Amitabha Banerjee

Fair queueing with service envelopes (FQSE): a cousin-fair hierarchical scheduler for subscriber access networks

In this paper, we propose and investigate the characteristics of a fair queueing with service envelopes (FQSE) algorithm-a hierarchical fair-share scheduling algorithm for access networks based on a remote scheduling system such as Ethernet passive optical networks (EPON) or cable TV network. FQSE is designed to overcome the limiting factors of a typical remote scheduling system such as large control-plane delay, limited control-plane bandwidth, and significant queue switch-over overhead. The algorithm is based on a concept of service envelope-a function representing the fair allocation of resources based on a global network condition called satisfiability parameter (SP). We define properties of cousin-fairness and sibling-fairness and show the FQSE to be cousin-fair. FQSE is unique in that it is the only hierarchical algorithm that is simultaneously cousin-fair. Furthermore, we show the necessary techniques to adapt FQSE to variable-sized packet-based networks. We analyze FQSE performance in EPON serving 1024 independent queues and demonstrate FQSEs ability to provide guaranteed bandwidth to each queue and to share the excess bandwidth fairly.

Control Plane for Advance Bandwidth Scheduling in Ultra High-Speed Networks

A control-plane architecture for supporting advance reservation of dedicated bandwidth channels on a switched network infrastructure is described including the front-end web interface, user and token management scheme, bandwidth scheduler, and signaling daemon. A path computation algorithm for bandwidth scheduling is proposed based on an extension of Bellman-Ford algorithm to an algebraic structure on sequences of disjoint non-negative real intervals. An implementation of this architecture for UltraScience Net is briefly described.

Algorithms for Integrated Routing and Scheduling for Aggregating Data from Distributed Resources on a Lambda Grid

In many e-science applications, there exists an important need to aggregate information from data repositories distributed around the world. In an effort to better link these resources in a unified manner, many lambda-grid networks, which provide end-to-end dedicated optical-circuit-switched connections, have been investigated. In this context, we consider the problem of aggregating files from distributed databases at a (grid) computing node over a lambda grid. The challenge is (1) to identify routes (that is, circuits) in the lambda-grid network, along which files should be transmitted, and (2) to schedule the transfers of these files over their respective circuits. To address this challenge, we propose a hybrid approach that combines offline and online scheduling. We define the Time-Path Scheduling Problem (TPSP) for offline scheduling. We prove that TPSP is NP-complete, develop a Mixed Integer Linear Program (MILP) formulation for TPSP, and then propose a greedy approach to solve TPSP because the MILP does not scale well. We compare the performance of the greedy approach on a few representative lambda-grid network topologies. One key input to the offline schedule is the file transfer time. Due to dynamics at the receiving end host, which is hard to model precisely, the actual file transfer time may vary. We first propose a model for estimating the file transfer time. Then, we propose online reconfiguration algorithms so that as files are transferred, the offline schedule may be modified online, depending on the amount of time that it actually took to transfer the file. This helps in reducing the total time to transfer all the files, which is an important metric. To demonstrate the effectiveness of our approach, we present results on an emulated lambda-grid network testbed.

Fair sharing using dual service-level agreements to achieve open access in a passive optical network

The Passive Optical Network (PON) is an attractive solution for high-bandwidth access networks. In the context of a broadband access network, the term open access implies the ability of multiple service providers to share the deployed access network infrastructure to make services available to the end users. Multiple services may thereby be delivered over a shared access channel. Open access requires fairness in terms of throughput, delay, jitter, and other network parameters in the access channel among the sharing entities, namely service providers and end users. Since the traffic in an access network is very bursty, an access network may be frequently subjected to high loads for certain durations of time. Meeting the above fairness requirements under such conditions is therefore very challenging. In this study, we first motivate the problem of meeting fairness requirements simultaneously to both service providers and users, which are located at opposite ends of an access channel. We then investigate the importance of two different sets of Service-Level Agreements (SLAs), which we call Dual SLAs. After formulating a mathematical model, we propose an efficient scheduling algorithm to meet Dual SLAs which is based on the well-known concept of max-min fairness. We then demonstrate the effectiveness of our proposed algorithm through simulations using a discrete-event-simulator-based PON set-up, which compares the fairness of the Dual-SLA scheduling algorithm with that of other traditional fair queuing algorithms such as Deficit Round Robin (DRR)

A time-path scheduling problem (TPSP) for aggregating large data files from distributed databases using an optical burst-switched network

The problem of aggregating large data files from distributed databases and address the corresponding challenges involved from a network architecture perspective is considered. We model this problem as one of identifying a time-path schedule (TPS) in a graph representation of the network. We prove that the TPS problem (TPSP) is NP-complete. We then propose a mixed integer linear programming (MILP)-based approach and three heuristics longest-file-first (LFF), disjoint-paths (DP), and most-distant-file-first (MDFF) - to solve TPSP.

