Re: dual stack & IPv6 on by default

[Alain Durand <Alain.Durand@Sun.COM>]

On Saturday, March 8, 2003, at 01:06  PM, Mika Liljeberg wrote:

> For IPv4, RFC1122 defines the ICMP errors that are to be treated as 
> soft
> errors, but does not state any special conditions for the connect 
> phase.
> It does say the following:
>
>             An attempt to open a TCP connection could fail with
>             excessive retransmissions of the SYN segment or by receipt
>             of a RST segment or an ICMP Port Unreachable.  SYN
>             retransmissions MUST be handled in the general way just
>             described for data retransmissions, including notification
>             of the application layer.
>
> However, port unreachable is classified as a hard error. Treating the
> other unreachable errors as hard errors during connect bends the rules 
> a
> little bit (in a nice way IMO).
RFC1122, section 4.2.3.5 says more just bellow what you quote:

            However, the values of R1 and R2 may be different for SYN
            and data segments.  In particular, R2 for a SYN segment MUST
            be set large enough to provide retransmission of the segment
            for at least 3 minutes.  The application can close the
            connection (i.e., give up on the open attempt) sooner, of
            course.

            DISCUSSION:
                 Some Internet paths have significant setup times, and
                 the number of such paths is likely to increase in the
                 future.

==> I understand from that section that a TCP implementation should
        wait 3 minutes on a SYN-sent before timing out.
       Do I miss something? Is this recommendation widely ignored?

	- Alain.