P. Barford and M. E. Crovella, "Critical Path Analysis of TCP Transactions," in Proceedings of the 2000.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....busiest servers are typically commercial, and thus have privacy and security concerns, making it difficult to gain access to them. Analyzing live servers is, unfortunately, rarely an available option for discovering problems in WWW server performance. The Wide Area Web Measurement (WAWM) project [6, 8] takes a related approach in that it places virtual test clients in the wide area network. The clients send synthetic requests generated by SURGE to a remote server. This guarantees the incorporation of realistic network characteristics, but using an actual wide area network makes it difficult to ....

Paul Barford and Mark Crovella. Critical path analysis of TCP transactions. In ACM SIGCOMM Symposium on Communications Architectures and Protocols, Stockhold, Sweden, August 2000.

....we say that VOD does not have the inherent hard latency requirements of purely interactive applications, and so TCP s packetretransmissions are not a significant problem for VOD. For purely interactive applications, we think it is important to characterize delays using the critical path approach[11, 2]. The question is how much of the retransmission delay e#ects mean and worst case critical paths for interactive applications. The critical path approach stresses the importance of interaction with other sources of delay. If congestion avoidance is essential to the best e#ort Internet, it may be ....

Paul Barford and Mark Crovella. Critical Path Analysis of TCP Transactions. In In Proceedings of the 2000 ACM SIGCOMM Conference, September 2000.

....the edges in the reverse direction up to the root. The nodes and edges traversed comprise the critical path for the lookup. In Figure 6, the dark arrows indicate the critical path for The idea of using critical path analysis for a portion of our work was inspired by work by Barford and Crovella [22]. They used critical path analysis to investigate various effects on the critical path profiles of TCP transactions. 1000 1500 2000 2500 3000 1.2 1.4 1.6 1.8 2.0 2.2 Total retries along critical paths Response Time of completed lookups (sec) Corr = 0.50 Fig. 7. Total retries along ....

Paul Barford and Mark Crovella, "Critical path analysis of TCP transactions," in Proceedings of ACM SIGCOMM, 2000, pp. 127-- 138.

....is defined to be the response time of the request. In this paper we focus on what we can do to improve the delay at the server. Research has shown that in situations where the server is receiving a high rate of requests, the delays at the server make up a significant portion of the response time [8], 7] 28] More This research is funded by Cisco Systems via a grant from the Pittsburgh Digital Greenhouse 00 1 and by NSF ITR 99 167 ANI0081396. Equipment was also provided by the Parallel Data Lab. specifically, 8] 7] find that even if the network load is high, the delays at a busy web ....

....the delays at the server make up a significant portion of the response time [8] 7] 28] More This research is funded by Cisco Systems via a grant from the Pittsburgh Digital Greenhouse 00 1 and by NSF ITR 99 167 ANI0081396. Equipment was also provided by the Parallel Data Lab. specifically, [8], 7] find that even if the network load is high, the delays at a busy web server can be responsible for more than 80 of the overall response time of a small file, and for 50 of the overall response time of a medium size file. Measurements [27] suggest that the request stream at most web ....

[Article contains additional citation context not shown here]

Paul Barford and Mark Crovella. Critical path analysis of tcp transactions. In SIGCOMM, 2000.

.... TCP packet losses have also been proposed [2] 3] 5] 9] 13] 17] 30] We believe that our context aware TCP IP approach complements many of these prior approaches, including connection state caching, rate based pacing, SACK TCP [13] Ensemble TCP [12] and RED [16] Barford and Crovella [8] discuss the critical path analysis of TCP connections, in an attempt to pinpoint the causes of the delays incurred during Web document transfers, However, this analysis is primarily from a network trafc analysis viewpoint, rather than a TCP control algorithm viewpoint. Our work builds upon ....

P. Barford and M. Crovella, "Critical Path Analysis of TCP Transactions ", Proceedings of ACM SIGCOMM, Stockholm, Sweden, pp. 127138, September 2000.

