XCP is a feedback-based congestion control system that uses direct, explicit, router feedback to avoid congestion in the network. It is designed for both scalability and generality. It was developed by Dina Katabi, starting from a suggestion by Mark Handley (refer to [] for detailed descriptions). The ns code for XCP which was originally developed by Dina Katabi was modified, extended and integrated into ns-2.28 at USC/ISI. It still continues to evolve as of today. If you are interested in looking at Dina's original source code please go to her website at https://www.ana.lcs.mit.edu/dina/XCP/