computer network complete introduction

Computer Networks 06.01.2016- 1

Computer Engineering and Applications

CSE4003: CN

Computer Networks:Introduction

Dr. Manas Kumar [email protected]


CSE4003 Computer Networks: Course Overview UNIT I

Introduction Concepts: Goals and Applications of Networks, Network structure and architecture, The OSI reference model, services, Network Topology Design, connecting devices,

Physical Layer: Transmission Media, Line coding scheme, Basic idea of modulation and multiplexing, Switching methods.

Medium Access sub layer: Medium Access sub layer - Channel Allocations, LAN protocols - ALOHA protocols, CSMA, CSMA/CD, Overview of IEEE standards

UNIT II Data Link Layer: HDLC and point to point protocol, Error detection and correction, Flow control

(sliding window protocol) Network Layer: Network Layer –IP addressing, Internetworking, Address mapping,

introduction to IPv6, transition from IPv4 to IPv6, routing. UNIT III

Transport Layer: Transport Layer - Design issues, connection management, Flow control, TCP window management, congestion control-slow start algorithm

Session Layer: Design issues, remote procedure call. Presentation Layer: Design issues, Data compression techniques, cryptography Application Layer: Application Layer: File Transfer, Access and Management, Electronic mail,

Virtual Terminals


Literature I

This is a good textbook for introductory courses to networking.

The chapters include detailed yet easy to grasp explanations of the topics covered, often with figures and demonstrations.


Literature II

This is a good book both as an introduction to networking and as a reference for graduate coursework.

Good end-of-chapter questions, with text depth appropriate for a smart child or an average 2nd year CS undergrad.


Literature III

This is a book with an early emphasis on application-layer paradigms and application programming interfaces (the top layer), encouraging a hands-on experience with protocols and networking concepts, before working down the protocol stack to more abstract layers.


Literature IV

The book takes a structured approach to explaining how networks work from the inside out. It starts with an explanation of the physical layer of networking, computer hardware and transmission systems; then works its way up to network applications.

It presents key principles, then illustrates them utilizing real-world example networks that run through the entire book.


Literature V

This new networking text follows a top-down approach. The presentation begins with an explanation of the application layer, which makes it easier for students to understand how network devices work, and then, with the students fully engaged, the authors move on to discuss the other layers, ending with the physical layer.


Computer Networks

A network consists of two or more computers that are linked in order to share resources (such as printers and CDs), exchange files, or allow electronic communications.

The computers on a network may be linked through cables, telephone lines, radio waves, satellites etc.

A popular example of a computer network is the Internet, which allows millions of users to share information.


1st goal: Resource Sharing

The goal is to make all programs, equipment, and especially data available to anyone on the network without regard to the physical location of the resource and the user.

Equipment: Printers, Scanner, CD-Burners…

Information: Customer records, Product information ,inventories, financial statements, tax

information


2nd goal: A Computer network to dowith people

A second goal of setting up a computer network has to do with people rather than information or even computers. A computer network can provide a powerful communication medium among employees. Email Cooperate with other to work VoIP Videoconferencing


3rd goal: e-Commerce

A third goal for many companies is doing business electronically with other companies, especially suppliers and customers.

e-Commerce B2B: Manufacturers and its suppliers. B2C: companies and its customers.


Advantages of Computer Networks

File Sharing: Networks offer a quick and easy way to share files directly.

Resource Sharing: All computers in the network can share resources such as printers, fax machines, modems and scanners.

Communication: Those on the network can communicate with each other via e-mail, instant messages etc.

Flexible Access: Networks allow their users to access files from computers throughout the network.

Sharing of Information: Computer networks enable us to share data and information with the computers that are located geographically large distance apart.


Evolution of computer networks


Network Technologies

Classification Based on Transmission Technology Broadcast networks

Broadcast network have a single communication channel that is shared by all the machines on the network

Point-to-point networks There may exist multiple paths between a

source-destination pair and the switching nodes areto provide a switching facility that will move data fromnode to node until they reach the destination.


