[TCP] illinois: Incorrect beta usage
authorStephen Hemminger <shemminger@linux-foundation.org>
Thu, 29 Nov 2007 14:10:55 +0000 (01:10 +1100)
committerHerbert Xu <herbert@gondor.apana.org.au>
Thu, 29 Nov 2007 14:10:55 +0000 (01:10 +1100)
commita357dde9df33f28611e6a3d4f88265e39bcc8880
tree181c8b1508a84ca30d32c779a508bb475fb96077
parent5e5234ff17ef98932688116025b30958bd28a940
[TCP] illinois: Incorrect beta usage

Lachlan Andrew observed that my TCP-Illinois implementation uses the
beta value incorrectly:
  The parameter  beta  in the paper specifies the amount to decrease
  *by*:  that is, on loss,
     W <-  W -  beta*W
  but in   tcp_illinois_ssthresh() uses  beta  as the amount
  to decrease  *to*: W <- beta*W

This bug makes the Linux TCP-Illinois get less-aggressive on uncongested network,
hurting performance. Note: since the base beta value is .5, it has no
impact on a congested network.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
net/ipv4/tcp_illinois.c