Ladan Gharai

Packet reordering, high speed networks and transport protocol performance

We performed end-to-end measurements of UDP/IP flows across an Internet backbone network. Using this data, we characterized the packet reordering processes seen in the network. Our results demonstrate the high prevalence of packet reordering relative to packet loss, and show a strong correlation between packet rate and reordering on the network we studied. We conclude that, given the increased parallelism in modern networks and the demands of high performance applications, new application and protocol designs should treat packet reordering on an equal footing to packet loss, and must be robust and resilient to both in order to achieve high performance

Experiences with High Definition Interactive Video Conferencing

We review the design and implementation of UltraGrid, a new high definition video conferencing system, and present some experimental results. UltraGrid was the first system to support gigabit rate high definition interactive video conferencing on commodity systems and networks, and we present measurements to illustrate behavior of production networks subject to such real time traffic. We illustrate the benefits of hybrid IP/provisioned optical networks over best effort IP networks for this class of traffic, and motivate the development of congestion control algorithms for interactive conferencing on best effort IP networks

Rtp and the Datagram Congestion Control Protocol

We describe how the new datagram congestion control protocol (DCCP) can be used as a bearer for the real-time transport protocol (RTP) to provide a congestion controlled basis for networked multimedia applications. This is a step towards deployment of congestion control for such applications, necessary to ensure the future stability of the best-effort network if high-bandwidth streaming and IPTV services are to be deployed outside of closed QoS-managed networks

IPsec-Protected Transport of HDTV over IP

Bandwidth-intensive applications compete directly with the operating systems network stack for CPU cycles. This is particularly true when the stack performs security protocols such as IPsec; the additional load of complex cryptographic transforms overwhelms modern CPUs when data rates exceed 100 Mbps. This paper describes a network-processing accelerator which overcomes these bottlenecks by offloading packet processing and cryptographic transforms to an intelligent interface card. The system achieves sustained 1 Gbps host-to-host bandwidth of encrypted IPsec traffic on commodity CPUs and networks. It appears to the application developer as a normal network interface, because the hardware acceleration is transparent to the user. The system is highly programmable and can support a variety of offload functions. A sample application is described, wherein production-quality HDTV is transported over IP at nearly 900 Mbps, fully secured using IPsec with AES encryption.

Scaling video conferencing through spatial tiling

We describe an approach to scaling video conferencing, with the use of active agents. Such agents tileNvideo frames into one, by modification of their respective meta-data and adjustment of their video frame rate if necessary. The spatial tiling agents are located within a network, and participants in the session unicast video to the “closest” agent. The agent then multicast the tiled video to the group of all participants. Results show that spatial tiling increases the ability of the end-user to receive large numbers of video streams and reduces network load both in terms of bandwidth and in packets per second. The result is a significant scaling boost to video conferencing systems.

Holographic and 3D Teleconferencing and Visualization: Implications for Terabit Networked Applications

We discuss the evolution of teleconferencing and networked visualization applications to support 3-dimensional display technologies. The implications of a continuation of Moores law, coupled with constraints on device clock rate due to power consumption, suggest that future end system and network architectures will become increasingly parallel in nature. Given this, we review trends in programming language design that will ease development of highly concurrent systems, and suggest how network transport protocols might evolve to support them.