CN Lecture 7 CN slide for ppt presentation.pptx

1. Computer Networks Lecture # 7 Course Title: Computer Networks Instructor: Tahira Malik (Lecturer) Email Address: [email protected] Department of Computer Science Term (Semester): Fall 2020 1

2. Transmission Media The physical path through which computers send and receive signals is called transmission media Transmission media is what actually carries a signal from one point to another Anything that can carry information from a source to a destination. Classes of Transmission Media Two classes of Transmission Media: Guided Media Unguided Media

3. Transmission Media Guided Media Guided media are those media that uses a physical path or conductor to transmit the signals from one device to another A medium such as copper wiring is referred to as bounded (guided) media because it holds electronic signals Fiber optic cable is also said to be bounded media as it holds light waves Unguided Media Unguided media or wireless communication transport electromagnetic waves without a physical conductor or media that do not physically constrain signals are considered to be unbounded media (unguided) Instead signals are broadcast through air and are available to anyone who has a receiver capable of receiving them

4. Guided Media All types of cables generally fall under the guided media Cables have a central conductor that consists of a wire or fiber surrounded by a plastic jacket It normally transmits signals using the lower end of the electromagnetic spectrum, such as simple electricity and sometimes radio waves Three types of cable media are Twisted Pair Cable Coaxial Cable Fiber-Optic Cable

5. Twisted Pair Cable The construction of TP is simple Two insulated wires are twisted around one another This is to help offset electrical disturbances which can affect TP cable such as radio frequency interference (RFI) and electromagnetic interference (EMI) These "pairs" of wires are then bundled together and coated to form a cable Twisted pair comes in two forms: Unshielded Twisted Pair (UTP) cable Shielded Twisted Pair (STP) cable

6. Unshielded Twisted Pair Cable UTP cable consists of a number of twisted pairs with a simple casing (no shielding) It is commonly used in telephone systems and is easy to install Structure of the cable:

7. Unshielded Twisted Pair Cable Characteristics: Cost: lowest (except cat5) Installation: easy Bandwidth Capacity: 1 – 500 Mbps (typically 10 Mbps) Node Capacity per Segment: 2 Attenuation: 100 meters (high) EMI: More vulnerable to EMI and eavesdropping Connectors used with UTP included RJ-11 and RJ-45 modular connectors, RJ-11 connectors accommodate 4 wires or 2 twisted pairs, while RJ-45 houses 8 wires or 4 twisted pairs

8. Shielded Twisted Pair STP has a shield usually aluminum/polyester (foil or mesh) between the outer jacket or casing and the wires This special layer is designed to help offset interference problems It was the first TP cable used for LANs Structure of the cable:

9. Shielded Twisted Pair Characteristics: Cost: Moderate Installation: Fairly easy Bandwidth Capacity: 1 – 155 Mbps (typically 16 Mbps) Node Capacity per Segment: 2 Attenuation: 100 meters (high) EMI: Less vulnerable to EMI and eavesdropping than UTP TP cabling has been around a while and is a tried and true medium. It hasn't been able to support high speed data transmissions until recently. New development is focusing on achieving 100 Mbps throughput on UTP.

10. Coaxial Cable Coaxial cable or just "coax" has been perfect for applications requiring stable transmission characteristics over fairly long distances Construction-wise coax is a little more complex then TP It is typically composed of a copper conductor that serves as the "core" of the cable This conductor is covered by a piece of insulating plastic, which is covered by a foam or wire mesh serving as both a shield and second conductor This second conductor is then coated by PVC (plastic) or other coating The conductor within a conductor sharing a single axis is how the name of the cable is derived

11. Coaxial Cable Structure of the cable:

12. Coaxial Cable Characteristics: Cost: Moderate Installation: Simple Bandwidth Capacity: 10 Mbps Node Capacity per Segment: 30 - 100 Attenuation: Few kilometers (low) EMI: Less vulnerable to EMI and eavesdropping

13. Fiber Optic Cable The crucial element for fiber is glass that makes up the core of the cabling The glass core of a fiber optic cable is surrounded by and bound to a glass tube called "cladding“ Cladding adds strength to the cable while disallowing any stray light wave from leaving the central core This cladding is then surrounded by a plastic or PVC outer jacket which provides additional strength and protection for the innards Fiber optic is lightweight and is utilized often with LEDs (Light-Emitting Diodes) and ILDs (Injection Laser Diodes) Fiber optic cable transmits light signals rather than electrical signals One optical fiber is the same diameter as a human hair It can only be banded at a specific angle

