Multimedia Streaming Gateway With Jitter Detection Siu-Ping Chan, Chi-Wah Kok Albert K. Wong IEEE TRANSACTIONS ON MULTIMEDIA, June 2005

Outline Introduction Related Work Jitter-Aware QoS for multimedia traffic –Jitter Detection Scheme 1 –Jitter Detection Scheme 2 Simulation Results Conclusion

Introduction When a multimedia stream is transported over packet-switched network, it assumes a constant network delay. Investigate a novel active buffer management scheme, “Jitter Detection” (JD) based on gateway-based Discard packet with enough jitter which is useless to clients

Related Work Gateway-based packet-switch network congestion control RED-drop packets randomly with a probability according to current queue length and a queue-size Like RED, but with average delay

Preparation in JD scheme Classify a packet as TCP or multimedia streaming packet with protocol field in IPv4 Delay jitter counter with four quantized regions stored in TOS field in IPv4 More near client, less discard –Need residual distance –With TTL field as residual distance –Servers and clients need to exchange hop-count information during session setup and routing update

Jitter-Aware QoS for multimedia traffic The packet size of the streaming is assumed to be fixed (ex. MPEG-2 VBR audio traffic) Losing some packets will still allow partial decoding of multimedia data

Jitter Detection Scheme 1

Estimate delay –CBO: current buffer occupancy of the output queue –LC: output link capacity –delay = CBO* Packet_Size/LC Count average delay –ave_delay= ave_delay*(1-wd)+delay*wd Count jitter –Jitter = delay- ave_delay

Jitter Detection Scheme 1 Count threshold (accumulated jitter) Decide if dropping or not - current past accumulate

Jitter Detection Scheme 2 What differ with JD1 –Jitter tolerance must be bigger if packet near destination (ie, fixed_th bigger when near clients) –Actual residual distance is hard to obtain With TTL as residual distance

Performance Bounds and Analysis of Dropping Decision Analysis the upper bound on the probability of dropping packet with Chebyshev inequality Chebyshev inequality : delay value of received multimedia packet : sample mean delay : standard deviation

Simulation Results With Network Simulator Two TCP source & two UPD source (Multimedia traffic) RED & JD are implemented in the gateways for congestion control of the TCP and UDP packets Two sets of additional simulations are performed using DropTail and the RED congestion control schemes

Simulation Results

Simulation Results-TCP Friendliness Greedy high-bandwidth UDP traffic will typically lower the throughput of TCP flows With TCP and UDP apply different buffer management schemes before putting into FIFO queue –JD have certain TCP-friendliness such that it will not lower the throughput of the TCP flows

Simulation Results-TCP Friendliness RED for TCP decrease !!

Simulation Results-TCP Friendliness lower drop rate

Simulation Results Delay Jitter of Multimedia Traffic Delay jitter for some received UDP packets using RED

Simulation Results Delay Jitter of Multimedia Traffic average delay jitter for some received UDP packets using different queue management scheme periodic because of TCP-congestion

Simulation Results Delay Jitter of Multimedia Traffic add two UDP streams

Simulation Results Useful Goodput of Multimedia Traffic Useful : packet arrives at the client within one half of the playout interval Useful threshold=0.1spacket size= 900 bytes

Simulation Results Useful Goodput of Multimedia Traffic low packet size, usefulless goodput, variation

Simulation Results Audio Quality Comparison Although JD1 throughput lower, but SNR higher

Conclusion A novel streaming friendly gateway-based buffer management scheme- JD is proposed JD improve QoS of multimedia networks by detecting and discarding multimedia packets with higher jitter Also improve JD scheme with residual hop-count

Chebyshev inequality Given only mean and variance, count an upper bound on the probability that some random variable is >= a set value