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Mobility Aware Server Selection for Mobile Streaming Multimedia CDN

Mobility Aware Server Selection for Mobile Streaming Multimedia CDN. Muhammad Mukarram Bin Tariq , Ravi Jain, Toshiro Kawahara {tariq , jain, kawahara}@docomolabs-usa.com DoCoMo USA Labs. September 29, 2003. Summary.

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Mobility Aware Server Selection for Mobile Streaming Multimedia CDN

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  1. Mobility Aware Server Selection for Mobile Streaming Multimedia CDN Muhammad Mukarram Bin Tariq, Ravi Jain, Toshiro Kawahara {tariq, jain, kawahara}@docomolabs-usa.com DoCoMo USA Labs. September 29, 2003

  2. Summary • We present a mobility-aware server selection scheme for content distribution networks. • Our target is CDN with high density of servers, each server having a small coverage area. Mobile users can move out of such service areas in the duration of streaming media sessions, resulting potentially degraded QoS. • Server Handoff can be performed to revive QoS, but it is expensive. • We use user’s mobility along with traditional criteria such as proximity, server load etc., and assigns a server such that the probability of user moving out of coverage area of the assigned server is reduced, while meeting QoS criteria. • Simulation results show up to 18 % reduction in number of server handoffs.

  3. Outline • Summary • Introduction • Overview • Problem Statement • Mobility Aware Server Selection • Assumed CDN topology • Gathering user mobility information and estimating residence time with servers. • Server Selection. • Simulation • Mobility, Server Selection, Content Distribution. • Results • Conclusions

  4. Introduction • Multimedia has increasing share in overall traffic • Fixed broadband has not harnessed Multimedia, how will mobile broadband? • Mobile phones are there all the time. • Usage scenarios: movies, songs, news, playing video games etc, while traveling • CDN must meet the challenge of mobility, wireless and streaming media trio. • Our focus is the (Mobility + Streaming). Market Size (traffic) Multimedia 70-80% Voice 20-30% 2005 2010 Year Expected Future mobile communication market [Yumiba01]

  5. Streaming Media In Mobile Networks • In previous work [Tariq02] we showed that server handoff is helpful for streaming content to mobile users. • Localizes traffic, reduces delay, jitter, and load on the network. Server Handoff R Server Handoff R R R Server Server Server R R R R R R Logically Non Adjacent Subnets, (hot spots) Subnets in a Mobile Network

  6. Naïve server handoff scheme has problems • If the users move too fast, there would be too many server handoffs, which are expensive for the network. • Signaling, Content Placement • Our mobility-aware server selection assigns right users to right servers, reducing the need for handoffs. • Reduce Number of Handoffs while meeting QoS criteria.

  7. CDN Topology Tier 3 Server Coverage Area More Coverage Area • Allows: • Maximization of traffic localization • Obtain desired QoS ↔ Number of Handoffs tradeoff by choosing appropriate server tier. Better QoS Servers Tier 2 Server Coverage Area Tier 1 Server Coverage Area aka. server-zoneEach has a RR Access Network Subnets

  8. Server Selection Process • Move to higher tier if • Server Capacity Available • User is Moving Fast • QoS Diff is maintained • Move to lower tier if • Server Capacity Available • Won’t increase handoffs • QoS Diff is maintained Server Tiers Server Capacity Information We introduce a Lazy Mode where we do not move users to lower tiers unless higher tiers are saturated!!! RR Mobility Information

  9. Mobility Information Client maintains its average subnet residence time over k recent moves Trajectory of the client A subnet Mean residence time of all n clients in RR’s server-zone Residence Time Client i Mean Server Residence-time for each tier t RR uses the information to estimate a future residence time of client i with tier t We can make a high granularity estimate using subnet specific information, at cost of higher overhead.

  10. Simulation • Simulate realistic user movement in a large geographical area, collect movement events – we wrote a custom simulator for this. • Simulate different server selection algorithms • Baseline, clients always assigned to default tier • Eager mode with both Low and High Granularity Mobility Information • Lazy Mode with both Low and High Granularity Mobility Information. • See how we did in terms of delay and jitter experience by the users. Mobility Simulation Server Selection Simulation Content Distribution Simulation

  11. Mobility Simulation • Custom simulator to simulate realistic urban area user movement. • Cars, Trains, Streets, Freeways, Public Transport, Congestion, etc. • San Francisco Bay area, 3575 sq. miles. • Over laid with 189 base-stations, 59 subnets

  12. Simulation Parameters • CDN topology • 34 servers arranged in 3 tiers, 21, 8 and 4 in tiers 1, 2, and 3 respectively. • The 3 tiers at 80ms, 160ms and 240ms respectively, from the edge. • Server Capacity, variable {50, 75, 100, 200, 300} simultaneous sessions • Users • 2500 users with three QoS class, {1, 2, 3}, users distributed across the three QoS classes proportionately to the number of servers at corresponding tier. • Session Durations, variable {50, 100, 200, 1000, 1500} seconds • Data rate per user: 64kbps, 20pps • Selection Criteria • Desired QoS Separation between adjacent classes: 20 ms. • Server Overload threshold for Lazy mode. 10% of the maximum reported load allowance.

  13. Simulation Results (1/2) Eager Mode Lazy Mode Low Granularity High Granularity Results for server capacity = 300 Results for server capacity = 100 More results in the paper…

  14. Simulation Results (2/2) • Desired Separation is maintained in all scenarios • Eager mode is achievesbetter convergence and at lower overall value. • Higher server capacityallows us to do more. • Accuracy of estimationhas little impact. QoS Class 1 QoS Class 2 QoS Class 3 Lazy Mode Eager Mode

  15. Conclusions • We have presented a mobility aware server selection scheme. • Up to 18% reduction in number of server handoffs. • Simple, Largely stateless • Relies on simple and manageable information – much of which is already available in the network. • If you are eager, you better be sure – with eager mode, higher accuracy is crucial. • Has applications beyond streaming media. • Anywhere that you want to make tradeoff with mobility by switching to wider-area systems. • Open issues: • Improving while maintaining simplicity. • Manageability. • Bundling with other technologies.

  16. Algorithm Details Task: Assign server to a client i of QoS class q and current/default server tier t selectedTier := t Find load allowance of next higher tier Lt+1 If the client is in fastest Lt+1 – true if is less than Lt+1 here Uj number of sessions of a client j If the delay separation will be maintained – true if . similarly for q,q-1 Assign Server Tier t+1. End-If Else-If Eager Mode or (Lazy Mode with Lt+1 too low) – checking to see if we can move it to lower tier instead Make sure client won’t increase the number of handoffs i.e., Assign Server Tier t-1. End-If

  17. IWCW 2003Conference Report Muhammad Mukarram Bin Tariq DoCoMo USA Labs. October 8, 2003

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