Figure 81. Ms Spring Drop And Continue, Insert Continues (Protected) - Alcatel 1850 TSS-320 Technical Handbook

MS - SPRING Interworking
When a 2f MS-SPRING is interconnected with another ring (either SNCP/I or MS-SPRING), the
interconnection of the two is performed by connecting two nodes per ring with HVC connections, as shown
in Figure 81.on page132.
Each VC4 that has to cross the ring boundary (only HVC level ring interconnections are considered here)
must be output by two nodes, one of which, the Primary Service Node (PSN) drops it and continues to
the Secondary Service Node (SSN). In the opposite direction, the SSN inserts a copy of the VC4 into the
ring and the PSN selects by means the Primary Node Service Selector function, between the VC4 coming
from the SSN and the VC4 that can be locally inserted by means an STM-1 Tributary. The selection is
made on the Path-AIS basis (AU-AIS).
The protection mechanism works on the hypothesis that the other ring selects one of the two versions of
the incoming VC4 and transmits two identical copies of the VC4 towards the PSN and the SSN (this is
guaranteed if the other ring is an MS-SPRING or an SNCP ring).
Note that the PSN and the SSN need not to be adjacent and need not to be the same for all of the VC4
that cross the ring boundary: i.e. each crossing VC4 has two associated nodes that act as PSN and SSN.
Primary
Service
Node
SS = Service Selector

Figure 81. MS SPRING Drop and Continue, Insert Continues (protected)

Alcatel 1850 TSS-320 Rel. 1.1
132/270 8DG 07734 AAAA Edition 01
2F MS - SPRING
side A
side B
side A
SS
side A
side A side B
SNCP or MS-SPRING
side B
Secondary
Service
Node
side B
Technical Handbook Common
Functional Description