Network Technologies

Classification Based on Scale Local Area Network (LAN) Metropolitan Area Network (MAN) Wide Area Networks (WAN)


Local Area Network (LAN)

LAN is usually privately owned and links the devices in a single office, building or campus of up to few kilometers in size.

LANs are distinguished from other kinds of networks by three categories: their size, transmission technology and topology.

LANs are restricted in size which means that their worst-case transmission time is bounded and known in

advance. Hence is more reliable as compared to MAN and WAN. Knowing this bound makes it possible to use certain kinds of design that would not otherwise be possible. It also simplifies network management.

LAN typically uses transmission technology consisting of single cable to which all machines are connected. Traditional LANs run at speeds of 10 to 100 Mbps (but now much higher speeds can

be achieved). The most common LAN topologies are bus, ring and star.


Local Area Network (LAN)


Metropolitan Area Networks (MAN)

MAN is designed to extend over the entire city. It may be a single network as a cable TV network or it may be means of connecting a

number of LANs into a larger network so that resources may be shared. MAN is wholly owned and operated by a private company or may be a service

provided by a public company.

The main reason for distinguishing MANs as a special category is that a standard has been adopted for them. It is DQDB (Distributed Queue Dual Bus) or IEEE 802.6.


Metropolitan Area Networks (MAN)


Wide Area Network (WAN)

WAN provides long-distance transmission of data, voice, image and information over large geographical areas that may comprise a country, continent or even the whole world.

WANs may utilize public, leased or private communication devices, usually in combinations, and can therefore span an unlimited number of miles.

A WAN that is wholly owned and used by a single company is often referred to as enterprise network.


Wide Area Network (WAN)


Internet – network of networks

Internet is a collection of networks or network of networks. The basic difference between WAN and Internet is that WAN is owned by a single

organization while internet is not so.


Personal Area Network (PAN)

PAN is a computer network used for communication among computer devices, including telephones and personal digital assistants, in proximity to an individual's body.

The devices may or may not belong to the person in question.

The reach of a PAN is typically a few meters.


Personal Area Network (PAN)


Classification by scale


Network Computing Models

Centralized Computing (Client-Server Network)

A client-server network is where every client is connected to the server . Server or mainframe computer has huge storage and processing capabilities.


Network Computing Models

Distributed Computing (Peer-to-Peer Network)

All devices have same power. It interconnects one or more computers. Centralized backup is not possible.


Simultaneous Access

Shared Peripheral Devices

Personal Communication

Easier Backup

Uses of Computer Network


Home Applications Access to remote information

Web Person-to-person communication

Email, VoIP e-commerce Interactive entertainment

IPTV, Gaming E-mail P2P - Peer to Peer Other applications

Ubiquitous computing IoT ( Internet of Things)

Sensor Networks RFID (Radio Frequency IDentification)

Mobile Users SoLoMo

Applications of networks


Every Network Includes:

1. At least two computers that have something to share.

2. A cable or wireless pathway, called Transmission Media, for computers to signal each other.

3. Rules, called Protocols, so that computers can use the unified principle of data communication.

4. Networking Interface Cards (NIC)


Protocol Stack

Why Layered architecture?

1. To make the design process easy by breaking unmanageable tasks into several smaller and manageable tasks (by divide-and-conquer approach).

2. Modularity and clear interfaces, so as to provide comparability between the different providers' components.

3. Ensure independence of layers, so that implementation of each layer can be changed or modified without affecting other layers.

4. Each layer can be analyzed and tested independently of all other layers.


Open System Interconnection (OSI)Reference Model

Developed by International Organization for Standardization (ISO) in 1984


Terminologies

A protocol is a formal set of rules and conventions that governs how computers exchange

information over a network medium.

the service user, the service provider, and the service access point (SAP)


Interaction between OSI Model Layers


Analogy of Protocol Hierarchies: The philosopher-translator-secretary architecture


Virtual Communication: Sino-US Talk


OSI Layers


Terminologies

Header: Upper layer puts a header in front of the message to identify the message and

passes the result to lower layer The header includes control information such as sequence numbers to keep the

right order. Size of messages

There is always a limit to the size of messages imposed by certain layer protocol. So incoming messages must be broken into smaller units (packets) in this layer.


