Tag - Ip Protocols

Application Layer

Application Layer enable the user, whether human or software, to access the network. It provides user interfaces and support for services such as electronic mail,file access and transfer, access to system resource, surfing the world wide web, and network management.

Application layer is Responsible for Providing Services to the user.

  • Application Layer is a term used in categorizing protocols and methods in architectural models of computer networking. Both the OSI model and the Internet Protocol Suite (TCP/IP) define application layers.
  • In TCP/IP, the Application Layer contains all protocols and methods that fall into the realm of process-to-process communications via an Internet Protocol (IP) network using the Transport Layer protocols to establish underlying host-to-host connections.
  • Provides a means for the user to access information on the network through an application. This layer is the main interface for the user to interact with the application and therefore the network.
  • The application layer is the OSI layer closest to the end user, which means that both the OSI application layer and the user interact directly with the software application. This layer interacts with software applications that implement a communicating component. Such application programs fall outside the scope of the OSI model. Application layer functions typically include identifying communication partners, determining resource availability, and synchronizing communication. When identifying communication partners, the application layer determines the identity and availability of communication partners for an application with data to transmit. When determining resource availability, the application layer must decide whether sufficient network resources for the requested communication exist. In synchronizing communication, all communication between applications requires cooperation that is managed by the application layer.


Some examples of application layer implementations include Telnet, File Transfer Protocol (FTP), and Simple Mail Transfer Protocol (SMTP).

 OSI  Model


  • Application Layer do¬†Interaction (Providing Services to the user)
  • 80% Application on internet do interact
  • i.e ¬†google.com —–> will auto —–> ¬†www.google.com ——> Here www intract ¬†on port 80
  • i.e ¬†for buy house property dealer do interact

Application Layer Protocols

IP Addressing

IP address is a unique identifier of a computer on TCP/IP networks and on the internet.  Every computer requires a unique IP address to be a part of the internet and the IP address is provided by the internet service providers.  Every IP address consists of the 32 bits and a binary system of 0s and 1s.  The binary number system consist of only two types of digits 0 and 1. It is easier for us to remember the decimal numbers rather than the binary number system such as 011001101. On a same network segment, all the IP address share the same network address.

There are five classes of the IP addresses such as A, B, C, D and E and only 3 classes are in the use. Class D IP addresses are reserved for the multicast group ant cannot be assigned to hosts and the E class IP addresses are the experimental addresses and cannot be assigned to the people. Every IP address consists of 4 octets and 32 bits.  Every participating host and the devices on a network such as servers, routers, switches, DNS, DHCP, gateway, web server, internet fax server and printer have their own unique addresses within the scope of the network.

TCP/IP protocols are installed by default with the Windows based operating systems. After the TCP/IP protocols are successfully installed you need to configure them through the Properties Tab of the Local Area Connection.

IP Addresses Classes

Class A

The binary address for the class A starts with 0. The range of the IP addresses in the class A is between 1 to 126 and the default subnet mask of the class A is  Class A supports 16 million hosts on each of 125 networks.  An example of the class A is  Class A is used for the large networks with many network devices.

Class B

The binary address for the class B starts with 10. The range of the IP address in the class B is between 128 to 191 and the default subnet mast for the class B is  Class B supports 65,000 on each of 16,000 networks. An example of the class B address is  Class B addresses scheme is used for the medium sized networks.

Class C

The binary address for the class C starts with 110. The range of the IP addresses in the class C is between 192 to 223 and the default subnet mask for the class C is 255.255.255.  Class C hosts 254 hosts on each of 2 million networks.  An example of the Class C IP address is  Class C is used for the small networks with less then 256 devices and nodes in a network.

Class D

The binary addresses for the class D starts with 1110 and the IP addresses range can be between 224 to 239.  An example of the class D IP address is

Class E

The binary address can starts with 1111 and the decimal can be anywhere from 240 to 255.  An example of the class E IP address is

It is very important to know that all the computers in the same network segment should have the IP addresses for the same class i.e. form A, B or C

IP Addressing

IP Addressing Tips 

  • A Network ID cannot be All 0s
  • A host ID cannot be All 1 because this represents a broadcast address for the local network.
  • Each host must have a unique host portion of the IP address.
  • All hosts on the same network segment should have the same network id.
  • A host address cannot be 127 because 127 has been reserved for the loop back functionalities.

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