Princeton S* Network Systems

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

Architecting distributed systems can be very difficult. Arguably the hardest part of programming a distributed application is getting node coordination correct. I’ll define a node in this context as a service running on a single server which communicates with other nodes and together make up your distributed application.

What I mean by coordination here is some act that multiple nodes must perform together. Some examples of coordination:

• Group membership
• Locking
• Publisher/Subscriber
• Ownership
• Synchronization

One or more of these primitives show up in all distributed systems, so implementing them correctly is extremely important. While developing CRAQ, I originally implemented a very simple group membership service, but … Continue Reading