Lers At The Input Edge Of An Mpls Network - Cisco 7604 Configuration Manual

PFC3BXL or PFC3B Mode MPLS QoS
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PE1 and PE2 are at the boundaries between the MPLS network and the IP network.
Note
These sections describe LER and LSR operation in an MPLS network.
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The QoS capabilities at the input interface differ depending on whether the input interface is a LAN port,
Note
a WAN port on an OSM, or a port adapter on a FlexWAN or Enhanced FlexWAN module. This section
is for LAN ports. For information on OSMs, see the OSM Configuration Note, 12.2SX. For information
on a FlexWAN or Enhanced FlexWAN module, see the FlexWAN and Enhanced FlexWAN Installation
and Configuration Note.

LERs at the Input Edge of an MPLS Network

Incoming labels are aggregate or nonaggregate. The aggregate label indicates that the arriving MPLS or
Note
MPLS VPN packet must be switched through an IP lookup to find the next hop and the outgoing
interface. The nonaggregate label indicates that the packet contains the IP next hop information.
This section describes how edge LERs can operate at either the ingress or the egress side of an MPLS
network.
At the ingress side of an MPLS network, LERs process packets as follows:
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Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
42-6
PE2—service provider egress LER
CE2—Customer equipment 2
LERs at the Input Edge of an MPLS Network, page 42-6
LSRs in the Core of an MPLS Network, page 42-7
LERs at the Output Edge of an MPLS Network, page 42-7
Layer 2 or Layer 3 traffic enters the edge of the MPLS network at the edge LER (PE1).
The PFC3BXL or PFC3B receives the traffic from the input interface and uses the 802.1p bits or the
IP ToS bits to determine the EXP bits and to perform any classification, marking, and policing. For
classification of incoming IP packets, the input service policy can also use access control lists
(ACLs).
For each incoming packet, the PFC3BXL or PFC3B performs a lookup on the IP address to
determine the next-hop router.
The appropriate label is pushed (imposition) into the packet, and the EXP value resulting from the
QoS decision is copied into the MPLS EXP field in the label header.
The PFC3BXL or PFC3B forwards the labeled packets to the appropriate output interface for
processing.
The PFC3BXL or PFC3B also forwards the 802.1p bits or the IP ToS bits to the output interface.
At the output interface, the labeled packets are differentiated by class for marking or policing. For
LAN interfaces, egress classification is still based on IP, not on MPLS.
The labeled packets (marked by EXP) are sent to the core MPLS network.
Chapter 42 Configuring PFC3BXL or PFC3B Mode MPLS QoS
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