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A Novel Approach for Transparent Bandwidth Conservation

A Novel Approach for Transparent Bandwidth Conservation. David Salyers, Aaron Striegel University of Notre Dame Department of Computer Science and Engineering Supported by NSF Grant: CNS03-47392. Introduction. Internet has grown an evolved Simple connectivity → sophisticated applications

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A Novel Approach for Transparent Bandwidth Conservation

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  1. A Novel Approach for Transparent Bandwidth Conservation David Salyers, Aaron Striegel University of Notre Dame Department of Computer Science and Engineering Supported by NSF Grant: CNS03-47392

  2. Introduction • Internet has grown an evolved • Simple connectivity → sophisticated applications • Point-to-point nature • Increased redundancy • Techniques to reduce redundancy • Active (multicast) • Passive (caching) IFIP Networking 2005

  3. Multicast Techniques • Current Multicast Techniques • IP Multicast • Application Layer Multicast (ALM) • Issues • Require global deployment • Application and/or end-to-end network support required IFIP Networking 2005

  4. Caching Techniques • Types: • Web/media caching • Packet Caching [Santos,Wetherall USENIX 1998] • Benefits: • Simple deployment • Reduces long term redundancy • Drawbacks: • Cannot handle short term redundancy IFIP Networking 2005

  5. Our Solution • Dynamic “Stealth” multicast • Dynamic formation of virtual multicast groups • Multicast only occurs inside a domain • Uses existing multicast within domain (PIM-SSM) • Does not require global multicast support. • Does not require application support. IFIP Networking 2005

  6. Stealth Multicast: Overview IFIP Networking 2005

  7. Key Principles • External Transparency • The end clients and server applications should not be aware that stealth multicast is operating • Limited QoS impact • Stealth multicast should not significantly affect the QoS of the application, specifically the end-to-end delay IFIP Networking 2005

  8. Stealth Multicast Operation • Virtual Group Detection Manager (VGDM) • Key Responsibilities • Signature generation • Background Traffic Analysis • Managing Virtual Groups • Converts to multicast • Creates/Updates physical trees IFIP Networking 2005

  9. Stealth Multicast Operation: VGDM IFIP Networking 2005

  10. Virtual Group Management • Only amenable packets are queued for possible multicast transport. • Non-amenable packets are never queued • Bounded QoS impact. • MHT – Maximum Hold Time • TSW – Time Search Window • PSW – Packet Search Window IFIP Networking 2005

  11. Stealth Multicast Transport • PIM-SSM (Single Source Multicast) • Source = ingress point • Receivers = egress points • Note: • Egress points << # of clients • Source driven changes (VGDM) • Join/Leave operations • Resource management/billing IFIP Networking 2005

  12. State Management • Problem • Preservation of unique client information. • Destination IP/Destination Port • Encapsulation vs. egress storage • Stateless (encapsulation) • Include after L4 (UDP) header • Simple state coherency • Stateful (egress storage) • Unique state stored at egress points • Limited packet overhead IFIP Networking 2005

  13. Scalability Considerations • Queue size (memory) • Needs less than 6MB of queue to handle 1Gbps with a MHT = 5ms • Redundancy detection • Santos, Wetherall [USENIX 1998] • Experimental studies • Itanium 2 – RedHat Linux (user space - libpcap) • Intel IXP IFIP Networking 2005

  14. Simulation Studies - Setup • ns-2 Simulation • Random ISP domain (32 core, 16 edge nodes) • Server Farm (40 source Applications) • Average number of clients per application: 32 • 500ms average inter-arrival time for join/leave events • Server Applications, UDP, exponentially distributed packet rate of 50ms and size of 500bytes IFIP Networking 2005

  15. Types of Transport Compared • Unicast • No multicast transmissions. • Full Stealth • VGDM is at edge node. • Local Stealth • VGDM is at server node. • ALM • Generic version of ALM • Ability to support 5 downstream clients • IP Multicast • Ideal version of IP Multicast IFIP Networking 2005

  16. Client Subscriptions: QoS Delay IFIP Networking 2005

  17. Client Subscriptions: Link BW IFIP Networking 2005

  18. Client Subscriptions: Domain BW IFIP Networking 2005

  19. Conclusions • Limited QoS (delay) impact • Provides multicast benefits combined with ease of deployment of caching • Key Benefits • No application support required • Simple resource management/billing • Directable economic benefit IFIP Networking 2005

  20. Current Work • Stealth multicast prototype • Wireless stealth multicast • Passive Application Layer Multicast (PALM) IFIP Networking 2005

  21. Questions? dsalyers@nd.edu http://www.cse.nd.edu/~dsalyers IFIP Networking 2005

  22. Simulation Studies – Setup (VGDM) IFIP Networking 2005

  23. Maximum Hold Time: QoS Delay IFIP Networking 2005

  24. Other Issues Cont. • Practical Benefit • While well suited for networks that contain a reasonable amount of redundant traffic, it is not envisioned that VGDMs are deployed at all nodes. • Since the VGDM • TCP • Generally TCP traffic is not amenable to stealth multicast. However, we are researching techniques to eliminate this problem. IFIP Networking 2005

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