ipv6_m1_v1-2e

IPv6 Basics, Version 1.2 e

T.O.P. BusinessInteractive GmbH

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1 Introduction



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1.1 What you already know................................................................3 1.2 The Need for IPv6 .........................................................................4



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1.1 What you already know

In the Web Based Training TCP/IP Basics module 4 you were given a short introduction to the advantages of IPv6 compared to IPv4. We said that IPv4 - a protocol designed in the 1980s – will one day reach the limits of available address space. For this reason, IPv6 uses new IP addresses with 128 bits each, instead of the 32 bits used by IPv4. With new IP addresses on the Internet Layer a new header is introduced with IPv6 that occupies less space but offers maximum functionality. In this course we will dip deeper into the functions of this new exciting technology. Wherever possible we will compare IPV6 to IPv4 to understand the differences. As this course is an update training course it is recommended that you take some time to review at least module 3 (IP addressing) and module 4 (Internet Layer Protocols) of the TCP/IP Basics WBT. Perhaps you will find it useful to have the printed or PDF version handy so you can look things up on they occur in the course.



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1.2 The Need for IPv6

Current statistics show that IP address space will be finally exhausted sometime between 2010 and 2012. You have learned already about several mechanisms that are currently in use to cope with this problem. These are Network Address Translation (NAT), private IP address space, and Classless Inter Domain Routing (CIDR) with Variable Length Subnet Masks (VLSM). Unfortunately these techniques have several problems. NAT breaks with the end-to-end nature of TCP/IP communication because addresses can be changed in packets as they traverse the network. Several application protocols cause problems when NAT is in use. As more and more companies interconnect their internal networks for collaborative work via Virtual Private Networks (VPNs), more and more IP address collisions occur because the same private address ranges are used in many company networks. Even CIDR cannot prevent the IPv4 address space from running out. And as smaller and smaller IP address ranges are assigned to internet provider customers, another problem occurs. As you remember, a router needs to contain a routing table to make a routing decision and forward a packet correctly. Routers connected to small networks have small routing tables and connect to the internet via a single default route. But if a router is linked to the internet core it needs a huge routing table that fills up more and more with smaller and smaller routes as CIDR is used to save IPv4 address space. This reduces routing performance because lookups take much longer. At the start of 2006, a current core router routing table holds more than 177.000 network entries and consumes more than 100 megabytes of memory.

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