1 / 18

Quality of Service Issues in Multi-Service Wireless Internet Links

Quality of Service Issues in Multi-Service Wireless Internet Links. George Xylomenos and George C. Polyzos Department of Informatics Athens University of Economics and Business Athens 10434, Greece polyzos@aueb.gr http://dias.aueb.gr/~gcp/ Tel.: +30-1-8203-650, Fax: +30-1-8203-325. Outline.

temple
Télécharger la présentation

Quality of Service Issues in Multi-Service Wireless Internet Links

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Quality of Service Issuesin Multi-ServiceWireless Internet Links George Xylomenos and George C. Polyzos Department of Informatics Athens University of Economics and Business Athens 10434, Greece polyzos@aueb.gr http://dias.aueb.gr/~gcp/ Tel.: +30-1-8203-650, Fax: +30-1-8203-325

  2. Outline • Motivation • Wireless systems and Internet applications • TCP throughput degradation • UDP and real-time application issues • Proposed approaches • Flexible Link Layer Internet Protocol (FLLIP) • Multi-protocol, adaptive, QoS/DS aware solution • Goals, architecture, implementation • Implicit and explicit service selection • Conclusion polyzos@aueb.gr

  3. Modern Wireless Systems • Opportunities and issues • Digital wireless systems • Cellular, PCS, 3G • Wireless LANs • LEO/MEO Satellites, LMDS • Mobility • Internet protocols: designed for networks that were • Wired: low error rate • TCP:loss  congestion • Fixed: no mobility, no handoffs • Physical layer solutions • Inflexible: one size fits all polyzos@aueb.gr

  4. Internet Applications and Protocols • Conventional data exchange applications • Usually TCP based • Error intolerance • Delay tolerance • Jitter intolerance (TCP) • Interactive and real-time applications • Often UDP based (plus RTP) • Often multipoint (IP Multicast) • Some error tolerance • Delay intolerance polyzos@aueb.gr

  5. Proposed Approaches • Indirect TCP • violation of semantics (not end-to-end anymore) • Snoop TCP • works well only in the direction towards the mobile • Modifications to TCP • Compatibility: usually both ends need to be updated • End-to-end retransmissions for a local problem • Not multi-protocol: useless for non TCP applications • Conventional link-layer schemes • Inflexible: one service only • Irrelevant for some protocols/applications polyzos@aueb.gr

  6. TCP/UDP TCP/UDP TCP/UDP IP IP IP IP 2Mbps 10Mbps 2Mbps LL LL LL LL 3ms 1ms 3ms PHY PHY PHY PHY Wireless Host A Base Station A Base Station B Wireless Host B Simulation Experiments • One and two wireless link scenarios • Exponential intervals between errors • 0.8-5.9% frame loss rates (1 Kbyte frames) • TCP: 100 Mbyte file transfer • UDP: Voice activated CBR video (1 Mbps) • Each test repeated 30 times polyzos@aueb.gr

  7. TCP Performance: Throughput polyzos@aueb.gr

  8. UDP Performance: Delay polyzos@aueb.gr

  9. Flexible Link Layer Internet Protocol (FLLIP) • Address the problem at its source • Local solution to a local problem • Compatible with Internet protocols & architecture • IP and higher layers unchanged • Aware of QoS requirements • Implicitly or explicitly • Per stream or classQoS differentiation • Fully or mostly reliable • Dynamic adaptation to stream/class mix • Variable bandwidth allocation • Dynamic adaptation to channel conditions polyzos@aueb.gr

  10. FLLIP Architecture • Multiple link layer modules • Packet classifier • Protocol, TCP/UDP ports • IP ToS, DS field • Per class load measurements • Incoming bandwidth allocations • Service class specific processing • Isolation between services • Frame scheduler (SCFQ) • Enforces incoming bandwidth allocations polyzos@aueb.gr

  11. SCFQ Frame Scheduler • Enforces incoming allocations • Protects services • Encourages efficiency • Self-clocked fair queueing (SCFQ) • Efficient, simple, fair • One queue per class • Heap sort polyzos@aueb.gr

  12. TCP Performance: Throughput with FLLIP polyzos@aueb.gr

  13. UDP Performance: Delay with FLLIP polyzos@aueb.gr

  14. Service Selection • Implicit QoS specification • Assigns applications to services • Protocol and TCP/UDP port fields • No changes to Internet protocols and applications • Immediate applicability • Explicit QoS specification • Assigns traffic classes to services • QoS provision • Integrated Services, RSVP • QoS differentiation • Differentiated Services • More flexible polyzos@aueb.gr

  15. Heuristic Packet Classifier • Implicit QoS specification polyzos@aueb.gr

  16. Differentiated Services Packet Classifier • Explicit QoS specification • Dynamic service selection polyzos@aueb.gr

  17. Service Measurement and Mobility Feedback • Service selection • Standard metrics • Refinement • Adaptive applications • Mobility polyzos@aueb.gr

  18. Conclusions • TCP performance severely impacted by wireless losses • TCP is not the only concern • Real-time multimedia over UDP • New applications and protocols • Link layer enhancements • Fast local recovery • Customized to underlying link • Wireless links: natural choice to introduce • QoS support • Differentiated services because • Bandwidth is scarce and expensive • Link performanceis variable and unpredictable polyzos@aueb.gr

More Related