Module II - Networking Fundimentals

Networking Terminology
Data Networks: Data networks developed as a result of business applications that were written for microcomputers. At that time microcomputers were not connected as mainframe computer terminals were, so there was no efficient way of sharing data among multiple microcomputers. It became apparant that sharing data through the use of floppy disks was not an efficient or cost-effective manner in which to operate business.
Businesses needed a solution that would successfully address the following three problems:
  • How to avoid duplication of equipment and resources
  • How to communicate efficiently
  • How to set up and manage a network
In the mid-1980s, new network technologies could not communicate with each other due to competition between companies. This often required old network equipment to be removed to implement new equipment.
One early solution was the creation of local-area network (LAN) standards. In a LAN system, each department of the company is a kind of electronic island. As the use of computers in businesses grew, it soon became obvious that even LANs were not sufficient. What was needed was a way for information to move efficiently and quickly, not only within a company, but also from one business to another. THe solution was the creation of metropolitan-area networks (MANs) and wide-area networks (WANs). Because WANs could connect user networks over large geographic areas, it was possible for businesses to communicate with each other accross great distances.
Data History:
The history of coputer networking is complex.
  • In the 1940s computers were large electromagnetical devices that were prone to failure.
  • In 1947 the invention of a semiconductor transistor opened up many possiblities for making smaller, more reliable computers.
  • In the 1950s mainframe computers, which wewre run by punched card programs, began to be used by large institutions
  • In the late 1950s the integrated circuit that combined several, then many, and now millions, of transistors on one small piece of simconductor was invented.
  • In the late 1960s and 1970s, smaller computers, called minicomputers came into existance. Still very large in modern standards.
  • In 1977 the Apple Computer Company introduced the microcomputer, also known as the personal computer.
  • In 1981 IBM introduced its first personal computer.
  • In the mid-1980s users with stand-alone computers started to share files using modems to connect to other computers. This was referred to as point-to-point, or dial-up communication.
  • This concept was expanded by the use of computers that were the central point of communication in a dial-up connection. These computers were clled bulletin boards.
  • Starting in the 1960s and continuing through te 70s, 80s, and 80s, the Department of Defense (DoD) developed large, reliable, wide-area networks (WANs) for military and scientific reasons.
  • The DoD's WAN eventlually became the Internet.
Some important dates:
1890s Bell invents the Telephone
1920s AM Radio developed
1939 FM Radio developed
1972 Ray Tomlinson creates e-mail program to send messages
1981 Term "Internet" assigned to set of connected set of networks
1982 The ISO releases OSI model and protocols
1983 TCP/IP becomes the universal language of the Internet
1984 CISCO Systems founded - Domain name service introduced
1991 Word Wide Web born
1996 The Internet covers the globe
Networking Devices:
Equipment that connects directly to a network segment is referred to as a device. These devices are broken up into two classifications:
  • End-User (computers, printers, scanners, and other devices that provide services directly to the user)
  • Network devices (devices that connect the end-user devices together to allow them to communicate
Network devices..
  • provide transport for the data that needs to be transferred between end-user devices.
  • provide extention of cable connections, concentration of connections, conversion of data formats, and manaagement of data transfers.
  • examples of network devices are repeaters, hubs, bridges, switches, and routers.
Host: The end-user can also be referred to as a Host. Hosts allow users to share, create and obtain information. Host devices are physically connected to the network media using a NIC. Hosts use the NIC connection to perform the tasks of sending e-mails, printing reports, scanning pictures, or accessing databases.
Repeater: network device used to regenerate a signal. Repeaters regenerate analog or digital signals distorted by transmission loss due to attenuaation. A repeater does not perform intelligent routing like a bridge or a router.
Hubs: concentrate connections. They take a group of hosts and allow the network to see them as a single unit. Active hubs not only concentrate hosts, but they also regenerate signals.
Bridges: convert network transmission data formats as well as perform basic data transmission management. Bridges, as the name implies, provide connections between LANs. Not only do bridges connect LANs, but they also perform a check on the data to determin wheter it should cross the bridge or not. This makes each part of the network more efficient.
