The MPLS WG Archive

["Thomas D. Nadeau" <tnadeau@cisco.com>]

         Sorry for the delay. I was traveling last week.

>I am re-sending a few questions I had on the TE MIB again (as I did not get
>any response the first time around). I would appreciate any helpful
>response.
>I tried searching the archives for an answer but I could not find anything
>relevant to the specific questions I've raised.
>
>Thanks
>-patrick.
>
>-----Original Message-----
>From: Dominic-Savio, Patrick
>Sent: Monday, February 04, 2002 10:53 AM
>To: 'mpls@uu.net'
>Subject: Question on Resource Sharing w.r.t mpls-te-mib-08
>
>
>Hi,
>The description for mplsTunnelResourcePointer indicates that 2 or more
>segments can share resources if the user specifies the same value for this
>object for different tunnels.
>
>The description for mplsTunnelSessionAttributes:mergingPermitted indicates
>that this is used for reducing resource overhead on downstream transit
>routers.
>
>I'm a bit confused about how these two parameters are related (if they are
>indeed related).
>First off I'm assuming that mplsTunnelSessionAttributes:mergingPermitted
>corresponds to the "SE Style desired" flag of the RSVP Session Attribute
>Object [RFC3209] when RSVP is used for signalling. If this is the case then
>this bit does not (quote from TE MIB:) "permit transit routers to merge this
>session..." it is
>only an indication to the egress LSR requesting SE style of reservation.
>In any case could you confirm that the
>mplsTunnelSessionAttributes:mergingPermitted value does correspond to the
>"SE Style desired" flag in RSVP.

         When using RSVP for signaling, I believe that is correct.

>If my above assumption is correct then (again with RSVP), say the user sets
>up a couple of tunnel instances and requests SE style reservation (using the
>mergingPermitted flag) for them. Now, if the egress LSR honors the request
>and responds with a SE STYLE reservation, shouldn't the ingress LSR (along
>with the transit LSRs) share resources between these two instances ?.
>So, receiving of an SE STYLE reservation by itself should indicate to the
>ingress LSR that resources should be shared. What then is the purpose of
>indication of resource sharing by specifying the same value of
>mplsTunnelResourcePointer on the ingress LSR?, this appears to be redundant.

         The bit on the tunnel indicates that sharing is permitted, but the
resource pointer allows you to specify which tunnels to share resources with
(as opposed to any tunnels with resource sharing bit enabled). For example, if
you wanted a bi-directional pair of tunnels to share resources together, 
but not
with other tunnels, you could specify that configuration this way.

         --Tom




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