VPN Package Remote Access Users

171 Appendix A. Emerging Internet Technologies A.1 IPv6 Because VPNs ultimately use the Internet as their transport medium, they are subject to the advantages and disadvantages associated with using the Internet Protocol IP. As you are probably aware, the mechanics of the Internet the TCPIP protocols rely not exactly on the familiar names that we are used to seeing in URLs, such as www.ibm.com and ftp.uu.net, but rather on a lower level addressing scheme that uses IP addresses or dotted quads. An IP address, such as 207.25.97.8, specifies precisely one computer. The IP address is the lowest common denominator separating one machine from another. A hot topic among networking professionals is that the current pool of IP addresses is drying up. Since the IP address is formed by putting 4 bytes together, with each byte having 256 combinations 2 8 , there is a limited number of IP addresses available 2 32 , or 4,294,967,296, to be exact. You may be thinking that four billion addresses is nothing to sneeze at, which is true, but the explosive growth of the Internet world-wide has caused a great strain on the system for deploying those addresses. One reason for this is that huge blocks have already been given out and the system for assigning new ones is antiquated and difficult to administer. The current version of the IP protocol is Version 4, and Version 5 disappeared while still under discussion. IP Version 6 IPv6 for short is a project supported by networking companies, technology professionals, and organizations such as the Internet Engineering Task Force [IETF], to increase the size of the IP address pool to accommodate the massive growth expected on the Internet over the next several decades. Rather than simply increasing the size of the IP address pool, the ongoing work with IPv6 addresses a whole host of architectural issues. There is a virtual mountain of Requests for Comments, or RFCs, devoted to the design and implementation of IPv6. From RFC 1887 we can see a few of the topics being explored: • Topological information included to significantly reduce routing protocol overhead • Additional levels of hierarchy with anchors built in to ease future growth • Standards for mapping service providers and subscribers to components of an IPv6 address • Address assignments for all network entities based on growth and need • Allocation of the IPv6 addresses by the Internet Registry • Multi-homing and multiple domain routing choices • IPv4 address space mapping into IPv6 • Multicast addressing • Mobile host addressing • Administrative addressing • Mechanisms for publishing routing information to third parties • A division of routing policies into host-to-router, router-to-router inter-domain, and domain-to-domain In summary, IPv6 is analogous to what the phone company was required to do to handle long distance calling. When the user prefixes an area code to the already existing number, the telephone exchange can route to that area from the outside simply by consulting the first three numbers and looking up the cityarea to which the call should be routed. Hence, a call placed