Switches: add more intelligence to data transfer management. Not only can they determine whether data should remain on a LAN or not, but they can transfer the data only to the connection that needs the data. Another difference between a bridge and a switch is that a switch does not convert data transmission formats.
Routers: have all the capabilities of the network devices mentioned above. Routers can regenerate signals, concentrate multiple connections, convert data transmission formants, and manage data transfers. They can also connect to a WAN, which allows them to connect LANs that are separated by great distances. Non of the other devices provide this type of connection.
Network topology - Defines the structure of the network. Two parts to the topology are:
  • physical topology: which is the actual layou of the wire or media
  • logical topology: which defines how the media is accessed by the hosts for sending data.

Commonly used Logical Topologies:

  • bus topology uses a single backbone cable that is terminated at both ends. All the hosts connect directly to this backbone.
  • ring topology connets one host to the next and the last host to the first. This creates a physical ring of cable.
  • star topology connects all cables to a central point of concentration.
  • extended star topology links individual stars together by connecting the hubs and/or switches. This topology can extend the scope and coverage of the network.
  • hierarchial topology is similar to an extended star. Howver, instead of linking the hubs and/or switches together, thes system is linked to a computer that controls the traffic on the topology.
  • mesh topology is implemented to provied as much protection as possible from interruption of service. The use of a mesh topology in the networked control systems of a nuclear power plant would be an excellent example. As seen in the graphic, each host has its own connections to all other hosts. Altough the Internet has multiple paths to any one location, it does not adopt the full mesh topology.
Logical Topology of a network is how the hosts communicate across the medium. The two most common types of logical topologies are broadcast and token passing:
  • Broadcast Topology Simply means that each host sends its data to all other hosts and .....
  • Logical Topology is token passing. Token passing controls network access by passing an electronic token sequentially to each host. When a host recieves the token, that host can send data on the network. If the host has not data to send, it passes the token to the next host and the process repeats itself. Two examples of networks that use token passing are Token Ring and Fiber Distributed Data Interface (FDDI).
Network Protocols:
  • protocols enable nework communication from one host through the network to another host.
  • protocol is a formal description of a set of rules and conventions that govern a particular aspect of how devices on a network communicate.
  • without protocols, the computer cannot make or rebuild the stream of incoming bits from another computer into the origional format.
Protocols control all aspects of data communication, which include how...
  • the physical network is buuilt
  • computers connect to the network
  • the data is formatted for transmission
  • the data is sent
  • to deal with errors
These network rules are created and maintained by many different organizations and commmittees.
  • Institute of Electrical and Electronic Engineers (IEEE)
  • American National Standards Institute (ANSI)
  • Telecommunications Industry Association (TIA)
  • Electronic Industries Alliance (EIA)
  • International Telecommunications Union (ITU), formerly known as the Comité Consultatif International Téléphonique et Télégraphique (CITT)
Local-area Networks (LANs):
LANs consist of the following components:
  • Computers
  • Network Interface cards
  • Peripheral devices
  • Network....
LANs make it possible for businesses that use computer technology to locally share files and printers efficiently, and make internal communications possible. A good example of this technology is e-mail.
Some common LAN technologies are:
  • Ethernet
  • Token Ring
  • FDDI
LANs are designed to:
  • Operate within a limited geographic area
  • Allow muti-access to high-bandwidh media
  • Control the network privately under local administration
  • Provide full-time connectivity to local services
  • Connect physically adjacent devices
Wide-Area Networks (WANs):
Wans are designed to...
  • operate over a large geographical area.
  • allow access over serial interfaces operating at lower speeds.
  • provide full-time and part-time connectivity.
  • connect devices separated over wide, even global areas.
WANs interconnect LANs, which then provide access to computers or file servers in other locations. Because WANs connect user networks over a large geographical area, they make it possible for businesses to communicate across great distances. Using WANs allows computers, printers, and other devices on a LAN to share and be shared with distant locations. Wide-are networking has also created a new class of workers called telecommunicaters, people who never have to leave their homes to go to work.
