It is our great pleasure to welcome you to Barcelona, Spain for SIGCOMM 2009, the flagship conference of the ACM SIG on Data Communications!
With great enthusiasm we have put together for you a rich and varied technical program that includes 27 full-length papers that will be presented over three days; a keynote talk by the SIGCOMM Award winner, Jon Crowcroft; the announcement of the SIGCOMM Test-of-Time Award; five one-day workshops that range from research on enterprise networks (WREN) to new forums on programmable routers and virtualization (VISA, PRESTO), online social networks (WOSN) and mobile systems and applications (MobiHeld); and two unique sessions with 19 posters and 23 demonstrations that highlight promising early-stage research. It is a packed program, full of intellectually stimulating forums, each of which has the potential of leading to new important breakthroughs.

It is a great pleasure to welcome you all to Barcelona and to a rewarding week of immersion in the very best research work in the field of networking.
Sigcomm is an extremely selective conference and this year was no exception: we received 267 submissions, out of which 27 were selected for publication. Authors worked very hard to submit high quality papers, and we want to thank them all. The selection of the final program would not have been possible without the help of 60 highly dedicated and skilled Technical Program Committee members, who worked over a period of 10 weeks producing almost one thousand reviews and a similar number of comments. Our thanks goes to them as well.

As researchers we have a duty to communicate our ideas. As communications researchers, we are privileged to study the technology and phenomena that are so transforming human society. We seek to understand and enhance the very tools with which we can convey our contributions to human knowledge.

This paper presents SoftRate, a wireless bit rate adaptation protocol that is responsive to rapidly varying channel conditions. Unlike previous work that uses either frame receptions or signal-to-noise ratio (SNR) estimates to select bit rates, SoftRate uses confidence information calculated by the physical layer and exported to higher layers via the SoftPHY interface to estimate the prevailing channel bit error rate (BER). Senders use this BER estimate, calculated over each received packet (even when the packet has no bit errors), to pick good bit rates. SoftRate’s novel BER computation works across different wireless environments and hardware without requiring any retraining. SoftRate also uses abrupt changes in the BER estimate to identify interference, enabling it to reduce the bit rate only in response to channel errors caused by attenuation or fading. Our experiments conducted using a software radio prototype show that SoftRate achieves 2x higher throughput than popular frame-level protocols such as SampleRate [4] and RRAA [24]. It also achieves 20% more throughput than an SNR-based protocol trained on the operating environment, and up to 4x higher throughput than an untrained SNR-based protocol. The throughput gains using SoftRate stem from its ability to react to channel variations within a single packet-time and its robustness to collision losses.

Network protocol designers, both at the physical and network level, have long considered interference and simultaneous transmission in wireless protocols as a problem to be avoided. This, coupled with a tendency to emulate wired network protocols in the wireless domain, has led to artificial limitations in wireless networks. In this paper, we argue that wireless protocols can exploit simultaneous transmission to reduce the cost of reliable multicast by orders of magnitude. With an appropriate application interface, simultaneous transmission can also greatly speed up common group communication primitives, such as anycast, broadcast, leader election and others.

Networking over UHF white spaces is fundamentally different from conventional Wi-Fi along three axes: spatial variation, temporal variation, and fragmentation of the UHF spectrum. Each of these differences gives rise to new challenges for implementing a wireless network in this band.

This paper considers the requirements for a scalable, easily manageable, fault-tolerant, and efficient data center network fabric. Trends in multi-core processors, end-host virtualization, and commodities of scale are pointing to future single-site data centers with millions of virtual end points.

To be agile and cost effective, data centers should allow dynamic resource allocation across large server pools. In particular, the data center network should enable any server to be assigned to any service.

This paper presents BCube, a new network architecture specifically designed for shipping-container based, modular data centers. At the core of the BCube architecture is its server-centric network structure, where servers with multi- ple network ports connect to multiple layers of COTS (com- modity on-the-shelf) mini-switches. Servers act as not only end hosts, but also relay nodes for each other. BCube sup- ports various bandwidth-intensive applications by speeding- up one-to-one, one-to-several, and one-to-all traffic patterns, and by providing high network capacity for all-to-all traffic.

Today’s Internet is open and anonymous. While it permits free traffic from any
host, attackers that generate malicious traffic cannot typically be held accountable. In this paper, we present a system called HostTracker that tracks dynamic bindings between hosts and IP addresses by leveraging application-level data with unreliable IDs.

Application-independent Redundancy Elimination (RE), or identifying and removing repeated content from network transfers, has been used with great success for improving network performance on enterprise access links. Recently, there is growing interest for supporting RE as a network-wide service. Such a network-wide RE service benefits ISPs by reducing link loads and increasing the effective network capacity to better accommodate the increasing number of bandwidth-intensive applications. Further, a networkwide RE service democratizes the benefits of RE to all end-to-end traffic and improves application performance by increasing throughput and reducing latencies.

Realizing the full potential of a multi-radio mesh network involves two main challenges: how to assign channels to radios at each node to minimize interference and how to choose high throughput routing paths in the face of lossy links, variable channel conditions and external load.

We present a new routing protocol, pathlet routing, in which networks advertise fragments of paths, called pathlets, that sources concatenate into end-to-end source routes. Intuitively, the pathlet is a highly exible building block, capturing policy constraints as well as enabling an exponentially large number of path choices. In particular, we show that pathlet routing can emulate the policies of BGP, source routing, and several recent multipath proposals.