IETF 80 highlights: congestion control
There were several interesting talks on various aspects of congestion control at IETF 80, spread around various working groups and research groups; the majority of work that I would classify as actual research being done in the IETF and IRTF at the moment seems to concern congestion control in some way or other.  I've already written about Multipath TCP and Bufferbloat; here's a potpourri of other TCP problems and proposed solutions.  Most of these came out of the meeting of the Internet Congestion Control Research Group (ICCRG) - strictly part of the IRTF rather than the IETF - but the presentation on SPDY came from the IETF Transport Area open meeting.
EuroSys 2011, day three
Session 7: Better Clouds
Kaleidoscope: Cloud Micro-Elasticity via VM State Coloring
The problem is that load on internet services fluctuates wildly throughout the day, but the bursts are very short (median around 20 minutes) and cloud providers are becoming "less elastic" (bigger VMs up for longer), and cannot support such short bursts because VMs are too heavyweight. The solution is based on VM cloning (SnowFlock), but the lazy propagation of state in SnowFlock leads to lots of blocking after the clone (for TPC-H). The solution is to do page coloring to work out the probable role of the page (code vs data, kernel vs user, etc.), and then tune the prefetching by color (such as read-ahead for cached files). Kaleidoscope also reduces the footprint of cloned VMs by allocating memory on-demand, and performing de-duplication. Most server apps tolerate cloning (only change is a new IP for the clones), and SPECweb, MySQL, httperf work fine. The experiments involved running Apache and TPC-H. Blocking decreases from 2 minutes to 30 seconds. TPC-H takes 80 seconds on a cold Xen VM, 20 seconds on a warm one, 130 seconds on a SnowFlock clone, and 30 seconds on a Kaleidoscope clone. Based on a simulation of an AT&T hosting service, Kaleidoscope achieved 98% fewer overheads using a 50% smaller data center. - dgm36
EuroSys 2011, day two
Session 4: Joules and Watts
Energy Management in Mobile Devices with the Cinder Operating System
A new mobile device OS, whose aim is to allow users to control their energy use, and allow applications to become more energy-efficient. First abstraction is throttling, which limits the draw that a particular application may have. However, the energy use is bursty, so this uses a reserve buffer that allows an application to use more energy if it has been running below maximum for a while. A process with an empty reserve will not be scheduled. To prevent hoarding of energy, the reserve drains with multiplicative decrease (e.g. 10%/sec). Reserves may be nested, to, for example, isolate the energy usage of a plugin like Adobe Flash. Energy may also be ring-fenced in "virtual batteries" for uses such as emergency calls. The OS abstraction is a process launcher called "enwrap", which launches an application with an allocation of power consumption. Background applications draw power from a smaller virtual battery to prevent unexpected power draw from applications you can't see; this is managed via a custom window manager. Development issues arose from the implementation of the HTC Dream, which uses a binary blob shared object to interact with the secure ARM9 core, and the exposure of the battery level as an integer 0 to 100; this led to concerns that future mobile phones will be more difficult to develop research OSs for, as there is a move to more use of secure cores and signed code. As a result of these frustrations, they moved to implement their abstractions in Linux, giving Cinder-Linux. One challenge was IPC: it was necessary to attribute energy use in daemons to the process making the IPC request. (This was easier in Cinder due to the use of gates, based on the same mechanism in HiStar.) One application developed was an energy-aware photo gallery, which modulated its download rate depending on energy properties. Next step is working out how to use these primitives, in terms of UI design (presenting a breakdown of energy use to users), energy modeling (currently use a simple energy model based on offline profiling, but could use something more sophisticated such as the approach described in the following talk), userspace code instrumentation and running Android (Dalvik) on Cinder.
EuroSys 2011, day one
Session 1: Data, Data, Data
Keypad: An Auditing File System for Theft-Prone Devices
The challenge is that mobile devices are prone to theft and loss, and encryption is not sufficient, because people have a habit of attaching the password to the device on a post-it, and it is vulnerable to social and hardware attack. Aim is to know what (if any) data is compromised in the event of a loss, and prevent future compromises. Solution is to force remote auditing on every file access (with encryption), by storing keys on the auditing server; this is done in the file system. File system metadata are stored on the trusted server. There are significant challenges in making this performant: caching/prefetching/preallocation are used to optimize key requests, but file creation is more challenging to optimize due to file systems semantics. Blocking filename registrations have correct semantics, but poor performance; vice versa for non-blocking registrations. To reconcile this, force a thief to use blocking semantics while allowing the user to use non-blocking semantics (as much as possible), which is based on using filenames as public keys. Second challenge is allowing disconnected access: the idea is to use multiple devices carried by the user to cross-audit file accesses, which still requires devices to hoard keys before going disconnected. - dgm36
20th International World Wide Web Conference – WWW 2011
I am just back from Hyderabad, in India, where I attended the 20th International World Wide Web Conference, also known as WWW 2011, to present our work on tracking geographic social cascades to improve video delivery.  This conference, organised as usual by the International World Wide Web Conference Committee (IW3C2),  represents the annual opportunity for the international community to discuss and debate the evolution of the Web, providing a mixture of academic and industrial content.
The word cloud shows pretty well the main themes of the conference this year, which heavily revolved around two large pivotal aspects: "social" and "search". Interestingly, there was not any attempt of merging the two things together, as Aardvark tried last year. Not surprisingly, "networks" are still popular in the community, and "Twitter" still enjoys a lot of interest, even though this may change with their new controversial Terms Of Service, which are likely to hamper social media data harvesting.
Overall it is a fairly big conference, with 2 initial days of workshops, tutorial and panels and then 3 days with 81 research papers. Also, there were three world-known personalities such as Dr. Abdul Kalam, Sir Tim Berners-Lee and Christos Papadimitriou that gave a keynote each. I will give a brief summary of the main research themes, with pointers to the most interesting papers. However, it was physically impossible to attend all the research sessions, as they were often happening simultaneously: you can find much more information on the conference website and on the official proceedings.