John Heidemann. Performance interactions between P-HTTP and TCP implementations. Computer Communications Review, 27(2), April 1997.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....is built on top of TCP, which provides reliable delivery between communication peers. Though TCP has been successful in delivering web traffic in many environments, previous research work have revealed the following intrinsic problems with TCP that hinders further performance improvement [6]. TCP is a connection oriented protocol that ensures communication reliability. The participants first setup a communication channel by a three way handshaking process, which is lengthy for high delay environment and short connections like HTML page delivery. Web servers could redirect the ....

....tag blocking thus is still subject to HOL blocking. Whereas the context aware scheme is not obstructed by tags and thus exhibit even better performance. 4 Related Works Research on HTTP transportation protocols mainly focused on how to adapt TCP to transfer short HTTP files. Persistent HTTP[6, 16] (P HTTP) has been proposed to reduce the setup cost in TCP. TCP fast start [16] is a technique that utilizes prior connections information to avoid slow start of TCP thus speed up short file downloading. Performance of various HTTP transportation protocols was analyzed in [7] The authors ....

J. Heidemann, "Performance Interactions Between PHTTP and TCP Implementations," ACM Computer Communication Review, vol. 27(2), pp. 65--73, April 1997.

....link) This observation was reinforced by Heidemann [6] who showed, as a result of analysis of traffic models, that lowest link bandwidths in excess of 200 Kbps are required in order to realize a subjective improvement in performance seen by the user. He reported validatation of the models used in [7] by comparison with traces of real traffic. The paper also identifies some areas of TCP HTTP interaction where persistence introduces delay. Identification of the various elements contributing to the download time of Web objects has been the subject of much research. It is, however, the download ....

J. Heidemann, "Performance interactions between P-HTTP and TCP implementations," ACM Computer Communication Review, vol. 27(2), pp. 65--73, April 1997. [Online]. Available: citeseer.nj.nec.com/heidemann97performance.html

....is built on top of TCP, which provides reliable delivery between communication peers. Though TCP has been successful in delivering web traffic in many environments, previous research work have revealed the following intrinsic problems with TCP that hinders further performance improvement [8], 18] TCP is a connection oriented protocol that ensures communication reliability. The participants first setup a communication channel by a three way handshaking process, which is lengthy for high delay environment and short connections like HTML page delivery. Web servers could redirect the ....

....time with various tag distances under loss rate 10 1000 10000 0 20 40 60 80 100 120 140 160 time (ms) Request UDP CATP Fig. 17. Internet test VII. RELATED WORKS Research on HTTP transportation protocols mainly focused on how to adapt TCP to transfer short HTTP files. Persistent HTTP[8], 18] 19] P HTTP) has been proposed to reduce the setup cost in TCP. TCP fast start [19] is a technique that utilizes prior connections information to avoid slow start of TCP thus speed up short file downloading. Performance of various HTTP transportation protocols was analyzed in [9] The ....

J. Heidemann, "Performance Interactions Between P-HTTP and TCP Implementations," ACM Computer Communication Review, vol. 27(2), pp. 65--73, April 1997.

....the transfer time of small les (which would take a few msec) is disproportionately increased given the delay in hundreds of msec su ered by the rst ACK. In addition, in request response applications, such as HTTP, it can delay transactions which generate segments that are smaller than 1 MSS [88]. Furthermore, as discussed in the following section, it can badly interact with Nagle s algorithm to signi cantly limit the transaction rate between two hosts. Finally, the delayed ACK scheme also a ects the various congestion mechanisms, as discussed in Section 7. For these reasons, some Unix ....

....is typically set to 1 MSS at the start of a connection. However, a well known bug in some BSD derived implementations increases the window when the ACK for the SYN ACK segment is received. Therefore, the endpoint which performs a passive open (i.e. server) e ectively starts with a 2 MSS window [88]. Obviously, this behavior has been accommodated in the standard. Note that starting with 2 segments allows connections to avoid waiting for a delayed ACK to expire, which would happen if only 1 MSS segment is sent. In fact, larger initial values have been proposed as means to improve performance ....

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Heidemann J., Performance Interactions Between P-HTTP and TCP Implementations, in ACM Computer Communication Review, April 1997.

....reveal the vulnerability of short TCP flows. Seddigh et al. 2] show the negative impact of the initial timeout value on the short TCP flow latency and propose to reduce the default recommended value. To enhance the performance of short TCP flows, a number of proposals, e.g. 12] 13] 14] [15] suggest to either use a large initial window value or share the network measurement information from previous records or communication with neighbors. Notice that these proposals require modification of the TCP protocol and may lead to congestion collapse. Our proposed scheme differs from these ....