....an agreement among multiple organizations. Another motivation for focusing on Web system architecture is due to the growing complexity of Web applications and services. Web performance perceived by end users is increasingly dominated by server delays, especially when contacting busy servers [15]. Recent measures suggest that the Web servers contribute for about 40 of the delay in a Web transaction [58] and it is likely that this percentage will increase in the near future. As a consequence of the changes transforming the Web from a simple communication and browsing infrastructure to a ....

P. Barford and M. E. Crovella. Critical path analysis of TCP transactions. In Proc. of ACM $igcomm 2000.

....are with the Department of Electrical Engineering, Stanford University, Stanford CA 94305. Email: noureddine, tobagi stanford.edu teractivity [14] or by using content replication and caching. In contrast, network delays, which form a significant part of total delay for Web transfers [4] [5], 24] 26] are usually outside the control of the provider or any other single organization, and are therefore not as easily reduced. In this paper, our focus is on network delays, and we assume that server performance has been properly addressed and server delays are therefore negligible. For ....

....at reduced rate. Finally, the exponential retransmit backoff rule typically doubles the retransmit timer value when a retransmitted packet is lost [28] This means that the loss of successive retransmissions results in very large delays. Similar observations were made in a measurement study [5], where the causes of transaction delays are profiled by tracing TCP packets exchanged between Web clients and servers. The study shows the network is a significant component of total delay for medium sized transfers (Web objects) and packet loss is the main cause of response time variability. ....

Barford P., Crovella M., Critical Path Analysis of TCP Transactions, in IEEE Transactions on Networking, Jun. 2001.

....instability, througput, client delay and server delay. Therefore, pinpointing the sources of the delay in the network application is not a easy job and the it usually requires at least two monitoring points, one is near the client application and the other is near the peer server side. Barford [3] recently proposed methods that aid in locating the root causes of delays in TCP transactions by passively collecting analyzing network tra#c traces at the end of points during TCP transactions. It enables the accurate assignment of delays to either the network, the client, or the server. However, ....

Paul Barford and Mark Crovella. Critical Path Analysis of TCP Transactions. In Proc. of ACM SIGCOMM, Sweden, August 2000.

....delays of sub second timescales, typically in the range of 150 to 200 milliseconds. This end to end delay requirement persists for the duration of these applications. Given the tight delay bounds, we think it is important to characterize various delay sources using the critical path approach[12, 2]. The question is how much the retransmission delay e#ects the mean and worst case critical paths for interactive applications. The critical path approach stresses the importance of interaction with other sources of delay. If congestion control is essential to the best e#ort Internet, it may be ....

Paul Barford and Mark Crovella. Critical Path Analysis of TCP Transactions. In In Proceedings of the

....is defined to be the response time of the request. In this paper we focus on what we can do to improve the delay at the server. Research has shown that in situations where the server is receiving a high rate of requests, the delays at the server make up a significant portion of the response time [8], 7] 28] More This research is funded by Cisco Systems via a grant from the Pittsburgh Digital Greenhouse 00 1 and by NSF ITR 99 167 ANI0081396. Equipment was also provided by the Parallel Data Lab. specifically, 8] 7] find that even if the network load is high, the delays at a busy web ....

....the delays at the server make up a significant portion of the response time [8] 7] 28] More This research is funded by Cisco Systems via a grant from the Pittsburgh Digital Greenhouse 00 1 and by NSF ITR 99 167 ANI0081396. Equipment was also provided by the Parallel Data Lab. specifically, [8], 7] find that even if the network load is high, the delays at a busy web server can be responsible for more than 80 of the overall response time of a small file, and for 50 of the overall response time of a medium size file. Measurements [27] suggest that the request stream at most web ....

[Article contains additional citation context not shown here]

Paul Barford and Mark Crovella. Critical path analysis of tcp transactions. In SIGCOMM, 2000.

....in a parallel system is critical path analysis. By discovering the chain of dependent events that determined the overall execution time, critical path analysis has been used successfully for identifying performance bottlenecks in large scale parallel systems, such as communication networks [3, 9]. Out of order superscalar processors are fine grain parallel systems: their instructions are fetched, re ordered, executed, and committed in parallel. We argue that the level of their parallelism and sophistication has grown enough to justify the use of critical path analysis of their ....

