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RE: Is the advertisement (IGP) of available BW at each pre-emption le vel is a DS-TE- requirement ?
Francois, I don't think its that
simple.
1st, there is no relationship between a packets
up-state fowarding (QoS) requirements and its 'importance' (vis-a-vis its need
to survive over some other packet, in either the same or different DS
class)....DS classes simply do not give this information. For example,
using LDP and like-DS-class merging across VPN populations allows no
control over per VPN topology survivability. This is a problem
IMO.
2nd, largest BW packing of 'path entities' is the most
efficient way to do things if all path entities have the same survivability
attribute. I can imagine a case of large(r) L-LSP carrying BE traffic and
a small(er) E-LSP carrying VPN traffic.......if I have an availability SLA to
meet for the VPN LSP, then irrespective of the size of the BE LSP I ought to
restore the VPN traffic before I even consider the BE
traffic.
regards, Neil
Choudhury,
At 20:17 09/11/2001 -0500, Jim Boyle
wrote:
On Fri, 9 Nov 2001, Choudhury, Sanjaya
wrote:
>
Q3. In a DiffServ TE
domain, where the network administrator
>
initiates the creation
the TE tunnels (using MPLS-TE-MIB ),
>
when/how can he take
advantage of the following pre-emption
>
scheme:
>
a)
Preemption within the same DiffServ traffic class
>
b)
Preemption across different DiffServ traffic classes
I'm not sure how
people use the MPLS-TE-MIB to setup TE tunnels, so I
can't help you
there. I think you mean class-type above, so again, that
is a
specific proposal.
I am not sure I fully get the question
(in particular I don't see the relationship with the fact that you set up
tunnels using MIB or not), but let me quote some draft text from teh drafts
we're working on as it may help:
"
First, a Service Provider using
two Class-Types (one for Voice and one for Data), may elect to configure the
following to ensure that Voice LSPs are never driven away from their shortest
path because of Data LSPs:
-all
Voice LSPs to preemption priority 0
-all
Data LSPs to preemption priority 1
Another Service Provider may elect
to configure the following in order to optimize global network resource
utilization by favoring placement of large LSPs first:
- all
large size Voice LSPs to preemption priority 0
- all
large size Data LSPs to preemption priority 1
- all
small size Voice LSPs to preemption priority 2
- all
small size Data LSPs to preemption priority 3
"
Note that this is
based on the observation that, today, a common use for preemption is to give
higher preemption to large LSPs in order to get better global utilisation. You
get a much better network utilisation by fitting big things first and then
small ones (just like filling up the boot of the family car when going away on
holidays, really).
Hope that helps.
Francois
>
>
Thanks,
>
sanjay
>
>
_________________________________________________________
Francois Le Faucheur
Development Engineer, IOS Layer 3 Services
Cisco Systems
Office Phone: +33 4
97 23 26 19
Mobile
:
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+33 4 97 23 26 26
Email:
flefauch@cisco.com
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