DITEC - Fundamentals in Networking (updated)

Diploma in Information Technology

Module IV: Fundamentals in Networking

Rasan SamarasingheESOFT Computer Studies (pvt) Ltd.No 68/1, Main Street, Pallegama, Embilipitiya.

Content1. What is a computer network?2. Types of computer networks3. Personal Area Network 4. Local Area Network 5. Metropolitan Area Network6. Wide Area Network 7. Networking Topologies8. Physical Topologies9. Physical Point to Point 10. Physical Bus Topology11. Physical Ring Topology12. Physical Star Topology13. Physical Mesh Topology14. Physical Tree Topology15. Physical Hybrid topology16. Logical Topologies17. Ethernet

18. Local Talk19. Token Ring20. FDDI21. ATM22. Transmission Media23. Networking Cables24. Coaxial Cables25. Twisted Pair Cables26. Fiber Optic Cables27. Network Devices28. NIC-Network interface card29. Hub30. Network Switch31. Router32. Bridge33. IP Address34. Activities

What is a computer network?

Computer network is an interconnection of two or more computers and other devices. Devices on a network can be linked by cables, telephone lines, radio waves or infrared waves.

Advantages of computer networks

• Files sharing• Devices sharing• Communication • Services sharing

Disadvantages of computer networks

• Virus attacks• Hacker attacks• Failures of a server may effect to the entire

network

Types of computer networks

Based on the network size, networks can be categorized into several types

1. Personal Area Network (PAN)2. Local Area Network (LAN)3. Metropolitan Area Network (MAN)4. Wide Area Network (WAN)

Personal Area Network (PAN)

• PAN is wireless network connected with mobile devices such as mobile phones, PDAs, Bluetooth printers, Headsets, etc.

• The technology using in here is Bluetooth or infrared.

Local Area Network (LAN)

• Coverage is about within 1km. • Ex: a company network within a building or

may be within two or more buildings.

Metropolitan Area Network (MAN)

• Coverage is about more than 1km and less than 10km.

• Ex: A network of a large town.

Wide Area Network (WAN)

• Coverage is about more than 10km.• Satellites may be use to expand this network.• Ex: Internet.

Networking Topologies

Topology is the way that we connect computers and other devices. In other words topology is the map of the network.

Networking Topologies

Topologies can be divided into two sections

1. Physical Topologies2. Logical Topologies

Physical Topologies

Physical arrangement of the network is known as physical topology

• Physical Point to Point Topology• Physical Bus Topology• Physical Ring Topology• Physical Star Topology• Physical Mesh Topology• Physical Tree Topology• Physical Hybrid Topology

Physical Point to Point Topology

This is the simplest topology that uses a permanent link between two end devices. It also known as peer to peer topology.

Characteristics• Using twisted pair cables.• Using RJ-45 connectors.• Maximum segment length is 100m.

Advantages• Low cost.• No additional devices or servers needed.• Easy to implement.

Disadvantages• Maximum 2 computers can be connected.• Cable breaks will affect to the whole network.

Physical Bus Topology

Each computers and devices are connected to a single cable called “backbone”.

Characteristics• Both thin net and thick net coaxial cables are

used.• Segment length of thin net coaxial cable is

200m.• Segment length of thick net coaxial cable is

500m.• BNC Connectors are used.• Maximum data transfer speed is 10mbps.

Advantages• Easy to implement.• Easy to expand.• Low cost (no additional devices).

Disadvantages• Maximum speed is 10mbps only.• Number of PCs will affect to the performance

of the network.• If backbone breaks, the entire network will be

failed.• Not suitable for heavy traffic.• Hard to find faults of the network.

Physical Ring Topology

Each computers and devices are connected each other forming a large circle.

Characteristics• Using coaxial or twisted pair cables.• Using BNC or RJ-45 connectors.• Maximum data transfer speed is between 4 -

16mbps.

Advantages• No need of a server.• Even the load of the network increases, it still

perform better than bus topology.

Disadvantages• If the cable breaks, entire network will be

failed.• If one station goes down, it will be affected to

the entire network.• Low speed.

Physical Star Topology

All the components of the network are connected to the central device called hub or switch.

Characteristics• Twisted pair cables are using.• Connectors are RJ-45.• Channel accessing method is depends on the

central device.

Advantages• Higher data transfer speed than previous

topologies. 100 - 1000mbps.• Central device make it easy to manage the

network.• Cable breaks will not affect to the entire

network.• Easy to expand.• More computers and devices can be connected.

Disadvantages• Single point of failure type network.• The central device using is increases the cost

of the network.

Extended Star Topology

Physical Mesh Topology

Each networking nodes are interconnected with each other.

Characteristics• It allowing most transmissions to be

distributed, even one of the connections goes down.

