Streaming Video over TCP with Receiver-based Delay Control Shruthi Victor Maria Amrita Chowdhury

Roadmap Introduction Traditional TCP Exact RDC 1 bit RDC Simulation Results Layered Video Streaming Conclusion

INTRODUCTION TCP , a dominant transport layer protocol in current Internet. Good congestion control capabilities. Unicasting video streams over TCP connections: A Real Challenge Delay and Throughput Variation of TCP connection –a major problem for video source

OBJECTIVE Receiver Based Delay Control(RDC) mechanism with TCP solves the problem.. Complexity of Congestion Control Algorithm of TCP left unaltered Changes only the TCP Receiver Side by extending the ACK Delay

RDC Demonstrating Traditional TCP, Exact RDC and 1 Bit RDC Comparison between traditional TCP and Exact RDC Comparison between Exact RDC and 1Bit RDC

TRADITIONAL TCP Router includes FIFO Buffer. Incoming packets forwarded to the buffer and drained to the outgoing link Buffer occupancy increases when arrival rate exceeds departure rate Packet dropped when buffer is exhausted

EXACT RDC Router includes FIFO Buffer and the token bucket Keeps the occupancy of the FIFO low by using the token bucket Token bucket used to calculate the delay for each packet and the delay appended to the outgoing packet Receiver delays the ACK depending on the delay value

EXACT RDC Token buffer drain rate < outgoing link rate Packet Delay computed as Dlocal=Ttransmission X (Otb-Ofifo) Ttransmission - Packet transmission time Otb-Token Bucket Level Ofifo-FIFO Level D=Max(Dlocal, Dincoming) Dincoming-Incoming appended Delay

Properties of Exact RDC Reduced Number of Timeout –TCP Rate =cwnd/RTT To reduce TCP Rate- RTT is increased Reduce Network Queueing Delay

1 Bit RDC Delay is encoded in 1 bit determined by the difference between the token buffer level and FIFO buffer level The receiver adjusts the ACK delay based on the percent of the received packets with the CE bit set

1 Bit RDC 1 bit RDC is based on multiplicative increase and additive decrease of delay Dn+1 = 2 X Dn Dn+1> Dn Dn+1 = (cwnd/(cwnd+1)) X Dn Dn+1<Dn

Exact RDC v/s 1 Bit RDC In exact RDC, calculated delay reflects the exact congestion level and the receiver can quickly adjust. In 1 bit RDC the delay is just an approximated value

EXACT RDC v/s 1 bit RDC IP header can not accommodate multi bit delay value 1 bit RDC , employs a CE bit in the IP header to accommodate the delay value

Using this simulation model 4 systems are compared: 1)Drop Tail 2)ECN 3)Exact RDC 4)1 bit RDC

Simulation

Layered Video Streaming Hierarchically Encoded Video Each layer requires same delivery bandwidth Data of a layer is played only if subsequent lower layers are received Additional layers enhances playback quality at the cost of more bandwidth

TCP as the Transport Protocol Traditional TCP not suitable for real time applications i.e. streaming purposes TCP connections introduce bandwidth and delay variations Retransmission in TCP ensures reliable data communication but might induce playback latency in the system

Video Source Streaming Algo Dynamic decision to add/drop a video layer Decision is based on observed occupancy of the TCP sending buffer and the buffer size

Video Source streaming Algo

Simulation Different Simulation Cases -10 Stream Data Simulation -Streams with Different Round Trip Time

Simulation-10 Stream

Simulation-10 Stream

Simulation-100 Stream

Simulation-Different Round Trip Time

Performance Summary Exact RDC and 1Bit RDC performs better than the DropTail and ECN method Exact RDC performs better than 1Bit RDC 1Bit RDC is easy to implement

Conclusion TCP connections with Receiver-based Delay Control (RDC) works well for carrying layered video streams. 1-bit RDC do not use accurate delays Additionally, a method for streaming hierarchically-encoded layered videos over TCP connections.

Conclusion RDC connection - utilize available bandwidth -reduce playback latency -friendly to competing TCP connections Combination of our RDC and layered video source algorithms offers an attractive approach to streaming video over IP networks.

Our Suggestions on the Paper The paper is written in a lucid language and is very easy to understand. There are lots of simulation results which makes understanding better. The paper describes the streaming of video using an algorithm that is only simulated not implemented in real world. So we can’t be very sure of the success rate of the algorithm.

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