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An Investigation into Transport Protocols and Data Transport ...

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9.3. Internet Transfers 239<br />

10000<br />

cwnd<br />

ssthresh<br />

10000<br />

cwnd<br />

ssthresh<br />

cwnd <strong>and</strong> ssthresh (packets)<br />

8000<br />

6000<br />

4000<br />

2000<br />

cwnd <strong>and</strong> ssthresh (packets)<br />

8000<br />

6000<br />

4000<br />

2000<br />

0<br />

0 50 100 150 200 250 300<br />

Time (seconds)<br />

(a) HSTCP<br />

0<br />

0 50 100 150 200 250 300<br />

Time (seconds)<br />

(b) ScalableTCP<br />

Figure 9.34: Slow Convergence of HSTCP <strong>and</strong> ScalableTCP over long distance<br />

high capacity Internet links.<br />

10 1<br />

Stability<br />

10 0<br />

St<strong>and</strong>ard TCP HSTCP ScalableTCP HTCP FAST BicTCP<br />

New−TCP<br />

Figure 9.35: Stability from CERN to LBL.<br />

Stability<br />

Figure 9.36 shows that FAST, H-TCP <strong>and</strong> BicTCP have similar median<br />

stabilities, with FAST showing a wider range of stability values.<br />

The other New-TCP algorithms show similar stability profiles, mostly<br />

because of the lack of congestion epochs as shown in Figure 9.34.<br />

Overhead<br />

HSTCP has the lowest transfer overhead as shown in Figure 9.36. However,<br />

these results have to be taken with care due to the lack of congestion epochs

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