Analysis of TFRC in Disconnected Scenarios and Performance Improvements with Freeze-DCCP

We present enhancements to the TCP-Friendly Rate Control mechanism (TFRC) which are designed to better cope with the intermittent connectivity available to mobile devices or in Delay Tolerant Networks. Our aim is to prevent losses during disconnected periods and quickly adapt to new network conditions. We propose to suspend the transmission before disconnections occur in a way inspired by Freeze-TCP, then probe, in a new way, the network after reconnecting to enable full use of the newly available bandwidth. We rst evaluate the potential performance gains for realistic network parameters. We then describe the proposed additions to TFRC and their implementation within the Datagram Congestion Control Protocol (DCCP) in ns-2. Comparisons of simulation results for example mobility scenarios show that the proposed enhancements enable faster recovery upon reconnection as well as signicantly improved adjustment to the newly available network conditions.