Network Definition

 A network is a group of two or more computer systems linked together. There are many types of computer networks, including:

Local-area networks (LANs) : The computers are geographically close together (that is, in the same building).

Wide-area networks (WANs) : The computers are farther apart and are connected by telephone lines or radio waves.

Campus-area networks (CANs): The computers are within a limited geographic area, such as a campus or military base.

metropolitan-area networks MANs): A data network designed for a town or city. Home-area networks (HANs): A network contained within a user's home that connects

a person's digital devices.

Topology : The geometric arrangement of a computer system. Common topologies include a bus, star, and ring. See the Network topology diagrams in the Quick Reference section of Webopedia.

Protocol : The protocol defines a common set of rules and signals that computers on the network use to communicate. One of the most popular protocols for LANs is called 

Ethernet. Another popular LAN protocol for PCs is the IBM token-ring network.

Architecture : Networks can be broadly classified as using either a peer-to-peer or client/server architecture.

OSI Model

The Open Systems Interconnection model (OSI) is a conceptual model that characterizes and standardizes the internal functions of a communication system by partitioning it into abstraction layers. 

The seven layers of the OSI Basic Reference Model are (from bottom to top): The Physical Layer describes the physical properties of the various communications

media, as well as the electrical properties and interpretation of the exchanged signals. Ex: this layer defines the size of Ethernet coaxial cable, the type of BNC connector used, and the termination method.

The Data Link Layer describes the logical organization of data bits transmitted on a particular medium. Ex: this layer defines the framing, addressing and check summing of Ethernet packets.

The Network Layer describes how a series of exchanges over various data links can deliver data between any two nodes in a network. Ex: this layer defines the addressing and routing structure of the Internet.

The Transport Layer describes the quality and nature of the data delivery. Ex: this layer defines if and how retransmissions will be used to ensure data delivery.

The Session Layer describes the organization of data sequences larger than the packets handled by lower layers. Ex: this layer describes how request and reply packets are paired in a remote procedure call.

The Presentation Layer describes the syntax of data being transferred. Ex: this layer describes how floating point numbers can be exchanged between hosts with different math formats.

The Application Layer describes how real work actually gets done. Ex: this layer would implement file system operations.

Token Ring

Token Ring/IEEE 802.5

Token ring local area network (LAN) technology is a protocol which resides at the data link layer (DLL) of the OSI model. It uses a special three-byte frame called a token that travels around the ring. Token-possession grants the possessor permission to transmit on the medium. Token ring frames travel completely around the loop. Media Access Unit

Fiber Distributed Data Interface (FDDI)

Fiber Distributed Data Interface (FDDI) provides a 100 Mbit/s optical standard for data transmission in a local area network that can extend in range up to 200 kilometers (120 mi). Although FDDI logical topology is a ring-based token network, it does not use the IEEE 802.5 token ring protocol as its basis; instead, its protocol is derived from the IEEE 802.4 token burs timed token protocol.

Wireless Networks

In this networks the networks are connected by means of wireless devices The most prominent type of wireless networks are

Blue Tooth Wi-Fi Wi-Max 802.11

Bluetooth is a proprietary open wireless technology standard for exchanging data over short distances (using short-wavelength radio transmissions in the ISM band from 2400–2480 MHz) from fixed and mobile devices, creating personal area networks (PANs) with high levels of security.

Wi-Fi is a popular technology that allows an electronic device to exchange data wirelessly (using radio waves) over a computer network, including high-speed Internet connections.

WiMAX (Worldwide Interoperability for Microwave Access) is a wireless communications standard designed to provide 30 to 40 megabit-per-second data rates, with the 2011 update providing up to 1 Gbit/s for fixed stations.

IEEE 802.11 is a set of standards for implementing wireless local area network (WLAN) computer communication in the 2.4, 3.6 and 5 GHz frequency bands. They are created and maintained by the IEEELAN/MAN Standards Committee (IEEE 802).

Wireless PAN

Wireless personal area networks (WPANs) interconnect devices within a relatively small area, that is generally within a person's reach.[3] For example, both Bluetooth radio and invisible infrared light provides a WPAN for interconnecting a headset to a laptop.

Wireless LAN

A wireless local area network (WLAN) links two or more devices over a short distance using a wireless distribution method, usually providing a connection through an access point for Internet access. The use of spectrum. Products using the IEEE 802.11

Wireless mesh network

A wireless mesh network is a wireless network made up of radio nodes organized in a mesh topology. Each node forwards messages on behalf of the other nodes. Mesh networks can "self heal", automatically re-routing around a node that has lost power.

Wireless MAN

Wireless metropolitan area networks are a type of wireless network that connects several wireless LANs. Example WiMAX

Wireless WAN

Wireless wide area networks are wireless networks that typically cover large areas, such as between neighboring towns and cities, or city and suburb. Point to point microwave links

Cellular network

A cellular network or mobile network is a radio network distributed over land areas called cells, each served by at least one fixed-location transceiver, known as a cell site or base station.

