The MPLS WG Archive

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

Title: RE: Traffic Engineering TLV

Dear Naidu

 I couldn't find the draft-kompella-tewg-bw-acct-00.txt draft can you please
 tell me where can i get this draft ?

Thanks & regds
Ashwin

-----Original Message-----
From: Naidu, Venkata [mailto:Venkata.Naidu@Marconi.com]
Sent: Thursday, August 16, 2001 7:12 PM
To: 'Ashwin C. Prabhu'; Naidu, Venkata; mpls@UU.NET; mpls-ops@mplsrc.com
Subject: FW: Traffic Engineering TLV

Ashwin:

   Please look at my inline comments...

-> The priority/preemption is a task of MPLS Management
-> module. I would like to know why the 8 priority levels
-> are provided in the OSPF Extension?

   OSPF (for that matter any IGP) job is to flood the TE
   information throughout the area (at present) for TE
   purpose. The 8 priority levels for unreserved bw is
   nothing to do with OSPF calculations. Just flood the info!

-> 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 ?

   Yes! After flooding the TE information, ingress LERs do
   CSPF to prune links (which are not met the requested
   bw, priority, preemption etc) to find the best path to egress.

-> 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 ?

   It is not that simple, please look at Kompella's paper
   draft-kompella-tewg-bw-acct-00.txt (and nested references)

->        As i found the draft draft-katz-yeung-ospf-traffic-04
-> not mentioning it clearly.

   As I said, draft-katz-yeung-ospf-traffic-04 is nothing to do
   with configuration of priority levels.

--Venkata Naidu

-> -----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
->