On things to happen during a TCP handover

Hansmann, W.; Frank, Matthias

doi:10.1109/lcn.2003.1243118

Cited by 41 publications

(34 citation statements)

References 11 publications

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“…Several problems affect the TCP performance during a VHO procedure [14]; in particular, the sudden BDP variation and a significant change in the RTT. It is important to avoid 'hard' VHO procedures because they entail intervals of channel disruption with the possibility of bursty packet losses.…”

Section: Survey Of Tcp Problems Due To Vhos In the Railway Scenariomentioning

confidence: 99%

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TCP Performance Issues in Satellite and WiFi Hybrid Networks for High-Speed Trains

Giambene¹,

Marchi²,

Kota³

2012

ICST Trans Ubiquitous Env

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GEO satellite communication systems are an efficient approach for broadband Internet provision on highspeed trains, but some work is still needed to allow a seamless service. In the railway scenario, satellite communications suffer from strong variations in the received signal power and need suitable solutions to deal with long channel disruptions due to tunnels. The approach envisaged in this paper is based on a hybrid network (satellite and terrestrial WiFi coverage) and a Vertical Handover (VHO) procedure to switch seamlessly from one segment to another whenever link quality degrades and a new segment is available. This paper deals with the TCP performance in the presence of VHOs (based on the IEEE 802.21 Media Independent Handover, MIH, standard) from the satellite to a terrestrial wireless segment and viceversa to cover tunnels. Details are provided for the adoption of MIH and MIPv6 in such a context, referring to the BSM standard. Design criteria for the WiFi coverage extension outside the tunnel are also presented. Finally, we have shown that TCP goodput behavior and convergence time can be improved by means of suitable accelerated TCP versions or using cross-layer methods.

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Section: Survey Of Tcp Problems Due To Vhos In the Railway Scenariomentioning

confidence: 99%

“…We examine below the detailed effects on TCP behavior in the two possible VHO cases for our train scenario [14], [15]: from satellite to WiFi and from WiFi to satellite. We refer to a mobile collective terminal on the train that receives TCP downstream flows.…”

Section: Survey Of Tcp Problems Due To Vhos In the Railway Scenariomentioning

confidence: 99%

TCP Performance Issues in Satellite and WiFi Hybrid Networks for High-Speed Trains

Giambene¹,

Marchi²,

Kota³

2012

ICST Trans Ubiquitous Env

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“…The reason might be that the affect is minor (cwnd only halved and limited packet retransmission) and TCP can recover from it by itself. Nevertheless, nodupack is proposed in [6] to enlarge the duplicate threshold dupThresh during the handover so more out-of-order packets are tolerated.…”

Section: Related Workmentioning

confidence: 99%

A fast adaptation mechanism for TCP vertical handover

Sleurs

Lil

et al. 2008

2008 International Conference on Advanced Technologies for Communications

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Abstract-In this paper we propose a vertical handover mechanism for TCP to deal with the delay and bandwidth change during the handover. The proposed mechanism relies on the interaction between the sender and the receiver during the handover and requires no a prior information of the new path. The adaptation is triggered by a handover notification at the receiver and finishes in about two round-trip time. Furthermore, it solves the problem of packet reordering and spurious retransmission timeout as well which are also common during vertical handovers. Simulation results show that our mechanism improves TCP performance in various vertical handover scenarios.Index Terms-TCP, Handover, Congestion Control, Mobility.I. INTRODUCTION It is well-known that TCP does not perform well during a handover. A first reason is the possible packet loss during the outage time when the mobile node changes its network connection. Since TCP regards all packet loss as indication of congestion, it will back-off its sending rate unnecessarily. This problem can be readily solved in the network layer with lossless handover techniques such as buffer-and-forward and make-before-break. Unfortunately, this is not the end of problems. When the handover takes place between different type of networks, or in other words, when TCP experiences a vertical handover, the abrupt change in network delay and bandwidth will still affect its performance.When the new path has a higher bandwidth or a lower delay, packets following the new path may overtake those in the old one and arrive at the receiver earlier. Consecutive out-oforder packets can generate enough duplicate ACKs to trigger false fast retransmission while no packet is really lost. On the other hand, when the new path has a lower bandwidth or a higher delay, packets following the new path may not be acknowledged in time, which causes premature RTOs at the TCP sender. All these wrongly triggered congestion responses not only cause unnecessary packet retransmission but also greatly decrease the TCP throughput regardless of the real network conditions. Furthermore, since TCP does not control the sending rate directly but only the number of in-flight packets using a sliding-window based mechanism, it will try to keep the same amount of packets in the network also after a handover. If the Bandwidth-Delay Product (BDP) is changed during a handover -which is very likely the case for a vertical one -TCP will either overrun or under-utilize the capacity of the new path. Because the Additive-Increase MultiplicativeDecrease (AIMD) scheme used in TCP for window adjusting

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“…Some works focus on the out-of-sequence problem. In particular, in [7], the authors analyzed under which situations a handover may falsely trigger the TCP congestion control action. In [6], the authors investigated the behaviors of various TCP versions, including TCP Tahoe, TCP Reno, TCP NewReno and TCP SACK.…”

Section: Problem Statement and Related Workmentioning

confidence: 99%

“…Specifically, we choose a threshold of 0.8 for the weight q(n) of newRTT in Eq. (7). In other words, the number of steps n is determined by how long the newRTT can contribute to more than 80% of SRTT.…”

Section: Scheme 3: Ack Delayingmentioning

confidence: 99%

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

Huang

Cai

2006

IEEE Network

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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.

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On things to happen during a TCP handover

Cited by 41 publications

References 11 publications

TCP Performance Issues in Satellite and WiFi Hybrid Networks for High-Speed Trains

TCP Performance Issues in Satellite and WiFi Hybrid Networks for High-Speed Trains

A fast adaptation mechanism for TCP vertical handover

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

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