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BASIC TELECOMMUNICATIONS

BASIC TELECOMMUNICATIONS . Modems and Routers. BASIC TELECOMMUNICATIONS . We recently learned a little bit about routers as they pertain to WiFi , now we’re going to take a closer look at the function of a router in a network S hould we use a router or a modem to get to the WAN?

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BASIC TELECOMMUNICATIONS

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  1. BASIC TELECOMMUNICATIONS Modems and Routers

  2. BASIC TELECOMMUNICATIONS We recently learned a little bit about routers as they pertain to WiFi, now we’re going to take a closer look at the function of a router in a network Should we use a router or a modem to get to the WAN? Hint: cover photograph of today’s lesson Router Modem

  3. BASIC TELECOMMUNICATIONS Here we have the modem connected to the internet and the router is networked through the WAN port, this router also has two dedicated VoIP ports

  4. BASIC TELECOMMUNICATIONS Here is a typical home network set up

  5. BASIC TELECOMMUNICATIONS • A router is a device that is used to send data packets between different networks • A router is connected to two or more data lines from other networks • When a data packet comes in on one of the lines, the router reads the address information in the packet to determine its ultimate destination

  6. BASIC TELECOMMUNICATIONS • Using information in its routing table, it directs the packet to the next network on its journey • Routers perform the "traffic directing" functions on the Internet • Home and small office routers simply pass data, such as web pages and email, between the home computers and the owner's cable or DSL modem

  7. BASIC TELECOMMUNICATIONS More sophisticated routers, such as enterprise routers, connect large business or ISP networks up to the powerful core routers that forward data at high speed along the optical fiber lines of the Internet backbone Enterprise routers

  8. BASIC TELECOMMUNICATIONS • When multiple routers are used in interconnected networks, the routers exchange information about destination addresses, using a dynamic routing protocol. • Each router builds up a table listing the preferred routes between any two systems on the interconnected networks

  9. BASIC TELECOMMUNICATIONS • A router has interfaces for different physical types of network connections, (such as copper cables, fiber optic, or wireless transmission) • It also contains firmware for different networking protocol standards • Each network interface uses this specialized computer software to enable data packets to be forwarded from one protocol transmission system to another

  10. BASIC TELECOMMUNICATIONS • firmwareis the combination of persistent memory and program code and data stored in it • Typical examples of devices containing firmware are embedded systems (such as traffic lights, consumer appliances, and digital watches), computers, computer peripherals, mobile phones, and digital cameras • The firmware contained in these devices provides the control program for the device

  11. BASIC TELECOMMUNICATIONS • Routers also have a built in firewall which adds a level of protection to the network • Firewall devices are available for enterprise solutions as a stand alone device that adds many more layers of protection and can be configured for specific applications • The firewall function in a router is software based

  12. BASIC TELECOMMUNICATIONS • Afirewallcan either be software-based or hardware-based and is used to help keep a network secure • Its primary objective is to control the incoming and outgoing network traffic by analyzing the data packets and determining whether it should be allowed through or not, based on a predetermined rule set

  13. BASIC TELECOMMUNICATIONS A network's firewall builds a bridge between an internal network that is assumed to be secure and trusted, and another network, usually an external (inter)network, such as the Internet, that is not assumed to be secure and trusted

  14. BASIC TELECOMMUNICATIONS • A modem (modulator-demodulator) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information • The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data • Remember AOL dial up modems, excruciatingly slow

  15. BASIC TELECOMMUNICATIONS • Modems can be used over any means of transmitting analog signals, from light emitting diodes to radio Here is an evolution of modems Present day 1994 1970s

  16. BASIC TELECOMMUNICATIONS • A voice band modem that turns the digital data of a personal computer into modulated electrical signals in the voice frequency range of a telephone channel • These signals can be transmitted over telephone lines and demodulated by another modem at the receiver side to recover the digital data

