3Com Switch 4800G 24-Port Configuration Manual page 334

334 C 29: IS-IS C
HAPTER ONFIGURATION
Figure 106 P2P IIH format
Intradomain routing protocol discriminator
Length indicator
Version/Protocol ID extension
ID length
R R R
Version
Reserved
Maximum area address
Reserved/Circuit type
Source ID
Holding time
PDU length
Local Circuit ID
Variable length fields
Instead of the priority and LAN ID fields in the LAN IIH, the P2P IIH has a Local
Circuit ID field.
LSP packet format
The Link State PDUs (LSP) carries link state information. There are two types:
Level-1 LSP and Level-2 LSP. The Level-2 LSP is sent by the Level-2 router, and the
Level-1 LSP is sent by the Level-1 router. The level-1-2 router can sent both types
of the LSPs.
Two types of LSPs have the same format, as shown in Figure 107.
No. of Octets
1
1
1
1
PDU type 1
1
1
1
1
ID length
2
2
1