Wednesday, August 1, 2012

IPv6 Musings

Those who know me know that I sound the IPv6 siren loudly and proudly.. This blog is no different and is part of my ongoing effort to help other technologists understand this monumental shift in how the Internet functions. I'll begin here by highlighting some of the most visible changes and how they impact your network designs. Future updates will include some more detailed technical information on each area.

Change #1: Address space increase

The address space in IPv6 has drastically increased to accommodate 2^128 unique addresses instead of the aging 2^32 addresses. This results in addresses that are 16 bytes long, separated into 16-bit chunks by a colon.

Typical IPv4 Address: 192.168.0.5
Typical IPv6 Address: 2001:db8:abcd:1234:5fcd:cdba:5892:5efb

As many users often now have multiple devices that require connectivity to the Internet this increase in address space provides much needed breathing room.


Change #2: NAT (Network Address Translation)


One of the ways we avoided the move to IPv6 a decade ago was the introduction of Network Address Translation technologies that allowed multiple networks and devices to use local-only IP addressing connected to one publicly visible IP address. This allowed you to connect a near limitless amount of devices to a single internet connection without consuming address space.

However, all has not been rosy in the world of NAT. NAT introduces problems with end-to-end connectivity which require extremely manual intervention to allow inbound communication to happen. Device performance lowers as each connection requires storing a record so communication can pass through freely. This often results in increased memory usage and decreased performance on lower end consumer hardware when flooded with lots of connections, such as P2P technologies.

Since a vast majority of networks use 192.168.0.0/24 and 192.168.1.0/24, connecting these networks during VPN sessions and company mergers can cause address space collisions and prevent end to end connectivity. Connecting these sites often requires NAT rules at the edge to allow communication to occur.

The increase in IPv6 address space, as well as the "globally unique" aspect of the assigned networks all but guarantees that the preceding problems are no longer an issue. No two globally connected networks should ever share the same address space. When you need to establish a VPN you merely connect the two sites together and add routes to direct the traffic to go over the encrypted tunnel. This vastly simplifies management and creation of site-to-site VPNs resulting in an overall reduction in the cost of planning these sorts of site mergers.