Bandwidth Sharing Across Class Types; Figure 27: Rdm Admission Control Policy Example - Alcatel-Lucent 7450 Manual

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Diff-Serv TE LSP Class Type Change under Failure

Bandwidth Sharing Across Class Types

In order to allow different levels of booking of network links under normal operating conditions

and under failure conditions, it is necessary to allow sharing of bandwidth across class types.

This feature introduces the Russian-Doll Model (RDM) Diff-Serv TE admission control policy

described in RFC 4127, Russian Dolls Bandwidth Constraints Model for Diffserv-aware MPLS

Traffic Engineering. This mode is enabled using the following command:

config>router>rsvp>diffserv-te rdm.

The Russian Doll Model (RDM) LSP admission control policy allows bandwidth sharing across

Class Types (CTs). It provides a hierarchical model by which the reserved bandwidth of a CT is

the sum of the reserved bandwidths of the numerically equal and higher CTs.

CT2 has a bandwidth constraint BC2 which represents a percentage of the maximum reservable

link bandwidth. Both CT2 and CT1 can share BC1 which is the sum of the percentage of the

maximum reservable bandwidth values configured for CT2 and CT1 respectively. Finally, CT2,

CT1, and CT0 together can share BC0 which is the sum of the percentage of the maximum

reservable bandwidth values configured for CT2, CT1, and CT0 respectively. The maximum value

for BC0 is of course the maximum reservable link bandwidth.

What this means in practice is that CT0 LSPs can use up to BC0 in the absence of LSPs in CT1

and CT2. When this occurs and a CT2 LSP with a reservation less than or equal to BC2 requests

admission, it is only admitted by preempting one or more CT0 LSPs of lower holding priority than

this LSP setup priority. Otherwise, the reservation request for the CT2 LSP will be rejected.

7450 ESS MPLS Guide