HP HSR6800 Configuration Manual page 56

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Bandwidth Constraint (BC)—Restricts the bandwidth for one or more class types.
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Bandwidth constraint model—Algorithm for implementing bandwidth constraints on different
CTs. A BC model comprises two factors, the maximum number of Bandwidth Constraints
(MaxBC) and the mappings between BCs and CTs. DS-TE supports two BC models, Russian
Dolls Model (RDM) and Maximum Allocation Model (MAM).
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TE class—A pair consisting of a CT and a preemption priority for the CT. The setup priority or
holding priority of an LSP transporting a traffic trunk from that CT must be the preemption
priority for the CT.
Note the following about the DS-TE modes:
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The prestandard mode supports two CTs (CT 0 and CT 1), eight priorities, and up to 16 TE
classes. The IETF mode supports four CTs (CT 0 through CT 3), eight priorities, and up to eight
TE classes.
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The prestandard mode supports only RDM. The IETF mode supports both RDM and MAM.
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The prestandard mode is proprietary, and therefore a device operating in prestandard mode
cannot communicate with devices of some other vendors. The IETF mode is a standard mode
implemented according to relative RFCs. A device operating in IETF mode can communicate
with devices of other vendors.
How DS-TE operates
A device takes the following steps to establish MPLS TE tunnels according to CTs of traffic trunks:
1. Determines the CT of traffic flows.
A device classifies traffic flows according to your configuration:
When configuring a dynamic MPLS TE tunnel, you can use the mpls te bandwidth command on the
tunnel interface to specify a CT for the traffic flows to be forwarded by the tunnel.
When configuring a static MPLS TE tunnel, you can use the bandwidth keyword to specify a CT for the
traffic flows to be forwarded along the tunnel.
2. Checks whether bandwidth is enough for the CT.
You can use the mpls te max-reservable-bandwidth command on an MPLS TE tunnel
interface to configure the bandwidth constraints of the tunnel interface. The device determines
whether bandwidth is enough to establish an MPLS TE tunnel for a traffic trunk according to the
traffic trunk's CT and the tunnel interface's BCs.
The relation between BCs and CTs varies in different BC models:
In RDM model, a BC constrains the total bandwidth of multiple CTs, as shown in
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BC 2 is for CT 2. The total bandwidth of the traffic of CT 2 cannot exceed BC 2.
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BC 1 is for CT 2 and CT 1. The total bandwidth of the traffic of CT 2 and CT 1 cannot exceed BC
1.
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BC 0 is for CT 2, CT 1, and CT 0. The total bandwidth of the traffic of CT 2, CT 1, and CT 0
cannot exceed BC 0. In this model, BC 0 equals the maximum reservable bandwidth of the
tunnel.
In cooperation with priority preemption, the RDM model can also implement the isolation across CTs,
ensuring each CT its share of bandwidth. RDM is suitable for networks where traffic is unstable and
traffic bursts might occur.
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Figure 20: