Network Queue QoS Policies
Quality of Service Guide 169
The packet-byte-offset command accepts either add or subtract as valid keywords which define
whether bytes are being added or removed from each packet traversing the queue. Up to 20 bytes may
be added to the packet and up to 43 bytes may be removed from the packet. An example use case for
subtracting bytes from each packet is an IP based accounting function. Given a Dot1Q encapsulation,
the command packet-byte-offset subtract 14 would remove the DLC header and the Dot1Q header
from the size of each packet for accounting functions only. The 14 bytes are not actually removed from
the packet, only the accounting size of the packet is affected.
As inferred above, the variable accounting size offered by the packet-byte-offset command is targeted
at the queue and queue group level. When the queue group represents the last-mile bandwidth
constraints for a subscriber, the offset allows the HSMDA queue group to provide an accurate
accounting to prevent overrun and underrun conditions for the subscriber. The accounting size of the
packet is ignored by the secondary shapers, the scheduling priority level shapers and the scheduler
maximum rate. The actual on-the-wire frame size is used for these functions to allow an accurate
representation of the behavior of the subscribers packets on an Ethernet aggregation network.
The packet-byte-offset value may be overridden for the HSMDA queue at the network queue level.
The no form of the command removes any accounting size changes to packets handled by the queue.
The command does not affect overrides that may exist on an associated with the queue.
This command only applies to the 7450 ESS and 7750 SR.
Parameters add add-bytes — Indicates that the byte value should be added to the packet for queue and queue
group level accounting functions. Either the add or subtract keyword must be specified. The
corresponding byte value must be specified when executing the packet-byte-offset command.
The add keyword is mutually exclusive with the subtract keyword.
Values 1 to 31
subtract sub-bytes — Indicates that the byte value should be subtracted from the packet for queue
and queue group level accounting functions. The subtract keyword is mutually exclusive
with the add keyword. Either the add or subtract keyword must be specified. The
corresponding byte value must be specified when executing the packet-byte-offset command.
The minimum resulting packet size used by the system is 64 bytes with an HS-MDA.
Values 1 to 64
wrr-policy
Syntax wrr-policy hsmda-wrr-policy-name
no wrr-policy
Context config>qos>network-queue>egress-hsmda
Description This command associates an existing HSMDA weighted-round-robin (WRR) scheduling loop policy
to the HSMDA queue. This command only applies to the 7450 ESS and 7750 SR.
Parameters hsmda-wrr-policy-name — Specifies the existing HSMDA WRR policy name to associate to the
queue.
To Next Page
Loading...
