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I P V 6
An Introduction to IPv6: The *New* Internet Protocol
INTRODUÇÃO AO IPv6
A Internet, desde sua concepção até os dias atuais, tem sido uma ferramenta de extrema importância para o mundo científico, acadêmico e principalmente corporativo.
O IPv6, é muito mais que aumento de capacidade de endereçamento, em linhas gerais o novo protocolo de Internet permite:
Este novo cenário permite a criação de diversas aplicações e novos produtos com muito mais eficiência e baixo custo. Aplicações que variam desde adicionar funcionalidades a dispositivos móveis, TV Internet baseada em Multicast IPv6 (e-Television®), Voz sobre IPv6 (VoSix®) até novos mecanismos de VPN baseados em IPv6 (SING®)
De acordo com o surgimento de novos dispositivos que necessitam de uma conexão IP para maior aplicabilidade e liberdade, reforça-se cada vez mais como tendência o IPv6, tornando necessário visualizar os novos horizontes tecnológicos, permitindo uma liberdade de escolha entre o presente e o futuro previsto.
O IPv6 já é uma realidade e abre portas para os mais diversos segmentos da Internet.
Abaixo, está um briefing para os interessados nas características técnicas do protocolo. Temos disponíveis cursos e treinamentos focados nesta tecnologia, entre em contato para saber quando estarão abertas as próximas vagas.
Cumprimentos,
Robson Oliveira
Índice
An Introduction to IPv6: The *New* Internet Protocol
Link Original: http://www.raiden.net/techhelp/intro-ipv6.htm
If you have heard of "IPv6", you are probably asking what it is and you are not alone. The curiosity surrounding IPv6 is growing now that it is being discussed more often and more publicly. I'm here to shed some light on to what "IPv6" is and how it will affect your future internet experiences both positively and negatively; hopefully, more positively than anything else. First, to understand how we got to IPv6, we have to understand where things started. In the years between the late 1960's and early 1970's, UCLA and a group of other colleges got together and came up with a way to link their computers together over what became the archetype of the internet, later known as Arpanet. The theoretical foundation of this early incarnation was laid upon several memos written by an MIT employee named J.C.R. Licklider. Seeing its potential, the US Government began expanding and developing Arpanet to provide the military with an effective, redundant, scalable, and durable communication medium during wartime. But as time went on and the early internet grew, the framework and protocol system of ArpaNet just did not cut it anymore, hence TCP/IP was born and with it IPv1. Obviously, they weren't born at the same time, but one led to the other and eventually even these were outgrown.
Why are we changing to IPv6?
The simple answer is that it is due to the very poor planning in the creation and implementation of IPv4 coupled with the unexpected explosive expansion of the internet. This has caused the world to rapidly run short of available IPv4 addresses. Based off of RFC 791, the document from which the standards for IPv4 were first dictated, first published in 1981, IPv4 has proven to be a very robust, easily scalable and implemented protocol for standard networking uses and needs. However, the designers of IPv4 never foresaw many of the uses and problems that have appeared as the internet and computer networking in general has expanded and grown; tools and services like VPN's, IpSec, and much more. Even with 4,294,967,296 potential addresses, current practices limit the number of available addresses to a few hundred million. Certainly nowhere near as many as is needed. Hence why the use of NAT (Network Address Translation) is promoted so heavily these days as a way to conserve the ever shrinking pool of remaining IP addresses available to the world. One positive outgrowth of IPv6 is that DHCP will no longer be needed or, at the least, its need will be greatly reduced making administration of network IP space much easier for administrators without having to deal with the sometimes complicated administration of a DHCP infrastructure.
Another positive outcome of IPv6 will be better internet routing using QoS, Quality of Service, which routes packets based on priority. So for example, if one person is pinging a server and another is downloading a file, the one pinging will have less priority in their data transmission than the one downloading a file because the user who is downloading a file from has created a data stream which will automatically gain more priority over the simple ICMP data packets. Lastly, routing will be simplified because the IPv6 information header on each packet is far more flexible and can contain more detailed information than an IPv4 header thus allowing for faster routing of data across a network or the internet. Currently, most routers need to maintain as many as 48,000 different routes in their routing tables just to effectively route data that passes through them. IPv6 reduces this number by at least 75%. Nats will also no longer need to be used as there will no longer be a need for IP address conservation since there will now be enough IPv6 addresses available for each person on the planet to have 10 of their very own.
