VSC7440 datasheet(274/444 Pages) MICROSEMI

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Functional Descriptions

VMDS-10492 VSC7440 Datasheet Revision 4.2

257

The following table lists the registers associated with the frame loopback options.

Frame forwarding is changed if allowed by the current frame pipeline point and action. For more

information, see Rewriter Pipeline Handling, page 254.

The following table shows the pipeline action when the frame forwarding is changed.

The pipeline updating rules ensures that a REDIR or DISCARD decision cannot be changed at a later

pipeline point. A COPY may be changed at a later point to either a REDIR or DISCARD action.

•

If a copy is changed to a discard, the CPU still receives the frame copy.

•

If a copy is changed to a redirection, the CPU receives a copy and the frame is looped back or also

sent to the redirection queue.

When frames are copied or redirected the IFH is updated as described in the following table.

3.26.5.3 Egress Statistics Update

The rewriter does not have Egress Service Index (ESDX) and port-based counters of its own. Instead,

the egress statistic counters in XQS:STAT are used for all frame and byte counting. For more

information, see Statistics, page 230.

The following counters are available to the rewriter as frame and octet counters.

•

Per egress port: 2 × 8 + 1 = 17 counters (color × cell bus priority + abort)

Table 176 •

Frame Loopback Options

Description

Replication

ES0_CTRL.

ES0_FRM_LBK_CFG

Using ES0 it is possible to loop frames back to ANA with the

LOOP_ENA action.

If this bit is set, a frame can only be looped once by ES0.

None

Table 177 •

Pipeline Action Updates

Forwarding Selection

Pipeline Action Updates

NONE

Unchanged

COPY

Unchanged

REDIR

CPU redirection: XTR / XTR_UPMEP

Loopback frames: LBK_ASM

DISCARD

XTR / XTR_UPMEP

Table 178 •

Loopback IFH Updates

IFH Field

Updated by

FWD.SRC_PORT

COPY or REDIR. The frame source port is changed to the current destination port.

MISC.PIPELINE_PT

COPY or REDIR. The pipeline point in which the frame forwarding was updated.

MISC.PIPELINE_ACT

COPY or REDIR. The pipeline action assigned to the frame.

MISC.CPU_MASK

Any operation. A CPU copy may be generated by all forward selections.

FWD.DO_LBK

Rewriter loopback. This bit is set to indicate that the frame has been looped by the

REW. Can optionally be used to prevent multiple loops of the same frame.

FWD.UPDATE_FCS

VOP. Set by the VOP if a looped frame changed.

VSTAX.MISC.ISDX

VOP. The frame ISDX can be changed by the VOP.

VSTAX.QOS.DP

VOP. The DP level can be set to 0 by the VOP.

ENCAP.MPLS_TTL

VOP. The MPLS_TTL can be set to 1 by the VOP.

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