Enterasys Networks CSX7000 Manuel d'utilisateur télécharger pdf (Page 125)

Central Site Remote Access Switch 125

ONFIGURING

ESOURCES

AND

INES

Lines

LINE ENCODING

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 METHOD

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.

OMMON CHANNEL

In the Common Channel signaling case, one of the 24 channels of the PRI frame is devoted

to call control messaging.

OBBED BIT SIGNALING

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.

INE BUILD OUT

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

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Enterasys Networks CSX7000 Manuel d'utilisateur Page 125

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