TCP-PCP: A Transport Control Protocol Based on the Prediction of ...

S1
Si
Sn
100 Mbps
3 ms
R1
20 Mbps
40 ms
R2
10 Mbps
3 ms
Fig. 9: Network topology 3
metric, in which the network settings are marked. As shown
in Fig.9, 10 same <strong>TCP</strong>-<strong>PCP</strong> flows share a 20 Mbps bottleneck
link.
We use Jain’s fairness index to justify the fairness of
<strong>TCP</strong> variants Ref. [14]. Simulation results are summarized in
Table II, which show that all <strong>TCP</strong> variants including <strong>TCP</strong>-
<strong>PCP</strong> achieve fairly satisfactory fairness index with different
link losses. Meanwhile, it is shown from Table II that <strong>TCP</strong>-
<strong>PCP</strong> still keeps higher throughput than Westwood and Jersey
in this case.
TABLE II: Comparison of fairness and throughput
Westwood Jersey <strong>TCP</strong>-<strong>PCP</strong>
LossRate Thru Fair Thru Fair Thru Fair
(kbps) (-) (kbps) (-) (kbps) (-)
0 1759 0.935 1783 0.962 1795 0.997
0.001 1741 0.998 1757 0.999 1761 0.999
0.005 1612 0.999 1619 1.0 1647 1.0
0.01 1457 0.999 1489 0.998 1532 0.999
D. Friendliness analysis
The experiment of friendliness partitions ten flows into two
parts, one uses <strong>TCP</strong>-<strong>PCP</strong>, the other uses the traditional <strong>TCP</strong>
protocol, such as Westwood.
Table III gives the change of average throughput, which is
calculated by summing up the throughput of the same <strong>TCP</strong>
variant and divided by the number of connections. It is clear
that the bandwidth allocation of <strong>TCP</strong>-<strong>PCP</strong> and Westwood is
close to its fair share without link loss occurring. When the
link loss rate raises from 0.1% to 1%, <strong>TCP</strong>-<strong>PCP</strong> achieves
higher throughput than Westwood. The results are according
with that of one <strong>TCP</strong> flow. But the increase is within a
tolerable range as regard to friendliness performance. It can be
concluded that <strong>TCP</strong>-<strong>PCP</strong> can coexist friendly with Westwood.
V. CONCLUSION
In this paper we proposed a novel <strong>Transport</strong> <strong>Control</strong> <strong>Protocol</strong>
based on the prediction of Congestion Probability. It
can improve <strong>TCP</strong> throughput in hybrid networks because the
sender judges network state by serial ECN feedbacks other
than single ECN feedback or packet dropping.
Actually, the congestion-aware scheme used in <strong>TCP</strong>-<strong>PCP</strong>
can be easily extended to existed <strong>TCP</strong> variants. Our next works
focus on checking its function on other <strong>TCP</strong> variants both on
NS2 simulation and wired/wirelss testbed.
D1
Di
Dn
TABLE III: Friendliness Performance
Loss rate: 0 Loss rate:0.001
Westwood:<strong>TCP</strong>-<strong>PCP</strong> Westwood <strong>TCP</strong>-<strong>PCP</strong> Westwood <strong>TCP</strong>-<strong>PCP</strong>
(kbps) (kbps) (kbps) (kbps)
3:7 1162.00 1174.85 1161.33 1174.14
5:5 1316.80 1331.40 1312.80 1329.40
7:3 1519.28 1536.66 1511.00 1539.00
Loss rate: 0.005 Loss rate:0.01
Westwood:<strong>TCP</strong>-<strong>PCP</strong> Westwood <strong>TCP</strong>-<strong>PCP</strong> Westwood <strong>TCP</strong>-<strong>PCP</strong>
(kbps) (kbps) (kbps) (kbps)
3:7 1289.66 1314.85 1099.00 1186.57
5:5 1294.80 1319.80 1269.80 1352.2
7:3 1485.28 1508.33 1388.14 1506.00
ACKNOWLEDGEMENT
This work was partially supported by the National Natural
Science Foundation of China (60673164), Provincial Natural
Science Foundation of Hunan (06JJ10009), the Specialized
Research Fund for the Doctoral Program of Higher Education
of China (20060533057), Program for New Century Excellent
Talents in University (NCET-05-0683), CityU Strategic
Research Grant No. 7002214.
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This full text paper was peer reviewed at the direction of IEEE Communications Society subject matter experts for publication in the IEEE "GLOBECOM" 2008 proceedings.