Also, if you're worried about IPv6 requiring you to change all of your software, learn new protocols, new methods of connecting, new ways of sending and receiving data or anything like that, fear not. The only thing really changing with IPv6 over what was in IPv4 is that you now have a larger address space which allows for more network addressable IP addresses, a more flexible header and packet system, and faster routing. As far as protocols are concerned, most will still remain the same so you can still ping, traceroute, or telnet to your heart's content. Security will now be native in IPv6, not an additional feature such as it appears in IPv4. Ports still work the same as well and UDP, TCP and other protocols are still present and accounted for.
IPv6 Addressing
To properly understand the addressing scheme of IPv6, we first have to understand the syntax of the actual address. With a standard IPv4 address, it consists of 32 bits broken into 8 bit segments separated by periods.
For example:
11111111. 11111111. 11111111. 11111111 (binary)
.255 (decimal)
With IPv6, you have a 128 bit address broken down into strings of 16 bits separated by colons.
For example:
1111111111111111: 1111111111111111: 1111111111111111: 1111111111111111: 1111111111111111: 1111111111111111: 1111111111111111: 1111111111111111 (binary)
FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF (aka Colon Hexadecimal)
So for example, a 16 bit string such as "0010000111011010" would convert to 21DA in hexadecimal. Hexadecimal is a binary addressing system that takes 4 bits of data and converts it into an alphanumeric value from 0 to F. This chart should give you a little better idea of how the binary numbers, decimal numbers, and hexadecimal values all compare to each other.
Binary Hexadecimal Decimal
0000 0 0
0001 1 1
0010 2 2
0011 3 3
0100 4 4
0101 5 5
0110 6 6
0111 7 7
1000 8 8
1001 9 9
1010 A 10
1011 B 11
1100 C 12
1101 D 13
1110 E 14
1111 F 15
As you notice, the binary digits are always 4 characters, aka 4 bits. The hexadecimal numbers are all 1 character, and the decimal numbers range from 1-2 characters in size. Since a hexadecimal number can't take up more than 1 space, any number greater than 9 has to be represented with a letter ranging from A-F. The decimal column lists the decimal values of each binary number. Therefore, a 16 bit string of data would need to be represented by 4 characters of hexadecimal data, or as we listed before in our example, something like this: 21DA
Simplifying the IPv6 address
For those of us too lazy to write out an entire 39 character IP address (32 bytes plus 7 colons) the wonderful people who wrote out the specs for IPv6 in RFC 2373, the informational document that dictates the standards for IPv6 decided to be nice to us. Since IPv6 addresses are designed to be computer friendly rather than human friendly (IPv4 addresses are designed to be human friendly) the designers of IPv6 were nice and gave us a way to simply each address. Take for example the following IPv6 address: 43FB:0000:0000:0000:0000:BB3F:A0A0:0000 This could be shortened to 43FB::BB3F:A0A0:0 instead. Now you might ask: "What's up with the double colon?" If you thought that, good for you. You've seen something many people would not have seen on their first try. The double colon (aka "::") signifies that we have removed a series of hexadecimal blocks from the address. These will always be contiguous zeros. AKA "0000:0000:0000:0000" can be shortened to just "::". Therefore when you see the double colon in an IPv6 address, it can be automatically assumed that they are all zeros. You can't however do this same shortening trick with any other combination of numbers that you can with a string of zeros. For the purpose of example, we will assume our address has numerous zeros in it in several groups. Let's also look at our abbreviated IP address again. Notice at the end there is a single zero after the last colon. If you already noticed this too, good for you. That is another simplification system for IPv6.
With IPv6 you can drop all the leading zeros off a 16 bit hexadecimal block leaving at least one character in each 4 character block. So in other words "0000" would become simply "0", and "0026" would simply become "26". In IPv4 this is done in much the same way by converting a number such as "035" into the much simpler number "35". Now, even though you can shorten an address using the double colon technique, you can only do it once in an address. Here's the reason why. If you take an address like "43FB:0000:0000:0000:0000:BB3F:0000:A0A0" and reduce both strings of zeros to the double colon like this: "43FB::BB3F::A0A0" how are you going to know how many blocks of 4 zeros are contained between the double colons? You can't know. Therefore, "43FB:0000:0000:0000:0000:BB3F:0000:A0A0" can only be reduced to "43FB::BB3F:0:A0A0" leaving one zero in the 7th block and a double colon for the 2nd through 5th blocks. That same set of 4 blocks can be reduced to simply "0:0:0:0" instead of the double colons as stripping the leading zeros off the number leaving a single zero in each block is permitted. Finally, when simplifying a number, you cannot throw out zeros at random. For example, "A0A0" can't be reduced to "AA". Once again you'd create a paradox for the computer as it wouldn't know where to replace the missing zeros. Now, if the block of 4 characters was "0A0A", you could drop the leading zero to make "A0A" instead.