Information Flow


Example: Path of a Web page request & Encapsulation


An Exchange Using the OSI Model


Physical Layer


Physical Layer

Purpose Transmits raw bits across a medium.

Concerns are Voltage: how many volts for 1 / 0 Timing: how many ns a bit lasts Duplexing: transmission in both directions? Connectors: how many pins? What is each pin? etc.


Data Link Layer


Data Link Layer

Purpose: Transform a raw transmission line into a line that appears free of undetected

transmission errors to the networks layer Concerns:

Framing - Breaks apart input data into frames and transmit the frames sequentially. Error handling – if the service is reliable, the receiver confirms correct receipt of

each frame by sending back an acknowledgement frame. Flow control - keeps a fast transmitter from drowning a slow receiver in data. Medium Access Control – how to control access to the shared channel for broadcast

networks.


Data Link Layer Example


Network Layer


Network Layer

Purpose Route packets from source to destination

Concerns Routing - What path is followed by packets from source to destination. Can be

based on a static table, can be determined when the connection is created, or can be highly dynamic, being determined anew for each packet, to reflect the current network load.

Congestion - Controls the number packets in the subnet. QoS – Quality of Service provided (delay, transit time, jitter…) Heterogeneity - Interfacing so that one type of network can talk to another.

Addressing, packet size, protocols…


12 Jan


Transport Layer


Transport Layer

Purpose Accept data from above it, split it up into smaller units if need be, pass them to

network layer, and ensure that the pieces all arrive correctly at the other end. Concerns

Service Decisions - What type of service to provide; error-free point to point, datagram, etc.

End-to-end: it carries data all the way from the source to the destination. Reliability - Ensures that packets arrive at their destination. Reassembles out of

order messages. Hides network - Allows details of the network to be hidden from higher level layers. Mapping - Determines which messages belong to which connections. Flow control - keeps a fast transmitter from flooding a slow receiver.


Session Layer


Session Layer

Purpose Allow users on different machines to establish sessions between them

Concerns Dialog control - keep track of whose turn it is to transmit Token Management – prevent two parties from attempting the same critical

operation at the same time Synchronization – checkpointing long transmissions to allow them to pick up from

where they left off in the event of a crash and subsequent recovery.


Presentation Layer


Presentation Layer

Purpose Make it possible for computers with different data representations to communicate

Concerns Syntax and semantics of information transmitted. Understands the nature of the data being transmitted. Converts ASCII/EBCDIC, big

endian/little endian


Application Layer


Application Layer

contains a variety of protocols that are commonly needed by users. HTTP FTP SMTP


The TCP/IP Reference Models

Link layer Internet layer Transport layer Application layer

the key a packet-switching network based on a connectionless layer that runs across different networks.


The TCP/IP Reference Models


Comparing OSI and TCP/IP Models

Concepts central to the OSI model Services Interfaces Protocols

OSI has good definition of service, interface, and protocol as discussed before. Fits well with object oriented programming concepts. Protocols are better hidden.

The TCP/IP model did not originally distinguish between service, interface, and protocol.

With TCP/IP, the protocols came first; model was just a description of the protocols. But then the model isn't good for any other protocols.


Different philosophy

Which is first? Reference Model

vsCorresponding

protocols

Specific differences Number of layers: 7 vs. 4

Connectionless vs. connection-oriented OSI supports both in the network layer, but only Connection-oriented

communication in the transport layer TCP/IP supports only connectionless mode in the network layer but supports both

in the transport layer, giving the users a choice.


What is a Topology?

Network topologies describe the ways in which the elements of a network are mapped. They describe the physical and logical arrangement of the network nodes.

