networks basics

Networking Basics

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AgendaAgendaOverview

What is a Network?

Establishing Network Connectivity

OSI Model

Physical Components

DataLink Protocols

Network Protocols

Other Terms and Definitions


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What is a Network?What is a Network?

A network consists of 2 or more computers connected together, and they can communicate and share resources (e.g. information)


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How can I connect two PC’s ?How can I connect two PC’s ?


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Why Networking?Why Networking?

• Sharing information — i.e. data communication

• Do you prefer these?

• Or this?


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Cont ……..Cont ……..• Sharing hardware or software

• E.g. print document

• Centralize administration and support

• E.g. Internet-based, so everyone can access the same administrative or support application from their PCs


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How many kinds of Networks?How many kinds of Networks?• Depending on one’s perspective, we can classify

networks in different ways

• Based on transmission media: Wired (“UTP,STP”(TP), coaxial cables, fiber-optic cables) and Wireless

• Based on network size: LAN and WAN (and MAN)

• Based on management method: Peer-to-peer and Client/Server

• Based on topology (connectivity): Bus, Star, Ring ,Mesh…

:

:


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Transmission MediaTransmission MediaTwo main categories:

• Guided ― wires, cables

• Unguided ― wireless transmission, e.g. radio, microwave, infrared, sound, sonar

We will concentrate on guided media here:

• Twisted-Pair cables:

- Unshielded Twisted-Pair (UTP) cables

- Shielded Twisted-Pair (STP) cables

• Coaxial cables

• Fiber-optic cables


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Twisted Pair CableTwisted Pair Cable

• Consists of 4 to 8 color-coded wires

• Each pair is twisted to reduce the effects of crosstalk on the wire

• Crosstalk occurs when signals on nearby wires cross over and interfere with the signal traveling on each wire

• Two types of twisted pair wire, shieldedshielded and unshieldedunshielded

- Shielded twisted pair (STP)Shielded twisted pair (STP) is insulated to reduce noise on the wire

- Unshielded twisted pair (UTP)Unshielded twisted pair (UTP) is more common and less expensive than STP

Twisted-Pair CablesTwisted-Pair Cables


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Unshielded Twisted-Pair (UTP)Unshielded Twisted-Pair (UTP)

Typically wrapped inside a plastic cover (for mechanical protection)

A sample UTP cable with 5 unshielded twisted pairs of wires

MetalInsulator


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Shielded Twisted-Pair (STP)Shielded Twisted-Pair (STP)

STP cables are similar to UTP cables, except there is a metal foil or braided-metal-mesh cover that encases each pair of insulated wires


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Categories of UTP CablesCategories of UTP Cables

EIA classifies UTP cables according to the quality:

Category 1 ― the lowest quality, only good for voice, mainly found in very old buildings, not recommended now

Category 2 ― good for voice and low data rates (up to 4Mbps for low-speed token ring networks)

Category 3 ― at least 3 twists per foot, for up to 10 Mbps (common in phone networks in residential buildings)

Category 4 ― up to 16 Mbps (mainly for token rings)

Category 5 (or 5e) ― up to 100 Mbps (common for networks targeted for high-speed data communications)

Category 6 ― more twists than Cat 5, up to 1 Gbps


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Coaxial CablesCoaxial Cables

In general, coaxial cables, or coax, carry signals of higher freq (100KHz–500MHz) than UTP cables

Outer metallic wrapping serves both as a shield against noise and as the second conductor that completes the circuit


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Coaxial CableCoaxial Cable

• Coaxial cable was used for many years with Ethernet bus networks

• In most networks today, twisted pair in a star configuration has replaced coaxial

• There are two types of coaxial cable, Thicknet (RG-58) and Thinnet(RG-8)

• Thicknet has less bend radius than Thinnet but a signal can travel further without disruption


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Fiber Optic CableFiber Optic Cable

• Fiber optic cable contains one or several pure glass tubes

• Light is sent through the glass using a light-emitting diode (LED)

• A layer of impure glass surrounds the tubes

• This is called cladding

• The cladding reflects the light back into the tube allowing the signal to travel for very long distances

