Packets

On the Internet, a typical packet length is about one kilobyte, or a thousand characters.

A large message may be divided into thousands of individual packets.

The beginning of an packet is called the "header" and records the following information:

* Source. The IP address of the computer sending the packet.

* Destination. The IP address of the destination computer .

* Length. The length of the packet in bytes.

* Number. The total number of packets in the complete message.

* Sequence. The number of this packet in the whole list of packets making up this communication.

This data provides the information an Internet router needs to get packets and messages to their destination.

For example, a destination computer can request the retransmission of missing packets, since it knows the

number of total packets and therefore can figure out which ones it doesn't have.