UDP: (USER DATAGRAM PROTOCOL) ::

User Datagram Protocol (UDP) User Datagram Protocol (UDP) is a connection less transport layer protocol (Layer 4) that are on the internet protocol family.

 UDP is basically an interface between IP and upper layer processes. UDP protocol ports distinguish multiple applications running on a device from each other. Unlike TCP, UDP adds no reliability, flow control, or error-recovery functions to IP. Because UDP's simplicity, UDP headers contain fewer bytes and consume less network overhead than TCP.

 UDP is useful in situations where the reliability mechanisms of TCP are not necessary, as when a higher layer protocol can error and flow control condition. UDP is the transport protocol for several well-known-application protocol layers, including Network File System (NFS), Simple Network Management Protocol (SNMP), Domain Name System (DNS) and Trivial File Transfer Protocol (TFTP).

UDP packet format contains four fields, This includes areas of source and destination ports, length and checksum.

TCP (TRANSMISSION CONTROL PROTOCOL) ::

TCP provides reliable transmission of data in an IP environment. Corresponding TCP transport layer (layer 4) of the OSI reference model. Among the services TCP provides are stream data transfer, reliability, efficient flow control, dual full cooperation and multiplexing. With stream data transfer, TCP delivers an unstructured stream of bytes identified by serial numbers.

This service benefits applications because they have no data to cover the blocks before handing it to TCP. Instead, TCP groups bytes into segments and passes them to IP for delivery. TCP offers reliability by providing connection-oriented, providing end-to-end reliable packet through an Internetwork.

 It does this by sequencing bytes sent acquaintance with a number indicating the next byte source destination expects to receive. Bytes not acknowledged within a certain period is retransmitted. Reliability mechanism of TCP allows devices to deal with lost, delayed, duplicate or incorrect packages.

A timeout mechanism allows the equipment lost packets and retransmission request to discover. TCP offers efficient flow control, which means that when sending acknowledgments back to the source, receiving TCP process indicates the highest sequence number can receive without overflowing its internal buffers.

 full duplex operation means that TCP processes can both send and receive at the same time. Finally, TCP multiplexing means that the multiple simultaneous high-level talks may be multiplexed over a single connection.

ICMP PACKET::

ICMPs generate different kinds of useful messages, including destination unreachable, Echo Request and Response Redirect, Time exceeded, and Router Advertisement and Router Soloists. If an ICMP message can not be saved, there is a second is created. It is an endless stream of ICMP messages are avoided.

When a message ICMP destination-unreachable is sent by a router, this means that the router is not able to send packets to the final destination. Router then throw the original package. There are two reasons why an unreachable destination will be. More broadly, the host resource specified a nonexistent address. Less commonly, the router does not have a route to the destination.

 Destination-unreachable messages consists of four basic types: network unreachable, host unreachable, protocol unreachable, and port unreachable. Network-unreachable messages usually mean that a failure has occurred in the course or treatment of a package.

 Host-unreachable messages usually indicate liver failure, such as incorrect subnet mask. Protocol-unreachable messages generally mean that the destination does not support upper layer protocol packets.

Port-unreachable messages means that the TCP socket or port is not available. An ICMP echo request message, which was created ping command is sent from a host is required to achieve test on a job site. ICMP echo-reply message indicates that the node can be achieved successfully. ICMP Redirect message is sent from router to source host to stimulate more efficient routing.

 The router still forwards the original packet to the destination. ICMP redirects allow host routing tables remain small, it is necessary to address only a router to know, even if the router is not the best way. Even after an ICMP Redirect message, some devices can continue with the road less efficient...

ARP (ADDRESS RESOLUTION PROTOCOL) ::

Address Resolution Protocol (ARP)::

 Summary For two machines in a data network to communicate, they know another physical machine (orMAC) addresses. By broadcasting Address Resolution Protocols (ARP), a host can dynamically discover the MAC layer address corresponding to a network layer address IP.

 Upon receipt of AMAC-layer address, IP devices create an ARP amount of recently acquired IP-to-MAC address mapping store, and in this way Arps broadcast when they want a device to recontact. If the device within a specified time, the cache entry flushed.

 In addition to Reverse Address Resolution Protocol (RARP) is used for layers mapMAC addresses IP addresses. RARP, which is the logical inverse of ARP, can be used by diskless workstations that are not their IP addresses to know when their boat.

 RARP relies on the presence of a RARP server with an entry MAC address table mappings-layer-to-IP.

IP SUBNET:

IP Subnet address ::

IP networks can be divided into smaller networks called subnetworks (or subnets). Subnet provides the network administrator with several benefits, including extra flexibility, more efficient use of network addresses, and the ability to broadcast traffic (a broadcast will not cross a router) have.
 Subnets are under local administration.

As such, the outside world sees an organization as a single network and have no detailed knowledge of the organization's internal structure. A given network address can be broken up into many subnetworks.

For example, 172.16.1.0, 172.16.2.0, 172.16.3.0 and 172.16.4.0 are all subnets within network 171.16.0.0. (All 0s in host portion of an address specify the network.)