This section describes QoS policy propagation using BGP (QPPB) as it applies to VPRN, IES, and router interfaces. see the ‟Internet Enhanced Service” section in the 7450 ESS, 7750 SR, 7950 XRS, and VSR Layer 3 Services Guide: IES and VPRN and the ‟IP Router Configuration” section in the 7450 ESS, 7750 SR, 7950 XRS, and VSR Router Configuration Guide.
QoS policy propagation using BGP (QPPB) is a feature that allows a route to be installed in the routing table with a forwarding-class and priority so that packets matching the route can receive the associated QoS. The forwarding-class and priority associated with a BGP route are set using BGP import route policies. This feature is called QPPB, even though the feature name refers to BGP specifically. On SR OS, QPPB is supported for BGP (IPv4, IPv6, VPN-IPv4, VPN-IPv6), RIP, and static routes.
SAP ingress and network QoS policies can achieve the same result as QPPB (for example, by assigning a packet arriving on an IP interface to a specific forwarding-class and priority/profile, based on the source address or destination address of the packet). However, the effort involved in creating the QoS policies, keeping them up-to-date, and applying them across many nodes is much greater than with QPPB. In a typical application of QPPB, a BGP route is advertised with a BGP community attribute that conveys a specific QoS. Routers that receive the advertisement accept the route into their routing table and set the forwarding-class and priority of the route from the community attribute.