Princeton S* Network Systems

I recently posted an article on Ed Felten’s group blog, Freedom to Tinker, which covers both technical and policy-related I.T. issues. It describes some technical issues and my recent experience with DMCA enforcement agencies, BitTorrent, and CoralCDN. I think our readers would be interested in it as well, as well as join in the lively conversation among commenters.
In the past few weeks, Ed has been writing about targeted and inaccurate copyright enforcement. While it may be difficult to quantify the actual extent of inaccurate claims, we can at least try to understand whether … Continue Reading

Together with Arvind Krishnamurthy, I’ll be chairing this year’s International Workshop on Peer-to-Peer Systems (IPTPS).  The workshop was started in 2002, which coincided both with the popularization of P2P file sharing (Napster, KaZaA) and the introduction of distributed hash tables (DHTs) from several different research groups.

Eight years later, P2P file sharing is still going strong (now through BitTorrent), while the previously-academic DHTs have found their way into real use.  DHTs now form the decentralized lookup structures for file sharing services—in the form of so-called “trackerless” BitTorrent—with the DHT in the Vuze service comprising more than a million concurrent users.  (As an aside, I’m proud to note that Vuze’s DHT is based on Kademlia, which was proposed by one of my officemates in grad school, Petar Maymounkov.)

These self-organizing systems have also found their way into the datacenter.  One notable example is the storage system, Dynamo, that forms the basis for Amazon’s shopping cart and other back-end  applications.  Or Facebook’s Cassandra, used for its Inbox search.  Or the rest of the key-value stores that do automated partitioning.  And we are starting to see these techniques being proposed for scaling enterprise networks as well.  With that in mind, we wanted to broaden the scope of this year’s IPTPS to include topics relating to self-organizing and self-managing distributed systems, even those running in single administrative domains.

We also plan to have a demo session at this year’s IPTPS to highlight developed and deployed systems.  The workshop will be collocated with NSDI in San Jose, so will be especially convenient for those in the Bay Area.  We welcome submissions (both paper and demos) from researchers, developers, and hackers.  If you don’t want to write a paper, come show off your running P2P system.

Paper submissions are due Friday, December 18, 2009.  More information can be found at http://www.usenix.org/event/iptps10/cfp/.

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Jen Rexford and I are jointly seeking to hire a post-doc to join us at Princeton.   We are looking for somebody to start sometime between February and June 2010 (ideally, as soon as possible) and stay for a duration of 18-24 months.

This research opportunity is part of the SCAFFOLD project.  SCAFFOLD is a new network architecture that focuses on better supporting distributed and wide-area services.  These services, run over multiple hosts distributed across many locations, need to respond quickly to server and network churn: both unexpected changes (due to equipment failures and physical mobility) and intentional changes (during planned … Continue Reading

This year’s HotNets workshop was held over the past two days in the faculty club at NYU; it was nice being on old turf.   The HotNets workshop has authors write 6-page “position” or “work-in-progress” papers on current “hot topics in networking” (surprise!).  Tucked into a cosy downstairs room, the workshop was nicely intimate and it saw lots of interesting questions and discussion.

One topic that was of particular interest to me were new ideas about datacenter networking; HotNets included two papers in each of two different research areas.

The first thematic area was addressing the problem of bisectional … Continue Reading

The last post argued how CoralCDN’s API through domain manipulation provided a simple yet surprisingly powerful content delivery mechanism.  Unfortunately, its technique flies in the face of the web’s use of domain names.

Conflating naming, location, and authorization, browsers use domains for three purposes:

1. Domains provide a human-readable name for what administrative entity a client is interacting with (e.g., the “common name” identified in SSL server certificates).
2. Domains specify where to retrieve content after they are resolved to IP addresses (through DNS).
3. Domains specify what security policies to enforce on web objects and their interactions, especially as it relates to browser Same Origin … Continue Reading
   

While my previous post argued that CoralCDN’s architecture design might not be ideal given its deployment, it has proven successful from the simple perspective of real-world use. Rather than any technical argument, we believe that the central reason for its adoption has been its simple user interface: Any URL can be requested through CoralCDN by appending nyud.net to its hostname.

Interface design

While superficially obvious, this interface design achieves several important deployment goals:

• Transparency: Work with unmodified, unconfigured, and unaware web clients and web servers.
• Deep caching: Support the automatic retrieval of embedded images or links also through CoralCDN when appropriate.
• Server control: Not … Continue Reading
  

Most of my posts about CoralCDN to date have discussed techniques to make the system more robust; now I discuss what it got wrong.  While nice, many of these optimizations were in fact moot: CoralCDN’s design is ill-suited for its current deployment and usage.

Let us frame this argument by first considering some usage statistics from CoralCDN’s deployment.  The available aggregate data from 167 of the ~250 operating CoralCDN nodes during one recent, randomly-chosen day (January 20, 2009) shows that these nodes received a total of 9.74M requests … Continue Reading

So after a few months of (occasional) posts, we finally decided to give the blog a name.

Dirty Slate Design reflects a design philosophy for systems and networking research, where deployability is a central goal.  While it’s often tempting to try to solve problems by wiping the slate clean and starting afresh, expecting a complete redesign and redeployment of systems as important, complex, and far-flung as the Web or the Internet is rather optimistic at best.

So, rather than implying something that is just “quick and dirty,” this philosophy tries to push new functionality or designs in a way that can be … Continue Reading

In the previous post, I discussed how CoralCDN implemented bandwidth restrictions that were fair-shared between “customer” domains. There was another major twist to this problem, however, that I didn’t talk about: the challenge of performing such a technique on a virtualized and shared platform such as PlanetLab.  While my discussion is certainly PlanetLab-centric, its questions are also applicable to other P2P deployments where users run peers within resource containers, or to commercial hosting environments using billing models such as 95th percentile usage.

Interacting with hosting platforms

CoralCDN’s self-regulation works well in trusted environments, and this approach is used similarly in other peer-to-peer … Continue Reading

For commercial CDNs and other computing services, the typical answer to resource limits is simply to acquire more capacity.  As CoralCDN’s deployment on PlanetLab does not have that luxury, we instead apply admission control to manage its bandwidth resources.  This post describes some of these mechanisms, while we’ll take a step back in the next post to describe some of the challenges in doing resource accounting and management on a virtualized and shared platform such as PlanetLab.

Following the Asian tsunami of December … Continue Reading