D-Link DES-3326SRM - Switch - Stackable Product Manual page 177

Each advertisement requested is specified by its Link-State Type, Link-State ID, and Advertising Router. This uniquely
identifies the advertisement, but not its instance. Link-State Request packets are understood to be requests for the most recent
instance.
The Link-State Update Packet
Link-State Update packets are OSPF packet type 4. These packets implement the flooding of link-state advertisements. Each
Link-State Update packet carries a collection of link-state advertisements one hop further from its origin. Several link-state
advertisements may be included in a single packet.
Link-State Update packets are multicast on those physical networks that support multicast/broadcast. In order to make the
flooding procedure reliable, flooded advertisements are acknowledged in Link-State Acknowledgment packets.
retransmission of certain advertisements is necessary, the retransmitted advertisements are always carried by unicast Link-State
Update packets.
The format of the Link-State Update packet is shown below:
The body of the Link-State Update packet consists of a list of link-state advertisements. Each advertisement begins with a
common 20-byte header, the link-state advertisement header. Otherwise, the format of each of the five types of link-state
advertisements is different.
D-Link DES-3326S Layer 3 Switch
Link-State Request Packet
Version No.
Checksum
Link-State Update Packet
4
Version No.
Checksum
Number of Advertisements
Link-State Advertisements ...
3
Packet Length
Router ID
Area ID
Authentication Type
Authentication
Authentication
Link-State Type
Link-State ID
Advertising Router
Packet Length
Router ID
Area ID
Authentication Type
Authentication
Authentication
167
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