Abstracts

Bandwidth Allocation for non-responsive Flows with Active Queue Management

This paper addresses the problem of configuring active queue management systems (e.g. WRED and RIO) for service level specifications in Internetworks. In particular, we focus on Assured Forwarding (AF) for non-responsive flows in Differentiated Services networks. The difficulty is to determine the correct queue level thresholds that will result in correct drop rates for various AF precedence levels under any combination of of-fered loads. A new active queue management scheme based on control loop is pro-posed that senses not only queue levels but also rates of queue levels changes and per flow bit rates to converge automatically to an optimal set of trans-mit fractions. The scheme has been implemented and tested on a network processor. Results show that the new active queue management scheme protects assured aggregated flow rates during periods of congestion. For non-responsive traffic the buffer occupancy level remains low during 250% offered load.

A Buffer-Management Scheme for Bandwidth and Delay Differentiation using a Virtual Scheduler

This paper presents a new scalable buffer-management scheme for IP Differentiated Services. The scheme consists of a Dif-ferentiated Random Drop (DRD) algorithm using feedback from a virtual scheduler. DRD choses a queue to perform an early packet drop to avoid congestion according to a specific probability function. First it will be shown that DRD in conjunction with first-come first-served scheduling is able to support relative service differentiation. The virtual scheduler is introduced to enable service differentiation in terms of bandwidth and delay at the same time. A virtual sched-uler runs in parallel to the real scheduler and maintains virtual queue lengths that are being used by the congestion avoidance scheme as a feedback for packet drop decisions. Scheduling packets for transmis-sion is performed by the real scheduler only.

Adaptive End-to-End Quality-of-Service Guarantees in IP Networks using an Active Networking Approach

This paper proposes a framework based on an active networking approach to efficiently link Quality-of-Service (QoS) descriptions from an application point of view with an underlying heteroge-neous IP networking infrastructure. The main goal is to provide building blocks that cooperate to sense the availability of and deploy distinct QoS capabilities in order to accomplish adaptive end-to-end service guarantees. The building blocks needed in a heterogeneous IP network will be introduced and discussed with respect to safety from abuse of total networking bandwidth, CPU, and memory usage. In conjunction with a new safety hierarchy and a sandbox environment for active-code execution, security risks can be bounded to the level of traditional IP forwarding, control, and management. In particular, the problem of QoS-parameter translation to provide end-to-end service guarantees is addressed, and an example using Diffserv, RSVP, and GPRS in a heterogeneous network is given.

Bringing Efficient Advanced Queries to Distributed Hash Tables

Interest in distributed storage is fueled by demand for reliability and resilience combined with ubiquitous availability. Peer-to-peer (P2P) storage networks are known for their decentralized control, self-organization, and adaptation. Advanced searching for documents and resources remains an open problem. The flooding approach favored by some P2P networks is inefficient in resource usage, but more scalable and resource-efficient solutions based on distributed hash tables (DHT) lack in query expressiveness and flexibility. In this paper, we address this issue and introduce new efficient, scalable, and completely distributed methods that strive to keep resource consumption by queries and index information as low as possible. We describe how to improve the handling of multiple subqueries combined through boolean set operators. The need for these operators is intensified by applications to go beyond simple exact keyword matches. We discuss, optimize, and analyze appropriate extensions to support range and prefix matching in DHTs.

Active Queue Management for Fair Bandwidth Allocation of Mixed Responsive and Non-Responsive Traffic Using a Closed-Loop Congestion Control Scheme

Today's known and widely used active queue management (AQM) schemes do not differentiate between packets from responsive (e.g., TCP sessions) and non-responsive traffic (e.g., UDP). This results in further widening the gap of unfair advantage already inherent to non-responsive traffic, as the responsive sender will significantly reduce its future transmit rate as a result of the congestion signals. As a simple work-around, responsive and non-responsive traffic are often assigned distinct AQM parameters. This approach however requires tuning for each traffic class that potentially depends on the current or expected offered load. In other words, responsiveness and TCP-friendliness cannot be estimated easily - not at last due to short-lived TCP sessions. In this paper we propose a closed-loop congestion control (CLCC) scheme on top of an existing AQM scheme to achieve fair bandwidth distribution among concurrent responsive and non-responsive traffic. The new scheme has the advantage that it does not need to estimate the level of responsiveness of traffic. We analyze our scheme on top of an existing rate-based AQM scheme known to approximate max-min fairness, and by means of simulations show that our extension significantly improves fair bandwidth allocation for responsive and non-responsive traffic.

