The Next Generation Internet Protocol: IPv6

4.3.1 Why IPv6?

The current Internet protocol (IP) version is IPv4, which has been used for many years and also has critical limitations. Challenges faced by the current IPv4 can be summarized as follows:

Growth of the Internet. Maximum: 4 billion.

When will addresses run out? Estimates: 2005.

Single IP address for devices.

Mobile Internet

Internet services from everywhere.

Removing location dependency.

Address spaces

Security

End-to-end encryption.

Data integrity and authentication requirements for the new protocol can be described as follows:

Support billions of hosts.

Reduce size of routing tables.

Simplify protocol, process packets faster.

Provide better security (authentication & privacy).

Better QoS (particularly for real-time data).

Aid multicasting, anycasting.

Make it possible for a host to roam without changing its address.

The primary motivation for change from IPv4 to IPv6 is the limited address space.

The 32-bit IPv4 address can only include just over a million networks on the Internet. At the current growth rate, each of the possible network prefixes will soon be assigned and no further growth will be possible.

The second motivation for change comes from requirements of new applications, especially applications that require real-time delivery of audio and video data. The current IP has limited capabilities for routing real-time data.

4.3.2 IPv6 Features

IPv6 retains many design features of IPv4, e.g., it still is connectionless. However, IPv6 also has many new features. It has practically unlimited address space, optional header fields (better support for options). It also simplifies packet header, provides authentication and privacy capability to make a network more secure, and pays more attention to type of service, e.g., Plug & Play, - better configuration options, etc. The new features of IPv6 can be summarized as follows:

Address size: Instead of 32, each IPv6 address is 128 bits. The address space is large enough for many years of growth of Internet.

Header format: The IPv6 header has a complete format compared to IPv4 headers.

Extension header: Unlike IPv4, which uses a single header format for all datagrams, IPv6 encodes information into separate headers. A datagram of IPv6 contains a base header followed by 0 or more extension headers, and data.

Support for audio and video: IPv6 includes a mechanism that allows a sender and receiver to establish a high-quality path through the underlying network and to associate datagrams with that path.

Extensible protocol: Unlike IPv4, IPv6 does not specify all possible protocol features. Instead, the designers have provided a scheme that allows a sender to add additional information to a datagram. The extension makes IPv6 more flexible than IPv4.

Network management: IPv6 has auto configuration ability. It can automate network address renumbering. DHCP support is mandated, i.e., every host can download its network configurations from a server at startup time. Auto-configuration allows hosts to operate in any location without any special support.

Auto address changes: Address changes in IPv6 can also be automated. It has two ways to change an address:

Stateless: routers advertise prefixes that identify the subnet(s) associated with a link. Hosts generate an “interface token” that uniquely identifies an interface on a subnet. An address is formed by combining the above two.

Stateful: clients obtain address and/or configuration from a DHCP server.

The DHCP server maintains the database and has a tight control over address assignments.

Mobility: IPv6 was specifically designed to support mobility, which is based on core features of IPv6. Mobility is not an “Add-on” feature in IPv6. All IPv6 networks, LANs/Subnets, and nodes are mobile ready.

One of the questions in the IPv6 design is, why does IPv6 use separate extension headers? This can be explained from the following aspects:

Economy: Partitioning the datagram functionality into separate headers is economical because it saves space. Having separate headers in IPv6 makes it possible to define a large set of features without requiring each datagram header to have at least one field for each feature.

Extensibility: When adding a new feature, existing IPv6 protocol headers can remain unchanged. A new next header type can be defined as well as a new header format.

Advantage: The chief advantage of placing new functionality in a new header lies in the ability to experiment with a new feature before changing all computers on the Internet.

4.4 Summary

Network architecture can have one of two types, one is defined by the OSI reference model and the other defined by the ARPANET model. The OSI reference model has seven protocol layers each of which builds upon the services offered by the subordinate layers to offer an enhanced service to the upper layers. The current Internet architecture was built on the ARPANET model which adopts four protocol layers. The main protocols used in the Internet architecture for network communication are TCP, UDP and IP protocols. IP protocol is a network layer protocol while TCP and UDP are transport layer protocols. The current IPv4 has a critical limitation, i.e., the limited address space so that it can not meet the demands of rapid growth of Internet. The study on the next generation of Internet protocol – IPv6 has been conducted for many years and will provide many new features as well as advantages compared with IPv4.

Exercises

4.1 What is the OSI reference model? What layers does it have? 4.1.1

How do programs residing on different computers communicate with each other in the OSI model? 4.1.1

What is the difference between the OSI architecture and the Internet architecture? 4.1.2

What method is used for application programs communication with each other on the Internet? 4.1.2

Describe how TCP/IP was evolved? 4.2.1

What is an IP address? Explain its meaning using examples. 4.2.1 What contents does an IP datagram have? 4.2.2

How does IP work? 4.2.2

How does TCP protocol overcome the unreliability of IP protocol? 4.2.2 What is a domain name system? 4.2.2

How to specify a communication uniquely? Give an example. 4.2.3 Why is UDP unreliable? 4.2.3

What is IPv6? Why do we need IPv6? 4.3 4.2

4.3

4.4

4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12 4.13

CHAPTER 5 INTERPROCESS