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jg’s ramblings

jg’s ramblings
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Jim Gettys' ramblings on random topics, and occasional rants.
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Does the Internet need “Governance”?

jg’s ramblings - Wed, 12/11/2014 - 7:16pm
Dave Reed just published concerning network neutrality. Everyone interested in the topic should  carefully read and understand  Does the Internet need “Governance”? One additional example of “light touch” help for the Internet where government may play a role is transparency: the recent MLAB’s report and the fact that Cogent’s actions caused retail ISP’s to look […]

Bufferbloat and Other Challenges

jg’s ramblings - Mon, 06/10/2014 - 7:50pm
Vint Cerf wrote a wonderful piece on the problems I’ve been wrestling with the last number of years, called “Bufferbloat and Other Internet Challenges“. It is funny how one thing leads to another; I started just wanting my home network to work as I knew it should, and started turning over rocks. The swamp we’re […]

Traditional AQM is not enough!

jg’s ramblings - Wed, 10/07/2013 - 8:27pm
Latency, once incurred, cannot be undone, as best first explained by Stuart Cheshire in his rant: “It’s the latency, Stupid.” and more formally in “Latency and the Quest for Interactivity.” Any unnecessary latency is too much latency. Many networking engineers and researchers express the opinion that 100 milliseconds latency is “good enough”. If the Internet’s worst latency […]

Best Practices for Benchmarking CoDel and FQ CoDel (and almost anything else!)

jg’s ramblings - Tue, 02/07/2013 - 7:21pm
The bufferbloat project has had trouble getting consistent repeatable results from other experimenters, due to a variety of factors. This Wiki page at attempts to identify the most common omissions and mistakes. There be land mines here. Your data will be garbage if you don’t avoid them! Note that most of these are traps […]

Bufferbloat in switches/bridges

jg’s ramblings - Fri, 21/06/2013 - 12:23am
I received the following question today from Ralph Droms.  I include an edited version of my response to Ralph. On Thu, Jun 20, 2013 at 9:45 AM, Ralph Droms (rdroms) <rdroms@yyy.zzz> wrote: Someone suggested to me that bufferbloat might even be worse in switches/bridges than in routers.  True fact?  If so, can you point me at any […]

TCP Small Queues

jg’s ramblings - Mon, 01/10/2012 - 6:37pm
Linux 3.6 just shipped.  As I’ve noted before, bloat occurs in multiple places in an OS stack (and applications!). If your OS TCP implementation fills transmit queues more than needed, full queues will cause the RTT to increase, etc. , causing TCP to misbehave. Net result: additional latency, with no increase in bandwidth performance. TCP [...]

I’m attending the International Summit for Community Wireless Networks

jg’s ramblings - Mon, 24/09/2012 - 6:34pm
I will be giving a updated version of my bufferbloat talk there on Saturday, October 6.  The meeting is about community wireless networks (many of which are mesh wireless networks) on which bufferbloat is a particular issue.  It is in Barcelona, Spain, October 4-7. We tried (and failed) to make ad-hoc mesh networking work when I [...]

The First Bufferbloat Battle Won

jg’s ramblings - Mon, 06/08/2012 - 7:15pm
Bufferbloat was covered in a number of sessions at the Vancouver IETF last week. The most important of these sessions is a great explanation of Kathie Nichols and Van Jacobson’s CoDel (“coddle”) algorithm given during Tuesday’s transport area meeting by Van.  It is not to be missed by serious network engineers. It also touches on [...]

The Internet is Broken, and How to Fix It

jg’s ramblings - Wed, 27/06/2012 - 1:32am
Many real time applications such as VOIP, gaming,  teleconferencing, and performing music together, require low latency. These are increasingly unusable in today’s internet, and not because there is insufficient bandwidth, but that we’ve failed to look at the Internet as a end to end system. The edge of the Internet runs congested most often today. Where [...]

The Bufferbloat Bandwidth Death March

jg’s ramblings - Wed, 23/05/2012 - 3:16pm
Latency much more than bandwidth governs actual internet “speed”, as first best expressed in written form by Stuart Chesire’s It’s the Latency, Stupid rant and more formally in Latency and the Quest for Interactivity.

