Specifications

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Cisco IGX 8400 Series Provisioning Guide, Release 9.3.3 and Later Releases
OL-1166-04
Chapter 10 Cisco IGX 8400 Series IP Service
IP Service—Functional Overview
Tip To save rack space, use multiple, separately-installed URMs as LSCs for multiple partitions on the same
IGX node.
For more information on MPLS on the IGX, refer to MPLS Label Switch Controller and Enhancements
12.2(8)T.
MPLS Labeling Criteria
For enabling business IP services, the most significant benefit of MPLS is the ability to assign labels
that have special meanings. Sets of labels distinguish destination address and application type or service
class (see Figure 10-7).
Figure 10-7 Benefits of MPLS Labels
The MPLS label is compared to precomputed switching tables in core devices, such as the IGX ATM
LSR, allowing each switch to automatically apply the correct IP services to each packet. Tables are
precalculated, to avoid reprocessing packets at every hop. This strategy not only makes it possible to
separate types of traffic, such as best-effort traffic from mission-critical traffic, it also makes an MPLS
solution highly scalable.
Because MPLS uses different policy mechanisms to assign labels to packets, it decouples packet
forwarding from the content of IP headers. Labels have local significance, and they are used many times
in large networks. Therefore, it is almost impossible to run out of labels. This characteristic is essential
to implementing advanced IP services such as QoS, large-scale VPNs, and traffic engineering.
25095
ATM switch
Router
Service class (QoS)
Privacy (VPN)
Traffic engineered path
Provider MPLS network
Label
IP packet