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

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

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

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

6. 6IFIP Networking 2005 Stealth Multicast: Overview

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

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

9. 9IFIP Networking 2005 Stealth Multicast Operation: VGDM

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

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

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

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

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

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

16. 16IFIP Networking 2005 Client Subscriptions: QoS Delay

17. 17IFIP Networking 2005 Client Subscriptions: Link BW

18. 18IFIP Networking 2005 Client Subscriptions: Domain BW

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

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

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

22. 22IFIP Networking 2005 Simulation Studies – Setup (VGDM) Maximum Groups: 50 Maximum Hold Time: 5ms Time Search Width: 2ms Packet Search Width: 100 Min Group Size: 2 Max Group Size: 200 State Management: Distributed Egress Threshold: 30% Time Lock: 100ms

23. 23IFIP Networking 2005 Maximum Hold Time: QoS Delay

24. 24IFIP Networking 2005 Other Issues Cont. Practical Benefit 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. 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 Since the VGDM TCP TCP Generally TCP traffic is not amenable to stealth multicast. However, we are researching techniques to eliminate this problem. Generally TCP traffic is not amenable to stealth multicast. However, we are researching techniques to eliminate this problem.