topic Re: sendq size in Operating System - HP-UX

sendq size

Manoj P.U._1 — Tue, 22 Oct 2002 09:26:28 GMT

Hello
Can anybody help to find the maximum size of Send-Q that it can grow before closing the socket connection?

This problem (dropping socket connection) is occurring in hp-ux 11.00 with Java based Application (Socket programming)

Thanks

Manoj

Re: sendq size

T G Manikandan — Tue, 22 Oct 2002 09:46:08 GMT

check this link

http://bizforums.itrc.hp.com/cm/QuestionAnswer/1,,0xfb9ae7613948d5118fef0090279cd0f9,00.html

Thanks

Re: sendq size

U.SivaKumar_2 — Tue, 22 Oct 2002 10:11:07 GMT

Hi,

To find the current max value do this,
#ndd -get /dev/tcp tcp_connec_request_max

Increase the value .
#ndd -set /dev/tcp tcp_connec_request_max 2048

Make entries in /etc/rc.config.d/nddconf file
TRANSPORT_NAME[]=tcp
NDD_NAME[]=tcp_connec_request_max
NDD_VALUE[]=2048

to make setting permanent even after
reboot.

regards,
U.SivaKumar

Re: sendq size

Manoj P.U._1 — Tue, 22 Oct 2002 10:46:07 GMT

Hi Sivakumar

you are telling about the maximum number of request from a client that can be accepted by server tcp_conn_request_max.

But I need the maximum limit of Send_Q in tcp socket in server client tcp communication.

Thanks for reply

Manoj

Re: sendq size

U.SivaKumar_2 — Tue, 22 Oct 2002 11:03:40 GMT

Hi,

DO this please.

#/usr/sbin/ndd -set tcp_syn_rcvd_max 2000

Make approriate entries in nddconf also

regards,
U.SivaKumar

Re: sendq size

Manoj P.U._1 — Tue, 22 Oct 2002 11:21:21 GMT

Hi shivakumar

You are giving solution to keep the socket connection for long time. But I don't want to do that because the application is developed in that way, it will close the connection if it cannot write to the socket.

In which location you are working in HCL, I am in Mumbai, HCL.

Thanks

Manoj

Re: sendq size

Helen French — Tue, 22 Oct 2002 14:45:14 GMT

Daa Manoj,

Just got the message from CTK. Did you check the command 'netstat'. This command will tell you the value of Send-Q at the third column:

# netstat

Re: sendq size

U.SivaKumar_2 — Wed, 23 Oct 2002 03:24:57 GMT

Hi,

I think you can understand that parameter tcp_syn_rcvd_max perfectly now.

Maximum SYN received parameter limits the socket queue because it will drop connections
when it exceeds the value.

Moreover I have done lot of R&D on this paramter . So you have to belive me ;-)

To Reinforce my arguments , I would like to quote a reference from my collection:-

"While great effort is undertaken to defend any network from those with malicious intent, several ports (largely TCP) must remain open to conduct business. Internet vandals may attempt to exploit these ports to launch a denial of service attack. One of the most popular attacks remains the SYN flood, wherein the socket queue of the attacked host is overwhelmed with bogus connection requests. To defend against such attacks, certain UNIX variants maintain separate queues for inbound socket connection requests. One queue is for half-open sockets (SYN received, SYN|ACK sent), the other queue for fully-open sockets awaiting an accept() call from the application. These two queues should be increased so that an attack of low to moderate intensity will have little to no effect on the stability or availability of the server.

A. AIX

/usr/sbin/no -o clean_partial_conns=1

This setting will instruct the kernel to randomly remove half-open sockets from the q0 queue to make room for new sockets.

B. Solaris

/usr/sbin/ndd -set /dev/tcp tcp_conn_req_max_q 1024

The q queue holds sockets awaiting an accept() call from the application.

/usr/sbin/ndd -set /dev/tcp tcp_conn_req_max_q0 2048

The q0 queue contains half-open sockets.

C. Tru64 UNIX

/sbin/sysconfig -r socket sominconn=65535

The value of sominconn determines how many simultaneous incoming SYN packets can be handled by the system.

/sbin/sysconfig -r socket somaxconn=65535

The value of somaxconn sets the maximum number of pending TCP connections.

D. HP-UX

/usr/sbin/ndd -set tcp_syn_rcvd_max 1024
/usr/sbin/ndd -set tcp_conn_request_max 200

I know you , I was working in mumbai now transfered to Coimbatore. I was with sudheesh varma in RBI.

regards,
U.SivaKumar

Re: sendq size

Manoj P.U._1 — Wed, 23 Oct 2002 03:55:13 GMT

Hi

Shiju, Ethu message anu nokkendathu ?

Shiva, Now I got yoy and nice to meet you in this forum. How is your health??

Warm regards

Manoj

Re: sendq size

U.SivaKumar_2 — Wed, 23 Oct 2002 04:11:45 GMT

Hi,

My health is almost OK now. Thanks . Keep in touch. Convey my regards to all.

regards,
U.SivaKumar