• There are two types of fiber, single-modesingle-mode and multi-modemulti-mode


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two types of fibertwo types of fiberSingle-mode

• Cable using one narrow tube (10 microns in diameter)

• The light has very little room to reflect enabling it to travel long distances without requiring attenuators

Single mode is used to connect buildings

Multi-mode

• Cable is 50 to 100 microns in diameter

• Light reflects much more so the signal cannot travel as far and it may carry more than one signal

• Multi-mode is much cheaper than signal mode

• Multi-mode is usually used to connect wiring closets within a building

Fiber Optic Cable


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The connection is shared by a number of subscribers, hence may raise performance and security problems

Fiber-optic cable

Cable companyCoaxial Cable

TV

PC


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network sizeOne way to describe a network is by the area it spans

LAN – Local Area NetworkLAN – Local Area Network

• Computer network that spans a relatively small area

• Most are confined to a single building or group of buildings

• All the computers use the same datalink protocol

WAN – Wide Area NetworkWAN – Wide Area Network

• Group of connected LANs

• One LAN can be connected to other LANs over any distance via telephone lines, leased lines, fiber runs, or radio waves

• The Internet is the largest

MAN – Metropolitan Area NetworkMAN – Metropolitan Area Network

• A network within a city or town


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Ways of data exchange….Ways of data exchange….1- Simplex : information flows in only one direction

2- Half-duplex : information flows in two directions, but only in one direction at a time.

3- Full-duplex : information flows in two directions at the same time


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Communication vs. TransmissionCommunication vs. Transmission

Communication: meaning full exchange of information between two

communication media.

Transmission : is a physical movement of information like bit polarity,synchronisation and clock etc .

Transmission Technology available

Unicast

Multicast

Broadcast


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Host types :Host types :A network can also be described by the architecture the computers use to communicate with one another

Peer-to-Peer Model

• Each computer can share resources and get resources from another computer in the network

• Access is determined by user’s security permissions on each machine


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Host types :Host types :

Client/Server

• All computers get resources from the server

• Access is determined by the user’s security permissions on the network

Server

Client

Client

Can I use your printer?

Can I get the customer file?

Client

Can I add to the database?


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client/server networksclient/server networks• Advantages of client/server networks

• Facilitate resource sharing – centrally administrate and control

• Facilitate system backup and improve fault tolerance

• Enhance security – only administrator can have access to Server

• Support more users – difficult to achieve with peer-to-peer networks

• Disadvantages of client/server networks• High cost for Servers• Need expert to configure the network• Introduce a single point of failure to the system


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Establishing Network ConnectivityEstablishing Network Connectivity

Requires four stepsfour steps:

• Install the network interface card (NIC)

• Install the NIC driver

• Install the client software

• Install and configure the network communications protocol


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Establishing Network ConnectivityEstablishing Network Connectivity• Think of the operating system as speaking French and the network as

speaking Arabic

• Driver must speak both languages to allow them to communicate effectively

• Package and address the network packets ensuring that they are delivered within the LAN

• Protocol is determined by the NOS

• Windows and the Internet communicate using the TCP/IP protocolTCP/IP protocol

• Novell Netware uses IPX/SPXIPX/SPX and/or TCP/IPTCP/IP


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OSI ModelOSI ModelOSI (Open Systems Interconnect) model was created by the ISO (International Standards Organization)

• Sets the accepted procedures that govern the development of network components

• Procedures provide standard interfaces that allow diverse programs and hardware to interconnect

• Model addresses seven layers of network connectivity but a specific component may only address one or two of the layers

• A network interface card (NIC), for example, only works at the Physical and Data Link Layers

• The OSI model defines a consistent communication platform for manufacturers and developers of network components


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Layer interaction:Layer interaction:OSI 7-layer modelOSI 7-layer model