  17. BASIC TELECOMMUNICATIONS • The voice band modem is the same as the old dial up modems that were rated for speeds of 56Kbps, at best most dial up users achieved a maximum of about 44Kbps • A modem requires a telephone number just like a POTS line and the same trouble shooting procedures can be applied to modems as that used for POTS lines • In contrast DSL provides 1.544Mbps and cable modems are even faster

  18. BASIC TELECOMMUNICATIONS • Modems are generally classified by the amount of data they can send in a given unit of time, usually expressed in bits per second (bps) • Modems can alternatively be classified by their symbol rate, measured in baud • The baud unit denotes symbols per second, or the number of times per second the modem sends a new signal

  19. BASIC TELECOMMUNICATIONS • For example, the ITU V.21 standard used audio frequency-shift keying (FSK), that is to say, tones of different frequencies, with two possible frequencies corresponding to two distinct symbols (or one bit per symbol), to carry 300 bits per second using 300 baud • the original ITU V.22 standard, which was able to transmit and receive four distinct symbols (two bits per symbol), handled 1,200 bit/s by sending 600 symbols per second (600 baud) using phase shift keying

  20. BASIC TELECOMMUNICATIONS • Baud was the prevalent measure for data transmission speed until replaced by a more accurate term, bps (bits per second). • In other words, one baud is one electronic state change per second. Since a single state change can involve more than a single bit of data, the bps unit of measurement has replaced it as a better expression of data transmission speed

  21. BASIC TELECOMMUNICATIONS Here is an example of what the bit and baud rates look like

  22. BASIC TELECOMMUNICATIONS • Amajor advance in modems was the Smartmodem, introduced in 1981 by Hayes Communications • The Smartmodem was an otherwise standard 103A 300-bit/s modem, but was attached to a small controller that let the computer send commands to it and enable it to operate the phone line

  23. BASIC TELECOMMUNICATIONS • The command set included instructions for picking up and hanging up the phone, dialing numbers, and answering calls.. • Prior to the Hayes Smartmodem, dial-up modems almost universally required a two-step process to activate a connection: • first, the user had to manually dial the remote number on a standard phone handset, and then secondly, plug the handset into an acoustic coupler

  24. BASIC TELECOMMUNICATIONS • With the Smartmodem, the computer could dial the phone directly by sending the modem a command, thus eliminating the need for an associated phone instrument for dialing and the need for an acoustic coupler. The Smartmodem instead plugged directly into the phone line • The basic Hayes command set remains the basis for computer control of most modern modems

  25. BASIC TELECOMMUNICATIONS • Almost all modern modems can interoperate with fax machines • Digital faxes, introduced in the 1980s, are simply a particular image format sent over a high-speed (commonly 14.4 kbit/s) modem • Software running on the host computer can convert any image into fax-format, which can then be sent using the modem

  26. BASIC TELECOMMUNICATIONS • Another term you should be familiar with is a Gateway which is very similar to a router • Agateway is any connection point or node on a network that provides access to a larger network and is essentially a modem and a router combined into one device, and does not need a modem to connect to the internet

  27. BASIC TELECOMMUNICATIONS • So depending on what level of networking you are operating on, a gateway is different and operates at layer 5 of the OSI model • For any home network connected to the Internet, the ISP server is the gateway to the Internet • That is why, a router integrating multiple networks together, acts as a gateway, however it operates at layer 3 of the OSI model

  28. BASIC TELECOMMUNICATIONS The OSI, or Open System Interconnection, model defines a networking framework for implementing protocols in seven layers. Control is passed from one layer to the next, starting at the application layer in one station, and proceeding to the bottom layer, over the channel to the next station and back up the hierarchy

  29. BASIC TELECOMMUNICATIONS This diagram shows the basic 7 layers of the OSI model LOGIC LINK CONTROL MEDIA ACCESS CONTROL

  30. BASIC TELECOMMUNICATIONS This model shows how the process flows through the OSI model

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