14. Fiber Optic Cable Structure of Cable

15. Fiber Optic Cable Optical fibers may be multimode or single mode Single mode fibers allow a single light path and are typically used with laser signaling (ILDs) They allow greater bandwidth but are more expensive Multimode fibers use multiple paths The physical characteristic of the multimode fiber makes all parts of the signal arrive at the same time, appearing to the receiver as though they were one pulse They use LEDs and are less expensive

16. Fiber Optic Cable Characteristics: Cost: Highest Installation: Difficult Bandwidth Capacity: 2 Gbps (typically 100 Mbps) Node Capacity per Segment: 2 Attenuation: Tens of kilometers (lowest) EMI: Not effected by EMI and eavesdropping

17. Unguided Media For unguided media, transmission and reception are achieved by means of an Antenna For transmission, the antenna radiates electromagnetic energy into the medium (usually air), and for reception, the antenna picks up electromagnetic waves from the surrounding medium There are basically two types of configurations for wireless transmission; directional and omnidirectional For the directional configuration, the transmitting antenna puts out a focused electromagnetic beam; the transmitting and receiving antennas must therefore be carefully aligned In the omnidirectional case, the transmitted signal spreads out in all directions and can be received by many antennas. In general, the higher the frequency of a signal, the more it is possible to focus it into a directional beam

18. Unguided Media Three general ranges of frequencies are of interest in our discussion of wireless transmission. Microwave Broadcast Radio Infrared

19. Unguided Media Microwave Frequencies in the range of about 2 GHz to 40 GHz are referred to as microwave frequencies At these frequencies, highly directional beams are possible, and microwave is quite suitable for point-to-point transmission Microwave is also used for satellite communications Microwave is commonly used for both voice and television transmission A business can establish a microwave link to a long distance telecommunications facility in the same city, bypassing the local telephone company The higher the frequency used, the higher the potential bandwidth and therefore the higher the potential data rate

20. Unguided Media Broadcast Radio Frequencies in the range of 30 MHz to 1 GHz are suitable for omnidirectional applications and are referred to as the broadcast radio range This range is used for a number of data-networking applications The principal difference between broadcast radio and microwave is that the former is omnidirectional and the latter is directional Thus, broadcast radio does not require dish-shaped antennas, and the antennas need not be rigidly mounted to a precise alignment Transmission is limited to line of sight, and distant transmitters will not interfere with each other due to reflection from the atmosphere

21. Unguided Media Infrared Another important frequency range, for local applications, is the infrared portion spectrum This covers, roughly, from 3 X 10 11 to 2 X 10 14 Hz Infrared is useful to local point-to-point and multipoint applications within confined areas, such as a single room One important difference between infrared and microwave transmission is that the former does not penetrate walls Transceivers must be in line of sight of each other Thus, the security and interference problems encountered in microwave systems are not present Furthermore, there is no frequency allocation issue with infrared, because no licensing is required

22. UTP Cable Installation EIA/TIA 568A and 568B (standards) The T-568A standard is supposed to be used in new network installations Most off-the-shelf Ethernet cables are still of the T-568B standard; however, it makes absolutely no functional difference in which you choose

23. UTP Cable Installation UTP Cable Configurations Straight-Through Cable: Straight-through means that the color of wire on Pin 1 on one end of the cable is the same as that of Pin 1 on the other end Pin 2 is the same as Pin 2, and so on The cable is wired to either EIA/TIA T568B or T568A standards, which determines what color wire is on each pin

24. UTP Cable Installation UTP Cable Configurations Crossover Cable: A crossover cable means that the second and third pairs on one end of the cable will be reversed on the other end The pin-outs are T568A on one end and T568B on the other end If the crossover cable is used between switches, it's considered to be part of the "vertical" cabling. Vertical cabling is also called backbone cabling A crossover cable can be used as a backbone cable to connect two or more switches in a LAN, or to connect two isolated hosts to create a mini-LAN This will allow the connection of two hosts or a server and a host without the need for a hub between them

25. UTP Cable Installation UTP Cable Configurations

26. UTP Cable Installation UTP Cable Configurations Rollover Cable: A rollover cable can be used to connect a host or dumb terminal to the console port on the back of a router or switch Cable is called a rollover because the pins on one end are all reversed on the other end as though one end of the cable was rotated or rolled over

27. UTP Cable Installation Figure shows how to connect networking devices

28. Questions Any Question Please? You can contact me at: [email protected] Your Query will be answered within one working day. 28

29. Thanks 29