VLL Service Configuration Commands
Page 356 7750 SR OS Services Guide
frame based and always include the preamble, DLC header, payload and the CRC regardless of the
configured byte offset.
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 mentioned 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 subscriber’s packets on an Ethernet aggregation
network.
The packet-byte-offset value can be overridden for the HSMDA queue at the SAP or subscriber
profile level.
The no form of the command removes any accounting size changes to packets handled by the queue.
The command does not effect overrides that may exist on SAPs or subscriber profiles associated with
the queue.
Parameters add add-bytes — The add keyword is mutually exclusive with the subtract keyword. Either the add
or subtract keyword must be specified. The add keyword is used to indicate that the following
byte value should be added to the packet for queue and queue group level accounting functions.
The corresponding byte value must be specified when executing the packet-byte-offset
command.
Values 0 — 31
subtract sub-bytes — The subtract keyword is mutually exclusive with the add keyword. Either the
add or subtract keyword must be specified. The subtract keyword is used to indicate that the
following byte value should be subtracted from the packet for queue and queue group level
accounting functions. The corresponding byte value must be specified when executing the
packet-byte-offset command.
Values 1 — 32
queue
Syntax queue queue-id [create]
no queue queue-id
Context config>service>epipe>sap>egress>hsmda-queue-over
config>service>epipe>sap>ingress>hsmda-queue-over
config>service>ipipe>sap>egress>hsmda-queue-over
config>service>ipipe>sap>ingress>hsmda-queue-over
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