Multiprotocol Label Switching; Mpls Terminology - Cisco BPX-BXM-155-8DX Installation And Configuration Manual

Virtual Switch Interfaces
When a virtual switch interface (VSI) is activated on a port, trunk, or virtual trunk so that it can be used
by a master controller, such as a SES PNNI or an MPLS controller, the resources of the virtual interface
associated with the port, trunk or virtual trunk are made available to the VSI. These control planes can
be external or internal to the switch. The VSI provides a mechanism for networking applications to
control the switch and use a partition of the switch resources.
VSI was implemented first on the BPX 8650 in Release 9.1, which uses VSI to perform Multiprotocol
Label Switching. Release 9.1 allowed support for VSI on BXM cards and for partitioning BXM
resources between Automatic Routing Management (formerly called AutoRoute) and a VSI-MPLS
controller.
You can configure partition resources between Automatic Routing Management PVCs and one VSI
control plane, but not both. You can also configure partition resources between Automatic Routing
Management PVCs and three VSI controllers (MPLS or PNNI).
VSI on the BPX provides:
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Multiprotocol Label Switching

Label switching enables routers at the edge of a network to apply simple labels to packets (frames), allowing
devices in the network core to switch packets according to these labels with minimal lookup activity. Label
switching in the network core can be performed by switches, such as ATM switches, or by existing routers.
Multiprotocol Label Switching (MPLS, previously called Tag Switching) integrates virtual circuit switching
with IP routing to offer scalable IP networks over ATM. MPLS support data, voice, and multimedia service
over ATM networks. MPLS summarizes routing decisions so that switches can perform IP forwarding, as
well as bringing other benefits that apply even when label switching is used in router-only networks.
Using MPLS techniques, it is possible to set up explicit routes for data flows that are constrained by
path, resource availability, and requested Quality of Service (QoS). MPLS also facilitates highly
scalable Virtual Private Networks.
MPLS assigns labels to IP flows, placing them in the IP frames. The frames can then be transported
across packet or cell-based networks and switched on the labels rather than being routed using IP
address look-up.
A routing protocol such as OSPF, uses the Label Distribution Protocol (LDP) to set up MPLS virtual
connections (VCs) on the switch.

MPLS Terminology

MPLS is a standardized version of Cisco's original Tag Switching proposal. MPLS and Tag Switching
are identical in principle and nearly so in operation. MPLS terminology has replaced obsolete Tag
Switching terminology.
An exception to the terminology is Tag Distribution Protocol (TDP). TDP and the MPLS Label
Distribution Protocol (LDP) are nearly identical, but use different message formats and procedures.
TDP is used in this design guide only when it is important to distinguish TDP from LDP. Otherwise,
any reference to LDP in this design guide also applies to TDP.
Cisco BPX 8600 Series Installation and Configuration
23-2
Class of service templates
Virtual trunks support for VSI
Support for VSI master redundancy
Multiple VSI partitions
SV+ support for VSI
Chapter 23 Configuring BXM Virtual Switch Interfaces
Release 9.3.0, Part Number 78-10674-01 Rev. D0, July 2001