RLC buffer occupancy when using a TCP connection over UMTS

Bestak, Robert; Godlewski, Philippe; Martins, Philippe

doi:10.1109/pimrc.2002.1045210

Cited by 15 publications

(18 citation statements)

References 6 publications

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“…In accordance to previous works [9], our simulation experiments show that, for a single TCP flow the RLC buffer occupancy corresponds approximately to the window size, given that the radio bearer is the bottleneck link. When several flows are multiplexed, the window sizes are smaller than BO.…”

Section: Second Mechanism: Single Packet Discardsupporting

confidence: 90%

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Combining ACK rate control and AQM to enhance TCP performance over 3G links

Alcaraz

Cerdan

2006

Proceedings of the ACM International Workshop on Performance Monitoring, Measurement, and Evaluation of Heterogeneous Wireless

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When TCP is carried over 3G links, overbuffering and buffer overflow at the RLC layer degrades its performance. In order to prevent these undesired interactions, we propose an algorithm that combines two strategies. If the congestion state of the downlink buffer is moderate, the protocol uses ACK rate control to adjust the sending rate of the source. If the buffer occupancy reaches certain threshold, a single packet is discarded to trigger TCP congestion control measures. By means of extensive simulation experiments, we disclose the influence of each parameter on TCP performance, finding several configurations that improve end-toend goodput while reducing the delay. The proposal is compared to other approaches, showing a better and more stable behaviour. The operation of the algorithm is deterministic; it does not require changes in 3G specifications nor in end user's protocol stack, and preserves TCP end-to-end semantics.

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Section: Second Mechanism: Single Packet Discardsupporting

confidence: 90%

“…The consequence is that, as described in [9] frame losses in the downlink channel result in higher RLC buffer occupancy at the network side. Considering that the current RLC specification propose a drop-tail scheme, the buffer may overflow causing consecutive packet losses.…”

Section: Motivationmentioning

confidence: 99%

Combining ACK rate control and AQM to enhance TCP performance over 3G links

Alcaraz

Cerdan

2006

Proceedings of the ACM International Workshop on Performance Monitoring, Measurement, and Evaluation of Heterogeneous Wireless

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“…Some studies focus on the interplay between the polling and status triggers and their related timers, as the frequency of Status Protocol Data Units (PDUs) affects both link overhead and packet delay [1], [21], [27], [32]. Other studies focus on the impact of the RLC window size (in PDUs) or buffer size [in Service Data Units (SDUs)] on throughput; buffers must be large enough to avoid stalling during bad channel periods [1], [5], [14], but not too large to avoid building up queues that reduce the TCP transmission rate [26]. Other studies examine the impact of the SDU discard policy on throughput: it has been noted that the discard SDUs after a timeout option strongly depends on the link bandwidth [32].…”

Section: Related Work and Contributionmentioning

confidence: 99%

Link Layer Adaptation for Shared Wireless Links

Xylomenos¹,

Makidis²

2008

Mobile Netw Appl

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Abstract-While traditional link layer protocols assume that they fully control the underlying link, in contemporary wireless networks the link may be dynamically shared by sessions belonging to different users and/or applications. To assess the impact of link sharing, we measure the File Transfer and Web Browsing throughput achieved over a Selective Repeat (SR) protocol, with or without contention from Media Distribution. Our results indicate that the optimal protocol settings strongly depend on the level of contention for the link. We therefore present two link layer protocols that adapt to the available bandwidth, our Adaptive Selective Repeat (ASR) protocol which dynamically modifies its retransmission timeouts, and the Radio Link Control (RLC) protocol specified for use by UMTS networks which does not employ retransmission timers. We first repeat our performance measurements to determine the optimal settings for each protocol, and then compare the fine tuned versions of all protocols with respect to their File Transfer and Web Browsing throughput, as well as to the delay induced to the contending Media Distribution packets. Our results indicate that while both RLC and ASR are more stable than SR, the complex RLC does not match the performance of our simpler ASR. Index Termsink Layer Protocols, Adaptive Selective Repeat, Radio Link Controlink Layer Protocols, Adaptive Selective Repeat, Radio Link ControlL

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“…Previous works [5,9,10] provide a clear view of the characteristics of 3G wireless links. Radio bearers are expected to multiplex a number of simultaneous connections ranging from 1 to 4 TCP flows [5,11], because 3G links employs per-user buffering.…”

Section: Characteristics Of 3g Linksmentioning

confidence: 99%

“…At the RLC layer, the upper layer packets will be stored in the downlink buffer until they are fully acknowledged by the receiver side. In consequence, as described in [4,10] frame losses in the downlink channel result in higher RLC buffer occupancy at the network side. Considering that the current RLC specification [1] proposes a droptail buffer, the buffer may overflow causing consecutive packet losses.…”

Section: Characteristics Of 3g Linksmentioning

confidence: 99%

Performance Evaluation of AQM Schemes in Rate-Varying 3G Links

Alcaraz

Cerdan

2006

Personal Wireless Communications

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Abstract. When TCP is carried over 3G links, overbuffering and buffer overflow at the RLC layer degrades its performance. AQM techniques at the RLC buffer can bring noticeable enhancements to TCP performance without introducing changes in 3G specifications. We show that the optimum parameter setting of AQM algorithms in RLC buffers is strongly related to the radio bearer rate, which can be changed dynamically by control layer protocols. By means of extensive simulation experiments we propose, for each specified nominal rate, optimum configurations that keep the goodput near the maximum while the delay is reduced up to 50%. We consider two AQM schemes, an adapted RED algorithm and a novel deterministic one, SBD described in this paper. We illustrate how an automatic reconfiguration of AQM parameters avoids the degradation caused by sudden changes in the radio bearer rate.

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RLC buffer occupancy when using a TCP connection over UMTS

Cited by 15 publications

References 6 publications

Combining ACK rate control and AQM to enhance TCP performance over 3G links

Combining ACK rate control and AQM to enhance TCP performance over 3G links

Link Layer Adaptation for Shared Wireless Links

Performance Evaluation of AQM Schemes in Rate-Varying 3G Links

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