Is-Is Pdu Format - 3Com MSR 50 Series Configuration Manual

IS-IS PDU Format

PDU header format
The IS-IS packets are encapsulated into link layer frames. The Protocol Data Unit
(PDU) consists of two parts, the headers and the variable length field, where the
headers can be further divided into the common header and the specific header.
The common headers are the same for all PDUs, while the specific headers vary by
PDU type. The following figure shows the PDU format.
Figure 257 PDU format
Common header format
Figure 258
Figure 258 PDU common header format
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Table 41 PDU type
Type
15
16
17
18
20
24
25
26
PDU common header PDU specific header
shows the common header format.
Intradomain routing protocol discriminator
Length indicator
Version/Protocol ID extension
ID length
R R R
Version
Reserved
Maximum area address
Intra-domain Routing Protocol Discriminator: Set to 0x83.
Length Indicator: The length of the PDU header, including both common and
specific headers, present in bytes.
Version/Protocol ID Extension: Set to 1(0x01).
ID Length: The length of the NSAP address and NET ID.
R(Reserved): Set to 0.
PDU Type: For detail information, refer to
Version: Set to 1(0x01).
Maximum Area Address: Maximum number of area addresses supported.
PDU Type
Level-1 LAN IS-IS hello PDU
Level-2 LAN IS-IS hello PDU
Point-to-Point IS-IS hello PDU
Level-1 Link State PDU
Level-2 Link State PDU
Level-1 Complete Sequence Numbers PDU
Level-2 Complete Sequence Numbers PDU
Level-1 Partial Sequence Numbers PDU
Variable length fields (CLV)
No. of Octets
1
1
1
1
PDU type 1
1
1
1
Table
IS-IS Overview
41.
Acronym
L1 LAN IIH
L2 LAN IIH
P2P IIH
L1 LSP
L2 LSP
L1 CSNP
L2 CSNP
L1 PSNP
883