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On Wed, Jun 06, 2001 at 01:55:08PM +0200, Ramón Agüero wrote:
> When a Duplicate ACK arrives, the tcp_fast_retrans function is called.
> Aparentely, this function does not trigger any retransmission unless
> tp->dup_acks == 3 or tp->fackets_out > 3. In some ocassions this is the
> behaviour I see (by tcpdump captures), but in other cases, the first dupack
> triggers a retransmission, although the number of sacked segments is only
> two. I have tried to see why this retransmission is trigerred, but I can't
> find it. Can anybody put some light in this tunnel :-) ?
You're probably seeing the Hoe heuristic, which extends Fast Retransmit to
fix more than a single lost packet per RTT. See Janey Hoe,
"Improving the startup behavior of a congestion control scheme for tcp".
It is a variant of NewReno as described in RFC2582.
-Andi
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