Computer Networks lecture 02 Presentation.pptx

Computer Networking class 2

1. Computer Networks By AFIA BHUTTO Lecture 2

2. This is the front of a switch. 24 interfaces also known as ports. Switches have a lots of interfaces to connect end hosts like PCs and servers too. These are called RJ (Registered jack)45 connector. Interfaces And Cables

3. The RJ 45 connector is used on the end of a copper Ethernet cable.

4. Ethernet is a collection of network protocols/standards. For the purpose of this lesson, we will focus on types of cabling as defined by Ethernet standards. Why do we need protocols and standards? Ethernet

5. If two people are talking to each other and one only speaks English and the other only speaks Japanese, there's not going to be a much or any communication between them. What they need is some agreed upon system of communicating like a common language between them. Network protocols serve that purpose for network devices. That’s why standard like Ethernet exist. Example

6. More relevant Example of Interfaces and cables. If you are trying to connect to, for example a network switch, but the maker of the cable and the maker of a switch haven't agreed upon the size and shape of the connector and port you won’t be able to connect them. That’s why there are industry standards that all vendors follow, both in terms of physical standards like connectors and cables like these, as well as logical standards like IP the internet protocol

7. Now connection between devices in a network operate at a set speed. These speeds are measured in bits per second. Bit is a value represented by either a 0 or a 1. When communicating across a copper network cable, a variation in the electrical signal is interpreted by the receiving device as a 0 or a 1. Series of 8 bits is equal to 1 byte.

8. Defined in the IEEE 802.3 standard in 1983. IEEE=Institute of electrical and electronic engineers. Table of some IEEE standards for Ethernet standards (Copper). Ethernet Standards speed Common name IEEE standard Informal name Maximum Length 10Mbps Ethernet 802.3i 10Base-T 100 m 100Mbps Fast Ethernet 802.3u 100Base_T 100 m 1Gbps Gigabit 802.3ab 1000Base_T 100 m 10Gbps 10 gig Ethernet 802.3an 10 G Base-T 100 m

9. The copper cables used in Ethernet standards are UTP cables. UTP stands for unshielded twisted pair. Unshielded means that the wires have no metallic shield, which can make them vulnerable to electrical interfaces. There are four pairs of wires that are twisted together. The twist actually helps protect against electromagnetic interfaces, or EMI UTP Cables

10. 10 Base-T and100 Base-T equal to 2 pairs (4 wires). 1000 Base-T and 10GBase-T equal to 4 pairs(8 wires). UTP Cables

11. 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 Lets say we are connecting a PC to a switch with fast Ethernet connection These numbers represent the pins on the RJ45 on the Pcs network interface card and the switch. There are four but we use only 4 or 2 pairs. Since this is a fast Ethernet. UTP Cables10 Base-T and100 Base-T

12. And will connect two pins at positions 1 and 2 on the switches network interface. The pc will use pin 1 and 2 to transmit data to the switch. Which we can write as Tx . Because the pc is transmitting data on pins 1 and 2, so switch cannot transmit on those. It has to receive data. Which we can write as RX on pin 1 and 2. UTP Cables10 Base-T and100 Base-T

13. Now the next pair that is used in a 10 base-T or 100 base-T cable is not 3 and 4, its 3 and 6. The function of each pin is opposite of the pair on pins On a switch pins 3 and 6 are used to transmit data and on pc pins 3 and 6 used to receive data. This allows full duplex transmission. Full transmission means that both devices and send data at the same time. Its called straight-through cable UTP Cables10 Base-T and100 Base-T

14. Crossover cables are used to connect two same devices like switch to switch router to router. If the switch on the left tries to trasnmit some data to the switch on the right it doesn’t work. Pin 1 connects to pin 3 on other side and pin 2 is connected with pin 6 on other side. Pin 3 connects with pin 1 and pin 6 connects with pin 2 on left side. Crossover cable

15. Device Type Transmit (TX) pins Receive (RX) pins Router 1 and 2 3 and 6 Firewall 1 and 2 3 and 6 Pc 1 and 2 3 and 6 Switch 3 and 6 1 and 2 Devices

16. Fiber-optic Connections In these interfaces you insert one of these its called an SFP transceiver (small form-factor pluggable). Fiber cable connects these type of devices. A  Fiber Optic Cable  is a cable that contains optical fibers (usually glass) coated in plastic that are used to send data by pulses of light

17. Fiber optics 1.(The fiber core glass itself) light is transmitted down this core to transmit data from one device to another. 2.Cladding that reflects light 3.A protective buffer 4.The outer jacket of the cable.

18. Lower cost than fiber-optics. Short maximum distance. RJ 45 ports used with UTP are cheaper than SFP ports. Higher cost than UTP Longer maximum distance than UTP. SFP ports are more expensive than RJ 45. UTP VS Fiber optics

19. You connect two old routers with a UTP cable, however data is not successfully sent and received between them. What could be the problem? TASk