The MPLS WG Archive

["Balaji, Hemanth" <hbalaji@riverstonenet.com>]

Hi,

Please Excuse me. There still seemed to have been some alignment
problem. 

-Hemanth.

-----Original Message-----
From: mpls-bounces@lists.ietf.org [mailto:mpls-bounces@lists.ietf.org]
On Behalf Of Balaji, Hemanth
Sent: Tuesday, June 21, 2005 11:03 AM
To: Adrian Farrel; George Swallow; mpls@ietf.org
Subject: RE: [mpls] One week last-last call on Soft Preemption



Hi,

 Can anyone explain, how the following situation is handled ( be it
needed to ) by the soft-preemption draft.



         
Topology:

                   +---------------- R2
                   |
R0 --------------- R1
                   |
                   +---------------- R4
Reservable link Bandwidth( BW)  for all links = 1000


LSP1 :

R0 ----------------- R1 ---------------- R4

BW = 500
Priority(Hold): 7




LSP2 :

R2 ----------------- R1 ---------------- R4

BW = 600
Priority(Setup): 6

1) Initially LSP1 is UP. Soft preemption desired flag is set.

2) Now R1 gets a new resquest for LSP2. ( which requires LSP1 to be
preempted, softpreempted in this case)

3) Let us assume the following situation.

   > Before R1 notifies R0 about the preemption.
   > R0 changes its BW Req to 400 and sends out its first new path
     message.
   > The first Resv msg from R1 that R0 receives has (will have-due to 
     step 2) the preemption pending flag set.
   

Now, what will the behavior be in this case, will this situation make
any difference?

Ideally, R0 should not attempt a make before break and look for an
allternate path, since the new BW requirement ( 400(7) + 600(6) )
can be satisfied along the same path ( R0-R1-R4).


Regards,
Hemanth.










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