Figure 1 shows a specific use case. Keeping the same topology, an ingress PBB PE, a PBB core and an egress PBB PE, consider the generic use case where:
the packet arrives on the ingress PBB PE on an I-SAP or an I-SDP binding/PW and it is assigned to a PBB service instance (Epipe/IVPLS)
goes next through a PBB core (native Ethernet B-SAPs or PW/MPLS based B-SDP)
and finally, egresses at another PBB PE through a PBB service instance on either an I-SAP or I-SDP binding/PW.
Similar to the Ethernet-VLAN VC Type, the following packet processing steps apply for different scenarios.
Ingress PE, ingress I-SAP case with force-qtag-forwarding enabled under PBB Epipe or IVPLS
The qtag is inserted automatically right after C-MAC addresses; an ethertype value of 8100 is used.
Case 1: SAP type = null/dot1q default (1/1/1 or 1/1/1.*) so there is no service delimiting tag used and stripped on the ingress side.
VLAN and Dot1p+DE bits on the inserted qtag are set to zero regardless of ingress QoS policy
Case 2: SAP type = dot1q or qinq default (1/1/1.100 or 1/1/1.100.*) so there is a service delimiting tag used and stripped.
The service delimiting qtag (dot1p + DE bits and VLAN) is copied as is in the inserted qtag.
Case 3: SAP type = qinq (1/1/1.100.10) so there are two service delimiting tags used and stripped.
The service delimiting qtag (VLAN and dot1p + DE bits) is copied as is from the inner tag in the inserted qtag.
Ingress PE, ingress I-SDP/PW case with force-qtag-forwarding enabled under PBB Epipe or IVPLS
The qtag is inserted automatically right after C-MAC addresses; an ethertype value of 8100 is used.
Case 1: SDP vc-type = Ethernet (force-vlan-vc-forwarding= not supported for I-PW) so there is no service delimiting tag stripped on the ingress side.
VLAN and Dot1p+DE bits on the inserted qtag are set to zero regardless of ingress QoS policy
Case 2: SDP vc-type = Ethernet VLAN so there is a service delimiting tag stripped.
VLAN and Dot1p + DE bits on the inserted qtag are preserved from the service delimiting tag.
PBB packets are tunneled through the core the same way for native ETH/MPLS cases.
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 C-MAC 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.
Egress PE, egress I-SDP case with force-qtag-forwarding enabled under PBB Epipe or IVPLS
Case 1: I-SDP vc-type = Ethernet VLAN so there is service delimiting tag added after PW encapsulation.
The dot1p+DE bits from the qtag received over the PBB core side are copied to the qtag added on the I-SDP.
The VLAN value in the qtag may change to match the provisioned value for the I-SDP configuration.
Case 2: I-SDP vc-type = Ethernet (force-vlan-vc-forwarding=not supported for I-SDPs) so there is no service delimiting tag added on egress PW.
The qtag received over the PBB core is stripped and the QoS information is lost.