The MPLS-OPS Archive

["Ashwin C. Prabhu" <Ashwinp@in.huawei.com>]

Title: RE: Traffic Engineering TLV

Dear Naidu

       The priority/premption is a task of MPLS Management module. I would like
       to know why the 8 priority levels are provided in the OSPF Extension? What
       i was thinking is this 8 priority levels is used by the CSPF for the computation
       of the routes. If so, why is it Unreservable Bandwidth for the 8 priority levels ?
       does it mean that on a link we configure the Bandwidth for different priority levels ?
       (Like Priority 0 -> 30 % bandwidth etc )
       Or this is ment for some other purpose ?
       As i found the draft draft-katz-yeung-ospf-traffic-04 not mentioning it clearly.
  

Regds
Ashwin

-----Original Message-----
From: Naidu, Venkata [mailto:Venkata.Naidu@Marconi.com]
Sent: Tuesday, August 14, 2001 7:37 PM
To: 'Ashwin C. Prabhu'; mpls@UU.NET; mpls-ops@mplsrc.com
Subject: FW: Traffic Engineering TLV

Prabhu:

->             Can anyone please tell me what are these 8
-> priority levels and what for these
->             used ?

  There are no set of semantics for each priority level.
  The different levels provide an ordering that can be
  used to determine preemption during the establishment
  of LSPs. They can also be used by an implementation
  as a means of ordering LSP computation and setup.

  How to use these priority levels? Look at:
  CR-LDP draft-ietf-mpls-cr-ldp-05.txt and
  RSVP-TE draft-ietf-mpls-rsvp-lsp-tunnel-08.txt

-> why we need this.

  The need for priority levels is specified in
  RFC 2702. There is a consensus of eight protocols
  being sufficient. 

  In Dan's terms...

  "The priority attribute defines the relative importance of traffic
   trunks.  If a constraint-based routing framework is used with MPLS,
   then priorities become very important because they can be used to
   determine the order in which path selection is done for traffic
   trunks at connection establishment and under fault scenarios.

   Priorities are also important in implementations  permitting
   preemption because they can be used to impose a partial order on the
   set of traffic trunks according to which preemptive policies can be
   actualized."

--Venkata Naidu