Thus spake "Daniel Senie" <dts(_at_)senie(_dot_)com>
At 01:00 PM 4/20/2003, Richard Carlson wrote:
The question is - how do we provide some feedback to apps that
they are trying to cross a scope boundary that it's a permanent error
condition (5xx in SMTP verbiage)? One proposed notification
method is the site-local prefix. Other methods can be created, but
something needs to be done and simply killing site-locals and
ignoring the underlying scoping issue is a non-starter.
You mean aside from applications understaning that an ICMP
Destination Unreachable / Administratively Prohibited response from
the site firewall?
Many firewalls simply drop packets which are prohibited without sending ICMP
responses, not to mention all the places that filter all ICMP
indiscriminately.
For that matter, IPv6 machines arguably could try their Site Local
address and be given that same feedback from the border router or
firewall, and use the response as an indication to go use their assigned
global address.
The vast majority of applications do not pick their source address, nor is
there a compelling reason for them to do so. A large number of applications
don't even handle multiple destination addresses properly, so expecting this
additional intelligence for the source address is irrational.
S
Stephen Sprunk "God does not play dice." --Albert Einstein
CCIE #3723 "God is an inveterate gambler, and He throws the
K5SSS dice at every possible opportunity." --Stephen Hawking