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Step 2: Server receives SYN packet and sends SYN + ACK packet SYN flag set, ACK flag set
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Sequence number specifies the server's starting sequence number. Acknowledgment number
means that the server has received X and expects X+1.
Step 3: Client receives SYN + ACK and send ACK back. ACK number means that server has
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received Y and expects Y+1.
RFC 6349 Testing Methodology
RFC 6349 is a practical testing methodology consisting of 4 different steps for measuring end to end TCP
Throughput and Performance in a managed IP network.
Step 1Max MTU Search:
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Search for the maximum packet length that can be sent through the network without segmentation.
The Path MTU search follows RFC4821 (Packetization Layer Path MTU Discovery).
Step 2Round Trip Time (RTT) Search:
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Measure of the roundtrip time between the TCP segment sent and the acknowledgment received,
the test has to be done in a network that is not congested to obtain the real round trip delay (not
accounting for network buffer delay).
Step 3Bottleneck Bandwidth (BB) Search:
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For this step, a Layer2/3 test can be done (RFC2544 or Y.1564) to determine the maximum through-
put rate supported by the network.
Step 4Bandwidth Delay Product Calculation:
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Based on RTT and BB results, the BDP is computed to estimate the optimal window size that should
be used for testing (Auto mode). User can also specify fixed window size.
Key Metrics:
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