Types of IPv6 Addresses
Just like in a normal IPv4 topology, there are 3 types of addresses in IPv6. Unicast, Multicast, and Anycast.
Unicast is standard point A to point B data traffic. This would be nothing more than me sending data from my computer, across the internet, to your computer and back again. That's the basic elements of Unicast addressing. So instead of needing to setup a special machine to dictate which server gets a given incoming connection first, IPv6 controls this automatically. Multicast is exactly how it sounds. Sending to one address on a subnet broadcasts to everyone on the subnet. This works the same as the broadcast address in IPv4.
Anycast identifies multiple network interfaces. In the simplest terms, the anycast address system is a "First man wins" system. Basically, if you have three network interfaces identified as part of a given anycast address and a request is sent to the anycast address, it is then forwarded to the first interface in the anycast group. Since that interface is not busy, the packet is then delivered to that interface. Say a second connection comes in and the first interface is busy. The connection is immediately routed over to the second interface. Then a third connection request comes in but now the first interface is not busy anymore so the data is routed to the first interface. This is a simple load balancing system built directly into IPv6.
Unicast IPv6 Addresses
Ok, let's further try to break down each of the addresses and look at just the Unicast address to start with. Since this will constitute about 90% of all traffic on the internet, and probably 99% of all traffic on your private network, we'll focus on this one type of IPv6 address specifically. With IPv6, subnets are done away with, in a manor of speaking. Instead of having to specify the subnet at the host level, it's specified at the address level. What this basically means is that only half of an actual IPv6 address deals with a specific host on the internet. This is the part that will probably baffle you to no end, the first 64 bits deal with the subnet. You're probably thinking to yourself, "Why would you attach the subnet to the IP address if the only thing that's going to use it is the actual host?" That's because unlike typical IPv4 subnets, with IPv6 you can do what is called hierarchical subnetting. In short, each part of the address dictates three basic things: the primary internet provider, such as Uunet, MCI, or one of the big backbone providers; the ISP; and the customer. Here is an example of how all 128 bits of an IPv6 address are broken down.
3 bits 13 bits 8 bits 24 bits 16 bits 64 bits
001 TLA ID Res NLA ID SLA ID Interface ID
Ok, now let's look at each of those segments.
001 - This is what is known as the "Aggregatable Global Unicast Address" or, in short, a "global address". IPv6 global addresses are equivalent to IPv4 global addresses. They are globally routable and can be reached on the IPv6 portion of the internet.
TLA ID - This is a Top Level Aggregation Identifier. The size of this field is 13 bits and identifies the highest levels of routing hierarchy. In short, these would be the major backbone providers like MCI, AT&T, UUnet, and others who provide the largest data channels on the internet. The TLA ID is used to simplify routing at these higher levels thus speeding up data routing and transfer times.
Res - This is a set of 8 bits that has been set aside for future use in case that either the TLA or NLA ID fields need to be expanded or a feature needs to be added.
NLA ID - This is the Next Level Aggregation Identifier. This field is 24 bits in size and would apply to your ISP. This both identifies your ISP, and allows them to create multiple levels of routing and addressing hierarchy within their organization to aid them in simplifying routing on their own network.
SLA ID - This is the Site Level Aggregation Identifier. In short, this set of 16 bits would apply to you, the end customer. It is used by an individual organization to identify the subnets within its own organization. This is the part that was previously referred to as subnetting. Once the basic routing is done and completed, it's down to nothing more than the simple internal subnets to determine where the packets go before reaching your machine.
Interface ID - This is your actual machine. Although 64 bits are set aside for your actual machine to uniquely identify it on the network, only 24 are truly needed and the rest can be set aside for additional subnetting and routing levels.
Local use Addresses
While many things in IPv6 are new and unique, there are many things that are much the same as they are in IPv4, if not done in a slightly different way. One example of this is local use addresses. These consist of Link Local and Site Local addresses. Link local addresses are more or less the IPv6 equivalent to the mac address already used on every network out there to identify individual pieces of networking hardware attached to the network. A link local address is automatically configured by the computer and is used for neighbor discovery and for querying of the DHCP server for an IP address and other information necessary on the network. These addresses are not world routable and are only used locally.
