Lesson number 2 : IP Address Notation - What Is An IP Address?

This tutorial explains the technology behind Internet Protocol (IP) networking.

Definition:

IP (Internet Protocol) is the primary network protocol used on the Internet, developed in the 1970s. On the Internet and many other networks, IP is often used together with the Transport Control Protocol (TCP) and referred to interchangeably as TCP/IP.

IP supports unique addressing for computers on a network. Most networks use the Internet Protocol version 4 (IPv4) standard that features IP addresses four bytes (32 bits) in length. The newer Internet Protocol version 6 (IPv6) standard features addresses 16 bytes (128 bits) in length.

Data on an Internet Protocol network is organized into packets. Each IP packet includes both a header (that specifies source, destination, and other information about the data) and the message data itself.

IP functions at layer 3 of the OSI model. It can therefore run on top of different data link interfaces including Ethernet and Wi-Fi.

Definition:

Transmission Control Protocol (TCP) and Internet Protocol (IP) are two distinct network protocols, technically speaking. TCP and IP are so commonly used together, however, that TCP/IP has become standard terminology to refer to either or both of the protocols.

IP corresponds to the Network layer (Layer 3) in the OSI model, whereas TCP corresponds to the Transport layer (Layer 4) in OSI. In other words, the term TCP/IP refers to network communications where the TCP transport is used to deliver data across IP networks.

The average person on the Internet works in a predominately TCP/IP environment. Web browsers, for example, use TCP/IP to communicate with Web servers.

Definition:

The OSI model defines internetworking in terms of a vertical stack of seven layers. The upper layers of the OSI model represent software that implements network services like encryption and connection management. The lower layers of the OSI model implement more primitive, hardware-oriented functions like routing, addressing, and flow control.

In the OSI model, data communication starts with the top layer at the sending side, travels down the OSI model stack to the bottom layer, then traveses the network connection to the bottom layer on the receiving side, and up its OSI model stack.

The OSI model was introduced in 1984. Although it was designed to be an abstract model, the OSI model remains a practical framework for today's key network technologies like Ethernet and protocols like IP.

Also Known As: Open Systems Interconnection (OSI) reference model, OSI seven layer model

Examples:

Internet Protocol (IP) corresponds to the Network layer of the OSI model, layer three. TCP and UDP correspond to OSI model layer four, the Transport layer. Lower layers of the OSI model are represented by technologies like Ethernet. Higher layers of the OSI model are represented by application protocols like TCP and UDP.

Definition:

A network protocol defines rules and conventions for communication between network devices. Protocols for computer networking all generally use packet switching techniques to send and receive messages in the form of packets.

Network protocols include mechanisms for devices to identify and make connections with each other, as well as formatting rules that specify how data is packaged into messages sent and received. Some protocols also support message acknowledgement and data compression designed for reliable and/or high-performance network communication. Hundreds of different computer network protocols have been developed each designed for specific purposes and environments.

Internet Protocols

The Internet Protocol family contains a set of related (and among the most widely used network protocols. Besides Internet Protocol (IP) itself, higher-level protocols like TCP, UDP, HTTP, and FTP all integrate with IP to provide additional capabilities. Similarly, lower-level Internet Protocols like ARP and ICMP also co-exist with IP. These higher level protocols interact more closely with applications like Web browsers while lower-level protocols interact with network adapters and other computer hardware.

Routing Protocols

Routing protocols are special-purpose protocols designed specifically for use by network routers on the Internet. Common routing protocols include EIGRP, OSPF and BGP.

How Network Protocols Are Implemented

Modern operating systems like Microsoft Windows contain built-in services or daemons that implement support for some network protocols. Applications like Web browsers contain software libraries that support the high level protocols necessary for that application to function. For some lower level TCP/IP and routing protocols, support is implemented in directly hardware (silicon chipsets) for improved performance.

IPv4 and IPv6

Internet Protocol (IP) technology was developed in the 1970s to support some of the first research computer networks. Today, IP has become a worldwide standard for home and business networking as well. Our network routers, Web browsers, email programs, instant messaging software - all rely on IP or other network protocols layered on top of IP.

Two versions of IP technology exist today. Traditional home computer networks use IP version 4 (IPv4), but some other networks, particularly those at educational and research institutions, have adopted the next generation IP version 6 (IPv6).

IPv4 Addressing Notation

An IPv4 address consists of four bytes (32 bits). These bytes are also known as octets.

For readability purposes, humans typically work with IP addresses in a notation called dotted decimal. This notation places periods between each of the four numbers (octets) that comprise an IP address. For example, an IP address that computers see as

00001010 00000000 00000000 00000001

is written in dotted decimal as

10.0.0.1

Because each byte contains 8 bits, each octet in an IP address ranges in value from a minimum of 0 to a maximum of 255. Therefore, the full range of IP addresses is from 0.0.0.0 through 255.255.255.255. This represents a total of 4,294,967,296 possible IP addresses.

IPv6 Addressing Notation

IP addresses change significantly with IPv6. IPv6 addresses are 16 bytes (128 bits) long rather than four bytes (32 bits). This larger size means that IPv6 supports more than

300,000,000,000,000,000,000,000,000,000,000,000,000

possible addresses! As an increasing number of cell phones and other consumer electronics expand their networking capability and require their own addresses, the smaller IPv4 address space will eventually run out and IPv6 become mandatory.

IPv6 addresses are generally written in the following form:

hhhh:hhhh:hhhh:hhhh:hhhh:hhhh:hhhh:hhhh

In this full notation, pairs of IPv6 bytes are separated by a colon and each byte in turns is represented as a pair of hexadecimal numbers, like in the following example:

E3D7:0000:0000:0000:51F4:9BC8:C0A8:6420

As shown above, IPv6 addresses commonly contain many bytes with a zero value. Shorthand notation in IPv6 removes these values from the text representation (though the bytes are still present in the actual network address) as follows:

E3D7::51F4:9BC8:C0A8:6420

Finally, many IPv6 addresses are extensions of IPv4 addresses. In these cases, the rightmost four bytes of an IPv6 address (the rightmost two byte pairs) may be rewritten in the IPv4 notation. Converting the above example to mixed notation yields

E3D7::51F4:9BC8:192.168.100.32

IPv6 addresses may be written in any of the full, shorthand or mixed notation illustrated above.

We will have our next lesson of networking soon.