The Next Generation zyx of the Internet: Aspects of the Internet Protocol Version 6 z I zyxwvutsrqponm David C. lee, Daniel 1. lough, Scott F. Midkiff, Nathaniel J. Davis IV, and Phillip zy E. Benchoff Virginia Polytechnic Institute and State University Abstract zyxwv This article presents an overview of several key improvements offered by the Inter- net Protocol version 6 (IPv6) over current Internet Protocol version 4 (IPv4). The top- ics covered include IPv6 addressing and routing concepts, changes to the minimum IPv6 packet size, flows, and traffic classes, the neighbor discovery and node auto- configuration mechanisms, and an overview of mobile IPv6 and the network securi- ty architecture. Transition mechanisms, such as dual stacks and the 6bone, are also discussed. The 6bone is a virtual network that is used to help test and facili- tate the development of IPv6. Key conce ts associated with the 6bone, such as setup requirements, IPv6 DNS support, anltunnel mechanics, are also presented zyxw he rapid growth of the current Internet, which operates using the Internet Protocol version 4 (IPv4), has creat- ed a number of problems for the administration and operation of the global network. These problems include the decreasing number of available IPv4 addresses for network nodes, and the rapid growth of memory and perfor- mance requirements for network routers. While changes to IPv4 have extended the life of the current Internet, these changes tend to create new problems and require a significant amount of overhead for network administration. The Internet Protocol version 6 (IPv6)l has been designed to support these extensions, and more, without creating the additional prob- lems. An excellent discussion of the requirements and back- ground €or Ipil6 can be found in [l]. This article provides a detailed introduction to the address- ing specifications, the prefix-based routing scheme, changes to the IPv6 minimum packet size, flows, and traffic classes, neighbor discovery and address autoconfiguration, mobile IPv6, and the IP security architecture. Additionally, ongoing IPv6 testing and deployment efforts are reviewed. Neither the IPv6 packet format nor the Internet Control Message Proto- col version 6 (ICMPv6) is discussed in this article; however, a detailed discussion of these and other topics may be found in For the curious, zyxwvutsrq IPv5 is the experimental Stream TransportIlprotocol. [l-61. This article differs from other articles by providing more up-to-date information, and delves into different techni- cal features of IPv6. Addressing Network addresses serve two purposes: first, to uniquely iden- tify an interface, and second, to aid routing by identifying “where” an interface is on the network. The 32-bit IPv4 address is divided into different classes, consisting of fixed boundaries between the identification of each network and the identification of each node. For example, a class B address has a theoretical possible range of 65,536 addresses, and a class C address has a possible range of 256 addresses. Fixed- sized addresses cause problems because most sites will need more than 256 addresses and fewer than 65,536 addresses. An IPv6 address is 128 bits in length, and the boundary between the transit network and site network subdivisions is not fixed, so networks can be sized accordingly. This allows a more flexi- ble addressing allocation strategy to be used. The remainder of this section discusses IPv6 address types. A number of address types exist in IPv6 [7], of which the basic types are unicast, multicast, and anycast addresses. A unicast address denotes a single host interface. A multicast address denotes a set of host interfaces. IPv6 no longer sup- ports the broadcast address, preferring the use of multicast addresses. Existing IPv4 services that require the broadcast 28 0890-8044/98/$10.00 zyxwvu 0 1998 IEEE IEEE Network JanuaryiFebruary 1998