This Recommendation
specifies a bearer service category that provides the unrestricted transfer
(without alteration) of user information in a packetized manner over a virtual
circuit within a B- or D-channel at the S/T reference point. Signalling
information for virtual call and/or possibly OAM information for permanent
virtual circuit services are transferred via B- or D-channels as described in
Recommendation I.462 (X.31).