Subject: [ippm] TWAMP questions

From: "Murtaza Chiba (mchiba)" <[email-masked]>
Date: Tue, 6 May 2008 09:32:57 -0700

Hi,
    A couple of more questions.
 
*) TWAMP does not exchange schedule slots and hence it is not known to
the Session Reflector as to how long a port needs to be left open for a
given test session.   I recommend adding a Session-Period to be sent in
a Request-Session message to compliment the Start-Time field.
 
*) TWAMP defines adding DSCP marking to the Test Session stream.   Does
the draft expect that the end systems will provide the correct queueing,
shaping and policing for the marked packet or is that purely for network
treatment?   The packets could originate and terminate on switches that
work on layer two CoS markings and could ignore the layer 3 DSCP.

-Murtaza
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---

From: "Walt Steverson" <[email-masked]>
Date: Fri, 9 May 2008 22:42:06 -0500

I agree with the need for something like the Session-Period field.
On Tue, May 6, 2008 at 11:32 AM, Murtaza Chiba (mchiba) <[email-masked]>
wrote:

> *) TWAMP does not exchange schedule slots and hence it is not known to the
> Session Reflector as to how long a port needs to be left open for a given
> test session.   I recommend adding a Session-Period to be sent in a
> Request-Session message to compliment the Start-Time field.
>
> *) TWAMP defines adding DSCP marking to the Test Session stream.   Does the
> draft expect that the end systems will provide the correct queueing, shaping
> and policing for the marked packet or is that purely for network
> treatment?   The packets could originate and terminate on switches that work
> on layer two CoS markings and could ignore the layer 3 DSCP.
>
>
> -Murtaza
>

---

From: "Murtaza Chiba (mchiba)" <[email-masked]>
Date: Mon, 12 May 2008 15:37:54 -0700

Another question we have is:
 
- What fields form a key to uniquely identify test streams?
 
  Is it Sender-Address + Sender-Port + Receiver-Address + Receiver-Port?
Should DSCP be used as well?   I guess this is an implementation
decision, but is significant since in the encrypted mode the decryption
keys will need to be identified based on the test stream packet
received.

Thanks,
-Murtaza

________________________________

	From: Walt Steverson [mailto:[email-masked]] 
	Sent: Friday, May 09, 2008 8:42 PM
	To: Murtaza Chiba (mchiba)
	Cc: IETF IPPM WG
	Subject: Re: [ippm] TWAMP questions

	I agree with the need for something like the Session-Period
field. 

	On Tue, May 6, 2008 at 11:32 AM, Murtaza Chiba (mchiba)
<[email-masked]> wrote:

		Hi,
		 
		*) TWAMP does not exchange schedule slots and hence it
is not known to the Session Reflector as to how long a port needs to be
left open for a given test session.   I recommend adding a
Session-Period to be sent in a Request-Session message to compliment the
Start-Time field.
		 
		*) TWAMP defines adding DSCP marking to the Test Session
stream.   Does the draft expect that the end systems will provide the
correct queueing, shaping and policing for the marked packet or is that
purely for network treatment?   The packets could originate and
terminate on switches that work on layer two CoS markings and could
ignore the layer 3 DSCP.

		-Murtaza

---

From: Al Morton <[email-masked]>
Date: Tue, 13 May 2008 12:49:49 -0400

At 11:42 PM 5/9/2008, Walt Steverson wrote:

I agree with the need for
something like the Session-Period field.

<[email-masked]>
wrote:

Hi,

A couple of more
questions.

*) TWAMP does not exchange
schedule slots and hence it is not known to the Session Reflector as to
how long a port needs to be left open for a given test
session.   I recommend adding a Session-Period to be sent in a
Request-Session message to compliment the Start-Time
field.

We could also handle apparent failures by allowing the Server and

Session Reflector to time-out and free-up resources after a

period on zero activity.  Since adding this behavior requires

no message changes, it's easier and less disruptive right now...