HostRouter Router Host

Application

Presentation

Session

Transport

Network

Link

Physical

Network

Link Link

Network

Link Link

Application

Presentation

Session

Transport

Network

Link

PhysicalPhysical

Hop by

hop

End to

end


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OSI ModelOSI Model


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OSI ModelOSI Model

Application 7

Presentation 6

Session 5

Transport 4

DataLink 2

Network 3

Physical 1 Physical 1

DataLink 2

Network 3

Transport 4

Session 5

Presentation 6

Application 7

Computer A Computer B

bits

Data

Data

Data

Chunked Data

Packet

Frame

Bits


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OSI ModelOSI ModelApplication Layer

Includes all the network applications a user interacts with including:

- HTTP – Hyper Text Transfer Protocol (www) is the protocol used on the world wide web and determines what types of information can be transferred.

- FTP – File Transfer Protocol is the protocol used to transfer files between computers

- SMTP – Simple Mail Transfer Protocol is used to send email.

- POP3 – Post Office Protocol 3 is used to receive mail.

- NNTP – Network News Transfer Protocol provides distribution, inquiry, retrieval and posting of news articles, bulleting boards and chats.

- Gopher – Gopher is a search engine (distributing documents over networks )

- Telnet – Telnet allows a user to logon and control a remote computer.


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OSI ModelOSI ModelPresentation Layer

Converts application layer information into a common format on the sending computer

Converts the common format to the application format at the receiving computer, formats include:

- ASCII – text files

- JPG, BMP, GIF – pictures

- MPG, AVI, MOV – videos

- MP3, WAV – music


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OSI ModelOSI ModelSession Layer

Responsible for establishing a connection, maintaining the connection and ending the connection

The decision to transmit data using half duplex or full duplex is made at this layer

- Half Duplex – This transmission type is similar to a one lane bridge. Cars can travel in both directions but not at the same time. With half duplex one computer send a message then waits for the other computer to respond.

- Full Duplex – This transmission type allows both computers to transmit and receive at the same time.


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OSI ModelOSI ModelTransport Layer

Responsible for breaking information into chunks and assigning addresses to the different processes

• The process addresses are called ports

• These should not be confused with external ports

• These are virtual ports used to keep network applications separated in the operating system

• Ports numbers are assigned based on the following:

- Well Known Ports 0-1023

- Registered Ports 1024 – 49,151

- Private Ports 49,151 – 65535


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OSI ModelOSI ModelTwo types of commonly used transport protocols that are part of the TCP/IP Protocol suite

- Transport Control Protocol (TCP) - At this layer the connection oriented protocol, TCP, establishes flow control by agreeing on the amount of data in each packet to be transferred (3 way handshake) and monitoring the packets that are received to ensure that lost packets are resent.

- User Datagram Protocol (UDP) – At this layer the connectionless protocol, UDP, sends a packet and assumes the destination computer receives it. There is no check performed to ensure the packet arrived intact.


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OSI ModelOSI ModelNetwork Layer

• At this layer a packet is created

• Packet includes information from the upper layers and the network address for the source and destination computer

• The IP address is the network address assigned to a TCP/IP packet

• The IPX address is the network address assigned to the IPX/SPX packet

• The information in the packet is ordered based on the network protocol

• A receiving computer will look for information in a specific place in the packet based on the protocol


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OSI ModelOSI ModelData-Link Layer

• Controls the movement of data on the network

• The packet from the network layer is modified to include the frame source and destination address

• This address is the media access control (MAC) address on the NIC

• Once these addresses are added the packet is called a frame

• Data-link protocols differ in the way frame is sent on the network


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ARP vs. RARP ARP vs. RARP Address Resolution Protocol (ARP)

• Is used to Associate the 32 bit IP address with the 48 bit physical address

• Used by a host or router to find the physical address of another host on its network by sending ARP query packet that includes the ip address of the reciever.

Reverse Address Resolution Protocol (RARP)• Allows hosts to discover its IP when it is know only its physical address.

