Ive been skimming over IPv6 over the last couple of days, and my written date is imminent so I wont be blogging in huge detail just skimming over some weak spots in my knowledge.

IPv6 Address Types

Most of us are familiar with the fact that IPv6 supports Multicast, Unicast and Anycast. Just like in IPv4 we can tell alot from the destination IP address, some of this is summarised below;

Aggregatable Global Unicast addresses belong in the 200::/3 range and are globally routable addresses for host to host communication. While the first 3 bits are always 001, the next 45 bits are allocated by the RIR (IPv6 allocations are generally given a /48), the following 16 bits can be used to define the subnet or Site Level Aggregator (SLA) and the final 64 bits are used as the interface ID.

Multicast - As in IPv4 they are used for one to many, or many to many communication, all IPv6 multicast addresses belong in the FF00::/8 range

Link Local Unicast addresses types are used for communication on the local link and are in the FE80::/10 range.  While the first few bits are FE80, the next 54 bits are always set to 0 and the remaining 64 bits are the MAC address in an EUI-64 format. Remember an EUI-64 formatted address is simply the mac with FFFE placed directly in the middle!

Solicited-node Multicast addresses are used for querying of network nodes for address resolution, it fulfils a similar purpose to ARP but is not broadcast. The messages to sent to the address FF02::1:FF00:0/10 with the last 24 bits set to the IPv6 address it is trying to be resolved.

IPv6 Message Types

There are a variety of message types which fulfil different functions which I should be aware of these are;

Router Advertisement (RA) – these messages are sent by the routers link local address to FF02::1  and advertise the link prefixes, MTU and hop limits. They are sent periodically or in response to a host seeing a RS message

Router Solicitation (RS) – these message are sent by hosts to  FF02::2 to query for the presence of a router, an RA message will be sent by the router in response

Neighbour Solicitation (NS) - these messages are sent by hosts to the solicited node multicast address or if known the target nodes address to query the other  hosts link layer address.  An NS message will receive a NA response from the host and used to detect duplicate addresses and ensure network reachability.

Neighbour Advertisement (NA) – these messages are sent in response to NS messages via unicast or sent to the address FF02::1 as a periodic advertisement

Redirect - this message type is sent by routers to a the link local address to inform them of a better next hop router.

I was planning to write a nice technical post on IPv6 migration techniques but I had a few cans of red bull and my mind has gone a wander.

Whenever IPv6 is mentioned it always causes a big rift in opinions, alot of people say that IPv4 will be totally deleted in 3 years +/-6months, according to RIPE who are responsible for IP & BGP AS allocation Europe. And the next Google’s and startups won’t be able to get IPv4 space and due to its rarity many people are concerned its going to become a commodity where companies will be bought/sold for their address space, there could even a potential black market in IPv4 space? Emerging countries such as Africa & China which are coming online will need huge allocations of address space to fulfill their needs, and mobile devices such as iPhones and internet devices everywhere becoming more popular there is a growing need. With NAT/PAT apparently harming innovation as there is a need for end to end addressing transparency, there is a clear need for more address.

But is IPv6 the answer?

Whenever IPv6 is mentioned it always causes a big rift in opinions, some people simply don’t believe that every host on the internet will ever change its TCP/IP stack for IPv6 as that change is a once in a lifetime opportunity and there is not a viable business reason to do so at the moment.

Vince Fuller who is a Senior Technical Consultant at Cisco Systems discussed recently that IPv6 is not the complete answer as although it solves the address limitations it does not solve the scalability issues issues we will eventually face with massive routing tables. I was lucky enough to speak to him at RIPE 56 and heard his presentation on a possible solution to some of the issues with Locater Id Separation (LISP).

Its going to be really interesting in the next few years to watch IPv4 “hit the wall”, and to see if it will be adopted and how long it will take, I wonder if it will become the chicken and egg conundrum of what will come first applications & websites or the user base?