Quality of Service and Asynchronous Transfer Mode in IP Internetworks Bruce A. Mah bmah@CS.Berkeley.EDU http://http.CS.Berkeley.EDU/~bmah/ The Tenet Group Computer Science Division University of California at Berkeley T Y • O I F S • R C E A V A L I I F N O U • R L L E E I G H T T N H T H I E E T R E B A • • • • 1 8 6 8 Berkeley Multimedia and Graphics Seminar 27 November 1996 Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 1 of 47
Motivation Ethernet FDDI R S R Ethernet ATM Network S S R ATM growing in popularity, but Internet is ubiquitous and heterogeneous. Want to use these types of networks together efficiently. Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 2 of 47
IP and ATM: Critical Differences Asynchronous Transfer Internet Protocol Mode Connections Yes No Service Model Quality of service Best-effort support, can provide performance guarantees Packets Small, fixed-size cells Variable-sized packets Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 3 of 47
Problems to be Solved ATM QOS in an IP Internetwork How can IP applications benefit from ATM quality of service support? Multiplexing What packets should share a virtual circuit? Virtual Circuit Management When should virtual circuits be created and torn down? Other Issues (not addressed here) Routing Address Resolution Multicast Support Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 4 of 47
Results ATM QOS QOS support can be helpful, if used carefully. Multiplexing Multiplexing eliminates virtual circuit setups, can help application performance. Virtual Circuit Management Caching idle virtual circuits can improve both network and application performance. Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 5 of 47
Outline ☞ Design Alternatives An Internet Simulated ATM Networking Environment Methodology Results and Analysis ATM Quality of Service Multiplexing Virtual Circuit Management Conclusions Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 6 of 47
IP over ATM: A Software View TCP UDP IP Adaptation Layer Signaling Ethernet FDDI ATM ATM stack treated by IP as a datalink layer. Device driver puts IP packets in AAL frames, establishes virtual circuits as needed. Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 7 of 47
Policies and Design Alternatives ATM Quality of Service Different service disciplines Preference to different applications Multiplexing ...per conversation ...per application type per host pair ...per router pair Virtual Circuit Management Permanent virtual circuits Switched virtual circuits Switched virtual circuits with caching Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 8 of 47
IP over ATM Policy Space Quality of Service Policies Virtual Circuit Management Policies Multiplexing Policies Policies to address problems: a three-dimensional space. Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 9 of 47
An Internet Simulated ATM Networking Environment (INSANE) Functional Requirements ATM (cell transport, adaptation layer, signalling) TCP features (slowstart, congestion control, fast retransmit, etc.) Synthetic workload with application-specific traffic patterns Logistical Constraints Easy to configure for large scenarios (1000+ hosts) Fast (hour-long simulations in reasonable time) Batch processing, off-line analysis Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 10 of 47
INSANE Protocol Stack User Workload Generator Telnet FTP HTTP SMTP NNTP Audio Video TCP UDP IP LAN Device Driver ATM Device Driver AAL RCAP LAN Reliable Cells ATM Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 11 of 47
Performance Notes Hardware Platform Running Time Sun Ultra 1 3X Sun Sparcstation 10 11X 100 MHz P5 (FreeBSD 2.1.0-RELEASE) 8X DEC Alpha AXP 3000/400 8X 300 simulation runs (4000 seconds each) 1500 hours of CPU time on Sun Ultra 1 cluster Estimated 10 GB raw data Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 12 of 47
Environment 1.5 Mbps ATM R R 30 ms R R R R 100 Mbps LAN × 200 × 2 W S Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 13 of 47
Workload Interarrival Time Application Source (MM:SS, per site) telnet tcplib 0:10 FTP tcplib 0:15 HTTP empirical 0:05 Audio tcplib 10:00 Video empirical 10:00 SMTP tcplib 0:04 NNTP tcplib 3:45 Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 14 of 47
Performance Metrics Objective: Measure performance effects visible to applications and users. telnet Setup and round-trip time FTP File and session response times HTTP File, Web page transfer times Audio Loss rate, one-way end-to-end delay Video Loss rate Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 15 of 47
Outline Design Alternatives An Internet Simulated ATM Networking Environment Methodology ☞ Results and Analysis ATM Quality of Service Multiplexing Virtual Circuit Management Conclusions Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 16 of 47
ATM Quality of Service Schedulers Best Effort (First-Come-First-Served) Static Priority Rate-Controlled Static Priority Rate-Controlled Static Priority (Rate Jitter Control) QOS parameters assigned based on application type Results Static priority can give preference, but starvation a danger Rate control for bulk transfers yields inconclusive results Rate jitter control reduces losses in long TCP bulk transfers Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 17 of 47
High-Priority Telnet 0.25 Telnet Response Time (seconds) 0.2 0.15 0.1 0.05 0 Best Effort High-Priority Telnet Interactive performance can be improved. Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 18 of 47
High-Priority FTP 4 FTP File Transfer Time (seconds) 3 2 1 0 Best Effort High-Priority FTP FTPs given high priority take less time. Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 19 of 47
High-Priority FTP 12 Overdue Loss Audio Loss/Overdue Rate (%) 10 8 6 4 2 0 Best Effort High-Priority FTP High-priority FTP can degrade others’ performance. Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 20 of 47
High-Priority Applications 1.2 Telnet Connect Time (seconds) 1 0.8 0.6 0.4 0.2 0 Best Effort High-Priority Applications Signalling starved by higher priority traffi c. Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 21 of 47
RCSP Rate-Limiting of Bulk Transfers 100 FTP File Transfer Time (seconds) 10 1 0.1 Best Effort FTP sent via RCSP RCSP can be used to constrain bulk transfers. Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 22 of 47
RCSP Rate-Limiting of Bulk Transfers 0.3 Telnet Round-Trip Time (seconds) 0.25 0.2 0.15 0.1 0.05 0 Best Effort FTP sent via RCSP Rate-control effects on best-effort applications unclear. Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 23 of 47
Jitter Control Effects 1000 FTP Session Time (seconds) 100 10 1 Best Effort FTP sent FTP sent via Jitter via RCSP Control RCSP Bursts smoothed out by delay jitter control, fewer losses. Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 24 of 47
Outline Design Alternatives An Internet Simulated ATM Networking Environment Evaluation Results and Analysis ATM Quality of Service ☞ Multiplexing Virtual Circuit Management Conclusions Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 25 of 47
Multiplexing Policies Different levels of traffi c aggr egation Virtual circuit per conversation (e.g. TCP connection) Virtual circuit per application per end-host pair Virtual circuit per router pair Results Multiplexing eliminates virtual circuit setups Interaction with policing degrades performance of long FTP, Web transfers Buffer contention causes losses with per-router pair multiplexing Quality of Service and Asynchronous Transfer Mode in IP Internetworks Last Change: November 20, 1996 Page 26 of 47
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