Illustrated TCP/IP by Matthew G. Naugle Wiley Computer Publishing, John Wiley & Sons, Inc. ISBN: 0471196568   Pub Date: 11/01/98

Part Three
Internet Protocol Version 6 (IPv6)

Chapter 139
Introduction

“The next IP.” “Version 6.” “Completely redone IPv4.” If you hear statements like this, ignore or correct them. IPv6 is not a new network layer protocol. Remember this, if anything, about IPv6: It is an evolutionary step for IP. Calmer heads prevailed during the two years of IPng working group and IPv6 has become an efficient IPv4 that is extensible.

IPv4 has proven to be a robust network layer protocol and there have been very few changes to it over the last 20 years. The biggest problem with IPv4 was the addressing, and these are the changes that were made. The addressing has not changed, but the methods of employing the 32-bit addressing have. IPv6 is a direct result of the shortages of the address space of IPv4. IPv6 is not revolutionary. It is the next step in the datagram delivery protocol known as IP. It is not a replacement for IPv4 per se, but there are many new and some revised functions of the protocol that improve upon it. Currently, there are enough fixes and extensions to the IPv4 protocol (not that there are many problems with the protocol) to make it last well into the year 2000. I have heard over the years, why implement a new version of IP when this one is working just fine? IPv4 simply put a Band-Aid a problem within a time period of need to further enhance the Internet to reach more people and business requirements.

As you read through this section, you should start to understand that the timing of this upgrade to IP is about right. The capabilities of IPv6 require a much more sophisticated computer than was required with IPv4. Generally, IPv4 could run on low-powered routers and endstations. The versatility of IPv6 will make use of the higher-powered routers and workstations.

When we changed IP, we did not change the function of any other protocol—again, the advantage of modular protocols. TCP and UDP stayed the same. Yes, the software calls to the IP interface are different: the socket interface known as Berkeley sockets (Unix), or for PCs the Winsock interface. But the basic functions of TCP/UDP and the applications that use them are the same. The other protocols that have to change are those that directly interface with IP. These are Domain Name Server, DHCP, OSPF, RIP, ICMP, and others.

You will hear a lot about IPv6 over the next few years, and IPv6 implementations will continue to remain as islands in the IPv4 Internet. This is the correct approach for IPv6. You cannot “flip the switch” as we did in January 1983 with IPv4. The Internet of today is extremely large and very commercial. There are still quite a few studies in progress to determine IPv6 addressing allocation, effects of IPv6 on IPv4 networks, tunneling, and so on. Slow-but-sure implementation. Test before implementing. Apply applications that have a need in the marketplace to IPv6. Work out the kinks before commercialization.

Whatever happened to IPv5? Well, it exists and is known as the Internet Stream Protocol (ST2) and is defined in RFC 1819. ST2 is an experimental resource reservation protocol intended to provide end-to-end real-time guarantees over an internet. It allows applications to build multidestination simplex data streams with a desired quality of service. The revised version of ST2 specified in RFC 1819 is called ST2+.

ST2 operates at the same layer as connectionless IP. It has been developed to support the efficient delivery of data streams to single or multiple destinations in applications that require guaranteed quality of service. ST2 is part of the IP protocol family and serves as an adjunct to, not a replacement for, IP. The revised version of ST2 specified in RFC 1819 is called ST2+. The main application areas of the protocol are the real-time transport of multimedia data (e.g., digital audio and video packet streams, distributed simulation/gaming) across internets. ST2 can be used to reserve bandwidth for real-time streams across network routes.

The foundation of IPv6 is IPv4. Like most great things in life, you build upon a foundation, something that you know works. Cars, over the years, are still built in the same fashion and still have tires, transmissions, engines, and bodies. But after many years, the extensions of those basics have led to more than just basic transportation. Many efficiencies and add-ons have been applied to the basic car to make it safer, better for the environment, and so forth.

The biggest change that you will notice throughout this text is the word dynamic. Routers and hosts discovery each other dynamically, hosts can configure themselves dynamically. There is even a replacement for the DHCP protocol that enforces (and efficiently uses) IP addressing. And, of course, the biggest change of all for IP: the address! Placing IPv6-capable nodes on a network with other IPv6 nodes and IPv6 routers will enable an IPv6 network to be established immediately via dynamics. Neighbor discovery protocols initiate and find the nodes on the network, nodes can autoconfigure their addresses, and routers simply have to have their interfaces configured and enabled, and off we go. IPv4 networks prevail, however; probably about 99.99 percent of all networks are IPv4. Therefore, we must make IPv6 work within the bounds of the existing IPv4 network.