Operation Manual – IPv4 Routing
H3C S3610&S5510 Series Ethernet Switches
Chapter 4 IS-IS Configuration
4-13
Figure 4-10
LSDB overload
z
IS Type: Type of the router generating the LSP.
V. SNP format
The Sequence Number PDU (SNP) confirms the latest received LSPs. It is similar to
the Acknowledge packet, but more efficient.
SNP contains 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
Intradomain routing protocol discriminator
Reserved
Version
R
ID length
Version/Protocol ID extension
Length indicator
Maximum area address
R
R
PDU type
No. of Octets
1
1
1
1
1
1
1
1
PDU length
Source ID
Start LSP ID
End LSP ID
Variable length fields
2
ID 1
ID 2
ID 2
Figure 4-11
L1/L2 CSNP format
