Performance Evaluation of EF-ADMIT
draft-gunn-tsvwg-ef-admit-evaluation-00

Abstract

A new Differentiated Services Code Point (DSCP), EF-ADMIT, has been recommended for a class of real-time traffic conforming to the Expedited Forwarding (EF) Per Hop Behavior (PHB) and admitted using a strong Call Admission Control (CAC) procedure incorporating capacity assurance, as compared to a class of real-time traffic conforming to the EF PHB but not subject to strong CAC. This document presents modeling results demonstrating that EF-ADMIT traffic will experience low packet drop rates even when lack of strong CAC results in EF traffic experiencing high packet drop rates. The modeling shows the performance benefit is material at low to medium network access speeds (e.g., 256 Kb/s to 1.5 Mb/s), but relatively inconsequential at high access speeds (e.g., 45 Mb/s) and, by inference, backbone speeds (100Mb/s and higher) where more bandwidth headroom is assumed. Furthermore, mixing relatively long packets (e.g., 1500 byte video packets) with relatively short packets (e.g., 200 byte voice packets) in EF PHB causes significant degradation to short packet performance at low to medium access speeds. Finally, the results show that implementation can be effective utilizing either one queue with combined EF and EF-ADMIT flows, or two queues with one forEF-ADMIT flows and one for EF flows, with the choice of approach mostly a matter of policy.

Authors

Janet P. Gunn

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)