286 CHAPTER 28: OSPF CONFIGURATION
Figure 84 LSR packet format
Major fields:
■ LS type: Type number of the LSA to be requested. Type 1 for example indicates
the Router LSA.
■ Link State ID: Determined by LSA type.
■ Advertising Router: ID of the router that sent the LSA.
LSU packet
LSU (Link State Update) packets are used to send the requested LSAs to peers, and
each packet carries a collection of LSAs. The LSU packet format is shown below.
Figure 85 LSU packet format
LSAck packet
LSAack (Link State Acknowledgment) packets are used to acknowledge received
LSU packets, contents including LSA headers to describe the corresponding LSAs.
Multiple LSAs can be acknowledged in a single Link State Acknowledgment
packet. The following figure gives its format.
Version 3
Router ID
Area ID
Checksum AuType
Packet length
Authentication
Authentication
LS type
Link state ID
...
Advertising router
0 7 15 31
...
Version 4
Router ID
Area ID
Checksum AuType
Packet length
Authentication
Authentication
Number of LSAs
LSA
0 7 15 31
LSA
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