Wans are designed to do the following:
  • Operate over large, geographically separated areas
  • Allow users to have real-time communication capabilities with other users
  • Provide full-time remote resources connected to local services
  • Provide e-mail, World Wide, Web, file transfer, and e-commerce services
Some common WAN technologies are:
  • Modems
  • Integrated Services Digital Network (ISDN)
  • Digital Subscriber Line (DSL)
  • Frame Relay
  • US (T) and Europe (E) Carrier Series - T1, E1, T3, E3
  • Synchronus Optical Network (SONET)
Metropolitan-Area Networks (MANs)
A MAN is a network that spans a metropolitan area such as a city or suburban area. A MAN usually consists of two or more LANs in a common geographical area.
Storage-Are Networks (SANs)
A SAN is a dedicated, high-performance network used to move data between servers and storage resources. Because it is a separate, dedicated network, it avoids any traffic conflict between clients and servers.
Virtual Private Network (VPN)
A VPN is a private network that is constructed within a public network infrastructure such as the global Internet. Usinv VPN, a telecommuter can access the network of the company headquarters through the Internet by building a secure tunnel between the telecommuter's PC and a VPN router in the headquarters.
There are three types of VPNS: Access VPNs, Intranet VPNs, and Extranet VPNs.
Intranets and Extranets
One common configuration of a LAN is an Intranet. Intranet Wreb servers differ from public Web servers in that the public must have the proper permissions and passwords to access the Intranet of an organization.
Extranets refer to applications and services that are Intranet based, and use extended, secure access to external users or enterprises. Therefore, an Extranet is the extention of two or more Intranet strategies with a secure interaction between participant enterprises and their respective intranets.
Bandwidth
Bandwidth is defined as the amount of information that can flow through a network connection in a given period of time. It is limited by physics and technology, is not free, and is crucial to network performance.
Bandwidth is finite. In other words, regardless of the media used to build the network, there are limits on the capacity of tht network to carry information. Bandwidht is limited by the laws of physics and by the technologies used to place information on the media. For example, the bandwidth of a conventional modem is limited to about 56kbps by both the physical properties of twisted-pair phone wires and by modem technology. However, the technologies employed by DSL also use the same twisted-pair phone wires, yet DSL provides much greater bandwidth than is available with conventional modems. So, even the limits imposed by the laws of physics are soetimes difficult to define. Optical fiber has the physical potential to provide virtually limitless bandwidth. Even so, the bandwidth of optical fiber cannot be fully realized until technologies are developed to take full advantage of its potential.
Bandwidth is not free. It is possible to buy equipment for a local-area network (LAN) that will provide nearly unlimited bandwidth over a long period of time. For WAN connections, it is almost always necessary to buy bandwidth from aservice provider. In either case, an understanding of bandiwdth and changes in demand for bandwidth over a given time can save an individual or a business a significant amount of money. A network manager needs to make the right decisions about the kinds of equipment and services to buy.
Bandwidth is a key factor in analyzing network performance, designing new networks, and understanding the internet. A networking professional must understand the tremendous impact of bandwidth and throughput on network performance and design. Information flows as a string of bits from computer to computer throughout the world. These bits represend massive amounts of information flowing back and forth across the globe in seconds or less.
The demand for bandwidth is ever increasing. As soon as net network technologies and infratstructures are built to provide greater bandwidth, new applictions are created to take advantage of the greater capacity. The delivery over the network of rich media content, including streaming video and audio, requires tremendous amounts of bandwidth. IP telephony systems are now commonly installed in place of traditional voice systems, which further adds to the need for bandwidth. The successful networkiung professional must anticipate the need for increased bandwidth and act accordingly.
Analogies of Bandwidth
Bandwidth is like the width of a pipe. A network of pipes brings fresh water to homes and businesses and carries waste water away. This water network is made up of pipes of different diameters. The main water pipes of a city may be two meters in diameter, while the pipe to a kitchen paucet may have a diameter of only two centimeters. The width of the pipe determines the amount of flow possible. The water is like data.
Bandwidth is like the number of lanes on a highway. A network of roads serves every city or town. Large highways with many traffic lanes are joined by smaller roads with fewer traffic lanes. These roads lead to even smaller, narrower roads, which eventually go to the driveways of homes and businesses. When fewer cars are on the road, they may move freely, but as traffic increases, congestion develops and the cars take longer to reach their destinations.