PUPRLE: Predictive Active Queue Management Utilizing Congestion Information

Active Queue Management (AQM) tries to find a delicate balance between two antagonistic Internet queuing requirements: First, buffer space should be maximized to accommodate the possibly huge transient bursts; second, buffer occupation should be minimum so as not to introduce unnecessary end-to-end delays. Traditional AQM mechanisms have been built on heuristics to achieve this balance, and have mostly done so quite well, but often require manual tuning or resulted in slow convergence. In contrast, the \purple{} approach predicts the impact of its own actions on the behavior of reactive protocols and thus on the short-term future traffic without per-flow state. \purple{} allows much faster convergence of the main AQM parameters, at least towards a local optimum, thereby smoothing and minimizing both congestion feedback and queue occupancy. To improve the quality of the prediction, we also passively monitor (using lightweight operations) information pertaining to the amount of congestion elsewhere in the network, for example, as seen by flows traversing this router.

Closed-Loop Congestion Control for Mixed Responsive and Non-Responsive Traffic

Today's known and widely used active queue management (AQM) schemes do not differentiate between packets from responsive (e.g., TCP sessions) and non-responsive traffic (e.g., UDP). This results in further widening the gap of unfair advantage already inherent to non-responsive traffic, as the responsive sender will significantly reduce its future transmit rate as a result of the congestion signals. As a simple work-around, responsive and non-responsive traffic are often assigned distinct AQM parameters. This approach however requires tuning for each traffic class that potentially depends on the current or expected offered load. In other words, responsiveness and TCP-friendliness cannot be estimated easily - not at last due to short-lived TCP sessions. In this paper we propose a closed-loop congestion control (CLCC) scheme on top of an existing AQM scheme to achieve fair bandwidth distribution among concurrent responsive and non-responsive traffic. The new scheme has the advantage that it does not need to estimate the level of responsiveness of traffic. We analyze our scheme on top of an existing rate-based AQM scheme known to approximate max-min fairness, and by means of simulations show that our extension significantly improves fair bandwidth allocation for responsive and non-responsive traffic. The simulation results have been verified with a prototype implementation on the IBM PowerNP 4GS3 network processor.

Creating Advanced Functions on Network Processors: Experience and Perspectives

In this paper, we present five case studies of advanced networking functions and how a network processor (NP) can provide high-performance and flexible support for each of them. We first review the basic NP system architectures, and describe in more detail the IBM PowerNP architecture from a data plane as well as from a control plane point of view. We introduce models for the programmer's views of NPs that facilitate a global understanding of NP software programming. Then, for each case study, we present results from prototypes as well as general considerations that also apply to a wider range of system architectures. Namely, we investigate the suitability of NPs for quality-of-service (active queue management and traffic engineering), header processing (GPRS tunneling protocol), intelligent forwarding (load-balancing without flow disruption), payload processing (active networks code interpretation and just-in-time compilation), and protocol stack termination (SCTP). Finally, we summarize the key features required by each case study, and make concluding remarks regarding the future of NPs.

A new Buffer-Management Scheme for IP Differentiated Services

The sophisticated Quality-of-Service (QoS) demands of research, education and commercial network service providers require new services in current best-effort Internet architecture. The Internet must enable applications that demand specific services to profit from a set of differentiated traffic classes, which support either relative or absolute types of quality of service, or both. This paper focuses on the design of scalable buffer management and queueing strategies in a QoS-enabled Internet. A threshold-based buffer management to be used mainly in core routers is proposed and evaluated. A new buffer management scheme, called Differentiated Random Drop (DRD) scheme, is introduced. Combined with simple first-come, first-served (FCFS) scheduling, the scheme can support differentiated services (Diffserv) that is being standardized by the IETF.

Adaptive End-to-End Quality-of-Service Guarantees in IP Networks using an Active Networking Approach

This paper proposes a framework based on an active net-working approach to efficiently link Quality-of-Service (QoS) descriptions from an application point of view with an underlying heterogeneous IP networking infrastructure. The main goal is to sense the availability of and deploy distinct QoS capabilities in order to accomplish adaptive end-to-end service guarantees. The building blocks needed in a heterogeneous IP network will be introduced and dis-cussed with respect to safety in terms of total networking bandwidth, CPU, and memory usage. In conjunction with a new safety hierarchy and a sandbox environment for active-code execution, security risks are reduced to traditional IP forwarding. In particular, the problem of QoS parameter translation to provide adaptive end-to-end ser-vice guarantees is addressed and an example using Diffserv and RSVP in a heterogeneous network is given.

