Pub Date : 2018-09-01DOI: 10.1109/ITC30.2018.00010
Esa Hyytiä, Rhonda Righter
Dispatching systems, where jobs are routed to servers immediately upon arrival, appear frequently in parallel computing systems. With a dynamic dispatching policy, the system is generally analytically intractable and performance evaluation is carried out by means of Monte Carlo simulations. A typical performance metric is the mean response time which is often easy to estimate. In contrast, we consider systems where events generating costs are extremely rare. In our reference system, jobs have deadlines for waiting time. When deadlines are loose when compared to the system's load, novel rare event simulation techniques must be applied. We consider both conditioning and importance sampling to this end. The proposed techniques are illustrated in numerical examples, where we discover interesting performance relationships among the classical dispatching policies; Random split (RND), Round-robin (RR), Join-the-shortest-queue (JSQ) and Least-work-left (LWL).
{"title":"Evaluating Rare Events in Mission Critical Dispatching Systems","authors":"Esa Hyytiä, Rhonda Righter","doi":"10.1109/ITC30.2018.00010","DOIUrl":"https://doi.org/10.1109/ITC30.2018.00010","url":null,"abstract":"Dispatching systems, where jobs are routed to servers immediately upon arrival, appear frequently in parallel computing systems. With a dynamic dispatching policy, the system is generally analytically intractable and performance evaluation is carried out by means of Monte Carlo simulations. A typical performance metric is the mean response time which is often easy to estimate. In contrast, we consider systems where events generating costs are extremely rare. In our reference system, jobs have deadlines for waiting time. When deadlines are loose when compared to the system's load, novel rare event simulation techniques must be applied. We consider both conditioning and importance sampling to this end. The proposed techniques are illustrated in numerical examples, where we discover interesting performance relationships among the classical dispatching policies; Random split (RND), Round-robin (RR), Join-the-shortest-queue (JSQ) and Least-work-left (LWL).","PeriodicalId":159861,"journal":{"name":"2018 30th International Teletraffic Congress (ITC 30)","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121370386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-09-01DOI: 10.1109/ITC30.2018.00042
Jan Willem Kleinrouweler, Britta Meixner, J. Bosman, H. V. D. Berg, R. Mei, Pablo César
Frequent variations in throughput make mobile networks a challenging environment for video streaming. Current video players deal with those variations by matching video quality to network throughput. However, this adaptation strategy results in frequent changes of video resolution and bitrate, which negatively impacts the users' streaming experience. Alternatively, keeping the video quality constant would improve the experience, but puts additional demand on the network. Downloading high quality content when channel quality is low requires additional resources, because data transfer efficiency is linked to channel quality. In this paper, we present a predictive Channel Quality based Buffering Strategy (CQBS) that lets the video buffer grow when channel quality is good, and relies on this buffer when channel quality decreases. Our strategy is the outcome of a Markov Decision Process. The underlying Markov chain is conditioned on 377 real-world LTE channel quality traces that we have collected using an Android mobile application. With our strategy, mobile network providers can deliver constant quality video streams, using less network resources.
{"title":"Improving Mobile Video Quality Through Predictive Channel Quality Based Buffering","authors":"Jan Willem Kleinrouweler, Britta Meixner, J. Bosman, H. V. D. Berg, R. Mei, Pablo César","doi":"10.1109/ITC30.2018.00042","DOIUrl":"https://doi.org/10.1109/ITC30.2018.00042","url":null,"abstract":"Frequent variations in throughput make mobile networks a challenging environment for video streaming. Current video players deal with those variations by matching video quality to network throughput. However, this adaptation strategy results in frequent changes of video resolution and bitrate, which negatively impacts the users' streaming experience. Alternatively, keeping the video quality constant would improve the experience, but puts additional demand on the network. Downloading high quality content when channel quality is low requires additional resources, because data transfer efficiency is linked to channel quality. In this paper, we present a predictive Channel Quality based Buffering Strategy (CQBS) that lets the video buffer grow when channel quality is good, and relies on this buffer when channel quality decreases. Our strategy is the outcome of a Markov Decision Process. The underlying Markov chain is conditioned on 377 real-world LTE channel quality traces that we have collected using an Android mobile application. With our strategy, mobile network providers can deliver constant quality video streams, using less network resources.","PeriodicalId":159861,"journal":{"name":"2018 30th International Teletraffic Congress (ITC 30)","volume":"01 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129647135","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-06-26DOI: 10.1109/ITC30.2018.00043
N. Pappas, Ioannis Dimitriou, Zhengqing Chen
In this work, we consider a random access IoT wireless network assisted by two aggregators. The nodes and the aggregators are transmitting in a random access manner under slotted time, the aggregators use network-level cooperation. We assume that all the nodes are sharing the same wireless channel to transmit their data to a common destination. The aggregators with out-of-band full duplex capability, are equipped with queues to store data packets that are transmitted by the network nodes and relaying them to the destination node. We characterize the throughput performance of the IoT network. In addition, we obtain the stability conditions for the queues at the aggregators and the average delay of the packets.
