dinisoft 1 Chapter 2

Networking Fundamentals

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Objectives

• Networking terminology

• Bandwidth

• Networking models

Data Networks

• Developed as a result of business applications that were written for microcomputer

• The microcomputers were not connected so there was no efficient way to share data among them

• It was not efficient or cost-effective for businesses to use floppy disks to share data

• 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

• Data networking solutions– Local-area networks– Wide-area networks

Networking History

• The history of computer networking is complex• It has involved many people from all over the world over

the past 35 years • In the 1940s computers were large electromechanical

devices that were prone to failure• In 1947 the invention of a semiconductor transistor

opened up many possibilities for making smaller, more reliable computers

• In the 1950s large institutions began to use mainframe computers, which were run by punched card programs

• In the 1960s mainframes with terminals and integrated circuits were widely used.

• In the late 1960s and 1970s smaller computers called minicomputers were created

• In the mid-1980s PC users began to use modems to share files with other computers. This was referred to as point-to-point, or dial-up communication

• In 1977 the Apple Computer Company introduced the microcomputer, which was also known as the Mac.

• In 1981 IBM introduced its first PC• The user-friendly Mac, the open-architecture IBM PC,

and the further micro-miniaturization of integrated circuits led to widespread use of personal computers in homes and businesses

• From the 1960s to the 1990s the U.S. Department of Defense (DoD) developed large, reliable, wide-area networks (WANs) for military and scientific reasons

Networking History

Networking Devices

• Equipment that connects directly to a network segment is referred to as a device. These devices are broken up into two classifications. The first classification is end-user devices. The second classification is network devices.

Repeater

• A repeater is a network device used to regenerate a analog or digital signals that are distorted by transmission loss due to attenuation

• A repeater does not make intelligent decision concerning forwarding packets like a router or bridge

Hub

• Hubs concentrate connections• In other words, they take a group of hosts and allow the

network to see them as a single unit• This is done passively, without any other effect on the data

transmission• Active hubs concentrate hosts and also regenerate signals.

Bridge

• Bridges convert network data formats and perform basic data transmission management

• Bridges provide connections between LANs• Bridges also check data to determine if it should cross the

bridge• This makes each part of the network more efficient.

Switch

• Switches add more intelligence to data transfer management

• They can determine if data should remain on a LAN and transfer data only to the connection that needs it

• Another difference between a bridge and switch is that a switch does not convert data transmission formats

Router

• Routers have all the capabilities listed above• Routers can regenerate signals, concentrate multiple

connections, convert data transmission formats, and manage data transfers

• They can also connect to a WAN, which allows them to connect LANs that are separated by great distances

• None of the other devices can provide this type of connection

Network Topology

• Network topology defines the structure of the network. The physical topology, which is the actual layout of the wire or media, and the logical topology, which defines how the media is accessed by the hosts for sending data.

Physical Topology

• A bus topology uses a single backbone cable that is terminated at both ends. All the hosts connect directly to this backbone

• A ring topology connects one host to the next and the last host to the first. This creates a physical ring of cable.

• A star topology connects all cables to a central point. • An extended star topology links individual stars together

by connecting the hubs or switches. • A hierarchical topology is similar to an extended star.

However, instead of linking the hubs or switches together, the system is linked to a computer that controls the traffic on the topology

Logical Topology

Broadcast topology

• Each host sends its data to all other hosts on the network medium

• There is no order that the stations must follow to use the network

• It is first come, first serve. Ethernet works this way as will be explained later in the course.

Token passing

• An electronic token is passed sequentially to each host• When a host receives the token, that host can send data

on the network• If the host has no data to send, it passes the token to the

next host and the process repeats itself Examples: Token Ring and Fiber Distributed Data

Interface (FDDI)

Network Protocols

• A protocol is a formal description of a set of rules and conventions that govern a particular aspect of how devices on a network communicate

• Protocol suites are collections of protocols that enable network communication from one host through the network to another host

• Rules are created and maintained by many different organizations and committees:

- The Institute of Electrical and Electronic Engineers (IEEE)

- American National Standards Institute (ANSI)

- Telecommunications Industry Association (TIA)

- Electronic Industries Alliance (EIA)

- International Telecommunications Union (ITU)

LANs

• Operate within a limited geographic area• Allow many users to access high-bandwidth media• Provide full-time connectivity to local services• Connect physically adjacent devices

LAN Components

• Computers • Network interface cards • Peripheral devices • Networking media

• Network devices

LAN Technologies

• Ethernet• Token Ring • Fiber distributed data interface (FDDI)

LAN Devices

WAN Technologies

• Analog modems• Integrated Services Digital Network (ISDN)• Digital Subscriber Line (DSL)• Frame Relay• Asynchronous Transfer Mode (ATM)• T (US) and E (Europe) carrier series: T1, E1, T3, E3• Synchronous Optical Network (SONET)

WAN Devices

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 geographic area.

Storage-Area 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 Networks (VPNs)

• A VPN is a private network that is constructed within a public network infrastructure such as the global Internet

Benefits of VPNs

• A VPN is a service that offers secure, reliable connectivity over a shared public network infrastructure such as the Internet.

• VPNs maintain the same security and management policies as a private network.

