Tcp characteristics pdf

Of particular concern congestion windows [5]. More details of this study can be found in [21]. SACK [25]. A set of web-like flows and a set 0 50 Time of small TCP flows were also used as background noise for all the simulation. They were short-lived flows that lasted for a few seconds. Only the second half was of interest because this research focused on the steady-state behavior. Descriptions of Scenarios for the Experiments We used three sets of primary flows in most of this study.

This network environment we refer to as Ideal Condition. The Fig. Evolution of Congestion Window for a Single Flow second network environment represented the situation where there were systemic losses or losses not directly related to congestion. We call it Lossy Link Condition. Some number of before 50 seconds RED case. The second observation is that packets were randomly dropped from the flows, with a defined HSTCP has an oscillatory behavior with a very short period.

The third network environment explored the reaction The third important observation is the influence of router of the flow sets to bursty traffic, so we refer to it as Bursty queue management on the behavior of both flows. With DT Traffic Condition. The bursty traffic was composed of short- queuing, drops did not occur until the router buffer overflowed.

With RED queuing, the router sends the congestion signal earlier. In the case of an empty network this can lead to lower VI. This section presents the results of our experiments. Ideal Condition the cases where there is a significant difference in the results, results for each individual queuing policy are presented. Isolated Flows flows, when there was no external interference, except the This first experiment allowed us to observe the basic be- background traffic.

The experiment ran only one time, without external This graphic shows that the HSTCP flows can reach full interference. The REGTCP flow takes The following graphic in Figure 6 presents the congestion around seconds to reach the bandwidth limit in congestion event rate for the first and second set of flows, when RED was avoidance. HSTCP produces a higher congestion event rate. When we used DT as the router queue management policy, it generated a slightly higher rate 30 of congestion events but otherwise was similar.

The third line is the result for all the flows combined. This fact is independent of the type of router queue Fig. Relative Fairness - Ideal Condition management used.

The relative fairness for the mixed flow set is depicted in RED is deployed, the relative fairness is better than when DT Figure 8. It shows the ratio between the amount of bandwidth is used.

This result is of flows increases. Bandwidth Stolen - Ideal Condition 0 Link Loss Rate This graph shows that the amount of bandwidth stolen decreases as the number of flows increases.

This fact highlights Fig. Although the amount of bandwidth stolen decreases We see that, as expected, the difference between the band- as the number of flows increase, the distance between the width used by the HSTCP flows and that used by the REGTCP amounts stolen between RED and DT increases slightly flows decreases as the number of losses increases.

Another important aspect to point out is that, for a link loss rate around C. We used the simulator error model to simulate D.

Bursty Traffic Condition losses on the bottleneck link. This loss model was set to drop This set of experiments helps us to understand the reaction a packet with a defined average drop rate. The first set contained 10 to bursty traffic. We used three sets of flows in this experiment. The first flows. On the other hand, the impact on the set of REGTCP flows is higher, and their 40 performance goes down quickly as the number of perturbations increases. The E.

It could be caused by the occurrence deployed with it. They also present the link presented in Figure One line is the aggregated result of utilization of all the flows together. The remaining line represents the link utilization REGTCP flows used, and it avoids allowing the link to become of the perturbations. This this performance remains relatively constant as the number of number appears to be highly dependent on the type of router perturbations increases.

The relative fairness for the mixed flow set is depicted in The ratio between the amount of bandwidth used by the Figure It is almost constant for both queuing policies.

We used two sets of flows to develop this experiment. We present here only the per flow relative fairness. The intention is to show the competition that a parallel stream transmission represents for a single long-lived regular TCP flow. The amount of link bandwidth used for the aggregate 90 parallel stream transmission is divided by the amount of link 80 bandwidth used by one of the 10 long-lived streams.

The results are presented in Figure This behavior only changes when there is a heavy 30 packet loss rate. In contrast, the relative fairness when HSTCP 20 is used is not constant and has a wide range of values.

The first set contains 10 REGTCP flows representing the long- 80 lived flows and also 1, 4, 7, 10 or 20 parallel streams. We observe in these graphics that when RED is used 30 the relative fairness increases as the number of perturbations 20 increase, but this behavior is not clear when DT is deployed. In 10 the DT case the ratio between the bandwidth used by HSTCP 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 and the bandwidth used by the 10 long-lived flows spreads Number of Flows over a wide range of values.

These are grouped below by topic. The major drawback in Regular TCP is that it dramati- 20 cally reduces the size of the congestion window in response to 10 a congestion event and its ACK-clocked congestion window 0 grows in increments of one.

This leads to slow recovery 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 from a congestion event when the congestion window was Number of Perturbations very large and leaves the link with a low level of utilization Fig.

This characteristic increases its average link utilization. For the conditions of our study, a link TCP. When they were submitted to bursty traffic 20 15 condition, the aggregated relative fairness was almost constant 10 using DT, but seemed to increase slightly when RED was used. In this work six Regular Fig. But these numbers depend totally on the average packet drop rate in the experiment.

This D. Use For Bulk Data Transfer was due to the bursty nature of these perturbations. This represents an advantage over other types of bulk data transfer such B. Fairness Impact as parallel streams. For parallel streams it is necessary to The bandwidth share used by the HighSpeed TCP flows change the application programs and to know a priori the was higher than that used by Regular TCP flows, when both number of parallel flows to transmit.

Also, in our opinion, types of flows competed for the same link. However, it was HighSpeed TCP presents better fairness and adaptability to an noticeable that the amount of the link bandwidth used by the environment of variable congestion event rates than other bulk HighSpeed TCP flows decreased as the total number of flows data transfer mechanisms, because of its different response increased.

The opposite happened with the Regular TCP flows. Parallel streams may also present better adaptability The reason for this behavior was that the higher the number of if they use some kind of adaptative control, as fractional flows competing for the link bandwidth, the more congestion congestion control [27], but at a cost of their simplicity. With the decrease in the HighSpeed TCP systemic packet losses, the packet loss rate will define the aggressiveness, the Regular TCP flows had more opportunity maximum available throughput.

It is possible to change this to use the bandwidth available. It is more aggressive at using the HighSpeed TCP should, by design, perform better or the same available bandwidth, but it decreases its aggressiveness as as Regular TCP. This adaptability is very VIII. It avoids having TCP has difficulty fully utilizing network links with a a link become idle caused by the slow dynamic of Regular high bandwidth delay product. HighSpeed TCP is easy Bursty traffic had only a small influence on the amount to deploy avoiding changes in routers and programs.

Effects of Router Queue Management with other solutions already in use. The change of the queue management scheme did not A point of concern is its fairness at low speeds, mainly significantly affect the link utilization of HighSpeed TCP flows in networks with droptail routers. A better relation with TCP in most cases. It did, however, cause a difference in the amount may be achieved by adjusting its three parameters, in particular of congestion events; RED requires fewer congestion events Low Window.

Pacing could help with droptail routers, and policies was clear when HighSpeed TCP was submitted to improve fairness. Futher studies in this area should be carried bursty traffic. Jinand, D. Wei, S. Low, G. Buhrmaster, J. Bunn, D. Choe, assessment of its deployment. Some have already began [28], R. Cottrell, J. Doyle, W. Feng, O. Martin, H. Newman, F. Paganini, S. Ravot, and S. So far, no unexpected behavior was found.

Choe and S. TCP connections. Then just click OK. In many ways, it is more interesting to look at how TCP does its job than the functions of the job itself. We can also see the many ways that it contrasts to its simpler transport layer sibling, UDP. The following are the ways that I would best describe the Transmission Control Protocol and how it performs the functions described in the preceding topic:.

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