Networking Fundamentals

CMPSC 255Fall 2004

Aims

By the end of this Module you should be able to: Briefly outline the history of networking. Identify devices used in networking. Understand the role of protocols in networking. Define LAN, WAN, MAN, and SAN. Explain VPNs and their advantages. Describe the differences between intranets and extranets. Explain bandwidth in networking as units of measurement. Explain the difference between bandwidth and throughput. Calculate data transfer rates. Describe the OSI Model in relation to Layers, Functions, Protocols and Devices Identify the four layers of the TCP/IP model and describe the similarities and

differences between the two models.

Network Evolution

Sneakernet Used when few computers

were available Stand alone computers Files transferred by copying

to disk and physically delivering it to destination

Makes it difficult to track current file version

Wastes time

Network Evolution

Local Area Networks Connected computers on a

shared medium Enabled users to share files

electronically More efficient Standards developed to allow

equipment from different vendors to interoperate

Network Evolution

Wide Area Networks As corporations grew wider

communication was needed Each branch of a corporation

became isolated Files sent by post or courier

Solution WAN standards developed Companies were able to

communicate with other networks globally

Network Terminology

Network Devices

Topologies

Network Topologies Describe Structure of the network Physical Layout of Cabling (Physical Topology) How the media is accessed by communicating hosts (Logical

Topology) Common Physical Topologies

Bus Topology

Uses a single backbone cable that is terminated at both ends.

All the hosts connect directly to this backbone Bandwidth is shared between the number of hosts

on Network Can be Logical or Physical

Star Topology

A star topology connects all cables to a central point of concentration

Can be a Logical Bus or Ring Concentrator can be a

Hub Switch MSAU

Ring Topology

Connects one host to the next and the last host to the first

This creates a physical ring of cable Can be Logical or Physical

Extended Star Topology

Links individual star wired network segments together

Uses hubs and/or switches This topology can extend the scope and coverage of

the network

Hierarchical Topology

Similar to an extended star 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

The use of a mesh topology in the networked control systems of a nuclear power plant would be an excellent example

Each host has its own connections to all other hosts. Internet has multiple paths to any one location but it does not

adopt the full mesh topology.

Logical Topologies

Defines how the hosts communicate across the medium The two most common types of logical topologies are:

Broadcast topology means that 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

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. Two examples of networks that use token passing are Token Ring and Fiber Distributed

Data Interface (FDDI). A variation of Token Ring and FDDI is Arcnet. Arcnet is token passing on a bus

topology.

Network Protocols

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

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.

Protocols control data communication, which include the following:

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

Network Protocols

Protocols are created and maintained by organizations and committees such as: Institute of Electrical and Electronic Engineers (IEEE) American National Standards Institute (ANSI) Telecommunications Industry Association (TIA) Electronic Industries Alliance (EIA) International Telecommunications Union (ITU)

Local Area Networks (LANs)

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

LAN Components

LANs are designed to: Operate in a limited geographical area Allow multiple access to high-bandwidth media Control the network privately under local administrative control Provide full time connectivity to local services Connect physically adjacent devices

WAN Components

WANs are designed to: Operate over a large geographical area Allow access over serial interfaces at lower speeds Provide full and part time connectivity Connect devices separated over wide, even global areas

LAN and WAN Technologies

Common LAN technologies are: Ethernet Token Ring FDDI

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 Synchronous Optical Network (SONET)

Metropolitan Area Network

A 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.

A service provider is used to connect two or more LAN sites

Can also be created using wireless technology

Storage Area Network

A dedicated, high-performance network used to move data between servers and storage resources.

SAN technology allows high-speed server-to-storage,

Offers the following features: Availability Scalability

Virtual Private Networks

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

Uses a secure tunnel through the Internet between the telecommuter’s PC and a VPN router in the headquarters

Intranet and Extranet VPNs

Bandwidth

Why Bandwidth is important Bandwidth is limited by Physics and Technology

Regardless of the media used to build the network there are limits on the capacity of that network to carry information.

