Monday, June 27, 2016

Feature Parity!

by Craig Miller

Bridging Feature Parity for all wheeled vehicles
We have solved problems for the 25 years or so that the internet has become a foundation of computer networking in our society, with many clever tricks, or even hacks. NAT (Network Address Translation) is probably the most well known. But there are others as well.

If we are going to move forward into the brave new world of IPv6, we need Parity with the features and capabilities of the legacy protocol, IPv4. That doesn't mean that we need similar tricks, but we do need similar solutions.

Wireless Ethernet Bridging

Case in point, I wanted to setup a wireless Ethernet bridge in my home to bring wired connectivity to a corner of the house where it is difficult to run wires. This seemed like a simple task of running a second router as an Ethernet bridge, acting as a wireless client of the first wireless router*.

Oops, lost the Ethernet MAC header

And that is where the fun began. Because, when one configures a second router as a wireless client, there is more going on that meets the eye. From a high level, the packet starts as Ethernet (802.3), but then changes to 802.11 (Wireless Layer 2 protocol), and then must change back to Ethernet. The last step is where the problem begins, what Ethernet MAC address to use, since it was stripped off when the 802.11 header was put on the packet?

Using Scapy notation, the packet would look like:
/Ethernet/payload (original packet)
/802.11/payload   (packet of the air)
/??/payload       (The Ethernet MAC address has been lost)

There are a couple of ways to deal with this, one could have been encapsulation of the bridged frame in 802.11 header, but instead a trick was used which only works for IPv4. Alas, no IPv6 frames will be bridged across the wireless link. Which in my home, kind of defeats the point.

WDS to the rescue, dang no standard

But wait, what about WDS (Wireless Distribution System)? After all, it was made for wireless bridging. Yes, it handles the problem of the the unknown Ethernet MAC address, and should be the solution. However, WDS was never standardized, and as such, is incompatible between different vendors and even different products (think chip sets) of the same vendor.

Still need solutions in an IPv6 world

We must demand feature IPv6 Parity from vendors and ask for the same from the open source community The networking problems that we have solved over the past 25+ years, still need solutions in an IPv6 world.

*Over the 5Ghz band, as the 2.4 Ghz band is way to crowded

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