J. Heidemann, "Performance Interactions Between P-HTTP and TCP Implementations," ACM Computer Communication Review, vol. 27(2), pp. 65--73, April 1997.

....substantially affect Web access for the vast majority of users. Most users see end to end latencies of about 250 ms and use modem lines. Bandwidths over 200 Kbps are required to provide user noticeable performance improvements. This conclusion is similar to the conclusion of our study. Heidemann [19] analyze the performance interaction between persistent HTTP (PHTTP) and TCP implementations. Initial P HTTP implementation has problems such as TCP delayed acknowledgements and multiple slow starts per TCP connection . Solutions given by Heidemann [19] that makes P HTTP performance better than ....

....to the conclusion of our study. Heidemann [19] analyze the performance interaction between persistent HTTP (PHTTP) and TCP implementations. Initial P HTTP implementation has problems such as TCP delayed acknowledgements and multiple slow starts per TCP connection . Solutions given by Heidemann [19] that makes P HTTP performance better than standard HTTP. But according to 6Bernardo [21] on average a user accesses just one URL at a site, which negates the benefit of using persistence. Thompson et al. [20] developed a monitoring system to capture and analyze Internet traffic on OC 3 trunks ....

Heidemann, J., "Performance Interactions Between P-HTTP and TCP Implementation," ACM Computer Communication Review, 27 2, 65-73, April 1997.

....for small data transfers (like the Web s requests and responses) Nagle algorithm, which tries to avoid the overhead of small packets can introduce delays to Web requests . Multiple connections are often used for physically co located transfers These and other problems have been discussed in [10, 13, 12, 3, 6, 9, 4]. Many of the problems mentioned above are inherent to the HTTP 1.0 protocol and attempts have been made to fix them in HTTP 1.1. All of those changes concentrated on the interactions between HTTP and TCP protocols, trying to optimize how TCP is used within the HTTP protocol. There is also an ....

J. Heidemann, "Performance Interactions Between P-HTTP and TCP Implementation," ACM Computer Communication Review, 27 2, 65-73, April 1997.

....These results reveal the vulnerability of short TCP flows. Seddigh et al. 2] show the negative impact of the initial timeout value on the short TCP flow latency and propose to reduce the default recommended value. To enhance the performance of short TCP flows, proposals like [13] 14] 15] [16] suggest to either use a large initial window value or share the network measurement information from previous records or communication with neighbors. Notice that these proposals require modification of the TCP protocol and may lead to congestion collapse. Our proposed scheme differs from these ....

J. Heidemann, "Performance Interactions Between P-HTTP and TCP Implementations," ACM Computer Communication Review, vol. 27(2), pp. 65--73, April 1997.

....discusses avenues for future work. 2 Related Work Early research in the web community has traditionally been on performance optimization rather than service differentiation and QoS management. Protocol issues such as performance interactions between TCP and HTTP have been investigated at length [7, 9, 18, 21, 22]. Load balancing [5, 14, 26] and admission control [23] have often been used to improve scalability and predictability of web services. More recently, architectures were proposed for differentiated services and QoS control. In the simplest case, two classes of clients, premium and basic, were ....

J. Heidemann. Performance interactions between p-http and tcp implementations. ACM Computer Communication Review, 27(2), April 1997.

.... transfer (e.g. File Transfer Protocol (FTP) and Simple Mail Transfer Protocol (SMTP) and remote terminal traffic (e.g. telnet and rlogin) The introduction of the Web has created new performance challenges, as the request response nature of Web interactions is a poor match for TCP s byte stream [83]. Even before the introduction of the Web, interest in request response (transaction) protocols was reflected in the development of VMTP and T TCP. The delay and jitter sensitivity of audio and video based applications required transport protocols providing something other than reliable service. ....

J. Heidemann. Performance interactions between P-HTTP and TCP implementations. Computer Communication Review, 27(2), April 1997.

....to pipeline the transfers of these components to reduce latency. The main drawback of P HTTP, though, is that the persistent TCP connection imposes a linear ordering on the Web page components, which are inherently independent. The analysis of the interactions between P HTTP and TCP are given in [14]. This drawback of P HTTP led to the development of a comprehensive solution, which has two components. The first component, TCP session, de couples TCP s ordered byte stream service abstraction from its congestion control and loss 15 recovery mechanisms. The second component of the solution, ....

