I am writing this from a delayed BART car that was mis-routed this morning. As we traveled south from Oakland, the Dublin/Pleasanton-bound train didn’t make the turn over the mountains and headed south to Fremont. The train operator had to stop the train, turn it around, and get us back on the right track, which cost us about 15 minutes. Given that it happened during rush hour, I also wonder how much having to move our train out of the way caused delays to cascade through the system. I’m used to BART delays, but this is my first train mis-route.
Archive for May, 2008
It’s hard to build a conference wireless network. I’ve built a few over the past five years, and it is always a big engineering challenge. As you build the network, you refine your plans. When users arrive and start sending traffic, you refine your plans. As loads ebb and flow, you refine your plans. I won’t say it’s easy, but it is a well traveled path. Every major gathering of networkers requires wireless connectivity.
I’m accustomed to the user experience on wireless LANs built for industry trade groups like the Wi-Fi Alliance, the IEEE 802.11 working group, and the IETF. The Wi-Fi Alliance uses Michael Hijdra and his team at 2Fast4Wireless, and Verilan does work for both IEEE 802.11 and the IETF. This week, I’m speaking at the TERENA NetConnect conference. It’s only the first day, but I’ve had lots of trouble with the network.
First of all, the network uses web “authentication.” All of the conference attendees have been given a unique account, but the use of accounts is enforced by a captive web portal, not WPA. The Wi-Fi Alliance, IEEE 802, and the IETF all run an 802.1X network, though they also offer an option for unauthenticated access. It seems unfortunate to avoid using 802.1X at the TERENA TNC conference because TERENA’s Eduroam project has done a great deal to drive adoption of 802.1X, and many of the attendees are therefore familiar with 802.1X configuration.
When the plenary hall filled up, the performance went down very quickly. In the first eight minutes, I was disconnected four times. At eight minutes, the network connection gave up the ghost and quit working altogether. Before that point, I was seeing round-trip times that I hadn’t seen since the great AT&T frame relay outage of 1998, when round trips were measured in seconds from my then-office to, well, anywhere. Round trip times were also measured in second-plus range here, and are substantially higher even than the GPRS/EDGE network I use when commuting to work:
Reply from 220.127.116.11: bytes=32 time=1050ms TTL=246
Reply from 18.104.22.168: bytes=32 time=1513ms TTL=246
Reply from 22.214.171.124: bytes=32 time=1464ms TTL=246
Reply from 126.96.36.199: bytes=32 time=3253ms TTL=246
Reply from 188.8.131.52: bytes=32 time=3448ms TTL=246
Reply from 184.108.40.206: bytes=32 time=753ms TTL=246
Reply from 220.127.116.11: bytes=32 time=1575ms TTL=246
Reply from 18.104.22.168: bytes=32 time=1469ms TTL=246
Reply from 22.214.171.124: bytes=32 time=228ms TTL=246
Reply from 126.96.36.199: bytes=32 time=1538ms TTL=246
(188.8.131.52 is one of my favorite test IP addresses. It’s short, quick, easy to type, and it belongs to a highly redundant DNS server so it is almost always there.)
In the plenary, I was sitting towards the back of the room. As it became clear that the network was failing, people closed up their laptops in frustration. In the afternoon session, an attempted demonstration was aborted due to network performance problems. In all of the rooms, Windows reports low signal strength, so some of the performance problems could be due to AP placement constraints.
Last but definitely not least, there are two network names in use. A sign posted at the plenary room indicates that the split is used for load balancing, and instructs us to use the appropriate one based on user name:
I have connected to both networks, and they appear to use the same DHCP server. This is probably a misguided attempt at broadcast containment and/or load balancing. The Wi-Fi/IEEE 802/IETF networks use a single SSID and let the infrastructure figure out load balancing in a way that is transparent to the users.
I recently had a breakfast meeting in Daly City, and my host picked the location. We met at a restaurant that is right next to a residential area. I arrived first, and when I opened my laptop to start work, I saw several wireless networks available.
I chuckled slightly when I saw the following network name:
A few days later, I was visiting the dentist’s office. Upon opening up a Mac, I was greeted with the following message:
Ahem. Well, I guess it is a matter of trust…
Danny McPherson has written about Wi-Fi access in the “refugee camp” that is the SFO Red Carpet Club.
Having independently discovered last week that Red Carpet Club members could now get Internet access for free via T-Mobile, I was eager to get online in an airport without having to drop another $9.95 to T-Mobile…
Although I’m an elite flyer on United, I am a more elite flyer with American. The Admirals Club (American’s counterpart to the Red Carpet Club) has promoted their Internet access much better. Members all received multiple mailings, and guests who buy a day pass get a card with a code on it.
American partnered with MobileStar for access in the Admirals Club in the late 1990s. Until this year, the network continued to operate only as a T-Mobile hotspot. Now, the T-Mobile hot spot operates in parallel with the captive portal for the Admirals Club. Like the Red Carpet Club, all you need is a magic membership number:
To login, all you need is the United Mileage Plus number of the primary Red Carpet Club account holder [Ed note: In the American Admirals Club, it's the AAdvantage number of the account holder]. Now, having long questioned the wisdom of a luggage tag that displays these numbers, be it a â€œhole-punchedâ€ Mileage Plus membership card, or a more obvious oval-shaped Red Carpet Club tag, Iâ€™m even more wary now…
Fortunately, the Admirals Club luggage tags don’t have AAdvantage numbers on them. They do have a bar code that I assume can be translated easily into an AAdvantage number by American employees. On the other hand, if somebody is in the club, you can look for a regular luggage tag. Even on the plane, I bet you could do worse than by looking for the right color luggage tag. I would be willing to bet that most people with black elite luggage tags (Executive Platinum) are also Admirals Club members, and the likelihood only increases if you find somebody with a million miler oval.
