Research On SCTP-based Concurrent Multipath Transfer Load Balancing And Retransmission Policies

With the improvement of Internet, end-to-end communication protocol based on transport layer singlehoming such as TCP and UDP are challenged in aspect of transmission performance, fault tolerance and security. The emergence of end-to-end communication protocol with transport layer multihoming such as SCTP-based CMT (Concurrent Multipath Transfer) greatly improved the end-to-end throughput and network resources utilization. With the extensive application of CMT, how to build a high-performance, scalable and highly available SCTP-based CMT load balancing mechanism so as to meet the emerging needs of large-scale application of SCTP is a current hotspot. In addition, because the data retransmission can not be avoided and the fact that the existence of the finite receive buffer, the pros and cons of CMT retransmission policies will directly affect the level of receive buffer blocking, so CMT retransmission policies plays an important role in guarantee the performance of the multipath transmission and the study on this issue has also become the focus of the field.At present, the problems of CMT load balancing and retransmission policies are as follows:(1)the standard SCTP congestion control mechanisms based on association are significantly limited in support of CMT load balancing application. In addition, the CMT load balancing has to face the issue of packet reordering and TCP-friendliness; (2) the existing CMT retransmission policies can not handle very well with the problem of "receive buffer blocking" for the lack of comprehensive consideration with network performance parameters. This problem has constrainted the improvement of the CMT end-to-end throughput.This paper analysis these two issues in-depth and points out the corresponding solutions: (1) did three aspects expansion for the SCTP with the CMT load balancing issues, namely the congestion control mechanisms based on path, the bandwidth-aware scheduling algorithm and the sharing bottleneck detection and recovery mechanisms, raised the Sub Path Congestion Control SCTP (SPCC-SCTP) to extend the standard SCTP and verified the rationality and effectiveness of the proposed load balancing mechanism by simulation. This mechanism enhanced the capacity of the CMT load balancing; (2) did potential changes to the CMT retransmission mechanism against the problem of the existing CMT retransmission policies and proposed RTX-CSL retransmission policies (Retransmission-Congestion window and Slow start threshold and Lossrate) based on an integrated parameters.Verified the rationality and effectiveness of the proposed policies and the simulation test results show that the strategy avoid the receive buffer blocking problem to some extent.Finally, the paper gived the summary of the subject and outlook the research work of future.