The physical topology of a network refers to the configuration of cables, computers, and other peripherals


Different Types of Topologies

Bus Topology

Star Topology

Ring Topology

Mesh Topology

Tree Topology

Hybrid Topology


Bus Topology

All the nodes (file server, workstations, and peripherals) on a bus topology are connected by one single cable.

A bus topology consists of a main run of cable with a terminator at each end. All nodes (file server, workstations, and peripherals) are connected to the linear cable.

Popular on LANs because they are inexpensive and easy to install.


Bus Topology


Bus Topology

Advantages of Bus Topology It is Cheap, easy to handle and implement. Require less cable It is best suited for small networks.

Disadvantages of Bus Topology The cable length is limited. This limits the number of stations that can be connected. This network topology can perform well only for a limited number of nodes.


Ring Topology

In a ring network, every device has exactly two neighbours for communication purposes.

All messages travel through a ring in the same direction.

A failure in any cable or device breaks the loop and can take down the entire network.

To implement a ring network we use the Token Ring technology

A token, or small data packet, is continuously passed around the network. When a device needs to transmit, it reserves the token for the next trip around, then attaches its data packet to it.


Ring Topology


Ring Topology

Advantage of Ring Topology Very orderly network where every device has access to the token and the

opportunity to transmit. Easier to Manage than a Bus Network Good Communication over long distances Handles high volume of traffic

Disadvantages of Ring Topology The failure of a single node of the network can cause the entire network to fail. The movement or changes made to network nodes affects the performance of the

entire network.


Star Topology

In a star network, each node (file server, workstations, and peripherals) is connected to a central device called a hub.

The hub takes a signal that comes from any node and passes it along to all the other nodes in the network.

Data on a star network passes through the hub, switch, or concentrator before continuing to its destination.

The hub, switch, or concentrator manages and controls all functions of the network.

The star topology reduces the chance of network failure by connecting all of the systems to a central node.


Star Topology


Star Topology

Advantages of Star Topology Easy to manage Easy to locate problems (cable/workstations) Easier to expand than a bus or ring topology. Easy to install and wire. Easy to detect faults and to remove parts.

Disadvantages of Star Topology Requires more cable length than a linear topology. If the hub or concentrator fails, nodes attached are disabled. More expensive because of the cost of the concentrators.


Tree Topology

A tree topology (hierarchical topology) can be viewed as a collection of star networks arranged in a hierarchy.

This tree has individual peripheral nodes which are required to transmit to and receive from one other only and are not required to act as repeaters or regenerators.

The tree topology arranges links and nodes into distinct hierarchies in order to allow greater control and easier troubleshooting.

This is particularly helpful for colleges, universities and schools so that each of the connect to the big network in some way.


Tree Topology


Tree Topology

Advantages of a Tree Topology Point-to-point wiring for individual segments. Supported by several hardware and software vendors. All the computers have access to the larger and their immediate networks.

Disadvantages of a Tree Topology Overall length of each segment is limited by the type of cabling used. If the backbone line breaks, the entire segment goes down. More difficult to configure and wire than other topologies.


Mesh Topology

In this topology, each node is connected to every other node in the network.

Implementing the mesh topology is expensive and difficult.

In this type of network, each node may send message to destination through multiple paths.

While the data is travelling on the Mesh Network it is automatically configured to reach the destination by taking the shortest route which means the least number of hops.


Mesh Topology


Mesh Topology

Advantage of Mesh Topology

No traffic problem as there are dedicated links. It has multiple links, so if one route is blocked then other routes can be used for

data communication. Points to point links make fault identification easy. Disadvantage of Mesh Topology There is mesh of wiring which can be difficult to manage. Installation is complex as each node is connected to every node. Cabling cost is high.


Hybrid Topology

A combination of any two or more network topologies.

A hybrid topology always accrues when two different basic network topologies are connected.

It is a mixture of above mentioned topologies. Usually, a central computer is attached with sub-controllers which in turn participate in a variety of topologies


Hybrid Topology


Hybrid Topology

Advantages of a Hybrid Topology

It is extremely flexible. It is very reliable.