Repeater

A repeater is an electronic device that receives a signal and retransmits it at a higher level or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances

Ethernet Hub

An Ethernet hub, active hub, network hub, repeater hub, multiport repeater or hub is a device for connecting multiple Ethernet devices together and making them act as a single network segment.

Network Switch

A network switch or switching hub is a computer networking device that connects network segments or network devices.

CSU/DSU

A CSU/DSU (Channel Service Unit/Data Service Unit) is a digital-interface device used to connect a Data Terminal Equipment device or DTE, such as a router, to a digital circuit, such as a T1 line.

Functions of CSU/DSU

The CSU/DSU implements two different functions.

The CSU is responsible for

The connection to the telecom network

The DSU is responsible

For handling the interface with the DTE.

DSL

A digital subscriber line (DSL) modem is a device used to connect a computer or router to a telephone line which has the digital subscriber line service configured, to allow the computer to connect to the Internet.

OR

A DSL modem or DSL router is what you need in order to connect to DSL broadband.

IP addressing

Types of IP address

Static address Dynamic address

Static IP address

manually input by network administrator manageable for small networks requires careful checks to avoid duplication

Dynamic IP address

examples - BOOTP, DHCP assigned by server when host boots derived automatically from a range of addresses duration of ‘lease’ negotiated, then address released back to server

Classes of IP address

Class A - large organizations , governments Class B - medium sized organizations Class C - small organizations

An Internet Protocol address (IP address) is a numerical label assigned to each device (e.g., computer, printer) participating in a computer network that uses the Internet Protocol for communication.

IP Address

Class

Total # Of Bits For Network ID / Host

ID

First Octet of

IP Address

# Of Network ID Bits

Used To Identify Class

Usable # Of

Network ID Bits

Number of Possible Network

IDs

# Of Host IDs Per

Network ID

Class A 8 / 24 0xxx xxxx 1 8-1 = 7 27-2 = 126 224-2 = 16,277,214

Class B 16 / 16 10xx xxxx 2 16-2 = 14 214 = 16,384

216-2 = 65,534

Class C 24 / 8 110x xxxx 3 24-3 = 21 221 = 2,097,152 28-2 = 254

TCP/IP networking

IP : Internet Protocol

UDP : User Datagram Protocol

RTP, traceroute

– TCP : Transmission Control Protocol

HTTP, FTP, ssh

TCP

• Reliable, full-duplex, connection-oriented, stream delivery

– Interface presented to the application doesn’t require data in individual packets

– Data is guaranteed to arrive, and in the correct order without duplications

• Or the connection will be dropped

– Imposes significant overheads

Applications of TCP

• Most things!

– HTTP, FTP, …

• Saves the application a lot of work, so used unless there’s a good reason not to

TCP implementation

• Connections are established using a three-way handshake

• Data is divided up into packets by the operating system

• Packets are numbered, and received packets are acknowledged

• Connections are explicitly closed (or may abnormally terminate)

TCP Segment

Three Way Handshake

Numerical Problems on the Network

Store-and-forward (SF) switching

This technique is alternatively called packet switching.

Each packet hasheader. Buffersfor packet. Move from source to the destination. One step of SF is called hop. Routing decisions are done by intermediate router

Next – Hop Forwarding

The routing table consists of at least three information fields:

1. the network id: i.e. the destination network id2. cost: i.e. the cost or metric of the path through which the packet is to be sent3. next hop: The next hop, or gateway, is the address of the next station to which the packet is to be

sent on the way to its final destination

Router based Architecture

Address Resolution Protocol

The Address Resolution Protocol (ARP) feature performs a required function in IP routing. ARP finds the hardware address, also known as Media Access Control (MAC) address, of a host from its known IP address. ARP maintains a cache (table) in which MAC addresses are mapped to IP addresses.

The ARP request message has the following fields:

•  HLN--Hardware address length. Specifies how long the hardware addresses are in the message. For IEEE 802 MAC addresses (Ethernet) the value is 6.

•  PLN--Protocol address length. Specifies how long the protocol (Layer 3) addresses are in the message. For IPv4, the value is 4.

•  OP--Opcode. Specifies the nature of the message by code:

–  1--ARP request.

–  2--ARP reply.

– 3 through 9--RARP and Inverse ARP requests and replies.

•  SHA--Sender hardware address. Specifies the Layer 2 hardware address of the device sending the message.

•  SPA--Sender protocol address. Specifies the IP address of the sending device.

•  THA--Target hardware address. Specifies the Layer 2 hardware address of the receiving device.

•  TPA--Target protocol address. Specifies the IP address of the receiving device.

Datagram Encapsulation

• A datagram is encapsulated in a frame

• The destination address in the frame is the address of the next hop

• The destination of the next hop is obtained by translating the IP address of the next hop to an equivalent hardware address.