P. Barford and M. Crovella. Critical path analysis of TCP transactions. In Proceedings of ACM SIGCOMM

....of TCP, which we call TCP ERC, or TCP for erasureresilient content, requires no client modifications, as TCP clients never examine discrepancies between content of an original transmission and a retransmission. Moreover, since our changes do not impact the timing semantics nor the critical path [6] of a TCP transfer, there is no negative performance impact. Delving into the details of TCP ERC, all of the flow control and congestion control mechanisms of TCP are retained in full. Conceptually, TCP ERC differs from regular TCP in only one respect. In a situation in which TCP would retransmit ....

P. Barford and M. Crovella. Critical path analysis of TCP transactions. In ACM SIGCOMM, Stockholm, Sweden, August 2000.

....of TCP, which we call TCP ERC, or TCP for erasure resilient content, requires no client modifications, as TCP clients never examine discrepancies between content of an original transmission and a retransmission. Moreover, since our changes do not impact the timing semantics nor the critical path [6] of a TCP transfer, there is no negative performance impact. Delving into the details of TCP ERC, all of the flow control and congestion control mechanisms of TCP are retained in full. Conceptually, TCP ERC differs from regular TCP in only one respect. In a situation in which TCP would retransmit ....

P. Barford and M. Crovella. Critical path analysis of TCP transactions. In ACM SIGCOMM, Stockholm, Sweden, August 2000.

....areas in addition to the typical difficulties associated with wide area measurement based study [10] The first was the task of breaking down data transfer delays into subcomponents. We addressed this by developing a robust, kernel level implementation of critical path analysis of TCP transfers [11]. Our kernel level implementation has two important benefits: it enables the calculation of subcomponents of data transfer delays in real time and expands the number of sub components of delays from the six described in [11] to nine. The details of the new subcomponents are described in Section ....

.... kernel level implementation of critical path analysis of TCP transfers [11] Our kernel level implementation has two important benefits: it enables the calculation of subcomponents of data transfer delays in real time and expands the number of sub components of delays from the six described in [11] to nine. The details of the new subcomponents are described in Section III. The combination of path property measurements and detailed data transfer delay measurements over 90 paths for 45 days led to a very large and highly dimensional data set. Our second challenge was organizing and reducing ....

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P. Barford and M. Crovella, "Critical path analysis of TCP transactions, " in Proceedings of ACM SIGCOMM '00, Stockholm, Sweden, September 2000.

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P. Barford and M. E. Crovella, "Critical Path Analysis of TCP Transactions," in Proceedings of the 2000.

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P. Barford and M. Crovella. Critical path analysis of TCP transactions. IEEE/ACM Transactions on Networking, 9(3), June 2001.

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Paul Barford and Mark Crovella. Critical Path Analysis of TCP Transactions. In SIGCOMM, pages 127--138, 2000. (pp 41, 42, 116, 117, 118, 134)

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P. Barford and M. Crovella, "Critical path analysis of TCP transactions," IEEE/ACM Transactions on Networking, vol. 9, pp. 238-48, 2001.

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P Barford, M. Crovella, "Critical path analysis of TCP transactions", em IEEE/ACM Transactions on Networking, vol. 9, no. 3, Jun 2001, pp. 238248

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P. Barford and M. Crovella. Critical path analysis of TCP transactions. IEEE/ACM Transactions on Networking, 9(3), June 2001.

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P. Barford and M. E. Crovella, Critical path analysis of TCP transactions, Proc. 2000.

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P. Barford and M. Crovella. Critical path analysis of TCP transactions. In Proceedings of ACM SIGCOMM, January 2000.

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P. Barford and M. Crovella. Critical path analysis of TCP transactions. IEEE/ACM Transactions on Networking, 9(3), June 2001.

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Paul Barford and Mark Crovella. Critical path analysis of tcp transactions. In SIGCOMM, 2000.

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Barford P., Crovella M., Critical Path Analysis of TCP Transactions, in IEEE Transactions on Networking, Volume 9, Number 3, June 2001.

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