*) TWAMP defines adding DSCP
marking to the Test Session stream.   Does the draft expect
that the end systems will provide the correct queueing, shaping and
policing for the marked packet or is that purely for network
treatment?   The packets could originate and terminate on
switches that work on layer two CoS markings and could ignore the layer 3
DSCP.

-Murtaza

If TWAMP is embedded in a router or a switch, the TWAMP spec

only covers the TWAMP functions.  Other configurations cover

the treatment of DSCP, if any.

revised text is on the way...

Al

---

From: Al Morton <[email-masked]>
Date: Tue, 13 May 2008 12:59:26 -0400

At 06:37 PM 5/12/2008, Murtaza Chiba (mchiba) wrote:

Another question we
have is:

- What fields form a
key to uniquely identify test streams?

Is it
Sender-Address + Sender-Port + Receiver-Address +
Receiver-Port?   Should DSCP be used as well?   I
guess this is an implementation decision, but is significant since in the
encrypted mode the decryption keys will need to be identified based on
the test stream packet received.

This does seem to be an implementation detail.

I imagine that at least one of the ports needs to change

for each test session.

Al

---

From: "Murtaza Chiba (mchiba)" <[email-masked]>
Date: Tue, 13 May 2008 12:03:38 -0700

Hi All,
    One response at MSC>

	From: Al Morton [mailto:[email-masked]] 
	Sent: Tuesday, May 13, 2008 9:50 AM
	To: Walt Steverson; Murtaza Chiba (mchiba)
	Cc: IETF IPPM WG
	Subject: Re: [ippm] TWAMP questions

		I agree with the need for something like the
Session-Period field.
		On Tue, May 6, 2008 at 11:32 AM, Murtaza Chiba (mchiba)
<[email-masked]> wrote:

			Hi,

			  
			*) TWAMP does not exchange schedule slots and
hence it is not known to the Session Reflector as to how long a port
needs to be left open for a given test session.   I recommend adding a
Session-Period to be sent in a Request-Session message to compliment the
Start-Time field.

	We could also handle apparent failures by allowing the Server
and 
	Session Reflector to time-out and free-up resources after a 
	period on zero activity.  Since adding this behavior requires
	no message changes, it's easier and less disruptive right now...
	 
	MSC> Failure is one aspect, the other thing to consider is that
for a given Connection, Test A may run for 3 days while Test B may run
for just one day.   Since the Stop-All message for graceful termination
comes on Day 3, Test B port will accept test streams for 2 additional
days.   The other thing is how would one define zero activity?   The
Server has no knowledge when a Stop message should arrive!
	 
	-Murtaza 

			  
			*) TWAMP defines adding DSCP marking to the Test
Session stream.   Does the draft expect that the end systems will
provide the correct queueing, shaping and policing for the marked packet
or is that purely for network treatment?   The packets could originate
and terminate on switches that work on layer two CoS markings and could
ignore the layer 3 DSCP. 
			
			-Murtaza

---

From: Al Morton <[email-masked]>
Date: Tue, 13 May 2008 15:29:58 -0400

At 03:03 PM 5/13/2008, Murtaza Chiba (mchiba) wrote:

(Al wrote)

MSC> Failure is one aspect, the other thing to consider is that for a
given Connection, Test A may run for 3 days while Test B may run for just
one day.   Since the Stop-All message for graceful termination
comes on Day 3, Test B port will accept test streams for 2 additional
days.

(Al) If this is a big deal for some specific application,

I would suggest setting up two control connections (for now),

and extend the commands to start/stop individual sessions

in future.

The other thing is
how would one define zero activity?   The Server has no
knowledge when a Stop message should arrive!

I suggest a wording like this:

...The Session-Reflector MAY

discontinue any session which has been Started when no packet

associated with that session has been received for REFWAIT
seconds.

The default value of REFWAIT SHALL be 900 seconds, and this
waiting

time MAY be configurable.

This applies on a single session basis, which seems to be

something you want...

Al