Sarit Mukherjee

A dual encryption protocol for scalable secure multicasting

We propose a dual encryption protocol for scalable secure multicasting. Multicasting is a scalable solution for group communication. It however poses several unique security problems. We use hierarchical subgrouping to achieve scalability. Third-party hosts or members of the multicast group are designated as subgroup managers. They are responsible for secret key distribution and group membership management at the subgroup level. Unlike existing secure multicast protocols, our protocol need not trust the subgroup managers with the distribution of data encryption keys. The dual encryption protocol proposed in this paper distributes encrypted data encryption keys via subgroup managers. We also present a classification of the existing secure multicast protocols, compare their relative merits and show the advantages of our protocol.

Carry-over round robin: a simple cell scheduling mechanism for ATM networks

We propose a simple mechanism named carry-over round robin (CORR) for scheduling cells in asynchronous transfer mode networks. We quantify the operational complexity of CORR scheduling and show that it is comparable to that of a simple round-robin scheduler. We then show that, albeit its simplicity, CORR is very competitive with much more sophisticated and significantly more complex scheduling disciplines in terms of performance. We evaluate the performance of CORR using both analysis and simulation, We derive analytical bounds on the worst case end-to-end delay achieved by a CORR scheduler for different traffic arrival patterns. Using traffic traces from MPEG video streams, we compare the delay performance of CORR with that of packet-by-packet generalized processor sharing (PGPS) and stop-and-go (SG). Our results show that, in terms of delay performance, CORR compares favorably with both PGPS and SG. We also analyze the fairness properties of CORR and show that it achieves near perfect fairness.

Multiclass transaction scheduling and overload management in firm real-time database systems

Real-Time Database Systems (RTDBSs), have attracted considerable amount of research attention in the recent past and a number of important applications have been identified for such systems, such as telecommunications network management, automated air traffic control, automated financial trading, process control and military command and control systems. Due to the rapidity of change of the system state in such applications, as well as the inherent complexities in controlling such systems (which result in frequent violation of consistency requirements and consequent repeated firings of control actions), it is likely that the transaction load in these systems would be fairly high. Thus RTDBSs need to be equipped with overload management mechanisms. Unfortunately overload management has been a fairly neglected area in real-time systems research in general and real-time database research in particular. In this paper we introduce Adaptive Access Parameter (AAP), a scheduling mechanism for multiclass transactions in real-time database systems that employs an explicit admission control policy to manage overload as well as system bias towards particular transaction classes. We show the theoretical underpinnings behind AAP and then report a thorough performance study that demonstrates AAPs substantial superiority over current algorithms with regard to performance metrics as well as computational overhead.

Multirate scheduling of VBR video traffic in ATM networks

One of the major attractions of asynchronous transfer mode (ATM) networks for transporting bursty video traffic is its ability to exploit the multiplexing gains of packet switching while providing quality of service guarantees. Unfortunately, most of the multiplexing mechanisms proposed in the literature fail to exploit the multiplexing gains of ATM. We propose a multirate service mechanism that allows a session to be served at different rates at different times. Applications generating bursty data, such as variable bit-rate (VBR) video, can take advantage of multirate service by requesting a high rate of service for brief periods of bursty arrivals and a much lower rate of service for all other times. Consequently, the applications can improve their delay performance without reserving a high bandwidth for the entire duration of the sessions. Furthermore, the scheduler can multiplex the peaks and the lulls in service rates of different sessions and improve the utilization of the system. Using MPEG video traces from a number of applications, we show that multirate servers outperform single-rate PGPS (packet-by-packet generalized processor sharing) servers and CBR (constant bit-rate) servers in terms of number of connections admitted, while providing the same level of service guarantees. We also investigate the performance of multirate service when service quality need not be guaranteed. We refer to this as predictive service. We propose a measurement-based admission control procedure for predictive service, and show that it helps increase the size of the admissible region even further.

