Fatal Reordering Problem of Stream Sequence Number in SCTP Stream Buffer of ns2 Network Simulator and Solution

In recent years, a lot of performance evaluation methodologies and tools have been developed within disparate research communities for the purposes of evaluation, design, and model reduction. Among those as a free and powerful evaluation tool, ns2 has attracted more and more users who focus on developing/designing various network protocols. On the other hand, stream control transmission protocol (SCTP) natively supports multi-streaming feature and reorders the out-of-order data chunks, which are stored in stream buffer, based on the stream sequence number (SSN) as per individual stream. Nevertheless, SSN has a 16-bit size and the SCTP receiver of ns2 simply arranges the stored data chunks by the order of their SSNs without other preconditions. In the long-lived SCTP association, however, this may result in a permanent reordering confusion in stream buffer while SSN of any stream wraps back to zero and the stream buffer is not empty then. Eventually, this problem will lead to traffic interruption because of the overflow of the whole receiving buffer and unfortunately impact the evaluation result of the related ideas. This paper points out the potential fatal reordering problem and introduces a simple solution to permanently eliminate this issue. The feasibility of this solution has been proven in our simulations.