BS ISO/IEC 13871:1995

Foreword
Introduction
1 Scope
2 Normative references
3 Definitions
4 Symbols and Abbreviations
5 Selection of ISO/IEC 13871 or ITU-T H.224 aggregation
    procedures
6 Basic Principles
    6.1 Modes of operation
    6.2 Frame Structure
          6.2.1 Bit Ordering
          6.2.2 Frame Alignment Word (FAW)
          6.2.3 Frame Count (FC)
          6.2.4 Information Channel (IC)
          6.2.5 Cyclic Redundancy Check (CRC)
          6.2.6 Distribution of Overhead Octets
    6.3 Overall Frame Alignment
    6.4 Description of CRC4 procedure
          6.4.1 Computation of the CRC4 bits
                  6.4.1.1 Multiplication and division
                            process
                  6.4.1.2 Encoding procedure
                  6.4.1.3 Decoding procedure
          6.4.2 Consequent actions
                  6.4.2.1 Enabling and Disabling the
                            CRC procedures
                  6.4.2.2 Action on bit E
                  6.4.2.3 Monitoring for error performance
7 Description of the Information Channel
    7.1 Information Channel Frame
          7.1.1 Rate Multiplier and Subrate Multiplier
                  Calculation and Operation
    7.2 Information Channel (IC) synchronization
    7.3 Transmission and Recognition of an Information
          Channel Frame
8 Procedures
    8.1 Call Setup
          8.1.1 Initial Channel Setup
          8.1.2 Additional Channel Setup
          8.1.3 Delay Equalization
          8.1.4 Timeout Conditions
    8.2 Adding Bandwidth to an Existing Call
          8.2.1 Negotiation (Calling Endpoint Initiated)
          8.2.2 Negotiation (Answering Endpoint Initiated)
          8.2.3 Additional Channel Setup
          8.2.4 Timeout Conditions
    8.3 Deleting Bandwidth from an Existing Call
          8.3.1 Calling Endpoint Initiated
          8.3.2 Answering Endpoint Initiated
          8.3.3 Timeout Conditions
    8.4 Collision Resolution
    8.5 Call Disconnection
          8.5.1 Calling Endpoint Initiated
          8.5.2 Answering Endpoint Initiated
          8.5.3 Timeout Conditions
    8.6 Remote Loopback
          8.6.1 Timeout Conditions
    8.7 Remote Loopback
          8.7.1 Loss of Channel (Other Than Call Setup)
          8.7.2 Loss of Delay Equalization
9 Transport Mode Operation
    9.1 Non Aggregating Unit Calling Aggregating Unit
    9.2 Aggregating Unit Calling Non Aggregating Unit
Annexes
A RMULT and SUBMULT Values
    A.1 Bearer Channel Rate (BCR) = 56 kbit/s
    A.2 Bearer Channel Rate (BCR) = 64 kbit/s
B Manufacturer's Identifiers
C Phone Number Length Extension
D State Machine Description of Channel Aggregation
    Control
    D.1 Reference Architecture
    D.2 State Definitions
          D.2.1 DE Negotiation Control
          D.2.2 DEQ MULTIFRAME CONTROL States
    D.3 Messages and Events
          D.3.1 Information Channel Messages
          D.3.2 DEQ Negotiation Control to Call Control
                  Messages
          D.3.3 DEQ Negotiation Control to DEQ Multiframe
                  Control Primitives
    D.4 Timers
    D.5 State Transition Diagrams
          D.5.1 DEQ Negotiation Control
          D.5.2 DEQ Multiframe Control
   D.6 SDL Diagrams
          D.6.1 DEQ Negotiation Control
          D.6.2 DEQ Multiframe Control

Specifies a set of methods collectively known as 'Digital Channel Aggregation', which are used to provide an aggregated bearer service.

This International Standard defines a set of procedures collectively called \'Digital Channel Aggregation\', which are used in the provision of an aggregated bearer service. Digital channel aggregation involves a means for the combination of multiple switched or unswitched 56kbit/s or 64kbit/s digital communications channels across one or more public and/or private networks into higher bandwidth digital bi-directional channels between Channel Aggregation Units (CAUs) serving terminal applications at network endpoints. Figure1 below illustrates a typical channel aggregation scenario. Figure1 Channel Aggregation Scenario In defining the channel aggregation procedures, this International Standard sets out the means used by a CAU to establish the parameters to be used for the aggregated connection synchronise and align multiple communications channels to maintain the bit sequence integrity of the aggregated bandwidth across the network(s) optionally monitor data transfer throughout a call to detect failure modes institute failure recovery procedures optionally dynamically vary the bandwidth on demand during a call. The channel aggregation procedures above are defined at the interface between the CAU and the network in terms of the frame structure and information messages applied to individual communications channels. Not defined by this International Standard are the call control procedures used to establish and disconnect the individual communications channels that make up the higher bandwidth connections the higher level protocols or applications that use the channel aggregation services the frame structure on the individual communications channels at the physical interface between the CAU and the network as required for \'normal\' 56kbit/s or 64kbit/s bearer services as opposed to aggregated bearer services the electrical characteristics of the individual communications channels at the physical interface between the CAU and the network.