1. Frame Metadata description
When the frames are forwarded through the switch they carry a set of metadata.
First, this metadata is assigned default values and in different blocks, these values can be changed.
The values have different purposes that can have an influence on how the frame is treated,
like what TCAM entries it hit, how it is policed and shaped, what special function HW resources
it will hit, and how the pushed tag will look like on egress
In the following, it will be outlined what the metadata is, how it is assigned, and how it is used.
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Classified VID.
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Classified Priority.
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Classified DPL (Drop Precedence Level).
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Classified PCP.
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Classified DEI.
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FRER HW pointer.
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PSFP HW pointer.
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PSFP policer HW pointer.
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ACL policer HW pointer.
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Queue ID.
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Policy Association Group (PAG)
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Ingress Service Descriptor (ISDX)
Not all metadata is supported in all TCAMs on all switches, so you should consult the datasheet for the details.
1.1. Classified VID.
Assignment:
Frames classified as untagged is assigned the bridge device default VID as classified VID.
Frames classified as tagged is assigned VID from the tag as classified VID.
Frames hitting a TC filter can have the classified VID changed.
Use:
Frames can hit a TC filter that has classified VID as key.
Frames are forwarded in a created bridge VLAN based on classified VID.
Frames can have a tag pushed with classified VID as the Tag VID on egress.
1.2. Classified Priority.
Assignment:
All Frames are assigned the bridge device default Priority as classified Priority.
Frames classified as tagged can have PCP from the tag mapped to a classified Priority.
IP frames can have PSFP value from frame mapped to a classified Priority.
Frames hitting a TC filter can have the classified Priority changed.
Use:
By default, the classified Priority is set to Queue ID that is used to decide which
queue in the Queue System the frame is entering.
On egress, frames can be scheduled and shaped based on classified Priority.
On egress, a tag pushed can have classified Priority mapped to Tag PCP and DEI.
1.3. Classified DPL.
Assignment:
All Frames are assigned the bridge device default DPL as classified DPL.
Frames classified as tagged can have DEI from the tag mapped to a classified DPL.
IP frames can have PSFP value from frame mapped to a classified DPL.
Frames hitting a TC filter can have the classified DPL changed.
Use:
The DPL is used in the queue system to decide what frames to drop when congestion happens.
DPL is the color of the frame that can be used by a color aware policer.
On egress, a tag pushed can have classified DPL mapped to Tag PCP and DEI.
1.4. Classified PCP.
Assignment:
All Frames are assigned the bridge device default PCP as classified Priority.
Frames classified as tagged will have PCP from the tag as the classified PCP.
Use:
On egress, a tag pushed can have classified PCP as Tag PCP.
1.5. Classified DEI.
Assignment:
All Frames are assigned the bridge device default DEI as classified DEI.
Frames classified as tagged will have DEI from the tag as the classified DEI.
Use:
On egress, a tag pushed can have classified DEI as Tag DEI.
1.6. FRER HW pointer.
Assignment:
Frames hitting a VCAP rule can have a FRER HW pointer assigned.
Use:
Frames will be handled by the configured FRER HW instance.
1.7. PSFP HW pointer.
Assignment:
Frames hitting a VCAP rule can have a PSFP HW pointer assigned.
Use:
Frames will be handled by the configured PSFP HW instance.
1.8. PSFP policer HW pointer.
Assignment:
Frames hitting a VCAP rule can have a PSFP policer HW pointer assigned.
Use:
Frame will be handled by the configured PSFP policer HW instance.
1.9. ACL policer HW pointer.
Assignment:
Frames can hit a TC filter that has a reference to a separately configured policer configuration.
This reference is carried in the metadata as an ACL policer HW pointer.
The TC filter can also specify the policer configuration explicitly.
In this case, a policer configuration is automatically created and a reference to that is carried
in the metadata as an ACL policer HW pointer.
Use:
Frames will be handled by the policer configuration pointed to by the ACL policer HW instance.
1.10. Queue ID.
Assignment:
By default, the classified Priority is set to Queue ID.
Change of this by PSFP is currently not supported.
Use:
In the Queue System, this is used to decide what queue the frame is entering.