The Experts below are selected from a list of 22389 Experts worldwide ranked by ideXlab platform

Oliver Hohlfeld - One of the best experts on this subject based on the ideXlab platform.

  • tcp s Initial Window deployment in the wild and its impact on performance
    IEEE Transactions on Network and Service Management, 2019
    Co-Authors: Jan Ruth, Ike Kunze, Oliver Hohlfeld
    Abstract:

    TCP congestion control and particularly its Initial congestion Window (IW) size is one long-debated topic that can influence Web performance. Its size is, however, assumed to be static by IETF recommendations—despite being network- and application-dependent—and only infrequently changed in its history. To understand if the standardization and research perspective still meets Internet reality, we study the IW configurations in IPv4 and of major content delivery networks (CDNs). We have been regularly inspecting IPv4 for HTTP and TLS servers to investigate their IW configuration and found a steady increase in IETF-recommended configurations. We additionally study how CDNs configure their IWs given their relevance for content distribution. To shed light on network-dependent CDN configurations, we use a globally distributed infrastructure of VPNs giving access to residential access links. We observe that most CDNs are well aware of the IW’s impact and find a high amount of customization that is beyond current Internet standards. We find various Initial Window configurations, most below 50 segments, yet, with exceptions of up to 100 segments—the tenfold of current standards. This paper highlights that Internet reality has drifted away from recommended and standardized practices. Driven by these findings, we investigate the effects of this new reality on the slow start of Cubic and BBR congestion controlled TCP flows. We find that TCP pacing is a key to enable increased IWs when competing against other traffic.

  • large scale scanning of tcp s Initial Window
    Internet Measurement Conference, 2017
    Co-Authors: Jan Ruth, Christian Bormann, Oliver Hohlfeld
    Abstract:

    Improving web performance is fueling the debate of sizing TCP's Initial congestion Window (IW), which is a critical performance parameter especially for short-lived flows. This debate yielded several RFC updates to recommended IW sizes, e.g., an increase to IW10 in 2010. The current adoption of IW recommendations is, however, unknown. In this paper, we therefore conduct large-scale measurements covering the entire IPv4 space inferring the IW distribution size by probing HTTP and HTTPS servers. We present an HTTP and TLS scanning method implemented in ZMap, enabling quick estimations of IW sizes at Internet scale. For the first time since the standardization and implementation of IW 10, we shed light on the rugged landscape of IW configurations on the Internet.

Dinil Mon Divakaran - One of the best experts on this subject based on the ideXlab platform.

  • characterizing the effects of tcp s Initial Window
    Conference on Computer Communications Workshops, 2017
    Co-Authors: Runa Barik, Dinil Mon Divakaran, Michael Welzl
    Abstract:

    Given the mice-elephant phenomenon (where 80% of flows in number contribute to only 20% of traffic in volume) of TCP traffic, TCP's slow-start algorithm plays an important role in today's Internet. Designed to slowly probe the network for available bandwidth, the current standard mandates TCP flows to start with an Initial Window (IW) size of at most ten segments. Given the speed of the today's networks, an IW of ten segments could be a good option; however, over years the IW value may need to be updated. This paper aids such future updates with a stochastic model that reveals the effects of IW on TCP traffic characteristics, queue length distribution, average packet loss probability, and response times of TCP flows. Our studies show that the optimal choice of IW for a flow depends on the bottleneck router's buffer size, number of active TCP connections, bottleneck router's link capacity, RTT, and flow size. We also observe that the IW value non-monotonously increases the number of RTTs required for flows to complete.

  • development and experimentation of tcp Initial Window function
    2014 International Conference and Workshop on the Network of the Future (NOF), 2014
    Co-Authors: Runa Barik, Dinil Mon Divakaran
    Abstract:

    In the light of the mice-elephant phenomenon of the Internet traffic, TCP congestion control algorithm shows unfairness against flows of small sizes (small flows). In this context, we find it motivating to study the influence of TCP's Initial Window (IW) size on the response times of small flows. In our previous works, we proposed a function that determines IW-size for each flow based on its size; through game-theoretic analysis as well as experiments on real testbed, we observed that the size-based IW function (in comparison to a single constant IW size) shows considerable improvement in the performance of small flows, while at the same time not affecting the performance of large flows. In this paper, we share the experience of using some important open source tools for developing, experimenting and evaluating the proposed IW function. We implement the size-based IW function in the Linux kernel, version 3.7.4; we use ipfw/Dummynet for emulating links, open source tool called parallel for executing the application in parallel for generating TCP traffic, wireshark (along with lua script) for extracting metrics for performance analysis. Finally we evaluate the performance of flows using the IW function.

