Subject: [NSIS] Statefully aware NSLP router sending error messages?

From: "James M. Polk" <[email-masked]>
Date: Wed, 07 Sep 2005 16:34:41 -0500

Hey

When a statefully aware NSLP router experiences an error (I think this is a 
QNE router), does it send the same error message in both directions, or 
only one, or is it different error in each direction?

Take a preemption event at a router (say router5) between endpoints Alice 
and Bob. Alice (sender) initiated the bi-directional reservation that was 
exstablished. (BTW - does any of this error messaging change depending on 
who initiated the reservation?)

Router 5 in the middle of the network experienced something that causes it 
to preempt the reservation between Alice and Bob. (BTW - are both 
directions preempted at the same time?)

The NOTIFY message with Transient error 0x04000005 is sent to Alice by 
Router 5. (BTW - I'm looking to be corrected anywhere along the way here)

Is a NOTIFY message with Transient error 0x04000005 sent to Bob at the same 
time?

Is another message from Router 5 sent to Bob at this same time?

If Bob doesn't get sent a NOTIFY with this preemption indication error, is 
Alice expected to send something to Bob to tell him one of the reservations 
between the two endpoints was preempted (like something at the SIP layer)?

The ERROR_SPEC has an Error Source Identifier field , and an optional Error 
Specific Information field - but where does it get described to Alice (who 
received this NOTIFY message from Router 5) that this NOTIFY is for the 
'Alice to Bob' direction, and *not* the 'Bob to Alice' direction? Does the 
BOUND_SESSION_ID affect this universally, even in error conditions, or is 
this concept only for individual reservations bound to aggregates? Is each 
router supposed to maintain state for each bound session (master to the 
slaves)? In the case of aggregates, this makes some sense, but I'm more 
curious about directionality with this inquiry. Section 3.2.7 seems 
inconsistent with its text, but I'll put that in another message to the list.

I can see a usecase where this L7 session could want to stay up even though 
one direction could be set to best-effort.

Or am I totally wet behind the ears about NSIS in which all reservations 
are always ultimately established in both directions regardless of which 
endpoint initiated the signaling and that there cannot be a one-way 
reservation? I do know multicast was canned.... (BTW - what happens when 
reservations traverse different routes, therefore many different routers - 
preventing a binding? How is this handled and can the reservations be 
prevented from establishment unless they take the same path?)

Which ID talks about any of this?

I'm focusing on the NSLP-07 ID, but should I be focusing more on the GIMPS 
ID for now to learn the basics?

cheers,
James

                                 *******************
                 Truth is not to be argued... it is to be presented.

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