1. NETWORKING CONCEPTS

1.1 Learning objectives

To know about uses, applications, disadvantages of network

To elaborate various types of network

To elaborate various types of topologies

Discuss switching techniques

1.2 Definition

A computer network is defined as the interconnection of two or more computers. It is done to enable the computers to communicate and share available resources.

1.3 Applications

Sharing of resources such as printers

Sharing of expensive software's and database

Communication from one computer to another computer Exchange of data and information among users via network

Sharing of information over geographically wide areas.

1.4 Uses of computer networks

sharing information

sharing of hardware and software

Reduced cost

Improved security

Centralized software managements

Electronic mail

Flexible access

Increased speed

1.5 Components of computer networks

Two or more computers

Cables as links between the computers

A network interfacing card(NIC) on each computer

Switches

Software called operating system(OS)

1.6 Disadvantages of computer networks

High cost of installation

Requires time for administration

Failure of server

1.7 Types of Networks

1.7.1 LAN(Local Area Network)

LAN is a network which is designed to operate over a small physical area such as an office, factory or a group of buildings.

LAN’s are easy to design and troubleshoot

Exchange of information and sharing of resources becomes easy because of LAN. In LAN all machines are connected to a single cable. Different types of topologies such as star, tree, bus, ring, etc Can be used

It is usually a privately owned network.

1.7.2 MAN(Metropolitan Area Network)

It is in between LAN & WAN technology that covers the entire city.

It uses similar technology as LAN.

It can be a single network such as cable TV network, or a measure of connecting a number of

LAN’s o a large network so that resources can be shared LAN to LAN as well as device to

device.

1.7.3 WAN(Wide Area Network)

When network spans over a large distance or when the computers to be connected to each other are at widely separated locations a local area network cannot be used. A wide area network(WAN) is installed.

The communication between different users of WAN is established using leased telephone lines, satellite links and similar channels.

It is cheaper and more efficient to use the phone network for the link. Most WAN networks are used to transfer large blocks of data between its users.

1.8 Peer to Peer Network

In peer to peer network each computer is responsible for making its own resources available to other computers on the network.

Each computer is responsible for setting up and maintaining its own security for these resources.

Also each computer is responsible for accessing the required network resources from peer to peer relationships.

Peer to peer network is useful for a small network containing less than 10 computers on a single LAN .

In peer to peer network each computer can function as both client and server. Peer to peer networks do not have a central control system. There are no servers in peer

networks.

Peer networks are amplified into home group.

1.9 Client Server Network

In client-server network relationships, certain computers act as server and other act as clients. A server is simply a computer, that available the network resources and provides service to other computers when they request it. A client is the computer running a program that requests the service from a server.

Local area network(LAN) is based on client server network relationship. A client-server network is one n which all available network resources such as files,

directories, applications and shared devices, are centrally managed and hosted and then are accessed by client.

Client serve network are defined by the presence of servers on a network that provide security and administration of the network.

1.10 Topologoies

1.10.1BUS Topology

Bus topology is a network type in which every computer and network device is connected to

single cable. When it has exactly two endpoints, then it is called Linear Bus topology.

Features of Bus Topology

It transmits data only in one direction.

Every device is connected to a single cable

Advantages of Bus Topology

It is cost effective.

Cable required is least compared to other network topology.

Used in small networks.

It is easy to understand.

Easy to expand joining two cables together.

Disadvantages of Bus Topology

Cables fails then whole network fails.

If network traffic is heavy or nodes are more the performance of the network decreases.

Cable has a limited length.

It is slower than the ring topology.

1.10.2 RING Topology

It is called ring topology because it forms a ring as each computer is connected to another

computer, with the last one connected to the first. Exactly two neighbours for each device.

Features of Ring Topology

A number of repeaters are used for Ring topology with large number of nodes, because if

someone wants to send some data to the last node in the ring topology with 100 nodes, then

the data will have to pass through 99 nodes to reach the 100th node. Hence to prevent data

loss repeaters are used in the network.

The transmission is unidirectional, but it can be made bidirectional by having 2 connections

between each Network Node, it is called Dual Ring Topology.

In Dual Ring Topology, two ring networks are formed, and data flow is in opposite direction

in them. Also, if one ring fails, the second ring can act as a backup, to keep the network up.

Data is transferred in a sequential manner that is bit by bit. Data transmitted, has to pass

through each node of the network, till the destination node.

Advantages of Ring Topology

Transmitting network is not affected by high traffic or by adding more nodes, as only the

nodes having tokens can transmit data.

Cheap to install and expand

Disadvantages of Ring Topology

Troubleshooting is difficult in ring topology.

Adding or deleting the computers disturbs the network activity.

Failure of one computer disturbs the whole network.

1.10.3 STAR Topology

In this type of topology all the computers are connected to a single hub through a cable. This hub

is the central node and all others nodes are connected to the central node.

Features of Star Topology

Every node has its own dedicated connection to the hub.

Hub acts as a repeater for data flow.

Can be used with twisted pair, Optical Fibre or coaxial cable.

Advantages of Star Topology

Fast performance with few nodes and low network traffic.

Hub can be upgraded easily.

Easy to troubleshoot.

Easy to setup and modify.

Only that node is affected which has failed, rest of the nodes can work smoothly.

Disadvantages of Star Topology

Cost of installation is high.

Expensive to use.

If the hub fails then the whole network is stopped because all the nodes depend on the hub.

Performance is based on the hub that is it depends on its capacity

1.10.4 MESH Topology

It is a point-to-point connection to other nodes or devices. All the network nodes are connected

to each other. Mesh has n(n-1)/2 physical channels to link n devices.

Types of Mesh Topology

1. Partial Mesh Topology : In this topology some of the systems are connected in the same

fashion as mesh topology but some devices are only connected to two or three devices.

2. Full Mesh Topology : Each and every nodes or devices are connected to each other.

Features of Mesh Topology

Fully connected.

Robust.

Not flexible.

Advantages of Mesh Topology

Each connection can carry its own data load.

It is robust.

Fault is diagnosed easily.

Provides security and privacy.

Disadvantages of Mesh Topology

Installation and configuration is difficult.

Cabling cost is more.

Bulk wiring is required.

1.10.5 TREE Topology

It has a root node and all other nodes are connected to it forming a hierarchy. It is also called

hierarchical topology. It should at least have three levels to the hierarchy.

Features of Tree Topology

Ideal if workstations are located in groups.

Used in Wide Area Network.

Advantages of Tree Topology

Extension of bus and star topologies.

Expansion of nodes is possible and easy.

Easily managed and maintained.

Error detection is easily done.

Disadvantages of Tree Topology

Heavily cabled.

Costly.

If more nodes are added maintenance is difficult.

Central hub fails, network fails.

1.10.6 HYBRID Topology

It is two different types of topologies which is a mixture of two or more topologies. For example

if in an office in one department ring topology is used and in another star topology is used,

connecting these topologies will result in Hybrid Topology (ring topology and star topology).

Features of Hybrid Topology

It is a combination of two or topologies

Inherits the advantages and disadvantages of the topologies included

Advantages of Hybrid Topology

Reliable as Error detecting and trouble shooting is easy.

Effective.

Scalable as size can be increased easily.

Flexible.

Disadvantages of Hybrid Topology

Complex in design.

Costly.

1.11 Switching Techniques

1.11.1 Circuit switching: it is a technique that directly connects the sender and the receiver in

an unbroken path.

• Telephone switching equipment, for example, establishes a path that connects the caller's

telephone to the receiver's telephone by making a physical connection.

• With this type of switching technique, once a connection is established, a dedicated path

exists between both ends until the connection is terminated.

• Routing decisions must be made when the circuit is first established, but there are no decisions

made after that time

• Circuit switching in a network operates almost the same way as the telephone system works.

• A complete end-to-end path must exist before communication can take place.

• The computer initiating the data transfer must ask for a connection to the destination.

• Once the connection has been initiated and completed to the destination device, the destination

device must acknowledge that it is ready and willing to carry on a transfer.

Advantages:

• The communication channel (once established) is dedicated.

Disadvantages:

• Possible long wait to establish a connection, (10 seconds, more on long- distance or

international calls.) during which no data can be transmitted.

• More expensive than any other switching techniques, because a dedicated path is required for

each connection.

• Inefficient use of the communication channel, because the channel is not used when the

connected systems are not using it.

1.11.2 Packet Switching:

Packet Switching

• Packet switching can be seen as a solution that tries to combine the advantages of message and

circuit switching and to minimize the disadvantages of both.

