2)
I:
The Initial bit. During the synchronization of link state database between two routers, it
may require multiple DD packets to be forwarded, among which the first DD packet will set
its initial bit to 1, while the others 0.
3)
M:
The More bit. When the forwarded DD packet is not the last one database, it will set its
More Bit to 1, while the last DD packet will set the M-Bit to be 0.
4)
MS:
The Master/Slave bit. Before the synchronization of the link state database between
two routers, master/slave router needs to be elected, which in general is decided by such
parameters as the router priority, router ID and etc. After the election, the master router
will dominate the process of database synchronization. The DD packet forwarded by the
master router would set its MS bit to 1, while that by the slave router would set the MS bit
to 0.
5)
DD Sequence Number:
After the master/slave router having been elected, the master
router randomly determines the sequence number of the first DD packet, and then the
sequence number of the following DD packets increments by one. In this way, the whole
synchronization process will carry on in good order.
6)
LSA header:
The LSA header of the whole or partial link state database of the advertising
router, whose uniqueness identifies a LSA.
4.
LSR Packet
During the synchronization of the link state database between two routers, if one router finds
an updated LSA or an LSA it doesn’t have in the DD packet forwarded, it could send a LSR
packet to request for a complete LSA.
Figure 10-44 LSR Packet
1)
Link State Type:
The type of LSA. There are 11 types of LSA in total: Router LSA, Network
LSA, Network Summarization LSA, ASBR Summarization LSA, and so on. In the following, all
these would be introduced in details.
2)
Link State ID:
It has different meanings for different types of LSA. The Link State ID of
Router LSA stands for the ID of advertising router; that of Network LSA stands for the
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