Anycast provider for SMTP?

Wed Jun 17 02:50:11 UTC 2015

In message <82D10008-CB76-42C7-A78C-EE876924DF1E at pch.net>, Bill Woodcock writes:
>
> > If you read what Joe wrote, he doesn't currently have an AS number or
> > employ BGP with his Internet providers. Extrapolate for his IPv4
> > assignment situation and the /24 announcement barrier. In an
> > IPv4-depleted world, he won't be doing anycast any time soonâ€¦
>
> â€¦which is one of the reasons why I suggested that he do anycast DNS
> (presumably using a DNS service provider) rather than anycast SMTP
> (presumably using himself) anyway.
>
> So, regardless of how much youâ€™re rolling your eyes, weâ€™re saying the
> same thing.  Weâ€™re just being testy about the details.
>
>                                 -Bill

If you are that worried about a anycast SMTP/TCP session breaking,
you will be just as worried about a anycast DNS/TCP session breaking.

That said the problem is that a client SMTP server doesn't retry
fast enough when a TCP session breaks mid transaction.  Anycast TCP
will not fix this.  I'm not aware of any SMTP client that takes 4
hours to try the next MX when connect fails and it was a 4 hour
retry that was the complaint.

Anycast will only help if the SMTP client doesn't try all the lowest
cost MX's and there are very few broken SMTP clients that do this.
The best fix for these is to identify the clients and get them
upgraded to something that is RFC compliant.  Trying multiple MXs
is a 20+ year old requirement.

Basically you are wasting your money on anycast SMTP.

Mark
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org