Quality of Service Guide Service Egress and Ingress QoS Policies
Edition: 01 3HE 11014 AAAC TQZZA 291
packet-byte-offset
Syntax packet-byte-offset [add bytes | subtract bytes | none]
no packet-byte-offset
Context config>qos>sap-egress
config>qos>sap-egress>queue
config>qos>sap-ingress
config>qos>sap-ingress>queue
Description This command is used to modify the size of the packet that schedulers operate on.
Modification only impacts schedulers and queue statistics. The actual packet size is not
modified, nor can it be. Only the size used by the schedulers to determine the scheduling is
changed. The packet-byte-offset command is meant to be a mechanism that can be used
to compensate for downstream encapsulation or header removal. The scheduling rates are
affected by the offset, as well as the statistics (accounting) associated with the queue. The
packet-byte-offset command does not affect port-level and
service-level statistics. It only affects the queue statistics. The network-queue policy applies
in both the ingress and egress directions.
The add and subtract keywords are mutually exclusive. Either add, subtract, or none must
be specified.
There are three possible modes of packet-byte-offset operation:
• no packet-byte-offset — enables legacy behavior so that no modification is performed
• packet-byte-offset — automatic adjustment mode. Rates apply to packets based on
the received packet size at ingress (this is also known as packet size on the wire, less
the
Layer-1 headers, the inter-frame GAP and the Preamble) and to the transmitted packet
size at egress, which includes 4-bytes of Ethernet FCS. At ingress, all internal headers
and associated service headers are discounted during scheduling operation. At egress
4-bytes are added to accommodate for Ethernet FCS.
• packet-byte-offset [add bytes | subtract bytes]— automatic correction followed by
addition or subtraction of a specified number of bytes. This command first performs the
packet-byte-offset operation as captured above and then adds or subtracts a certain
number of bytes. Rates apply to packets based on the size of the packet at the ingress
or egress port plus or minus an offset.
Packet byte offset configuration can be applied at the policy level, in which case it applies to
all of the queues within the policy, or at the individual queue level so that it applies only to a
specific queue.
The no version of this command enables legacy 7705 SAR behavior where the queue rates
are relative to the packet size with the internal fabric header added, but without the FCS.
To Next Page
Loading...
