Load Balancing in aCluster-based Active

Jiani Guo (Student Member, IEEE)Laxmi Bhuyan (Fellow, IEEE)

March 15th 2005

Seo, Dong Mahn

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ContentsI. IntroductionII. Background and Related Work

- Background, Related work

III. Cluster-Based Active Router Architecture- Cluster-Based Active Router, Cluster-based Multimedia Transcoding Service, Software Framework of Active Router Cluster, Load Test Mechanism

IV. Load balancing Techniques- First Fit (FF), Stream-based Mapping (SM), Least Load First (LLF), Adaptive Load Sharing (ALS) Policy, Adaptive Portioning (AP)

V. Design of the Experiments- Experimental Settings, Design Issues

VI. Performance Metrics- System Scalability, Load Sharing Overhead, Video Quality

VII. Performance Evaluation- Effect of Varying Load test Epoch, Effect of Varying Packet Size, Effect of Varying Number of Dispatchers, System Throughput, Video Quality

VIII. Conclusion

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Introduction (1) Parallel and distributed computing systems Active network architecture

NetScript project, ANTS system, SwitchWareMega project, Journey network

Multimedia streamingTo provide real-time transcoding serviceCluster-based Active Router Architecture (CLARA)

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Introduction (2)

Load balancingSimple static policyAdaptive load balancing policySame flow packetsMultimedia Active Router

reduce the transcoding timeensure that the out of order departure of packets belonging t

o ther same streamRound-robin & one flow/stream

Inter-departure time & Jitter

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Introduction (3)

In this paperLinux-based active router cluster

Gigabit Ethernet, multithreaded software architectureManager node, Computing Servers

Load test mechanismAdoptive load sharing technique based on the HRW al

gorithmNew algorithm : Adaptive Partitioning (AP)First fit, Adaptive load sharing schime, Stream-based

mapping, AP

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Background

Transmission of multimedia informationTo store multiple copies of the source stream

JPEG transcoding technique, determinig the level of transcoding

Cluster-based web distillation proxy (TranSend)Layered source-coding algorithmReal-time transcoding service

Application level video gateway architecture, active network node (ANN), proxy architecture, CLARA

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Related work

Load balancingSimple static policy

Random distribution policy, modulus-based round robin policy

Load balancing algorithms with the concept of flowsHRW algorithm

MPEG transcodingLoad sharing schemes

Round robin, stream-based round robin, adaptive load sharing

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Cluster-Based Active Router

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Cluster-based Multimedia Transcoding Service

MPEG-1, MPEG-2, H.261/263, MPEG-4 MPEG-4 Object Composition Petri Net (MOCPN) To deploy transcoding among different coding sch

emes Ours

To provide a general transcodingTo develop a scheduling technique

Fast transcodingReducing the out-of-order departure

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Software Framework of Active Router Cluster (1)

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Software Framework of Active Router Cluster (2)

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Load Test Mechanism

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First Fit (FF)

Round robin way Scheduler blocked, if full Put the media unit, if vacancy Without extra load analyzer Better than the simple round-robin scheme

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Stream-based Mapping (SM) To preserve the computation order To keep the simplicity of first fit Propose and implement f(c) = c mod N, c is the stream number, N is the to

tal number of servers. j = i % N, i is stream, j is dispatch queue. Good for homogeneous servers and some specific

input patternsM ≥N, M = multiple of N (M is the number of streams,

N is the number of servers)

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Least Load First (LLF)

Actual load condition Picks the currently least loaded server Ai(t), the number of outstanding requests Transcoding workload is proportional. The same stream are possible to be distributed to

different servers High jitters at destination

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Adaptive Load Sharing (ALS) Policy

Extended HRW technique

v is the identifier vector of the packet, j is the server node to which the packet

Utilization of each server

Implement function

Same weightsload informationload statistics informationmodify and recalculate

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Adaptive Portioning (AP) (1)

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Adaptive Portioning (AP) (2)

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Adaptive Portioning (AP) (3)

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Experimental Settings Assumptions

1 input port, 1 output port Multiple media streams concurrently on the Manager nod

e Departure-Recorder program MPEG-1

color video to black/white, FFMpeg No multi-layer encoding, stream error correction encoding 15 frames in a GOP, 30fps, around 50KB of GOP, a GOP per 0.

2 sec

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Design Issues

1) Load Test Epoch Sensitive parameter for feedback-based load

balancing schemes

2) Number of Threads Thread switching is non-negligible overhead.

3) Packet Size 10K to 100K GOP size Packet size

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System Scalability

Measure the scalability of our clusterSystem throughput, GOPs/sec

One of the most important metrics

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Load Sharing Overhead Metric 1 : Load Test Overhead is the average time

consumed by the Manager node to poll through all servers to collect the load statistics information.

Metric 2 : Load Remapping Overhead is the time consumed to set the current load for each server in a specific load balancing scheme.

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Video Quality Metric 1 : Departure Jitter per Stream is the stan

dard deviation of the interdepature time among GOPs when the stream is received by the Departure-Recoder PC.

Metric 2 : Average Interdeparture Time among GOPs per Stream is the mean of the interdepature time among GIOs when the stream is delivered to the active router.

Metric 3 : Out-of-Order Rate per Stream describes how many GOPs among all the GOPs in a stream depart out of order.

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Effect of Varying Load test Epoch

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Effect of Varying Packet Size (1)

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Effect of Varying Packet Size (2)

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Effect of Varying Number of Dispatchers

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System Throughput

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Video Quality (1)

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Video Quality (2)

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Video Quality (3)

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Conclusion (1)

Active networkNew direction for processing network trafficDistribute expensive computationMultimedia traffic

Cluster-based active router architectureDesign, implement, evaluate

Load sharing policyFirst Fit, Least Load First, Stream-based Mapping, Ad

aptive Load Sharing, Adaptive Partioning

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Conclusion (2) Load balancing scheme

To improve the throughput First Fit and Least Load First schemes

To achieve good video playout quality Stream-based Mapping, Adaptive Load Sharing and Adaptive Partitioni

ng

Feedback-based scheme Adaptive partitioning algorithm

Future research Address the problem Explore how to guarantee QoS requirements for different

streams

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Q & A