3com S7906E Manuel De Montage

 

1-11 

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 (10s by default). On point-to-point 

networks, CSNP is only sent during the first adjacency establishment. 

The CSNP packet format is shown in 

. 

Figure 1-11 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. 

 shows the PSNP packet format.