Re: SMTP over UDP (was: newbie check...)
- On Aug 29, 2013, at 3:14 PM, Wietse Venema wrote:
>> It's standard SMTP over tcp, typically with STARTTLS and AUTH. IGood. Then I won't reconfigure my firewall until further notice...
>> imagine the udp entry is a historical artifact.
> Plaintext SMTP over UDP would require that the MTA invents major
> parts of TCP, including the parts that deal with packet loss,
> out-of-order arrival, and flow control.
- On 8/30/2013 10:12 AM, Terry Gilsenan wrote:
> I am not talking about implementing SMTP on UDP, I am taking about the possibility of adding a side-channel for bulk data that would use UDP.I'm really surprised nobody has mentioned this yet. It seems there's a
far simpler solution to the described high latency low bandwidth
attachment transfer problem: TCP send/receive buffer size.
If all receiving systems advertised a sufficiently large receive buffer
and clients could match it, then this latency/bandwidth problem pretty
much evaporates. A 1MB buffer allows a 50MB attachment to be sent
requiring only 50 ACKs. Assuming the path is fairly reliable, which has
been your assumption in your UDP argument, then this is a far less
invasive solution with similar performance.
IIRC, not may years ago, a team comprised of personnel at Argonne and
CERN achieved sustained saturation of a 1 Gbps link between Chicago and
Geneva, using parallel FTP and an insanely large TCP buffer, like in the
multiple GB range. I'll have to dig it up.
This demonstrates that high bandwidth TCP over high latency links is