You can say, that somehow everything you do on the Internet is a matter of packets, and to be more precise, of IP packets. For example, all the Web pages that you receive on your computer, come in a variety of packages, and all the emails you send are also transmitted in packets. The networks that transfer data for all sites in small packets are called packet switched networks. On Internet, the network part of an e-mail in parts of a certain size are called bytes. This is what we call packages. Each packet carries the information that will help you reach your destination – basically the IP address of the sender of the packet, the IP that must receive, something to tell the network how many packets have left in the message, and the number of each particular package.
The packet carries data using Internet protocols, which is TCP / IP ( Transmission Control Protocol / Internet Protocol ). Each packet contains part of the message body. Typically, a package usually takes about 1500 bytes.
Each packet is then sent to its destination via the best available route – a route that can be taken by the other packets of the message or any message packets. This makes the network more efficient. For starters, the network can balance the load of several facilities within milliseconds. Second, if there is a problem with one or more computers as the message is being transferred, packets can be routed to alternative sites, ensuring complete delivery of the message.
Depending on the type of network, packets can be referred by various names, such as frames, blocks, cells or segments. However, in most packages, whatever type they may be, there are three distinct parts:
Header – The header contains instructions on data that is carried in the packet.
These instructions may include:
- Packet size (some networks have a specific size packages, while others rely on the header to carry information.
- Synchronization, which is a few bytes out package that allows an order online.
- The packet number that identifies each packet within a sequence.
- Protocol: In networks carrying multiple types of information, the protocol defines the type of packet is transmitted: emails, Web pages, video streams, etc.
- Destination address, which is where the package is.
- Source address, which is where the packet came from.
Load or Payload – is also called the body or packet data. This is the data that the packet is carrying from one place to another. If a package is of a “fixed” size, ie smaller than the standard size with which travels across the network, then you must add a filler to reach the correct size.
The tail – usually contains a few bits that tell the receiving device that has reached the end of the package. Normally it takes a check for errors. The most common method is used in packet is CRC ( Cyclic Redundancy Check ).
Usually it works as follows: Take the sum of all 1s in loading and linking. The result is stored as a hexadecimal value in the queue. The receiving device adds these 1s in the payload and compares the result to the value stored in the queue. If the value matches, the packet is good. But if the value does not match, the receiving device sends a request to the source device to forward the packet.
To give us an idea of how they interact routers with IP packets, we should think of it this way: Each packet contains protocols, source and destination addresses, and the packet number is. The routers in the network will look at the destination address in the header and compare it to a routing table that stores, to find out where to send the packet. Once the packet arrives at its destination, such as a computer, the TCP / IP stack team will remove the header and order each packet assembling the message based on the sequence numbers in each packet.