HPE 5800 Series Configuration Manual page 131

Major fields of the L1/L2 LSP are:
•
PDU length—Total length of the PDU in bytes.
•
Remaining lifetime—LSP remaining lifetime in seconds.
•
LSP ID—Consists of the system ID, the pseudonode ID (one byte) and the LSP fragment
number (one byte).
•
Sequence number—LSP sequence number.
•
Checksum—LSP checksum.
•
P (Partition)—Partition bit that is only for L2 LSPs. This field indicates whether the router
supports partition repair.
•
ATT (Attach)—Attach bit that is generated by a L1/L2 router for L1 LSPs only. This field
indicates that the router generating the LSP is connected to multiple areas.
•
OL (Overload)—Indicates that the LSDB is not complete because the router has run out of
memory. Other routers will not send packets to the overloaded router, except packets destined
to the networks directly connected to the router. For example, in
packets to Router C through Router B. Once other routers know the OL field of LSPs from
Router B is set to 1, Router A will send packets to Router C via Router D and Router E, but still
send to Router B packets destined to the network directly connected to Router B.
•
IS type—Type of the router generating the LSP.
Figure 44 LSDB overload
SNP
A sequence number PDU (SNP) describes the complete or partial LSPs for LSDB synchronization.
SNPs include Complete SNP (CSNP) and Partial SNP (PSNP), which are further divided into Level-1
CSNP, Level-2 CSNP, Level-1 PSNP and Level-2 PSNP.
A CSNP describes the summary of all LSPs for LSDB synchronization between neighboring routers.
On broadcast networks, CSNPs are sent by the DIS periodically (10s by default). On point-to-point
networks, CSNPs are only sent during the adjacency establishment.
The CSNP packet format is shown in Figure 45.
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Figure 44, Router A forwards