TTL Processing on Incoming MPLS Packets
The flow chart on Figure 51 on page 215 illustrates TTL processing on incoming MPLS
packets. On a transit LSR or an egress LER, MPLS pops one or more labels and can
push one or more labels. The incoming TTL of the packet is determined by the
configured TTL processing tunnel model.
When all of the following conditions are met, the incoming TTL is set to the TTL value
found in the immediate inner header:
■
The outer label is popped as opposed to being swapped
■
The TTL processing model is configured to pipe
■
The inner header is MPLS or IP
If any of those conditions is not met, then the incoming TTL is set to the TTL value
found in the outermost label. In all cases, the TTL values of any further inner labels
are ignored.
When an IP packet is exposed after MPLS pops all the labels that should be popped,
MPLS passes the packet to IP for further processing, including TTL checking. When
the uniform tunnel model for TTL processing is in effect, MPLS sets the TTL value of
the IP packet to the incoming TTL value that was just set. In other words, the TTL
value is copied from the outermost label to the IP packet. When the pipe model for
TTL processing is in effect, the TTL value in the IP header is left unchanged.
If an IP packet is not exposed by the label popping, then MPLS performs the TTL
validation. If the incoming TTL is less than 2, the packet is dropped. If innermost
packet is IP, an ICMP packet is built and sent. If the TTL does not expire and the
packet needs to be sent out, the outgoing TTL is determined by the rules for outgoing
MPLS packets.
214
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MPLS Label Switching and Packet Forwarding
JUNOSe 11.0.x BGP and MPLS Configuration Guide
Содержание JUNOSE
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Страница 24: ...xxiv Table of Contents JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 37: ...Part 1 Border Gateway Protocol Configuring BGP Routing on page 3 Border Gateway Protocol 1...
Страница 38: ...2 Border Gateway Protocol JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 234: ...198 Monitoring BGP JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 236: ...200 Multiprotocol Layer Switching JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 298: ...262 Point to Multipoint LSPs Configuration JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 346: ...310 Example Traffic Class Configuration for Differentiated Services JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 535: ...There is no no version See undebug ip mbgp Monitoring BGP MPLS VPNs 499 Chapter 5 Configuring BGP MPLS Applications...
Страница 536: ...500 Monitoring BGP MPLS VPNs JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 538: ...502 Layer 2 Services Over MPLS JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 592: ...556 Multiple ATM Virtual Circuits over a Single Pseudowire Example JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 604: ...568 Virtual Private LAN Service JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 618: ...582 VPLS References JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 642: ...606 VPLS Configuration Example with LDP Signaling JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 674: ...638 Virtual Private Wire Service JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 718: ...682 Monitoring MPLS Forwarding Table for VPWS JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 719: ...Part 6 Index Index on page 685 Index 683...
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