COMPUTER COMMUNICATION NETWORKS AND INTERNET

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TEE 213/05 Telecommunication

Principles

Unit 5 COMPUTER COMMUNICATION NETWORKS AND INTERNET

Semester January 2012



Switch / Hub Users

• A hub is slower than the switch. The switch can support up to 2N users without dividing the speed by the number of users.

• The switch achieves this by quickly switching between many users at the same time. This is due to the assumption that not all computers will be requesting for information at the same time.



Example – Switch / Hub

• A 100Mb/s 8-port switch and a 100Mb/s 8-port hub are tested for 8 users. Calculate the speed that will be experienced by each user when the:

– Switch is used– Hub is used

• • Switch = No degradation of speed will be experienced and each

user will experience 100Mb/s.

• Hub = Each user will experience a maximum surfing speed of 100Mb/s / 8 = 12.5Mb/s



Mesh Configuration



• Example• Calculate the number of links that will be needed to link up 10

computers.



Star Topology

• If the central computer (server) goes down, all communication between computers ceases.

• This configuration is also speed-limited as all communications need to pass through a single node (the server computer).



Ring Topology



Ring Topology Description

• In a ring topology, the server or control computer and all computers are linked in a single close-loop.

• Usually data is transferred around the ring in only 1 direction, passing through each node.

• Therefore, there is some amplification and regeneration of data at each node, permitting long distance transmission distances between nodes.

• The ring topology can also be implemented at a low cost. Expansion is also simple, as a new node can be easily inserted into the ring network at any point.



Bus Topology

In a Mesh topology, one node is connected to every other node. Every node can talk directly to all other nodes. This arrangement is very expensive and will cost more with the increase of computers in the system, especially with wired connections.



Advantages and disadvantages of each topology



Hierarchy of Networks



Relationship with different types of networks



7-Layer OSI



OSI Analogy



The Packet Transmission System



TCP/IP

OSI layers TCP/IP layers7. Application Application6. Presentation5. Session4. Transport Host-to-Host (TCP)3. Network IP2. Data link Network access1. Physical



IPV4 Header



IPV4 Address Classes



Example

Given the company's network. Determine the Class of this network

From Figure, the router has address 202.178.0.1. Matching the net ID with Table, this is a class C network.



IPV4 addresses that cannot be used

IP Address Reason why cannot be usedDefault - Network 0.0.0.0 Refers to the default route. This route

simplifies routing tables used by IPLoopback - Network 127.0.0.1 Reserved for loopback. The address

127.0.0.1 is often used to refer to the local host. Using this address, applications can address a local host as if it were a remote host.

Network Address - IP address with all hosts bits set to 0 (for example, 192.0.0.0)

Refers to the actual network itself. For example, network 202.178.0.0 can be used to identify network 202.178. This type of notation is often used within routing tables

Subnet/network broadcast - IP address with all node bits set to 1 (for example 202.178.255.255) (255 represents 1)

IP addresses with all node bits set to 1 are local network broadcast addresses and must not be used. Example: 125.255.255.255 (Class A)

Network broadcast - IP address with all bits set to 1. Example: 255.255.255.255

The IP address with all bits set to 1 is a broadcast address and must not be used. These refer to all nodes in the network no matter what the IP address.



Example

• For a Class A network, calculate:– The maximum number of networks– The maximum number of valid hosts



Thank you

Engineering

COMPUTER COMMUNICATION NETWORKS AND INTERNET