While at the ISCWN in Vienna, I met Ben West of WasabiNet in St. Louis. He’s provided excellent coverage of the sessions he attended in his day-by-day posts here:
August 17, 2010
August 10, 2010
October 01, 2009
August 29, 2008
August 11, 2008
Asian innovation in mobile social networking
I'm continually amazed at the East-West cultural gap (that's between Asia and the US/EU, not between Boston and Silicon Valley). It goes both ways, but as an American Internet and mobile enthusiast with Asian connections, I'm usually struck by US ignorance of Asian Internet and mobile services.
Today, China has the worlds largest mobile population and the worlds largest Internet population. Korea is a leader in high speed broadband, as is Japan. Japan is also the #2 economy in the world and arguably the world's leading mobile society. Surely it's worth the time to understand what's happening in their markets!
For a change, over the weekend, I stumbled on an excellent presentation, What Asia can tell us about mobile social networks, from O'Reilly's conference, Graphing Social Patterns East, held in June in Washington DC. The presenter was Benjamin Joffe who resides in Beijing where, among other things, he's the founder of Mobile Monday Beijing.
Some of his numbers may be a year old, but the impact is clear. Asian services like QQ (740M registered users), CyWorld (used by 90% of young Koreans) and Mixi (10M mobile users in Japan) typically started before Facebook, have many more features, and are profitable!
Here's Benjamin's features list:
Check out the entire presentation. Well worth the effort!
February 10, 2008
January 13, 2008
December 09, 2007
November 08, 2007
October 22, 2007
October 21, 2007
October 16, 2007
October 02, 2007
September 20, 2007
September 15, 2007
September 05, 2007
Navizon is building the wireless covereage map I asked for
Last week I lamented the sketchiness of most wireless signal coverage maps and went on to suggest someone should "Use handset software to build mobile coverage maps." Now Shai Berger has pointed out someone who's already doing just that. It's Navizon from Mexens Technology. Their focus is wireless positioning, i.e. determining your location, but their approach includes downloadable software for smartphones, PDAs and handheld PCs.
Mexens is the provider of the first positioning system that combines WiFi, Cellular and GPS information. The Wireless Positioning System triangulates signals broadcasted from Wi-Fi access points and Cellular towers to help users find their way in most major metropolitan areas worldwide.
It is based on a collaborative network called Navizon. This is why we like to describe it as a peer-to-peer positioning system. Our users are sharing information about the position of WiFi access points and cellular towers, and by doing so, they keep our map of the Wireless landscape up-to-date.
And they offer such information in the form of a Google Maps mashup! Here's their take on mobile cell sites in a western part of Newton, Massachusetts USA.
With software on the WiFi enabled mobile devices they can capture every WiFi signal any of their contributors pass. Here's their map of WiFi signals on the northern edge of Natick Massachusetts. Red are secure access points and green are unsecure, i.e. open, access points.
Clearly, Navizon participants have driven through the area, but no one has gone into the residential neighborhoods, as I'm confident this community is riddled with broadband users and residential access points.
While the website is in English, coverage is global. Here are 200 of the more than 37K signals they've mapped in this part of London:
And 200 of more than 87K signals mapped in western Paris:
This is fascinating! But I have other things to do now, so I'll print out their 20 page white paper to read at a later point.
August 31, 2007
Use handset software to build mobile covereage maps
Over the past few weeks, while researching other subjects, I've stumbled on multiple websites providing mobile signal coverage maps. Two days ago, I hit an excellent HSDPA vs EVDO coverage map for the US that I can't seem to locate right now. :-) Today, I stumbled on Signal Map, a very interesting US centric site that aggregates user experiences.
Earlier I had bookmarked Cell Phone Tower Search, a site based on the FCC's database of US towers, and Sitefinder, an official Ofcom site mapping UK basestations.
I know I have seen other sites that, like Signal Map, attempt to aggregate actual user experiences, for example, Dead Cell Zones. But I haven't seen anyone who's taken the next logical step in acquiring accurate user data.
Why not offer mobile phone users some downloadable handset software that automatically captures as much information as possible and sends it to a common site like Signal Map? Yes, that puts a cost on the subscriber who agrees to participate, but I know my mobile plan includes a bundle of SMS messages that I never exceed and a data plan that I don't typically exceed. If I could configure how many SMS message were sent or how much data went out per month, I'd be happy to participate in such a scheme.
