3Com S7902E, Руководство по настройке

Страница: 863 / 2621

1-3
z
Intra-Area-Prefix-LSA: Each Intra-Area-Prefix-LSA contains IPv6 prefix information on a router,
stub area or transit area information, and has area flooding scope. It was introduced because
Router-LSAs and Network-LSAs contain no address information now.
RFC 5187 defines the Type 11 LSA, Grace-LSA. A Grace-LSA is generated by a GR (Graceful Restart)
Restarter at reboot and transmitted on the local link. The restarter describes the cause and interval of
the reboot in the Grace-LSA to tell its neighbors that it performs a GR operation.
Timers of OSPFv3
Timers in OSPFv3 include:
z
OSPFv3 packet timer
z
LSA delay timer
z
SPF timer
z
GR timer
OSPFv3 packet timer
Hello packets are sent periodically between neighboring routers for finding and maintaining neighbor
relationships, or for DR/BDR election. The hello interval must be identical on neighboring interfaces.
The smaller the hello interval, the faster the network convergence speed and the bigger the network
load.
If a router receives no hello packet from a neighbor within a period, it will declare the peer is down. The
period is called the dead interval.
After sending an LSA to its adjacency, a router waits for an acknowledgment from the adjacency. If no
response is received after the retransmission interval elapses, the router will send again the LSA. The
retransmission interval must be longer than the round-trip time of the LSA.
LSA delay time
Each LSA has an age in the local LSDB (incremented by 1 per second), but an LSA does not age on
transmission. You need to add an LSA delay time into the age time before transmission, which is
important for low-speed networks.
SPF timer
Whenever the LSDB changes, an SPF calculation happens. If recalculations become so frequent, a
large amount of resources will be occupied. You can adjust the SPF calculation interval and delay time
to protect networks from being overloaded due to frequent changes.
GR timer
If a failure to establish adjacencies occurs during a GR, the device will be in the GR process for a long
time. To avoid such cases, you can configure the GR timer for the device to exit the GR process when
the timer expires.
OSPFv3 Features Supported
z
Basic features defined in RFC 2740