val of information stored in infor- mation centres (usually) provided for public use. Connectionless data service aspects: Distribution services are sub-divided into those: Can be supported in B-ISDN. 1. Without user individual presentation control, and includes 1. Indirectly via a B-ISDN connection-oriented service broadcast services. Continuous information flow from central 2. Directly via a B-ISDN connectionless service (for further source to authorised receivers attached to the network. User has study). no control over start and order of presentation. 2. With user individual presentation control, information from Interworking aspects: central source to large number of users, provided as sequence of information entities with cyclic repetition. User can control Services normally available from narrow-band interfaces will also start and order of presentation. be available from broadband interfaces. Standards for ATM 41/11 Signalling aspects: 9. VP Connection (VPC): concatenation of VP links. Extends between two VPC endpoints (more than two for point to multi- A number of service-based signalling capability requirements are point). Provided for user-user, user-network, network-network listed. information transfer. Cell sequence integrity is preserved by the ATM layer within a VCC. 41.4.4.3 Video coding aspects 10 VPC endpoint: where VCIs are originated, translated or termi- nated. When VCs are switched the VPC supporting the incom- The final section of the recommendation deals with video coding ing VC links must be terminated first and a new outgoing VPC aspects and argues for coordination of video coding studies with created. B-ISDN studies in order to minimise the number of video terminals needed to access a range of interactive and distribution video and The Physical Layer is also explored: still image based services. Minimising the number of coding tech- niques and matching them to network characteristics is key to this 1. Transmission path: extends between network elements that aim. Constant bit-rate and var