H3C Technologies H3C S12500 Series Switches - Manual (Page 153)

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NOTE:
On IS-IS broadcast networks, all routers are adjacent with each other. However, the DIS is responsible for
the synchronization of their LSDBs.
IS-IS PDU
PDU
IS-IS packets are encapsulated into link layer frames. An IS-IS PDU has two parts, the headers and the
variable length fields, where the headers comprise the PDU common header and the PDU specific
header. All PDUs have the same PDU common header, while the specific headers vary by PDU type.
Figure 56 PDU format
Common header format
Figure 57 PDU common header format
Major fields of the PDU common header are as follows:
• Intradomain routing protocol discriminator—Set to 0x83.
• Length indicator—Length of the PDU header in bytes, including both common and specific headers.
• Version/Protocol ID extension—Set to 1(0x01).
• ID length—Length of the NSAP address and NET ID.
• R(Reserved)—Set to 0.
• PDU type—For detailed information, see Table 4 .
• Version—Set to 1(0x01).
• Maximum area address—Maximum number of area addresses supported.
Table 4 PDU type
Type PDU Type Acronym
15 Level-1 LAN IS-IS hello PDU L1 LAN IIH
16 Level-2 LAN IS-IS hello PDU L2 LAN IIH
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