de a Quality of service defined by par- ameters such as cell loss ratio, cell delay variation and preserve Glossary of terms and definitions, organised under two headings: cell sequence integrity. VCC traffic parameters will require services; and interfaces, channels and transfer modes. These are negotiation and VCC usage will be monitored. (Figure 41.10.) kept updated to remain in line with the evolution of terminology used in the other recommendations in the series dealing with broad- Virtual channel connection band. 41.4.2 Broadband aspects of ISDN Statement of the basic principles of the broadband aspects of ISDN. Establishes ATM as the transfer mode for implementing B-ISDN and identifies certain specific advantages: 1. Flexibility of network access. VP ATM VC/VP ATM 2. Dynamic bandwidth allocation on demand: fine degree of gra- Switch Switch nularity. Virtual path connection Virtual path 3. Flexible bearer capability allocation; easy provision of semi- permanent connections. 4. Independence from the means of transport at the physical layer. Figure 41.10 Types of ATM layer connection (Based on 41.4.3 I.150: B-ISDN ATM functional Fig. 2/1.150) characteristics Describes how VCCs may be established and released citing four methods at the UNI: by subscription (semi-permanent Describes the basic principles of ATM and addresses the functions connection set up by management); using a meta-signalling VC of the ATM layer: to establish a signalling VC; by using a signalling VC for user/network signalling; similarly for user/user signalling. 1. Describes how the physical layer connection can carry a num- Defines a virtual path connection (VPC) as a concatenation of ber of virtual paths distinguished by the 'VPI' field: also how virtual path links that extends between the point where VCI 41/10 Asynchronous Transfer Mode values are assigned/translated/removed VPC characteristics The recommendation deals with each class in detail, describing are broadly as for VCCs except that VPCs are only set up on a the type of informat