Wonsang Song

NetServ Framework Design and Implementation 1.0

Eyeball ISPs today are under-utilizing an important asset: edge routers. We present NetServ, a programmable node architecture aimed at turning edge routers into distributed service hosting platforms. This allows ISPs to allocate router resources to content publishers and application service providers motivated to deploy content and services at the network edge. This model provides important benefits over currently available solutions like CDN. Content and services can be brought closer to end users by dynamically installing and removing custom modules as needed throughout the network. Unlike previous programmable router proposals which focused on customizing features of a router, NetServ focuses on deploying content and services. All our design decisions reflect this change in focus. We set three main design goals: a wide-area deployment, a multi-user execution environment, and a clear economic benefit. We built a prototype using Linux, NSIS signaling, and the Java OSGi framework. We also implemented four prototype applications: ActiveCDN provides publisher-specific content distribution and processing; KeepAlive Responder and Media Relay reduce the infrastructure needs of telephony providers; and Overload Control makes it possible to deploy more flexible algorithms to handle excessive traffic.

Using IM and SMS for emergency text communications

Currently, text communication cannot be used to ask for help in emergency situations. Even in the Next Generation 9-1-1 system, an IP/SIP-based emergency communication system, there has been no investigation into how text communications such as Instant Messaging (IM) and Short Message Service (SMS) can be integrated. We identify the technical challenges in the integration of IM and SMS networks with the NG9-1-1 system, and propose a solution for each challenge. We also describe a working prototype system using our approach.

Polygon Simplification for Location-Based Services Using Population Density

An important group of location-based services (LBS), including 9-1-1 service, rely on the mapping between a users location and a service boundary in order to select the appropriate service provider. In such cases, mobile clients can cache the mapping information to reduce service latency and server load. However, caching such a mapping can be burdensome on mobile devices because representing the polygon that defines a service boundary requires a large amount of data. We present GeoPS-PD, a polygon simplification algorithm designed for LBS applications. Unlike existing algorithms, GeoPS-PD never produces a false positive, is tunable at runtime for the desired balance between target polygon size and area coverage, and optionally takes into account the population density. We demonstrate the efficacy of GeoPS-PD using the US state boundary data. For New York, GeoPS-PD produces a simplified polygon which is only 3% of the original size, yet covers 95% of the original area, and makes the LBS queries 3.17 times faster.

MOSAIC: Stateless mobility for HTTP-based applications

We present a mobility solution for stateless applications, where the mobile host can change its IP address as well as the content servers used by ongoing client sessions. This allows content retrieval to always use the locally optimal source when the host moves between networks. We refer to this approach as “stateless mobility” since neither the network nor the content servers hold mobility-related state information. Our mobility solution, referred to as MOSAIC, is applied to HTTP sessions using GET method invocation, which represent a large fraction of mobile Internet traffic. By moving MOSAIC underneath the socket interface, we create a generic application-independent feature. We realized a lightweight implementation using an L3 packet filter, which promises easy portability to other platforms. MOSAICs overall concept is evaluated via measurements using public Internet services.

Improving the Vertical Accuracy of Indoor Positioning for Emergency Communication

The emergency communication systems are undergoing a transition from the PSTN-based legacy system to an IP-based next generation system. In the next generation system, GPS accurately provides a user’s location when the user makes an emergency call outdoors using a mobile phone. Indoor positioning, however, presents a challenge because GPS does not generally work indoors. Moreover, unlike outdoors, vertical accuracy is critical indoors because an error of few meters will send emergency responders to a different floor in a building. This paper presents an indoor positioning system which focuses on improving the accuracy of vertical location. We aim to provide floor-level accuracy with minimal infrastructure support. Our approach is to use multiple sensors available in today’s smartphones to trace users’ vertical movements inside buildings. We make three contributions. First, we present the elevator module for tracking a user’s movement in elevators. The elevator module addresses three core challenges that make it difficult to accurately derive displacement from acceleration. Second, we present the stairway module which determines the number of floors a user has traveled on foot. Unlike previous systems that track users’ foot steps, our stairway module uses a novel landing counting technique. Third, we present a hybrid architecture that combines the sensor-based components with minimal and practical infrastructure. The infrastructure provides initial anchor and periodic corrections of a user’s vertical location indoors. The architecture strikes the right balance between the accuracy of location and the feasibility of deployment for the purpose of emergency communication.

NetServ: Reviving Active Networks

In 1996, Tennenhouse and Wetherall proposed active networks, where users can inject code modules into network nodes. The proposal sparked intense debate and followon research, but ultimately failed to win over the networking community. Fifteen years later, the problems that motivated the active networks proposal persist. We call for a revival of active networks. We present NetServ, a fully integrated active network system that provides all the necessary functionality to be deployable, addressing the core problems that prevented the practical success of earlier approaches. We make the following contributions. We present a hybrid approach to active networking, which combines the best qualities from the two extreme approaches– integrated and discrete. We built a working system that strikes the right balance between security and performance by leveraging current technologies. We suggest an economic model based on NetServ between content providers and ISPs. We built four applications to illustrate the model.