PBB Features
Page 812 7750 SR OS Services Guide
• Egress PE, egress I-SAP case with force-qtag-forwarding enabled under PBB Epipe or
VPLS
→ The egress QoS policy (FC->dot1p+DE bits) is used to determine the QoS settings of
the added QTAGs. If it required to preserve the ingress QoS, no egress policy should
be added.
− If QinQ SAP is used, at least qinq-mark-top-only option must be enabled to
preserve the CTAG.
→ The “core QTAG” (core = received over the PBB core, 1st after CMAC addresses) is
always removed after QoS information is extracted.
− If no force-qtag-forwarding is used at egress PE, the inserted QTAG is
maintained.
→ If egress SAP is on the ingress PE, then the dot1p+DE value is read directly from the
procedures described in Ingress PE, ingress I-SAP and Ingress PE, ingress I-SDP/PW
cases. The use cases below still apply.
→ Case 1: SAP type = null/dot1q default (2/2/2 or 2/2/2.*) so there is no service
delimiting tag added on the egress side.
− Dot1p+DE bits and the VLAN value contained in the QTAG are ignored.
→ Case 2: SAP type = dot1q/qinq default (3/1/1.300 or 3/1/1.300.*) so a service
delimiting tag is added on egress
− The FC->dot1p, DE bit entries in the SAP egress QoS policy are applied.
− If there are no such entries, then the values of the dot1p+DE bits from the stripped
QTAG are used.
→ Case 3: SAP type = qinq (3//1/1.300.30) so two service delimiting tags are added on
egress
− The FC->dot1p, DE bit entries in the SAP egress QoS policy are applied.
−If the “qinq-mark-top-only” command under vpls>sap>egress is not enabled
(default), the policy is applied to both service delimiting tags.
−If the qinq-mark-top-only command is enabled, the policy is applied only to the
outer service delimiting tag.
− On the tags where the egress QoS policies do not apply the values of the
dot1p+DE bits from the stripped QTAG are used.
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