Reduced TCP Window Sizefor Legacy LAN QoS II.ppt

Reduced TCP Window Sizefor Legacy LAN QoS II Outline Summary of previous work Basic idea: Reduce TCP window size for LAN traffic! NS simulation results 10-BASE-T measurements NS simulation for extended LAN topology Worst case scenario Is communication between T2s necessary? NS simulation for simple traffic model Average case scenario Bi-directional traffic Future work Scenario: Single Switch LAN Voice is received from WAN File is loaded from file server Both have to go through buffer at output port Basics Idea Reduce TCP window size for intra-LAN traffic No loss in throughput when: NxW = BxD Set TCP window size according to delay constraint DMAX, e.g., DMAX = 10 ms B = 10 Mbps 1480 Byte packets N=2 connection Advertised window in ACK can be modified in T2 without knowledge of sender/receiver NS Simulation Results 10-BASE-T Measurements Scenario: 2 Switch LAN Voice is received from WAN Files are loaded from Bi to Ai Appropriate W depends on N! How bad is mismatch? Is communication between T2s needed? Variation of N, W N={1,2,4,8,16,32} x W={1,2,4,8,16,32,64} Variation of N, W - stretched Similar performance for WxN = const. For W=4 reasonable performance for N16 Scenario: N to N Communication Voice received from WAN Each terminal sends/receives data to/from every other terminal Balanced N to N communication N=8, W={4, 64} Traffic Model and Measurement Random file size Bi distributed uniformly within 4-512 packets(1 packet = 1480 Byte) Waiting time in between file transfers: Voice Delay N=8, l=0.3 Voice Delay - Detail Strong correlation: nice for adaptive play-out control! Future Work Refine traffic model and LAN simulation Implement NS module that acts like T2 Integrate Networking and Signal Processing parts Use trace files from NS simulations for adaptive play-out time control Conjecture: Fixed TCP window is ok, since remaining delay jitter can be controled by adaptive play-out Niko F?rber Sept. 20, 2000 T2 10/100 Legacy Switch Router File Server 100 10 bottl