A random early demotion and promotion marker for assured services

The differentiated services (DiffServ) model, proposed to evolve the current best-effort Internet to a quality-of-service-aware Internet, provides packet level service differentiation on a per-hop basis. The end-to-end service differentiation may be provided by extending the per-hop behavior over multiple network domains through service level agreements between domains. The edge routers of each of the domains monitor the aggregate flow of the incoming packets and demote packets when the aggregate incoming traffic exceeds the negotiated interdomain service agreement. A demoted packet may encounter other edge routers on its path that have sufficient resources to route the packet with its original marking. In this paper, we propose a random early demotion and promotion (REDP) technique that works at the aggregate traffic level and allows (1) fair demotion of packets belonging to different flows, and (2) easy and fair detection and promotion of the demoted packets. Using early and random decisions on packets REDP ensures fairness in promotion and demotion. It uses a three color marking mechanism, reserving one color fur differentiating between a demoted packet and a packet with the original out-of-profile marking. We experiment with the proposed REDP scheme using the ns2 simulator for both TCP and UDP streams. The results demonstrate the fairness of REDP scheme in demoting and promoting packets. Furthermore, we show a variety of results that demonstrates that REDP provides better assured services compared to the previously proposed RIO scheme with or without the provision of promotion.

On guaranteed delivery of time-critical messages in DQDB

This paper addresses the problem of guaranteed delivery of messages with hard deadlines in a DQDB network. The authors present a cyclic reservation scheme capable of allocating bandwidth with any arbitrary granularity and provide deterministic delay guarantees. They propose two implementations of the allocation scheme within the framework of DQDB medium access control protocol. The proposed implementations are very simple, incur minimal overhead and require only minor changes in the adopted standard.<<ETX>>

A bandwidth allocation scheme for time constrained message transmission on a slotted ring LAN

We study the problem of transmitting time constrained synchronous messages in a slotted ring based local area network, carrying synchronous and asynchronous traffic. A bandwidth allocation scheme for synchronous messages is developed on top of a media access control protocol that assigns preemptive priority to synchronous traffic over asynchronous traffic. We derive sufficient conditions for schedulability of time critical synchronous messages and show that the scheme achieves high levels of schedulable utilization. A slot access protocol is proposed for synchronous streams that implements the allocation scheme with minimal additional overhead and loss of schedulable utilization. The protocol is distributed in the sense that any node can locally determine if it can use a slot, without exchanging any explicit messages with other nodes.<<ETX>>

An active buffer management technique for providing interactive functions in broadcast video-on-demand systems

Multicast delivery is an efficient approach to the provision of a video-on-demand (VoD) service. Interacting with the video stream is a desirable feature for users. However, it is a challenging task to provide the functionality in the multicast environment because a lot of users share multicast delivery channels. In this paper, we propose an active buffer management technique to provide interactive functions in broadcast VoD systems. In our scheme, the client can selectively prefetch segments from broadcast channels based on the observation of the play point in its local buffer. The content of the buffer is adjusted in such a way that the relative position of the play point is kept in the middle part of the buffer. Our simulations show that the active buffer management scheme can implement interactive actions through buffering with a high probability in a wide range of user interaction levels.

Supporting MPEG video transport on DOCSIS-compliant cable networks

A novel quality of service (QoS) scheduling mechanism suitable for transporting variable bit rate video in the upstream direction over a DOCSIS (data over cable system interface specification)-compliant cable network is presented. It is shown, via simulation using real life video traces, that the proposed scheduling service provides significant improvements as compared to the existing DOCSIS QoS scheduling services, with regard to bandwidth utilization and latency distribution. The proposed scheduling service is also applicable to transport integrated services over the Internet and can be utilized by other emerging multimedia applications, where data are bursty in nature and variable in bit rate.

A scalable distributed multimedia file system using network attached autonomous disks

Repositories for multimedia data differ from those for traditional text-based data both in terms of storage space and streaming bandwidth requirements. The file systems used in the multimedia environment need to support large volumes and high bandwidth. In this paper, we propose a novel scalable distributed file system built using autonomous disks. Autonomous disks are attached directly to the network and are able to perform lightweight processing. We discuss different ways to realize an autonomous disk, and describe a prototype implementation on a Linux platform using PC-based hardware. We present the design methodology and a prototype Linux-based implementation of the distributed file system that supports such disks. We detail experimental results on the performance of the proposed file system prototyped using autonomous disks. We show that the performance of the file system scales linearly with the number of disks and the number of clients. The file systems performance is much superior to NFS running on the same hardware platform, and it can deliver higher raw disk bandwidth to the applications. We also show that the file system can provide strict bandwidth guarantees for multimedia streams.