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

Bandwidth is not freeWAN connectivity must be purchased from a service provider

Bandwidth requirements are growing at a rapid rateMore and more companies are using WAN services which require more and

more bandwidth Bandwidth is critical to network performance

The higher the bandwidth the more information can be transferred in a shorter time

Bandwidth

Bandwidth Analogy 1

Bandwidth

Bandwidth Analogy 2

Bandwidth

Units of Bandwidth Bandwidth is the measure of how much information, or bits, can flow

from one place to another in a given amount of time Although bandwidth can be described in bits per second, usually

some multiple of bits per second is used.

Limitations

Bandwidth is limited by a number of factors Media Network devices Physics

Each have their own limiting factorsActual bandwidth of a network is determined

by a combination of the physical media and the technologies chosen for signaling and detecting network signals

Media bandwidth and limitations

Media Max Length Max Bandwidth50 Ohm Coaxial Cable(10Base2) Thin Ethernet

185m 10Mbps

50 Ohm Coaxial Cable(10Base5) Thick Ethernet

500m 10Mbps

Category 5 Unshielded Twisted Pair (UTP)(10BaseT) Ethernet

100m 10Mbps

Category 5 Unshielded Twisted Pair (UTP)(100BaseTX) Ethernet

100m 100Mbps

Category 5 Unshielded Twisted Pair (UTP)(1000BaseTX) Ethernet

100m 1000Mbps

Multimode Optical Fibre62.5/125mm 100BaseFX Ethernet

2000m 100Mbps

Multimode Optical Fibre62.5/125mm 1000BaseSX Ethernet

220m 1000Mbps

Multimode Optical Fibre50/125mm 1000BaseSX Ethernet

550m 1000Mbps

Single mode Optical Fibre9/125mm 1000BaseLX Ethernet

5000m 1000Mbps

Throughput

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.

Is determines by the following factors Internetworking devices Type of data being transferred Network topology Number of users on the network User computer Server computer Power conditions

Transfer Time Calculation

Data Transfer Calculation Best Download: T=S/BW Typical Bandwidth: T=S/P

Where T = Transfer time in seconds S = Size of file in Bits BW = Maximum theoretical bandwidth (slowest link

between source and destination devices P = Actual throughput at moment of transfer in Bps

Layered models

Using a layered model Breaks network communication into smaller, more

manageable parts. Standardizes network components to allow multiple vendor

development and support. Allows different types of network hardware and software to

communicate with each other. Prevents changes in one layer from affecting other layers. Divides network communication into smaller parts to make

learning it easier to understand.

OSI Model

Open Standards Interconnection Model (OSI Model) Released by International

Standards Organisation (ISO) in 1984

Standardised communications between different vendor hardware and software

Consists of 7 Layers Each layer described a specific

aspect of network communication

Layer 1

The physical layer is concerned with transmitting raw bits over a medium Wires Connectors Voltages Data rates

Layer 2

Controls the direct link to the media

How media is accessed Physical addressing Network topology Flow control Error Notification

Layer 3

Logical Addressing Best Path Determination

“Best Effort” delivery of data between networks

Layer 4

End-to-end Connections Concerned with transportation

issues between hosts Reliable delivery of data Establishes, maintains and

terminates virtual circuits Error recovery and data flow

Layer 5

Host to host communication Establishes, manages and

terminates sessions between applications

Layer 6

Data representation Ensure data is readable with

receiving system Data format Data Structure Negotiates data transfer

syntax for application layer

Layer 7

Provides network services for applications e-mail, file transfer, terminal

emulation

Peer to Peer Communication

Host 1 Host 2

TCP/IP Model

Developed by the US DoD Designed as an open

standard Is robust enough to

survive any conditions (even nuclear war)

Is the standard used for communication on the Internet

TCP/IP Vs OSI

TCT/IP OSI

Labs

Lab 2.3.6 OSI Model and TCP/IP Model

Lab 2.3.7 OSI Model Characteristics and Devices

TCP/IP Protocols

Protocols and TCP/IP

Data Encapsulation

Analog Vs Digital

Is measured by how much of the electromagnetic spectrum is occupied by each signal

The basic unit of analog bandwidth is hertz (Hz) Units of measurement that are commonly seen are

kilohertz (KHz) megahertz (MHz) gigahertz (GHz).

These are the units used to describe the bandwidths of cordless telephones

Operate at either 900 MHz or 2.4 GHz. These are also the units used to describe the bandwidths of

IEEE 802.11a and 802.11b wireless networks operate at 5 GHz and 2.4 GHz.