Cisco NCS 5500 Series Configuration Manual page 62

Implementing MPLS Traffic Engineering
MPLS-TE Features - Details
For every traffic-engineered tunnel that is configured for an automatic bandwidth, the average output rate is
sampled, based on various configurable parameters. Then, the tunnel bandwidth is readjusted automatically
based on either the largest average output rate that was noticed during a certain interval, or a configured
maximum bandwidth value.
While re-optimizing the LSP with the new bandwidth, a new path request is generated. If the new bandwidth
is not available, the last good LSP remains used. This way, the network experiences no traffic interruptions.
If minimum or maximum bandwidth values are configured for a tunnel, the bandwidth, which the automatic
bandwidth signals, stays within these values.
The output rate on a tunnel is collected at regular intervals that are configured by using the application
command in MPLS-TE auto bandwidth interface configuration mode. When the application period timer
expires, and when the difference between the measured and the current bandwidth exceeds the adjustment
threshold, the tunnel is re-optimized. Then, the bandwidth samples are cleared to record the new largest output
rate at the next interval. If a tunnel is shut down, and is later brought again, the adjusted bandwidth is lost,
and the tunnel is brought back with the initially configured bandwidth. When the tunnel is brought back, the
application period is reset.
MPLS Traffic Engineering Interarea Tunneling
The MPLS-TE interarea tunneling feature allows you to establish TE tunnels spanning multiple Interior
Gateway Protocol (IGP) areas and levels, thus eliminating the requirement that headend and tailend routers
reside in a single area.
Interarea support allows the configuration of a TE LSP that spans multiple areas, where its headend and tailend
label switched routers (LSRs) reside in different IGP areas. Customers running multiple IGP area backbones
(primarily for scalability reasons) requires Multiarea and Interarea TE . This lets you limit the amount of
flooded information, reduces the SPF duration, and lessens the impact of a link or node failure within an area,
particularly with large WAN backbones split in multiple areas.
The following figure shows a typical interarea TE network using OSPF.
Figure 9: Interarea (OSPF) TE Network Diagram
MPLS Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 6.2.x
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