Adding network-layer intelligence to mobile receivers for solving spurious TCP timeout during vertical handoff

Abstract

With the help of Mobile IP/IPv6 and soft handoff, on-going TCP sessions can remain active and handoff packet loss can be avoided. However, TCP still faces several performance degradation issues due to the disparities in bandwidth and propagation delay between different access networks. Particularly, during vertical handoffs, some undesirable phenomenons may erroneously trigger TCP congestion control actions and thus degrade TCP performance. In this paper, we tackle the spurious timeout problem frequently associated with handovers from fast to slow links. We propose three network-layer schemes: Fast ACK, Slow ACK and ACK Delaying. These schemes require only minor modifications to the network layer of mobile receivers and no change to the TCP protocol and the TCP sender. Simulation results show that these schemes can effectively improve TCP performance during soft vertical handoffs.

Multi Radio Resource Management over WiMAX-WiFi Heterogeneous Networks: Performance Investigation

“…In the latter case some advanced technique must be implemented in order to reduce the packet losses during handovers: for example, packets duplication over the two technologies during handovers is proposed for voice calls in (Ben Ali & Pierre, 2009), for video streaming applications in (Cunningham et al, 2004), and for TCP data transfers in (Naoe et al, 2007) and (Wang et al, 2007). (Rutagemwa et al, 2007) and (Huang & Cai, 2006) suggest to use the old connection in downlink until the base-station's queue is emptied while the new connection is already being used for the uplink. Since the issue of vertical handover is besides the scope of this work, hereafter vertical handovers are assumed to be possible and seamless to the end user.…”

A Cross-Layer Scheme for Inter-RAT Handover from WiMAX to UMTS

“…The problems about inter-RAT handover have been extensively studied by numerous references [1][2][3][4][5]. These problems, such as long handover latency, BDP (Bandwidth Delay Product) mismatch, delay spikes, packet losses, premature timeout, false fast retransmit and spurious RTO (Retransmission TimeOut) [1], cannot be resolved in total by only one scheme at a time.…”

“…In [1], the timeout problem during vertical handover is fixed by using timestamp in WP-TCP header, which is not applicable for other existing TCP variants. It should be noted that reference [5] proposes to delay the RTT iteratively to a proper value before a vertical handover to avoid premature timeout. Unfortunately, the RTO algorithm and parameters of TCP sender must be available for TCP receiver.…”

“…For the occasional inter-RAT handover scenario, we will apply ACK Delaying scheme [5] to gradually eliminate the usage of "spoofed" ACK timer and retransmit timer in TCP proxy, which will be specified in detail in a future article.…”