{"title":"Network-Level Cooperation in Random Access IoT Networks with Aggregators","authors":"N. Pappas, Ioannis Dimitriou, Zhengqing Chen","doi":"10.1109/ITC30.2018.00043","DOIUrl":"https://doi.org/10.1109/ITC30.2018.00043","url":null,"abstract":"In this work, we consider a random access IoT wireless network assisted by two aggregators. The nodes and the aggregators are transmitting in a random access manner under slotted time, the aggregators use network-level cooperation. We assume that all the nodes are sharing the same wireless channel to transmit their data to a common destination. The aggregators with out-of-band full duplex capability, are equipped with queues to store data packets that are transmitted by the network nodes and relaying them to the destination node. We characterize the throughput performance of the IoT network. In addition, we obtain the stability conditions for the queues at the aggregators and the average delay of the packets.","PeriodicalId":159861,"journal":{"name":"2018 30th International Teletraffic Congress (ITC 30)","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133382344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-04-27DOI: 10.1109/ITC30.2018.10053
Ehsan Mohammadpour, Eleni Stai, Maaz M. Mohiuddin, J. Boudec
We compute bounds on end-to-end worst-case latency and on nodal backlog size for a per-class deterministic network that implements Credit Based Shaper (CBS) and Asynchronous Traffic Shaping (ATS), as proposed by the Time-Sensitive Networking (TSN) standardization group. ATS is an implementation of the Interleaved Regulator, which reshapes traffic in the network before admitting it into a CBS buffer, thus avoiding burstiness cascades. Due to the interleaved regulator, traffic is reshaped at every switch, which allows for the computation of explicit delay and backlog bounds. Furthermore, we obtain a novel, tight per-flow bound for the response time of CBS, when the input is regulated, which is smaller than existing network calculus bounds. We also compute a per-flow bound on the response time of the interleaved regulator. Based on all the above results, we compute bounds on the per-class backlogs. Then, we use the newly computed delay bounds along with recent results on interleaved regulators from literature to derive tight end-to-end latency bounds and show that these are less than the sums of per-switch delay bounds.
{"title":"Latency and Backlog Bounds in Time-Sensitive Networking with Credit Based Shapers and Asynchronous Traffic Shaping","authors":"Ehsan Mohammadpour, Eleni Stai, Maaz M. Mohiuddin, J. Boudec","doi":"10.1109/ITC30.2018.10053","DOIUrl":"https://doi.org/10.1109/ITC30.2018.10053","url":null,"abstract":"We compute bounds on end-to-end worst-case latency and on nodal backlog size for a per-class deterministic network that implements Credit Based Shaper (CBS) and Asynchronous Traffic Shaping (ATS), as proposed by the Time-Sensitive Networking (TSN) standardization group. ATS is an implementation of the Interleaved Regulator, which reshapes traffic in the network before admitting it into a CBS buffer, thus avoiding burstiness cascades. Due to the interleaved regulator, traffic is reshaped at every switch, which allows for the computation of explicit delay and backlog bounds. Furthermore, we obtain a novel, tight per-flow bound for the response time of CBS, when the input is regulated, which is smaller than existing network calculus bounds. We also compute a per-flow bound on the response time of the interleaved regulator. Based on all the above results, we compute bounds on the per-class backlogs. Then, we use the newly computed delay bounds along with recent results on interleaved regulators from literature to derive tight end-to-end latency bounds and show that these are less than the sums of per-switch delay bounds.","PeriodicalId":159861,"journal":{"name":"2018 30th International Teletraffic Congress (ITC 30)","volume":"19 3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123263788","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-04-21DOI: 10.1109/ITC30.2018.10058
A. Burchard, J. Liebeherr
Generalized Processor Sharing (GPS), which provides the theoretical underpinnings for fair packet scheduling algorithms, has been studied extensively. However, a tight formulation of the available service to a flow only exists for traffic that is regulated by affine arrival envelopes and a constant-rate link. In this paper, we show that the universal service curve by Parekh and Gallager can be extended to concave arrival envelopes and links with time-variable capacity. We also dispense with the previously existing assumption of a stable system.
