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xStack DGS-3600 Series Layer 3 Gigabit Ethernet Managed Switch CLI Manual
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ACL FLOW METERING COMMANDS
Before configuring the ACL Flow Meter, here is a list of acronyms and terms users will need to know.
trTCM – Two Rate Three Color Marker. This, along with the srTCM, are two methods available on the switch for metering and
marking packet flow. The trTCM meters and IP flow and marks it as a color based on the flow’s surpassing of two rates, the CIP and
the PIR.
CIR – Committed Information Rate. Common to both the trTCM and the srTCM, the CIR is measured in bytes of IP
packets. IP packet bytes are measured by taking the size of the IP header but not the link specific headers. For the trTCM, the
packet flow is marked green if it doesn’t exceed the CIR and yellow if it does. The configured rate of the CIR must not
exceed that of the PIR. The CIR can also be configured for unexpected packet bursts using the CBS and PBS fields.
CBS – Committed Burst Size. Measured in bytes, the CBS is associated with the CIR and is used to identify packets
that exceed the normal boundaries of packet size. The CBS should be configured to accept the biggest IP packet that
is expected in the IP flow.
PIR – Peak Information Rate. This rate is measured in bytes of IP packets. IP packet bytes are measured by taking the size
of the IP header but not the link specific headers. If the packet flow exceeds the PIR, that packet flow is marked red. The PIR
must be configured to be equal or more than that of the CIR.
PBS – Peak Burst Size. Measured in bytes, the PBS is associated with the PIR and is used to identify packets that
exceed the normal boundaries of packet size. The PBS should be configured to accept the biggest IP packet that is expected
in the IP flow.
srTCM – Single Rate Three Color Marker. This, along with the trTCM, are two methods available on the switch for metering and
marking packet flow. The srTCM marks its IP packet flow based on the configured CBS and EBS. A packet flow that does not reach
the CBS is marked green, if it exceeds the CBS but not the EBS its marked yellow, and if it exceeds the EBS its marked red.
CBS – Committed Burst Size. Measured in bytes, the CBS is associated with the CIR and is used to identify packets that
exceed the normal boundaries of packet size. The CBS should be configured to accept the biggest IP packet that is expected
in the IP flow.
EBS – Excess Burst Size. Measured in bytes, the EBS is associated with the CIR and is used to identify packets that exceed
the boundaries of the CBS packet size. The EBS is to be configured for an equal or larger rate than the CBS.
DSCP – Differentiated Services Code Point. The part of the packet header where the color will be added. Users may change the
DSCP field of incoming packets.
The ACL Flow Meter function will allow users to color code IP packet flows based on the rate of incoming packets. Users have two
types of Flow metering to choose from, trTCM and srTCM, as explained previously. When a packet flow is placed in a color code,
the user can choose what to do with packets that have exceeded that color-coded rate.
Green – When an IP flow is in the green mode, its configurable parameters can be set in the Conform field, where the packets can
have their DSCP field changed. This is an acceptable flow rate for the ACL Flow Meter function.
Yellow – When an IP flow is in the yellow mode, its configurable parameters can be set in the Exceed field. Users may choose to
either Permit or Drop exceeded packets. Users may also choose to change the DSCP field of the packets.
Red – When an IP flow is in the red mode, its configurable parameters can be set in the Exceed field. Users may choose to either
Permit or Drop exceeded packets. Users may also choose to change the DSCP field of the packets.
Users may also choose to count exceeded packets by clicking the Counter check box. If the counter is enabled, the counter setting in
the access profile will be disabled.
The ACL Flow Meter commands in the Command Line Interface (CLI) are listed (along with the appropriate parameters) in the
following table.