Layer 1 & Layer 2 Protocols
• 7-1 •
The H.110 Basic Rate ISDN Board
7.0 Layer 1 & Layer 2 Protocols
Basic Rate ISDN conforms to a model defined in a set of standards (I.430,
Q.921, Q.931 etc.) that is composed of a number of layers dealing with the
physical interface, peer to peer signaling and call control. The Infinity
Series H.110 Basic Rate ISDN Board provides most of the control over the
first two layers and optionally provides an interface to deal with the details
of the third or call control layer. This section will give a brief description
of the first two layers and how they relate to the inter-workings of the
board and the application. It is not meant as a exhaustive reference or
definition. For this, the reader is referred to the relevant specifications or
Bellcore documents.
7.1 Layer 1
The physical characteristics of the Basic Rate Interface are defined by I.430
and are referred to as Layer 1. Layer 1 deals with the functions of timing
and synchronization. It also provides the following services,
activation/deactivation, D-channel access for signaling, transmission of the
B and D channels, and Layer 1 status indication to Layer 2.
On the H.110 Basic Rate ISDN Board, the details of Layer 1 operation are
carried out by the hardware and the on board processor and are largely
hidden from the application. However, error messages will be sent to
indicate a change of status that might affect the operation of the interface.
Examples are the loss or restoration of synchronization. Details of these
messages may be found in Section 10.2.
Activation, deactivation, and synchronization are achieved through the
exchange of bit specific bit patterns referred to as INFO signals. These
are: