Re: Name resolution limits
Re: Name resolution limits
- Subject: Re: Name resolution limits
- From: Jason Linhart <email@hidden>
- Date: Fri, 8 Feb 2002 17:32:35 -0500
On 2/8/02 3:53 PM Chris Hanson (email@hidden) wrote:
>
At 6:06 PM -0800 2/7/02, jud spencer wrote:
>
>On 2/7/02 5:53 PM, "Josh Graessley" <email@hidden> wrote:
>
>
>
>> This is not a problem with Mac OS Xs networking, this is a problem with
the
>
>> design of the APIs used to lookup names. The APIs are written for a world
>
>> where you simply block to wait for an operation to complete.
>
>
>
>Hmm., which to someone like me (who's customers are pressuring me to release
>
>an OSX version of my mail server that has better performance than the OS9
>
>version) sounds like it is a problem with OSX networking.
>
>
It's definitely a problem with Mac OS X networking. It's just not a
>
problem *unique* to Mac OS X networking, but rather one inherited
>
from Unix.
>
>
Since Windows uses the BSD socket API as well, doesn't it also have
>
this limitation?
This was only a limitation in Unix as of 1992. Sun solved this problem
with the introduction of gethostbyname_r in 1992 and every other shipping
Unix like system added support for it years ago. There are similar _r
interfaces for all the other related routines. The thread safe versions
appear to be part of the POSIX standard, as of somewhere around 1999.
Some of the early implementations were serialized (limited to one lookup
at a time by a mutex or lock), despite the thread safe interface. But the
major platforms have supported true overlapped lookups for some time. Sun
has been doing it correctly since 1992. BIND 8 was the first version of
BIND to be thread safe and was released in 1997. Linux and FreeBSD use
BIND for their resolver library and became thread safe and overlapped not
too long after that.
Windows never had this problem. Their Internet access interface was fully
thread safe from the start (available earlier, but practical to use
somewhere around 1991). They apparently serialized lookups for awhile at
first. Various sources disagree about when the change to overlapped
lookups happened exactly, but I know that they have not been serialized
in the last three years.
Jason
-----------------
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-----------------
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as a searing indictment of the narrow-minded binary counting system.
-- Peter van der Linden, Expert C Programming, Deep C Secrets
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