Configuring Lsp Ping - Zte ZXR10 ZSR V2 Configuration Manual (System Management

1 100.0.0.22 55 ms 2 ms 2 ms
/*The IP address on the first-hop device and time delays*/
2 10.17.94.81 176 ms 143 ms 333 ms
3 10.28.5.61 131 ms 133 ms 134 ms
4
/*The fourth-hop device does not return any packet. There are "*" marks.*/
5 202.70.62.169 151 ms 149 ms 146 ms
6 202.43.177.81 176 ms 162 ms 165 ms
7 218.100.27.30 142 ms 134 ms 159 ms
8 175.103.59.110 140 ms 166 ms 138 ms
[finished]

15.7 Configuring LSP Ping

Overview
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Description of LSP Ping
On an
switching is performed. IP ping, however, only checks connectivity on the IP plane,
but cannot check LSPs. On an MPLS network, if a
disconnected, labels cannot be forwarded. In this case, IP ping packets are reachable,
but the LSP fails.
Various factors cause LSP faults. For example, an LDP session is disconnected, LDP
is not enabled on some LSRs, or an exception occurs in an LDP label forwarding table.
A mechanism different from IP ping is needed to detect whether an end-to-end LSP
is operating properly. Therefore, LSP ping is generated.
LSP ping uses a packet belonging to a specific Forwarding Equivalence Class
(FEC) to verify the integrity of the LSP (from the source LSR to the destination LSR)
that belongs to this FEC. An LSP ping request packet contains information on the
corresponding FEC.
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Work Flow of LSP Ping
An LSP ping packet is encapsulated in a UDP packet, and contains a serial number
and a time stamp. When processing an LSP ping request packet, MPLS uses the
same forwarding policy as packets of the FEC. When the LSP ping packet reaches
an LSP egress, the LSR control plane checks the packet to verify whether this LSP is
the correct egress of the FEC.
Similar to IP ping, LSP ping also uses the Echo Request and Echo Reply mechanism.
But the LSP ping packet format is completely different from the IP ping packet format.
Packets sent by LSP ping are not ICMP packets but UDP packets whose port number
is 3503. On an MPLS network,
1. A source device sends a UDP Echo Request packet whose port number is 3503.
2. LSRs forward the Echo Request packet through label switching.
SJ-20140504150128-007|2014-05-10 (R1.0)
* * *
MPLS network, if IP ping is used, labels are added to ping packets and label
Chapter 15 Network Layer Detection
LDP
15-15
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session between two LSRs is