sean's place

Thoughts on IPv6

I got to reading this post (don’t ask why), and I was startled that almost everyone who posted (especially those not in favor of IPv6) forgot that internet access is two-way.

Let’s back up a moment; the aforementioned discussion would be on the relative merits of IPv6. The primary benefit of IPv6 is the vastly increased address space; from 32 bits (~4 billion unique addresses) to 128 bits (billions and billions and billions of times more than IPv4). In the recent past, NAT (network address translation) was seen as a way to slow the exhaustion of IPv4 address space by translating “private address” space into a single (or a small few) “public” addresses. This is common in homes (192.168.x.x addresses internally, a single dynamic address externally) and in businesses.

The sad fact though is this concentrates on the access side of the equation. This solution works fine if you care about one way communication. This whole scheme though breaks when you consider streaming video via RTP (the streamer opens a return connection to you to send video¹) or similar protocols. As a more simple example, take the case where you might want to copy files from one of your computers at home to to your computer at work. Getting that to work through NAT is certainly possible, but often troublesome (it’s commonly called PAT and it involves mapping  a single port on the “outside” to an internal port on the “inside” — it’s a chore, if anything).

As we move forward and bandwidths increase (fiber to the home, DOCSIS 3, and grudgingly, VDSL), the “internet” connection at home will look a lot more like a “network” connection. Your video, voice, and data service will come over IP and new worlds of data access will come to exist. With public addressing for everything, protocols heretofore foiled by NAT will start to work and the needfulness of port-address-translation will be all but extinguished. To access your data at home, you’d need only connect to your system at home through its public address (which you would have found by using DNS, for IPv6 addresses do not lend themselves to memorization). The days of brokering connections through mutually-accessible sentinel servers out on the internet will become a thing of the past.

Alas, I digress. IPv6 is necessary, but once more, it’s a good thing. It will help transform individual connections to the internet from single-use appendages to a true internetworked environment with enormous advantages to all who use it.

¹ – not a perfect analogy, but it works