Implementing IBM System Networking 10Gb Ethernet Switches

76 Implementing IBM System Networking 10Gb Ethernet Switches

When polling is enabled, at the end of each configured polling interval, the switch reports

general port statistics and port Ethernet statistics.

sFlow network sampling

In addition to statistical counters, IBM System Networking switches can be configured to

collect periodic samples of the traffic data received on each port. For each sample, 128 bytes

are copied, UDP-encapsulated, and sent to the configured sFlow analyzer.

For each port, the sFlow sampling rate can be configured to occur every 256 - 65536 packets,

or set to 0 to disable (the default) this feature. A sampling rate of 256 means that one sample

is taken for approximately every 256 packets received on the port. The sampling rate is

statistical, however. It is possible to have more or fewer samples sent to the analyzer for any

specific group of packets (especially under low traffic conditions). The actual sample rate

becomes most accurate over time, and under higher traffic flow.

sFlow sampling has the following restrictions:

򐂰 Sample rate: The fastest sFlow sample rate is 1 out of every 256 packets.

򐂰 ACLs: sFlow sampling is performed before ACLs are processed. For ports configured both

with sFlow sampling and one or more ACLs, sampling occurs regardless of the action of

the ACL.

򐂰 Port mirroring: sFlow sampling does not occur on mirrored traffic. If sFlow sampling is

enabled on a port that is configured as a port monitor, the mirrored traffic is not sampled.

2.6.4 Remote Monitoring (RMON)

Remote Monitoring (RMON) allows network devices to exchange network monitoring data.

RMON allows the switch to perform the following functions:

򐂰 Track events and trigger alarms when a threshold is reached.

򐂰 Notify administrators by issuing a syslog message or SNMP trap.

RMON overview

The RMON MIB provides an interface between the RMON agent on the switch and an RMON

management application. The RMON MIB is described in RFC 1757, found at:

http://www.ietf.org/rfc/rfc1757.txt

The RMON standard defines objects that are suitable for the management of Ethernet

networks. The RMON agent continuously collects statistics and proactively monitors switch

performance. You can use RMON to monitor traffic that flows through the switch.

sFlow sampling: Although sFlow sampling is not generally a processor -intensive

operation, configuring fast sampling rates (such as once every 256 packets) on ports

under heavy traffic loads can cause switch processor utilization to reach maximum. Use

larger rate values for ports that experience heavy traffic.