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DGS-3600 Series Layer 3 Gigabit Ethernet Managed Switch CLI Manual
84
10
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 CIR 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.