Subject: [ippm] twamp-control keepalive

From: "Walt Steverson" <[email-masked]>
Date: Tue, 22 Apr 2008 15:24:42 -0500

Is there some way for TWAMP Server to detect when a Control-Client abruptly
disappears (eg. somebody tripped over the power or ethernet cable)?  The
only mechanism I can see is that if TCP keepalives are enabled then they
could eventually inform the Server that the socket is no longer open.  The
default timeout value for the SO_KEEPALIVE option on many systems seems to
be ~2 hours (
http://unlser1.unl.csi.cuny.edu/faqs/sock-faq/html/unix-socket-faq-2.html#peer_death)
which is a long time for the connection to hang around consuming resources.
Adjusting the TCP keepalive timeout affects all TCP connections on many
systems.  If the TWAMP control protocol included a keepalive message this
long delay could be significantly shortened without impacting other TCP
connections on the system.  The TWAMP Server seems especially vulnerable
after the Start-Ack message is sent to the Control-Client and before the
Control-Client sends the Stop-Sessions message.
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From: Al Morton <[email-masked]>
Date: Wed, 23 Apr 2008 09:32:36 -0400

Interesting, sounds like a new TWAMP Control-Command Number

would be needed for this.  Suggest we think about it for

draft-morton-more-twamp-*

Does anyone else see a need for this feature?

Al

At 04:24 PM 4/22/2008, Walt Steverson wrote:

Is there some way for TWAMP
Server to detect when a Control-Client abruptly disappears (eg. somebody
tripped over the power or ethernet cable)?  The only mechanism I can
see is that if TCP keepalives are enabled then they could eventually
inform the Server that the socket is no longer open.  The default
timeout value for the SO_KEEPALIVE option on many systems seems to be ~2
hours
(
http://unlser1.unl.csi.cuny.edu/faqs/sock-faq/html/unix-socket-faq-2.html#peer_death
) which is a long time for the connection to hang around consuming
resources.  Adjusting the TCP keepalive timeout affects all TCP
connections on many systems.  If the TWAMP control protocol included
a keepalive message this long delay could be significantly shortened
without impacting other TCP connections on the system.  The TWAMP
Server seems especially vulnerable after the Start-Ack message is sent to
the Control-Client and before the Control-Client sends the Stop-Sessions
message.