The University of Arizona, Department of Computer Science

IP Router with QoS Support

Overview

We are building an IP router with Quality-of-Service support in Scout. The router supports the IETF-defined Guaranteed and Controlled-Load service classes, along with the conventional best-effort service class. The implementation includes multiple packet scheduling algorithms, including Deficit Round Robin (DRR), Virtual Clock (VC) and Weighted Fair Queuing (WFQ).

Research Goals

• Paths. Our main objective is to understand how Scout paths map onto traffic flows, and how Scout's scheduling mechanism can be used to schedule packets according to a network reservation.
• Quality of Service. We are studying the interplay of network reservations with different end-to-end transport strategies, such as TCP Vegas congestion control.
• Customizable Routers. We are also interested in developing a router architecture that can easily be customized, for example, to add firewall support, to bridge IPv4 and IPv6 networks, and in the extreme, to add per-flow extensions. Allowing per-flow customization is an example of an active network, and will eventually provide support for liquid software.

Router Graph

Forwarding paths extend from one link to another. In our architecture each reservation-based flow (Guaranteed or Controll-load flow) is mapped onto a single path, while all the best-effort traffic between two links is aggregated onto a single path. The above Scout graph illustrates the path layout for a router with two links. There are two guaranteed flows, one controlled-load flow, and multiple best-effort flows represented in this graph.

Status

• The router functions and supports the DRR and VC scheduling algorithms.
• Flow reservations are made "off-line." An implementation of RSVP is in progress.

Papers

A. Khune and L. Peterson. Implementing a Quality of Service Router in the Scout Operating System. In preparation.

Contributors

• Abhiram Khune, Graduate Student
• Venkat Raghavan, Graduate Student
• Mason Katz, Research Staff.
• Jørgen S. Hansen, Visiting Scholar

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Last updated March 2, 1998