Bandwidth Sharing Across Class Types; Figure 10: Rdm Admission Control Policy Example - Alcatel-Lucent 7950 SR User Configuration Manual

MPLS and RSVP

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+CT1
CT2
CT3 CT2+CT1+CT0
BC2
BC1
BC0

Figure 10: RDM Admission Control Policy Example

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.
7950 SR OS MPLS Configuration Guide Page 71