Networking Basics

Module 2

Table of Contents

NetworkingTerminology

Bandwidth

Go There!

Go There!

Networking ModelsGo There!

Networking Terminology

Table of Contents

Data networks 2.1.1

Mainframe computers were connected to terminals

Did not share information with microcomputers Microcomputers were not connected to

mainframes Could not share information between

microcomputers Sneaker net was developed Copy data onto a floppy disk and carry disk to the

other user Not efficient if you modified the file Not cost effective

Networks were developed

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

1980’s tremendous expansion Problem each company developed it’s own software and

hardware specifications old equipment had to be replaced with each upgrade

Creation of LANs

Solution 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).

Network history 2.1.2

1940’s- computers were electromechanical devices

1950’s- mainframe computers used punch card programs for large institutions

1960’s-mainframes with terminals had integrated circuits were widely used

1970’s- minicomputers introduced like the Apple Computer Company

1981- IBM introduced it’s first personal computer, now Mac & IBM PC were widely used

Mid 1980’s- standalone computers shared files by modems connected to other computers

Starting in the 60’s through 90’s Department of Defense (DoD) developed large, reliable, wide-area networks (WAN) for military & scientific reasons

The DoDs WAN eventually became the Internet

Networking devices 2.1.3

Equipment that connects directly to a network segment is referred to as a device

End user devices are: Computers Printers Scanners Other devices that provide services directly to the

user

Hosts- End-user devices that provide users with a connection to the network

Allow users to share, create, and obtain information

Host devices are physically connected to the network media using a network interface card (NIC)

NIC is a printed circuit board that fits into the expansion slot of a bus on a computer motherboard, or it can be a peripheral device.

It is also called a network adapter Each individual NIC carries a unique code,

called a Media Access Control (MAC) address. This address is used to control data

communication for the host on the network.

Network devices provide transport for the data that needs to be transferred between end-user devices

Network devices provide extension of cable connections, concentration of connections, conversion of data formats, and management of data transfers

Examples of devices that perform these functions are repeaters, hubs, bridges, switches, and routers

Repeater

network device used to regenerate a signal Regenerate analog or digital signals distorted

by transmission loss due to attenuation Does not perform intelligent routing like a

bridge or router.

Hubs- Multiport repeater

Hubs concentrate connections Hubs 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 not only concentrate hosts, but

they also regenerate signals.

Bridges- Forward & Filter Mac addresses

Bridges convert network transmission data formats as well as perform basic data transmission management

Provide connections between LANs Perform a check on the data to determine

whether it should cross the bridge or not This makes each part of the network more

efficient

Switches- multi port bridges

Workgroup 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 that data

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

Routers

Routers have all the capabilities that bridges and switches have.

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 2.1.4

Network topology defines the structure of the network

One part of the topology definition is the physical topology, which is the actual layout of the wire or media

The other part is the logical topology, which defines how the media is accessed by the hosts for sending data

Physical topology

Bus topology Bus topology uses a single backbone cable that is

terminated at both ends All the hosts connect directly to this backbone.

Ring topology A ring topology connects one host to the next and

the last host to the first This creates a physical ring of cable

Star topology A star topology connects all cables to a central point

of concentration. Extended Star topology  

An 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

Hierarchical topology Similar to an extended star However, instead of linking the hubs and/or switches

together, the system is linked to a computer that controls the traffic on the topology

Mesh topology Implemented to provide as much protection as

possible from interruption of service each host has its own connections to all other

hosts Although the Internet has multiple paths to any one

location, it does not adopt the full mesh topology The use of a mesh topology in the networked control

systems of a nuclear power plant would be an excellent example

Logical topology

Logical topology of a network is how the hosts communicate across the medium

Two most common types of logical topologies Broadcast- ethernet

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

1st come, 1st serve token passing- Token Ring & FDDI (Fiber

Distributed Data Interface)

Token passing & FDDI

Token passing controls network access by passing an electronic token 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.

Network protocols 2.1.5

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.

Protocols determine the format, timing, sequencing, and error control in data communication.

