Transparency Of Customer Qos Indication Through Pbb Backbone; Figure 120: Pcp, De Bits Transparency In Pbb - Alcatel-Lucent 7750 SR Manual

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Transparency of Customer QoS Indication through PBB Backbone

Similar to PW transport, operators want to allow their customers to preserve all eight (8) Ethernet
COS markings (three dot1p bits) and the discard eligibility indication (DE bit) while transiting
through a PBB backbone.
This means any customer COS marking on the packets inbound to the ingress SAP must be
preserved when going out on the egress SAP at the remote PBB PE even if the customer VLAN
tag is used for SAP identification at the ingress.
A solution to the above requirements is depicted in
The PBB BVPLS is represented by the blue pipe in the middle with its associated COS
represented through both the service (I-tag) and tunnel COS (BVID dot1p+DE or PW EXP bits).
The customer COS is contained in the orange dot1q VLAN tags managed in the customer
domains. There may be one (CVID) or two (CVID, SVID) tags used to provide service
classification at the SAP. IVPLS or PBB Epipe instances (orange triangles) are used to provide a
Carrier-of-Carrier service.
As the VLAN tags are stripped at the ingress SAP and added back at the egress SAP, the PBB
implementation must provide a way to maintain the customer QoS marking. This is done using a
force-qtag-forwarding configuration on a per IVPLS/Epipe basis under the node specifying the
uplink to the related BVPLS. When force-qtag-forwarding is enabled, a new VLAN tag is added
7750 SR OS Services Guide
SDP to SDP). Note that if either dot1p or DE based classification is not explicitly enabled
in the CLI, the values from the default fc to dot1p, DE mapping are assumed.
Dot1p, DE bits for existing BTAGs will remain unchanged - for example, applicable to
packets transiting the B-VPLS and going out on SDP.

Figure 120: PCP, DE bits transparency in PBB

Virtual Private LAN Services
Figure 120.
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