SLA-Aware Protocol for Efficient Tunable Laser Utilization to Support Incremental Upgrade in Long-Reach Passive Optical Networks

With the advances in optical technology, the span of a broadband access network using passive optical network (PON) technology can be increased from todays standard of 20 km to 100 km or higher and thereby serve many more users. Such an extended-reach PON is known as a SuperPON in the literature, and we call it a long-reach PON (LR-PON). A major challenge in LR-PON is how to utilize the network resources (e.g., wavelengths, lasers, etc.) effectively to meet the increased bandwidth requests from the expanding base of users. We propose a new and efficient protocol to achieve a high utilization of tunable lasers across different user groups in LR-PON. To accommodate downstream bursty traffic and provide quality of service in the user-specified service-level agreements (SLAs), the protocol integrates our proposed SLA-aware bandwidth allocation scheme based on flow scheduling. Illustrative numerical results demonstrate the protocols advantage to support incremental upgrade of bandwidth with increasing user bandwidth requests and to provide a user with an SLA that guarantees a number of streaming flows with average bandwidth and maximum delay guarantee (i.e., 5 ms), as well as data flows with average bandwidth specifications.

A Protocol for Efficient Tunable Laser Utilization to Support Incremental Upgrade in a WDM-PON

We present a novel protocol to achieve better utilization of tunable lasers across different user groups in a WDM-PON. We demonstrate the protocols advantage to support incremental upgrade of bandwidth with increasing user bandwidth request.

Fair sharing using service-level agreements (SLAs) for open access in EPON

Ethernet passive optical networks (EPONs) are an attractive solution for meeting the broadband access requirements of residential users. Open access is a regulatory requirement in many countries which mandates that the access infrastructure must be open to various service providers for free competition. Thus, different service providers may cater services to same or different users using the same shared access channel. Open access demands fairness in the use of network resources among sharing entities, namely service providers and end users. In this study, we investigate scheduling algorithms for fair bandwidth sharing in the context of open access for EPONs.

Introspective end-system modeling to optimize the transfer time of rate based protocols

The transmission capacity of todays high-speed networks is often greater than the capacity of an end-system (such as a server or a remote client) to consume the incoming data. The mismatch between the network and the end-system, which can be exacerbated by high end-system workloads, will result in incoming packets being dropped at different points in the packet receiving process. In particular, a packet may be dropped in the NIC, in the kernel ring buffer, and (for rate based protocols) in the socket buffer. To provide reliable data transfers, these losses require retransmissions, and if the loss rate is high enough result in longer download times. In this paper, we focus on UDP-like rate based transport protocols, and address the question of how best to estimate the rate at which the end-system can consume data which minimizes the overall transfer time of a file. We propose a novel queueing network model of the end-system, which consists of a model of the NIC, a model of the kernel ring buffer and the protocol processing, and a model of the socket buffer from which the application process reads the data. We show that using simple and approximate queueing models, we can accurately predict the effective end-system bottleneck rate that minimizes the file transfer time. We compare our protocol with PA-UDP, an end-system aware rate based transport protocol, and show that our approach performs better, particularly when the packet losses in the NIC and/or the kernel ring buffer are high. We also compare our approach to TCP. Unlike in our rate based scheme, TCP invokes the congestion control algorithm when there are losses in the NIC and the ring buffer. With higher end-to-end delay, this results in significant performance degradation compared to our reliable end-system aware rate based protocol.

Shared-Wavelength WDM-PON Access Network --- Bursty Traffic Accommodation and User-defined SLA Support

We investigate the shared-wavelength WDM-PON architecture which accommodates bursty downstream traffic. Based on the architecture, the proposed flow-scheduling algorithm can support user-specified service level agreements (SLAs), especially under high traffic load. Illustrative results demonstrate that the new architecture can provide a user with a number of streaming flows with bandwidth and maximum delay guarantees, as well as average bandwidth guarantee for data flows, as specified by the user-defined SLA.