IP: 111.111.111.001 IP: 111.111.111.002

MAC: AA-AA-AA-AA-AA-AA

111.111.111.002 BB-BB-BB-BB-BB-BB

ARP cache

LAN

MAC: BB-BB-BB-BB-BB-BB

111.111.111.001 AA-AA-AA-AA-AA-AA

ARP cache


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OSI ModelOSI ModelEthernet Protocol (IEEE 802.3) (Xerox and others)

• Based on the bus physical topology and uses Carrier Sense, Carrier Sense, Multiple Access with Collision Detection (CSMA/CD)Multiple Access with Collision Detection (CSMA/CD)

• Means the computer that wants to send a message listens on the media, sends the message if it hears nothing

• If two computers send a message at the same time, a collision occurs

• When a collision occurs the sending computers wait a random amount of time, listen, and resend the message


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OSI ModelOSI ModelToken Ring Protocol (IEEE 802.5) (IBM and others)

• Based on the ring physical topology and puts a token message on the ring

• The computer that wants to send a message must first control the token

• The message is sent, then the token is re-released

• This ensures that only one message is on the ring at a time


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OSI ModelOSI ModelWireless Protocol (IEEE 802.11x) (Similar to Ethernet)

• The computer listens for traffic on the radio waves, if there is none the package is transmitted

• If a collision occurs the package is retransmitted

• This protocol is affected by anything else transmitting in the same radio wave space

• Examples include cell phones and microwaves, common examples are 802.11b, 802.11g. and 802.11f

• They vary in transmission speed and frequency


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OSI ModelOSI ModelPhysical Layer

A frame is conveyed as bits onto the media

The physical topology and the components are the issues at this layer

Physical components include the media (cabling, radio waves, etc), the connectors, the NIC and the signal repeating devices like the hub and repeater


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Physical Components (Layer 1)Physical Components (Layer 1)Network Topologies

Physical vs. Logical Topology

1- Bus

• A bus topology is a single cable that connects all computers in a line

• Each end must be terminated, one must be grounded


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Physical Components (Layer 1)…..Physical Components (Layer 1)…..• Ring Topology

• Every computer serves asa repeater to boost signals

• Typical way to send data: • Token passing

• only the computer who

gets the token can send

data• Disadvantages

• Difficult to add computers

• More expensive

• If one computer fails, whole network fails

T T

T

data

T

data

T

data

T data

T data

T data

T Ack

T Ack

T Ack

TAck T


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Physical Components (Layer 1)…..Physical Components (Layer 1)…..3- Star

• In a star topologystar topology the computers are connected to a central HUB via cable segments


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How to construct a network with Bus / Star Topology?

Bus Topology

BNC T-Connector

Network Card

Coaxial cable

Star Topology


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Physical Components (Layer 1)Physical Components (Layer 1)4- Mesh

• Commonly used in WAN configurations

• Routers are connected to multiple links for redundancy

• Provides the ability to determine the quickest route to a destination and to change routes when a connection is broken


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Network ProtocolsNetwork ProtocolsTCP/IP

• Transport Control Protocol/Internet Protocol is the protocol used on the Internet and by Windows networked operating systems

• TCP/IP uses 32 bit IP addresses and subnet masks to identify the network and node

IPX/SPX

• Novell Netware uses this protocol that is easier to configure but both nodes must use the same frame type for communication to work

• The IPX address is based on the node MAC address


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Types of nodes important to networksTypes of nodes important to networksHub A device that repeats or broadcasts the network stream of information to individual nodes ( usually personal computers)

SwitchA device that receives packets from its input link, and then sorts them and transmits them over the proper link that connects to the node addressed.

BridgeA link between two networks that have identical rules of communication.

Gateway A link between two different networks that have different rules of communication.

Router A node that sends network packets in one of many possible directions to get

Brouter A hyprid devices that combine the features of both bridges and routers


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Objectives RevisitedObjectives RevisitedExplain the network concept

Explain how to connect to a network

Describe the OSI Model layers

Differentiate between Physical layer components


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Basics of NetworkingBasics of Networking

Thank You.

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CCNA Certified CCNA Certified

networks basics

Technology

twistedpair cables

twisted pair cable

twistedpair stp stp

types of twisted pair

categories of utp cables

pair of insulated wires

coaxial cable coaxial

types of coaxial cable