Biswajit Nandy

Bandwidth assurance issues for TCP flows in a differentiated services network

Much industry attention has been focused on providing differentiated levels of service to users on IP networks. One such proposal is the RIO scheme proposed by Clark (see ACM Transactions on Networking, 1998 ). RIO is an extension of the RED algorithm that relies on a differentiated drop treatment during congestion to cause different levels of service. The end result of differentiated dropping of packets during congestion is differentiated throughput rates for end-users. The IETFs Diffserv Working Group has recently standardized a PHB (per hop behaviour) that is based on a differentiated drop scheme-assured forwarding (AF). This paper raises issues with providing bandwidth assurance for TCP flows in a RIO-enabled differentiated services network. The main contribution is a detailed experimental study of five different factors that impact throughput assurances for TCP and UDP flows in such a network. Our study demonstrates that these factors can cause different throughput rates for end-users in spite of having contracted identical service agreements.

Intelligent Traffic Conditioners for Assured Forwarding Based Differentiated Services Networks

Issues related to bandwidth assurance in Assured Forwarding based Differentiated Services (Diffserv) networks have been discussed in recent research papers [7][8][11]. Some of the factors that can bias bandwidth assurance are Round Trip Time (RTT), UDP/TCP interaction and different target rates. The bias due to these factors needs to be mitigated before bandwidth assurance for a paying customer can be articulated in Service Level Agreements (SLAs). This paper proposes intelligent traffic conditioning approaches at the edge of the network to mitigate the effect of Round Trip Time, UDP/TCP interactions, and different target rates. The simulation results show a significant improvement in bandwidth assurance with intelligent traffic conditioning. The limitation of the proposed solutions is that they require communication between edge devices. In addition, these solutions are not applicable for a one-to-any network topology.

Security advances and challenges in 4G wireless networks

This paper presents a study of security advances and challenges associated with emergent 4G wireless technologies. The paper makes a number of contributions to the field. First, it studies the security standards evolution across different generations of wireless standards. Second, the security-related standards, architecture and design for the LTE and WiMAX technologies are analyzed. Third, security issues and vulnerabilities present in the above 4G standards are discussed. Finally, we point to potential areas for future vulnerabilities and evaluate areas in 4G security which warrant attention and future work by the research and advanced technology industry.

Source routed forwarding with software defined control, considerations and implications

The research introduced in this paper focuses on controller scalability and performance issues in Software-Defined Networks (SDNs), and discusses a new routing scheme that leverages a variation of Source Routing for use in OpenFlow-based networks. The research aims to reduce the state needed to be distributed to the network devices by the controller(s) in SDNs, and in return improve the scale, convergence time, fault tolerance and cost of such network architectures.

Using TCP models to understand bandwidth assurance in a Differentiated Services network

In this paper, a comprehensive analytical model to predict the bandwidth achieved by aggregates of TCP flows in a DiffServ network is presented. The model predicts achieved bandwidth in three different cases: an over-provisioned network, an under-provisioned network, and a near-provisioned network. In developing the model, we ensure that all parameters are measurable using standard tools and information available from routers and network management tools in todays networks. Simulation was used to establish the validity of the model and understand its scope of applicability and limitations. Using the model, we explain why achieved excess bandwidth is based on factors such as RTT, packet size, and CIR. Finally, we present a novel extension of the model to predict the bandwidth of TCP flows in a Diffserv network with multiple congested nodes.

Aggregate flow control: improving assurances for differentiated services network

The differentiated services architecture is a simple, but novel, approach for providing service differentiation in an IP network. However, there are various issues to be addressed before any sophisticated end-to-end services can be offered. This work proposes an aggregate flow control (AFC) technique with a Diffserv traffic conditioner to improve the bandwidth and delay assurance of differentiated services. A prototype has been developed to study the end-to-end behavior of customer aggregates. In particular, this new approach improves performance in the following manner: (1) fairness issues among aggregated customer traffic with different number of micro-flows in an aggregate, interaction of non-responsive traffic (UDP) and responsive traffic (TCP), and the effect of different packet sizes in aggregates; (2) improved transactions per second for short TCP flows; and (3) reduced inter-packet delay variation for streaming UDP traffic. Experiments are also performed in a topology with multiple congestion points to show an improved treatment of conformant aggregates, and the ability of AFC to handle multiple aggregates and differing target rates.