• There are two methods of packet switching: Datagram and virtual circuit.

• In both packet switching methods, a message is broken into small parts, called packets.

• Each packet is tagged with appropriate source and destination addresses.

• With current technology, packets are generally accepted onto the network on a first-come, first-

served basis. If the network becomes overloaded, packets are delayed or discarded (``dropped'').

• In packet switching, the analog signal from your phone is converted into a digital data stream.

That series of digital bits is then divided into relatively tiny clusters of bits, called packets.

• Datagram packet switching is similar to message switching in that each packet is a self-

contained unit with complete addressing information attached.

• This fact allows packets to take a variety of possible paths through the network.

• So the packets, each with the same destination address, do not follow the same route, and they

may arrive out of sequence at the exit point node (or the destination).

• Reordering is done at the destination point based on the sequence number of the packets.

• It is possible for a packet to be destroyed if one of the nodes on its way is crashed momentarily.

Thus all its queued packets may be lost.

• In the virtual circuit approach, a preplanned route is established before any data packets are

sent.

• A logical connection is established when a sender send a "call request packet" to the receiver

and the receiver send back an acknowledge packet "call accepted packet" to the sender if the

receiver agrees on conversational parameters.

• The conversational parameters can be maximum packet sizes, path to be taken, and other

variables necessary to establish and maintain the conversation.

• Virtual circuits imply acknowledgements, flow control, and error control, so virtual circuits are reliable. That is, they have the capability to inform upper-protocol layers if a transmission

problem occurs

• In virtual circuit, the route between stations does not mean that this is a dedicated path, as in circuit switching.

• A packet is still buffered at each node and queued for output over a line.

Advantages:

• Packet switching is cost effective, because switching devices do not need massive amount of secondary storage.

• Packet switching offers improved delay characteristics, because there are no long messages in

the queue (maximum packet size is fixed).

• Packet can be rerouted if there is any problem, such as, busy or disabled links.

•The advantage of packet switching is that many network users can share the same channel at the

same time. Packet switching can maximize link efficiency by making optimal use of link

bandwidth.

Disadvantages:

• Protocols for packet switching are typically more complex.

• It can add some initial costs in implementation.

• If packet is lost, sender needs to retransmit the data. Another disadvantage is that packet-switched systems still can’t deliver the same quality as dedicated circuits in applications

requiring very little delay - like voice conversations or moving images.

1.11.3 Message Switching

• With message switching there is no need to establish a dedicated path between two stations.

• When a station sends a message, the destination address is appended to the message.

• The message is then transmitted through the network, in its entirety, from node to node.

• Each node receives the entire message, stores it in its entirety on disk, and then transmits the message to the next node.

• This type of network is called a store-and-forward network.

A message-switching node is typically a general-purpose computer. The device needs sufficient

secondary-storage capacity to store the incoming messages, which could be long. A time delay is

introduced using this type of scheme due to store- and-forward time, plus the time required to

find the next node in the transmission path.

Advantages:

• Channel efficiency can be greater compared to circuit-switched systems, because more

devices are sharing the channel.

• Traffic congestion can be reduced, because messages may be temporarily stored in route.

• Message priorities can be established due to store-and-forward technique.

• Message broadcasting can be achieved with the use of broadcast address appended in the

message

Disadvantages

• Message switching is not compatible with interactive applications.

• Store-and-forward devices are expensive, because they must have large disks to hold

potentially long messages

VERY SHORT QUESTIONS

1. Define network?

2. What is full form of LAN?

3. Define star topology?

4. What is a server?

5. Name various elements of computer network?

6. What are the 3 phases of circuit switching?

7. Name four network topology?

SHORT QUESTIONS

1. Explain packet switching?

2. What is message switching?

3. Explain tree and star topology?

4. Discuss mesh topology?

5. What are the uses of computer network?

6. What is peer to peer network?

7. What is Ring topology?

8. What do you mean by email?

LONG QUESTIONS

1. Explain various topologies in detail?

2. Explain switching techniques?

3. What is peer to peer and client server model?

4. What is computer network and what are its applications?

2. NETWORKING MODELS

2.1 Learning objectives

2.2 OSI model

Established in 1947, the International Standards Organization(ISO) is a multinational body

dedicated to world wide agreement on international standards .An ISO standard that covers all

aspects of network communications is the Open Systems Interconnection model. It was first

introduced in the late 1970s .An open system is a set of protocols that all owes any two different

system to communicate regardless of the underlying architecture. The purpose of the OSI mode

list show how to facilitate communication between different systems without requiring changes

to the logic of the underlying hardware and software

Layer 7: Physical Layer

The lowest layer of the OSI model is concerned with data communication in the form of

electrical, optic, or electromagnetic signals physically transmitting information between

networking devices and infrastructure. The Physical Layer is essentially responsible for the

communication of unstructured raw data streams over a physical medium. It defines a range of

aspects associated with the electrical, mechanical, and physical systems and networking devices

that include the specifications; e.g. cable size, signal frequency, voltages, etc.; topologies such as

Bus, Star, Ring, and Mesh; communication modes such as Simplex, Half Duplex, and Full

Duplex; data Transmission Performance e.g. Bit Rate and Bit Synchronization; as well as

modulation, switching, and interfacing with the physical transmission medium as described here.

Common protocols include Wi-Fi, Ethernet, and others as listed here. The hardware includes

networking devices, antennas, cables, modem, intermediate devices such as repeaters and hubs.

Layer 6: Data Link Layer

The second layer of the OSI model concerns data transmission between the nodes within a

network and manages the connections between physically connected devices such as switches.

The raw data received from the physical layer is synchronized and packaged into

data frames that contain the necessary protocols to route information between appropriate nodes.

The Data Link Layeris further divided into two sublayers: Logical Link Control (LLC) sublayer

responsible for flow controls and error controls that ensure error-free and accurate data

transmission between the network nodes; and the Media Access Control (MAC) sublayer

responsible for managing access and permissions to transmit data between the network nodes.

The data is transmitted sequentially and the layer expects acknowledgement for the encapsulated

raw data sent between the nodes.

Layer 5: Network Layer

The third layer of the OSI model organizes and transmits data between multiple networks. This

layer is responsible for routing the data via the best physical path based on a range of factors

including network characteristics, best available path, traffic controls, congestion of data packets,

and priority of service, among others. The network layer implements logical addressing for data

packets to distinguish between the source and destination networks. Other functions at the

Network Layer include encapsulation and fragmentation, as well as congestion controls and error

handling. The outgoing data is divided into packets and incoming data is reassembled into

information that is consumable at a higher application level. Network Layer hardware includes

routes, bridge routers, 3-layer switches, and protocols such as Internet (IPv4) Protocol version 4

and Internet Protocol version 6 (IPv6).

Layer 4: Transport Layer

The fourth layer of the OSI model ensures complete and reliable delivery of data packets.

The Transport Layer provides mechanisms such as error control, flow control, and congestion

control to keep track of the data packets, check for errors and duplication, and resend the

information that fails delivery. It involves the service-point addressing function to ensure that the

packet is sent in response to a specific process (via a port address). Packet Segmentation and

reassembly ensure that the data is divided and sequentially sent to the destination where it is

rechecked for integrity and accuracy based on the receiving sequence. Common protocols

include the Transmission Control Protocol (TCP) for connection-oriented data transmission

and User Datagram Protocol (UDP) for connectionless data transmission.

Layer 3: Session Layer

The Session Layer manages sessions between servers to coordinate the communication – as the

first of the top three OSI model layers that deal with the software level. Session refers to any

interactive data exchange between two entities within a network. Common examples include

HTTPS sessions that allow Internet users to visit and browse websites for a specific time period.

The Session Layer is responsible for a range of functions including opening, closing, and re-

establishing session activities, authentication and authorization of communication between

specific apps and servers, identifying full-duplex or half-duplex operations, and synchronizing

data streams. Common Session Layer protocols include Remote procedure call protocol (RPC),

Point-to-Point Tunneling Protocol (PPTP), Session Control Protocol (SCP), and Session

Description Protocol (SDP) as described here.

Layer 2: Presentation Layer

The sixth layer of the OSI model converts data formats between applications and the networks.

Responsibilities of the Presentation Layer include data conversion, character code

translation, data compression, encryption and decryption. The Presentation Layer, also called the

Syntax Layer, maps the semantics and syntax of the data such that the received information is

consumable for every distinct network entity. For example, the data we transfer from our

encryption-based communication app is formatted and encrypted at this layer before it is sent

across the network. At the receiving end, the data is decrypted and formatted into text or media

information as originally intended. The presentation layer also serializes complex information

into transportable formats. The data streams are then deserialized and reassembled into original

object format at the destination.

