KTI KGS-3120, Руководство по эксплуатации, Страница: 115 / 221

-115-
OSPF Packet Header
Field Description
Version No. The OSPF version number
Type The OSPF packet type.
The OSPF packet types are as follows:
. Hello
. Database Description
. Link-State Request
. Link-State Update
. Link-State Acknowledgment
Packet Length The length of the packet in bytes. This length includes the 24-byte header.
Router ID The Router ID of the packet’ s source.
Area ID A 32-bit number identifying the area that this packet belongs to. All OSPF
packets are associated with a single area. Packets traversing a virtual link
are assigned the backbone Area ID of 0.0.0.0
Checksum A standard IP checksum that includes all of the packet’ s contents except
for the 64-bit authentication field.
Authentication Type The type of authentication to be used for the packet.
Authentication A 64-bit field used by the authentication scheme.
Hello Packet
Hello packets are OSPF packet type 1. They are sent periodically on all interfaces, including virtual
links, in order to establish and maintain neighbor relationships. In addition, Hello Packets are multicast
on those physical networks having a multicast or broadcast capability, enabling dynamic discovery of
neighboring routers.
All routers connected to a common network must agree on certain parameters such as the Network
Mask, the Hello Interval, and the Router Dead Interval. These parameters are included in hello pack-
ets, so that differences can inhibit the forming of neighbor relationships. A detailed explanation of the
receive processing for Hello packets, so that differences can inhibit the forming of neighbor relation-
ships.