What TCP Tells Us About the Network

Matt Mathis

1-July-99

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From any forward tap (1, 3, 5) alone:

Classic flow stats, (for both directions!)

Total data, total time, average rate, packet sizes

RTT, loss rate, and window (!)

Is the rate network or host limited?

Is the (potential) network bottleneck up or down stream?

Some application duplex problems

From any pair (e.g. 3, 4):

Receiver misstuning

Receiver CPU or application bottleneck

Receiver bugs (Closer to the receiver is better)

From pair near the sender (1, 2):

Sender misstuning

Sender CPU or application bottlenecks

Sender bugs

Percent duplicate data

At receiver indicates how well TCP is coping

Rises monotonicly towards the sender

Differential rise is quality of any given hop