Back-Off Mechanism; Sflow On Lag Ports; Extended Sflow - Dell Force10 C150 Configuration Manual

Note: Sampling rate backoff can change the sampling rate value that is set in the hardware. This equation
shows the relationship between actual sampling rate, sub-sampling rate, and the hardware sampling rate
for an interface:
Note the absence of a configured rate in the equation. That is because when the hardware sampling rate
value on the port-pipe exceeds the configured sampling rate value for an interface, the actual rate changes
to the hardware rate. The sub-sampling rate never goes below a value of one.

Back-off Mechanism

If the sampling rate for an interface is set to a very low value, the CPU can get overloaded with flow
samples under high-traffic conditions. In such a scenario, a binary back-off mechanism gets triggered,
which doubles the sampling-rate (halves the number of samples per second) for all interfaces. The backoff
mechanism continues to double the sampling-rate until CPU condition is cleared. This is as per sFlow
version 5 draft. Once the back-off changes the sample-rate, users must manually change the sampling rate
to the desired value.
As a result of back-off, the actual sampling-rate of an interface may differ from its configured sampling
rate. The actual sampling-rate of the interface and the configured sample-rate can be viewed by using the
show sflow

sFlow on LAG ports

When a physical port becomes a member of a LAG, it inherits the sFlow configuration from the LAG port.

Extended sFlow

Extended sFlow
Platforms
Extended sFlow packs additional information in the sFlow datagram depending on the type of sampled
packet. The following options can be enabled:
extended-switch
•
extended-router
•
extended-gateway
•
Note: The entire AS path is not included. BGP community-list and local preference information are not
included. These fields are assigned default values and are not interpreted by the collector.
980 | sFlow
Actual sampling rate = sub-sampling rate * hardware sampling rate
command.
is supported fully on platform
c s
extended-switch
and support
— 802.1Q VLAN ID and 802.1p priority information
— Next-hop and source and destination mask length.
— Source and destination AS number and the BGP next-hop.
e
information processing only.