Computer Network Tutorial

Introduction of Computer Network Types of Computer Network Network Topology Computer Networking Architecture Transmission Modes (Data Flow) Basic Networking Devices Integrate Services Digital Network (ISDN)

Model

OSI Model TCP/IP Model

Physical Layer

Digital Transmission Analog Transmission Transmission Media Switching

Data Link Layer

Error detection and Error correction Data Link Control Multiple Access Aloha

Network Layer

Network Layer - Logical Address Address Mapping Unicast Routing Protocol

Transport Layer

Process to Process Delivery User Datagram Protocol Transmission Control Protocol Stream Control Transmission Protocol Session Layer and Presentation Layer

Application Layer

Domain Name System Application Protocol E-mail Cryptography

Misc

Classes of Routing Protocols Classification of Routing Algorithms Controlled Access Protocols in Computer Networks Differences between IPv4 and IPv6 Fixed and Flooding Routing Algorithms Advantages and Disadvantages of Fibre Optics Cable APIPA Difference between Active and Passive FTP Fiber Optics and its Types Method of Joining and Fusion of Fiber Optic Cable Define Framing in Computer Network Disadvantages of Computer Network Mesh Topology Diagram in Computer Network Ring Topology in Computer Network Star Topology in Computer Networks 4G Mobile Communication Technology Advantages and Disadvantages of LAN Advantages and Disadvantages of MAN Advantages and Disadvantages of WAN Application Layer in OSI Model Cyclic Redundancy Check Example Data link layer in OSI model Difference between Transport and Network Layer Hamming Code Example Network Layer in OSI Model Session Layer in OSI Model Transport Layer in OSI Model Two Port Network in Computer Networks Uses of Computer Networks What is Computer Network What is Framing in a Computer Network Advantages and Disadvantages of Bus Topology Difference between Star Topology and Bus Topology Subnetting in Computer Network Subnetting Questions and Answers What is Bus Topology What is Network Topology and Types in Computer Networks Access Control in Networking Basic Characteristics of Computer Network Benefits of SOCKS5 Proxy in Computer Networks Computer Network viva Questions Difference between BOOTP and RARP Difference Between Network Topologies and Network Protocols Difference between NFC and RFID Difference Between Point-to-Point Link and star Topology Network Differences Between MSS and MTU Differences Between Trunk Port and Access Port Different Modes of Communication in Computer Networks MIME Protocol in Computer Networks Modes of Communication in Computer Networks Network Attack in Computer Network Port Address in Networking Simplest Protocol in Computer Network Sliding Window Protocol in Computer Network Stop And Wait Protocol in Computer Networks TCP 3-Way Handshake Process in Computer Networks What is a Proxy Server What is APPN What is ICMP Protocol What is Point-to-Point Protocol What is Port Address in Networking What is the HDLC Protocol What is VRRP Protocol Difference Between Analog and Digital Signals Difference Between Hub and Repeater Difference between Repeater and Switch Difference Between Transparent Bridge and Source Routing Bridge Source Routing Bridge in Computer Networks Transparent Bridge in Computer Networks Transport Protocol in Computer Networks Types of CSMA in Computer Networks What is Wired and Wireless Networking Network Security in Computer Network Disadvantages of Extranet Difference Between TELNET and FTP Define Protocol in Computer Networks Guided Transmission Media in Computer Network What is a Gateway in a Computer Network IGMP in Computer Networks LAN Protocols in Computer Networks MAN Meaning in Computer Modulation Techniques in Computer Networks Switching in DCN TCP/IP Applications What is IGMP? What is Modem in Networking What is Non-Persistent CSMA Difference between Cell Splitting and Cell Sectoring Forouzen Computer Network Open Loop and Closed Loop Congestion Control Types of Cluster Computing WAP-Wireless Access Point What are the elements of the Transport Protocol Difference between Gateway and Switch Flow Control in Data Link Layer Body Area Network Flooding in Computer Network Token Ring in Computer Networks VoIP in Computer Networks What is Infrared Transmission Congestion Control Techniques Forward Error Correction (FEC) Switching Techniques What is Telnet in Computer Network What are the Types of IPv4 Addresses IEEE 802.6 (DQDB) IEEE 802.15.4 Technology What is HDLC (High-level Data Link Control)? What is SMS Hubbing in Telecom? Circuit Switching in Computer Networks Communication Satellites in Computer Networks Features of HTTP Protocol IMAP4 (Internet Message Access Protocol) Internet Services How to Set up a Wireless Router Internetwork Routing in Computer Networks Distributed Computing System Features of GSM The 802.11 MAC Sublayer Protocol What is IEEE 802.3? What are Hubs and Switches in Computer Networks? What is Modem in a Computer Network? What is multicasting in Computer Networks? GSM -The Mobile Station What is Network Server? Slotted Aloha in Computer Network What is Ethernet in Computer Networks What is Arpanet? Radio Access Network (RAN) TCP 3-Way Handshake Process PING SWEEP (ICMP SWEEP) Print Server Private IP Address Security Services in Computer Networks Protocol Data Unit (PDU) CSMA with Collision Avoidance (CSMA/CA) What is Gateway in Computer Network? Advantages of Networking Data Link Layer Design Issues DHCP in Computer Networks Internet Security Association and Key Management Protocol (ISAKMP) What is Switch Hub? Telnet Full form in Networking Multimedia Systems Quality of Service in Computer Networks What is Carrier Sense Multiple Access (CSMA)? What is Circuit Switching What is Duplex Network? What is Web Protocol Network LAN Technologies Classes in Computer Network Low-Density Parity Check (LDPC) Wireless Internet Service Providers(Wisps) What is Handshaking? Cache Server What Is WSN Network? Check Sum Error Detection Linear Bus Topology Functions of the Transport Layer Infrared Transmission in Computer Networks Digital Signal in Computer Network Digital Data Transmission in Computer Networks Define Checksum with Example Computer Network Security Requirements Brust Errors in Computer Network Back Side Bus (BSB) 2-Dimension Parity Check in Computer Network Router and Brouter Microwave Transmission in Computer Networks Magnetic Media in Computer Network A One-Bit Sliding Window Protocol CDMA-Near-Far Problem Reference Models in Computer Networks Uni-cast, Broadcast, and Multicast in Computer Networks Uses Of Bridges in Computer Networks What are Gateways in Computer Network?

