The Use of ATM Quality of Service to Support IP over ATM Bruce A. Mah bmah@CS.Berkeley.EDU The Tenet Group 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 17th Annual ILP Conference, Berkeley, CA 9 March 1995 The Use of ATM Quality of Service to Support IP over ATM Page 1 of 20
Outline Introduction Using ATM QOS for IP conversations Multiplexing Virtual circuit management Implementation and Evaluation Summary The Use of ATM Quality of Service to Support IP over ATM Page 2 of 20
Environment: A Heterogeneous IP Internet H Ethernet FDDI R S R ATM Network Ethernet S S H R ATM network provides performance guarantees Internetwork carries a mix of data and multimedia traffic The Use of ATM Quality of Service to Support IP over ATM Page 3 of 20
IP over ATM TCP UDP IP AAL5 Ethernet FDDI ATM IP layer uses ATM protocol stack as a datalink layer Many commercial and research implementations exist Can we use ATM QOS to improve performance? The Use of ATM Quality of Service to Support IP over ATM Page 4 of 20
Research Issues Using ATM Virtual Circuits for IP How to map a stream of IP datagrams onto a virtual circuit? What QOS requirements do IP conversations have? Multiplexing How and when should multiple conversations share a virtual circuit? Virtual Circuit Management When should virtual circuits be created and torn down? The Use of ATM Quality of Service to Support IP over ATM Page 5 of 20
Mapping IP Datagrams onto a Virtual Circuit “IP Conversation” A stream of related IP datagrams between common endpoints with some definable set of QOS parameters Hosts and routers use protocol headers to determine conversations Packets of a conversations travel over a single ATM virtual circuit For example: All packets for a given telnet connection All NFS packets between a client and its server All ICMP messages between a host pair The Use of ATM Quality of Service to Support IP over ATM Page 6 of 20
Determination of Requirements Pre-defined per application For well-known applications (e.g. telnet ) Monitoring traffic Adapt to bandwidth requirements (e.g. variable-bitrate video) Explicit signalling In-band (e.g. IP options) Out-of-band with a signalling protocol (e.g. RCAP, RSVP) The Use of ATM Quality of Service to Support IP over ATM Page 7 of 20
Multiplexing with QOS Considerations Tradeoff Protection of individual IP conversations Increased utilization of reserved resources due to statistical multiplexing The Use of ATM Quality of Service to Support IP over ATM Page 8 of 20
Virtual Circuit Per Router Pair H H R R H H All traffi c between a pair of r outers routed over same virtual circuit Statistical multiplexing of conversations over virtual circuit No protection among conversations sharing a router pair Uses: Low-bitrate or bursty traffi c (ICMP) Background best-effort traffi c (electr onic mail) The Use of ATM Quality of Service to Support IP over ATM Page 9 of 20
Virtual Circuit Per Conversation H H R R H H Each IP conversation seen by a router uses a separate virtual circuit IP conversations protected from each other over ATM subnet No statistical multiplexing gain within virtual circuit Uses: Real-time video Interactive fi le transfer The Use of ATM Quality of Service to Support IP over ATM Page 10 of 20
Virtual Circuit Management with QOS Considerations Paradigm shift: ATM connections vs. IP datagrams When to set up and tear down connections for datagrams? Tradeoff Long-lived virtual circuits: Tie up resources Short-lived virtual circuits: Connection setup latency and processing The Use of ATM Quality of Service to Support IP over ATM Page 11 of 20
Permanent Virtual Circuits R R R No connection setup latency Resources always reserved Not flexible enough to handle changes in load O n 2 ( ) Scalability a problem: connections and resources The Use of ATM Quality of Service to Support IP over ATM Page 12 of 20
Switched Virtual Circuits R R R Establish virtual circuits on demand Tear down connections when not used Connection setup latency incurred For fi rst packet of conversation For other packets if SVC closed too early Enhancement: connection caching for other IP conversations The Use of ATM Quality of Service to Support IP over ATM Page 13 of 20
Implementation and Evaluation Berkeley Wisconsin Bell Labs LBL UIUC Rutgers LLNL SNL XUNET II: A wide-area ATM backbone (DS-3 between FDDI) The Use of ATM Quality of Service to Support IP over ATM Page 14 of 20
Completed Work MBONE Measurements Video— nv Audio— vat Image distribution— imm XUNET IP driver modifi ed to distinguish IP conversations All TCP connections map to unique virtual circuits All UDP streams map to unique virtual circuits XUNET IP over ATM service enhanced to use SVCs Virtual circuits created on demand Fixed idle timeout The Use of ATM Quality of Service to Support IP over ATM Page 15 of 20
Video Bitrate ( nv 128 Kbps) 300 law.cs.berkeley.edu 250 KBits per second 200 150 100 50 0 0 500 1000 1500 2000 2500 3000 3500 4000 Time in Seconds Average bitrate (one-second samples) 115 Kbps Peak bitrate (one-second samples) 270 Kbps The Use of ATM Quality of Service to Support IP over ATM Page 16 of 20
XUNET Router TCP Throughput 40 35 Throughput (Mbps) 30 25 20 Enhanced XUNET IP Driver Default XUNET IP Driver 15 10 5 0 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 User Data Payload Size (Bytes) Preliminary measurements show no performance degradation The Use of ATM Quality of Service to Support IP over ATM Page 17 of 20
Work in Progress Obtain QOS-guaranteed virtual circuits over XUNET Scheduling disciplines Signalling support Formulate IP over ATM strategies Mapping from IP conversation(s) to QOS-guaranteed virtual circuit Multiplexing policy Virtual circuit setup and teardown policy The Use of ATM Quality of Service to Support IP over ATM Page 18 of 20
Evaluation of Strategies Performance for IP conversations End-to-end latency Throughput Setup latency Overall network performance Utilization Effi ciency and over head Best-effort performance The Use of ATM Quality of Service to Support IP over ATM Page 19 of 20
Summary Idea: Use QOS guarantees for an IP-over-ATM service Use of virtual circuits with QOS parameters to carry IP data Multiplexing Virtual circuit use and management Implementation in progress on XUNET II Evaluate various strategies Performance of individual conversations Performance of network as a whole The Use of ATM Quality of Service to Support IP over ATM Page 20 of 20
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