Layer 1: Application Layer

The Application Layer concerns the networking processes at the application level. This layer

interacts directly with end-users to provide support for email, network data sharing, file transfers,

and directory services, among other distributed information services. The upper most layer of the

OSI model identifies networking entities to facilitate networking requests by end-user requests,

determines resource availability, synchronizes communication, and manages application-specific

networking requirements. The Application Layer also identifies constraints at the application

level such as those associated with authentication, privacy, quality of service, networking

devices, and data syntax. The most common Application Layer protocols include File Transfer

Protocol (FTP), Simple Mail Transfer Protocol (SMTP) and Domain Name System (DNS).

2.2 TCP/IP

Layer 4: Application layer

is the top most layer of four layer TCP/IP model. Application layer is present on the top of

the Transport layer. Application layer defines TCP/IP application protocols and how host

programs interface with Transport layer services to use the network.

Application layer includes all the higher-level protocols like DNS (Domain Naming

System), HTTP (Hypertext Transfer Protocol), Telnet, SSH, FTP (File Transfer Protocol), TFTP

(Trivial File Transfer Protocol), SNMP (Simple Network Management Protocol), SMTP (Simple

Mail Transfer Protocol) , DHCP (Dynamic Host Configuration Protocol), X Windows, RDP

(Remote Desktop Protocol) etc.

Layer 3: Transport Layer

Transport Layer is the third layer of the four layer TCP/IP model. The position of the Transport

layer is between Application layer and Internet layer. The purpose of Transport layer is to permit

devices on the source and destination hosts to carry on a conversation. Transport layer defines

the level of service and status of the connection used when transporting data.

The main protocols included at Transport layer are TCP (Transmission Control

Protocol) and UDP (User Datagram Protocol).

Layer 2: Internet Layer

Internet Layer is the second layer of the four layer TCP/IP model. The position of Internet

layer is between Network Access Layer and Transport layer. Internet layer pack data into data

packets known as IP datagrams, which contain source and destination address (logical address or

IP address) information that is used to forward the datagrams between hosts and across networks.

The Internet layer is also responsible for routing of IP datagrams.

Packet switching network depends upon a connectionless internetwork layer. This layer is known

as Internet layer. Its job is to allow hosts to insert packets into any network and have them to

deliver independently to the destination. At the destination side data packets may appear in a

different order than they were sent. It is the job of the higher layers to rearrange them in order to

deliver them to proper network applications operating at the Application layer.

The main protocols included at Internet layer are IP (Internet Protocol), ICMP (Internet Control

Message Protocol), ARP (Address Resolution Protocol), RARP (Reverse Address Resolution

Protocol) and IGMP (Internet Group Management Protocol).

Layer 1: Network Access Layer

Network Access Layer is the first layer of the four layer TCP/IP model. Network Access

Layer defines details of how data is physically sent through the network, including how bits are

electrically or optically signaled by hardware devices that interface directly with a network

medium, such as coaxial cable, optical fiber, or twisted pair copper wire.

The protocols included in Network Access Layer are Ethernet, Token Ring, FDDI, X.25, Frame

Relay etc.

2.4 Comparison between OSI and TCP/IP model

SI(Open System Interconnection) TCP/IP(Transmission Control Protocol / Inter

1. OSI is a generic, protocol independent

standard, acting as a communication gateway

between the network and end user.

1. TCP/IP model is based on standard protocols a

the Internet has developed. It is a communica

which allows connection of hosts over a netwo

2. In OSI model the transport layer guarantees 2. In TCP/IP model the transport layer does not

the delivery of packets. delivery of packets. Still the TCP/IP model is more reliable.

3. Follows vertical approach. 3. Follows horizontal approach.

4. OSI model has a separate Presentation layer

and Session layer.

4. TCP/IP does not have a separate Presentation layer or

Session layer.

5. Transport Layer is Connection Oriented. 5. Transport Layer is both Connection Oriented and

Connection less.

6. Network Layer is both Connection Oriented

and Connection less.

6. Network Layer is Connection less.

7. OSI is a reference model around which the

networks are built. Generally it is used as a

guidance tool.

7. TCP/IP model is, in a way implementation of the OSI

model.

8. Network layer of OSI model provides both

connection oriented and connectionless service.

8. The Network layer in TCP/IP model provides

connectionless service.

9. OSI model has a problem of fitting the

protocols into the model.

9. TCP/IP model does not fit any protocol

10. Protocols are hidden in OSI model and are

easily replaced as the technology changes.

10. In TCP/IP replacing protocol is not easy.

11. OSI model defines services, interfaces and

protocols very clearly and makes clear

distinction between them. It is protocol

independent.

11. In TCP/IP, services, interfaces and protocols are not

clearly separated. It is also protocol dependent.

12. It has 7 layers 12. It has 4 layers

VERY SHORT QUESTIONS

1. What is the full form of OSI?

2. Name the seven layers of OSI model?

3. Name the four layers of TCP model?

4. Draw the diagram of OSI model?

5. Which layer consist of data in form of packets?

6. Name the two protocols used in Transport layer?

SHORT QUESTIONS

1. what is the function of data link layer?

2. what is the function of presentation and session layer?

3. what is OSI reference model?

4. Write the function of transport layer of TCP model?

5. Write the function of application layer of OSI model?

LONG QUESTIONS

1. What is an OSI model? Explain in detail.

2. What is TCP/IP model? Explain in detail.

3. TCP/IP ADDRESSING

3.1 Learning Objectives

To know about IP addressing

Elaborate classful and classless addressing

Discuss subnetting and supernetting

Know about IPV4 and IPV6 header formats

Elaborate comparison between them

3.2 IP Addressing

IP address is an address having information about how to reach a specific host, especially outside

the LAN. An IP address is a 32 bit unique address having an address space of 232

.

Generally, there are two notations in which IP address is written, dotted decimal notation and

hexadecimal notation.

Dotted Decimal Notation

Hexadecimal Notation

Some points to be noted about dotted decimal notation :

1. The value of any segment (byte) is between 0 and 255 (both included).

2. There are no zeroes preceding the value in any segment (054 is wrong, 54 is correct).

3.2.1 Classful Addressing

The 32 bit IP address is divided into five sub-classes. These are:

Class A

Class B

Class C

Class D

Class E

Each of these classes has a valid range of IP addresses. Classes D and E are reserved for

multicast and experimental purposes respectively. The order of bits in the first octet determine

the classes of IP address.

IPv4 address is divided into two parts:

Network ID

Host ID

The class of IP address is used to determine the bits used for network ID and host ID and the

number of total networks and hosts possible in that particular class. Each ISP or network

administrator assigns IP address to each device that is connected to its network.

Note: IP addresses are globally managed by Internet Assigned Numbers Authority(IANA) and

regional Internet registries(RIR).

Note: While finding the total number of host IP addresses, 2 IP addresses are not counted and are

therefore, decreased from the total count because the first IP address of any network is the

network number and whereas the last IP address is reserved for broadcast IP.

Class A:

IP address belonging to class A are assigned to the networks that contain a large number of hosts.

The network ID is 8 bits long.

The host ID is 24 bits long.

The higher order bit of the first octet in class A is always set to 0. The remaining 7 bits in first

octet are used to determine network ID. The 24 bits of host ID are used to determine the host in

any network. The default sub-net mask for class A is 255.x.x.x. Therefore, class A has a total of:

2^7= 128 network ID

2^24 – 2 = 16,777,214 host ID

IP addresses belonging to class A ranges from 1.x.x.x – 126.x.x.x

Class B:

IP address belonging to class B are assigned to the networks that ranges from medium-sized to

large-sized networks.

The network ID is 16 bits long.

The host ID is 16 bits long.

The higher order bits of the first octet of IP addresses of class B are always set to 10. The

remaining 14 bits are used to determine network ID. The 16 bits of host ID is used to determine

the host in any network. The default sub-net mask for class B is 255.255.x.x. Class B has a total

of:

2^14 = 16384 network address

2^16 – 2 = 65534 host address

IP addresses belonging to class B ranges from 128.0.x.x – 191.255.x.x.

Class C:

IP address belonging to class C are assigned to small-sized networks.

The network ID is 24 bits long.

The host ID is 8 bits long.

