D-Link DES-3326SR User Manual page 140

DES-3326SR Layer 3 Fast Ethernet Switch User's Guide
Each acknowledged link-state advertisement is described by its
link-state advertisement header. It contains all the information
required to uniquely identify both the advertisement and the
advertisement's current instance.
Link-State Advertisement Formats
There are five distinct types of link-state advertisements. Each
link-state advertisement begins with a standard 20-byte link-
state advertisement header. Succeeding sections then diagram
the separate link-state advertisement types.
Each link-state advertisement describes a piece of the OSPF
routing domain. Every router originates a router links
advertisement. In addition, whenever the router is elected as
the Designated Router,
advertisement. Other types of link-state advertisements may
also be originated. The flooding algorithm is reliable, ensuring
that all routers have the same collection of link-state
advertisements. The collection of advertisements is called the
link-state (or topological) database.
From the link-state database, each router constructs a shortest
path tree with itself as root. This yields a routing table.
There are four types of link state advertisements, each using a
common link state header. These are:
•
Router Links Advertisements
•
Network Links Advertisements
•
Summary Link Advertisements
•
Autonomous System Link Advertisements
The Link State Advertisement Header
All link state advertisements begin with a common 20-byte
header. This header contains enough information to uniquely
it originates a network
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links