Architecture of encapsulation

Fragmentation

• A smaller MTU, it is possible to further fragment a fragment.

• No distinguish between original fragments and sub fragments.

• Reassembly without first reassembling sub fragments.

Link state Algorithm:

Each router must do the following:

• Discover neighbors, know their network address.

• Find delay or cost to each of its neighbors.

• Construct a packet.

• Send this packet to all other routers.

• Compute the shortest path to every other router.

Applications of Link state Algorithm:

• Calculating the routing tables.

• Distributing the maps

• Finding the shortest paths.

Example on Link state algorithm

Distance Vector routing algorithm:

Dijkstra's algorithm:

It is a graph search algorithm that solves the single-source shortest path problem for a graph with nonnegative edge path costs, producing a shortest path tree

Algorithm working

• It starts with the initial root node

• Compare all the distance

• Select the Minimum cost node

Application

• Traffic Information system

• Travelling Sales person problem

Client /Server concepts:

Client

• is one who sends the requests.

• is the consumer because he consumes the data from the producer.

• is connected to the server

•

Server:

• is one who produces the data to the client whenever he request

• is producer.

• is connected to many clients.

Applications: it will be used in the distributed computing.

The client and server are connected through the computer networks.

It will be sued in the cloud computing.

Disadvantages:

• Limited Band width.

• Congestion

• Low configuration servers to respond clients.

Port De-multiplexing:

• Port Multiplexing is responsible for running multiple network applications.

• These network applications are responsible for sending and receiving data.

• Transport layer protocols will implement these network applications by using port Numbers.

Port Number:

It used to to address particular applications to which we need to send the data. Port Numbers are classified into 3 categories. They are

• Well known ports: range is 0-1023 registered by IANA

• Registered ports: 1024-49151

• Private ports: 49152- 65535

Examples Port: port 1 –TCP 25 –SMTP

Socket

• Socket is used as end – end point connections between sender and receiver hosts.

• Socket is used for inter Process communications.

• Socket will be addressed by both IP and Port numbers.

• IP used to address to the host or system and port used to address the applications program.

• Sockets are developed between the transport layer and internet layer.

Types of sockets:

There are 3 types of sockets.

• Stream socket (connection Oriented) example: TCP Sockets.

• Data Gram Sockets (Connection Less) Example: UDP sockets.

• Raw Sockets.

Implementation:

• Sockets can be implemented using Application Programming Interface API called Socket API by using C and other Programming’s languages like java.

Server concurrency:

Concurrent server means One Server can able to communicate many clients at a time But where as Iterative server means one server can respond to one one client at a time. There are 2 types of concurrency servers they are TCP and UDP concurrent servers.

DNS (Domain name System):

• DNS means mapping IP address to Host name and host name to IP address.

• IP address is 32 bit

• Information is indexed by Domain Name

• The tree of domain names together is called the Domain Name Space

Types of DNS

• Iterative DNS Server

• Recursive DNS Server

TELNET (Telemetry Network)

• It is network protocol used in internet or LAN to provide bidirectional text data transfer.

• It used to connect client with their servers and can implement the client part.

• It is used in both windows and Linux operating systems.

Web Technologies:

The following are the types of web technologies used they are :

• HTML

• HTTP

• CGI

• JAVA

• RPC

• Middle ware

Java

Java has evolved to be the most predominant and popular general purpose programming language of the current age.

Java is a

• Developed by Sun Microsystems

• Simple,

• Portable,

• Distributed,

• Robust,

• Secure,

• Dynamic,

• Architecture neutral,

RPC: Remote Procedure Calls.

• It defines Procedures

• It defines methods

• Communication can be had between computer which are distributed geographically

Middle Ware Technologies:

Middleware is computer software that connects software components or people and their applications.

Types of Middle ware technologies:

• RMI - Remote Method Invocations

• CORBA – Common Object Recourse Broker Architecture

• .Net Technologies: C#, ASP.Net, VB.Net

Network management system

A network management system (NMS) is a combination of hardware and software used to monitor and administer a computer network or networks. Individual network elements (NEs) in a network are managed by an element management system.

Network Security:

• Network security starts with authenticating the user, commonly with a username and a password

• Communication between two hosts using a network may be encrypted to maintain privacy.

Cryptography:

• It is the process of encryption and decryption of data using key.

Encryption:

It is the process of transforming the plain text to cipher text

Example. Hello – Plain text Shift each character by 3 character positions.

Khoor – Cipher text

Decryption:

It is the process of transforming the cipher text to plain text

Encryption and decryption can be performed by using encryption algorithm and decryption algorithm by using the public and private key.

Example

• Khoor – Cipher text

• Hello – Plain text

Types of Cryptography

• Traditional Cryptography

• Symmetric Cryptography.

Types of Cryptography Algorithms

• RSA ( Ron Rivest, Adi Shamir and Leonard Adleman,)

• AES (Advance Encryption Standards)

• Triple DES (Data Encryption Standard