The higher order bits of the first octet of IP addresses of class C are always set to 110. The

remaining 21 bits are used to determine network ID. The 8 bits of host ID is used to determine

the host in any network. The default sub-net mask for class C is 255.255.255.x. Class C has a

total of:

2^21 = 2097152 network address

2^8 – 2 = 254 host address

IP addresses belonging to class C ranges from 192.0.0.x – 223.255.255.x.

Class D:

IP address belonging to class D are reserved for multi-casting. The higher order bits of the first

octet of IP addresses belonging to class D are always set to 1110. The remaining bits are for the

address that interested hosts recognize.

Class D does not posses any sub-net mask. IP addresses belonging to class D ranges from

224.0.0.0 – 239.255.255.255.

Class E:

IP addresses belonging to class E are reserved for experimental and research purposes. IP

addresses of class E ranges from 240.0.0.0 – 255.255.255.254. This class doesn’t have any sub-

net mask. The higher order bits of first octet of class E are always set to 1111.

Range of special IP addresses:

169.254.0.0 – 169.254.0.16 : Link local addresses

127.0.0.0 – 127.0.0.8 : Loop-back addresses

0.0.0.0 – 0.0.0.8 : used to communicate within the current network.

Summary of Classful addressing :

Problems with Classful Addressing:

The problem with this classful addressing method is that millions of class A address are wasted,

many of the class B address are wasted, whereas, number of addresses available in class C is so

small that it cannot cater the needs of organizations. Class D addresses are used for multicast

routing, and are therefore available as a single block only. Class E addresses are reserved.

Since there are these problems, Classful networking was replaced by Classless Inter-Domain

Routing (CIDR) in 1993

3.2.3 Classless Addressing

To reduce the wastage of IP addresses in a block, we use sub-netting. What we do is that we use

host id bits as net id bits of a classful IP address. We give the IP address and define the number

of bits for mask along with it (usually followed by a ‘/’ symbol), like, 192.168.1.1/28. Here,

subnet mask is found by putting the given number of bits out of 32 as 1, like, in the given

address, we need to put 28 out of 32 bits as 1 and the rest as 0, and so, the subnet mask would be

255.255.255.240.

3.3. Subnetting

Subnetting: Dividing a large block of addresses into several contiguous sub-blocks and

assigning these sub-blocks to different smaller networks is called subnetting. It is a practice that

is widely used when classless addressing is done.

3.4 Supernetting

Supernetting is the opposite of Subnetting. In subnetting, a single big network is divided into

multiple smaller subnetworks. In Supernetting, multiple networks are combined into a bigger

network termed as a Supernetwork or Supernet.

Supernetting is mainly used in Route Summarization, where routes to multiple networks with

similar network prefixes are combined into a single routing entry, with the routing entry pointing

to a Super network, encompassing all the networks. This in turn significantly reduces the size of

routing tables and also the size of routing updates exchanged by routing protocols.

More specifically,

When multiple networks are combined to form a bigger network, it is termed as super-

netting

Super netting is used in route aggregation to reduce the size of routing tables and routing

table updates

3.5 IPV4 Header Format

Base Header

Version: It defines the version number of IP, i.e., in this case, it is 4 with a binary value of 0100.

Header length (HLEN): It represents the length of the header in multiple of four bytes.

Service type: It determines how datagram should be handled and includes individual bits such as

level of throughput, reliability, and delay.

Total length: It signifies the entire length of the IP datagram.

Identification: This field is used in fragmentation. A datagram is divided when it passes through

different networks to match the network frame size. At that time each fragment is determined

with a sequence number in this field.

Flags: The bits in the flags field handles fragmentation and identifies the first, middle or last

fragment, etc.

Fragmentation offset: It’s a pointer that represents the offset of the data in the original datagram.

Time to live: It defines the number of hops a datagram can travel before it is rejected. In simple

words, it specifies the duration for which a datagram remains on the internet.

Protocol: The protocol field specifies which upper layer protocol data are encapsulated in the

datagram (TCP, UDP, ICMP, etc.).

Header checksum: This is a 16-bit field confirm the integrity of the header values, not the rest of

the packet.

Source address: It’s a four-byte internet address which identifies the source of the datagram.

Destination address: This is a 4-byte field which identifies the final destination.

Options: This provides more functionality to the IP datagram. Furthermore can carry fields like

control routing, timing, management, and alignment.

IPv4 is a two-level address structure (net id and host id) classified into five categories (A, B, C,

D, and E).

3.6 IPV6 Header Format

An IPv6 address is a 128-bit binary value, which can be displayed as 32 hexadecimal digits.

Base Header

Version: This four-bit field specifies the version of the IP, i.e., 6 in this case.

Priority: It defines the priority of the packet concerning traffic congestion.

Flow label: The reason for designing this protocol is to facilitate with special controlling for a

certain flow of data.

Payload length: It defines the total length of the IP datagram excepting the base header.

Next header: It’s an eight-bit field describe the header that trails the base header in the datagram.

The next header is one of the optional extension headers which IP uses or the header for an upper

layer protocol such as UDP or TCP.

Hop limit: This eight-bit hop limit field assists with the same functions at the TTL field in IPv4.

Source address: It is a 16 bytes internet address identifies the source of the datagram.

Destination address: This is 16-byte internet address that generally describes the final destination

of the datagram.

3.7 Comparison Between IPV4 and IPV6

BASIS OF

COMPARISON

IPV4 IPV6

Address Configuration Supports Manual and DHCP

configuration.

Supports Auto-configuration and

renumbering

End-to-end connection

integrity

Unachievable Achievable

Address Space It can generate 4.29 x

109 addresses.

It can produce quite a large numb

addresses, i.e., 3.4 x 1038

.

Security features Security is dependent on

application

IPSEC is inbuilt in the IPv6 protocol

Address length 32 bits (4 bytes) 128 bits (16 bytes)

Address Representation In decimal In hexadecimal

Fragmentation performed

by

Sender and forwarding routers Only by the sender

Packet flow identification Not available Available and uses flow label field in the

header

Checksum Field

Available Not available

Message Transmission

Scheme

Broadcasting Multicasting and Anycasting

Encryption and

Authentication

Not Provided Provided

VERY SHORT QUESTIONS

1. Define IP address.

2. Masking is used in subnetting(T/F)?

3. Name the five class of classfull addressing?

4. Mention the range of addresses included in each class of IP address?

5. What is the full form of IPV4 and IPV6?

6. Which address is used for loop back test?

7. What is TCP/IP

SHORT QUESTIONS

1. Explain the various types of ip address?

2. What is subnetting?

3. What is supernetting?

4. Draw the table for various address class of IP address?

5. What is the disadvantage of classful addressing and why classless addressing was opted?

LONG QUESTION

1. Explain IPV4 Header format?

2. Explain IPV6 header format?

3. Compare IPV4 and IPV6 header format?

4. Explain IP addressing in detail?

4. NETWORK ARCHITECTURE

4.1 Learning Objectives

4.2 Ethernet

Ethernet

Ethernet is the most popular physical layer LAN technology in use today. It defines the number

of conductors that are required for a connection, the performance thresholds that can be

expected, and provides the framework for data transmission. A standard Ethernet network can

transmit data at a rate up to 10 Megabits per second (10 Mbps). Other LAN types include Token

Ring, Fast Ethernet, Gigabit Ethernet, 10 Gigabit Ethernet, Fiber Distributed Data Interface

(FDDI), Asynchronous Transfer Mode (ATM) and LocalTalk.

Ethernet is popular because it strikes a good balance between speed, cost and ease of installation.

These benefits, combined with wide acceptance in the computer marketplace and the ability to

support virtually all popular network protocols, make Ethernet an ideal networking technology

for most computer users today.

The Institute for Electrical and Electronic Engineers developed an Ethernet standard known as

IEEE Standard 802.3. This standard defines rules for configuring an Ethernet network and also

specifies how the elements in an Ethernet network interact with one another. By adhering to the

IEEE standard, network equipment and network protocols can communicate efficiently.

4.3 Ethernet Specification and Standardisation

4.3.1 Fast Ethernet

The Fast Ethernet standard (IEEE 802.3u) has been established for Ethernet networks that need

higher transmission speeds. This standard raises the Ethernet speed limit from 10 Mbps to 100

Mbps with only minimal changes to the existing cable structure. Fast Ethernet provides faster

throughput for video, multimedia, graphics, Internet surfing and stronger error detection and

correction.

There are three types of Fast Ethernet: 100BASE-TX for use with level 5 UTP cable; 100BASE-

FX for use with fiber-optic cable; and 100BASE-T4 which utilizes an extra two wires for use

with level 3 UTP cable. The 100BASE-TX standard has become the most popular due to its

close compatibility with the 10BASE-T Ethernet standard.

