1 0011 0010 1010 1101 0001 0100 1011 Patcharee Basu, Kanchana - - PowerPoint PPT Presentation

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1 0011 0010 1010 1101 0001 0100 1011 Patcharee Basu, Kanchana - - PowerPoint PPT Presentation

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A Reliable Multicast for Unidirectional Satellite Link <RMUS> 1 0011 0010 1010 1101 0001 0100 1011 Patcharee Basu, Kanchana Kanchanasut yoo@soi.ne.jp, kk@cs.ait.ac.th intERLab Asian Institute of Technology Objectives 0011 0010 1010

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A Reliable Multicast for Unidirectional Satellite Link <RMUS>

Patcharee Basu, Kanchana Kanchanasut

yoo@soi.ne.jp, kk@cs.ait.ac.th

intERLab Asian Institute of Technology

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Objectives

  • File distribution for Education satellite link

– Class materials – Archive lectures

  • HTML pages
  • Video files
  • Image files
  • Many receivers in rural areas

– poor Internet connectivity

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Unidirectional satellite link

Unidirectional Satellite Link Feed router Receiving routers UDL Receiving networks UDL feeding networks

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Unidirectional Link Routing (UDLR)

Unidirectional Satellite Link Feed router Receiving routers UDL Receiving networks UDL feeding networks

Internet

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Satellite UDL & IP Multicast

  • Strengthen the broadcasting property
  • Minimum bandwidth consumption
  • Used for massive information delivery

– Video streaming – Content distribution (Unreliable datagram?)

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Concerns

  • Application

– Need of Reliability – Not time-sensitive

  • Satellite UDL

– Downstream link

  • High bandwidth
  • Long delay

– Return paths

  • Receivers do not share the same return path
  • As good as the worst one

– Long delay (Satellite) – Low bandwidth (Dial-up modem)

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Reliable Multicast for Unidirectional Satellite Link( RMUS)

  • Error Control
  • Error detection

– NAK-based receiver-initiated

  • Error recovery

– Selective repeat

  • Congestion Control
  • Congestion Detection

– Modification of Monitor-Based Flow Control (MBFC)

  • Rate adjustment

– Congestion management

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Error Control(1)

  • Error detection

– Identification

  • Receiver (IP, Process ID)
  • Packet (Sequence Number)

– Detection mechanism

  • Receiver detects the loss
  • Sender polls for reception results
  • Receiver reports the reception result back only at the

end of the transmission

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Error Control(2)

  • Error Recovery

– Selective repeat

  • Retransmit only the loss packets

– Initiate a new data transmission cycle

  • Treat the lost packets in the previous cycle as data
  • Exclude receivers who has completed the

transmission

– RESENT-RETRY

  • Current implementation is 10
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Error Control

SENDER #1 #2... #N RJ Q u e rytim e in te rv a l Start data transmission Send a join message (IP, Process ID) Report data loss

  • r completeion

Start next session until all receivers transfer complete RECEIVERS Data transmission Queries for receivers RQ End of data transmission Polling for reception report Report data loss

  • r completeion

Q u e rytim e in te rva l POLL_ALL Data transmission

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Congestion Control(1)

  • Monitor the network condition

– Modification of Monitor based flow control (MBFC),

  • T. Shiroshita, T. Sano, O. Takahashi, N.

Yamanouchi, 1997

  • Divide the data transmission into sessions

(monitoring region)

  • Sends a number of packets
  • Collect reception report from all receivers{NACK
  • r ACK)
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Congestion Control(2)

– 2 thresholds for controlling the transmission rate

  • THup and Thdown

If (ACKs/N) > Thup then Increase the rate Else If (NACKs/N) > Thdown then Decrease the rate Else Keep the current rate

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MBFC

SENDER #1 #2... #N DATA ACK or NACK Backoff time Return reception result ACK = Complete NACK = Detect Loss Adjust transmission rate and continue send next region RECEIVERS monitor region DATA MS monitor region MS Send control packet monitor region MS ACK or NACK DATA

TMON =?

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TMON for UDL

TMON = DUDL + DRTP + TBACKOFF TMON : Time interval of the monitoring region DUDL : Delay of the unidirectional satellite link DRTP : Delay of the return path TBACKOFF: Backoff timeout to prevent ACK implosion at the sender Maximum delay

  • f all return path

= DUDL TMON = RTTUDL+ TBACKOFF TMON : Time interval of the monitoring region DUDL : Delay of the unidirectional satellite link DRTP : Delay of the return path TBACKOFF: Backoff timeout to prevent ACK implosion at the sender

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Rate Adjustment

  • Normal network condition(without congestion)

– TCP,MBFC : Slow start and Additive increase

Initial congestion window = Maximum segment size (MSS) threshold = 64k

– Additive increase is too slow for the long RTT network

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Rate Adjustment

  • Normal network condition(without congestion)

