1. Network Topology and LAN Technologies

2. Definition
A network topology is the graphic description of the arrangement of a network including its nodes and cable or connecting lines.
In short it’s a schematic description of the arrangement of a network, including its nodes and connecting lines.

3. Types of Topology
The topology of a network is the actual geometric layout of workstations. There are 4 main types o physical topology:
Bus
Star
Ring
Mesh

4. Bus Topology
In the bus network topology, every workstation or node is connected to a main cable called the bus. Therefore, in effect, each workstation is directly connected to every other workstation or node in the network.

5. Advantages of Bus Topology
It is easy to set up, handle, and implement. 
It is best-suited for small networks.
It costs less.

6. Disadvantage of Bus Topology
The cable length is limited and this limits the number of network nodes that can be connected.
This network topology can perform well only for a limited number of nodes. When the number of devices connected to the bus increases, the efficiency decreases.
It is suitable for networks with low traffic. High traffic increases load on the bus, and the network efficiency drops.
It is heavily dependent on the central cable. A fault in the cable leads to network failure.
It is not easy to isolate faults in the network nodes.
Each device on the network "sees" all the data being transmitted, thus posing a security risk.

7. Bus Topology

8. Star Topology
In the star network topology, there is a central computer or server to which all the workstations are directly connected. Every workstation is indirectly connected to each other through the central computer.
Each node has a dedicated set of wires connecting it to a central network hub. Since all traffic passes through the hub, the hub becomes a central point for isolating network problems and gathering network statistics.

9. Advantages of Star Topology
Due to its centralized nature, the topology offers simplicity of operation. 
It also achieves isolation of each device in the network so adding or removing network nodes is easy, and can be done without affecting the entire network.
Due to the centralized nature, it is easy to detect faults in the network devices.
As the analysis of traffic is easy, the topology poses lesser security risk.
Data packets do not have to pass through many nodes, like in the case of a ring network. Thus, with the use of a high-capacity central hub, traffic load can be handled at fairly decent speeds.

10. Disadvantages of Star Topology
Network operation depends on the functioning of the central hub/server. Hence, central hub failure leads to failure of the entire network.
Also, the number of nodes that can be added, depends on the capacity of the central hub.
The setup cost is quite high.

11. Star Topology

12. Ring Topology
In the ring topology, the workstations are connected in a closed loop configuration. Adjacent pairs of workstations are directly connected. Other pairs of workstations are indirectly connected, with data passing through one or more intermediate nodes.
In a ring topology, the signal travels in only one direction, carried by token from node to node

13. Advantages of Ring Topology
The data being transmitted between two nodes passes through all the intermediate nodes. A central server is not required for the management of this topology.
The traffic is unidirectional and the data transmission is high-speed. So in comparison to a bus, a ring is better at handling load.
The adding or removing of network nodes is easy, as the process requires changing only two connections.
The configuration makes it easy to identify faults in network nodes.
In this topology, each node has the opportunity to transmit data. Thus, it is a very organized network topology.
It is less costly than a star topology.

14. Disadvantages of Ring Topology
The failure of a single node in the network can cause the entire network to fail.
The movement or changes made to network nodes affect the entire network's performance.
Data sent from one node to another has to pass through all the intermediate nodes. This makes the transmission slower in comparison to that in a star topology. The transmission speed drops with an increase in the number of nodes.
There is heavy dependency on the wire connecting the network nodes in the ring.

15. Ring Topology

16. Mesh Topology
The mesh topology employs either of two schemes, called full mesh and partial mesh. In the full mesh topology, each workstation is connected directly to each of the others. In the partial mesh topology, some workstations are connected to all the others, and some are connected only to those other nodes with which they exchange the most data.

17. Advantages of Mesh Topology
The arrangement of the network nodes is such that it is possible to transmit data from one node to many other nodes at the same time.
The failure of a single node does not cause the entire network to fail as there are alternate paths for data transmission.
It can handle heavy traffic, as there are dedicated paths between any two network nodes.
Point-to-point contact between every pair of nodes, makes it easy to identify faults.

18. Disadvantages of Mesh Topology
The arrangement whereby every network node is connected to every other node of the network, many connections serve no major purpose. This leads to redundancy of many network connections.
A lot of cabling is required. Thus, the costs incurred in setup and maintenance are high.
Owing to its complexity, the administration of a mesh network is difficult.

19. Mesh Topology

20. LAN TECHNOLOGIES-Ethernet
Ethernet is the most widely-installed local area network ( LAN) technology and specified in a standard, IEEE 802.3, Ethernet was originally developed by Xerox.
An Ethernet LAN typically uses coaxial cable or special grades of twisted pair wires. Ethernet is also used in wireless LANs.
The most commonly installed Ethernet systems is called 10BASE-T.

21. Types of Ethernet Standards
Standard Ethernet (10 Base-T)
Fast Ethernet (100 Base-T)
Gigabit Ethernet (1000 Base-T)
10 Gigabit Ethernet (10GE/10GbE/10GigE)

22. Standard Ethernet (10 Base-T)
The “T” stands for twisted as in UTP (Unshielded Twisted Pair) and has a transfer rate 10Mbps.
The down side of this standard is that it has a maximum cable lengths of 100 meters between nodes/workstations.
The good side to this network is they are easy to set up and cheap This is why they are an ideal for small offices or homes.

23. Fast Ethernet (100 Base-T
With a transfer rate of 100MbpsFast Ethernet technology met its design goals of increasing the performance of traditional Ethernet while avoiding the need to completely re-cable existing Ethernet networks. Fast Ethernet comes in two major varieties:
100Base-T (using unshielded twisted pair cable). Maximum cable length is 100 meters
100Base-FX (using fiber optic cable) Maximum cable length is 2000 meters
It relies on Category 5 UTP (100Base-TX) or Category 3 or better UTP (100Base T2),

24. Fast Ethernet

25. Gigabit Ethernet (1000BaseT)
Where as Fast Ethernet improved traditional Ethernet from 10 Megabit to 100 Megabit speed, Gigabit Ethernet boasts the same order-of-magnitude improvement over Fast Ethernet by offering speeds of 1000 Megabits (1 Gigabit).
1000Base-T uses Category 5 cabling similar to 100 Mbps Ethernet, although achieving gigabit speed requires the use of additional wire pairs.
Has a maximum cable length of 100 meters

26. 10 Gigabit Ethernet
 Transfers data at a rate of 10 gigabits per second (10Gbps) . It was first defined by the IEEE 802.3ae-2002 standard.
Like previous versions of Ethernet, 10GbE can use either copper or fiber cabling. However, because of its higher bandwidth requirements, higher grade copper cables are required i.e. CAT 6a or Category 7 cables for links up to 100meters.
However, unlike previous Ethernet standards, 10-gigabit Ethernet defines only full duplex point-to-point links which are generally connected by network switches.

27. Power over Ethernet
PoE is a solution in which an electrical current is run to networking hardware over the Ethernet Category 5 cable or higher. This solution does not require an extra AC power cord at the product location. This minimizes the amount of cable needed as well as eliminates the difficulties and cost of installing extra outlets.

28. END OF LECTURE