Protocol Action: Network performance measurement for periodic streams to Proposed Standard
The IESG <iesg-secretary@ietf.org> Tue, 01 October 2002 14:56 UTC
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From: The IESG <iesg-secretary@ietf.org>
Subject: Protocol Action: Network performance measurement for periodic streams to Proposed Standard
Date: Tue, 01 Oct 2002 10:45:20 -0400
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The IESG has approved the Internet-Draft 'Network performance measurement for periodic streams' <draft-ietf-ippm-npmps-08.txt> as a Proposed Standard. This document is the product of the IP Performance Metrics Working Group. The IESG contact persons are Allison Mankin and Scott Bradner. Technical Summary The document specifies a metric that introduces packets with repeating periods and length as a particular model. It formalizes periodic stream measurement to achieve comparable results between independent implementations. As noted in the IPPM framework RFC 2330, this type of metric has some limitations, such as probing only a limited part of of the perfomrance spectrum, but it also has strengths, of which just a few: * It can be configured to match particular inelastic media flows. * Measurement of many network impairments (e.g., delay variation, consecutive loss, reordering) are sensitive to the sampling frequency. When the impairments themselves are time-varying (and the variations are somewhat rare, yet important), a constant probing frequency may simplify analysis The specification provides the definition of the metric, and its analysis, a repeatable algorithm for it, and considerations for its security. It also specifies how to avoidcongestion and network synchronization effects that might arise with long running tests: 1. The performance sampled may be synchronized with some other periodic behavior, or the samples may be anticipated and the results manipulated. Unpredictable sampling is preferred. 2. Active measurements of sufficient volume can cause congestion, and periodic sampling might drive congestion-aware senders into a synchronized state, producing atypical results. The total traffic generated by this or any metric should be limited to avoid adverse affects on non-test traffic (random start times, choice of packet size, and test duration should be carefully considered, for instance). Working Group Summary There was good working group consensus on this document and careful review to ensure a correct specification. Protocol Quality The specification was reviewed for the IESG by Allison Mankin.