Snp format – H3C Technologies H3C S12500 Series Switches User Manual
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Figure 61 LSDB overload
SNP format
A sequence number PDU (SNP) acknowledges the latest received LSPs. It is similar to an Acknowledge
packet, but more efficient.
SNP involves 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.
CSNP covers the summary of all LSPs in the LSDB to synchronize the LSDB between neighboring routers.
On broadcast networks, CSNP is sent by the DIS periodically (10 seconds by default). On point-to-point
networks, CSNP is only sent during the first adjacency establishment.
Figure 62 L1/L2 CSNP format
PSNP only contains the sequence numbers of one or multiple latest received LSPs. It can acknowledge
multiple LSPs at one time. When LSDBs are not synchronized, a PSNP is used to request new LSPs from
neighbors.