Disadvantages of a Hybrid Topology

Expensive


Networking hardware includes all computers, peripherals, interface cards and other equipment needed to perform data-processing and communications within the network.

What is Networking Hardware?


Networking Hardware

Network Interface Card

Hub

Repeater

Bridge

Switch

Gateway


Network Interface Cards

Network interface cards, commonly referred to as NICs, are used to connect a PC to a network.

The NIC provides a physical connection between the networking cable and the computer's internal bus.

Different computers have different bus architectures; PCI bus master slots are most commonly found on 486/Pentium PCs and ISA expansion slots are commonly found on 386 and older PCs.

NICs come in three basic varieties: 8-bit, 16-bit, and 32-bit. The larger the number of bits that can be transferred to the NIC, the faster the NIC can transfer data to the network cable.


Network Interface Cards


Hubs

A hub joins multiple computers (or other network devices) together to form a single network.

On this network, all computers can communicate directly with each other.

The networking hub is a junction box with several ports in the back for receiving the Ethernet cables that are plugged into each computer on the LAN.


Types of Hubs

A passive hub serves simply as a passage for the data, enabling it to go from one device to another.

Intelligent hub include additional features that enables an administrator to monitor the traffic passing through the hub and to configure each port in the hub.

Switching hub, actually reads the destination address of each packet and then forwards the packet to the correct port.


Hubs


Repeater

Since a signal loses strength as it passes along a cable, it is often necessary to boost the signal with a device called a repeater.

A repeater is an electronic device that receives a signal, cleans it of unnecessary noise, regenerates it, and retransmits it at a higher power level so that the signal can cover longer distances without degradation.

A good example of the use of repeaters would be in a local area network using a star topology with unshielded twisted-pair cabling.


Repeaters


Switch

A network switch is a small hardware device that joins multiple computers together within one local area network (LAN).

Network switches appear nearly identical to network hubs, but a switch generally contains more intelligence than a hub.

Unlike hubs, network switches are capable of inspecting data packets as they are received, determining the source and destination device of each packet, and forwarding them appropriately.

Allow several users to send information over a network at the same time without slowing each other down.


Switch


Router

A device to interconnect SIMILAR networks, e.g. similar protocols and workstations and servers.

A router is an electronic device that interconnects two or more computer networks, and selectively interchanges packets of data between them.

Each data packet contains address information that a router can use to determine if the source and destination are on the same network, or if the data packet must be transferred from one network to another.


Router


Bridge

A bridge is a device that connects a local area network (LAN) to another local area network that uses the same protocol (for example, Ethernet or token ring).

The function of a bridge is to connect separate networks together. Bridges connect different networks types (such as Ethernet and Fast Ethernet) or networks of the same type.

Bridges map the Ethernet addresses of the nodes residing on each network segment and allow only necessary traffic to pass through the bridge. When a packet is received by the bridge, the bridge determines the destination and source segments.


Types of Bridges

Bridges come in three basic types:

Local bridges: Directly connect local area networks (LANs)

Remote bridges: Can be used to create a wide area network (WAN) link between LANs. Remote bridges have been replaced with routers.

Wireless bridges: Can be used to join LANs or connect remote stations to LANs.


Bridges


Gateway

Gateways are used to interconnect two different networks having different protocols.

Networks using different protocols use different addressing formats.

A gateway is a network point that acts as an entrance to another network.

Gateways are also called protocol converters.


Gateway


What is the difference?

Bridge: device to interconnect two LANs that use the SAME logical link control protocol but may use different medium access control protocols.

Router: device to interconnect SIMILAR networks, e.g. similar protocols and workstations and servers.

Gateway: device to interconnect DISSIMILAR protocols and servers, and Macintosh and IBM LANs and equipment


Computer Engineering and Applications

Thank you.

Computer Networks

Dr. Manas Kumar Mishra

[email protected]

06.01.2016

computer network complete introduction

Education