On Wed, Aug 14, 2024 at 06:48:38AM -0700, Dave Crocker via mailop wrote:
> Making a distance-sensitive assumption about traffic behavior is a
> suprisingly bad idea for anything having to do with the Internet. Resources
> and their uses can be -- and often are -- a long way away and using
> connections with wildly varied performance characteristics.
>
> I use a number of different email service and have no idea where any of
> their servers are, but suspect some are across a large ocean from me.
>
> The only time distance-sensitive assumptions might make sense is when the
> interaction is known to be -- and must be --- part of a LAN that both
> parties are on. Maybe.
Sure, and thus my suggestion to not push the timeout below 30s.
I am now in Melbourne AU, and see fairly high latency to many remote
services, but some of my MUA users are in the UK, and even when using
BT's mobile network both submission and remote delivery are well under
30s.
Jun 09 03:24:12 amnesiac postfix/submission/smtpd[3842186]: connect from
unknown[2a00:23ee:2550:44f9:7965:a6ab:fd66:c0fa]
Jun 09 03:24:14 amnesiac postfix/submission/smtpd[3842186]: Anonymous TLS
connection established from unknown[2a00:23ee:2550:44f9:7965:a6ab:fd66:c0fa]:
TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519
server-signature RSA-PSS (2048 bits) server-digest SHA256
Jun 09 03:24:15 amnesiac postfix/submission/smtpd[3842186]: 996078DF253:
client=unknown[2a00:23ee:2550:44f9:7965:a6ab:fd66:c0fa], sasl_method=PLAIN,
sasl_username=[censored]
Jun 09 03:24:17 amnesiac postfix/cleanup[3842190]: 996078DF253:
message-id=<[censored]>
Jun 09 03:24:18 amnesiac postfix/qmgr[3767137]: 996078DF253:
from=<[censored]>, size=15577, nrcpt=1 (queue active)
~2s for EHLO + TLS handshake, and ~4 more for another EHLO + mail transaction
Jun 09 03:24:22 amnesiac postfix/smtp[3842191]: Untrusted TLS connection
established to <censored>.mail.protection.outlook.com[52.101.68.10]:25: TLSv1.3
with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE
(secp384r1) server-signature RSA-PSS (2048 bits) server-digest SHA256
Jun 09 03:24:25 amnesiac postfix/smtp[3842191]: 996078DF253:
to=<[censored]>, relay=[censored].mail.protection.outlook.com[52.101.68.10]:25,
delay=10, delays=3.3/0.01/4.6/2.5, dsn=2.6.0, status=sent (250 2.6.0
<[censoured]> [InternalId=44293997727358,
Hostname=AS1PR07MB9618.eurprd07.prod.outlook.com] 25920 bytes in 0.177, 142.602
KB/sec Queued mail for delivery)
Here Postfix reports 3.3s from "MAIL FROM:" (start of transaction) to
receiving the complete message (pre-queue delay), 4.6s to connect,
perform a TLS handshake, and perform the inner EHLO, and 2.5s for the
mail transaction (message went back to Europe for delivery).
The entire prodcess (here back to the EU) took ~13s, with ping rtts to
the UK of ~300ms:
rtt min/avg/max/mdev = 290.789/291.338/291.659/0.280 ms
So 30s is I think generous enough for MUA to MSA traffic on or near Earth.
--
Viktor.
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