Example Applications needing Advanced Services Campus Focused Workshop on Advanced Networks Atlanta, GA

Voice over IP Environment for Research (VIPER) Chakravarthy K Sannedhi Electrical & Computer Engineering

VoIP: Benefits Data traffic growing rapidly – Multiple parallel networks are expensive – VoIP Enables convergence of voice & data networks – Low-cost and flat-rate pricing possible IP is compatible with most modern network technologies & topologies

VoIP: Issues Delay – too much can cause “real time” voice interaction to become useless Jitter – small amounts can be “fixed” by jitter buffers, but end- to-end delay suffers Packet loss – creates “big gaps” in received (reconstructed) voice

VoIP: QoS approaches Bandwidth allocation – Necessary, but not sufficient Prioritization of the voice traffic – Necessary, but not sufficient – Different techniques have different effects on voice as well as “other traffic” QoS Techniques – DiffServ – IntServ – Traffic Shaping

VoIP: Quality Testing Objective Testing – Necessary, but not terribly useful – Objective measures often correlate poorly with human perception (even when perceptual models are used) Subjective Testing – Necessary, but prone to error and interpretation – Time consuming, particularly in context of network-dependent error mechanisms General idea … VIPER – Automated environment to configure various network-based parameters which affect voice QoS – Enables collecting of subjective test data

VIPER Architecture

Web Interface Call GeneratorTest taker’s data collector Noise Generator Script Loader Voice Database Script Database MySQL Database VIPER Architecture

QoS Techniques Tested IntServ (RSVP) DiffServ (EF and AF) Label Switching (MPLS) Traffic Shaping (CAR, GTS, etc.)

Best Effort No QoS First In First Out Still the voice is marked with EF 1.1

RSVP IntServ Technique Sender sends the PATH message which contains TSpec Receiver sends RESV which includes Flowspec 75% of the bandwidth to voice 1.4

Weighted Fair Queuing Schedules interactive traffic to the front of the queue Applies weights to identified traffic flows Shares the remaining bandwidth between the high bandwidth flows 3.6

Custom Queuing Services the traffic in round robin basis Voice was given maximum queue limit and maximum byte count 1.2

Priority Queuing Suitable for interfaces with less than Mbps bandwidth Voice is placed in the High priority queue Injustice to traffics that are other than in High priority queue 1.2

Class Based WFQ Traffic is placed in different classes Simultaneous handling of the traffic 10 % of bandwidth to voice 4.4

CBWFQ with LLQ Brings strict priority queuing to CBWFQ Preferential treatment for the voice Not effective on Frame Relay networks 3.6

Committed Access Rate Traffic Shaping technique Voice packets are given the nice burst range with a good amount of tolerance Lowers the Jitter 1.4

IP RTP Priority with WFQ Useful for slow speed links with speeds less than Mbps Voice packets are identified by the UDP port range Voice was given 60 Kbps of bandwidth along with the application of fair queuing 3.9

IP RTP Priority with RSVP Voice is identified by its UDP port range 75% of the bandwidth to the voice 1.5

VIPER pMOS results QoS (in extreme congestion) PMOSMissed Calls (%) Confidence (95%) Best Effort  0.14 WFQ  0.27 RSVP only  0.28 IPRTP + EF  0.28 IPRTP + WFQ  0.27 RSVP + IPRTP  0.28 CQ + EF  0.19 PQ + EF  o.19 CBWFQ + LLQ + EF  0.27 CBWFQ + EF  0.22 CAR + EF  0.36

Acknowledgements Jill Gemmill – Assistant Director, Department of Academic Computing, UAB Stan McClellan – Associate Professor, Electrical & Computer Engineering. UAB

References Red Hat Linux - Iperf - MySQL - PHP - Cisco - Expect - Vgetty -

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