COMPUTER NETWORKS Ms. Mrinmoyee Mukherjee Assistant Professor St. Francis Institute of Technology, Mount Poinsur, S.V.P Road, Borivli (west), Mumbai

OBJECTIVES OF THE DAY 1.Properties of physical media 2.Different types of Media a. Twisted pair b. Coaxial cable c. Fiber Optic Cable d. Microwave Transmission e. Satellite Transmissions PHYSICAL LAYER

PROPERTIES OF PHYSICAL MEDIA THE PROPERTIES OF PHYSICAL LAYER ARE- 1.Data Limit Rates- how fast we can send data 2.Physical Layer Protocols and Services 3.Physical layer signaling and Encoding 4.Type of Channel- Noisy/ Noiseless 5.Bandwidth Delay Product 6.Performance-how good the network is A.Bandwidth B.Throughput C.Latency a.Propagation time b.Transmission Time c.Queuing Time d.Processing delay

Transmission medium:: the physical path between transmitter and receiver. Repeaters or amplifiers may be used to extend the length of the medium. Communication of electromagnetic waves is guided or unguided. Guided media :: waves are guided along a physical path (e.g, twisted pair, coaxial cable and optical fiber). Unguided media:: means for transmitting but not guiding electromagnetic waves (e.g., the atmosphere and outer space). PROPERTIES OF PHYSICAL MEDIA

Describe the purpose of the Physical layer in the network and identify the basic elements that enable this layer to fulfill its function Physical Layer Protocols and Services

Describe the role of bits in representing a frame as it is transported across the local media Physical Layer Protocols and Services

Describe the role of signaling in the physical media Physical Layer Protocols and Services

Distinguish who establishes and maintains standards for the Physical layers compared to those for the other layers of the network Physical Layer Protocols and Services

Identify hardware components associated with the Physical layer that are governed by standards Physical Layer Protocols and Services

Explain that network communication at this layer consists of individual bits encoded onto the Physical layer and describe the basic encoding techniques Physical Layer Protocols and Services

Describe the role of encoding as it applies to the transmission of bits and explain the value of treating a collection of bits as a code Physical Layer Protocols and Services

Define the terms bandwidth, throughput Physical Layer Protocols and Services

13 Twisted pair Coaxial cable Optical fiber Wireless communications Transmission Media Choices

1. Two insulated wires arranged in a spiral pattern 2. Copper or steel coated with copper 3. The signal is transmitted through one wire and a ground reference is transmitted in the other wire. 4. Typically twisted pair is installed in building telephone wiring. 5. Local loop connection to central telephone exchange is twisted pair. Twisted Pair

Limited in distance, bandwidth and data rate due to problems with attenuation, interference and noise – Issue: cross-talk due to interference from other signals – “shielding” wire (shielded twisted pair (STP)) with metallic braid or sheathing reduces interference. – “twisting” reduces low-frequency interference and crosstalk. Twisted Pair

Coaxial Cable 1.It consists of stiff copper wire as the core surrounded by an insulating material. 2.This insulating material is further enclosed within a cylindrical conductor 3.Coaxial cable have higher bandwidth and a better noise immunity 4.Bandwidth close to 1GHz 5.It is mainly used for cable television

Safety Rules

Fiber Optic Cable

Difference PropertyRadio Transmission Millimeter Wave Transmission Light wave Transmission Generatio n Easy to generate Easy to install Travel Distances It can travel large distances It can travel small distances It can travel large distances Penetratio n High-Can penetrate building It cannot penetrate solids Cannot penetrate rain and fog DirectionIt travels in all direction DirectionalUnidirectional Applicati ons Radio and Military operations Remote controls for TV, DVD etc Connect the LANs in two buildings

Telephone Network 1.The modern telephone system provides a two-way, real time transmission of voice signals. 2.Telephone network use circuit switching. 3.Initially the system was completely analog. Now its both analog and digital Phases 1.Caller-Picks up the telephone which alerts a switch in the local telephone office 2.Switch-gets ready to accept a number and gives the dial tone 3.User enters the telephone number using pulses 4.The switch converts the pulses or tones to a telephone number 5.The source switch uses the telephone signaling network to find a route to the destination office and allocates resources to this route 6.The destination office alerts the receiver about an incoming call by ringing its phone 7.The ring is sent back to the caller 8.Conversation begins when the party lifts the phone 9.Call is terminated and the resources released when the user hangs up their telephones

Telephone Network A telephone network is made of three major components

Telephone Network A telephone network is made of three major components

Signaling System Seven (SS7)

1.It is a protocol used in the signaling network. 2.It is similar to TCP/IP protocol 3.Physical Layer- (Message Transport Part-Level-1): It uses physical layer specifications like T-1 and DC0 4.Data Link Layer (Message Transport Part-Level-2): It performs packetizing and error checking 5.Network layer (Message Transport Part-Level-3): Provides end to end connectivity using datagram switching and perform routing 6.Transport Layer – SCCP (Signal Connection Control Point) :used for special services 7.TUP (telephone User Point ):Sets up voice calls. It accepts dialed digits and routes the call 8.TCAP (Transaction Capabilities Application Port) Remote calls that allow application programs on one computer to invoke procedures on other computers 9.ISUP (ISDN user port)- Provides services similar to ISDN network