[Python-Dev] socket.create_connection slow

[Steve Holden]

Eric Smith wrote:
> Kristján Valur Jónsson wrote:
>> Aha, thanks, since my wireshark wasn't working.
>> I boiled a few pints of water (thanks, Google) and came up with this:
>>
>> http://support.microsoft.com/kb/175523
>>
>> Here is the summary:
>> Note that with other implementations of TCP, such as those commonly
>> found in many UNIX systems, the connect() fails immediately upon the
>> receipt of the first ACK/RST packet, resulting in the awareness of an
>> error very quickly. However, this behavior is not specified in the
>> RFCs and is left to each implementation to decide. The approach of
>> Microsoft platforms is that the system administrator has the freedom
>> to adjust TCP performance-related settings to their own tastes, namely
>> the maximum retry that defaults to 3. The advantage of this is that
>> the service you're trying to reach may have temporarily shut down and
>> might resurface in between SYN attempts. In this case, it's convenient
>> that the connect() waited long enough to obtain a connection since the
>> service really was there.
>>
>> Yet another "undefined" thing affecting us, Martin.
> 
> I know it's pointless to express my shock here, but I can't resist. It's
> truly amazing to me that they'd delay the connect call's failure for a
> second by default, in hopes that the other end might come back up
> between SYN's. How often could that possibly happen?
> 
When I read it I was tempted to observe they must have been testing
Microsoft network services. It is a truly bizarre rationalization of a
default that appears to have been taken from DOS-era network client
applications. I remember demonstrating the phenomenon on a cli-based
Telnet client at least 15 years ago.

regards
 Steve
-- 
Steve Holden        +1 571 484 6266   +1 800 494 3119
Holden Web LLC              http://www.holdenweb.com/