A Milestone Reached: CoDel is in Linux!

jg’s ramblings - Tue, 22/05/2012 - 7:37pm
The CoDel AQM algorithm by Kathie Nichols and Van Jacobson provides us with an essential missing tool to control queues properly. Eric Dumazet wrote the codel line discipline (based on a quick prototype by Dave Täht) which landed in net-next a week or two ago; yesterday, net-next was merged into the Linux mainline for inclusion in the next [...]

The Next Nightmare is Coming

jg’s ramblings - Mon, 14/05/2012 - 11:00am
BitTorrent was NEVER the Performance Problem BitTorrent is a lightning rod on two fronts: it is used to download large files, which the MPAA sees as a threat to their business model, and due to BitTorrent’s performance impact on Internet. Bram Cohen has taken infinite grief for BitTorrent over the years, when the end user performance problems are [...]

Fundamental Progress Solving Bufferbloat

jg’s ramblings - Tue, 08/05/2012 - 10:10am
Kathie Nichols and Van Jacobson today published an article entitled ”Controlling Queue Delay” in the ACM Queue. which describes a new adaptive active queue management algorithm (AQM), called CoDel (pronounced “coddle”). The article will appear sometime this summer in the Communications of the ACM.

Bufferbloat goings on…

jg’s ramblings - Tue, 01/05/2012 - 7:30pm
The bufferbloat front has appeared quiet for several months since two publications hit CACM (1), (2) and several videos hit YouTube, though I have one more article to write for IEEE Spectrum (sigh…). There has been a lot going on behind the lines, however, and some major announcements are imminent on ways to really fix [...]

I’ll be attending Penguicon on April 28, 29.

jg’s ramblings - Thu, 19/04/2012 - 5:16pm
I’ve never been to Penguicon before; but they invited me and John Scalzi (one of my favorite recent SF authors) to be guests of honor, so how could I possibly say no? I haven’t been to a SF con for decades; much less one crossed with a Linux conference.  I think it should be fun; [...]

An Minor Diversion into DNSSEC….

jg’s ramblings - Wed, 21/03/2012 - 4:59pm
I realised recently an interesting milestone has been reached, that will thrill the people who have slaved on DNSSEC for over a decade: DNSSEC running end-to-end, into the house the way “it should really work” without requiring any configuration or intervention has happened.  After all the SOPA/PIPA anguish, seeing DNSSEC come to life is really, [...]

Diagnosing Bufferbloat

jg’s ramblings - Mon, 20/02/2012 - 8:07pm
People (including in my family) ask how to diagnose bufferbloat. Bufferbloat’s existence is pretty easy to figure out; identifying which hop is the current culprit is harder.  For the moment, let’s concentrate on the edge of the network. The ICSI Netalyzr project is the easiest way for most to identify problems: you should run it [...]

Bufferbloat demonstration videos

jg’s ramblings - Wed, 01/02/2012 - 3:23pm
If people have heard of bufferbloat at all, it is usually just an abstraction despite having personal experience with it. Bufferbloat can occur in your operating system, your home router, your broadband gear, wireless, and almost anywhere in the Internet.  They still think that if experience poor Internet speed means they must need more bandwidth, [...]

ACM Queue: BufferBloat: What’s Wrong with the Internet?

jg’s ramblings - Fri, 09/12/2011 - 12:52am
ACM Queue: BufferBloat: What’s Wrong with the Internet?  A discussion with Vint Cerf, Van Jacobson, Nick Weaver, and Jim Gettys This is part of an ACM Queue case study, accompanying Kathie Nichols and my article that will appear in the January 2012 CACM (Communications of the ACM).

ACM Queue posting of Bufferbloat: Dark Buffers in the Internet

jg’s ramblings - Tue, 06/12/2011 - 5:07pm
Vint Cerf recommended that I start immediately blogging about bufferbloat a year or so ago, given the severity of the problem to avoid the usual publication delays; that’s why things appeared here first. But more formal publication has its merits; in particular, having articles for less directly involved in networking and/or more managerially oriented technical [...]

Apple Patents Portrait-Landscape Flipping: the patent system is broken…

jg’s ramblings - Mon, 18/07/2011 - 5:21pm
I noticed with interest Slashdot’s article last week on Apple Patenting Portrait-Landscape flipping based on control of one or more accelerometers in Slashdot last week.  As I work at Bell Labs these days, I don’t read patents, so I’ll just go on the summary I read there. Here’s some prior art from June 2001.  In that [...]


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