The present document specifies the physical, procedural and protocol requirements for interfaces at the VB5.2 reference
point between an Access Network (AN) and a Service Node (SN). The VB5.2 reference point provides flexible
(provisioned) virtual path (VP) link allocation and flexible (provisioned) virtual channel (VC) link allocation (controlled
by the Q3 interfaces) as well as on-demand VC link allocation controlled by the SN via the broadband bearer connection
control (B-BCC) protocol. That is, the VB5.2 reference point is a superset of the VB5.1 reference point, enabling
on-demand VC link allocation in the AN and across the VB5 reference point via the additional B-BCC function.
The following B-ISDN customer access types with the general user network interface (UNI) characteristics defined in
ITU-T Recommendation I.432.1 [33] are supported:
a) B-ISDN accesses with a UNI at 155 520 kbit/s and 622 080 kbit/s according to
ITU-T Recommendation I.432.2 [34], i.e.:
1) SDH based according to ETS 300 300 [4];
2) Cell based according to ETS 300 299 [3].
b) B-ISDN access with a PDH based UNI at 1 544 kbit/s and 2 048 kbit/s according to
ITU-T Recommendation I.432.3 [35].
c) B-ISDN accesses with a UNI at 51 840 kbit/s or 25 600 kbit/s according to
ITU-T Recommendations I.432.4 [36] and I.432.5 [37].
B-ISDN accesses with a UNI according to future ENs and/or ITU-T Recommendations may require additional
functionality at the VB5.2 reference point.
In order to provide for a migration from narrowband to broadband access network and service node arrangements, also
narrowband access types as specified for:
- V5.1 interface according to ETS 300 324-1 [6]/ITU-T Recommendation G.964 [20]; and/or
- V5.2 interface according to ETS 300 347-1 [7]/ITU-T Recommendation G.965 [21],
are also supported according to the integration scenario given in Appendix III.2.2 of
ITU-T Recommendation G.902 [19], using a circuit emul (...abbreviated)