Measurement of Bandwidth
In digital systems, the basic unit of bandwidth is bits per second (bps). Bandwidth is the measure of how much information, in bits, can flow from one place to another in a given amount of time (seconds). Network bandwidth is typically described as thousands (kbps), millions (Mbps), billions (Gbps), and trillions (Tbps) of bits per second.
Limitations of Bandwidth
Typical Media Maximum Theoretical Bandwidth Maximum Theoretical Distance
50-Ohm Coaxial Cable
(10BASE2 Ethernet; Thinnet) 		10 Mbps 185 m
50-Ohm Coaxial Cable
(10BASE 5 Ethernet; Thicknet) 		10Mbps 500 M
Cat 5 Unshielded Twisted Pair (UTP)
(10BASE-T Ethernet) 		10 Mbps 100 m
Cat 5 Unshielded Twisted Pair (UTP)
(100BASE-TX Ethernet) 		100Mbps 100 m
Cat 5 Unshielded Twisted Pair (UTP)
(1000BASE-TX Ethernet) 		1000Mbps 100 m
Multimode Optical Fiber (62.5/125mm)
(100BASE-FX Ethernet) 		100Mbps 2000 m
Multimode Optical Fiber (62.4/125mm)
(1000BASE-SX Ethernet) 		1000Mbps 220 m
Multimode Optical Fiber (50/125mm)
(1000BASE-SX Ethernet) 		1000Mbps 550 m
WAN Service Typical User Bandwidth
Modem Individuals 56kbps
DSL Individuals, telecommuters, small businesses 128kbps - 6.1Mbps
ISDN Telecommuters, small businesses 128kpbs
Frame Relay Small institutions (schools), reliable WANs 56kbps - 44.736Mbps (US) or 34.368Mbps (Europe)
T1 Larger entities 1.544Mbps
E1 Larger entities 2.048Mbps
T3 Larger entities 44.736Mbps
E3 Larger entities 34.368Mbps
Throughput of Bandwidth
Throughput refers to actual measured bandwidth, at a specific time of day, using specific Internet routes, and while a specific set of data is transmitted on the network.
Variables That May Affect Throughput
  • PC (client)
  • Server
  • Other Users on LAN
  • Routing within the network cloud
  • Design of all networks involved
  • Type of data
  • Time of day (usage peaks, etc)
The following are some of the factors that determine throughput:
  • Internetworking devices
  • Type of data being transferred
  • Network topology
  • Number of users on network
  • User computer
  • Server computer
  • Power conditions
By measuring throughput on a regular basis, a network administrator will be aware of changes in network performacne and changes in the needs of network users. The network can then be adjusted accordingly.
Transfer Time Calculation
Best Download: T = (S/BW)
Typical Download: T = (S/P)
BW: Maximum theoretical bandwidth of the "slowest link" between the source host and destination host
P: Acutal throughput at the moment of transfer
T: Time for transfer to occur (seconds)
S: File size in Bits
Digital vs. Analog
Radio, television, and telephone transmissions have, until recently, been sent through the air and over wires using electromagnetic waves. These waves are called analog because they have the same shapes as the light and sound waves produced by the transmitters. As light and sound waves change size and shape, the electrical signal that carries the transmission changes proportionally. In other words, the electromagnetic waves are analogous to the light and sound waves.
Analog bandwidth is measured by how much of the electromagnetic spectrum is occuppied by each signal. The basic unit of analog bandwidth is hertz (Hz), or cycles per second. Typically, multiples of the basic unit of analog bandwidth are used, just as with digital bandwidth. Units of measurement that are commonly seen are KHz, MHz, and GHz.
While analog signals are capable of carrying a variety of information, they have some significant disadvantages in comparison to digital transmissions. The analog video signal that requires a wide frequency range for transmission cannot be squeezeed into a smaller band.
It is important to understand the differences and similarities between digital and analog bandwidth. Both types are regularly encountered in the field of IT. However, this course is primarily concerned with digital networking, so 'bandwidth' will refer to digital bandwidth.