Implementation of the Network Control Protocol using ECN Bits (eNCP)

Many studies have shown that the transmission control protocol (TCP) which is the major transport protocol in the Internet today is finding it increasingly difficult to cope with the growth of communication network capacities and applications. TCP’s inability to properly utilize network links is one of the problems. Besides, TCP takes a long time to achieve fairness between flows. Many of the new modification of TCP inherit these main problems of TCP. Clean-slate protocols such as the explicit Congestion control Protocol (XCP) which get congestion feedback from routers can fully utilize the links and reduce queueing delays in the path of the flows. But XCP, in addition to having many router computation overheads also takes many rounds to allocate fair shares to flows. To solve the drawbacks of XCP and TCP, we have previously presented a network control protocol (NCP). NCP allocates fair share to flows in one round resulting in increased average file completion time (AFCT) as short flows are not blocked by big file transfer flows. Although smaller than that of XCP, NCP uses a 32 bit additional header in every packet to carry a congestion feedback from the routers in the path of every flow to each source of the flow. Apart from the inconvenience of modifying the TCP/IP packet formats, the additional header may accumulate to cause some increase in AFCT. In this paper we present an efficient implementation scheme (algorithm) of the Network Congestion Control (NCP) protocol using Explicit Congestion Notification (ECN) bits (eNCP). Using this implementation scheme, NCP does not need any additional packet header, avoiding the per packet overhead. In addition to the convenience of not having to change the TCP/IP packet header format, numerical results show that a significant amount of data overhead can be saved using eNCP. Not having to add a layer can also make NCP easily deployable and backward compatible.