• Mesh topologies are either partially or fully connected.

• Uses in the internet.

Advantages• Supports for high traffic.• Cable breaks will not affect to the

communication.• Expansions and modifications can be done

without disrupting other devices.

Disadvantages• Overall cost of the network is high.• Setup, maintaining and administrating this

network is very tough.

Physical Tree Topology

A tree topology is essentially a combination of bus topology and star topology. The nodes of bus topology are replaced with star topology networks.

Advantages• Secondary nodes allow more devices to be

connected. • Having different levels of the network makes it

more manageable.

Disadvantages• Maintenance of the network is difficult.• If the backbone fails, the entire network will

be failed.

Physical Hybrid Topology

The combination of more topologies is known as hybrid topology.

Physical Hybrid Topology

Advantages• Flexible to expand and modify.• Very effective.

Disadvantages• Very complex.• Costly infrastructure.

Logical Topologies

Logical topology represents the way that data travel through the computer network.

• Ethernet• Local Talk• Token Ring• FDDI• ATM

Ethernet

• Ethernet is a local area network technology.• Physical Bus Topology and Physical Star Topology

(Hub as central device) uses Ethernet.• CSMA/CD (Carrier Sense Multiple Access / Collision

Detection) describes how the Ethernet protocol regulates communication among nodes.

• The number of devices and segment length of media affects the efficiency of Ethernet.

• Ethernet first standardized in 1983 as IEEE 802.3• 100Base-T and Gigabit Ethernet are the newest

versions of Ethernet.

Ethernet

• Physical Bus Topology is an Ethernet.

Ethernet

• Logical Bus Topology implemented as physical star topology is an Ethernet.

Ethernet

• By using segmentation the network diameter and the efficiency can be increased.

Local Talk

• Local Talk is a network protocol that was developed by Apple Computer, Inc. for Macintosh computers.

Local Talk

• The method used by Local Talk is called CSMA/CA (Carrier Sense Multiple Access / Collision Avoidance).

• Local Talk transmits data up to 230 kbps only.• Each Local Talk Mac or printer has its own

Local Talk adapter to connect each other as a chain.

• Two Mac computers can use a serial port instead of Local Talk adapters.

Local Talk uses CSMA/CA

Token Ring

• Token Ring also a local area network technology.

• Physical Ring Topology and Physical Star Topology (MSAU as central device) uses Token Ring.

• It uses a special three-byte frame called a token that travels around the ring.

• No collisions occurred.• It is standardized with protocol IEEE 802.5.

Token Ring

• Logical Ring Topology implemented as physical star topology is a Token Ring.

FDDI - Fiber Distributed Data Interface

• FDDI uses a dual ring physical topology for sending data over fiber optic cables.

• FDDI networks are token-passing networks, and support data rates of up to 100 Mbps.

• FDDI can extend in range up to 200 km.• FDDI uses two rings to achieve better results

and less chance of failure.• FDDI is used mainly in mission critical and high

traffic networks.

Dual-attach FDDI board

• If a station goes down, the signals are routed around it by a loop formed from the rings.

ATM - Asynchronous Transfer Mode

• ATM supports to carry a complete range of user traffic, including voice, data, and video signals.

• ATM transmitting relatively small and fixed data packets compared to units used with other technologies.

• The data transfer rates on ATM are either 155 Mbps or 622 Mbps.

• ATM is a key component of broadband ISDN.

Comparison of Logical TopologiesProtocol Cable Speed TopologyEthernet Twisted Pair,

Coaxial, Fiber10 Mbps Bus, Star, Tree

Fast Ethernet

Twisted Pair, Fiber

100 Mbps Star

Local Talk Twisted Pair 0.23 Mbps Bus or StarToken Ring Twisted Pair,

Coaxial4 Mbps - 16 Mbps

FDDI Fiber 100 Mbps Dual ringATM Twisted Pair,

Fiber155 - 622 Mbps

Bus, Star, Tree

Transmission Media

When choosing the transmission media consider the following

• Transmission speed• Segment length• Cost• Resistance to environment conditions

Networking Cables

There are several kind of networking cables

• Coaxial Cables• Twisted Pair Cables• Fiber Optic Cables

Coaxial Cables

Coaxial cables are two types• Thin net coaxial cables• Thick net coaxial cables

Outer cover

Outer copper shield

Inner insulatorInner inductor

Thin net coaxial cables

• Use to connect computers and devices in bus topology and ring topology.

• Well flexible.• Maximum segment length is 200m (185m).

Thick net coaxial cables

• Used as backbone cables and outdoor laying.• Not well flexible.• Maximum segment length is 500m (485m).