This approach may be problematic in areas where SMS and/or data is expensive, but with generous bundles and the (relatively) low cost of mobile service in the US, it seems likely this scheme could work. And, one such phone might generate 20-50 reports per month, much more user created content that you are likely to get by asking users to type information into your website.
To the folks at Signal Map, what do you think?
August 29, 2007
Best Skype outage post mortem so far
It's been more than ten days since the global Skype outage – time to reconsider what actually happened. The most credible analysis is not from Skype, but from Julian Cain in a series of comments (here, here and here) that he made to a Gigom article about the outage (or see the single file in "References" below). Julian is lead architect at Pando and, earlier, was head of Mac development for Kazaa at Sharmen Networks. So he knows a lot about peer-to-peer networks and his work at Sharmen put him in a position to know quite a bit about the P2P technology that's also used by Skype (and likely by Joost).
Background
Skype's P2P technology was evolved from FastTrack, originally developed for Kazaa. Their P2P network consists of clients and supernodes. Skype distributes client software which includes all necessary supernode software, so any client that has appropriate capacity and connectivity can be promoted to become a supernode. Supernodes dynamically link to other supernodes to support a distributed database and distributed index (called the distributed hash table or DHT). For Skype, the DHT layer is responsible for maintaining client presence info, contacts and icons/avatars, and handling call routing.
Root Cause
But as I pointed out in several posts during the outage, there's also a centralized component to the Skype network. That's the login servers. Julian refers to them at the "authentication servers" and/or "login/connectivity servers." They are implemented as one cluster of about 50 machines. As for the root cause of the outage, he asserts:
Skype employees introduced code into the "login/connectivity" server farm that was not compatible with current Skype clients.
Other Issues
While that was the root cause, it was helped along by other network characteristics, notably that each client connects to only one supernode at a time. According to Julian, there are 300+ clients per supernode and if a supernode goes off line, the 300 or so clients connected to it must reenter their "connecting" sequence, i.e., find and connect to another supernode.
A network with 8 million on-line users implies ~27K supernodes, a figure that's consistent with the ~20K supernodes estimated by Desclaux and Kortchinsky in 2005-2006 (see their June 2006 Recon presentation, PDF here). The other point from measurements by Desclaux and Kortchinsky is that each supernode attempts to maintain a list of all other supernodes which means there is a substantial amount of traffic between supernodes. This clearly contributed to the slow recovery, during which Julian commented:
Right now there are approximately 10,000 Skype networks instead of one single "in sync" network.
Scaling?
So I wonder, apart from the login server cluster as a single point of failure, is there also a scaling issue? FastTrack's breakthrough was the use of supernodes to make the system more scalable. But was that just one layer of scalability? If so, what happens when there are 300 million on-line users and one million supernodes? Perhaps Julian (or another P2P expert) could comment...
References:
I've extracted and assembled a complete copy of Julian's relevant comments.
Vanilla Skype part 1 and part 2, by Fabrice Desclaux and Kostya Kortchinsky, Recon, June 17th, 2006.
Skype traffic during the week of the outage, captured by Phil Wolff of Skype Journal.
August 21, 2007
August 16, 2007
Skype Network Crashes
As others are reporting, Skype clients have been disconnecting and reconnecting around the world. Here is Boston, I've been off line and back again at least four times in the past hour. And when I've reconnect, an amazing small number of others are seen as on-line:
In recent weeks, I've been seeing over 9 million users on line at this time of day, so 615K suggests very little of the global Skype network is accessibile to me, if they are on-line at all. A few minutes ago, Jan was seeing 773K other users from his site in Malaysia, so this really is global.
We've known, at least since 2004, that Skype's peer-to-peer network wasn't strictly P2P. The vast majority of traffic (control and media) is P2P, but everytime a client comes on line (well at least at startup and each login), it interrogates the Skype Login Server at skype.com. We also know that a Skype client must establish a connection to a super node to successfully login. But I don't know if there is anything about supernodes that cause them to crash if they can't reach a centralized or semi-centralized Skype server.
It will be interesting to see how this develops. Hopefully Skype will be forthcoming, but if not, I'm sure third parties will piece together an answer.
August 10, 2007
June 22, 2007
June 12, 2007
May 22, 2007
May 07, 2007
March 06, 2007
January 17, 2007
January 08, 2007
September 14, 2006
September 05, 2006
August 23, 2006
August 17, 2006
Scale free networks. long tails and big bucks - or maybe not
Some of my blog posts serve to organize a set of references on a topic that's important to me. This is such an occasion -- hopefully one or two others may share this interest.
