Transmission Control Protocol Layer Research Articles

Impact of buffering time reduction on false congestion detection in TCP vegas over OBS networks

Since Transmission Control Protocol (TCP) is the dominant protocol on the Internet and optical burst switching (OBS) networks represent the optical transmission solution that can meet future high bandwidth requirements, TCP and OBS networks represent a possible combination for the next-generation Internet. However, a problem with this combination model is that operations at the OBS layer need to be controlled so that false congestion detection at the TCP layer is minimised. Considering the combination of TCP Vegas and OBS, congestion detection at the TCP layer is based on the round-trip time (RTT), where congestion is detected if the current RTT exceeds a given RTTmax. The extra delay may be due to some actual loss, but it may also be due to the extended execution time caused by some OBS layer operations. Therefore, reducing the time of operations at the OBS layer will reduce false congestion detection at the TCP layer. This paper investigates the impact of reducing the buffering time at the ingress node on the false congestion detection rate at the TCP layer. The reduction of the burst buffering time is accomplished by nesting the offset time in the assembly time. The simulation results and analysis show that the transmission efficiency in TCP Vegas over OBS networks is significantly improved; the throughput remains high, and the delivery success rate is significantly increased compared to the conventional buffering mode.

Content and buffer status aware packet scheduling and resource management framework for video streaming over LTE system

With the development of the video encoding and wireless communication technologies, DASH (Dynamic Adaptive Streaming over HTTP) services have an increasing and great share of all the mobile services. However, we find some problems which still need to be addressed for DASH service optimization: (1) the limitation of the video segment representations cannot keep pace with the change of wireless channel states; (2) the characteristics of the video transmission have been not fully utilized in current DASH services; and (3) long interruption time will yield poor QoE (Quality of Experience). To solve these problems, we build a new transmission architecture by modifying the traditional TCP transmission flow. We first add a TCP (Transmission Control Protocol) proxy responsible for discarding the expiry packets automatically before putting them into the TCP sending window and then build a “ACK (acknowledgement) reconstruction module” to reconstruct the received ACK for concealing the packets discarded by the packet scheduler. Based on the new framework, we explore the interdependence among all the packets from the encoder to indicate the importance of each packet and update the interdependence relationship of every scheduling period based on the feedback ACK information. At MAC (Media Access Control) layer, a buffer status estimation module is employed to estimate the client buffer and playback information, which can be used to calculate the packet urgency. Then, a cross-layer design, which consists of an application layer of media server and client, TCP layer, MAC layer, and physical layer, is formulated and the packet scheduling and resource allocation can be jointly optimized. At client, through the analysis of the status of client buffer and MAC queue, an adaptive segment request scheme is developed to determine how and when to send the segment request. Simulation results show that the proposed algorithms can efficiently improve the received video quality as well as the playback continuity compared with other existing algorithms.

Refining TCP's RTT dependent mechanism by utilizing link retransmission delay measurement in Wireless LAN

SummaryNetwork utilization by legacy transmission control protocol (TCP) is determined by its round trip time (RTT) dependent mechanism for the growth of its sending rate. The RTT does not always reflect the actual network conditions, especially in the case of wireless local area network (WLAN). Consequently, it influences the RTT‐dependent mechanism falsely. This paper proposes a novel cross‐layer scheme between TCP and the Institute of Electrical and Electronics Engineers (IEEE) 802.11 medium access control (MAC) that compensates for any diminished growth of TCP's sending rate because of the inclusion of non‐congestion delay component in RTT, if any. The proposed scheme has two refinements. The first refinement is at the MAC layer that notifies the additional propagation delay on account of link retransmission of a TCP packet. The second refinement is at the TCP layer in which the sender adapts the sending rate by relating the aforementioned additional propagation delay to the RTT estimation. To examine the benefits, the proposed scheme is evaluated after implementing it on top of representative TCP variants; Newreno and Westwood+ (TCPW). Simulation results showed that with the proposed scheme, network utilization by native TCP is improved by more than 35% in a dedicated WLAN environment, while the performance remained protected in a shared WLAN environment. Copyright © 2015 John Wiley & Sons, Ltd.

