Rosen Sharma

Issues and trends in router design

Future routers must not only forward packets at high speeds, but also deal with nontrivial issues such as scheduling support for differential services, heterogeneous link technologies, and backward compatibility with a wide range of packet formats and routing protocols. The authors outline the design issues facing the next generation of backbone, enterprise, and access routers. The authors also present a survey of advances in router design, identifying important trends, concluding with a selection of open issues.

ThinStreams: an architecture for multicasting layered video

Multicast is a common method for distributing audio and video over the Internet. Since receivers are heterogeneous in processing capability, network bandwidth, and requirements for video quality, a single multicast stream is usually insufficient. A common strategy is to use layered video coding with multiple multicast groups. In this scheme, a receiver adjusts its video quality by selecting the number of multicast groups, and thereby video layers, it receives. Implementing this scheme requires the receivers to decide when to join a new group or leave a subscribed group. This paper presents a new solution to the join/leave problem using ThinStreams. In ThinStreams, a single video layer is multicast over several multicast groups, each with identical bandwidth. ThinStreams separates the coding scheme (i.e., the video layers) from control (i.e., the multicast groups), helping to bound network oscillations caused by receivers joining and leaving high bandwidth multicast groups. This work evaluates the join/leave algorithms used in ThinStreams using simulations and preliminary experiments on the MBONE. It also addresses fairness among independent video broadcasts and shows how to prevent interference between them.

The ENTRAPID protocol development environment

As Internet services rapidly become an essential part of the global infrastructure, it is necessary for the protocols underlying these services to be robust and fail-safe. To achieve this goal, protocol developers should be able to design, implement, simulate, visualize, and validate their work in a protocol development environment before deployment in the field. We describe the ENTRAPID protocol development environment, outline its implementation, and present a performance evaluation.

Environments for active networks

Active networks have the potential to solve three fundamental problems in traditional (and current) networks: (a) service extensibility, (b) rapid reaction to network events, and (c) obtaining a disaggregated view of network state. Traditional networks expose a fixed set of network services, which are difficult to modify or customize. In contrast, active networks allow service extensibility by providing an environment for execution of nearly arbitrary agents (or applets) within the network. Such a framework can be used to build application level gateways for multimedia processing, such as transcoding and fusion/merging, within the network. A second advantage of active networks is their ability to rapidly respond to asynchronous network events because control algorithms can be co-located with network elements. Finally, traditional networks achieve scaling by aggressively aggregating network state. Applets embedded in the network see the disaggregated state, allowing finer-grained control. The authors describe some preliminary ideas in exploiting an active network framework for next generation networks. They support ideas by describing their experience in using an active network framework for network management.

Signaling and operating system support for native-mode ATM applications

Applications communicating over connectionless networks, such as IP, cannot obtain per-connection Quality of Service (QoS) guarantees. In contrast, the connection-oriented nature of the ATM layer and its per-virtual-circuit QoS guarantees are visible to a native-mode ATM application. We describe the design and implementation of operating system and signaling support for native-mode applications, independent of the semantics of the protocol layers or of the signaling protocol. The work was done in the context of a Unix-like operating system and the Xunet 2 wide-area high-speed ATM network. The IPC-based interface between an application and the signaling entity allows processes to request parameterized virtual circuits, and the signaling-kernel interface allows resources to be reclaimed from prematurely terminating processes. We also built a simple encapsulation layer over raw IP that allows any host with IP access to send AAL frames into the wide-area network with little performance degradation. Our design makes it simple to port existing TCP/IP socket applications to a native-mode ATM protocol stack and also enables interoperation of existing IP networks with our ATM network. Our experience has been positive - the design is robust, easily extendible and scales well with the number of open connections.