3Com S7902E, Configuration Manual

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1-2
OSPFv3 Packets
OSPFv3 has also five types of packets: hello, DD, LSR, LSU, and LSAck.
The five packets have the same packet header, which different from the OSPFv2 packet header is only
16 bytes in length, has no authentication field, but is added with an Instance ID field to support
multi-instance per link.
Figure 1-1 gives the OSPFv3 packet header.
Figure 1-1 OSPFv3 packet header
Major fields:
z
Version #: Version of OSPF, which is 3 for OSPFv3.
z
Type: Type of OSPF packet; Types 1 to 5 are hello, DD, LSR, LSU, and LSAck respectively.
z
Packet Length: Packet length in bytes, including header.
z
Instance ID: Instance ID for a link.
z
0: Reserved. It must be 0.
OSPFv3 LSA Types
OSPFv3 sends routing information in LSAs, which as defined in RFC 2740 have the following types:
z
Router-LSA: Originated by all routers. This LSA describes the collected states of the router's
interfaces to an area. Flooded throughout a single area only.
z
Network-LSA: Originated for broadcast and NBMA networks by the Designated Router. This LSA
contains the list of routers connected to the network. Flooded throughout a single area only.
z
Inter-Area-Prefix-LSA: Similar to Type 3 LSA of OSPFv2, originated by ABRs (Area Border
Routers), and flooded throughout the LSA's associated area. Each Inter-Area-Prefix-LSA
describes a route with IPv6 address prefix to a destination outside the area, yet still inside the AS
(an inter-area route).
z
Inter-Area-Router-LSA: Similar to Type 4 LSA of OSPFv2, originated by ABRs and flooded
throughout the LSA's associated area. Each Inter-Area-Router-LSA describes a route to ASBR
(Autonomous System Boundary Router).
z
AS-external-LSA: Originated by ASBRs, and flooded throughout the AS (except Stub and NSSA
areas). Each AS-external-LSA describes a route to another Autonomous System. A default route
can be described by an AS external LSA.
z
Link-LSA: A router originates a separate Link-LSA for each attached link. Link-LSAs have link-local
flooding scope. Each Link-LSA describes the IPv6 address prefix of the link and Link-local address
of the router.