tailieunhanh - Grid networks enabling grids with advanced communication technology phần 6

Một phiên họp quản lý thực hiện bắt đầu khi một thứ tự công việc được gửi đến các máy chủ tính toán từ xa. Tại các máy chủ từ xa, yêu cầu gửi đến nhiều cấp độ kiểm tra an ninh. WS-Security cơ chế được sử dụng để xác nhận yêu cầu và xác thực người yêu cầu. | 156 Chapter 8 Grid Networks and TCP Services Protocols and Technologies Figure . Queue size for different TCPs. FAST HSTCP -X Scalable Reno a BIC-TCP -HTCP Behaviour of Different Protocols over 10 Mbps Lossy Link with 50 ms RTT 10 6 ẵ 4 2 8 0 0 Loss rate Figure . Loss response for different TCPs. Enhanced Internet Transport Protocols 157 ENHANCED INTERNET TRANSPORT PROTOCOLS As noted a number of research projects have been established to investigate options for enhancing Internet transport protocol architecture through variant and alternative protocols. The following sections describe a selective sample set of these approaches and provide short explanations of their rationale. Also described is the architecture for the classical TCP stack which is useful for comparison. TCP RENO NEWRENO TCP Reno s congestion control mechanism was introduced in 1988 9 and later extended to NewReno in 1999 6 by improving the packet loss recovery behavior. NewReno is the current standard TCP found in most operating systems. NewReno probes the capacity of the network path by increasing the window until packet loss is induced. Whenever an ACK packet is received NewReno increases the window w by 1 w so that on average the window is increased by 1 every RTT. If loss occurs the window is reduced by half 1 ACK w w - w w Loss w - 2 This type of control algorithm is called Arithmetic Increase Multiplicative Decrease AIMD and it produces a sawtooth window behavior as shown in Figure . Since the arrival of ACK packets and loss events is dependent only on the RTT and packet loss rate in the network p researchers 10 have described the average rate Figure . TCP Reno AIMD throughput RTT windows size queue size. 158 Chapter 8 Grid Networks and TCP Services Protocols and Technologies of the Reno by x 15 2 3 MSS RTT -Jp bps where MSS is the packet size. Note that the rate depends on both the loss rate of the path and .