provider backbone transport (Metro) (PBT)

Provider Backbone Transport (PBT) is a low-cost alternative to Multi-Protocol Label Switching(MPLS) in urban and metro networks. PBT is used as an Ethernet tunneling technique in Carrier Ethernet Transport( CET) for connection-oriented tunneling. PBT allows transport paths to be configured via network and service management over the truncated Ethernet transport.

Provider Backbone Transport provides for explicit configuration of punt-to-point( P2P) connections by the administrator and offloads certain routing algorithms to the control plane of metro switches. Backup connections can also be configured to take over in the event of a failure.

Monitoring of PBT connections is based on IEEE 802.1ag, the Ethernet OAM, Operation, Administration, and Maintenance, which deals with fault management. This involves continuous connection checks on the regular and backup paths. This is done by regularly sending out so-called CC frames, Connectivity Check, between the connection end points. If a certain number of CC messages fail to arrive, the traffic is routed via the alternative path.

Provider Backbone Transport was developed by Nortel under the name Provider Backbone Bridging withTraffic Engineering( PBB-TE) and submitted to IEEE for standardization, where it is treated as a subset of 802.1ag for error monitoringand 802.1ah, Provider Backbone Bridges (PBB).