Load balancing for multicast traffic in SDN using real-time link cost modification

In this paper we propose an approach for applying traffic load balancing to multicast traffic through real-time link cost modification in a software defined network (SDN) controller. We present an SDN controller architecture supporting traffic monitoring, group management, and multicast traffic routing. An implemented prototype is described, and this prototype is used to implement shortest path multicast routing techniques which make use of the real-time state of traffic flows in the network. This prototype is evaluated through experimentation in Mininet emulated wide area networks. Evaluation is presented in terms of resulting network performance metrics focusing on the distribution of traffic flows. Our results demonstrate that real-time modification of links costs produces statistically significant improvements in traffic distribution metrics, with an average improvement of up to 52.8% in traffic concentration relative to shortest-path routing. This indicates that SDN enables the use of real-time modification of link cost functions as an effective technique for implementing traffic load balancing for multicast traffic.

An empirical study of today's Internet traffic for differentiated services IP QoS

The IETF is currently focused on differentiated services (Diffserv) as the architecture to provide quality of service in IP networks (IP-QoS). The Diffserv architecture consists of two key components: traffic conditioning at the edge and per hop behaviour (PHB) at the core. Traffic conditioners are realized through various building blocks such as classifier, meter, marker, policer, etc. This paper focuses on an empirical study of pre-Diffserv Internet traffic. We use the results of the study to understand design choices for some of the Diffserv architecture building blocks. The primary contribution is an investigation into the usage of the type-of-service (TOS) field marking to understand if its usage justifies the IETF Diffserv Working Groups (WGs) standardization of class selector PHB on the basis of backwards compatibility with the TOS octet. A second contribution is a detailed examination of Internet and intranet traffic traces to understand issues related to packet classification in Diffserv edge routers. In particular, we study the need for classifiers that maintain per-flow state and utilize techniques based on inspection of layer-7 header/payload.

Exploring source routed forwarding in SDN-based WANs

Software-Defined Networking has been gaining increasing attention in both the research and the industry communities. Separating the control and data planes has brought many advantages such as greater control plane programmability, more vendor independence, possibility of network virtualization, lowered operational expenses, etc. SDN deployments are possible in a variety of contexts: Enterprise networks, WANs and networks connecting data centers. The realization and operation of an SDN requires the inclusion of a central controller. SDN however raises several concerns for WANs including performance limitations due to the larger propagation delays of control information to and from the controller, the increased work load due to a larger number of network elements and concerns as to performance impacts related to the controller placement. This paper attempts to address some of these issues by examining the effects of using source routing as an alternative to hop by hop in an Internet2 SDN-based WAN production deployment. Our analysis shows that source routing can bring significant gains in SDN convergence performance in WAN environments and reduce the sensitivity in performance due to controller placement.

A Connectionless Approach to Providing QoS in IP Networks

The attempt to provide QoS in IP networks has raised some interesting questions on how a service can be provided to meet the application requirements while obeying the network resource constraints. Previous efforts focussed on a flow-based, connection oriented approach to deliver QoS for IP Networks — Intserv. This approach was quite comprehensive but it has not been widely deployed because of complexity and scalability issues. A recent packet marking based scheme called Differentiated Services (Diffserv) Architecture provides a relatively simple and coarse approach. It is too early to predict the usefulness of this approach. This paper outlines a framework to deliver IP QoS which is based on Intserv. It addresses scalability concerns by removing the need for a connection-oriented reservation setup mechanism and replaces it with a Diffserv-like mechanism to consistently allocate bandwidth end-to-end in a network. A prototype device is discussed that manages bandwidth on a node. An algorithm is presented that allows the device to automatically detect application QoS requirements without the need for application-level signalling. A priority-based scheduling mechanism with a variant of weighted round-robin is described.