D-Link xStack Reference Manual page 216

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xStack DGS-3620 Series Layer 3 Managed Stackable Gigabit Switch Web UI Reference Guide
Link-State Update Packet
4
Packet Length
Version No.
Router ID
Area ID
Checksum
Authentication Type
Authentication
Authentication
Number of Advertisements
Link-State Advertisements ...
Figure 6-33 Link-State Update Packet
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.
Link-State Acknowledgment Packet
Link-State Acknowledgment packets are OSPF packet type 5. To make the folding of link-state advertisements
reliable, flooded advertisements are explicitly acknowledged. This acknowledgment is accomplished through the
sending and receiving of Link-State Acknowledgment packets. Multiple link-state advertisements can be
acknowledged in a single Link-State Acknowledgment packet.
Depending on the state of the sending interface and the source of the advertisements being acknowledged, a Link-
State Acknowledgment packet is sent either to the multicast address AllSPFRouters, to the multicast address
AllDRouters, or as a unicast packet.
The format of this packet is similar to that of the Data Description packet. The body of both packets is simply a list
of link-state advertisement headers.
The format of the Link-State Acknowledgment packet is shown below:
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