Network Router User Manual

16-27
ATM Switch Router Software Configuration Guide
OL-7396-01
Chapter 16 Configuring Tag Switching and MPLS
MPLS Network Packet Transmission
Figure 16-6 ATM MPLS LFIB Table Update
MPLS Network Packet Transmission
This section provides a description of a packet being transmitted across an MLPS enabled network and
the process used to switch the packets.
When a packet is received at an MPLS ingress interface the interface driver uses the IDB (interface
descriptor block) to start the following MPLS process on the packet:
• Packet encapsulation is checked and verified
• Packet is checked for QoS or policing limitations.
• Label and ingress interface data are used to check the TFIB trying to determine the egress label and
interface number.
• The TTL field is updated and the label is either replaced with the next hop label or popped (deleted)
if this is the MPLS edge exit LSR.
• The packet is transmitted to the next hop.
a0/0 a0/0/0
a0/1/0
e1/0
a2/0/0
a1/1/0
a1/0/0
a2/1/0
a3/0/0
e3/1/0
e3/2/0
68273
AdminLSR1
NetLSR2
NetLSR3
SalesRt1
172.68.10/24
SalesLSR4
e2/0
SalesRt2
172.68.44/24
AdminRt1
= Packet
= Packet with VPI/VCI label