Adapting NORM Unicast Transport for Loss Tolerant and ECN Environments

This work presents new experimental results examining the loss tolerant unicast congestion control behavior of the NACK-Oriented Reliable Multicast (NORM) transport protocol documented initially as Internet Proposed Standard, Request for Comments (RFC) 5740. While RFC 5740 specifies a reliable multicast UDP-based transport protocol, NORM also has the ability to provide loss tolerant UDP unicast reliable transport that is well-suited for lossy wireless environments where protocols like TCP may not perform well. In addition, we introduce the design and use of a unicast SOCKS proxy for the NORM protocol called the NACK-Oriented Proxy (NORP) and validate the results of NORP performance against other NORM unicast experimental results. The availability of NORP will reduce the transition risk and improve the use of NORM unicast capabilities by not requiring end system application modifications. Our results examine a number of unicast congestion control variants of the NORM protocol, including an explicit congestion notification (ECN) mode, within an emulated lossy link modeled network environment. We include COTS hardware routing and radio-to-router interface (R2RI) within the test environment to examine and validate the use and performance of ECN-based packet marking and improved cross-layer flow control when available. The initial experiments demonstrate the significant advantage of using ECN-based assistance within error-prone wireless environments. We also show increased performance of an additional loss tolerant mode that does not require ECN infrastructure support. Coexistent transport fairness results show that NORM unicast modes are friendly to both inter-protocol flows (e.g., TCP flows coexisting) and to intra-protocol flows (e.g., Other NORM flows coexisting). We conclude by summarizing findings and discussing future work planned.