Allied Telesis AT-9724TS specifications Database Description Packet, On the network, 109

OSPF Hello Packet
Octets
0	1	2	3	4
Version No.		1	Packet Length
		Router ID
		Area ID

Checksum

Authentication Type

Authentication

Authentication

Network Mask

Hello Interval		Options	Router Priority
	Router Dead Interval
	Designated Router
	Backup Designated Router
	Neighbour

		Figure 6- 101. Hello Packet
	Field	Description
	Network Mask	The network mask associated with this interface.
	Options	The optional capabilities supported by the router.
	Hello Interval	The number of seconds between this router’s Hello packets.
	Router Priority	This router’s Router Priority.The Router Priority is used in the election of the DR and BDR. If this field is set
	Router Dead Interval	to 0, the router is ineligible become the DR or the BDR.
		The number of seconds that must pass before declaring a silent router as down.
	Designated Router	The identity of the DR for this network, in the view of the advertising router.The DR is identified here by its IP
	Backup Designated Router	interface address on the network.
		The identity of the Backup Designated Router (BDR) for this network.The BDR is identified here by its IP
	Neighbor	interface address on the network.This field is set to 0.0.0.0 if there is no BDR.
		The Router IDs of each router from whom valid Hello packets have been seen within the Router Dead Interval
		on the network.
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.

Allied Telesyn AT-9724TS High-Density Layer 3 Stackable Gigabit Ethernet Switch 109