Private Network To Network Interface (Pnni) - Cisco BPX-BXM-155-8DX Installation And Configuration Manual

Chapter 1 The BPX Switch: Functional Overview
BPX Switch Operation
With Label Switching the complete analysis of the Layer 3 header is performed only once: at the edge
label switch router (LSR) which is located at each edge of the network. At this location, the Layer 3
header is mapped into a fixed length label, called a label.
At each router across the network, only the label need be examined in the incoming cell or packet in
order to send the cell or packet on its way across the network. At the other end of the network, an edge
LSR swaps the label out for the appropriate header data linked to that label.
A key result of this arrangement is that forwarding decisions based on some or all of these different
sources of information can be achieved by means of a single table lookup from a fixed-length label. For
this reason, label switching makes it feasible for routers and switches to make forwarding decisions
based upon multiple destination addresses.
Label switching integrates switching and routing functions, combining the reachability information
provided by the router function, plus the traffic engineering benefits achieved by the optimizing
capabilities of switches.
For multiservice networks, the BPX 8650 switch provides ATM, Frame Relay, and IP Internet service
all on a single platform in a highly scalable way. Support of all these services on a common platform
provides operational cost savings and simplifies provisioning for multiservice providers.
Cisco's MPLS solution is described in detail in the Cisco MPLS Controller Software Configuration
Guide.

Private Network to Network Interface (PNNI)

Private Network to Network Interface (PNNI) is a link-state routing protocol that provides
standards-based dynamic ATM routing with QoS support as defined by the ATM Forum. PNNI supports
aggregation for private ATM addresses and links between switches, and can scale the network and its
performance by configuring PNNI peer groups and hierarchical levels.
A key feature of the PNNI hierarchy mechanism is its ability to automatically configure itself in
networks in which the address structure reflects the topology. It is responsive to changes in network
resources and availability.
PNNI is available on the BPX switch when an optional Cisco Service Expansion Shelf (SES) PNNI is
installed. This controller is connected locally to a BPX 8600 series switch to provide PNNI signaling
and routing for the establishment of ATM and Frame Relay switched virtual circuits (SVCs) and Soft
Permanent Virtual Circuits (SPVCs) over a BPX 8600 wide area network. The network created with
BPX SES PNNI nodes also supports traditional ATM and Frame Relay permanent virtual circuits
(PVCs) in a separately partitioned AutoRoute network.
ATM SVCs are ATM connections that are established and maintained by a standardized signaling
mechanism between ATM CPE (ATM end systems) across a Cisco WAN switching network. ATM
SVCs are set up in accordance with user demand and removed when calls are completed, thus freeing
up network resources.
BPX SES PNNI node resources, such as port virtual path identifier (VPI) range and bandwidth and
trunk bandwidth, are partitioned between SVCs/SVPCs and PVCs. Resource partitioning provides a
firewall between PVCs and SVCs/SVPs so that problems with CPE or large bursts do not affect the
robustness and availability of PVC services. Bursty data for either PVCs or SVCs/SPVCs can always
use any unused link bandwidth, regardless of partitioning.
For a brief description of the SES PNNI, see Service Expansion Shelf PNNI, page 2-8. Refer to the
Cisco SES PNNI Controller Software Configuration Guide for detailed information abut the SES.
For further information about PNNI and the SES, refer to the Cisco SES PNNI Controller Software
Configuration Guide.
Cisco BPX 8600 Series Installation and Configuration
1-8
Release 9.3.0, Part Number 78-10674-01 Rev. D0, July 2001