[Planetlab-users] limit on number of connections to a port

[Vivek Pai]

Ioan Raicu wrote:

> If you do a "ulimit -a", you will get the OS specific limits; most 
> likely, your open file descriptors are limited to 1024 (per 
> process)... but this can be raised with the ulimit command.  On a dual 
> Opteron

As Neil Spring indicated in an earlier message, the current maximum per
process is set to 4K on PlanetLab. This is configurable (by root), but 
so far,
few services have had a problem with this limit.

> system running SuSe Linux 9, I was able to get 60K+ concurrent TCP 
> connections.... which got pretty close to the fundamental limits of 
> 64K ports (8 bit value).

While this portion isn't relevant to PlanetLab, it's worth pointing out
that the port number is 16 bits, and 60K connections isn't some
fundamental limit. Flows are identified using a 5-tuple of source and
dest addresses and port numbers, and the protocol. If you have have more
than one client machine (or even multiple IP addresses on a single 
machine),
you can easily have more than 64K of these 5-tuples. If the OSes are
configured right, you can generate a practically unlimited number of
flows.

-Vivek

> Ioan
>
> Neil Spring wrote:
>
>> If by "connections" you mean TCP connections, then yes, your 
>> application can only have as many connections as file descriptors 
>> (sockets) allocated by the kernel.  (4,000-ish, I think, though 
>> people who have run into this limit are more likely to know).
>>
>> I don't think you're giving enough precise information for a smarter 
>> answer.  Information like which system call fails with what errno 
>> value (perhaps from strace) would be helpful, but likely much more is 
>> required.
>>
>> -neil
>>
>>
>> On Oct 4, 2006, at 3:00 AM, Parul Halwe wrote:
>>
>>>
>>> Hello All,
>>>         Is there any limit on number connections that can be made to 
>>> a particular port? I am developing an application that requires 
>>> sending data packets. Initially everything works fine but after some 
>>> time I am not able to establish connection to that port.
>>>
>>> Thanks and Regards,
>>> Parul Halwe
>>>
>>> --Parul Halwe
>>> Student
>>> M.Tech - 2nd Year
>>> Computer Science and Engg. dept.
>>> IIT Bombay
>>>
>>> _______________________________________________
>>> Users mailing list: Users at lists.planet-lab.org
>>> https://lists.planet-lab.org/mailman/listinfo/users
>>
>>
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>