Question on RFC6298, Managing the RTO Timer and additional lost pakets in Recovery state

Hi

I am trying to understand the Linux TCP stack and how it rearms the RTO tim=
er, in the process I  read section 5 in RFC6298.
It says quote "(5.3) When an ACK is received that acknowledges new data, re=
start the retransmission timer so that it will expire after RTO seconds (fo=
r the current value of RTO)."
What is the definition of new data ?. The strict interpretation is when SND=
.UNA advances, but it can also be that the highest SACKed sequence number i=
ncreases. The former case it is more likely that RTO happens.

The second question is Linux related. Given that a lost packet puts the sta=
ck in Recovery state, the congestion window reduces one step as an effect o=
n this. What happens if additional packets are lost when in Recovery state.=
 I guess the congestion window should decrease more or ?.

I am currently porting the Linux TCP stack to fit our Java based system sim=
ulator, most things seem to be working but the above leaves me wondering.

/Ingemar

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Ingemar Johansson  M.Sc.
Master Researcher

Ericsson AB
Wireless Access Networks
Labratoriegr=E4nd 11
971 28, Lule=E5, Sweden
Phone +46-1071 43042
SMS/MMS +46-73 078 3289
[email protected]<mailto:[email protected]>
www.ericsson.com

"We can be heroes,
  just for one day"
    David Bowie
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