John Heidemann. Performance interactions between P-HTTP and TCP implementations. ACM Computer Communication Review, 27(2):tba, April 1997.

....even after we ensured the use of fully buffered I O in nnrpd, our benchmark still yielded better results with the Nagle algorithm disabled. The Nagle algorithm increases mean latency by 19 , and median latency by 4 . What causes this effect We present a somewhat simplified explanation (see also [4]) Consider the number of full sized TCP segments required to convey an NNTP response (such as a news article) If the response exactly fits an integral number of segments, then the Nagle algorithm has no effect, and the TCP stack sends each packet immediately. However, response sizes vary ....

.... the interactive X window system [17] In both of these cases, implementors quickly realized the need to disable the Nagle algorithm [3] More recently, the introduction in HTTP of persistent connections (the use of a single TCP connections for several HTTP requests) has led several researchers [4, 10] to similar conclusions. In general, any application that uses TCP as a transport for a series of reciprocal exchanges can suffer from this interaction. The effect would not appear when an entire request or response always fits in one TCP segment, but may be seen when the request or response is ....

J. Heidemann. Performance interactions between P-HTTP and TCP implementations. ACM Computer Communication Review, 27(2):65--73, http:// www.acm.org/sigcomm/ccr/archive/. April 1997.

....TCP delays acks by typically 200 ms. Our measurements indicate that Sun s Solaris delays acks by about 45 ms, on average. 3 Related Work Network designers understood that delayed acknowledgements may slow application communications, as described in [Stevens 98] Microsoft 98] and [Sun 98] Heidemann 97] discusses this problem in persistent HTTP. He states that the problem does not occur in HTTP, versions 1.0 and earlier, but we find it does. Microsoft acknowledges the problem [Microsoft 97] and [Microsoft 97] but indicates that it only occurs when making small sends. Nielsen 98] and [Nielsen ....

, Heidemann, J., Performance Interactions Between P-HTTP and TCP Implementations, ACM Computer Communication Review, April 1997

....bandwidth, a real TCP implementation must have knowledge about the bandwidth that has been available recently. This suggests the advantage of preserving and sharing information about network conditions; this has been proposed in several different contexts [BSSK97, SSK97, Tou97, BPS 98, PK98, Hei97, SAA 98] 3.3 Limits of the Optimal Model 3.3.1 Bandwidth Delay Product This model of optimal performance of TCP flows assumes that the flow is able to send increasingly faster, without reaching the bottleneck bandwidth, or suffering any losses. However, even if we assume that the path is ....

John Heidemann. Performance interactions between P-HTTP and TCP implementations. ACM Computer Communications Review, 27(2), April 1997.

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John Heidemann. Performance interactions between P-HTTP and TCP implementations. Computer Communications Review, 27(2), April 1997.

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J. Heidemann, Performance interactions between P-HTTP and TCP implementations, ACM Computer Communications Review 27 (2) (1997) 65--73.

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J. Heidemann, "Performance Interactions Between P-HTTP and TCP Implementations" , ACM Computer Communication Review, 27 2, 65-73, April, 1997.

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J. Heidemann. Performance Interactions between P-HTTP and TCP Implementations. ACM Computer Communication Review, 27(2):65-- 73, April 1997. (pp 22, 120, 161)

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J. Heidemann. Performance interactions between p-http and tcp implemenation. ACM Computer Communicatoin Review, 27(2):6573, April 1997.

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J. Heidemann. Performance Interactions Between P-HTTP and TCP Implementations. In ACM Computer Communication Review, April 1997.

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J. Heidemann, " Performance interactions between P-HTTP and TCP Implementations," ACM Computer Communication Review, vol. 27, no. 2, pp. 65-73, April 1997.

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J. Heidemann, "Performance Interactions Between P-HTTP and TCP Implementations" , ACM Computer Communication Review, 27 2, 65-73, April, 1997.

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J. Heidemann, "Performance Interactions Between P-HTTP and TCP Implementations" , ACM Computer Communication Review, 27 2, 65-73, April, 1997.

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John Heidemann. Performance interactions between P-HTTP and TCP implementations. ACM Computer Communication Review, 27(2):65-73, April 1997.

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J. Heidemann, "Performance Interactions Between P-HTTP and TCP Implementations", ACM SIGCOMM, Computer Communication Review, Vol. 27, No. 2, pp. 65-73, April 1997.

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