User manual

Product Description
Framing Modes
2-8 July 2004 Wide Bank 28 DS3 - Release 2.4
Framing Modes
 Additional Functions Available in C-Bit Mode ... 2-8
 DS3 Multiframe Structure ... 2-9
The Wide Bank 28 DS3 can be configured for either M23 or C-bit framing. The major difference
between M23 framing and C-bit parity framing is that M23 framing uses the C-bits to indicate stuffing,
while C-bit parity framing does not.
With M23 framing, all three C-bits in a subframe are set to one (1) if stuffing occurs, or to zero (0) if
stuffing does not occur.
C-bit parity framing does not require stuffing indication (stuffing is always present), so the C-bits are
used for other applications. These other applications and how the C-bits are used to accomplish them
are described in the following text and figures.
Additional Functions Available in C-Bit Mode
When configured for C-bit framing, the Wide Bank 28 DS3 provides the following functions, which
are not available in M23 framing:
 Control of C-bit loopbacks for low-speed and DS3 using the loopup and loopdown commands
 The third C-bit in M-subframe 1 provides a far-end alarm and control signal. This signal is
used to send alarm or status information from the far-end to the near-end and to initiate low-
speed and DS3 loopbacks at the far-end terminal from the near-end terminal. See Testing the
DS3 Far-End with Loopback Tests on page 7-37.
 Automatic receipt of far-end alarms
 The alarms are sent automatically and result in a minor alarm indication on the Wide Bank 28
DS3. See DS3 Far-End Alarms and Control (FEAC) on page 12-4.
 Controlled receipt of far-end statistics and status
 Separate commands for statistics and status must be issued from the Wide Bank to cause the
network to send the information. See DS3 Far-End Statistics on page 7-7.
 Point-to-Point Protocol (PPP) IP communication over C-bit link
 This provides an IP connection over the C-bit data link instead of the Ethernet port, and
provides management access equal to the Ethernet port. See Management Interfaces on
page 8-2.
 Controlled receipt of PPP link status
 A command issued from the Wide Bank causes the network to send the information. See
Point-to-Point Protocol Status on page 7-8.
 A terminal-to-terminal Path Maintenance Data Link