Telecommunications & Networks

Lally School of M&T- MicroComputing Lecture Topics 1. Telecommunication Networks 2. Network Components 3. Network Topologies 4. Network Protocols 5. Network Types 6. Network Architectures

Lally School of M&T- MicroComputing Communication Networks A system that is set up for the communication of information from one location to another. Example: The mail system in the old west. Telecommunication Networks or just Networks A system that is set up for the communication of information by electronic means. Example: The transmission of information between personal computers

Lally School of M&T- MicroComputing Network Components 1. Sender and receiver 2. Channel 3. Message 4. Noise SenderReceiver Channel Noise

Lally School of M&T- MicroComputing 1. Sender and Receiver These are input and output devices like Pcs, handheld computers, terminals etc that send or receive information.

Lally School of M&T- MicroComputing 2. Channels – Channel Mediums Channel Medium A telecommunications channel is the medium used to send information from the sender to the receiver. In older communication channels this medium was the mailperson used to carry the messages from New York to Los Angeles. 1. Twisted pair (cat 5 shown here) – looks similar to telephone cable – has square plastic RJ-45 connector 2. Coaxial cable – resembles cable-TV cable – round, silver BNC connector

Lally School of M&T- MicroComputing Channels 3. Fiber-optic cable is a bundle of extremely thin tubes of glass Each optical fiber (tube) is thinner than a human hair Consists of strong inner support wire, multiple strands of optical fiber and a tough outer cable Transmit pulses of light USB, serial, parallel, SCSI, and Firewire connections 4. Infrared light can also carry data signals, but for short distances with a clear line of sight. Best for transmitting between notebook computers and a printer, or between a PDA and a desktop computer

Lally School of M&T- MicroComputing Channels Channel Characteristics 1. Transmission Rate The rate at which a channel transfers data from one computer to another. Measured in bits per second. 2. Bandwidth The maximum volume of data the network can carry. 3. Transmission Mode (Two modes) 1. Asynchronous Transmission Data is transmitted one byte at a time. Like a mailperson carrying one letter at a time. Every byte has a starting bit and an ending bit so that the receiver knows when a byte begins and when it ends. 2. Synchronous Transmission Data is transmitted as blocks of bytes at a time which is faster than asynchronous transmission.

Lally School of M&T- MicroComputing Channels 4. Transmission Direction (Three directions) Simplex: A device can send or receive data but not do both like in TV sets. Half-Duplex: The sender and receiver devices can alternate in sending and receiving data like in walkie-talkies. Full Duplex: Both sender and receiver devices can send and receive data at the same time like in the phone.

Lally School of M&T- MicroComputing Channels 4. Transmission Signal (Two types) Information transfers through the channel in the form of electromagnetic signals. Analog Signals: These are continuous signals represented as waves. Eg. temperature or telephones. Messages are transmitted by changing the amplitude and frequency of waves. Digital Signals: These are represented in the form of zeros and ones and are the way computers transmit information. Less susceptible to channel noise.

Lally School of M&T- MicroComputing Analog Signal Specifics Frequency Wavelength Amplitude

Lally School of M&T- MicroComputing Messages and Packets When you transmit data, it is broken up into small pieces called packets A packet is a parcel of data that is sent across a network Has the address of its sender Has the address of the receiver Has some data When they reach the destination, they are put back together into their original form.

Lally School of M&T- MicroComputing Network Topologies Star Topology Bus Topology Ring Topology The geometric configuration of devices in the network.

Lally School of M&T- MicroComputing Network Topologies - Bus Bus Topology Connects all devices in the network to a central channel. Signals from devices are intercepted from all other devices but only the addressed device will respond. There is no central host or server. The channel in the network can handle one message at a time. Advantages: Makes it easy to add or remove devices from the network without affecting network performance. If one of the devices in the network fails, the network will not fail. Disadvantages The network performance decreases as the number of devices in the network increases because each device checks to see if the signal transmitted from another device is for it or not If two devices send a message at the same time, a “message collision” will occur and the messages will need to be resent.

Lally School of M&T- MicroComputing Network Topologies-Ring Ring Topology Devices are arranged in a ring. A device can communicate directly with any other device in the network. There is no central host or server for the network. Advantages: If one of the devices in the network fails, the network will not fail.

Lally School of M&T- MicroComputing Network Topologies-Star Star Topology There is a central server or host in the network. Applied when some processing should be centralized and some of it left on the devices. Signals between devices (messages) absolutely go through the central host which functions as the traffic controller. The channel in the network can handle one message at a time. Advantages: Makes it easy to add or remove devices from the network. If one of the devices in the network fails, the network will not fail. Disadvantages If the central host fails, the network will fail. Also as the distance between the host and any device increases, the cost increases significantly.

Lally School of M&T- MicroComputing Network Protocols Three major components of a protocol: A set of characters that mean the same for the sender and receiver. A set of rules for timing and sequencing messages. A set of methods for detecting and correcting errors.

Lally School of M&T- MicroComputing Network Protocol Examples

Lally School of M&T- MicroComputing Ethernet Ethernet (10 Mbs). Node listens to cable and transmits when everything is clear. If collision occurs, nodes will attempt again after a random period of time. Fast Ethernet (100 Mbs). Gigabit Ethernet (1GB). 10 Gigabit Ethernet

Lally School of M&T- MicroComputing Protocol Type – Token Ring Token Ring. A single electronic token moves around the ring. If a node wishes to transmit waits for an empty token and attaches data to it.

Lally School of M&T- MicroComputing How do I set up a simple LAN?

Lally School of M&T- MicroComputing Network Types LAN (Local Area Networks) A network that links devices in a local area and within a radius of 2000 feet. They use bus or ring topologies Used to share resources in an office such as printers, scanners, file servers etc. They require extensive wiring. A solution to that nowadays is to create a wireless LAN. LANs communicate with other LANs through gateways that can translate protocol standards from one network to the other. For one LAN to access the resources of another bridges or routers are used if the distance increases.

Lally School of M&T- MicroComputing Network Types WAN (Wide Area Networks) Span from several miles to entire continents Lines might be leased or purchased Integrated Services Digital Network (ISDN) Transmitting data over a phone line

Lally School of M&T- MicroComputing Network Types Virtual Private Networks (VPNs): How do they work Through Public Mediums Tunneling Cost Reduction Cost savings on the calls (1K to 2K per call per person) Operating Costs of supporting remote users Modem pools Other support Elimination of dedicated lines No need for multiple access lines Savings increase if company is decentralized geographically Flexibility

Lally School of M&T- MicroComputing Network Architecture Client Server Peer-To-Peer

Lally School of M&T- MicroComputing Network Architecture Client Server Fat Client Fat Server Three-Tier (Distributed) Multi-tier (Distributed)

Lally School of M&T- MicroComputing Client Server Network Architecture Three-Tier (Distributed)

Lally School of M&T- MicroComputing Client Server Network Architecture Fat Server

Lally School of M&T- MicroComputing Client Server Network Architecture Fat Client

Lally School of M&T- MicroComputing Client Server Network Architecture Internet Implementation