16 61225101L1-5B
Multiple Services
The NTU supports the configuration of multiple
services. These services are routed to either the
G.703/G.704 interface or the Nx64k interface. The
Nx64k interface supports a single service with
1 <= N <= 36. The G.703 interface (with G.704
framing) supports multiple services (often termed
“Stacked E1”). The G.703 interface without any
framing supports a single 2048 kBit/s service. (See
ITU-T G991.2 Annex. E.1-TPS-TC for European
2048 kbit/s digital Unstructured Leased Line
(D2048U).)
The Nx64k service and G.703 service are capable of
operating simultaneously. The total number of time
slots must be less than or equal to the maximum
number of SHDSL time slots (excluding TS0 if
structured E1 is used). The G.703 interface with
framing (G.704) runs over SHDSL in aligned mode
and supports simultaneous services using the Nx64k
port for the second service. (See ITU-T G991-2
Annex E.7 - TPS-TC for Aligned European 2048
kbit/s digital Structured Leased Line (D2048S) and
Fractional.)
The SHDSL NTU supports CRC-4 detection/
generation toward the SHDSL network (Figure 22).
The CRC-4 detection/generation can operate in the
following modes (configurable via the management
interface):
1. CRC-4 detection/generation disabled
2. CRC-4 detection/generation enabled
When less than 32 time slots are configured on the
G.703 port, the NTU bases the CRC-4 detection/
generation on filling the unused time slots with a fixed
pattern configurable via the management interface.
This CRC-4 detection/generation is also required for
multirate (single or simultaneous services) where less
than 31 G.704 time slots are carried over the SHDSL
line.
NOTE
All framed services operate in aligned mode.
Operation
The SHDSL NTU supports multiple rate line
operation as specified in ITU-T G.991.2. All services
described in this document operate in multiple rate
mode, with a corresponding change in maximum
payload. Unstructured E1 is supported for SHDSL
rates equal to 32 and with all G.703 time slot
assignments equal to the same G.703 service value
(1 to 31).
The G.703 interface supports operation in the
following modes that are selectable via the
management interface:
1. Framed
2. Framed pass through
3. Unframed
Figure 22. CRC-4 Detection/Generation
SHDSL Time Slots
Nx64k Service
E1 Service
