Verilink 9000 Series (34-00271) Product Manual - Manual (Page 211)

Configuration / Operation 189
NRZI
The NRZI parameter describes the encoding technique used at Layer 1. The selection
can be either non-return to zero (NRZ) or non-return to zero inverted (NRZI).
NRZ used what would be considered a normal coding scheme: a 1 bit represents a
high signal and a 0 bit represents a low signal.
NRZI uses a different encoding scheme: a 1 bit represents the continuation of the
current state, while a 0 bit is indicated by a change in state.
The selections are NRZ and NRZI.
Data link type
This parameter effects how the MultiPro platform interacts with data received on
this port. Three types of interaction are described below.
Tunneling. In tunneling mode, any frame received on this port is forwarded
through the network to its destination where it is sent exactly as it was received.
This means that all information, supervisory and unencumbered frames are sent
through the network. There is no local acknowledgment of frames.
SDLC. In SDLC mode, the anticipated Layer 2 protocol is SDLC and the MultiPro
unit acknowledges the frame locally, based on the calculation of the FCS. This
allows for greater throughout and reduces the amount of traffic generated by this
port on the network. This option has a second Port Parameter screen for Levels 2
and 3.
LAPB. The LAPB mode anticipates Layer 2 to be the LAPB derivative of HDLC
and performs local acknowledging and interaction, based on that protocol’s defined
characteristics. As with SDLC this allows for greater throughput and reduces traffic
on the network. This option has a second Port Parameter screen for Levels 2 and 3.
The selections are S (SDLC), L (LAPB), and T (TUNNEL).