VSC7440 datasheet(135/444 Pages) MICROSEMI

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Functional Descriptions

VMDS-10492 VSC7440 Datasheet Revision 4.2

118

The following fields in the VCAP CLM action can be used to move to the next protocol layer:

•

NXT_OFFSET_FROM_TYPE.

Move frame pointer past current protocol layer (Ethernet and/or IP). The actual number of bytes the

frame pointer is moved may vary depending on content of the current protocol layer, such as the

number of VLAN tags or IPv4 options.

•

NXT_NORM_W16_OFFSET.

Move frame pointer a number of 16 bit words. If both NXT_OFFSET_FROM_TYPE and

NXT_NORM_W16_OFFSET are specified, then frame pointer is first moved based on

NXT_OFFSET_FROM_TYPE and afterwards moved further into the frame based on

NXT_NORM_W16_OFFSET.

•

NXT_TYPE_AFTER_OFFSET.

Specify protocol layer at new frame pointer position.

For more information about VCAP CLM action fields, see Table 65, page 92.

Each VCAP CLM lookup can at most move the frame pointer 66 bytes. The following pseudo code shows

the algorithm used to update frame_ptr and frame_type upon each VCPA_CLM lookup.

// ======================================================================

// ANA_CL: VCAP CLM Frame Pointer and Frame Type Update

// Update frame_ptr and frame_type upon VCAP CLM lookup.

// Prior to first VCAP CLM lookup frame_ptr is initialized to 0 and

// frame_type is set to ETH.

// The algorithm is run after each VCAP CLM lookup.

// ----------------------------------------------------------------------

// Function for updating

frame_ptr

frame_type

// based on action from VCAP CLM lookup

void UpdateFramePtrAndType(

// VCAP CLM index. 0=First VCAP CLM lookup,

// 5=Last VCAP CLM lookup

clm_idx,

// Action from VCAP CLM lookup

// clm_action.vld is only set if

// VCAP CLM lookup was enabled.

clm_action,

// From ClmKeyFieldsMpls()

clm_key_fields_mpls,

)

{

int frame_ptr_current

= frame_ptr;

int frame_type_current = frame_type;

if (!clm_action.vld) return;

if (clm_action.nxt_offset_from_type > 0) {

// Move frame_ptr based on frame type

switch (clm_action.nxt_offset_from_type) {

case SKIP_ETH:

if (frame_type_current == ETH) {

// Move frame_ptr past DMAC, SMAC, 0-3 VLAN tags and EtherType

SkipLinkLayer(&frame_ptr);

}

break;

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