Coaxial cable connectors

BNC Connectors

Twister Pair Cables

• Most popular network cable in networking.• There are two types called:

1. Unshielded twisted pair cables.2. Shielded twisted pair cables.

• Maximum segment length is 100m.• Data transferring speed varied on cable

categories.

Unshielded Twister Pair Cables (UTP)

Shielded Twister Pair Cables (STP)

Twisted pair cable categories

Category Speed

CAT 1 Voice grade

CAT 2 4 Mbps

CAT 3 16Mbps

CAT 4 100Mbps

CAT 5 1000Mbps

CAT 5e 1000Mbps

CAT 6 1000Mbps

CAT 7 1000Mbps

Twisted pair cable connectors

RJ-45 Connectors RJ-45 Base

Twisted Pair / RJ-45 Cabling Types

Fiber Optic Cables

• Fiber optic cables uses light pulses to send and receive data.

• Have very higher data transfer speed. Ex: 10Gbps or 100Gbps.

• There are two types of fiber optic cables mainly– Single Mode Fiber (SMF)– Multi Mode Fiber (MMF)

Fiber Optic Cable Structure

Single Mode Fiber Optic Cables

• Transmit one light pulse at a time for one direction.

• Because of this reason devices need two cables for full duplex communication.

Multi Mode Fiber Optic Cables

• Transmit more than one light pulse.• Because of that full duplex communication can

achieve using a single cable.• These cables are not suitable for long distance

data transfer.

Submarine Cable Map

Fiber Optic Media Converters

Fiber Optic Connectors

Network Devices

Devices of a network can be classified as

• End user devicesProvide services to the user directly.

Computers, printers, scanners and other.

• Network devicesConnect end user devices together.

Network Devices

• NIC-Network interface card• Hub• Network Switch• Router• Bridge

Network Interface Card (NIC)

• Every computer should have a network interface card to connect to the network.

• There are several things to consider before buying a NIC.1. Network interface (connectors)2. Internal interface (PCI, USB)3. Network architecture

• Hub is use to connect all computers and other devices together.

• Hub is a broadcasting device.• Maximum data transfer speed is 10Mbps.• There are two types of hubs:

1. Active Hubs2. Passive Hubs

Active Hubs

When active hubs receive a signal in one port, it boost the signal and remove the electromagnetic noises before send that to other devices.

Passive Hubs

In passive hubs, it do not amplify the signal or remove noise before send data to other computers.

Network Switch

Switches are also use to connect computers in physical star topology and these devices are intelligent than hubs.

How network switch works?

1. Switches maintain a small table in there RAM to identify computers that related with the port numbers.

2. When switch receives a data packet, it reads the packet header to identify destination address.

3. After that it will search the entire table to find the related port for that address.

4. Then it can directly forward that data packet to the related computer rather than broadcasting.

Network Switch Types

• Layer 2 switches (unmanaged switches)Using MAC addresses of connected devices.

• Layer 3 switches (managed switches)Using IP addresses of connected devices.Providing more features than layer 2 switches and

expensive.

Routers

• Routers are use to connect networks together.• Routers are more intelligent devices and it use

IP addresses to deal with the packet.• Routers are responsible for:

Identify proper networks and sub networks.Forward data packets using the best path.Network Address Translation (NAT).Destroying TTL data packets. Etc

Bridge

Bridge can use to connect different topologies together or can use to connect different cable types together.

IP Address (Internet Protocol)

• IP address is an unique address that use to identify computers and devices.

• There are two IP versions called IPv4 and IPv6• IPv4 is the common version that used in most

networks.• IPv4 is made up with 4 decimal numbers and

each are separated by dots. (###.###.###.###) and each number can be in between 0 to 255.

• IP versions, rules and regulations are created and maintain by IANA (Internet Assigned Number Authority)

IP Classes (IPv4)

• Class A• Class B• Class C• Class D (reserved for multicasting purposes)• Class E (reserved for experimental purposes)

Can use in our networks

IP Address

IP Addresses are made up with two sections1. Network Address (network portion)2. Host Address (host portion)

N H H H N N H H N N N H

N N N H N N N H

Class A Class B Class C

Class D Class E

IP Ranges in each classes

IP ClassFirst Octate

IP AddressReceived Bits Range (min-max)

Class A 0####### 00000000-01111111(1-126) 1-126 0-255 0-255 0-255

Class B 10###### 10000000-10111111(128-191) 128-191 0-255 0-255 0-255

Class C 110##### 11000000-11011111(192-223) 192-223 0-255 0-255 0-255

Class D 1110#### 11100000-11101111(224-239) 224-239 0-255 0-255 0-255

Class E 1111#### 11110000-11111111(240-255) 240-255 0-255 0-255 0-255

Activities

Assigning IP address to connect two computers

User accountsSharing filesSharing printer

The End

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DITEC - Fundamentals in Networking (updated)

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