VSC7440 datasheet(273/444 Pages) MICROSEMI

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Functional Descriptions

VMDS-10492 VSC7440 Datasheet Revision 4.2

256

3.26.5.2 Frame Copy, Redirect, or Discard

Frame forwarding may be changed by ES0 action FWD_SEL, the MIP or the VOP. Changing frame

forwarding will update the frame pipeline point and action.

The following options are available to control frame forwarding.

•

No action. Do not change frame forwarding.

•

Copy frame to CPU via the loopback interface. The frame is looped back to the ANA where it is sent

to the CPU. The IFH of the CPU copy is modified to select a CPU queue. The frame is also

forwarded as normal to the destination port and can be modified by the normal rewriter operations.

•

Redirect frame to ANA via loopback interface. When doing frame loopbacks, the destination port of

the redirected frame will be left unchanged. The IFH of the frame is modified and the MAC

addresses may be swapped. Redirected frames may also be sent to a CPU queue. This can be

done as a standalone operation or together with the loopback frame. When redirecting, the frame is

only sent to the loopback interface and not to the original destination port.

•

Discard frame. The frame is terminated before transmission.

The following illustrations depicts options for frame forwarding.

Figure 78 •

Frame Forward Options

Inject

If a frame is injected in pipeline point N, the forwarding cannot be changed in

pipeline point N-1 and it will not be counted in the N-1 point. Logically the frame

does not exist in the N-1 point.

Example: A frame is injected in the REW_VRAP pipeline point (Pipeline point =

REW_VRAP, Action = INJ). The SW-MEP is configured to loop the same frame

in the pipeline point REW_SAT. The frame will not be looped, because it was

injected later in the pipeline (REW_VRAP > REW_SAT). The frame will not be

counted by the egress service statistics, which has a default location in the

REW_PORT_VOE pipeline point for injected frames.

Extract

If frame is extracted in pipeline point N the forwarding cannot be changed in

pipeline point N+1 and it will not be counted in the N+1 point. Logically the

frame does not exist in the N+1 point.

Example: A frame is extracted in the REW_IN_MIP pipeline point (Pipeline

point = REW_IN_MIP, Action = XTR). The SW-MEP is configured to loop the

same frame in the pipeline point REW_SAT. The frame will not be looped

because it has already been extracted earlier in the pipeline (REW_IN_MIP <

REW_SAT). The frame will not be counted by the egress service statistics,

which has a default location in the REW_OU_SW pipeline point for extracted

frames.

Table 175 •

Pipeline Point Updating Rules (continued)

Pipeline Action

Rule

IFH

Payload

From OQS

Rewriter

Changed

Payload

To DSM

No action or copy

IFH(1)

SA(2) DA(2)

Discard

Terminate

Payload

To LBK

Copy or redirect

1. The IFH is modified for looped frames.

2. MACs can be swapped for looped frames.

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