Network managers who want to incorporate Fast Ethernet into an existing configuration are

required to make many decisions. The number of users in each site on the network that need the

higher throughput must be determined; which segments of the backbone need to be reconfigured

specifically for 100BASE-T; plus what hardware is necessary in order to connect the 100BASE-

T segments with existing 10BASE-T segments. Gigabit Ethernet is a future technology that

promises a migration path beyond Fast Ethernet so the next generation of networks will support

even higher data transfer speeds.

4.3.2 Gigabit Ethernet

Gigabit Ethernet was developed to meet the need for faster communication networks with

applications such as multimedia and Voice over IP (VoIP). Also known as “gigabit-Ethernet-

over-copper” or 1000Base-T, GigE is a version of Ethernet that runs at speeds 10 times faster

than 100Base-T. It is defined in the IEEE 802.3 standard and is currently used as an enterprise

backbone. Existing Ethernet LANs with 10 and 100 Mbps cards can feed into a Gigabit Ethernet

backbone to interconnect high performance switches, routers and servers.

From the data link layer of the OSI model upward, the look and implementation of Gigabit

Ethernet is identical to that of Ethernet. The most important differences between Gigabit

Ethernet and Fast Ethernet include the additional support of full duplex operation in the MAC

layer and the data rates.

VERY SHORT QUESTIONS

1. What is Ethernet?

2. What are ethernet specifications?

3. What is the full form of IEEE?

4. Which cables are used in gigabit Ethernet?

5. Give examples of fast Ethernet?

SHORT QUESTIONS

1. What is fast Ethernet?

2. What is gigabit Ethernet?

LONG QUESTIONS

1. Explain different ethernet specifications and standards?

5. Network Connectivity

5.1 Learning Objectives

To know about various network connectivity devices like hub, switches, bridges, router,

gateways, NICs

5.2 Network Connectivity devices

5.2.1 Hub

Hub is one of the basic icons of networking devices which works at physical layer and hence

connect networking devices physically together. Hubs are fundamentally used in networks that

use twisted pair cabling to connect devices. They are designed to transmit the packets to the

other appended devices without altering any of the transmitted packets received. They act as

pathways to direct electrical signals to travel along. They transmit the information regardless of

the fact if data packet is destined for the device connected or not.

Hub falls in two categories:

Active Hub: They are smarter than the passive hubs. They not only provide the path for the data

signals infact they regenerate, concentrate and strengthen the signals before sending them to their

destinations. Active hubs are also termed as ‘repeaters’.

Passive Hub: They are more like point contact for the wires to built in the physical network.

They have nothing to do with modifying the signals.

5.2.2. Switches

Switches are the linkage points of an Ethernet network. Just as in hub, devices in switches are

connected to them through twisted pair cabling. But the difference shows up in the manner both

the devices; hub and a switch treat the data they receive. Hubworks by sending the data to all the

ports on the device whereas a switch transfers it only to that port which is connected to the

destination device. A switch does so by having an in-built learning of the MAC address of the

devices connected to it.

5.3.3 Bridges

A bridge is a computer networking device that builds the connection with the other bridge

networks which use the same protocol. It works at the Data Link layer of the OSI Model and

connects the different networks together and develops communication between them. It connects

two local-area networks; two physical LANs into larger logical LAN or two segments of the

same LAN that use the same protocol.

Types of Bridges:

There are mainly three types in which bridges can be characterized:

Transparent Bridge: As the name signifies, it appears to be transparent for the other

devices on the network. The other devices are ignorant of its existence. It only blocks or

forwards the data as per the MAC address.

Source Route Bridge: It derives its name from the fact that the path which packet takes

through the network is implanted within the packet. It is mainly used in Token ring

networks.

Translational Bridge: The process of conversion takes place via Translational Bridge. It

converts the data format of one networking to another. For instance Token ring to

Ethernet and vice versa.

5.3.4 Routers

Routers are network layer devices and are particularly identified as Layer- 3 devices of the OSI

Model. They process logical addressing information in the Network header of a packet such as

IP Addresses. Router is used to create larger complex networks by complex traffic routing. It has

the ability to connect dissimilar LANs on the same protocol. It also has the ability to limit the

flow of broadcasts. A router primarily comprises of a hardware device or a system of the

computer which has more than one network interface and routing software.

5.3.5 Gateways

Gateway is a device which is used to connect multiple networks and passes packets from one

packet to the other network. Acting as the ‘gateway’ between different networking systems or

computer programs, a gateway is a device which forms a link between them. It allows the

computer programs, either on the same computer or on different computers to share information

across the network through protocols. A router is also a gateway, since it interprets data from one

network protocol to another.

Others such as bridge converts the data into different forms between two networking systems.

Then a software application converts the data from one format into another. Gateway is a viable

tool to translate the data format, although the data itself remains unchanged. Gateway might be

installed in some other device to add its functionality into another.

5.3.6 Network card

Network cards also known as Network Interface Cards (NICs) are hardware devices that connect

a computer with the network. They are installed on the mother board. They are responsible for

developing a physical connection between the network and the computer. Computer data is

translated into electrical signals send to the network via Network Interface Cards.

They can also manage some important data-conversion function. These days network cards are

software configured unlike in olden days when drivers were needed to configure them. Even if

the NIC doesn’t come up with the software then the latest drivers or the associated software can

be downloaded from the internet as well.

VERY SHORT QUESTIONS

1. Name some connectivity devices?

2. What is the full form of NICs?

3. What are the types of types of hub?

4. What are the types of bridges?

5. Draw the diagram showing bridge connectivity?

SHORT QUESTIONS

1. What is hub?

2. What is router?

3. What is bridge?

4. What is the difference between bridge and hub?

5. What are gateways?

6. What are network interface card?

LONG QUESTIONS

1. Explain various network connectivity devices?

6. NETWORK ADMINISTRATION

6.1 Learning Objectives

Know about network security principals

Discuss cryptography

Elaborate troubleshooting tools

Discuss DHCP Server

6.2 Network Security Principles

The Three Primary Goals of Network Security

For most of today’s corporate networks, the demands of e-commerce and customer contact

require connectivity between internal corporate networks and the outside world. From a security

standpoint, two basic assumptions about modern corporate networks are as follows:

Today’s corporate networks are large, interconnect with other networks, and run both

standards-based and proprietary protocols.

The devices and applications connecting to and using corporate networks are continually

increasing in complexity

Because almost all (if not all) corporate networks require network security, consider the three

primary goals of network security:

Confidentiality

Integrity

Availability

Confidentiality

Data confidentiality implies keeping data private. This privacy could entail physically or

logically restricting access to sensitive data or encrypting traffic traversing a network. A network

that provides confidentiality would do the following, as a few examples:

Use network security mechanisms (for example, firewalls and access control lists [ACL]) to

prevent unauthorized access to network resources.

Require appropriate credentials (for example, usernames and passwords) to access specific

network resources.

Encrypt traffic such that an attacker could not decipher any traffic he captured from the

network.

Integrity

Data integrity ensures that data has not been modified in transit. Also, a data integrity solution

might perform origin authentication to verify that traffic is originating from the source that

should be sending it.

Examples of integrity violations include

Modifying the appearance of a corporate website

Intercepting and altering an e-commerce transaction

Modifying financial records that are stored electronically

Availability

The availability of data is a measure of the data’s accessibility. For example, if a server were

down only five minutes per year, it would have an availability of 99.999 percent (that is, “five

nines” of availability).

Here are a couple of examples of how an attacker could attempt to compromise the availability

of a network:

He could send improperly formatted data to a networked device, resulting in an unhandled

exception error.

He could flood a network system with an excessive amount of traffic or requests. This would

consume the system’s processing resources and prevent the system from responding to many

legitimate requests. This type of attack is called a denial-of-service (DoS) attack.

6.2.1 Cryptography

Cryptography involves creating written or generated codes that allow information to be kept

secret. Cryptography converts data into a format that is unreadable for an unauthorized user,

allowing it to be transmitted without unauthorized entities decoding it back into a readable

format, thus compromising the data.

Information security uses cryptography on several levels. The information cannot be read

without a key to decrypt it. The information maintains its integrity during transit and while being

stored. Cryptography also aids in nonrepudiation. This means that the sender and the delivery of

a message can be verified.

Cryptography is also known as cryptology.

Cryptography is classified into symmetric cryptography, asymmetric cryptography and hashing.

Below are the description of these types.

