The MPLS WG Archive

["Daniel N. Bauer" <dnb@zurich.ibm.com>]

Shahram Davari wrote:
> 
> Hi Daneil,
> 
> With all due respect, I don't think that your mentioned approach will work efficiently. First of all it is not reasonable to expect all routers to have exactly the same BW assignment per PHB. Secondly, it is also not reasonable to expect an E-LSP to carry traffic in proportion to their PHB assignments in the routers.
> 
> My understanding of using the E-LSP aggregate BW for admission control is as follows:
> 
> During an E-LSP setup, the aggregate BW of all supported PHBs is signaled. If all the routers in the path, have sufficient BW, the E-LSP is admitted. Now at the ingress to this E-LSP, the ingress router could do a separate admission control for each supported BA that is using the mentioned E-LSP (note this is independent of the E-LSP admission control). In other words there are two phases to the admission control, one for the whole E-LSP and another one for the traffic that is going to use that E-LSP. This is very similar to the Aggregate RSVP admission control (check ISSL WG for more information).
> 
> Regards,
> -Shahram

Hello Shahram,

maybe my assumptions are a little bit far-fetched. Still, your
solution does not (yet?) convince me, either.
In your proposal, the following points are not quite clear to me:

1.) How does the "admission control for each supported BA" work?
    How does the ingress LSR split up the aggregated BW request into
    a BW request for each BA? What is the rational to do admission
    control for the BAs only at the edge?
    I don't find this very similar to the Aggregate RSVP admission control.
    There, the requirement of each flow is known before the flows are aggregated.
    This is not the case for E-LPSs.

2.) If admission control for E-LSPs is only based on the aggregate bandwidth,
    it becomes difficult to do a reliable admission control for L-LSPs. For L-LSP
    admission control, the LSRs need to know the unreserved bandwidth per OA.
    How is it possible to do book-keeping for unreserved bandwidth, if E-LSPs
    are admitted on the aggregate?

Maybe a solution is to extend the signaling and include optionally the
BW requirements per OA for E-LSPs.

Regards,
-Daniel