Iâ€™ve yet to explore how difficult it would be to exhaustive search for valid numbers, or if multiple logins are permitted at a given time, or how far outside of the Red Carpet Club these numbers are valid, orâ€¦
As to the last point, the numbers are almost certainly valid as long as you can get to an AP. Although it is possible to build a wireless network that attempts to determine location and restrict services to a certain geographic area, the cost is quite high.
My experience is that the signal goes quite a long distance. Even before I forked over the money for an Admirals Club membership, I used their networks frequently. As a non-member, I could almost always sit in a gate area near the entrance and use the network. (I am a long-time T-Mobile hot spot subscriber through my cell phone plan.) In Chicago, I would sit in the hallway joining the H and K concourses, which was especially nice because there were usually unoccupied power plugs. At Los Angeles, I could sit at gate 41 and get a weak signal.
In the past, I tested whether T-Mobile’s hot spot network would support multiple simultaneous logins, and it does not. I have not tested whether the same is true for the captive portal they run for the Admirals Club. I would be surprised if that were the case because club members are allowed to bring guests, and it is likely that travelers with the ability to pay for an airline club membership have friends and family members who also have their own devices.
I have not sat down to formally add up how long I have spent in various countries, but I know that if I did so, the United Kingdom would come out on top. My first visit to the UK was over fifteen years ago, and in 1999 I spent three separate months on assignment on the outskirts of London near Heathrow. In spite of all of the time I have spent in the UK, though, I have never been to Stonehenge. On my recent trip, I decided to take advantage of my rental car and see the place.
On reflection, I think I was lucky and slipped between two waves of tour buses. As I arrived, a great number of people were leaving the site, and it stayed relatively uncrowded for the duration of my visit. Many of my photos show the crowds; the one below of the main circle is an exception.
English Heritage, the government body that manages Stonehenge, provides free audio guide instead of erecting interpretive signs that clutter the landscape. While generally well done, the audio guide has one particular difficulty versus signs, which is that the ravens that gather at Stonehenge make a great deal of noise. (At the reduced resolution of the photo below, the ravens are not visible as much more than specks, though.)
My departure was hurried by the arrival of dark clouds blotting out the blue sky. By the time I made it to the car, the rain had picked up and was quite heavy. Even though the rain had held off during my visit, the whole experience was still a fairly cold one. Stonehenge is set slightly above the surrounding terrain, and there is a great deal of wind whipping through the monument.
As I walked around the foot of the Acropolis, there was another “aha!” language moment. Monuments and sacred sites around the Acropolis were connected by a foot path called the Peripatos. Its shared root with the English word “peripatetic” was obvious (in part because that adjective was widely used to describe Rudy Perpich, the governor of Minnesota when I attended elementary school).
Off the Peripatos, the Stoa of Eumenes connects the Theater of Dionysis to the Odeon of Herodes Atticus. This photo was taken facing the Odeon.
At night, the Acropolis is lit beautifully, and stands out against the dark sky. Even at night, the brightly lit Acropolis serves as a beacon while walking around the city.
The same night, I took a photo of myself with the Acropolis as a backdrop. Unlike the previous photo, I had to keep the shutter speed down so my image would remain sharp. Exposing the dimly lit far-off background correctly required an extreme case of dragging the shutter. I mounted the camera on a tripod, exposed the photo for six seconds to collect enough light for the background, and used an on-camera flash to expose myself in the foreground.
On my first night in Athens, I walked from my hotel on Syngrou to the Acropolis. Although entry to the Acropolis was closed by the time I finally arrived near the Acropolis, I was able to set up my camera on the Areopagus and capture my exhausted grin after finally making it through the snowstorms.
History is inescapable when visiting Athens. (For me, that’s the major attraction.) On my visit, I made sure to save some time for the National Archaeological Museum. As you might expect, it has one of the best collections of treasures from ancient Greece.
Many of the most famous pieces in the museum are massive imposing marble statues. My favorite piece in the museum was not one of them. In the museum’s prehistoric collection, there is a relatively small gallery with artifacts from the Mycenaean civilization, including some tables with writing in the extremely old Linear B script. Linear B was used over three thousand years ago, and most of the writing that survives is everyday topics. If I recall the signs in the museum correctly, these tablets have livestock inventory and property records. Given the small size and fleeting nature of some of the records, these are probably some of the world’s oldest Post-it notes.
One of the major themes of the museum is the changing nature of funerary markers. Several funerary markers in the shape of lions exist, all of which have detailed, flame-shaped manes.
At a dead end in one of the inner rooms was perhaps the greatest treat of the visit, a small sculpture of Athena Parthenos (Athena the virgin). A massive version graced the interior of Parthenon; contemporary accounts indicate the original in the Parthenon used over a ton of gold. Two replicas believed to be faithful survive to this day, and the only complete one is the statue exhibited in the museum.
Details on the copy are incredible, down to the snakes that serve as a belt and the locks of hair that trail down on to the breastplate. (Reflections from nearby windows are unavoidable; as one of the foremost treasures of the museum, this piece is shown only in a protective case.)
In the center of the museum, a sculpture gallery shows off the height of Hellenistic sculptural achievement. I have always been impressed by the ability of sculpture to show movement. One of my favorite pieces in the Louvre is Diana of Versailles, showing the goddess of the hunt in pursuit of her prey. The original idea would have belonged to Greek sculptors, as shown here.
The gallery also has a striking statue of Aphrodite, holding a richly-detailed drapery.