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Application Guidelines
Ones Density Enforcement
Connection to the T1 Network requires the connecting device (SC-IP) to meet pulse density
constraints. The method for adhering to the pulse density constraints is termed Ones Density
Enforcement.
The SC-IP's Line Code option supports:
•
Alternate Mark Inversion (AMI) with no bipolar violations
•
Bipolar with 8 Zero Substitution (B8ZS) with bipolar violations
The Line Code option you choose depends primarily on the design of the T1 Network, keeping in
mind that all equipment must be compatible with AMI coding and some equipment may not be
compatible with B8ZS coding.
When optioned for B8ZS, the SC-IP replaces eight consecutive "zeros" with a sequence, including
bipolar violations, which can be detected to allow any combination of zeros and ones to be
transmitted throughout the T1 Network.
When optioned for AMI, the SC-IP automatically inserts "ones" in accordance to the configuration
as shown below. This insertion of "ones" will cause the frame relay packets to be corrupted (FCS
errors) as illustrated in and . The user should be aware of this and attempt to eliminate excessive
zeros in the transmit direction (towards the T1 Network).
1
NETWORK
ORIGINATES
EXCESSIVE ZEROS
Table A-5
Application with 8(N+1) Enforcement
Line Code
B8ZS
AMI
AMI
Note
The AMI line option code is not recommended for a 64kbps network rate.
A-6
2
SC-IP INSERTS ONES
TO ENFORCE DENSITY
CONSTRAINT
Frame Relay
T1/FT1
SC-IP
Network
Format
Consecutive
xx
Nx56K
Nx64K
SpectraComm IP Router Card
Installation and Operation Manual
Ones Density Enforcement
3
INSERTED ONES
PASS THROUGH
UNDETECTED
T1/FT1
SC-IP
NETWORK
RECEIVES
ERRORED
PACKETS
Enforcement
xx
B8ZS
Consecutive
None
Consecutive
8(N+1)
4
076R200-000
Issue 2
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