Asymmetric communication models for resource‐constrained hierarchical ethernet networks

SummaryCommunication time prediction is critical for parallel application performance tuning, especially for the rapidly growing field of data‐intensive applications. However, making such predictions accurately is non‐trivial when contention exists on different components in hierarchical networks. In this article, we derive an ‘asymmetric network property’ on transmission control protocol (TCP) layer for concurrent bidirectional communications in a commercial off‐the‐shelf (COTS) cluster and develop a communication model as the first effort to characterize the communication times on hierarchical Ethernet networks with contentions on both network interface card and backbone cable levels. We develop a micro‐benchmark for a set of simultaneous point‐to‐point message‐passing interface (MPI) operations on a parametrized network topology and use it to validate our model extensively and show that the model can be used to predict the communication times for simultaneous MPI operations (both point‐to‐point and collective communications) on resource‐constrained networks effectively. We show that if the asymmetric network property is excluded from the model, the communication time predictions will be significantly less accurate than those made by using the asymmetric network property. In addition, we validate the model on a cluster of Grid5000 infrastructure, which is a more loosely coupled platform. As such, we advocate the potential to integrate this model in performance analysis for data‐intensive parallel applications. Our observation of the performance degradation caused by the asymmetric network property suggests that some part of the software stack below TCP layer in COTS clusters needs targeted tuning, which has not yet attracted any attention in literature. Copyright © 2014 John Wiley & Sons, Ltd.

A Distributed MAC Layer Congestion Control Method to Achieve High Network Performance for EAST Experiments

Many applications would require fast data transfer in Wireless Local Area Networks (WLANs) nowadays. A representative example is the EAST (Experimental Advanced Superconducting Tokamak) project where physics researchers need to transport massive experiment data using the TCP (Transmission Control Protocol). However, the high contention level and the high error rate in wireless networks have a great impact on the TCP performance. To alleviate this problem, this paper proposes a MAC layer congestion control method to deal with wireless packet loss due to errors (as opposed to congestion). Our mechanism is implemented at the end wireless nodes based on the IEEE 802.11 DCF mechanism but without any modification to the TCP layer. We first propose the concept of the MAC layer congestion window in which the MAC layer will send all the packets in a window when it obtains access to the wireless channel (unlike the traditional DCF mechanism that just sends only one packet). Then we allow our congestion control mechanism to adjust its MAC congestion window based on the contention degree and the packet loss rate at the MAC layer. By performing wireless congestion control at the MAC layer, our mechanism can mitigate the effect of wireless packet loss on TCP, and therefore improve the TCP performance. The simulation and experiment results show that our mechanism can achieve better performance than the traditional MAC layer mechanisms in WLANs.

Channel Occupancy Time Based TCP Rate Control for Improving Fairness in IEEE 802.11 DCF

In the IEEE 802.11 distributed coordination function (DCF), the basic service set (BSS) suffers from two unfairness issues: 1) performance anomaly and 2) uplink/downlink unfairness. In this paper, to solve these issues, we propose a window control scheme in the Transmission Control Protocol (TCP) for the IEEE 802.11 DCF mode. The proposed scheme is called channel occupancy time based rate control for TCP (COTRC-TCP). COTRC-TCP controls the maximum window size based on the throughput estimated at the TCP layer so that each station can use the wireless channel for equal duration. The throughput estimation is based on the number of active stations and the channel occupancy period used by each station in the BSS, which are monitored at the Medium Access Control (MAC) layer. The proposed scheme forms a cross-layer approach that involves both MAC and transport layers. The performance of COTRC-TCP over multirate IEEE 802.11 DCF is evaluated and compared with that of previous works through extensive simulations. Simulation results show that COTRC-TCP exhibits fairness in terms of channel-occupancy time among the competing stations, which accordingly remedies the unfairness problems. The proposed scheme also improves the transmission efficiency.

Internet connection with UMTS

Mobile telecommunication new services are based on data networks specially Internet. These services include http, telnet, ftp, Simple Mail Transfer Protocol, etc. Besides, we recognize a mobile network as a multiuser network. Transmission Control Protocol (TCP)/Internet Protocol which is sensitive to link congestion in wireline data links is also used in wireless networks. In order to improve the system performance, the TCP layer uses flow control and congestion control. Besides, radio link control (RLC) and medium access control sublayers have been introduced to compensate the deficiency of TCP layer in wireless environment. RLC has an important role in quality of service enhancement of the Universal Mobile Telecommunications System (UMTS). In this paper, we review the protocol stack of UMTS Terrestrial Radio Access Network which is based on Third-Generation Partnership Project. Then, we evaluate its layer 2 error control mechanisms and verify TCP over automatic repeat request error control mechanism and finally quality of service improvement results from it in fading channels.

