Rec. UIT-T G.708 (1991) – NETWORK NODE INTERFACE FOR THE SYNCHRONOUS DIGITAL HIERARCHY
FOREWORD
1 Location of network-node interface (NNI)
2 Basic multiplexing principle and multiplexing elements
    2.1 General
    2.2 Definitions
        2.2.1 synchronous digital hierarchy (SDH)
        2.2.2 synchronous transport module (STM)
        2.2.3 virtual container (VC)
        2.2.4 administrative unit (AU)
        2.2.5 tributary unit (TU)
        2.2.6 container: C-n (n = 1-4)
        2.2.7 network-node interface (NNI)
        2.2.8 pointer
        2.2.9 concatenation
        2.2.10 mapping synchronous digital hierarchy
        2.2.11 multiplexing synchronous digital hierarchy
        2.2.12 aligning synchronous digital hierarchy
3 Frame structure
    3.1 Basic frame structure
    3.2 Section overhead
    3.3 Administrative unit pointers
    3.4 Administrative units in the STM-N
4 Interconnection of STM-Ns
5 Overhead functions
    5.1 Types of overhead
        5.1.1 Section overhead (SOH)
        5.1.2 Virtual container path overhead VC (POH)
    5.2 SOH descriptions
        5.2.1 SOH bytes location
        5.2.2 SOH bytes description
6 Physical specification of the NNI
ANNEX A – Alphabetical list of abbreviations used in this Recommendation