Site local addressing would be equivalent to the private network addresses used in Nat under IPv4. These addresses are not world routable and are used for data traffic within your local network itself. Compatibility is also a big factor with IPv6. Built into the specs for the protocol is a complete system by which IPv6 can interact with legacy IPv4 and vice versa. We won't go into the specifics of this, but if you had any worries about making the transition to IPv6 with many legacy clients, routers, and other elements of your network that are IPv4 aware only, you don't have to anymore, because this was already foreseen as being a big stumbling block to acceptance and has been implemented directly into the protocol.
On top of Link Local and Site local addressing, IPv6 also includes two of our old IPv4 favorites. The loopback and unspecified address's. Aside from some formatting changes, both work exactly the same as before.
Subnetting IPv6
Now that we've discussed some of the basic elements of IPv6, I'm sure you're probably saying to yourself "That's great, but how do we subnet under IPv6?" Well, that's both a simple, and a somewhat complicated answer. If you remember earlier in this article we discussed the breakdown of the IPv6 address and how the first half of the IP address was separated into TLA, NLA and SLA ID's. It's through those three separate ID's that subnetting takes place. When subnetting under IPv6, the average person will not need to be concerned with the TLA or the NLA sections of the IP address. Those are taken care of by the Internet Backbone Provider (ie MCI, Uunet, AT&T, Sprint, etc) and your ISP respectively.
Initially a pool of IP addresses will be assigned to an Internet Backbone provider who in turn parts out those IP blocks and assigns them to individual ISP's and customers giving each their own unique NLA number. At this point your ISP will then part out your IP address and assign you a unique block of IP's with your own block of SLA ID's. Most likely they will give you a block of 8 ID's, each of which can become a subnet if you so choose to use each of these ID's separately on your network as a unique subnet. What you do after this is entirely up to you. You can give every single device in your house its own ip address if you wanted to. With the current IPv6 subnetting standard the way it is, you could technically have millions of devices with hundreds of their own individual ip's assigned to them. But who needs that many? Although per the latest RFC the size of the interface ID has not changed, I suspect that at some point in the future this will be shrunk down to a more realistic number or made flexible to allow for subnets ranging from 2 ip's in size all the way up to the full 64 bits assigned to the Interface ID section of the IP address.
The challenges ahead for IPv6
In reality, with the current rate of usage of IPv4 addresses, it's not unrealistic to expect IP's to only be handed out on a per need basis. In other words, instead of a single ISP getting billions of potential addresses, they'd get several hundred thousand, possibly a million at most while the next segment of that IP block would be assigned to another ISP. I personally don't see IPv6 in full use worldwide for many years to come, but with China and several other Asian nations switching their entire nation to IPv6 in 2006, we may see it appear here and around the world even faster than the planned 2009 initial deployment of IPv6 setup by Icann. The only bad thing about switching to IPv6 is it isn't fully tested in a real world environment. We honestly don't know what will happen once the entire internet begins talking in IPv6. It may make the transition seamlessly, or it may fall flat on its face. There is also the other problem of legacy support.
IPv6 has native legacy support built into it that will allow it to communicate directly with the current IPv4 addressing system already in use on the internet. But that's not the big problem. Where things get sticky is all of the machines that are too old to know how to talk with an IPv6 network. Almost any machine with an operating system that was released in 2000 or after has an almost 100% chance of their operating system being IPv6 compatible. (If you're unsure, it's best to check with the organization responsible for the particular operating system you are using to see if it is compatible. IE Windows users would go to Microsoft, MacOS users would go to Apple, and so on.) The big problem lies with all the older mainframe computers that are scattered all over the world. Many of these are running operating systems that are 10, 20, and in some cases as much as 30 years old. These would most definitely not be compatible and therefore I expect that IPv4 won't be phased out as quickly as Icann and many other internet organizations responsible for the change to IPv6 would like. I suspect that IPv4 will be used in some form or fashion for at least the next 10 to 20 years.
Conclusion
It is true that IPv6 is not human friendly; however, in the long run, it will help solve a lot of issues with the current shortage of available IPv4 addresses on the internet. It will also address the rapidly growing size of the internet, newer "net-aware" appliances, and other growing difficulties with routing and much more. Although IPv6 is not scheduled to be implemented before 2008, expect to begin to seeing slow changes in the direction of IPv6 implementation shortly thereafter because 2008 is when the initial changeover to IPv6 is tentatively scheduled for. With 2010 being the year that all current IPv4 addresses are expected to be exhausted, the proliferation of IPv6 into everyday networking will become more and more common.
References:
Understanding IPv6 by Microsoft Press
RFC 791
RFC 2373
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