Computer networks unit 1 basic networking concepts

Computer networks fundamental networking concept

1. UNIT I - INTRODUCTION AND PHYSICAL LAYER

2. INTRODUCTION TO NETWORKS A network is a set of devices (often referred to as nodes) connected by communication links. A node can be a computer, printer, or any other device capable of sending or receiving data generated by other nodes on the network. When we communicate, we are sharing information. This sharing can be local or remote .

3. CHARACTERISTICS OF A NETWORK Delivery Accuracy Timeliness

4. COMPONENTS INVOLVED IN A NETWORK PROCESS

5. KEY ELEMENTS OF PROTOCOL Syntax Semantics Timing

6. TRANSMISSION MODES The way in which data is transmitted from one device to another device is known as transmission mode . The transmission mode is also known as the communication mode. Each communication channel has a direction associated with it, and transmission media provide the direction. Therefore, the transmission mode is also known as a directional mode . The transmission mode is defined in the physical layer.

7. Types of Transmission mode

8. SIMPLEX MODE

9. HALF-DUPLEX MODE

10. FULL-DUPLEX MODE

11. COMPARISON - SIMPLEX, HALF-DUPLEX AND FULL-DUPLEX MODE

12. LINE CONFIGURATION / LINE CONNECTIVITY Line configuration refers to the way two or more communication devices attach to a link. A link is a communications pathway that transfers data from one device to another . There are two possible line configurations : Point to Point (PPP ) MultiPoint

13. Point to Point (PPP)

14. MultiPoint It is also called Multidrop configuration. In this connection two or more devices share a single link. There are two kinds of Multipoint Connections . Spatial Sharing Temporal (Time) Sharing

15. NETWORK TYPES A computer network is a group of computers linked to each other that enables the computer to communicate with another computer and share their resources, data, and applications . A computer network can be categorized by their size. A computer network is mainly of three types: 1. Local Area Network (LAN) 2. Wide Area Network (WAN) 3. Metropolitan Area Network (MAN )

16. LOCAL AREA NETWORK (LAN)

17. WIDE AREA NETWORK (WAN )

18. METROPOLITAN AREA NETWORK (MAN)

19. INTERNETWORK An internetwork is defined as two or more computer network LANs or WAN. An Internetwork can be formed by joining two or more individual networks by means of various devices such as routers, gateways and bridges. An interconnection between public, private, commercial,industrial , or government computer networks can also be defined as internetworking

20. PROTOCOL LAYERING In networking, a protocol defines the rules that both the sender and receiver and all intermediate devices need to follow to be able to communicate effectively . A protocol provides a communication service that the process uses to exchange messages. When communication is simple, we may need only one simple protocol.

21. Basic Elements of Layered Architecture Service. Protocol Interface

22. PROTOCOL LAYERING Features of Protocol Layering 1. It decomposes the problem of building a network into more manageable components. 2. It provides a more modular design . Principles of Protocol Layering 1. The first principle dictates that if we want bidirectional communication, we need to make each layer so that it is able to perform two opposite tasks, one in each direction. 2. The second principle that we need to follow in protocol layering is that the two objects under each layer at both sites should be identical.

23. Protocol Graph Protocol Graph The set of protocols that make up a network system is called a protocol graph . The nodes of the graph correspond to protocols, and the edges represent a dependence relation. A protocol graph consists of protocols RRP (Request/Reply Protocol) and MSP (Message Stream Protocol) implement two different types of process-to-process channels, and both depend on the HHP (Host-to- Host Protocol) which provides a host-to-host connectivity service

24. OSI MODEL OSI stands for Open System Interconnection. It is a reference model that describes how information from a software applicationin one computer moves through a physical medium to the software application in another computer. OSI consists of seven layers, and each layer performs a particular network function. OSI model was developed by the International Organization for Standardization (ISO) in 1984, and it is now considered as an architectural model for the inter- computer communications. OSI model divides the whole task into seven smaller and manageable tasks. Each layer is assigned a particular task. Each layer is self-contained, so that task assigned to each layer can be performed independently

25. OSI stands for Open System Interconnection. It is a reference model that describes how information from a software application in one computer moves through a physical medium to the software application in another computer. OSI consists of seven layers, and each layer performs a particular network function. OSI model was developed by the International Organization for Standardization (ISO) in 1984, and it is now considered as an architectural model for the inter- computer communications. OSI model divides the whole task into seven smaller and manageable tasks. Each layer is assigned a particular task. Each layer is self-contained, so that task assigned to each layer can be performed independently

