Pbb Qos - Alcatel-Lucent 7750 SR Manual

Os services guide

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PBB Features

PBB QoS

For PBB encapsulation, the configuration used for DE and dot1p in SAP and SDP policies applies

to the related bits in both backbone dot1q (BTAG) and ITAG fields.

The following QoS processing rules apply for PBB B-VPLS SAPs and SDPs:

B-VPLS SAP ingress

B-VPLS SAP egress

B-VPLS SDP (network) ingress policy

B-VPLS SDP (network) egress policy

If dot1p, DE based classification is enabled, the BTAG fields will be used by default to

evaluate the internal forwarding class (fc) and discard profile if there is a BTAG field. The

802.1ah ITAG will be used only if the BTAG is absent (null SAP).

If either one of the dot1p or DE based classification is not explicitly enabled or the packets

are untagged then the default fc and profile is assigned.

If the sap-egress policy for the SAP contains an fc to dot1p/de mapping, this entry is used

to set the dot1p and DE bits from the BTAG of the frame going out from the SAP. The

same applies for the ITAG on frames originated locally from an I-VPLS. The mapping

does not have any effect on the ITAG of frames transiting the B-VPLS.

If no explicit mapping exists, the related dot1p DE bits are set to zero on both ITAG and

BTAG if the frame is originated locally from an I-VPLS. If the frame is transiting the B-

VPLS the ITAG stays unchanged, the BTAG is set according to the type of ingress SAP.

→ If the ingress SAP is tagged, the values of the dot1p, DE bits are preserved in the

BTAG going out on the egress SAP.

→ If the ingress SAP is untagged, the dot1p, DE bits are set to zero in the BTAG going

out on the egress SAP.

QoS policies for dot1p and DE bits apply only for the outer VLAN ID: this is the VLAN

ID associated with the link layer and not the PBB BTAG. As a result, the dot1p DE bits

will be checked if an outer VLAN ID exists in the packets ingressing the SDP. If that

VLAN ID is absent, nothing above the pseudowire SL will be checked - for example, no

dot1p bits in the BTAG or ITAG will be checked. It is expected that the EXP bits will be

used to transport QoS information across the MPLS backbone and into the PEs.

When building PBB packets originating from a local I-VPLS, the BTAG and ITAG values

(dot1p, DE bits) will be set according to the network egress policy. The same applies for

newly added BTAG (VLAN mode pseudowires) in a packet transiting the B-VPLS (SAP/

7750 SR OS Services Guide