Back in 2002, I really enjoyed Albert-Laszlo Barabasi's book on networks, Linked: How Everything Is Connected to Everything Else and What It Means, but haven't paid much attention to scale-free networks since then. Yesterday I stumbled on this interesting presentation by Chris Anderson at "SciFoo" last week, which prompted me to revisit the subject. The notes in Anderson's presentation include two great references (Limpert et al., Mitzenmacher) for the mathematically inclined, and the current Wikipedia article on Scale-free networks has excellent content and a lot more references.
New to me, are the diverse models that generate networks which are scale-free but differ in other meaningful characteristics. Barabasi discussed preferential attachment, a model which generates scale-free networks with highly connected nodes near the core. These networks are robust even if a large fraction of the nodes are removed. However the Internet, while a scale-free network, has it's highly connected nodes closer to the periphery, so the preferential attachment model doesn't apply. And as Wikipedia currently puts it,
Indeed, many of the results about scale-free networks have been claimed to apply to the Internet, but are disputed by Internet researchers and engineers.
The "big bucks" part of my headline was prompted by Chris Anderson's The Long Tail: Why the Future of Business Is Selling Less of More. Anderson's thesis, originally published in Wired magazine, is that the popularity of items in certain markets, like media, follows a power law -- the same law that applies to the connectivity of nodes in a scale-free network! In such a market, a few products have enormous sales but there is a very long tail of products that have only a few sales each. This long tail goes way out, so taken together, sales on the long tail represent big bucks.
Since Anderson's book was published there's been considerable argument about the long tail. Nicholas Carr has good summary of the argument between Wall Street Journal columnist Lee Gomer and Chris Anderson. But Andrew Odlyzko (on a private economist list, quoted here) has the best overall answer to the questions Lee Gomer raised.
As with the Internet, the key question is: does the phenomenon follow a power law (as scale free networks do)? If however, it follows a log-normal distribution, there's a lot less money to be made selling products out on the long tail as illustrated by this slide in Anderson's presentation:
As Anderson puts it:
But here’s the problem. I’ve been assuming that the powerlaw is the “natural” shape of all these markets. But there are other distributions that start off straight on a log-log chart, then fall off the line not necessarily because of a bottleneck effect but because they’re simply not powerlaws. The best example of this is the “lognormal” distribution, which often stays straight for several orders of magnitude before sloping downward. How to tell whether a market that falls off the line is a natural powerlaw shape distorted by a removable bottleneck or a natural lognormal market that will look like that no matter what you do? In markets such as film or television archives, this could be a billion-dollar question.
Indeed!
August 16, 2006
August 15, 2006
July 22, 2006
Facebook leveraging their elitist position
Myspace dominates US social networking sites. Indeed it dominates all US web accesses. As I noted in June, Facebook comes in 3rd among US users of social networking sites, far behind MySpace. But Facebook has nearly complete control of the college social networking market. And they appear to be leveraging that elite position very effectively.
Facebook started with incremental rollouts at US and then UK colleges. In September 2005 they added a separate site for high school students. In February 2006 they allowed college networks and high school networks to interconnect. Finally, a few months ago they started adding corporations. At every stage they have preserved a sense of exclusivity. For example, you must have an appropriate email address (initially a ".edu" address at a member school) in order to register. Of course once you are registered, you can substitute any other email address and, while you start as a member of the network at your college, you can search across all networks for people and invite them to be friends. So there's a strong sense of exclusivity or elitism, but not as much exclusivity as you think.
Fred Stutzman, a PhD student at the University of North Carolina, posts a very interesting analysis of Facebook adoption among incoming freshman at UNC. The first thing to note is that more than 90% of incoming freshman have signed up on Facebook by the beginning of the summer before they arrive on campus. This was true in 2005 and it is true now. What's different this year is that most incoming UNC freshman already have a large set of friends on Facebook that are not part of the UNC network. Here's the image from Stutzman's essay.
Obviously the high school program has worked wonders. Evidently anyone planning on going to college (at least to UNC), gets onto Facebook while they are still in high school.
Today Myspace gets five times the page views of Facebook, but of all the English language social networking sites (i.e. not counting sites like Cyworld), Facebook has the market position as the exclusive, I'd say elitist, service and they appear to be leveraging that position effectively.
Look for Facebook to move from #3 to #2 in short order.
Perhaps more important, when it comes to monetizing social networking services, Facebook's user demographics give them a strong position. (Some indicators here).
July 13, 2006
June 15, 2006
May 26, 2006
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