Without protocols, the computer cannot make or rebuild the stream of incoming bits from another computer into the original format

Protocols determine

How the physical network is built How computers connect to the network How the data is formatted for transmission How that data is sent How to deal with errors

Organizations that maintain these network rules: 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 (CCITT)

Local Area Networks 2.1.6

LANs consist of the following components: Computers Network interface cards Peripheral devices Networking media Network devices

LANs

Operate within a limited geographic area Allow multi-access to high-bandwidth media Control the network privately under local

administration Provide full-time connectivity to local services Connect physically adjacent devices

Common LAN technologies

Ethernet Token Ring FDDI

Wide Area Networks 2.1.7

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 Provide e-mail, World Wide Web, file transfer,

and e-commerce services

WANs technologies

Modems Integrated Services Digital Network (ISDN) Digital Subscriber Line (DSL) Frame Relay US (T) and Europe (E) Carrier Series – T1, E1,

T3, E3 Synchronous Optical Network (SONET)

Metropolitan area networks 2.1.8

MAN- network that spans a metropolitan area such as a city or suburban area.

usually consists of two or more LANs in a common geographic area.

Typically, a service provider is used to connect two or more LAN sites using private communication lines or optical services.

MAN can also be created using wireless bridge technology by beaming signals across public areas

Storage area networks 2.1.9

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

SANs offer the following features:

Performance – SANs enable concurrent access of disk or tape arrays by two or more servers at high speeds, providing enhanced system performance.

Availability – SANs have disaster tolerance built in, because data can be mirrored using a SAN up to 10 kilometers (km) or 6.2 miles away.

Scalability – Like a LAN/WAN, it can use a variety of technologies. This allows easy relocation of backup data, operations, file migration, and data replication between systems.

Virtual private network 2.1.10

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

Using 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.

Benefits of VPNs 2.1.11

Offers secure, reliable connectivity over a shared public network infrastructure

Same security & management policies as a private network

Cost-effective for point-to-point connection between remote users & enterprise customer’s network

3 main types of VPNs

Access VPNs Intranet VPNs Extranet VPNs

Access VPNs

Access VPNs provide remote access to a mobile worker and small office/home office (SOHO) to the headquarters of the Intranet or Extranet over a shared infrastructure

Access VPNs use analog, dialup, ISDN, digital subscriber line (DSL), mobile IP, and cable technologies to securely connect mobile users, telecommuters, and branch offices

Intranet VPNs

Intranet VPNs link regional and remote offices to the headquarters of the internal network over a shared infrastructure using dedicated connections

Intranet VPNs differ from Extranet VPNs in that they allow access only to the employees of the enterprise

Extranet VPNs

Extranet VPNs link business partners to the headquarters of the network over a shared infrastructure using dedicated connections

Extranet VPNs differ from Intranet VPNs in that they allow access to users outside the enterprise

Intranets

One common configuration of a LAN is an Intranet

Intranet Web servers - the public must have the proper permissions and passwords to access the Intranet of an organization

Designed to permit access by users who have access privileges to the internal LAN of the organization

Example- your college or business intranet Web servers are installed in the network to

enable communication or sharing of files

Extranets

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

This access is usually accomplished through passwords, user IDs, and other application-level security.

Extranet is the extension of two or more Intranet strategies with a secure interaction between participant enterprises and their respective intranets.

Bandwidth

Table of Contents

Importance of bandwidth 2.2.1

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

Why bandwidth is important Limited by physics & technology Not free Requirements are growing at a rapid rate Critical to network performance

Analogies 2.2.2

Bandwidth is like the width of a pipe Bandwidth is also like the number of lanes on

a highway

Measurement 2.2.3

Bandwidth is the measure of how much information, or bits, can flow from one place to another in a given amount of time, or seconds

Can be measured in: Bits per second (bps) Thousands of bits per second (kbps) Millions of bits per second (Mbps) Billions of bits per second (Gbps) Trillions of bits per second (Tbps)

Limitations 2.2.4

Bandwidth varies depending upon the type of media as well as the LAN and WAN technologies used

Signals travel through twisted-pair copper wire, coaxial cable, optical fiber, and air

Throughput 2.2.5

Bandwidth is the measure of the amount of information that can move through the network in a given period of time

