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| n |
processing
ACKs from MH:
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– |
new
ACK: common case, initiates cleaning up of snoop cache,
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update
estimate of round-trip time for wireless link, forward ACK
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to FH
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– |
spurious
ACK: less than last ACK seen, happens rarely. Just drop
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ACK
and continue
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duplicate
ACK: indicates packet loss, one of several actions:
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n |
packet
either not in cache or marked as retransmitted: pass duplicate
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ACK on
to FH
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n |
first
duplicated ACK for cached packet: retransmit cached packet
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immediately
and at high priority, estimate number of expected
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duplicate
ACKs, based on # of packets sent after missing one
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n |
expected
successive duplicate ACKs: ignore, we already initiated
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retransmission.
Since retransmission happens at higher priority, we
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might
not see total number of expected duplicate ACKs
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