Re: [squid-users] 111 connection refused

tis 2006-11-21 klockan 16:28 -0500 skrev paulvmf@gmail.com:

> I think this is the answer, I have seen this page:
> http://www.squid-cache.org/Doc/FAQ/FAQ-14.html#ss14.5

> I hope that someone could explain me in detail about it, because I
> don't understand it at all.

ECN is an standard extension to TCP/IP, making TCP/IP behave better in
overload conditions where the available bandwidth is all used up (i.e.
the default condition for any WAN link).

Defined by Internet RFC3168 issued by the Networking Working Group at
IETF, the standardization body responsible for the evolution of TCP/IP
and other core Internet technologies such as routing.

It's implemented by using two previously unused bits (of 6) in the TCP
header, plus redefining two bits of the never standardized TOS field in
the IP header (dividing TOS in 6 bits Diffserv and 2 bit ECN fields),
allowing routers to clearly indicate overload conditions to the
participating computers instead of dropping packets hoping that the
computers will realize there is too much traffic.

The main problem is the use of those previously unused bits in the TCP
header. The TCP/IP standard has always said that those bits is reserved
for future use, but many old firewalls assume the bits will never be
used and simply drops all traffic using this new feature thinking it's
invalid use of TCP/IP to evolve beyond the original standards from 1981.

ECN in it's final form was defined 2001, but earlier specifications was
circulated several years earlier.

Regards
Henrik