The Role of Network Processors in Active Networks

Network processors (NPs) implement a balance between hardware and software that addresses the demand of performance and programmability in active networks (AN). We argue that this makes them an important player in the implementation and deployment of ANs. Besides a general introduction into the relationship of NPs and ANs, we describe the power of this combination in a framework for secure and safe capsule-based active code. We also describe the advantages of offloading AN control point functionality into the NP and how to execute active code in the data path efficiently. Furthermore, the paper reports on experiences about implementing active networking concepts on the IBM PowerNP network processor.

Towards High-performance Active Networking

Network processors have been developed to ease the implementation of new network protocols in high-speed routers. Being embedded in network interface cards, they enable extended packet processing at link speed as is required, for instance, for active network nodes. Active network nodes start using network processors for extended packet processing close to the link. The control and configuration of high-performance active network nodes with network processors such that new services can benefit from the additional processing capacity offered is nontrivial. In this paper, we present PromethOS NP which is a modular and flexible router architecture that provides a framework for dynamic service extension by plugins with integrated support of network processors, namely the IBM PowerNP 4GS3 network processor. We briefly introduce the PowerNP architecture in order to show how our active networking framework maps onto this network processor and provide results from performance measurements. Owing to architectural similarities of network processors, we believe that our considerations are also valid for other network processors.

Web caching: How to select your best siblings

The World Wide Web is growing exponentially and already accounts for a big percentage of the traffic in the Internet. Often popular Web servers are overloaded, hot documents travel many times across the same congested links, and receivers experience slow response times. Cache hit rates can be significantly increased by having caches cooperate. In this report we extensively analyze the log entries of the Eurecom Institute and other Squid caches in order to show what hit rates might be achieved with cooperating caches. We also discuss how to chose a parent cache out of several sibling caches based on ping and download round trip times.

Adaptive End-to-End Quality of Service Guarantees in IP Networks

Quality of Service (QoS) in IP networks has made significant advances in the past decade, which resulted in the standardization of QoS frameworks such as Integrated Services and Differentiated Services addressing both relative and absolute service differentiation. Simultaneously, hardware development has led to new fast and efficient QoS mechanisms for traffic differentiation and prevention of the dreaded congestion collapse. The hardware itself shifted from simple network interface cards to interfaces built with application-specific integrated circuits, leading to the introduction of application-specific instruction-set processors, or in other words, network processors. This evolution allowed the development of new, more sophisticated algorithms for QoS support.

However, it can be safely stated today that QoS support still is rarely used. The increasing gap between the description of QoS parameters and the capabilities of the underlying hardware, which becomes even more important when traversing heterogeneous networks consisting of networking equipment from different manufacturers each having different capabilities, is one of the reasons for this. The lack of interoperability between QoS mechanisms cannot be solved solely on the protocol level. Moreover, QoS requirements differ for each type of application; a one-size-fits-all solution is not satisfactory, and, depending on the underlying QoS mechanisms, mapping these requirements to them is difficult. Therefore QoS deployment is an extremely complex task.

This thesis addresses existing and new QoS mechanisms whose integration, interaction, and interoperation are not solvable on the protocol level to build adaptive end-to-end QoS guarantees. To do so, a safe, efficient, and adaptive framework using active networks (SeaFan) proposed that is flexible enough to address certain QoS tasks even in the data path. Safety and security requirements are ensured by the combination of a byte-code language, the introduction of the resource-bound vector, the definition of a safety hierarchy, and a sandbox environment. The minimum set of functionalities in a node model supporting the active-networking framework is specified. These functionalities are capable of acting locally on the nodes and globally with respect to the end-to-end service. The concept of having several QoS capabilities running at the same time is explicitly allowed.

New QoS mechanisms are introduced that address relative and absolute bandwidth differentiation with responsive and non-responsive protocols, including packet-drop-rate differentiation. Scalability is ensured by the aggregation of flows and the careful limitation of the distribution of information, even when acting on the end-to-end service from within the network.

The excellent performance of the new QoS mechanisms has been shown by means of simulations in ns-2, and the feasibility of and the benefits from the existence of a programmable networking infrastructure have been shown in a reference implementation on the IBM PowerNP 4GS3. Further optimization methods using just-in-time compilation have revealed additional potential in byte-coded active networks. The combination of the active-networking framework and the QoS mechanism enables the deployment of adaptive end-to-end services over heterogeneous IP networks.