Enterasys Networks CSX6000 - Manual (Page 125)

Central Site Remote Access Switch 125
C ONFIGURING R ESOURCES AND L INES
Lines
L INE E NCODING
For Primary Rate lines only. Line encoding specifies the nature of the signals that are used to
represent binary one and zero at the physical layer. Two encoding methods are Alternate Mark
Inversion (AMI) and Bipolar 8 Zero Substitution (B8ZS). AMI as the encoding scheme implies that
the applications using the transmission line must guarantee a certain number of 1s in the signal to
help prevent a loss of synchronization in the network. This is possible if the voltage level of the
signal remains zero for too long a period of time (i.e., too many logical 0s in the transmitted data).
B8ZS enforces no such limits on the application using the transmission medium since it introduces
bipolar violations in the signal. These violations are in turn interpreted at the receiving end not as
errors, but simply as the substitution of a 1 for a 0 after certain number of consecutive 0s were
detected in the transmitted signal.
T1 S IGNALING M ETHOD
For primary rate lines only. The signaling method dictates how and where the call signaling is to
be carried. The methods currently available are: Common Channel and Robbed Bit Signaling.
C OMMON C HANNEL
In the Common Channel signaling case, one of the 24 channels of the PRI frame is devoted
to call control messaging.
R OBBED B IT S IGNALING
In the Robbed Bit Signaling method, 1 bit of each data channel is “robbed” in order to carry
the requisite signaling information. This method is only available for Digital Modem
resources.
Notes: Mixing RBS lines and Common Channel lines in a single CyberSWITCH will cause some
problems with outbound calls. A 64 Kbps data call may try to go out on the RBS line. The
WAN card controlling that line will reject the call, as will every other WAN card until a
card using a Common Channel line is tried.
The E1/R2 signaling method is specified under Line Characteristics, Framing Type .
L INE B UILD O UT
For primary rate lines only. No matter what the quality of the cabling employed in a network, each
and every line experiences some signal loss or degradation. Line Build Out describes the degree of
attenuation to be applied to the transmission signal in order to have the correct signal levels and
shape arrive at the receiver. Generally, the longer the line connecting the CPE and the network
equipment, the less the transmitted signal is attenuated.
CFGEDIT will use short or long haul information to determine the correct Line Build Out (i.e.,
degree of attenuation) for your lines. The value you input (in CFGEDIT) to determine attenuation
depends on whether or not you are using an external Channel Service Unit (CSU).
If you are using an external CSU, you will specify a value under Short Haul Build Out. Specify the
length of the line, in meters, from CPE to the CSU by selecting a range from zero to 210 meters.
If you are not using an external CSU, specify a value under Long Haul Build Out. On long hauls, your
telephone company will provide you with a decibel attenuation value when they install the lines.
The installers may specify option labels A, B, or C during installation. If so, these labels correspond,
respectively, to Long Haul Build Out values of -0.0dB, -7.5dB, and -15.0dB. The value is dependent
on distance, type and condition of physical line, and other environmental factors. For example, if
the distance to the Telco switch is great (6000 foot maximum), or the line is old, you may need a