– RMUS : slow start and additive increase

  • Initial congestion window = RMUS segment size(RSS)

– In our implementation, RSS= 8*MSS

  • Threshold is set as RMUS threshold (Rthresh)

– In our implementation, Rthresh = 128K

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Rate Adjustment

  • Congestion case

– TCP use multiplicative decrease – RMUS gradually decrease by RSS/2

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Scalability

  • Backoff timeout

– Reduce the density of workload on processing receivers’ requests – Reduce the density of traffic caused by receivers’ messages

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Scalability

  • Workload of sender ~ Backoff timeout

Number of receivers

  • RMUS with Adaptive Tmon

TMON = RTTUDL+ TBACKOFF where TBACKOFF = Fn( Number of receivers)

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Experiment

  • Actual UDL satellite network
  • Asian Internet Interconnection Initiatives

project (www.ai3.net)

  • 9 Mbps C band satellite link
  • Feed at Japan
  • Receivers at Thailand, Indonesia, Japan’s

receiving site.

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Experiment network

  • LAN
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Experiment network

Return path Delay (ms) Receiver 1 LAN 0.119 Receiver 2 Bidirectional satellite 270 Receiver 3 Regular Internet 124 Receiver 4 Regular Internet 150

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Experimental Variables

RMUS parameter Value THUP 0.9 THDOWN 0.3 Backoff time 0.3 second

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Evaluation

  • Comparison of RMUS, MBFC,TCP on

– Performance

  • Transmission rate

– Overhead

  • Amount of overhead on return path
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Rate Adjustment

1000 2000 3000 4000 5000 6000 2 5 5 7 5 1 1 2 5 1 5 1 7 5 2 2 2 5 2 5 2 7 5 3 3 2 5 3 5 3 7 5 4 4 2 5 4 5 4 7 5 Time (second) Rate (kbps) TCP MBFC RMUS

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RMUS & TCP

1000 2000 3000 4000 5000 6000 5 5 9 5 1 4 1 8 5 2 3 2 7 5 3 2 3 6 5 4 1 4 5 5 5 5 4 5 5 9 6 3 5 6 8 7 2 5 7 7 8 1 5 8 6 9 5 9 5 9 9 5 Time (second) Rate (kbps) TCP RMUS

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MBFC & TCP

200 400 600 800 1000 1200 1400 5 5 1 1 1 6 5 2 2 2 7 5 3 3 3 8 5 4 4 4 9 5 5 5 6 5 6 6 7 1 5 7 7 8 2 5 8 8 9 3 5 9 9 1 4 5 1 1 1 1 5 5 1 2 1 1 2 6 5 Time (second) Rate (Kbps) TCP MBFC

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RMUS 2 flows

500 1000 1500 2000 2500 3000 3500 4000 4500 5000 40 80 120 160 200 240 280 320 360 400 440 480 520 560 600 640 680 720 760 800 840 Time (second) Rate (Kbps) RMUS flow 1 RMUS flow 2

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RMUS 3 flows

  • Time (second)

Rate (Kbps)

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RMUS 4 flows

  • Time (seond)
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RMUS & Realtime

1000 2000 3000 4000 5000 6000 4 8 1 2 1 6 2 2 4 2 8 3 2 3 6 4 4 4 4 8 5 2 5 6 6 6 4 6 8 7 2 7 6 8 8 4 Time (second) Rate (Kbps) RMUS Realtime

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Acknowledgement Overhead

10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 1 2 3 4 5 6 7 8 9 10 Data size (Mbytes ) Control data (bytes) TCP RMU MBFC

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Applications

  • RMUS FTP
  • Web cache object distribution
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Applications

  • MTM <Multicast tree mirroring>

– SOI Asia , WIDE project

  • Real time digital class on the satellite UDLR environment
  • 7 countries, 13 partners <expanding to Bangladesh, Mongol,

Cambodia, Nepal>

– Class materials/archive lectures distribution – 6 receivers at the moment <1 Thailand, 4 Indonesia, 1 Malaysia >

  • Launched 9 September 2004
  • 6 lecture materials
  • ppt and pdf (12-130 MB)
  • 5 archive lectures
  • html files <1-100 KB>
  • video files <300-600 MB>
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Conclusion

  • RMUS takes care the unique characteristics
  • f UDL satellite link

– High-bandwidth long-delay downstream link – Different types of backward communication channel

  • Error control

– Receiver-initated + selective repeat recovery

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Conclusion

  • Congestion control

– Slow start+ additive increase and gradually rate reduction when congestion occurs

  • Scalability

– Adaptive Tmon value proportional to number

  • f receivers

– Simulation (future study)

  • Faster transmission with low overhead
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Thank you