D-Link xStack DGS-3600 User Manual page 151

Database Description Packet
Database Description packets are OSPF packet type 2. These packets are exchanged when an adjacency is being initialized. They
describe the contents of the topological database. Multiple packets may be used to describe the database. For this purpose, a poll-
response procedure is used. One of the routers is designated to be master, the other a slave. The master seconds Database
Description packets (polls) that are acknowledged by Database Description packets sent by the slave (responses). The responses
are linked to the polls via the packets' DD sequence numbers.
Field
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.
xStack DGS-3600 Series Layer 3 Gigabit Ethernet Managed Switch
Database Description Packet
2
Version No.
Checksum
Reserved
I M MS
Reserved
Link-State Advertisement Header ...
Figure 8- 29. 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.
User 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
Router ID
Area ID
Authentication Type
Authentication
Authentication
Options
DD Sequence No.
135