[Bloat] [Ecn-sane] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

alex.burr at ealdwulf.org.uk alex.burr at ealdwulf.org.uk
Sun Mar 24 16:15:15 EDT 2019

Hi Bob,

I note that all the non-dependent claims of US20170019343A1 (claims 1,14,22) seem to assume use of the proportional-integral controller (Note, I am not a lawyer, and especially not a patent lawyer). In Appendix B of draft-briscoe-tsvwg-aqm-dualq-coupled, an alternate algorithm 'Curvy RED' seems to replace PI, but it is noted that 'the Curvy RED algorithm has not been maintained to the same degree as the DualPI2 algorithm '.

Can you comment on whether the Curvy RED algorithm could form a non-patent-encumbered dualq? In particular:
 - Why wasn't curvy red further developed? Was it found to contain some deficiency? Are you intending to present it as an alternative?
 - Does Curvy RED actually completely replace PI?
 - Can we have reasonable assurance that no patents will surface covering Curvy RED?


On Wednesday, March 20, 2019, 11:29:38 PM GMT, Bob Briscoe <ietf at bobbriscoe.net> wrote: 

1/ In 2016, I arranged for the hire of a patent attorney to undertake the unusual step of filing a third party observation with the European Patent Office. This went through Al-Lu's patent application claim by claim pointing to prior art and giving the patent examiner all the arguments to reject each claim. However, the examiner chose to take very little note of it, which was disappointing and costly for us. The main prior art is:
    Gibbens, R.J. & Kelly, F.P., "On Packet Marking at Priority Queues," IEEE Transactions on Automatic Control 47(6):1016--1020 (June 2002)
The guys named as inventors in AL-Lu's filing published a paper on PI2 with me, in which we included a citation of this Gibbens paper as inspiration for the coupling. The Gibbens paper was already cited as background by other patents, so the EPO has it in their citation index.

The coupling was also based on my prior research with Mirja before I started working with the guys from Al-Lu in the RITE European Collaborative project. we had to go through a few rejections, but Mirja and I finally got this work published in 2014  - still before the priority date of the Al-Lu patent application:
    Kühlewind, M., Wagner, D.P., Espinosa, J.M.R. & Briscoe, B., "Using Data Center TCP (DCTCP) in the Internet," In: Proc. Third IEEE Globecom Workshop on Telecommunications Standards: From Research to Standards pp.583-588 (December 2014)

2/ The only claim that I could not find prior art for (in the original EU filing) was a very specific claim about using a square root for the coupling. The Linux implementation runs this the other way round so that it only has to do a squaring. So I figured we were safe from that.

However, until just now, I had not noticed that Al-Lu has retrospectively re-written the claims in the US patent and in the EU patent application to claim this the other way round - as a squaring. And to claim the two random number trick. Both restructuring to use a squaring and the two random number trick were definitely my ideas (while working for BT in a collaboration with Al-Lu). I have emails to prove this (from memory they were actually both in the same email). This is important, because a patent has to be about mechanism, not algorithm.

3/ This is a positive development. It means this patent is on very shaky legal ground. I have been trying to put pressure on Nokia to license this royalty free. But now I see what they have done, I am going to have to get a different type of legal advice. 

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