Re: [tcpm] TCP, DCCP, v6, and ICMP soft errors [draft-ietf-v6ops-v6onbydefault-01]

[Eddie Kohler <kohler@cs.ucla.edu>]

I think at this point we have to agree to disagree and, if this issue is 
considered important, get other opinions on it.

The best kernel APIs provide mechanism, not policy, since policy changes and 
different apps want different policies.  In my opinion 
draft-gont-tcpm-tcp-soft-errors codifies for all apps a policy that, if 
implemented, may/will reduce user-visible network connectivity.  Therefore it 
should not be accepted; a new draft should provide a "mechanism" for 
implementing the soft-error behavior you need, discuss how to use that 
mechanism, and also potentially talk about a higher-level, library API that DTRT 
by default.

Also, talking about "default behavior" and ease of app construction is a little 
disingenuous since there's no real installed base.  Only apps that implement 
address cycling need the new behavior; this is a small set.  Apps that don't 
cycle addresses: now there's an installed base.

If anyone had practical data on Destination Unreachable errors -- in particular, 
how transient they tend to be for today's hosts -- this would be a great time to 
speak up.  If Dest. Unreachable is frequently transient, that strengthens my 
case.  If it's very infrequently transient, that strengthens 
draft-gont-tcpm-tcp-soft-errors.

Thanks,
Eddie