Unstructured Ds1 - 3Com 3C63100-AC-C - PathBuilder S600 Bridge/router Reference Manual

Figure 54 Multiframe Structure for 3x64kbit/s DS1 or E1 with CAS
AAL1 Pointer
Pointer
ABCD for
First
Transported
Timeslot
. . .
ABCD for
Third
D for
Transported
Timeslot
ported
slot
Transported Timeslot
D f
The PathBuilder S600 CBR module can detect the AB bits on the CAS to activate
or de-activate the CBR PVC.
When an off-hook signal is detected, the CBR PVC is activated.
n
When an on-hook signal is detected, the CBR PVC is deactivated, freeing up
n
the network access bandwidth for other uses (such as VBR traffic). This is the
basis for dynamic bandwidth allocation.
Note that 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 S600 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 55.
First Transported Octet of Multiframe
Second Transported Octet of Multiframe
. . .
First 125 µsec Frame of Multiframe for
DS1
Second 125 µsec Frame of Multiframe for
DS1
Last 125 µsec Frame of Multiframe for
DS1
ABCD for Second
Signaling
Application Overview
First Transported Octet of Multiframe
Second Transported Octet of Multiframe
First 125 µsec Frame of Multiframe for
DS1
Second 125 µsec Frame of Multiframe f
DS1
Last 125 µsec Frame of Multiframe for
DS1
Signaling
Substructure
91