Telecom lect 1

By: Muhammad Naveed Shaikh

INSTRUCTED BYMUHAMMAD NAVEED SHAIKH

Telecom Systems & Networks

Lecture 1


Computer Networking

• What do you mean by Networking?


Networking

• The art and science of connecting computers with each other in order to share data and resources is termed as Networking.


Advantages & Disadvantages of Networks

Let we discuss the advantages and disadvantages of computer networks..


ADVANTAGES OF NETWORKS

• Security / Encapsulation• Distributed Databases• Faster Problem Solving• Centralized Management• Security through Redundancy• Shared Processing


DISADVANTAGES OF NETWORK• Server faults stop applications being available (SPOF)• Network faults can cause loss of data. • Network fault could lead to loss of resources • User work dependent upon network • System open to hackers • Decisions tend to become centralized • Could become inefficient • Could degrade in performance • Resources could be located too far from users • Network management can become difficult


Network Criteria

Network Criteria

Performance Reliability Security


Applications of NetoworksSome of the network applications in different fields are the following:• Marketing & Sales• Financial and Banking Services• Enterprise Resource Planning• Electronic Messaging• Database Sharing• Information Services• Electronic Data Interchange (EDI)• Teleconferencing• Cellular Telephone• Cable Television• Intenet


Physical & Logical Networks

• What is the main difference between physical and logical networks?


Physical Networks

• Network must be connected physically with wire or wireless medium.

• However even if the computers are connected physically can’t communicate with each other until and unless they are logically connected as well.


Logical Networks

• Network must be connected logically to establish communication among them.

• Logical means there must be some address assign to the node to communicate.

• The most famous addressing is IP addressing scheme like 10.56.0.1

By: Muhammad Naveed Shaikh12

Modes of Transmission • A communications channel is classified as one of

three types:

(depending on the direction of transfer)– Simplex:– Full-Duplex:– Half-Duplex:


SIMPLEX

A simplex mechanism can only transfer data in a single direction• It is analogous to broadcast radio or

television


Half duplex– A half-duplex mechanism involves a shared

transmission medium

– The shared medium can be used for communication in each direction but the communication cannot proceed simultaneously

– It is analogous to using walkie-talkies where only one side can transmit at a time


Full duplex

– Allows transmission in two directions simultaneously• It is analogous to a voice telephone

conversation– in which a participant can speak even if

they are able to hear at the other end


Simplex, Half-Duplex, and Full-Duplex Transmission

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COS & NOS

• What is the difference between client operating system and Network operating system?


Client Operating System (COS)

• The Operating System which has the ability to be a client in the network is known as Client Operating System.

• COS can not administrate the network.

• Client operating system can not be a domain administrator.

• Examples are:• Windows 98, XP, Windows ME, Vista, DOS etc


Network Operating System (NOS)• The Operating System which has the ability to be a server inside the

network is known as Network Operating System.

• NOS can administrate the network.

• It must be a server edition like windows 2003 server

• Server operating system can be a domain administrator.

• Examples are:• Windows 2000 server, Windows 2003 server etc


Transmission Media

• Wired• Wireless


Coaxial Cable

Originally, Ethernet ran over thicknet coaxial cabling. This has, for the most part, gone by the wayside today.


Twisted Pair Cabling

1. Shielded Twisted Pair Cabling (STP)2. Unshielded Twisted Pair Cabling (UTP)


Shielded Twisted Pair

Shielded twisted pair is a special kind of copper telephone wiring used in some business installations. An outer covering or shield is added to the ordinary twisted pair. STP cable is also used for Data Networks. Its shielding allows greater tolerances for protection from EMI interference, such as from flourescent light fixtures and electric motors.


Unshielded Twisted Pair Unshielded twisted pair (UTP) cable is used for both LANs and telephone systems. UTP cables are composed of four color-coded pairs of copper conductors twisted around each other. An outer jacket provides protection and keeps the pairs in alignment. UTP cable connects to devices via 8 pin modular connectors called RJ-45 plugs. All LAN protocols can operate over UTP. Most modern LAN devices are equipped with RJ-45 jacks.


RJ-45 connectors

This is the Connector

This is the Jack


Cross Over cable – pin assignments


Fiber Optics Cables

Fast Ethernet and Gigabit Ethernet can also be run over glass optical fibers. This can occur in two different ways:

• Single mode fiber (SMF)

• Multi mode fiber (MMF)


Single Mode Fiber (SMF)• Single Mode Fiber transmits data by means of a

laser through the optical fiber medium. This laser is projected in a straight line through the medium due to the laser's high speed and continuity. It is capable of higher bandwidth and greater cable run distances than multimode fiber. SMF connections spanning up to 2 kilometers


Multi Mode Fiber (MMF)• MMF uses LED to transmit light by

bouncing it off reflective surfaces within the cable walls. These modes of light can travel different distances, depending on the angle they enter the cable. This means that they will arrive at different times. (This phenomenon is called modal dispersion.)


Optical Fibre with ST Connector• Optical fibre is a glass fibre which can reflect light along a central

tube.• Specify fibre as multimode or single mode; multimode is much

cheaper to use but typically limited to 500m runs (single mode ~200km).

Many different connectors, eg ST, SC, LC, MRTJ.

ST and SC connectors ST connectorOptic fibre basics


A Wiring Closet

Optic fibre terminations

Copper terminations

Managed ethernetswitches


A Busier Wiring Closet!

•Colour coordinated cables;

• Order of panels:

• Optic fibre at top,• then copper RJ45,• then switches,• then media convertors.


Transmission

BroadcastingEthernet is a broadcast-based

environment. In this environment, all stations see all frames placed on the network. Following any transmission, each station must examine every frame to determine whether that frame was meant for it. Frames identified as intended for a given station are passed to a higher-layer protocol.


Media Access

The Ethernet media access uses the following process:

• Any station on a LAN can access the network at any time.

• Before sending data, stations listen for traffic on the network.

• A station waits until it detects no traffic before it transmits data.


Collision handling

• Ethernet is a "first come, first serve" environment. In fact, it was developed on a foundation known as Carrier Sense Multiple Access with Collision Detection or CSMA / CD. In such an environment, any station on the network can transmit whenever the network is quiet. A collision occurs when two stations listen for traffic, hear none, and then transmit data at the same time. Both transmissions are damaged, and the stations must retransmit at a later time. Backoff algorithms determine when the colliding stations should retransmit. These algorithms assign a random order number for each collision-involved station to retransmit the data.


Copper: Cat5e UTP with RJ45 Connectors• Cat5 is a basic cable standard – how many

strands, how thick, what twisting, how to insulate. Cat3 is used for analogue telephone lines; Cat5 is for basic ethernet, Cat5e is better. Some people are using Cat6 or Cat7 now.

• UTP: Unshielded Twisted Pair. 8 individual wires are twisted into 4 pairs and encased in a sheath. A superior (but expensive) alternative is STP: shielded twisted pair, where the pairs are wrapped in metal foil which is connected to earth at one end.

• RJ45: a standard design of plug, a little like a large telephone plug.

Engineering

Telecom lect 1