some question about"Source quench",help me please,can you?

[manner]

I have a HP 9000N4000.It have a 100 network Adapter ,I config it two IP address .One IP address is 10.236.0.2 and another is 10.236.0.4 and it was the resource of MC Service Guide.when I ping 10.236.0.4 ,sometimes it reply me "Source quench",and sometimes it is normal.Can you help me to answer this question! Thank you very much!

[eran maor]

| 3.2.2.3 Source Quench: RFC-792
|
| A host MAY send a Source Quench message if it is
| approaching, or has reached, the point at which it is forced
| to discard incoming datagrams due to a shortage of
| reassembly buffers or other resources. See Section 2.2.3 of
| [INTRO:2] for suggestions on when to send Source Quench.

[INTRO:2] is RFC1009 - Requirements for Internet Gateways - and
it says:

| 2.2.3. Source Quench
|
| All gateways must contain code for sending ICMP Source Quench
| messages when they are forced to drop IP datagrams due to
| congestion. Although the Source Quench mechanism is known to
| be an imperfect means for Internet congestion control, and
| research towards more effective means is in progress, Source
| Quench is considered to be too valuable to omit from production
| gateways.

From these, you can notice Source Quench is not MUST item.
And internet hosts can choose whether or not it will be generated.

At 11.0, its implementation has dramatically changed from 10.X.
When it receives ICMP ECHO packets, they are all sent upstreams
to any application which opens SOCK_RAW socket. And if some of
those program's socket buffer gets full just because the program
can not read those ICMP ECHO packets in timely manner, ICMP
SOURCE QUENCH is generated.

The above behaviour is specific one to 11.0 and can not be seen
on 10.X.

Then, who's opening SOCK_RAW socket on 11.0 ? It's rpcd daemon.
rpcd is looking after DCE RPC request. Software Distributor package
like swinstall, swcopy and swlist uses DCE RPC and those commands
relies on rpcd daemon. The old version of rpcd is not reading
received data from its SOCK_RAW socket so frequently and its buffer
can get full if many ICMP ECHO packet is received. With the DCE
runtime patch, [PHSS_17810/PACHRDME/English] , the way of reading the data from its
RAW_SOCK socket was improved (See CR: CHFts24522). This may be able
to stop the source quench from being generated. However, you have
to know that it may still happen even with this DCE patch. If the
rate of ICMP ECHO packets received is too high, the same symptom
can happen sooner or later.

To eliminate it completely, you must change ndd parameter to disable
source quench by:

# ndd -set /dev/ip ip_send_source_quench 0

To set this parameter permanently over reboot, you have to set
this option in /etc/rc.config.d/nddconf.

There have been lots of questions here:

" Is there any bad side effect from this change ? "

The answer is NO. ICMP source quench is not generated at 10.X
and there is no problems reported with this behaviour. And as you
can notice in the RFCs above, ICMP souce quench is the feature of
"MAY". Hosts just "may" send it.

Further, SOCK_RAW socket interface is not supported and it's used
to implement other products like ping command and SD package.
Therefore, there's no chance to have 3rd party application which
uses SOCK_RAW. This means disabling it can not affect any 3rd
party application's behaviour

[Kofi ARTHIABAH]

Hi GS:

This question has been answered in the forums previously- check this thread:

http://forums.itrc.hp.com/cm/QuestionAnswer/1,1150,0x28d0f841489fd4118fef0090279cd0f9,00.html

Alex describes what you have to do to prevent these messages.

BTW you can also do a search (top left of your screen) and type "source quench" in the search field for other threads that discuss the topic.

Good luck.

[John Poff]

Your source quench error is caused by ICMP getting too busy to respond to all the requests it is getting. It sends out a "source quench" message telling the other ends to stop for a minute. It is an inefficient method of flow control, and you can turn it off. We did it at our site to appease our network guys.

The way to turn it off in HP is to use the ndd command. Type this command as root to see if it is indeed turned on:

ndd -get /dev/ip ip_send_source_quench

If it returns a 1, it is turned on. To turn it off, try this:

ndd -set /dev/ip ip_send_source_quench 0

Try that and see if it stops your source quench errors. To turn it off permanently, you will need to edit your /etc/rc.config.d/nddconf file. Add these lines to it:

TRANSPORT_NAME[0]=ip
NDD_NAME[0]=ip_send_source_quench
NDD_VALUE[0]=0

Good luck!