Design And Implementation Of TCP Protocol Prototype Based On Network Coding

Because of the design idea of "packet loss due to congestion" for TCP, the transmission performance of this protocol declines sharply in the network environment with a high loss rate. Many improvements were designed to solve this problem, however the starting point was just limited in how to distinguish the reason that causes packet loss or on the transmission parameters adjustment which did not produce the qualitative leap, but the emergence of network coding technology provides a new way to solve this technical problem. Based on the network coding design, the TCP/NC protocol makes full use of the computing capability of nodes and data fusion to break the original data packet sequence. This protocol well shields the calling of control mechanism caused by the network congestion in the premise of not distinguishing the packet loss reason, and improves the performance of transmission in such an awful network environment. However, the protocol only provides a basic framework, and it gives no specific implementation details to carry on the effective coding and decoding operations. Besides, the abundant transmission and computation has not obtained a good optimization. However, high efficiency coding and decoding algorithm is the key to design and implement this protocol. So it needs further research and improvement.In this paper, on the basis of the deep research on network coding technology and TCP/NC protocol, random linear network coding was implemented, and TCP/NC protocol was implemented in the simulation environment, and then a kind of improved coding and decoding algorithm was put forward based on the fixed coefficient matrix. The main research includes the following aspects: (1) A random linear coding and decoding algorithm with a high availability based on Galois field operation was designed. The complexity of this algorithm was well reduced by table look-up, and validated its correctness in the simulation environment.(2) An algorithm verification system with a good scalability for the verification of algorithm’s correctness and complexity was designed.(3) The TCP/NC protocol was implemented by using NS2simulator, and compared with its parent protocol TCP-vegas. The results show that, TCP/NC protocol achieves a throughput of4.7times and8.1times as TCP-vegas under the same condition of network with a packet loss rate of5%and10%. At the same time, the transmission rate reached3.8times and12.1times as TCP-vegas.(4) In the light of the deficiency of random linear coding and decoding algorithm such as the more additional network transmission cost caused by sending coding parameters, and the CPU consumption and time delay produced by the decoding end complex calculation, a fixed coefficient matrix encoding and decoding algorithm was designed in this research, which reduced the cost of network transmission and its complexity. Simulated in the same settings and parameters, a decoding operation performed by the new algorithm can reduce28.9%of the Galois field operations. And the new algorithm has a much lower computational complexity.