• They are the most cost-effective method of establishing a point-to-point connection between remote users and an enterprise customer's network.

VPN Types

There are three main types of VPNs:• Intranet VPNs • Extranet VPNs • Access VPNs

Intranets and Extranets

• Intranets are designed to permit access by users who have access privileges to the internal LAN of the organization

• Extranets refer to applications and services that are Intranet based, but that use extended, secure access to external users or enterprises

Bandwidth

• Bandwidth is defined as the amount of information that can flow through a network connection in a given period of time

• Bandwidth is limited by the laws of physics and by the technologies used to place information on the media

Example: Bandwidth of a conventional modem is limited to about 56 kbps

Importance of Bandwidth

Digital Bandwidth

• Two analogies that describe digital bandwidth– Width of a pipe– Number of lanes on a highway

• Media bandwidth differences– Category 5 UTP – 100 meters maximum physical

distance– Multimode (62.5/125um) optical fiber – 2000

meters– Modem – 56 kbps = 0.056 Mbps– T1 – 1.544 Mbps

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

• Throughput is often far less than the maximum possible digital bandwidth of the medium that is being used

• Factors that determine throughput are:

- Internetworking devices - Type of data being transferred- Network topology- Number of users on the network- User computer- Server computer

Bandwidth Pipe Analogy

Bandwidth Highway Analogy

Bandwidth Measurements

Media Bandwidth

Digital Transfer Calculation

Digital vs. Analog

• Analog bandwidth is measured by how much of the electromagnetic spectrum is occupied by each signal

• In digital signaling, all information is sent as bits,

regardless of the kind of information it is.

Using Layers to Describe Communication

• Source, destination, and data packets– All communications originate at a source and travel

to a destination.– Information that travels on a network is referred to as

a data, packet, or data packet.

Using Layers to Describe Communication

• Media– Telephone wires (UTP)– Category 5 UTP (used for 10BASE-T Ethernet)– Coaxial cables– Optical fibers (thin glass fibers that carry light)

• Protocol – All devices on a network need to speak the same

language.– Set of rules that makes communication both possible

and more efficient.

The Purpose of the OSI Reference Model

• It breaks network communication into smaller, simpler parts that are easier to develop

• It facilitates standardization of network components to allow multiple-vendor development and support

• It allows different types of network hardware and software to communicate with each other

• It prevents changes in one layer from affecting the other layers so that they can develop more quickly

• It breaks network communication into smaller parts to make learning it easier to understand

Seven Layers of the OSI Reference Model

• Layer 7: Application• Layer 6: Presentation• Layer 5: Session• Layer 4: Transport• Layer 3: Network• Layer 2: Data link• Layer 1: Physical

Why a Layered Model?

Layers with Functions

The Seven Layers of the OSI Reference Model

• The application (upper) layers– Layer 7: Application– Layer 6: Presentation– Layer 5: Session

• The data-flow (lower) layers– Layer 4: Transport– Layer 3: Network– Layer 2: Data link– Layer 1: Physical

The Application (Upper) Layers• Application

– User interface– Examples – Telnet, HTTP

• Presentation– How data is presented– Special processing, such as encryption– Examples – ASCII, EMCDIC, JPEG

• Session– Keeping different applications’ data separate– Examples – Operating system/application access

scheduling

The Data-Flow (Lower) Layers

• Transport – Reliable or unreliable delivery– Error correction before transmit– Examples: TCP, UDP, SPX

• Network– Provide logical addressing which routers use for path

determination– Examples: IP, IPX

The Lower Layers (cont.)

• Data link– Combines bits into bytes and bytes into frames– Access to media using MAC address– Error detection not correction– Examples: 802.3/802.2, HDLN

• Physical– Moves bits between devices– Specifies voltage, wire speed, and pin out cables– Examples: EIA/TIA-232, V.35

The OSI Model

• Application – Think of browsers.• Presentation – Think of common data format.• Session – Think of dialogs and conversations.• Transport – Think of flow control and reliability.• Network – Think of path selection, routing, and logical

addressing.• Data Link – Think of frames and media access control.• Physical – Think of signals and media.

Peer-to-Peer Communication

• For data to travel from the source to the destination, each layer of the OSI model at the source must communicate with its peer layer at the destination.

• During this process, the protocols of each layer exchange information, called protocol data units (PDUs), between peer layers.

• Each layer of communication on the source computer communicates with a layer-specific PDU, and with its peer layer on the destination computer.

The TCP/IP Reference Model

TCP/IP Protocol Graph

Applications

• FTP – File Transfer Protocol• HTTP – Hypertext Transfer Protocol• SMTP – Simple Mail Transfer Protocol• DNS – Domain Name System• TFTP – Trivial File Transfer Protocol

OSI Model and TCP/IP Model

Use of the OSI Model in the CCNA Curriculum

Encapsulation The lower layers use encapsulation to put the protocol data unit (PDU) from the upper layer into its data field and to add headers and trailers that the layer can use to perform its function.

Names for Data at Each Layer

De-Encapsulation

• When the data link layer receives the frame, it does the following:– It reads the physical address and other control

information provided by the directly connected peer data link layer.

– It strips the control information from the frame, thereby creating a datagram.

– It passes the datagram up to the next layer, following the instructions that appeared in the control portion of the frame.

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