Connection-oriented Ethernet - PBT and PBB

PBT and PBB

Provider Backbone Transport (PBT) is connection-oriented switch operation scheme and network management architecture. PBT was invented by British Telecom (BT) and developed by Nortel (now Avaya). It defines methods to emulate connection-oriented networks by providing "nailed-up" trunks through a packet-switched network. Key data-plane differences from PBB include the static configuration of forwarding tables within Ethernet switches, dropping of multicast packets and the prevention of "flooding" of frames to unknown destination addresses. Configuration is performed by a centralized management server like in SDH networks, though in the future a control plane may be added. PBT has been presented to IEEE802 and a new project has been approved to standardize it under the name of Provider Backbone Bridge Traffic Engineering (PBB-TE) (IEEE 802.1Qay), a modification to PBB.

Provider Backbone Bridges (PBB) is an Ethernet data-plane technology invented in 2004 by Nortel Networks (now Avaya). It is sometimes known as MAC-in-MAC because it involves encapsulating an Ethernet datagram inside another one with new source and destination addresses (termed B-SA and B-DA). IEEE802 is standardizing the technology as (IEEE 802.1ah), currently under development. PBB is the original data-plane chosen by British Telecom for their new PBT-based Ethernet transport.

PBB can support point-to-point, point-to-multipoint and multipoint-to-multipoint networks. PBT focuses on point-to-point connectivity, and may be capable of extension to point-to-multipoint, a key technology for advanced data applications such as IPTV. PBT avoids trying to address multipoint-to-multipoint networking, as in the opinion of some of its supporters guaranteed levels of service in multipoint-to-multipoint networks are impossible.

Additionally Ethernet is being reinforced with operations, administration, and maintenance (OAM) capabilities through the work of various standard bodies (IEEE 802.1ag, ITU-T Y.1731 and G.8021, IEEE 802.3ah).

PBT/PBB equipment leverages economies of scale inherent in Ethernet promising about 30%–40% cheaper solutions compared to T-MPLS equipment with identical features and capabilities making PBT a better overall return on investment.