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

Factors that determine throughput

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

Data transfer calculation 2.2.6

Network designers & administrators make decisions regarding bandwidth

Should they increase size of the WAN connection to accommodate a new database

LAN backbone, does it have sufficient bandwidth for streaming-videos

Digital versus analog 2.2.7

Radio, television, and telephone transmissions have, until recently, been sent through the air and over wires using electromagnetic waves

waves are called analog because they have the same shapes as the light and sound waves produced by the transmitters

Measurement- Hertz (Hz), or cycles per second Kilohertz (KHz) Megahertz (MHz) Gigahertz (GHz)

Disadvantages of Analog signals

Can not carry as much information as digital Smaller band range If analog bandwidth not available, signal can

not be sent

Networking Models

Table of Contents

Layers to analyze problems 2.3.1

Layers to analyze problems 2.3.1

Layers to analyze problems 2.3.1

Layers to describe data comm 2.3.2

In order for data packets to travel from a source to a destination on a network, it is important that all the devices on the network speak the same language or protocol

A protocol is a set of rules that make communication on a network more efficient

For example, while flying an airplane, pilots obey very specific rules for communication with other airplanes and with air traffic control

OSI model 2.3.3

1980’s brought tremendous growth to networks Companies experienced problems with rapid expansion Problem: how to exchange information between

proprietary software and hardware ISO (International Organization for Standardization)

researched different models ISO created a network model that helps vendors create

networks that are compatible with other networks 1984- OSI (Open Systems Interconnection) released

OSI model Benefits

Reduces complexity Standardizes interfaces Facilitates modular engineering Ensures interoperable technology Accelerates evolution Simplifies teaching and learning

OSI layers 2.3.4

OSI reference model is a framework that is used to understand how information travels throughout a network

OSI reference model explains how packets travel through the various layers to another device on a network, even if the sender and destination have different types of network media

there are seven numbered layers

Advantages of layers

It breaks network communication into smaller, more manageable parts.

It standardizes 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 other layers.

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

OSI Layers

7 Application Network Processes to Applications I.e. e-mail, FTP

6 Presentation Format data & data structures, data syntax & transfer, readability

5 Session Interhost Communication- establishes, manages, & terminates sessions between applications

4 Transport End-to-end Connections, establish, maintain, terminate Virtual circuits, fault detection & recovery

3 Network Network Address & best path determination, flow control, error notification

2 Data Link Direct Link Control, Access to Media

1 Physical Binary Transmission- wires, connectors, voltages, data rates

Peer-to-peer comm. 2.3.5

In order 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

This form of communication is referred to as peer-to-peer

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

Data Encapsulation Process

Data packets on a network originate at a source and then travel to a destination

Each layer depends on the service function of the OSI layer below it.

To provide this service, the lower layer uses encapsulation to put the PDU from the upper layer into its data field; then it adds whatever headers and trailers the layer needs to perform its function

Next, as the data moves down through the layers of the OSI model, additional headers and trailers are added

Transport layer encapsulation

After Layers 7, 6, and 5 have added their information, Layer 4 adds more information. This grouping of data, the Layer 4 PDU, is called a segment

Network Layer encapsulation

The network layer provides a service to the transport layer, and the transport layer presents data to the internetwork subsystem.

The network layer has the task of moving the data through the internetwork.

Network layer encapsulation

It accomplishes this task by encapsulating the data and attaching a header creating a packet (the Layer 3 PDU).

The header contains information required to complete the transfer, such as source and destination logical addresses

Data Link layer encapsulation

The data link layer provides a service to the network layer. It encapsulates the network layer information in a frame (the Layer 2 PDU).

The frame header contains information (for example, physical addresses) required to complete the data link functions.

The data link layer provides a service to the network layer by encapsulating the network layer information in a frame

Physical layer encapsulation

The physical layer also provides a service to the data link layer. The physical layer encodes the data link frame into a pattern of 1s and 0s (bits) for transmission on the medium (usually a wire) at Layer 1.

TCP/IP model 2.3.6

historical and technical standard of the Internet is the TCP/IP model

The U.S. Department of Defense (DoD) created the TCP/IP reference model, because it wanted to design a network that could survive any conditions, including a nuclear war.

In a world connected by different types of communication media such as copper wires, microwaves, optical fibers and satellite links, the DoD wanted transmission of packets every time and under any conditions

TCP/IP was developed as an open standard.

Encapsulation process

Data Segments Packets Frames Bits

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