{"title":"A General Per-Flow Service Curve for GPS","authors":"A. Burchard, J. Liebeherr","doi":"10.1109/ITC30.2018.10058","DOIUrl":"https://doi.org/10.1109/ITC30.2018.10058","url":null,"abstract":"Generalized Processor Sharing (GPS), which provides the theoretical underpinnings for fair packet scheduling algorithms, has been studied extensively. However, a tight formulation of the available service to a flow only exists for traffic that is regulated by affine arrival envelopes and a constant-rate link. In this paper, we show that the universal service curve by Parekh and Gallager can be extended to concave arrival envelopes and links with time-variable capacity. We also dispense with the previously existing assumption of a stable system.","PeriodicalId":159861,"journal":{"name":"2018 30th International Teletraffic Congress (ITC 30)","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129811691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-04-21DOI: 10.1109/ITC30.2018.10057
J. Liebeherr
We show that a fluid-flow interpretation of Service Curve Earliest Deadline First (SCED) scheduling simplifies deadline derivations for this scheduler. By exploiting the recently reported isomorphism between min-plus and max-plus network calculus and expressing deadlines in a max-plus algebra, deadline computations no longer require explicit pseudo-inverse computations. SCED deadlines are provided for latency-rate as well as a class of piecewise linear service curves.
{"title":"A Fluid-Flow Interpretation of SCED Scheduling","authors":"J. Liebeherr","doi":"10.1109/ITC30.2018.10057","DOIUrl":"https://doi.org/10.1109/ITC30.2018.10057","url":null,"abstract":"We show that a fluid-flow interpretation of Service Curve Earliest Deadline First (SCED) scheduling simplifies deadline derivations for this scheduler. By exploiting the recently reported isomorphism between min-plus and max-plus network calculus and expressing deadlines in a max-plus algebra, deadline computations no longer require explicit pseudo-inverse computations. SCED deadlines are provided for latency-rate as well as a class of piecewise linear service curves.","PeriodicalId":159861,"journal":{"name":"2018 30th International Teletraffic Congress (ITC 30)","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122448026","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-03-22DOI: 10.1109/ITC30.2018.00031
Zhiyuan Jiang, B. Krishnamachari, Sheng Zhou, Z. Niu
In an Internet-of-Things system where status data are collected from sensors and actuators for time-critical applications, the freshness of data is vital and can be quantified by the recently proposed age-of-information (AoI) metric. In this paper, we first consider a general scenario where multiple terminals share a common channel to transmit or receive randomly generated status packets. The optimal scheduling problem to minimize AoI is formulated as a restless multi-armed bandit problem. To solve the problem efficiently, we derive the Whittle's index in closed-form and establish the indexability thereof. Compared with existing work, we extend the index policy for AoI optimization to incorporate stochastic packet arrivals and optimal packet management (buffering the latest packet). Inspired by the index policy which has near-optimal performance but is centralized by nature, a decentralized status update scheme, i.e., the index-prioritized random access policy (IPRA), is further proposed, achieving universally near-optimal AoI performance and outperforming state-of-the-arts in the literature.
