3Com Switch 4800G 24-Port Configuration Manual page 337

Figure 110 shows the PSNP packet format.
Figure 110 L1/L2 PSNP format
Intradomain routing protocol discriminator
Length indicator
Version/Protocol ID extension
ID length
R R R
Version
Reserved
Maximum area address
PDU length
Source ID
Variable length fields
CLV
The variable fields of PDU are composed of multiple Code-Length-Value (CLV)
triplets. Figure 111 shows the CLV format.
Figure 111 CLV format
Code
Length
Value
Table 45 shows different PDUs contain different CLVs.
Table 45 CLV name and the corresponding PDU type
CLV Code Name
1 Area Addresses
2 IS Neighbors (LSP)
4 Partition Designated Level2 IS
6 IS Neighbors (MAC Address)
7 IS Neighbors (SNPA Address)
8 Padding
9 LSP Entries
10 Authentication Information
128 IP Internal Reachability Information
129 Protocols Supported
130 IP External Reachability Information
131 Inter-Domain Routing Protocol Information
132 IP Interface Address
No. of Octets
1
1
1
1
PDU type 1
1
1
1
2
ID length+1
No. of Octets
1
1
Length
IS-IS Overview 337
PDU Type
IIH, LSP
LSP
L2 LSP
LAN IIH
LAN IIH
IIH
SNP
IIH, LSP, SNP
LSP
IIH, LSP
L2 LSP
L2 LSP
IIH, LSP