[170380] in North American Network Operators' Group
Re: IPv6 isn't SMTP
daemon@ATHENA.MIT.EDU (Franck Martin)
Wed Mar 26 22:17:44 2014
From: Franck Martin <fmartin@linkedin.com>
To: Fred Baker <fred@cisco.com>
Date: Thu, 27 Mar 2014 02:16:40 +0000
In-Reply-To: <A235C285-8934-4908-A789-24DAA9E2393D@cisco.com>
Cc: North American Network
Operators Group <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
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On Mar 26, 2014, at 5:47 PM, Fred Baker (fred) <fred@cisco.com> wrote:
>=20
> On Mar 25, 2014, at 8:31 PM, Cutler James R =
<james.cutler@consultant.com> wrote:
>=20
>> 3. Arguing about IPv6 in the context of requirements upon SMTP =
connections is playing that uncomfortable game with one=92s own combat =
boots. And not particularly productive.
>=20
> That is one of my two big take-aways from this conversation. The other =
is that operators of SMTP MTAs should implement RDNS for them, which I =
thought we already knew.
It is in several industry recommendations cf for instance BCP at =
www.m3aawg.org=20
>=20
> To my knowledge, there are three impacts that IPv6 implementation =
makes on an SMTP implementation. One is that the OS interface to get the =
address of the next MUA or MTA needs to use getaddrinfo() instead of =
gethostbyname() (and would do well to observe RFC 6555=92s =
considerations). Another is that, whether on an incoming or an outbound =
connection, when the application gets its own address from the OS =
(binary or as a character string), it needs to allocate more storage for =
the data structure. The third is that it needs to be able to interpret =
user@2001:db8::1 as well as user@dns-name and user@192.0.2.1.=20
>=20
and user@2001:db8::1.25 with user@192.0.2.1:25. Who had the good idea to =
use : for IPv6 addresses while this is the separator for the port in =
IPv4? A few MTA are confused by it.
> All things considered, that=92s a pretty narrow change set.
>=20
> Everyone here, no doubt, is clueful enough to implement RDNS for their =
MTAs. We know that there are people in the world that don=92t implement =
it for IPv4. Yet, here we are, using SMTP/IPv4 to discuss this, and I =
don=92t hear anyone saying that IPv4 isn=92t ready for prime time as a =
result of the fact of some operators not implementing RDNS.
>=20
There is some confusion between MX selection and address selection, I =
tried to document it, and resolve the ambiguities in =
http://datatracker.ietf.org/doc/draft-martin-smtp-target-host-selection-ip=
v4-IPv6/ (comments at apps-discuss@ietf.org)
Remember 70 to 90% of email is spam, blacklists can drop as much as 75% =
of spam at connection time (an IPv6 blacklist has problems due to size =
and impact on DNS). If we mess up the transition of SMTP to IPv6, less =
than 1 out of 10 emails in your mailbox will be remotely interesting=85.
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