26. ORGANIZATION OF THE OSI LAYERS

27. FUNCTIONS OF THE OSI LAYERS 1 . PHYSICAL LAYER The physical layer coordinates the functions required to transmit a bit stream over a physical medium. The physical layer is concerned with the following functions: Physical characteristics of interfaces and media Representation of bits Signals Data Rate or Transmission rate Synchronization of bits Line Configuration Physical Topology Transmission Mode

28. DATA LINK LAYER It is responsible for transmitting frames from one node to the next node. The other responsibilities of this layer are Framing Physical addressing Flow control Error control Medium Access control

29. NETWORK LAYER This layer is responsible for the delivery of packets from source to destination. It determines the best path to move data from source to the destination based on the network conditions, the priority of service, and other factors. The other responsibilities of this layer are Logical addressing Routing

30. TRANSPORT LAYER It is responsible for Process to Process delivery. That is responsible for source-to destination (end-to-end) delivery of the entire message, It also ensures whether the message arrives in order or not. The other responsibilities of this layer are Port addressing / Service Point addressing Segmentation and reassembly Connection control Flow control Error Control

31. SESSION LAYER This layer establishes, manages and terminates connections between applications. The other responsibilities of this layer are: Dialog control Synchronization

32. PRESENTATION LAYER It is concerned with the syntax and semantics of information exchanged between two systems. The other responsibilities of this layer are: Translation Encryption and decryption Compression and expansion

33. APPLICATION LAYER This layer enables the user to access the network. It handles issues such as network transparency, resource allocation, etc. This allows the user to log on to remote user. The other responsibilities of this layer are: FTAM (File Transfer, Access, Management) Mail services Directory services

34. TCP / IP PROTOCOL SUITE The TCP/IP architecture is also called as Internet architecture. It is developed by the US Defense Advanced Research Project Agency (DARPA) for its packet switched network (ARPANET). TCP/IP is a protocol suite used in the Internet today. It is a 4-layer model. The layers of TCP/IP are 1. Application layer 2. Transport Layer (TCP/UDP) 3. Internet Layer 4. Network Interface Layer

35. COMPARISON - OSI MODEL AND TCP/IP MODEL

36. HTTP (HYPERTEXT TRANSFER PROTOCOL) The Hyper Text Transfer Protocol (HTTP) is used to define how the client server programs can be written to retrieve web pages from the Web. It is a protocol used to access the data on the World Wide Web (WWW). The HTTP protocol can be used to transfer the data in the form of plain text, hypertext, audio, video, and so on. HTTP is a stateless request/response protocol that governs client/server communication.

37. Features of HTTP Connectionless protocol Media independent Stateless

38. HTTP REQUEST AND RESPONSE MESSAGES

39. HTTP REQUEST MESSAGE:

40. Request Line

41. Request Header

42. HTTP RESPONSE MESSAGE

43. Status Line

44. Response Header

45. HTTP CONNECTIONS HTTP Clients and Servers exchange multiple messages over the same TCP connection. If some of the objects are located on the same server, we have two choices: to retrieve each object using a new TCP connection or to make a TCP connection and retrieve them all. The first method is referred to as a non-persistent connection,the second as a persistent connection. HTTP 1.0 uses non-persistent connections and HTTP 1.1 uses persistent connections

46. NON-PERSISTENT CONNECTIONS

47. PERSISTENT CONNECTIONS

48. HTTP COOKIES An HTTP cookie (also called web cookie, Internet cookie, browser cookie, or simply cookie) is a small piece of data sent from a website and stored on the user's computer by the user's web browser while the user is browsing.

49. SOCKETS A socket is one endpoint of a two-way communication link between two programs running on the network. The socket mechanism provides a means of inter-process communication (IPC) by establishing named contact points between which the communication take place.

50. The socket provides bidirectional FIFO Communication facility over the network . Each socket has a specific address. This address is composed of an IP address and a port number .

51. Socket Addresses Local (sender) R emote (receiver ) A socket address should first define the computer on which a client or a server is running . A socket address should be a combination of an IP address and a port number.

52. Types of Sockets Datagram Socket Stream Socket

53. FTP (FILE TRANSFER PROTOCOL) FTP is a standard internet protocol provided by TCP/IP used for transmitting the files from one host to another. It is mainly used for transferring the web page files from their creator to the computer that acts as a server for other computers on the internet. It is also used for downloading the files to computer from other servers. Although we can transfer files using HTTP, FTP is a better choice to transfer large files or to transfer files using different formats.

54. FTP MECHANISM

55. FTP CONNECTIONS

56. FTP COMMUNICATION