Wednesday, August 8, 2012

Stanford Linear Accelerator tour

At the recent Joint Techs conference, our host Stanford University arranged a lunch time tour of the Stanford Linear Accelerator Center (SLAC) for a small group of attendees. I signed up early as I knew it was going to popular with this crowd. SLAC is a 50 GeV electron-positron accelerator operated by Stanford on behalf of the US Dept of Energy.

(SLAC is now officially known as the "SLAC National Accelerator Lab".)

This is the second particle accelerator site I've visited. In the summer of 2007 (also during a Joint Techs conference), I saw Fermilab and the 2 TeV Tevatron, at that time the world's most powerful particle accelerator. My annotated photos from that visit are on flickr. The Tevatron ceased operation in late 2011. One of these days, I hope to visit the Large Hadron Collider at CERN.

Here are some photos from the SLAC tour. The full set is also available.

Bebo White, a noted SLAC computational physicist, was our tour guide. He's an entertaining and jolly character, who by his own admission looks like Santa Claus :-)

How the LINAC works:

Hmm, Science has a long way to go!

SLAC had the first website in North America (the first in the world of course was at CERN, where Tim Berners-Lee worked). Seeing a NeXT Cube brings back memories. That was my main computer for most of my undergraduate years at Penn, when I worked for NeXT as a campus consultant.

Mock-up of accelerator components just outside the end of the Klystron gallery:

Facilities photo/map:

The Klystron gallery along the nearly 2-mile long building that houses the main linac. Klystrons are the key driving force for the accelerator and produce amplified electromagnetic carrier waves that help boost the electrons along the beam line. The Klystrons are to the left of this photo, and sit above the main accelerator beam line which is situated 25-feet beneath the ground.  There are 240 Klystrons in total. The particles are injected at the other end of this tunnel.

Our merry tour group ...

Sunday, August 5, 2012

A Look at World IPv6 Launch Traffic Measurements

The World IPv6 Launch website has compiled a set of measurements at I'll take a quick look at some of them here, with a focus on universities.

The "Network Operator measurements" include data collected by Google, Facebook, and Yahoo! for access to their services on June 6th 2012 from the various network operator participants registered for the event. There were only 77 networks in total registered. I'm sure there are a number of other qualified networks that could have provided significant numbers of IPv6 users and traffic. I suspect the initial requirement that network operator participants be able to demonstrate that at least 1% of their traffic constitute IPv6 prior to the event likely dissuaded some potential participants from registering.

Different views of the network operator measurement charts require manipulating javascript controlled knobs at the website, so I can't provide a direct URL link to them. Instead, in the discussion below, I'm including the relevant screen captures.

View by Total Traffic 

The default view presents the participating networks sorted by total volume of IPv6 traffic measured, although the absolute volume number is not disclosed. Several large ISPs lead the list, with Free Telecom (France) occupying the top spot. AT&T (US), KDDI (Japan), RCS & RDS (Romania), Comcast (US), and Verizon Wireless (US) round out the next five. There is a significant disparity in the proportion of IPv6 traffic generated by those networks though, with Comcast seeing only 1.47% and Free seeing 17.35%. I suspect the numbers for Comcast will go up significantly as they turn up IPv6 on more of their home network customers during the coming year (the number was 1.5% on June 6th).  The US wireless carriers should also see their numbers go up as more of their users switch to IPv6-enabled 4G/LTE cell phones.

It's great to see a number of US universities (including my own) feature prominently in the top part of this list also - in ranked order: Indiana University, University of Pennsylvania, Virginia Tech, Louisiana State, and University of Iowa.

View by IPv6 Traffic Percentage

Sorting the table by the "IPv6 traffic percentage" column (the 3rd column below) produces some very impressive looking numbers. In this measure, universities start to dominate the rankings. The top two spots are held by Virginia Tech and Louisiana State, for which close to 60% of traffic constituted IPv6. Other notables include Marist College (53%), Indiana University (49%), RPI (47%), Penn (32%), University of Iowa (31%), Karlsruhe Institute of Technology (20%), & University of Phillipines Diliman (12%).  The effect of many of these universities having large parts of their campus networks IPv6 enabled and presumably large numbers of IPv6 enabled computers on those networks undoubtedly had a lot to do with these results.

It would be interesting to see more detailed measurement data from some of these extensively IPv6 enabled campuses about what proportion of their total traffic is IPv6 (as opposed to the subset of traffic only to a set of popular IPv6 enabled services). I hope to be able to share some data from Penn in the near future - we're currently dealing with some IPv6 traffic accounting bugs with a router vendor first. But our initial calculations are that we were seeing IPv6 account for 8 to 10% of the total traffic traversing the campus border during peak hours of the day. Even though the vast majority of the Internet is not IPv6 enabled, the existence of a number of popular and high-traffic generating services (Google, YouTube!, Netflix, etc) are likely skewing the numbers in favor of IPv6.