Tcp The Over Hylabs Performance Analysis

Hybrid optical switching networks, which make use of the advances of Optical Circuit Switching (OCS) and Optical Packet Switching (OPS)/Optical Burst Switching (OBS), have recently received a lot of attentions. A novel hybrid network architecture—Hybrid Lightpath And Burst Switching(HyLABS) which has been proposed recently can alternate packets'switching mode between OCS and OBS dynamiclly according to traffic load. As the most importmant protocal working in Transport Layer, to analyze the performance of TCP(Transport Control Protocal) in the HyLABS networks is very essential.The second chapter analyzes the performance of TCP on HyLABS networks by simulation. The first part finds that the change of transport mode will cause the packets'disorder when the TCP packets in the same connection transport in two different ways and then a special issue named false fast retransmit (FFR) will generate at the sender. The second part presents the throughput of different versions of TCP and we analyze the results. From the results, we find that the throughput of Vegas is lower than others and that's decided by it's special congestion control mechanism. To address the disorder problem of TCP traffic in the HyLABS networks, we propose two modified algorithms named S-DRA and R-DGA at the third chapter.The former delays the response of congestion control when receiving three duplicate ACKs for a interval at the sender. The latter delays the generation and transmission of duplicate ACK at TCP's receiver.At last,we compare the performance of S-DRA,R-DGA and TCPReno. Simulation results show that the two new algorithms can reduce the issue of FFR efficiently and improve the throughput of TCP over HyLABS.The window's rule of Vegas protocols has been changed during the slow start and congestion avoidance phrase in the third chapter. The init purpose of Vegas protocols is to adjust the length of the congestion window by changing the packet's round-trip-time (RTT) on a network with buffer. The Vegas protocols are not available in the HyLABS network because the OBS layer don't need buffer, the OCS layer won't lose any packet for the reason of buffer and both transport sachems have different influences on the RTT. Our paper proposes an improved protocol called Vegas-Hy on the basis of Vegas protocol. We change the condition and rule of adjusting length of the congestion window in the phase of congestion-avoiding and slow-starting to make it fit for the HyLABS network. In the last part, we compare the performance of Vegas-Hy and Vegas in the same condition and find Vegas-Hy performs better than Vegas.