  • configuring tcp s Initial Window
    2014
    Co-Authors: Dinil Mon Divakaran, Runa Barik, Rachel Huang, Jianjie You
    Abstract:

    This document discusses that TCP's Initial congestion Window is not a constant in different use cases. It proposes a flexible method to configure the Initial Window in order to keep up with the current network state.

  • evolution of tcp s Initial Window size
    Local Computer Networks, 2013
    Co-Authors: Runa Barik, Dinil Mon Divakaran
    Abstract:

    Recognizing the upper bound of TCP Initial Window (IW) size-four segments-too small, researchers have been proposing to increase this. In this context, we observed that given the mice-elephant phenomenon, small flows benefit more from larger IW-size than large flows. This work proposes a simple but effective function to set IW-size for each flow, and investigates a scenario where the decentralized nature of Internet may enforce users to strategically choose right value for some parameter V in function, for improving performance of flows. We develop an evolutionary non-cooperative game-theoretic model to evaluate equilibria points and evolutionary stable strategy that are reached by users. Our game-theoretic results reveal that, there exists an optimal value for V for which small flows achieve better performance. Further our experiments on a testbed confirm that the performance attained by small flows using the proposed function is considerably improved, while not affecting the performance of large flows.

  • tcp Initial Window a study
    Wired Wireless Internet Communications, 2012
    Co-Authors: Runa Barik, Dinil Mon Divakaran
    Abstract:

    The research community has for sometime argued the need to increase the size of TCP Initial-Window (IW). While it is probably high time that IW-size is increased, we note that a comprehensive study on this front is missing. In this paper, we attempt to build that gap, analyzing the affects increasing IW on various important parameters correlated to the performance of flows. In particular, given the mice-elephant phenomenon, we focus on how the response times of small TCP flows are affected with increasing IW. Our study reveals that, it is difficult to set one single value for IW that improves various parameters such as number of time-outs, retransmission rate, number of spurious time-outs, completion times of flows, etc. Instead, we propose to use a simple function to set the value of IW of a flow depending on the flow-size. Through simulations, we show that such a function performs better.

Jan Ruth - One of the best experts on this subject based on the ideXlab platform.

  • tcp s Initial Window deployment in the wild and its impact on performance
    IEEE Transactions on Network and Service Management, 2019
    Co-Authors: Jan Ruth, Ike Kunze, Oliver Hohlfeld
    Abstract:

    TCP congestion control and particularly its Initial congestion Window (IW) size is one long-debated topic that can influence Web performance. Its size is, however, assumed to be static by IETF recommendations—despite being network- and application-dependent—and only infrequently changed in its history. To understand if the standardization and research perspective still meets Internet reality, we study the IW configurations in IPv4 and of major content delivery networks (CDNs). We have been regularly inspecting IPv4 for HTTP and TLS servers to investigate their IW configuration and found a steady increase in IETF-recommended configurations. We additionally study how CDNs configure their IWs given their relevance for content distribution. To shed light on network-dependent CDN configurations, we use a globally distributed infrastructure of VPNs giving access to residential access links. We observe that most CDNs are well aware of the IW’s impact and find a high amount of customization that is beyond current Internet standards. We find various Initial Window configurations, most below 50 segments, yet, with exceptions of up to 100 segments—the tenfold of current standards. This paper highlights that Internet reality has drifted away from recommended and standardized practices. Driven by these findings, we investigate the effects of this new reality on the slow start of Cubic and BBR congestion controlled TCP flows. We find that TCP pacing is a key to enable increased IWs when competing against other traffic.

  • large scale scanning of tcp s Initial Window
    Internet Measurement Conference, 2017
    Co-Authors: Jan Ruth, Christian Bormann, Oliver Hohlfeld
    Abstract:

    Improving web performance is fueling the debate of sizing TCP's Initial congestion Window (IW), which is a critical performance parameter especially for short-lived flows. This debate yielded several RFC updates to recommended IW sizes, e.g., an increase to IW10 in 2010. The current adoption of IW recommendations is, however, unknown. In this paper, we therefore conduct large-scale measurements covering the entire IPv4 space inferring the IW distribution size by probing HTTP and HTTPS servers. We present an HTTP and TLS scanning method implemented in ZMap, enabling quick estimations of IW sizes at Internet scale. For the first time since the standardization and implementation of IW 10, we shed light on the rugged landscape of IW configurations on the Internet.

Runa Barik - One of the best experts on this subject based on the ideXlab platform.

