TP-Link JetStream T2700G-28TQ User Manual page 201

Router Dead Interval: When the receiving router doesn't receive another Hello packet
4)
update from the advertising router within the specified age time, it will delete the advertising
router from its neighbor table. Only routers with the coincident dead interval can be neighbors.
5) Designated Router ID: The interface IP of the router specified by the advertising router in the
advertising interface network.
6) Backup Designated Router ID: The interface IP of the backup router specified by the
advertising router in the advertising interface network.
7) Neighbor: All the neighbor tables of the advertising router, listing the neighbor interface IP
addresses in each interface network segment.
3. DD Packet
Two routers after becoming neighbors will send to each other the header of all routing information
in its link state database through the DD packets, in which way the receiving router could
synchronize the database.
1) Interface MTU: Size in bytes of the largest IP packet that can be sent out by the routing
interface of the advertising router.
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.
M: The More bit. When the forwarded DD packet is not the last one database, it will set its
3)
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.
Figure 10-41 DD Packet
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