Application Layer in OSI Model

This article will help you in getting a better understanding of the Application layer in the OSI model.

It is the uppermost layer in the OSI Model. The application layer establishes the interaction/communication between the end user and the software application.The application layer allows users to send and access the data and provides connectivity with the network.

As it is the last layer it depends on all the layers for the completion of a process. The application layer displays the data. It is not an application, instead, it is a component of an application that resides within the application. It is an abstraction layer that displays only the outer structure and hides the inner structure(code of application) from the user. It displays the data in a human-understandable format.

Functionalities of the Application Layer

  1. Mail services: Application layer provides basic mail services like sending, receiving, and forwarding mail. It provides a storage facility for mail.
  2. Determining resource availability: Application layer provides or determines the availability of requested resources for carrying out a specific communication. Here resources may refer to any input/output devices like printers, etc., or for access to main memory. 
  3. Addressing: Addressing is very crucial in establishing the communication between the client and server. When clients send a request to the server the request carries both server and its address. The response of the server (to the client’s request) consists of the destination address(client address). DNS(Domain Name System) protocol is used for carrying out the addressing process.
  4. Synchronizing communication: Synchronization is a process of adding multiple checkpoints in the communication process. If there is any interruption or any failure during the process, then the process will continue to run from the last saved checkpoint rather than repeating the process from the initial stage. All the communications between various applications are properly synchronized with the help of the Application layer.
  5. File transfer Access and Management (FTAM): This procedure is mainly applicable for remote computers so that users can manage, and retrieve various files from a remote computer. FTAM stores file structure, file attributes, etc in a virtual hierarchical manner.
  6. Identifying communication partners:  The application layer determines whether the communication partners are available or not for data transfer by an application.
  7. Network Virtual terminal: A user log onto a remote host with the help of the Application Layer to create a software emulation terminal at a remote host. The user’s computer interacts with the software terminal and interacts with the host. But the remote host assumes that it is interacting with its terminal and it allows the user to get logged in.

Working of Application Layer

The application layer acts as an interface between a user and a software application. The client sends a request to the server, and the server acknowledges the client that the connection is established by setting up the Acknowledgement(ACK) Flag to 1. As soon as the client receives the acknowledgment from the server, the client can access the server and can store and retrieve data from the server.

Application Layer Protocols

Following are the various protocols used by the application layer in the Open Systems Interconnection (OSI) Model:

1. FTP (File Transfer Protocol):

FTP stands for File Transfer Protocol. This protocol is used for sending various files from one device to another device. This transfer of files is done with the help of remote computer devices. 20 port number is used for accessing the data and 21 port number is used to handle the data.

2. SMTP (Simple Mail Transfer Protocol):

SMTP stands for Simple Mail Transfer Protocol. This protocol is used for delivering mails from one device to another device. Simple Mail Transfer Protocol is mainly used by the end-users and this protocol utilizes the 25 and 587 port numbers.

3. HTTP (Hyper Text Transfer Protocol):

HTTP abbreviates Hyper Text Transfer Protocol. This protocol’s functioning is based on the client-server model. This protocol is used to transfer various types of data like photos, text, hypertext, or other hypermedia documents into the WWW(World wide web).

Hyper Text Transfer Protocol is mainly used in establishing the communication between web browsers and web servers. It acts as a basic foundation for WWW. It utilizes 80 port number.

4. DNS (Domain Name Search):

DNS abbreviates Domain Name Search. This protocol uses the Domain Name into its equivalent IP address. For example, if a user selects www.xyz.com then it converts it into its equivalent IP address i.e., 192.23.45.63(it is a random IP address that is mentioned just for understanding purposes). This protocol utilizes 53 port number.