Design of coordinator to eliminate redundant local retransmission in wireless networks

Owing to limited bandwidth, high bit error rate, and bursty error in the wireless environment, the performance of the transmission control protocol (TCP) degrades greatly in wireless networks. Up to now, many researchers have contributed greatly to the wireless TCP field. However, in most of their works, the wireless TCP module usually works in the TCP layer and has no idea of the actual time of the packet transmission, which is determined by the Scheduler in the media access control (MAC) layer, and this will bring the inaccuracy to the local retransmission timeout and induce the redundant local retransmission. In this article, a coordinator is introduced into the base-station (BS), which can provide efficient cooperation between the TCP module and the scheduler module. On the bais of the performance analysis and simulation results, the proposed method is shown to eliminate redundant local retransmission, increase throughput, and improve TCP-level fairness in wireless networks. Moreover, this scheme is orthogonal to those existing wireless TCP schemes, thus it can give great compatibility to the current networks, and further enhance the performance of TCP under the condition that the performance improvement benefiting from the existing approaches will not be affected.

How to minimize the TCP effect in a UMTS‐HSDPA system?

AbstractThis paper focuses on the interaction between the transmission control protocol (TCP) layer and the radio interface in a 3G wireless system. An analytical model to evaluate the impact of TCP on the UMTS‐HSDPA capacity is presented. A method to minimize the effect of TCP on wireless networks using shared channels is also proposed. High speed downlink packet access (HSDPA) is an evolution of the UMTS standard over the air interface to achieve higher aggregate bit rates through the introduction of adaptive modulation and coding, hybrid automatic repeat request (ARQ), fast scheduling, fast cell selection, and multiple input multiple output (MIMO) (space time coding and blast) techniques. The proposed model is used to evaluate the effect of the TCP protocol on the bit rate of various data services (at 64 and 128 kbps). As expected, the bit rate per flow decreases strongly if the congestion frequency in the wired network increases. However, the overall capacity achieved by HSDPA is not as affected by the TCP layer. Using this result, a method to maintain the bit rate per TCP flow at a given value without loosing much cell capacity is proposed. The findings are supported by simulation results. Copyright © 2005 John Wiley & Sons, Ltd.

TCP performance over mobile ad hoc networks: a quantitative study

AbstractIn this paper, we study the performance of the transmission control protocol (TCP) over mobile ad‐hoc networks. We present a comprehensive set of simulation results and identify the key factors that impact TCP's performance over ad‐hoc networks. We use a variety of parameters including link failure detection latency, route computation latency, packet level route unavailability index, and flow level route unavailability index to capture the impact of mobility. We relate the impact of mobility on the different parameters to TCP's performance by studying the throughput, loss‐rate and retransmission timeout values at the TCP layer. We conclude from our results that existing approaches to improve TCP performance over mobile ad‐hoc networks have identified and hence focused only on a subset of the affecting factors. In the process, we identify a comprehensive set of factors influencing TCP performance. Finally, using the insights gained through the performance evaluations, we propose a framework called Atra consisting of three simple and easily implementable mechanisms at the MAC and routing layers to improve TCP's performance over ad‐hoc networks. We demonstrate that Atra improves on the throughput performance of a default protocol stack by 50%–100%. Copyright © 2004 John Wiley & Sons, Ltd.

Agent-based rate coordination between TCP and ABR congestion control algorithms

In this paper we study the extent of negative interactions between Transmission Control Protocol (TCP) and Asynchronous Transfer Mode (ATM) congestion control through the application of an approach based on coordination via explicit cooperation. To do so, we implement an agent that bridges the gap between the ATM layer and the TCP layer in the protocol stack at the sender end to coordinate the congestion control algorithms of the TCP transport protocol and the ATM cell-oriented switching architecture. The novel idea uses ATM rate-based flow control to adjust the credit-based window size of TCP via the implementation of the agent. The effects of running TCP over Available Bit Rate (ABR) are studied with the help of two simulation models (LAN and WAN). Firstly, we show that TCP window (CWND) and ABR Actual Cell Rate (ACR) are weakly correlated. Secondly, we derive an Agent-based algorithm to ensure that even when the ATM switch queues are indicating no congestion, it is the switch (and not the source) which should control the increment in the TCP source rates. The introduction of the agent at the edge of the network coordinates the TCP and ATM sending transmission and clearly demonstrates a strong correlation coefficient between CWND and ACR. The simulation results show that coordination at the edge of the network makes better use of available bandwidth and improves TCP's performance over ATM for a range of performance metrics such as Cell Loss Ratio, Packet Retransmission Ratio and Throughput.