Bufferbloat, Cablemodem and SDR/SDN

Yesterday I attended a session at the IETF meeting in Vancouver that will probably be remembered as being a key moment in the history of the Internet. In it Van Jacobson gave a fantastic talk on CoDel and on the Bufferbloat problem. At the end of the talk, Van presented some deployment issues, the second one being that that in a computer CoDel should be deployed closer to the device driver. I wondered if Van Jacobson own’s netchannels could not be a nice solution to this problem, but I did not get the courage to go to the microphone and ask this.

I did not think much of the first deployment issue at the time. Here the problem is that although Codel is now implemented in the Linux kernel 3.5, and so can easily be deployed in home NATs/routers, the right place to install CoDel would be inside the Cablemodem (or equivalent). Unfortunately this is not a place that can be easily modified, as it is fully under the control of whoever built the cablemodem.

Then later in the day I attended the Technical Plenary, and the technical talk was about Software Defined Network (SDN). I must admit that I never heard of SDN before, but the name itself immediately made me thing of SDR, Software Defined Radio – I worked on a project involving SDR few years back, and I still have the two USRP1 that I used for prototyping. My intuition seems right on, although the first talk by Cisco left me confused (I will summarized it as “this is horribly complicated, buy our stuff”). The second talk by a researcher was better although a little bit creepy (SDN in my home network and the controller outside?). With the third and last talk by Google, I now was convinced that SDN was in fact SDR for network.

Now all these talks got somehow processed during my sleep, and I woke up with an idea. Why do not use the same hardware that is used for SDR, but for implementing SDN? For example one can design an USRP1 daughterboard that would permit to connect it to the RJ45 connector from my cable provider. Then it is simply a programming problem – i.e. implementing Docsis 3.0 but this time with CoDel inside. And that would also open a lot of possibilities, like being able to run tcpdump on the cable side of the modem.

One can even dream of additional daughterboards for different wire connections – Ethernet, USB, HDMI, SATA, Powerline and so on. That would be an exciting project to work on.

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