From IWCMC 07 August Shing-Guo Chang

Transcription

1 G. A. Ramanujan, Amit Thawani*, V. Sridhar Applied Research Group, Satyam Computer Services Ltd, 3rd Floor SID Block, IISc Campus, Bangalore, INDIA {Ramanujan_GA, Amit_Thawani, K. Gopinath Department of Computer Science and Automation IISc Campus Bangalore, INDIA From IWCMC 07 August Shing-Guo Chang

2 + Intruduction + System Goals + Algorithm design + Experiment + Results + Conclusion

3 + Thin client computing has been in computing niches until the desktop computing model emerged stronger in early 1990 s. + Some key benefits of thin clients. Reduction in desktop maintenance cost. Reduction in bandwidth costs for server centric applications.

4 + More recently,computing in general has moved towards multimedia applications. + Thin client computing still has remained In graphic based circumstance. + For example: Receiving live feeds from a video conference while mobile and simultaneously receiving updates of weather condition and live entertainment audio feed from satellite radio depending on the current position as update by GPS.

5 Thin client feature rich thin client

6 + The performance of TCP connection is heavily affected by UDP. Traditional data application such as http,ftp and telnet employ TCP. Real-time multimedia application such as video conferencing prefer UDP. + Need fairness and minimal QoS. Intermediate routers employ the appropriate packet scheduling mechanisms such as Class-Based Queuing. All router should employ the same scheduling mechanism with same parameter.

7 + An alternative and easier way is to apply the admission control algorithm to UDP and TCP connection,for example: To provide users with meaningful and effective video presentation,the admission control interval should be long enough to avoid frequent video quality fluctuations. + Receiving minimal QoS Control TCP flows by obtaining state info. From receivers using receiver window control available in TCP

8 + Make sure that packet loss ratio of UDP flows are reduced and throughput of TCP flows are either increased or remain same without applying the enhancement. Model a feature rich thin client capable of supporting many current and emerging technologies. Ex: Bluetooth,IPTV,GPS etc. As emerging technologies are moving toward multimedia content which have intrinsic requirements of low delay,low packet loss and less tolerable error.

9 We propose to study the interaction between TCP and UDP when the end system receiving data is a CPU resource constrained thin client. System is designed with the goal of achieving fairness among flows and yet guaranteeing a minimal QoS for flows.

10 + Start with calculating the statistics number of TCP and UDP packets received and sent in that second. Make sure long enough interval and obtain a fair knowledge of the current dynamics. + Execute admission control algorithm and depending on whether there is more or less data than can be processed.

11 + All the statistics of packet loss ratio and end to end delay given by α (current_values) + (1 α) (old_values) + Five case Case1:determine the number of available UDP packets. Case2 :severely lossy UDP flows. Case3 :Either severely lossy TCP flows or TCP flows whose end to end delay are more than the maxmum acceptable delay by the application.

12 Case4:UDP flows are lossy and the total number of packets received. Lost by its lossy nature. Case5:TCP flows are lossy and the total number of packets received. Lost by its lossy nature. + Case2 to case5 are under the condition of available UDP packets is less than CPU can process.

13 + Let PUDP = Packet loss ratio of UDP flows, PTCP = Packet loss ratio of TCP flows, ETCP= End to end delay of TCP flows, Win = Receiver window size, MaxPKT_UDP = Maximum allowable UDP packets ThUDP = Threshold for acceptable UDP loss, ThTCP = Threshold for acceptable TCP loss T = current time, TPKT = Timestamp in packet, MaxPKT_TCP = Maximum allowable TCP packets RecvUDP = No of received UDP packets, RecvTCP = No of received TCP packets, + Max perceivable delay =Maximum tolerable delay by the specific applications + Available processing =Amount CPU resources available to process incoming packets. + Max packets =Maximum packets processable by the system in 1 sec. + AdmitPKT_TOTAL =Total number of packets available for processing after admission control. + K = 2 = constant factor mentioning the difference in processing UDP versus TCP packets.

14 + If: RecvUDP > MaxPKT_UDP + AdmitPKT_UDP = MaxPKT_UDP + Else:....Case (1) + AdmitPKT_UDP = RecvUDP + PUDP = total dropped UDP/total sent UDP + PTCP = total dropped TCP/total sent TCP + ETCP = T - TPKT + If (Admitpkt_udp > Available processing) + If: PUDP <= ThUDP + Do nothing + Else:...Case (2) + PerINCREASE = (RecvTCP/MaxPKT_TCP) + Win = Win + (Win * PerINCREASE) + (The receiver window size changes is communicated implicitly by TCP protocol) + If: PTCP <= ThTCP && ETCP < Max perceivable delay + Do nothing + Else:.Case (3) + PerDECREASE = (RecvTCP/MaxPKT_TCP) + Win = (Win - (Win * PerDECREASE))/K + (The receiver window size changes is communicated implicitly by TCP protocol)

15 + If: PUDP >= ThUDP && RecvUDP > RecvTCP + && AdmitPKT_TOTAL > Max packets...case (4) + PerINCREASE = (RecvTCP/MaxPKT_TCP) + Win = (Win + (Win * PerINCREASE))/K + (The receiver window size changes is communicated implicitly by TCP + protocol) + Else if: PTCP >= ThTCP && RecvUDP < RecvTCP + && AdmitPKT_TOTAL > Max packets Case (5) + PerDECREASE = (RecvTCP/MaxPKT_TCP) + Win = Win - (Win * PerDECREASE) + (The receiver window size changes is communicated implicitly by TCP + protocol)

16 Compute: Calculate the no of packets received from each flows. Assign an initial higher priority to UDP flows Monitor flows for every 1 second interval Repeat: go to compute after every 1 sec to get new aggregate statistic and evaluate changes. The above defined calculations are carried out for every flow and adjustments are sent to every flow.

17 + Using network simulator NS Ten servers stream. Contain up to ten streaming multimedia data and Contain up to ten streaming transmitting TCP data. + Connection contained a mix of wireless and wired links, also contained a mix of real time and non real time flows. + CPU considered 500MHz.

18 TCP overflow condition : five TCP sources each sending data with three wired and two wireless. Two of wired soures had a link capacity of 20 Mbps while one had a link capacity of 50 Mbps. The wireless sources had mobility enabled and where in transmission range for 75% of simulation time. UDP overflow condition : Three UDP sources streaming real time data with two wired sources,each of capacity 20 Mbps and a wireless source with a propagation delay of 100 ms.

19 The UDP packets are controlled through admission control and TCP sources without any loss. Fig 3 and Fig 4 show the results for case1 and case2

20 UDP flows are either almost zero or they are effectively controlled to ensure complete reduction in packet loss. Fig 5 and Fig 6 show the results for case 3 and case 4

21 The transmission of data with the algorithm is delayed due to the applied controlling factor, however on the average case the reduction in packet loss ratio is achieved. Fig 7 show the result for case 5

22 Fig 10.Some resource out of transmission range. Fig 11.the algorithm allows or enables the transmission of a burst of data. Fig 9,Fig 10 and Fig 11 show the results for delay variations

23 + The algorithm does not affect the normal performance of thin client and provides a fair distribution of bandwidth across flows and satisfy minimal QoS regardless of the condition of either overflow or underflow.