Symmetric key cryptography –

It involves usage of one secret key along with encryption and decryption algorithms which

help in securing the contents of the message. The strength of symmetric key cryptography

depends upon the number of key bits. It is relatively faster than asymmetric key

cryptography. There arises a key distribution problem as the key has to be transferred from

the sender to receiver through a secure channel.

Asymmetric key cryptography –

It is also known as public key cryptography because it involves usage of a public key

along with secret key. It solves the problem of key distribution as both parties uses

different keys for encryption/decryption. It is not feasible to use for decrypting bulk

messages as it is very slow compared to symmetric key cryptography.

Hashing –

It involves taking the plain-text and converting it to a hash value of fixed size by a hash

function. This process ensures integrity of the message as the hash value on both, sender\’s

and receiver\’s side should match if the message is unaltered.

6.3 Troubleshooting Tools

6.3.1 Ping:

The most commonly used network tool is the ping utility. This utility is used to provide a basic

connectivity test between the requesting host and a destination host. This is done by using the

Internet Control Message Protocol (ICMP) which has the ability to send an echo packet to a

destination host and a mechanism to listen for a response from this host. Simply stated, if the

requesting host receives a response from the destination host, this host is reachable. This utility is

commonly used to provide a basic picture of where a specific networking problem may exist. For

example, if an Internet connection is down at an office, the ping utility can be used to figure out

whether the problem exists within the office or within the network of the Internet provider.

6.3.2Tracert/traceroute

Typically, once the ping utility has been used to determine basic connectivity, the

tracert/traceroute utility can used to determine more specific information about the path to the

destination host including the route the packet takes and the response time of these intermediate

hosts. Figure below shows an example of the tracert utility being used to find the path from a

host inside an office to www.google.com. The tracert utility and traceroute utilities perform the

same function but operate on different operating systems, Tracert for Windows machines and

traceroute for Linux/*nix based machines.

6.3.3 Ipconfig/ifconfig

One of the most important things that must be completed when troubleshooting a networking

issue is to find out the specific IP configuration of the variously affected hosts. Sometimes this

information is already known when addressing is configured statically, but when a dynamic

addressing method is used, the IP address of each host can potentially change often. The utilities

that can be used to find out this IP configuration information include the ipconfig utility on

Windows machines and the ifconfig utility on Linux/*nix based machines.

6.3.4 Netstat

Often, one of the things that are required to be figured out is the current state of the active

network connections on a host. This is very important information to find for a variety of

reasons. For example, when verifying the status of a listening port on a host or to check and see

what remote hosts are connected to a local host on a specific port. It is also possible to use the

netstat utility to determine which services on a host that is associated with specific active ports.

Figure below shows an example of the netstat utility being used to display the currently active

ports on a Linux machine.

6.3.5 Wireshark

Wireshark is a network or protocol analyzer (also known as a network sniffer) available for free

at the Wireshark website. It is used to analyze the structure of different network protocols and

has the ability to demonstrate encapsulation. The analyzer operates on Unix, Linux and

Microsoft Windows operating systems, and employs the GTK+ widget toolkit and pcap for

packet capturing. Wireshark and other terminal-based free software versions like Tshark are

released under the GNU General Public License.

Wireshark shares many characteristics with tcpdump. The difference is that it supports a

graphical user interface (GUI) and has information filtering features. In addition, Wireshark

permits the user to see all the traffic being passed over the network.

Features of Wireshark include:

Data is analyzed either from the wire over the network connection or from data files that

have already captured data packets.

Supports live data reading and analysis for a wide range of networks (including Ethernet,

IEEE 802.11, point-to-point Protocol (PPP) and loopback).

With the help of GUI or other versions, users can browse captured data networks.

For programmatically editing and converting the captured files to the editcap application,

users can use command line switches.

Display filters are used to filter and organize the data display.

New protocols can be scrutinized by creating plug-ins.

Captured traffic can also trace Voice over Internet (VoIP) calls over the network.

6.3.6 Nmap

Nmap, short for Network Mapper, is a free, open-source tool for vulnerability scanning and

network discovery. Network administrators use Nmap to identify what devices are running on

their systems, discovering hosts that are available and the services they offer, finding open ports

and detecting security risks.

Nmap can be used to monitor single hosts as well as vast networks that encompass hundreds of

thousands of devices and multitudes of subnets.

Though Nmap has evolved over the years and is extremely flexible, at heart it's a port-scan tool,

gathering information by sending raw packets to system ports. It listens for responses and

determines whether ports are open, closed or filtered in some way by, for example, a firewall.

Other terms used for port scanning include port discovery or enumeration.

6.3.7 TCPDUMP

tcpdump is a most powerful and widely used command-line packets sniffer or package analyzer

tool which is used to capture or filter TCP/IP packets that received or transferred over a network

on a specific interface. It is available under most of the Linux/Unix based operating systems.

6.4 DHCP Server

A DHCP Server is a network server that automatically provides and assigns IP addresses, default

gateways and other network parameters to client devices. It relies on the standard protocol

known as Dynamic Host Configuration Protocol or DHCP to respond to broadcast queries by

clients.

A DHCP server automatically sends the required network parameters for clients to properly

communicate on the network. Without it, the network administrator has to manually set up every

client that joins the network, which can be cumbersome, especially in large networks. DHCP

servers usually assign each client with a unique dynamic IP address, which changes when the

client’s lease for that IP address has expired.

VERY SHORT QUESTIONS

1. What do you mean by network security?

2. What are network security principles?

3. What is cryptography?

4. What is hashing?

5. What is the full form of DHCP?

6. What is cryptology?

7. What is symmetric key cryptography?

8. What is asymmetric key cryptography?

9. What is TCPDUMP?

SHORT QUESTIONS

1. What is ping command?

2. What is DHCP server?

3. What is Tracert/traceroute?

4. What is ipconfig command?

5. Mention about wireshark?

6. Discuss about Nmap?

LONG QUESTIONS

1. What is network security principles?

2. What is cryptography?

3. Explain various troubleshooting tools?

7. INTRODUCTION TO WIRELESS NETWORK

7.1 Learning Objectives

Know about wireless lan

Discuss architecture of wireless lan

Discuss wimax and lifi

Elaborate Bluetooth architecture

Discuss its applications

7.2 Introduction to wireless Lan-802.11

A wireless LAN (WLAN or WiFi) is a data transmission system designed to provide location-

independent network access between computing devices by using radio waves rather than a

cable infrastructure

In the corporate enterprise, wireless LANs are usually implemented as the final link between

the existing wired network and a group of client computers, giving these users wireless access

to the full resources and services of the corporate network across a building or campus setting.

The widespread acceptance of WLANs depends on industry standardization to ensure product

compatibility and reliability among the various manufacturers.

The 802.11 specification [IEEE Std 802.11 (ISO/IEC 8802-11: 1999)] as a standard for

wireless LANS was ratified by the Institute of Electrical and Electronics Engineers (IEEE) in

the year 1997. This version of 802.11 provides for 1 Mbps and 2 Mbps data rates and a set of

fundamental signaling methods and other services. Like all IEEE 802 standards, the 802.11

standards focus on the bottom two levels the ISO model, the physical layer and link layer (see

figure below). Any LAN application, network operating system, protocol, including TCP/IP

and Novell NetWare, will run on an 802.11-compliant WLAN as easily as they run over

Ethernet.

7.2.1 IEEE 802.11 Architecture

Each computer, mobile, portable or fixed, is referred to as a station in 802.11 [Wireless Local

Area Networks].

The difference between a portable and mobile station is that a portable station moves from

point to point but is only used at a fixed point. Mobile stations access the LAN during

movement.

When two or more stations come together to communicate with each other, they form a Basic

Service Set (BSS). The minimum BSS consists of two stations. 802.11 LANs use the BSS as

the standard building block.

A BSS that stands alone and is not connected to a base is called an Independent Basic Service

Set (IBSS) or is referred to as an Ad-Hoc Network. An ad-hoc network is a network where

stations communicate only peer to peer. There is no base and no one gives permission to talk.

Mostly these networks are spontaneous and can be set up rapidly. Ad-Hoc or IBSS networks

are characteristically limited both temporally and spatially.

When BSS's are interconnected the network becomes one with infrastructure. 802.11

infrastructure has several elements. Two or more BSS's are interconnected using a Distribution

System or DS. This concept of DS increases network coverage. Each BSS becomes a

component of an extended, larger network. Entry to the DS is accomplished with the use of

Access Points (AP). An access point is a station, thus addressable. So, data moves between the

BSS and the DS with the help of these access points.

