Transcript Network types Point-to-Point (Direct) Connection

Network types
Point-to-Point (Direct) Connection
• Dedicated circuit boards connected by cable;
• To transfer data from A to B:
– A writes on its circuit board;
– A’s board transfers data to B’s board;
– B reads data from its board.
A
B
Point-to-Point Connection (cont.)
• Pros:
– High transfer speed;
– Secure connection;
• Cons:
– Difficult to add a new computer to a set of communicating computers.
– Difficult if communication is between heterogeneous computers;
– Expensive: circuit boards needed for every pair of communicating
computers;
• How many boards would you need to connect 5 computers
via this method?
Local Area Network (LAN)
• A single shared medium, usually a cable, to
which computers can attach.
PC 1
Printer
PC 2
PC n
File Server
Local Area Networks (cont.)
• Designed and developed for communications and resource
sharing in a local work environment (room, campus, building).
• Because sharing occurs:
– Cost decreases
– Computers have to coordinate the use of the network;
• Overall, LANs connect more computers than any type of
network.
Connecting a Computer to a LAN
• Requires a network interface;
• A network interface consists of:
– a circuit board that plugs into the computer
– A cable that connects the circuit board to the LAN;
• The network interface isolates a computer from the
LAN  heterogeneous computers can communicate
across the LAN.
Network Topologies
• The configurations of network components
• Widely used network topologies
– Bus
– Star
– Extended star
– Ring
– Mesh
– Partial Mesh
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Bus Network Topology
• Most simple network topology
• All devices connected to a common central
cable (wire or other media )
• Inexpensive
• Easily expanded
• If cable fails, the entire network will shut down
• Earlier Ethernet commonly implement a bus
topology
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Bus Network Topology (Continued)
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Star Network Topology
• Star topology is centered around central routing
device called a switch or a hub by point-topoint links.
• All network nodes connect to the hub
• Easy to install and update
• If hub fails, network fails
• Disadvantage that it require more cabling
therefore, higher cost than the bus.
• Extended star
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Ring Network Topology
• Each node connected to two other nodes in a
ring
• Similar to the buss, but with the ends of the
buss connected together by unidirectional
transmission link to form a single closed loop.
• Each station on the network connects to the
network at a repeater.
• Expensive and difficult to install
• One example of a ring topology is Token Ring
networks
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Ring Network Topology (Continued)
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Ring Topology (cont.)
• Sending a message:
– There is a special message, called token;
– Exactly one token exists on the ring at any time which is passed along
the ring;
– To send data, a computer waits for the token to arrive, and then
transmits one message;
– The message is transmitted to the next computer, and then to the
next, until it arrives back to the sender.
– After the message is transmitted, the computer holding the token,
passes the token to the next computer in the ring.
• Dual-Ring
– Tow rings allow data to be sent in both directions
– Creates redundancy.
Mesh Network Topology
• Every node connected to every other node
• Fast
• Reliable
– No hub or bus to fail
– If one device goes down, it is the only node affected
• Expensive
– Every node must be wired to every other node
• Difficult to add nodes
– If there are 32 nodes in a mesh network and you
wish to add a new node, how many new cables
must you add?
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• Partial Mesh
– At least one derive is connected to all other
devices without being fully meshed.
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