  • characterizing the effects of tcp s Initial Window
    Conference on Computer Communications Workshops, 2017
    Co-Authors: Runa Barik, Dinil Mon Divakaran, Michael Welzl
    Abstract:

    Given the mice-elephant phenomenon (where 80% of flows in number contribute to only 20% of traffic in volume) of TCP traffic, TCP's slow-start algorithm plays an important role in today's Internet. Designed to slowly probe the network for available bandwidth, the current standard mandates TCP flows to start with an Initial Window (IW) size of at most ten segments. Given the speed of the today's networks, an IW of ten segments could be a good option; however, over years the IW value may need to be updated. This paper aids such future updates with a stochastic model that reveals the effects of IW on TCP traffic characteristics, queue length distribution, average packet loss probability, and response times of TCP flows. Our studies show that the optimal choice of IW for a flow depends on the bottleneck router's buffer size, number of active TCP connections, bottleneck router's link capacity, RTT, and flow size. We also observe that the IW value non-monotonously increases the number of RTTs required for flows to complete.

  • development and experimentation of tcp Initial Window function
    2014 International Conference and Workshop on the Network of the Future (NOF), 2014
    Co-Authors: Runa Barik, Dinil Mon Divakaran
    Abstract:

    In the light of the mice-elephant phenomenon of the Internet traffic, TCP congestion control algorithm shows unfairness against flows of small sizes (small flows). In this context, we find it motivating to study the influence of TCP's Initial Window (IW) size on the response times of small flows. In our previous works, we proposed a function that determines IW-size for each flow based on its size; through game-theoretic analysis as well as experiments on real testbed, we observed that the size-based IW function (in comparison to a single constant IW size) shows considerable improvement in the performance of small flows, while at the same time not affecting the performance of large flows. In this paper, we share the experience of using some important open source tools for developing, experimenting and evaluating the proposed IW function. We implement the size-based IW function in the Linux kernel, version 3.7.4; we use ipfw/Dummynet for emulating links, open source tool called parallel for executing the application in parallel for generating TCP traffic, wireshark (along with lua script) for extracting metrics for performance analysis. Finally we evaluate the performance of flows using the IW function.

  • configuring tcp s Initial Window
    2014
    Co-Authors: Dinil Mon Divakaran, Runa Barik, Rachel Huang, Jianjie You
    Abstract:

    This document discusses that TCP's Initial congestion Window is not a constant in different use cases. It proposes a flexible method to configure the Initial Window in order to keep up with the current network state.

  • evolution of tcp s Initial Window size
    Local Computer Networks, 2013
    Co-Authors: Runa Barik, Dinil Mon Divakaran
    Abstract:

    Recognizing the upper bound of TCP Initial Window (IW) size-four segments-too small, researchers have been proposing to increase this. In this context, we observed that given the mice-elephant phenomenon, small flows benefit more from larger IW-size than large flows. This work proposes a simple but effective function to set IW-size for each flow, and investigates a scenario where the decentralized nature of Internet may enforce users to strategically choose right value for some parameter V in function, for improving performance of flows. We develop an evolutionary non-cooperative game-theoretic model to evaluate equilibria points and evolutionary stable strategy that are reached by users. Our game-theoretic results reveal that, there exists an optimal value for V for which small flows achieve better performance. Further our experiments on a testbed confirm that the performance attained by small flows using the proposed function is considerably improved, while not affecting the performance of large flows.

  • tcp Initial Window a study
    Wired Wireless Internet Communications, 2012
    Co-Authors: Runa Barik, Dinil Mon Divakaran
    Abstract:

    The research community has for sometime argued the need to increase the size of TCP Initial-Window (IW). While it is probably high time that IW-size is increased, we note that a comprehensive study on this front is missing. In this paper, we attempt to build that gap, analyzing the affects increasing IW on various important parameters correlated to the performance of flows. In particular, given the mice-elephant phenomenon, we focus on how the response times of small TCP flows are affected with increasing IW. Our study reveals that, it is difficult to set one single value for IW that improves various parameters such as number of time-outs, retransmission rate, number of spurious time-outs, completion times of flows, etc. Instead, we propose to use a simple function to set the value of IW of a flow depending on the flow-size. Through simulations, we show that such a function performs better.

Huang Guo-ce - One of the best experts on this subject based on the ideXlab platform.

  • TCP Slow Start Algorithm Based on RTT Fairness
    Computer Engineering, 2009
    Co-Authors: Wang Jian-feng, Huang Guo-ce
    Abstract:

    Thi paper analyzes the problems in standard TCP slow start algorithm when it is applied to the network environment including GEO satellite links.To solve these problems,a new improved TCP slow start algorithm based on RTT fairness is proposed,termed RFB-SS.RFB-SS algorithm uses the larger Initial Window mechanism.And in the early slow start phase,the congestion Window remains exponential growth,in the late phase,by using Window control growth factor,the congestion Window of larger RTT increases faster,otherwise increases slower.Performance analysis and simulation results show that RFB-SS algorithm slows down the congestion Window growth rate,and weakens the TCP flow of smaller RTT in the aggressive bandwidth competition in the late slow start phase.To a certain extent,RFB-SS algorithm obtains a fair sharing of available bandwidth among different RTT flows.