在物联网系统中，从传感器和执行器收集状态数据用于时间关键型应用，数据的新鲜度至关重要，可以通过最近提出的信息年龄(AoI)度量来量化。在本文中，我们首先考虑一个通用场景，其中多个终端共享一个公共通道来发送或接收随机生成的状态数据包。将AoI最小的最优调度问题表述为一个不宁多臂强盗问题。为了有效地解决这一问题，我们导出了封闭形式的惠特尔指数，并建立了其可索引性。与已有的工作相比，我们扩展了AoI优化的索引策略，将随机数据包到达和最优数据包管理(缓冲最新数据包)结合起来。受具有接近最优性能但本质上是中心化的索引策略的启发，进一步提出了一种分散的状态更新方案，即索引优先随机访问策略(index- priority random access policy, IPRA)，实现了普遍接近最优的AoI性能，优于文献中最先进的性能。
{"title":"Can Decentralized Status Update Achieve Universally Near-Optimal Age-of-Information in Wireless Multiaccess Channels?","authors":"Zhiyuan Jiang, B. Krishnamachari, Sheng Zhou, Z. Niu","doi":"10.1109/ITC30.2018.00031","DOIUrl":"https://doi.org/10.1109/ITC30.2018.00031","url":null,"abstract":"In an Internet-of-Things system where status data are collected from sensors and actuators for time-critical applications, the freshness of data is vital and can be quantified by the recently proposed age-of-information (AoI) metric. In this paper, we first consider a general scenario where multiple terminals share a common channel to transmit or receive randomly generated status packets. The optimal scheduling problem to minimize AoI is formulated as a restless multi-armed bandit problem. To solve the problem efficiently, we derive the Whittle's index in closed-form and establish the indexability thereof. Compared with existing work, we extend the index policy for AoI optimization to incorporate stochastic packet arrivals and optimal packet management (buffering the latest packet). Inspired by the index policy which has near-optimal performance but is centralized by nature, a decentralized status update scheme, i.e., the index-prioritized random access policy (IPRA), is further proposed, achieving universally near-optimal AoI performance and outperforming state-of-the-arts in the literature.","PeriodicalId":159861,"journal":{"name":"2018 30th International Teletraffic Congress (ITC 30)","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132102560","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-01-07DOI: 10.1109/ITC30.2018.00036
Ramakrishnan Durairajan, Sathiya Kumaran Mani, P. Barford, R. Nowak, J. Sommers
One-way delay (OWD) between end hosts has important implications for Internet applications, protocols, and measurement-based analyses. We describe a new approach for identifying OWDs via passive measurement of Network Time Protocol (NTP) traffic. NTP traffic offers the opportunity to measure OWDs accurately and continuously from hosts throughout the Internet. Based on detailed examination of NTP implementations and in-situ behavior, we develop an analysis tool that we call TimeWeaver, which enables assessment of precision and accuracy of OWD measurements from NTP. We apply TimeWeaver to a ~1TB corpus of NTP traffic collected from 19 servers located in the US and report on the characteristics of hosts and their associated OWDs, which we classify in a precision/accuracy hierarchy. To demonstrate the utility of these measurements, we apply iterative hard-threshold singular value decomposition to estimate the missing OWDs between arbitrary hosts from the highest tier in the hierarchy. We show that this approach results in highly accurate estimates of missing OWDs, with average error rates on the order of less than 2%.
{"title":"TimeWeaver: Opportunistic One Way Delay Measurement Via NTP","authors":"Ramakrishnan Durairajan, Sathiya Kumaran Mani, P. Barford, R. Nowak, J. Sommers","doi":"10.1109/ITC30.2018.00036","DOIUrl":"https://doi.org/10.1109/ITC30.2018.00036","url":null,"abstract":"One-way delay (OWD) between end hosts has important implications for Internet applications, protocols, and measurement-based analyses. We describe a new approach for identifying OWDs via passive measurement of Network Time Protocol (NTP) traffic. NTP traffic offers the opportunity to measure OWDs accurately and continuously from hosts throughout the Internet. Based on detailed examination of NTP implementations and in-situ behavior, we develop an analysis tool that we call TimeWeaver, which enables assessment of precision and accuracy of OWD measurements from NTP. We apply TimeWeaver to a ~1TB corpus of NTP traffic collected from 19 servers located in the US and report on the characteristics of hosts and their associated OWDs, which we classify in a precision/accuracy hierarchy. To demonstrate the utility of these measurements, we apply iterative hard-threshold singular value decomposition to estimate the missing OWDs between arbitrary hosts from the highest tier in the hierarchy. We show that this approach results in highly accurate estimates of missing OWDs, with average error rates on the order of less than 2%.","PeriodicalId":159861,"journal":{"name":"2018 30th International Teletraffic Congress (ITC 30)","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114337710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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