Introduction to Data Communications 5. Introduction to Networking
5. Introduction to Networking What is a Network? A network can consist of two computers connected together on a desk or it can consist of many Local Area Networks (LANs) connected together to form a Wide Area Network (WAN) across a continent.
The key is that 2 or more computers are connected together by a communication medium and they are sharing resources. The resources can be files, printers, hard-drives or cpu number crunching power.
5a. The Big Picture Many individuals have asked to see The Big Picture of networking: "where does everything fit in?". Where does operating systems fit in with routers and the OSI layers? What about different operating systems like Windows, UNIX, Linux and Novell? The following page has a graphic which attempts to show The Big Picture. It attempts to show the many areas of networking and data communication and how they tie into each other. Network Operating Systems (NOS) are software that runs on computer platforms (hardware) and controls the way the computer behaves. Communication and cabling protocols define the way data is passed from network to network. Storm Clouds represent telecommunications media that connect networks together. They form the backbone for data communications and the Internet Machines such as bridges and routers link together networks that have different purposes such as telecommunications networks and local area networks in order to pass information.
Telephony services such as private branch exchanges (PBX), public switched telephone network (PSTN) and Voice Over IP (VOIP) provide voice communications along with data communications. Television cable systems are providing data communications services and telephony services such as VOIP The Internet is the name for the complete network - all of the components connected together in almost a haphazardly fashion.
The Internet and data communications are dynamic entities that are constantly growing and evolving. By the time that you read these words, new technology and communications methods will have been added to the data communications to improve it - make it bigger, faster, better.
5b. The Big Picture Illustrated
5c. Breaking The Big Picture up! The Big Picture still doesn't give us a good idea of the placement of the many protocols involved in networking and telecommunications. The Big Picture can be broken up into the following 4 areas: i. ii. iii. iv. v.
Local Loop LANs MANs WANs. Telecommunications components
i. The Local Loop
The Local Loop is often called "the last mile" and it refers to the last mile of analog phone line that goes from the central office (CO) to your house. Typical local loop protocols are: Voice lines Modem connections 56 kbps ISDN (Integrated Services Digital Network) 2 x 64 kbps digital lines ADSL (Asymmetrical Digital Subscriber Line) up to 8 Mbps Cable Modems up to 30 Mbps
Note: Cable modems are not part of the Local Loop but do fall in the category of "the last mile" or how to get high speed digital communication to the premise (home). It would incredibly expensive to replace the existing cabling structure. All of these protocols are used to overcome the existing cabling limitations in the local loop and provide high speed digital data tranmission. The existing cabling was designed for voice communications and not digital.
ii. LANs Local Area Networks (LANs) are networks that connect computers and resources together in a building or buildings close together. The computers share resources such as hard-drives, printers, data, CPU power, fax/modem, applications, etc... They usually have distributed processing - means that there is many desktop computers distributed around the network and that there is no central processor machine (mainframe).
Location: In a building or individual rooms or floors of buildings or connecting nearby buildings together like a campus wide network like a college or university..
Components of a LAN The components used by LANs can be divided into cabling standards, hardware and protocols. Examples of cabling standards used on LANs are: Cat 3, 4 and 5 cables IBM Type 19 cabling standards EIA568A and 568B
Ethernet cabling standards: IEEE 802.3 (10Base5), IEEE 802.3a (10Base2), IEEE 802.3i (10BaseT) Unshielded Twisted Pair (UTP) Shielded Twisted Pair (STP) Connectors: RJ45, RJ11, Hermaphroditic connectors, RS232, DB25, BNC
Examples of hardware devices are: Network Interface Cards NICs Repeaters Ethernet Hubs or multiport repeaters Token Ring MultiStation Access Units (MSAUs), Control Access Units (CAUs) and Lobe Access Modules (LAMs) Bridges Brouters Routers Gateways Print servers File servers Switches
Examples of LAN protocols are: Ethernet frame types: Ethernet_II, Ethernet_SNAP, Ethernet_802.2, Ethernet_802.3 Media Access Control layer (MAC layer) Token Ring: IBM and IEEE 802.5 Logical Link Control Layer (LLC) IEEE 802.2 TCP/IP SMB, NetBIOS and NetBeui IPX/SPX Fiber Distributed Data Interchange (FDDI) Asynchronous Transfer Mode (ATM)
iii. MANs Metropolitan Area Networks (MANs) are networks that connect LANs together within a city. From The Big Picture, we see that telecommunication sevices provide the connection (storm clouds) between networks. Local telecommunication services provides the external connection for joining networks across cities. The main criteria for a MAN is that the connection between the LANs is through a local exchange carrier (the local phone company).
Location: Separate buildings distributed throughout a city. Examples of companies that use MANs are universities, colleges, grocery chains, gas stations, department stores and banks. The protocols that are used for MANs are quite different from LANs except for ATM which can be used for both under certain conditions. Examples of MAN protocols are: RS-232, V.35 X.25 (56kbps), PADs Frame Relay (up to 45 Mbps), FRADs Asynchronous Transfer Mode (ATM) ISDN (Integrated Services Digital Network) PRI and BRI Dedicated T-1 lines (1.544 Mbps) and Fractional T-1
T-3 (45 Mbps) and OC-3 lines (155 Mbps) ADSL (Asymmetrical Digital Subscriber Line) xDSL (many different types of Digital Subscriber Lines)
iv. WAN Wide Area Networks (WAN) are a communication system linking LANs between cities, countries and continents. The main difference between a MAN and a WAN is that the WAN uses Long Distance Carriers rather than Local Exchange carriers. Otherwise the same protocols and equipment are used as a MAN.
Location: City to city, across a country or across a continent. Wide Area Networks (WANs) connect LANs together between cities or across a country. The TransCanada Pipeline has a WAN that stretches from Alberta in the Western Provinces of Canada to Boston on the Eastern United States seaboard. The pipeline goes from Alberta to Ontario then through the States and ends up in Boston. The maintenance and control of the network resides in Calgary, Alberta.
v. Telecommunications Components of The Big Picture The Telecommunications component provides backbone services to connect LANs together and to provide voice communications. As soon as the data communications leaves the building, it is connect to a telco provider of some type and uses one of the following protocols. ISDN - Integrated Services Digital Network Private Branch Exchanges - PBXs, Key Systems Telcos - ATT, Bell Telephone, Sprint, Telus DataPac nd DataRoute - packet switching and analog switching WAN protocols Cell Relay - Digital packet switching WAN protocol
Frame Relay - Digital packet switching WAN protocol X.25 - Analog packet switching WAN protocol ATM - Asynchronous Transfer Mode WAN protocol ADSL - Asymmetrical digital subscriber line Public Switched Telephone Network (PSTN) Voice over IP (VOIP)