Creating large and complex networks using BSS's and DS's leads us to the next level of

hierarchy, the Extended Service Set or ESS. The beauty of the ESS is the entire network looks

like an independent basic service set to the Logical Link Control layer (LLC). This means that

stations within the ESS can communicate or even move between BSS′s transparently to the LLC.

One of the requirements of IEEE 802.11 is that it can be used with existing wired networks.

802.11 solved this challenge with the use of a Portal. A portal is the logical integration

between wired LANs and 802.11. It also can serve as the access point to the DS. All data

going to an 802.11 LAN from an 802.X LAN must pass through a portal. It thus functions as

bridge between wired and wireless.

The implementation of the DS is not specified by 802.11. Therefore, a distribution system may

be created from existing or new technologies. A point-to-point bridge connecting LANs in two

separate buildings could become a DS.

While the implementation for the DS is not specified, 802.11 does specify the services, which

the DS must support. Services are divided into two sections

1. Station Services (SS)

2. Distribution System Services (DSS).

There are five services provided by the DSS

1. Association

2. Reassociation

3. Disassociation

4. Distribution

5. Integration

7.2.3 Wimax

WiMAX is one of the hottest broadband wireless technologies around today. WiMAX systems

are expected to deliver broadband access services to residential and enterprise customers in an

economical way.

Loosely, WiMax is a standardized wireless version of Ethernet intended primarily as an

alternative to wire technologies (such as Cable Modems, DSL and T1/E1 links) to provide

broadband access to customer premises.

More strictly, WiMAX is an industry trade organization formed by leading communications,

component, and equipment companies to promote and certify compatibility and interoperability

of broadband wireless access equipment that conforms to the IEEE 802.16 and ETSI

HIPERMAN standards.

WiMAX would operate similar to WiFi, but at higher speeds over greater distances and for a

greater number of users. WiMAX has the ability to provide service even in areas that are

difficult for wired infrastructure to reach and the ability to overcome the physical limitations of

traditional wired infrastructure.

WiMAX was formed in April 2001, in anticipation of the publication of the original 10-66 GHz

IEEE 802.16 specifications. WiMAX is to 802.16 as the WiFi Alliance is to 802.11.

7.2.4 Lifi

LiFi is a wireless optical networking technology that uses light-emitting diodes (LEDs) for data

transmission.

LiFi is designed to use LED light bulbs similar to those currently in use in many energy-

conscious homes and offices. However, LiFi bulbs are outfitted with a chip that modulates the

light imperceptibly for optical data transmission. LiFi data is transmitted by the LED bulbs and

received by photoreceptors.

LiFi's early developmental models were capable of 150 megabits-per-second (Mbps). Some

commercial kits enabling that speed have been released. In the lab, with stronger LEDs and

different technology, researchers have enabled 10 gigabits-per-second (Gbps), which is faster

than 802.11ad.

Benefits of LiFi:

Higher speeds than Wi-Fi.

10000 times the frequency spectrum of radio.

More secure because data cannot be intercepted without a clear line of sight.

Prevents piggybacking.

Eliminates neighboring network interference.

Unimpeded by radio interference.

Does not create interference in sensitive electronics, making it better for use in environments

like hospitals and aircraft.

7.3 Bluetooth

7.3.1Bluetooth Architecture

Bluetooth communication occurs between a master radio and a slave radio. Bluetooth radios are

symmetric in that the same device may operate as a master and also the slave. Each radio has a

48-bit unique device address (BD_ADDR) that is fixed.

Two or more radio devices together form ad-hoc networks called piconets. All units within a

piconet share the same channel. Each piconet has one master device and one or more slaves.

There may be up to seven active slaves at a time within a piconet. Thus, each active device

within a piconet is identifiable by a 3-bit active device address. Inactive slaves in unconnected

modes may continue to reside within the piconet.

A master is the only one that may initiate a Bluetooth communication link. However, once a link

is estBablished, the slave may request a master/slave switch to become the master. Slaves are not

allowed to talk to each other directly. All communication occurs within the slave and the master.

Slaves within a piconet must also synchronize their internal clocks and frequency hops with that

of the master. Each piconet uses a different frequency hopping sequence. Radio devices used

Time Division Multiplexing (TDM). A master device in a piconet transmits on even numbered

slots and the slaves may transmit on odd numbered slots.

Multiple piconets with overlapping coverage areas form a scatternet. Each piconet may have

only one master, but slaves may participate in different piconets on a time-division multiplex

basis. A device may be a master in one piconet and a slave in another or a slave in more than one

piconet.

7.3.2 Bluetooth Applications

Allows a transfer of images (or) word documents (or) applications (or) audio and video files

between devices without the help of cables.

Can be used for remote sales technology allowing wireless access to vending machines and

other commercial enterprises.

Provides inter accessibility of PDAs, palmtops and desktops for file and data exchanges.

It can be used to setup a personal area network (PAN) or a wireless personal area network

(WPAN).

VERY SHORT QUESTIONS

1. what is the full form of PAN?

2. What is the full form of WPAN?

3. Which technology us used in lifi?

4. What is the full form of TDM?

5. What is the full form of WLAN?

6. What does ESS and BSS stand for?

7. What does IEEE stand for?

8. What is the IEEE specification for WLAN?

SHORT QUESTIONS

1. Discuss about WLAN in brief?

2. What is Wimax?

3. What is lifi and what are its benefits?

4. What are the applications of Bluetooth?

5. What is piconet?

LONG QUESTIONS

1. Discuss about WLAN and its architecture in detail?

2. Mention about Bluetooth architecture?

8. CLOUD COMPUTING

8.1Learning objectives

Describe cloud computing.

Know about advantages and applications of cloud computing.

Elaborate about history of cloud computing.

Know about challenges of cloud computing.

8.2 What is Cloud?

The term Cloud refers to a Network or Internet. In other words, we can say that Cloud is

something, which is present at remote location. Cloud can provide services over network, i.e.,

on public networks or on private networks, i.e., WAN, LAN or VPN. Applications such as e-

mail, web conferencing, customer relationship management (CRM), all run in cloud.

8.3 What is Cloud Computing?

Cloud Computing refers to manipulating, configuring, and accessing the applications online. It offers online data storage, infrastructure and application.

8.4 Advantages of Cloud Computing

Cloud Computing has numerous advantages. Some of them are listed below:

One can access applications as utilities, over the Internet.

Manipulate and configure the application online at any time.

It does not require installing a specific piece of software to access or manipulating cloud

application.

Cloud Computing offers online development and deployment tools, programming runtime environment through Platform as a Service model

Cloud resources are available over the network in a manner that provides platform independent access to any type of clients.

Cloud Computing offers on-demand self-service. The resources can be used without interaction with cloud service provider.

Cloud Computing is highly cost effective because it operates at higher efficiencies with greater utilization. It just requires an Internet connection.

Cloud Computing offers load balancing that makes it more reliable.

8.5 SERVICE MODELS

8.5.1. Infrastructure as a service

Iaas provider’s access to fundamental resources such as physical machines, virtual machines,

virtual storage, etc., Apart from these resources, the IaaS also offers:

Virtual machine disk storage

Virtual local area network (VLANs)

Load balancers

IP addresses

Software bundles

All of the above resources are made available to end user via server virtualization. Moreover,

these resources are accessed by the customers as if they own them.

Benefits:

IaaS allows the cloud provider to freely locate the infrastructure over the Internet in a cost-

effective manner. Some of the key benefits of IaaS are listed below:

Full Control of the computing resources through Administrative Access to VMs.

Flexible and Efficient renting of Computer Hardware.

Portability, Interoperability with Legacy Applications.

Issues:

IaaS shares issues with PaaS and SaaS, such as Network dependence and browser based risks. It

also have some specific issues associated with it. These issues are mentioned in the following

diagram:

Compatibility With Legacy Security Vulnerabilities

Because IaaS offers the consumer to run legacy software in provider's infrastructure, therefore it

exposes consumers to all of the security vulnerabilities of such legacy software.

Virtual Machine Sprawl

The VM can become out of date with respect to security updates because IaaS allows the

consumer to operate the virtual machines in running, suspended and off state. However, the

provider can automatically update such VMs, but this mechanism is hard and complex.

Robustness Of Vm-Level Isolation

IaaS offers an isolated environment to individual consumers through hypervisor. Hypervisor

is a software layer that includes hardware support for virtualization to split a physical

computer into multiple virtual machines.

