Specifications

3-31
Cisco AS5x00 Case Study for Basic IP Modem Services
11/24/1999
Section 3 Commissioning the Cisco AS5800 Hardware
Enabling the T3/T1 Controllers
Table 3-6 Controller Terms and Descriptions
Concept Description
Framing type Defines the control bits and data bits.
For T3s, Cisco supports:

M23—M23 multiplexer framing (default)
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C-bit—C-bit parity framing
For T1s, Cisco supports:
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ESF—Extended super frame. Required for 64 kb operation on DS0s.
ESF requires 2k-framing bits for synchronization. The remaining 6k is used for
error detection, CRC, and data link monitoring. ESF is recommended for PRI
configurations.

SF—Super frame. SF (D4) is used in channel bank robbed bit signalling (RBS)
configurations. The in-band signaling occurs within the 6th and 12th frames.
SF uses the framing bit for frame synchronization. SF is not recommended for
PRI configurations.
Line code type An encoding method used to allow synchronous data to be transmitted in a
compatible format. Common line codes are RZ (return to zero), NRZ (non-return to
zero), B8ZS, AMI, and HDB3.
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AMI—Alternate mark inversion. Signal transitions are referenced by a binary 1
(mark). AMI is used on older T1 circuits. B8ZS is more reliable than AMI.
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B8ZS—Most popular line-code scheme used in North America. To maintain
clock synchronization, B8ZS replaces string 8 binary 0s with variations. B8ZS
is more reliable than AMI, and it should be used with PRI configurations.
Clock source Refers to both timing and synchronization of the T1 carrier. Timing is encoded within
the transmitted data signal, and it ensures synchronization throughout the network.
Clocks are prioritized by slot number (slot 0 to slot 5). The highest priority clock is
selected from the card in slot 0. If this clock fails, the highest priority clock from the
card in slot 1 becomes the default clock, and so forth.
Timeslot
assignment
Timeslots are assigned to channels. For T1 PRI scenarios, all 24 T1 timeslots are
assigned as ISDN PRI channels. After timeslots are assigned by the
pri-group
command, D-channel serial interfaces are automatically created in the configuration
file (for example S1/0/0:0:23, S1/0/0:1:23, and so on).