Arnt Gulbrandsen wrote:
What I've never understood is why (almost) everyone tries addresses in
sequence instead of in parallel.
Even applications that routinely open two or more concurrent connections
to the server first try IPvX, then wait many seconds, then try IPvY. Why
not try both in parallel and use whatever address answers first?
Maybe because it would be a big waste of network bandwidth and close
to a Denial of Service (DoS) attack if every client would try every
IPv4 and IPv6 address in parallel that it can get hold of for a hostname.
Similarly, it could require a major redesign of lots of applications
in order to be able to manage several parallel requests
-- multi-threaded with blocking DNS-lookups and blocking connect()s
or parallel asynchronous/non-blocking DNS-lookups and connect()s.
I was hit by a funny Bug in Microsoft Windows NT 3.1 in 1993 when using
asynchronous connect()s for the first time. After the connection
timeout (60 seconds) I would still get an event delivered with
the original socket number -- even if I had long closed that
connect-pending socket and been reassigned the same socket number
on the next socket() call from the OS.
-Martin
_______________________________________________
Ietf mailing list
Ietf(_at_)ietf(_dot_)org
https://www.ietf.org/mailman/listinfo/ietf