Tuning ISIS-SPB LSP timers
Change LSP timer settings depending on network stability to increase the network convergence speed and protect CPU from unnecessary route recalculations.
Table 4: ISIS-SPB LSP timers
LSP timer | Functionality | Tuning guidelines |
|---|---|---|
Minimum LSP transmit interval | Sets the minimum interval for transmitting LSPs out of an interface. You can also set the number of LSPs that can be sent at each interval. | Increase the interval to reduce LSP traffic in the network. Decrease the interval for quick LSDB synchronization. |
LSP lifetime | Sets the amount of time that an LSP can be retained in an LSDB. | Set the lifetime to a higher value than the LSP refresh interval. |
LSP refresh interval and LSP generation timer | Control the update interval for an LSP. | Increase the interval to protect the CPU from frequent LSP generation. Decrease the interval for quick reaction to topology change events. |
LSP fast-flooding | Floods the first several LSPs that invoke SPF before SPF computation is started. | Enable this feature for quick LSDB synchronization. |
Setting the minimum LSP transmit interval and the maximum number of LSPs sent at each interval
To control ISIS-SPB traffic on a circuit, set the minimum interval for the device to transmit LSPs out of the circuit and the maximum number of LSPs sent at each interval. Before the minimum interval expires, newly generated LSP updates must wait in queue before they can be sent out.
To control ISIS-SPB traffic on the SPBM network:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter Layer 2 Ethernet interface view or Layer 2 aggregate interface view. | interface interface-type interface-number | N/A |
3. Set the minimum LSP transmit interval and the maximum number of LSP segments sent at each interval. | spbm timer lsp time [ count count ] | By default, the minimum LSP transmit interval is 33 milliseconds. A maximum of five LSP segments can be sent at each interval. |
![[NOTE: ]](images/note.png) | NOTE: ISIS-SPB requires acknowledgment for each LSP sent on a point-to-point circuit. ISIS-SPB will retransmit an LSP at 5-second interval until it receives an acknowledgment for the LSP. This retransmission interval is not user configurable. | |
Setting the LSP lifetime
The LSP lifetime specifies the maximum amount of time for an LSP to be retained in an LSDB.
SPBM nodes add a lifetime in each LSP they have advertised. If an SPBM node does not receive an update for an LSP before its lifetime expires, the SPBM node performs the following operations:
Removes the LSP from the LSDB.
Retains the LSP digest for 60 seconds.
Sends an update of the LSP with a lifetime of 0. The SPBM neighbors remove the LSP from their LSDBs when they receive the LSP update.
To set the maximum LSP lifetime:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter SPBM view. | spbm | N/A |
3. Set the maximum LSP lifetime. | timer lsp-max-age seconds | The default maximum LSP lifetime is 1200 seconds. |
Tuning the LSP refresh interval and LSP generation timer
To prevent LSPs from age-out and synchronize LSDBs, ISIS-SPB performs periodic and event-driven LSP updates:
LSP refresh interval—Sets the interval at which ISIS-SPB regularly regenerates an LSP, regardless of whether any change has occurred to the LSP.
LSP generation timer—Sets the delay for ISIS-SPB to generate a new version of an LSP in response to an LSP change. For example, an update occurs because of a change in adjacency, interface metric value, system ID, or area address.
The LSP generation timer is an exponential generation timer. With this timer, ISIS-SPB quickly responds to the first events for an LSP and then slows down to protect the CPU from frequent LSP generation.
The LSP generation timer value is derived from the following parameters:
minimum-interval—Minimum LSP generation interval.
incremental-interval—Base number for the incremental interval.
maximum-interval—Maximum LSP generation interval.
When the network is stable, the LSP generation timer is set to the minimum interval for each LSP generation. When the network is unstable, the LSP generation timer increments by incremental-interval×2n-2 (n is the number of generation times) for each LSP generation until the maximum interval is reached. If an event triggers LSP generation after the maximum interval is reached, the LSP generation timer re-initiates with the minimum interval.
| NOTE: The network is considered unstable if the interval between consecutive LSP generation events is smaller than two times the maximum interval. | |
To tune the LSP refresh interval and the LSP regeneration timer parameters:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter SPBM view. | spbm | N/A |
3. Set the LSP refresh interval. | timer lsp-refresh seconds | The default refresh interval is 900 seconds. |
4. Set the LSP generation timer parameters. | timer lsp-generation maximum-interval [ minimum-interval [ incremental-interval ] ] | Default values for the LSP generation timer parameters:
The minimum interval and the incremental interval must be shorter than the maximum interval. |
Enabling LSP fast-flooding
LSP fast-flooding enables ISIS-SPB to flood the first several LSPs that invoke SPF before SPF computation is started. This mechanism improves ISIS-SPB convergence time. The number of LSPs that can be fast flooded is user configurable.
To configure LSP fast-flooding:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter SPBM view. | spbm | N/A |
3. Configure LSP fast-flooding. | flash-flood [ flood-count flooding-count | max-timer-interval interval ] * | By default, LSP fast-flooding is disabled. |