3Com S7906E Configuration Manual page 647

LSAck packet
Link State Acknowledgment (LSAck) packets are used to acknowledge received LSU packets by
carrying LSA headers to describe corresponding LSAs. Multiple LSAs can be acknowledged in a single
LSAck packet. The following figure gives its format.
Figure 1-14 LSAck packet format
LSA header format
All LSAs have the same header, as shown in the following figure.
Figure 1-15 LSA header format
Major fields:
LS age: Time in seconds elapsed since the LSA was originated. A LSA ages in the LSDB (added
by 1 per second), but does not in transmission.
LS type: Type of the LSA.
Link State ID: The contents of this field depend on the LSA's type
LS sequence number: Used by other routers to judge new and old LSAs.
LS checksum: Checksum of the LSA except the LS age field.
Length: Length in bytes of the LSA, including the LSA header.
Formats of LSAs
1) Router LSA
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