D-Link xStack DGS-3620 Series Reference Manual page 232

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xStack DGS-3620 Series Layer 3 Managed Stackable Gigabit Switch Web UI Reference Guide
Version No.
Reserved
Parameter
Options
I-bit
M-bit
MS-bit
DD Sequence Number
The rest of the packet consists of a list of the topological database's pieces. Each link state advertisement in the
database is described by its link state advertisement header.
Link-State Request Packet
Link-State Request packets are OSPF packet type 3. After exchanging Database Description packets with a
neighboring router, a router may find that parts of its topological database are out of date. The Link-State Request
packet is used to request the pieces of the neighbor's database that are more up to date. Multiple Link-State
Request packets may need to be used. The sending of Link-State Request packets is the last step in bringing up
an adjacency.
A router that sends a Link-State Request packet has in mind the precise instance of the database pieces it is
requesting, defined by LS sequence number, LS checksum, and LS age, although these fields are not specified in
the Link-State Request packet itself. The router may receive even more recent instances in response.
The format of the Link-State Request packet is shown below:
Database Description Packet
2
Router ID
Checksum
I M MS
Reserved
DD Sequence No.
Link-State Advertisement Header ...
Figure 6-32 Database Description Packet
Description
The optional capabilities supported by the router.
The Initial bit. When set to 1, this packet is the first in the sequence of Database
Description packets.
The More bit. When set to 1, this indicates that more Database Description packets
will follow.
The Master Slave bit. When set to 1, this indicates that the router is the master during
the Database Exchange process. A zero indicates the opposite.
Used to sequence the collection of Database Description Packets. The initial value
(indicated by the Initial bit being set) should be unique. The DD sequence number
then increments until the complete database description has been sent.
Packet Length
Area ID
Authentication Type
Authentication
Authentication
Options
231