Sechang Son Computer Sciences Department University of Wisconsin-Madison Network Bandwidth Regulation

Outline › Bandwidth Regulation Model › Goals and Approaches › Overall Scheme › Cedar’s Local Regulation › NetMnger’s Global Regulation › Future Work

Bandwidth Regulation Model

Goals › Controlled use of bandwidth › Not monopolizing network › Why not TCP?  TCP congestion control does not distinguish between user process and Condor process  We want to give more bandwidth to user process

Approaches › Focus on mechanism › No change to existing Cedar interface  Cedar = network layer of condor  Compatibility issue › Simple manager implementation

Overall Scheme

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Cedar’s Local Regulation › Bandwidth Allocation › Bandwidth Regulation › Congestion Detection & Control

Bandwidth Allocation › (window, maxBytes, maxPercent)  Do not send, in any case, more than maxBytes bytes during window sec  If congestion occurs, back off to maxPercent % of what you could send at the time of congestion

Bandwidth Regulation › Moderate level of short burst is allowed › Can’t saved too much bandwidth for later use › When (100M, 100sec, 80%) is given  Can send up to 10M(> 6M) during 6sec  Can’t send 90M during 25sec, even if only 10M has been sent during 75sec

Congestion Detection & Control › Detection  Measure time taken to send a packet  Check the number of bytes sent by TCP › Control  Back off to the given percent in allocation  Remain backed off for a while  Gradually try more bandwidth

NetMnger’s Global Regulation › Bandwidth (Re)Allocation › Congestion Control

Bandwidth (Re)Allocation › Even distribution of bandwidth among Condor connections › Periodic polling of network usage and condition › Reallocation occurs when  Extra bandwidth needed: new connection  Free bandwidth found: close report, less usage  Congestion reported

Congestion Control › If any of Cedar reports congestion, NetMnger backs off every Cedar sharing the network › If every Cedar reports No congestion, NetMnger gives the original bandwidth to each Cedar

Further Work › The study of relationship to TCP’s congestion control › Congestion Avoidance  E.g TCP Vegas mechanism

Thank You