 Custom Search Guy recommends: A free desktop tool that monitors, or restarts, your VMware virtual machines. Download your free VM Console Guy’s Ezine 136 – IPv6 OverviewIPv6 – OverviewDo the numbers 192.168.0.1 mean anything to you? If you see an IP address of 10.0.0.1 do you think hmm… private network? Could 169.254.x.y indicate no DHCP server available? If any of the foregoing dot decimal numbers ring a bell then clearly you have a working knowledge of IP4. What I would like to do is give you a similar basic understanding of IPv6. The good news is that IPv6 principles are very similar to those of IPv4. Moreover, networks and applications can make the transition to IPv6 easily. The biggest stumbling block is that we humans struggle to see patterns within these new large hexadecimal numbers. My objective in this ezine is to give meaning to IPv6 addresses such as: 2001:0618:71A3:0801:1319:0211:FEC2:82DC Topics for IPv6
US Government steps into the IPv6 arenaBefore we get to know the new IPv6 hexadecimal numbers, I would like to say a few words about why you need a working knowledge of IPv6. What made me suddenly sit up and take notice was when I read that the USA government has decreed that all federal agencies must be IPv6 compliant by June 2008. Previously, I pigeon-holed IPv6 in the category of having more false dawns than teams like the Arizona Cardinals (NFL), or Newcastle United (Soccer). Insufficient IPv4 addressesChina and India will want a lot more IP addresses to become a presence on the internet. Moreover, developed countries need additional IP addresses for cell phones and other mobile devices. Cisco have analysed the data, and conclude that IANA’s allocation pool of IPv4 addresses will probably run out in between 3 and 10 years. This assessment of the available IPv4 pool takes into account American universities such as Stanford and MIT who have handed over their Class A addresses so that the rest of the world can benefit. Although techniques such as NAT and Supernetting (CIDR) have served their purpose in extending the useful life of IPv4 on the internet; however, in 2008 they are seen as limited, and are choking internet communication. At their heart, both IPv4 and IPv6 are level 3 routing protocols. However IPv6 is just that bit quicker, smarter and lot more scaleable. Nevertheless, it is the realization that the 32bit IPv4 just cannot deliver sufficient unique address which has been the driving force to upgrade to a 128bit IPng (new generation), or IPv6 as it’s better known. IPv6 – Theory Behind the NumbersIt is well-known that there are lies, damn lies and statistics. In the case of IP numbers, your best friends are estimation, approximation and the big picture. My point is that in the case of IPv4 mathematicians told us with a 32bit number there would be 4,294,967,296 possible IP addresses, in practice this turned out there were only about 17 million useful addresses. What springs to mind is Oscar Wilde’s adage ‘A cynic (mathematician) is a man who knows the price of everything but the value of nothing’. With the 128bit IPv6, the same mathematicians say there will be 340,300,000,000,000,000,000,000,000,000,000,000,000,000 IP addresses. Guy guestimates that there may be as few as: 18,000,000,000,000 useful IPv6 address. This is partly due to reserved and unassigned bits in the 128bit address. Even with my extremely low estimate, no worries, it means that everybody on the planet could be given 3,000 IP addresses. In my mind’s eye I see: one for their computer, one for their phone, car, fridge, cooker and every other appliance – then some. IPv6 – Getting to Know the NumbersIPv6 numbers will be in hexadecimal. Therefore you will see IP addresses containing not only numbers but also the letters ABCDEF, for example: 2001:0618:71A3:08D3:1319:8A2E:0370:7017. As you can see, 128bit numbers are split into 8 groups of 16bit. Observe how each group is separated by a colon rather than a dot. It is also apparent that this scheme dramatically expands on IPv4s 4 groups of 8bit numbers. Surprisingly, the hex letters are not case sensitive. Many private networks won’t need to use the full range of IPv6 numbering capabilities; hence many of the values will be zero. In this circumstance, thanks to compressing zeros, you will see simpler notation, for example, instead of FD01:0000:0000:0000:0000:0000:0000:0002, you will see FD01::2. Note the double colon :: indicating suppression of the intervening zeros. Thus the term ‘compression’ in IPv6 refers to the notation and not to the protocol packets themselves. The biggest reason that there will be fewer IPv6 addresses than the theoretical maximum is that each 64bit number will include the MAC address of the host. While incorporating the hardware address cuts down the available numbers, it makes this protocol more efficient, secure and useful than IPv4. IPv6 Examples 0:0:0:0:0:0:0:1 The classic loopback address. Compressed format ::1 FF01:0:0:0:0:0:0:42 A multicast address. Compressed to FF01::42 0:0:0:0:0:0:10.0.0.20 An IPv4 address. Note triple colon in the compressed form :::10.0.0.20 FE80::23a1:b131 A local-link address. An address for use in the internal organisation, but not on the internet. IPv6 Address Format (RFC 3587 and 2374)Here are 3 or 4 slightly different ways of describing the IPv6 address format. Global Routing Prefix | Subnet ID | Interface ID Slightly more information of first 4 bytes: 3 | 13 | 32 | 16 | (64-bit Interface ID) 001 | Top Level Aggregate Identifier | Next-level Aggregate ID | Site-level Aggregate Identifier Each IP address can be divided into sections. The first part contains routing information, while in the middle holds the site identifier and subnetting information. The last part of the hex address has the interface ID which is the 48-bit link-layer (MAC) address plus a 16-bit global identifier. If you want to know the bit-by-bit significance of each number in IPv6, the ultimate fountain of knowledge is held in ‘Refer For Comments’ documents such as RFC 3587 and RFC 2374, also 3315 for DHCP. These articles are freely available on the internet. Guy Recommends: The Free IP Address Tracker (IPAT) |
