Importance of the Internet Protocol (IP)

Importance of the Internet Protocol (IP)

For hosts to communicate on the Internet, they must be running Internet Protocol (IP) software. The IP protocol is one of a group of protocols that are collectively referred to as TCP/IP (Transmission Control Protocol / Internet Protocol). The Internet Protocol (IP) uses packets to carry data. Whether you are playing an Internet video game, chatting with a friend, sending email or searching the Web, the information you are sending or receiving is carried in the form of IP packets.

 Each IP packet must contain a valid source and destination IP address. Without valid address information, packets sent will not reach the destination host. Return packets will not make it back to the original source.

 IP defines the structure of the source and destination IP addresses. It specifies how these addresses are used in routing of packets from one host or network to another.

 All protocols that operate on the Internet, including IP, are defined in numbered standards documents called RFCs (Request for Comments).

An IP packet has a header at the beginning which contains the source and destination IP addresses. It also contains control information that describes the packet to network devices, such as routers, it passes through and also helps to control its behavior on the network. The IP packet is sometimes referred to as a datagram.

 IP addresses must be unique on the Internet. There are organizations responsible for controlling the distribution of IP addresses so that there is no duplication. ISPs obtain blocks of IP addresses from a local, national or regional Internet registry (RIR). It is the responsibly of the ISPs to manage these addresses and assign them to end users.

 Computers in homes, small businesses and other organizations obtain their IP configuration from their ISP. Typically, this configuration is obtained automatically when the user connects to the ISP for Internet access.

How ISPs Handle Packets

Before being sent on the Internet, messages are divided into packets. IP packet size is between 64 to 1500 bytes for Ethernet networks, and contains mostly user data. Downloading a single 1 MB song would require over 600 packets of 1500 bytes. Each individual packet must have a source and destination IP address.

 When a packet is sent across the Internet, the ISP determines whether the packet is destined for a local service located on the ISP network, or a remote service located on a different network.

 Every ISP has a control facility for their network, known as the Network Operations Center (NOC). The NOC usually controls traffic flow and houses services such as email and web hosting. The NOC may be located at one of the POPs or at a completely separate facility within the ISP network. Packets looking for local services are usually forwarded to the NOC and never leave the ISP network.

 Routers in each of the ISP POPs use the destination address of the IP packets to choose the best path through the Internet. The packets you send to the ISP POP are forwarded by routers through the ISP's network and then through the networks of other ISPs. They pass from router to router until they reach their final destination.

Forwarding  Packet Across the Internet

There are network utilities that test connectivity to the destination device. The ping utility tests end-to-end connectivity between source and destination. It measures the time that it takes test packets to make a round trip from the source to the destination and whether the transmission is successful. However, if the packet does not reach the destination, or if delays are encountered along the way, there is no way to determine where the problem is located.

 How is it possible to determine which routers the packets have passed through and detect the problem areas in the path?

 The traceroute utility traces the route from source to destination. Each router through which the packets travel is referred to as a hop. Traceroute displays each hop along the way and the time it takes for each one. If a problem occurs, the display of the time and the route that the packet traveled can help to determine where the packet was lost or delayed. The traceroute utility is called tracert in the Windows environment.

 There are also a number of visual traceroute programs that can provide a graphical display of the route that a packet takes.