Source Quench

[Mr. R. Astles]

We have noticed that one of our servers is sending out source quench signals and we suspect that this may be related to a performance issue that we have. This server is primarily a NFS server.

Is there a command that shows how many or how freqently this machine is sending these signals.

Is there a setting that I can modify to make it stop.

Is there a limit to the file size or amount of data that can be handled via NFS.

Am I barking up the wrong tree and worrying needlessly about source quench

[Vijeesh CTK]

try this command

ndd -set /dev/ip ip_send_source_quench 0

CTK

[hpuxrox]

ndd -set /dev/ip ip_send_source_quench 0

[MANOJ SRIVASTAVA]

Hi Mr Astles


this is a know problem in HPUX 11.00
Here is waht you can do on the fly :
ndd -set /dev/ip ip_send_source_quench 0

also set it up in the /etc/rc.config.d/nddconf to make it permanent , here is waht HP says:
This problem has been identified and is addressed in SR 5003435396.
This problem will be fixed in the 11.01 version of the HP-UX operating
system. These messages can be safely ignored as they have absolutely no
impact on the operating system (performance or otherwise). Alternatively
these messages can be prevented by disabling source quench. For more
information see the sections below.

What is causing these messages?

At 11.0 the Streams Xport layer now passes the ICMP echo request to any
other process that has a socket open and bound to raw IP. The rpcd
rpcd/dced deamon opens a raw socket to listen to ICMP messages. This raw
socket is open by icmp_monitor routine of rpcd. The main function of
this routine is to check for error messages from DCE servers registered
in endpoint database of the host and it checks the socket every 5
minutes. It does not respond to or use the ICMP echo requests; however,
the socket queue becomes filled during the 5-minute delay causing the
source quench message. The fix being implemented in 11.01 will be to
increase the buffer size to 128 K and shorten the wait interval from 5
minutes to 2 minutes, thereby flushing the queue of these unwanted
messages before the queue becomes filled.

Why is it safe to ignore these messages or to turn them off?

A good disscussion of this is in TCPIP Illustrated Volume 1,
by Richard Stevens, pages 160-162.Here is an excerpt from page 161:

Although RFC 1009 [Braden and Postal 1987] requires a
router to generate source quenches when it runs out of
buffers, the new router requirements RFC [Almquist 1993]
changes this and says that a router must not originate
source quench errors. The current feeling is to deprecate
the source quench error, since it consumes network bandwidth
and is an ineffective and unfair fix for congestion.

Also, see RFC 1812, section 4.3.3.3 Source Quench for a good
discussion of the issues.

Also RFC 2001 has discussion on Congestion and why TCP should handle
this not ICMP:

Congestion avoidance and slow start are independent
algorithms with different objectives. But when congestion
occurs, TCP must slow down its transmission rate of packets
into the network and then invoke slow start to get things
going again. In practice, they are implemented together.

Exactly how do I disable source quench?

You can disable source quench in HP-UX 11.0 by executing this command:

ndd -set /dev/ip ip_send_source_quench 0

To disable Source Quench so that it can survive a reboot,

modify the /etc/rc.config.d/nddconf file as follows :
TRANSPORT_NAME[X]=ip
NDD_NAME[X]=ip_send_source_quench
NDD_VALUE[X]=0

Where X is the next logical numerical sequence in a table
of values, with X starting at 0.
--------------------------------------------------

DCE patch and dependencies:

3 PHCO_23651 fsck_vxfs(1M) cumulative patch
2 PHCO_23876 cumulative SAM/ObAM patch
1 PHCO_25883 cumulative 10.20 libc compatibility support
3 PHKL_18543 PM/VM/UFS/async/scsi/io/DMAPI/JFS/perf patch
3 PHKL_20016 2nd CPU not recognized in G70/H70/I70
3 PHKL_23956 Profile, virtual timers and disabling fix
3 PHKL_24027 VxFS 3.1 cumulative patch
1 PHKL_25906 Probe,IDDS,PM,VM,PA-8700,asyncio,T600,FS
1 PHKL_25999 syscall, msem_lock, umask cumulative patch
2 PHSS_21614 HP DCE/9000 1.7 Runtime cumulative patch


All the best


Manoj Srivastava

[Sachin Patel]

If you serach for source quench you will find number of threads.

Little facts about this message. I found this log time ago from here in forums.

This message is result of ping only. It is just a warning message that ICMP request that source has received is too fast and it is not able to response back. so it tells ping server to slow down. This will help to prevent their buffer from overflowing. As we can see from following figure it send this warning message only when network traffic is very very high. As you can see on second figure it starts working when you have less network traffic.

you can suppress this message very easily. And it will even improve our performance because you are getting rid of that traffic from network. Only problem is when ICMP request fails it will don't know when to stop. you can disable this error message on fly using comment listed above.

Sachin

[Clemens van Everdingen]

Hi,

Searched my old answers !

See this thread:

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x73afba808b46d611abda0090277a778c,00.html

Regards,
C.

[nancy rippey]

You may also wish to install patch PHSS_21614. It resolves a source quench issue within HPUX 11.0
http://us-support2.external.hp.com/wpsl/bin/doc.pl/screen=wpslDisplayPatch/sid=5837731c06d141ac2b

nancy