Data Erase Practices

The consumer uses virtual machines that in turn use the common disk resources provided by

the cloud provider. When the consumer releases the resource, the cloud provider must ensure

that next consumer to rent the resource does not observe data residue from previous

consumer.

Characteristics:

Here are the characteristics of IaaS service model:

Virtual machines with pre-installed software.

Virtual machines with pre-installed Operating Systems such as Windows, Linux, and Solaris.

On-demand availability of resources.

Allows to store copies of particular data in different locations.

The computing resources can be easily scaled up and down.

8.5.2 Platform as a Service(PAAS)-

It also offers development & deployment tools, required to develop applications. PaaS has a

feature of point-and-click tools that enables non-developers to create web applications.Google's

App Engine, Force.com are examples of PaaS offering vendors. Developer may log on to

thesewebsites and use the built-in API to create web-based applications.

But the disadvantage of using PaaS is that the developer lock-in with a particular vendor. For

example, an application written in Python against Google's API using Google's App Engine is

likely to work only in that environment. Therefore, the vendor lock-in is the biggest problem in

PaaS.

The following diagram shows how PaaS offers an API and development tools to the developers

and how it helps the end user to access business applications.

Benefits:

Lower Administrative Overhead

Consumer need not to bother much about the administration because it's the responsibility of

cloud provider.

Lower Total Cost Of Ownership

Consumer need not purchase expensive hardware, servers, power and data storage.

Scalable Solutions

It is very easy to scale up or down automatically based on application resource demands.

More Current System Softwar

It is the responsibility of the cloud provider to maintain software versions and patch

installations.

Issues:

Lack Of Portability Between Paas Clouds

Although standard languages are used yet the implementations of platforms services may

vary. For example, file, queue, or hash table interfaces of one platform may differ from

another, making it difficult to transfer workloads from one platform to another.

Event Based Processor Scheduling

The PaaS applications are event oriented which poses resource constraints on applications, i.e.,

they have to answer a request in a given interval of time.

Security Engineering Of Paas Applications

Since the PaaS applications are dependent on network, PaaS applications must explicitly use

cryptography and manage security exposures.

Characteristics:

Here are the characteristics of PaaS service model:

PaaS offers browser based development environment. It allows the developer to create

database and edit the application code either via Application Programming Interface or point-

and-click tools.

PaaS provides built-in security, scalability, and web service interfaces.

PaaS provides built-in tools for defining workflow and approval processes and defining

business rules.

It is easy to integrate with other applications on the same platform.

PaaS also provides web services interfaces that allow us to connect the applications outside

the platform.

8.5.3 Software as a Service(SaaS )

This model allows providing software application as a service to the end users. It refers to a

software that is deployed on a hosted service and is accessible via Internet. There are

several

SaaS applications, some of them are listed below:

Billing and Invoicing System

Customer Relationship Management (CRM) applications

Help Desk Applications

Human Resource (HR) Solutions

Some of the SaaS applications are not customizable such as an Office Suite. But SaaS

provides us Application Programming Interface (API), which allows the developer to develop

a customized application.

Characteristics:

Here are the characteristics of SaaS service model:

SaaS makes the software available over the Internet.

The Software are maintained by the vendor rather than where they are running.

The license to the software may be subscription based or usage based. And it is billed on

recurring basis.

SaaS applications are cost effective since they do not require any maintenance at end user

side.

They are available on demand.

They can be scaled up or down on demand.

They are automatically upgraded and updated.

SaaS offers share data model. Therefore, multiple users can share single instance of

infrastructure. It is not required to hard code the functionality for individual users.

All users are running same version of the software.

Benefits:

Using SaaS has proved to be beneficial in terms of scalability, efficiency, performance and much

more. Some of the benefits are listed below:

Modest Software Tools

Efficient use of Software Licenses

Centralized Management & Data

Platform responsibilities managed by provider

Multitenant solutions

Issues:

There are several issues associated with SaaS, some of them are listed below:

Browser Based Risks

If the consumer visits malicious website and browser becomes infected, and the subsequent

access to SaaS application might compromise the consumer's data. To avoid such risks, the

consumer can use multiple browsers and dedicate a specific browser to access SaaS

applications or can use virtual desktop while accessing the SaaS applications.

Network Dependence

The SaaS application can be delivered only when network is continuously available. Also

network should be reliable but the network reliability cannot be guaranteed either by cloud

provider or the consumer.

Lack Of Portability Between Saas Clouds

Transferring workloads from one SaaS cloud to another is not so easy because work flow,

business logics, user interfaces, support scripts can be provider specific

8.6 Deployment Models

8.6.1 Public clouds

The Public Cloud allows systems and services to be easily accessible to general public, e.g.,

Google, Amazon, Microsoft offers cloud services via Internet.

Benefits:

Cost Effective

Since public cloud share same resources with large number of consumer, it has low cost.

Reliability:

Since public cloud employs large number of resources from different locations, if any of the

resource fail, public cloud can employ another one.

Flexibility

It is also very easy to integrate public cloud with private cloud, hence gives consumers a

flexible approach.

Location Independence

Since, public cloud services are delivered through Internet, therefore ensures location

independence.

Utility Style Costing

Public cloud is also based on pay-per-use model and resources are accessible whenever

consumer needs it.

High Scalability

Cloud resources are made available on demand from a pool of resources, i.e., they can be

scaled up or down according the requirement.

Disadvantages:

Here are the disadvantages of public cloud model:

Low Security

In public cloud model, data is hosted off-site and resources are shared publicly, therefore

does not ensure higher level of security.

Less Customizable

It is comparatively less customizable than private cloud.

8.6.2 Private cloud

The Private Cloud allows systems and services to be accessible within an organization. The

Private Cloud is operated only within a single organization. However, it may be managed

internally or by third-party.

Benefits:

Higher Security And Privacy

Private cloud operations are not available to general public and resources are shared from

distinct pool of resources, therefore, ensures high security and privacy.

More Control

Private clouds have more control on its resources and hardware than public cloud because it

is accessed only within an organization.

Cost And Energy Efficiency

Private cloud resources are not as cost effective as public clouds but they offer more

efficiency than public cloud.

Disadvantages:

Here are the disadvantages of using private cloud model:

Restricted Area

Private cloud is only accessible locally and is very difficult to deploy globally.

Inflexible Pricing

In order to fulfill demand, purchasing new hardware is very costly.

Limited Scalability

Private cloud can be scaled only within capacity of internal hosted resources.

8.6.3 Hybrid cloud

The Hybrid Cloud is a mixture of public and private cloud. Non-critical activities are performed

using public cloud while the critical activities are performed using private cloud.

Benefits:

Scalability

It offers both features of public cloud scalability and private cloud scalability.

Flexibility

It offers both secure resources and scalable public resources.

Cost Efficiencies

Public cloud are more cost effective than private, therefore hybrid cloud can have this saving.

Security

Private cloud in hybrid cloud ensures higher degree of security.

Disadvantages:

Networking Issues

Networking becomes complex due to presence of private and public cloud.

Security Compliance

It is necessary to ensure that cloud services are compliant with organization's security

policies.

8.6.4 Community cloud

The community Cloud allows system and services to be accessible by group of organizations. It

shares the infrastructure between several organizations from a specific community. It may be

managed internally or by the third-party.

Benefits:

There are many benefits of deploying cloud as community cloud model. The following diagram

shows some of those benefits:

Cost Effective

Community cloud offers same advantage as that of private cloud at low cost.

Sharing Between Organizations

Community cloud provides an infrastructure to share cloud resources and capabilities among

several organizations.

Security

Community cloud is comparatively more secure than the public cloud.

Issues:

Since all data is housed at one location, one must be careful in storing data in community

cloud because it might be accessible by others.

It is also challenging to allocate responsibilities of governance, security and cost.

Very short questions

1. What are different service models? Name them.

2. Name fundamental resources of Iaas?

3. Give two benefits of Iaas?

4. Paas is also known as.

5. What is private cloud?

6. What is hybrid cloud?

7. What is community cloud?

8. What is cloud?

9. What is cloud compting?

Short questions

1. Name different cloud service models with suitable example?

2. Explain characteristics of Iaas model?

3. Define private cloud along with diagram.

4. Explain benefits of private cloud?

5. What are the issues found with Paas?

6. What are the advantages of cloud computing?

Long questions

1. Explain Iaas along with four benefits, issues and characteristics.

2. What is the difference between public cloud, private cloud, hybrid cloud, community cloud?

3. Explain cloud computing deployment models in detail.

4. What are the advantages, characteristics and disadvantages of SAAS?

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