or
  removing devices.
• Easy to detect faults and to remove parts.
• Disadvantages
• Requires more cable length than a linear
  topology.
• If the hub or concentrator fails, nodes attached
  are disabled.
• More expensive than linear bus topologies because
  of the cost of the concentrators.

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• Ring Topology
• the nodes are connected in a closed loop by
  communication lines
• is a single closed ring consisting of nodes and
  links, with each node connected to only two
  adjacent nodes. (CISCO CNAP 1st yr. companion
  guide, 2nd Edition).
• computers are connected on a single circle of
  cable.
• (MICROSOFT MCSE Training Kit Networking
  Essentials Plus, Third Edition)

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Ring Topology

• Advantages
• System provides equal access for all computers.
• Performance is even despite many users.

• Disadvantages
• Failure of one computer can impact the rest of
  the network.
• Problems are hard to isolate.
• Network reconfiguration disrupts operation.

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• Mesh Topology
• two or more paths lead to each node so that the
  overall structure becomes that of a mesh
• each computer is connected to every other
  computer by separate cablings. (MICROSOFT MCSE
  Training Kit Networking Essentials Plus, Third
  Edition).
• every node is linked directly to every other
  node. (CISCO CNAP 1st yr. companion guide, 2nd
  Edition).

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Mesh Topology

• Advantages
• System provides increased redundancy and
  reliability as
• well as ease of troubleshooting.

• Disadvantages
• System is expensive to install because it uses a
  lot of cabling.
• Has a high administrative overhead

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Mesh Topology
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• Tree Topology
• Several child nodes are connected to a parent
  node.
• It uses a trunk node from which it branches to
  other nodes.

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Tree Topology

• Advantages
• Modifying system and adding new computers is
  easy.
• Centralized monitoring and management are
  possible.
• Failure of one computer does not affect the rest
  of the network.

• Disadvantages
• If the parent node (hub) is malfunctioning it
  will affect all the subordinate nodes.

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Methods of Media Access Control

• CSMA/CD (Carrier Sense Multiple Access with
  Collision Detection)
• Token passing

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CSMA/CD (Carrier Sense Multiple Access with
Collision Detection)

• Used in BUS topology LAN 10BASE-T
• Carrier Sense
• All the terminals need to monitor whether data is
  passing on the cable
• Transmission starts when no data is passed,
  pauses for standby when data is passed
• Multiple Access
• Two or more computers share one cable
• Collision Detection
• Data collide if two or more terminals transmit
  data simultaneously.
• If a collision is detected, all terminals will
  have to wait a specified time before attempting
  retransmission

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Token passing

• Used in ring topology LAN
• Signal (token) carrying the right to transmit on
  the cable is passed around the network
• Token carrying no data free token
• Token carrying data busy token

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2 types of token passing

• Token ring
• physical star
• Logical ring
• Token bus
• Physical bus
• Logical ring

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Mechanism of Token Passing
ILLUSTRATION Terminal A seizes the token and
sends data to terminal C.
D
D
A
C
C
A
B
B

• The free token is passed around the ring.
• Only the station that seizes the free token can
  transmit.

2. Data is attached to the token and sent from A
to C
- Free token
-Busy token
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Mechanism of token passing
D
D
C
C
A
A
B
B
3. C receives the data, adds receipt
notification to the token and passes it on
4. A receives the receipt notification from C,
and passes the free token.
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• END OF DISCUSSION