Unstructured Ds1 - 3Com 3C63400-3AC-C - PathBuilder S700 Switch Reference Manual

The PathBuilder S700 software can also monitor a full 8-bit pattern on a DS0 to
determine circuit activity. This is the basis for the two supported types of dynamic
bandwidth allocation (DBA):
Structured voice DBA
n
Structured data DBA
n
Structured Voice DBA When a CBR port is configured as structured voice,
signaling bits of voice channels are carried along with their payload in AAL1 cells.
These signalling bits, which are received from T1/E1 framers, are stored in buffers
provided in the SAR processor. The CBR software periodically reads the stored
signaling bits and checks for an idle condition of voice channels with on-hook
detection enabled.
When an on-hook (idle) signal is detected, the CBR virtual circuit is deactivated,
n
and the bandwidth reserved for that channel is released for other uses (such as
VBR traffic).
When an off-hook signal is detected, the CBR virtual circuit is activated.
n
Structured Data DBA When a CBR port is configured as structured data, only
DSO payload bytes are carried in AAL1 cells. These data cells are stored in buffers
provided in the SAR processor. The CBR software periodically reads the stored data
bits and checks for an idle code in the stored data bits of each DS0 channel. All
virtual circuits in the port use a user-selected DBA bit mask to mask off bits that
are not a portion of the idle code.
When an on-hook condition (idle code) is detected, the CBR virtual circuit is
n
deactivated, and the bandwidth reserved for that channel is released for other
uses.
When an off-hook condition (no idle code) is detected, the CBR virtual circuit is
n
activated.
A structured DS1 channel will not pass the original DS1 frame to the remote end.
For instance, ESF network management will terminate at the PathBuilder S700 on
a structured DS1, so CSU to CSU Facility Data Link (FDL) communication will not be
possible. FDL communication is possible with unstructured DS1.

Unstructured DS1

Implement unstructured DS1 service when you want DS1 tunneling through an
ATM system. DS1 tunneling allows an entire DS1 frame including framing bits to
transit an ATM networks. See Figure 57.
Supported Applications 93