3Com Switch 4800G 24-Port Configuration Manual page 287

Figure 86 LSAck packet format
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Version
Checksum
LSA header format
All LSAs have the same header, as shown in the following figure.
Figure 87 LSA header format
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LS age
LS checksum
Major fields:
LS age: Time in seconds elapsed since the LSA was originated. A LSA ages in
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the LSDB (added by 1 per second), but does not in transmission.
LS type: Type of the LSA.
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Link State ID: The contents of this field depend on the LSA's type
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LS sequence number: Used by other routers to judge new and old LSAs.
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LS checksum: Checksum of the LSA except the LS age field.
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Length: Length in bytes of the LSA, including the LSA header.
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15
5
Router ID
Area ID
Authentication
Authentication
LSA header
LSA header
15
Options
Linke state ID
Advertising Router
LS sequence number
Introduction to OSPF 287
Packet length
AuType
LS type
Length
31
31