tcp hostcache and ip fastforward for review

Jonathan Mini mini at freebsd.org
Mon Nov 10 02:41:56 PST 2003


On Nov 10, 2003, at 1:39 AM, Andre Oppermann wrote:

> Jonathan Mini wrote:
>
> All in all I don't think it is worth adding this complexity.

I agree.

>> This is actually a small value for TCP connections which are being
>> used to forward messages, especially on gigabit links.
>> Heavily-intensive
>> web applications that are using small HTTP requests (pipelined inside 
>> a
>> persistent connection) to update small manipulations of state are
>> a good example of this.  I wouldn't be surprised to see chatter
>> between SQL servers follow similar patterns.  Applications which
>> use XML-based messaging often send several small packets per message,
>> which is unfortunate.
>
> Do you think such applications manage to send 1000 packets per second
> with less than 256 bytes payload per packet? I think the network code
> would collect some data to form a larger packet (unless TCP_NODELAY
> set)?

Traffic like that only happens when TCP_NODELAY is set.  Otherwise, you
get what you would expect.

>> On the other hand, I'm used to looking at proxies, which are not
>> the general case.  This is why the limits are tunable, after all. =)
>
> Is there way you could monitor such connections and compile some
> statistics how many small packets per second are sent? I could adjust
> the patch to just report the fact instead of dropping the connection.
> Could do it for 4.9-R too, it's fairly easy.

Alas, no.  This is from anecdotal experience from our support staff at
work.

-- 
Jonathan Mini
mini at freebsd.org
http://www.freebsd.org



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