Drop & Continue - Alcatel 1850 TSS-320 Technical Handbook

3.6.3 Drop & Continue
(See from Figure 65.on page 118 to Figure 69.on page 120)
The Drop and Continue architecture has been implemented in the network to improve traffic availability.
Drop and Continue is a way of protecting a path crossing a number of sub-networks, e.g., rings.
The sub-networks should be connected through at least two nodes (so realizing two independent
connections).
The equipment is configured as "DROP and CONTINUE" on each interconnection node.
The subnetworks' equipment implement the connection between two SNCP rings.
The resulting architecture affords protection against multiple failures (evenly distributed one per
subnetwork) tolerated without traffic loss (node failure or single cable cut).
The Drop and Continue feature improves traffic availability as compared with the simple "end-to-end
SNCP". More subnetworks are connected the further is availability increased.
The Drop and Continue features simultaneously realizes the following on one node:
• unidirectional pass-through
• protected drop
• insertion in one direction
The achievable configurations are:
• D/C-A INS-A
• D/C-A INS-B
D/C stands for "Drop and Continue", the letter after it (A = line side" A" ) indicates the "drop " side (e.g.,
"A" means "A main side", and consequently the spare side is the "B" one).
The end letter (INS-B or INS-A) indicates the insert side.
N.B. The letters "A" and "B" are not referred to a specific board or ports in a physical slot of
the subrack; "A" and "B" are used in the figures of this paragraph to identify a Line
direction.
The "Unidirectional pass-through" is always in the direction opposite to that of the "insert" side (e.g., when
"INS B" the pass-through is from B side to A side).
For further information refer to Figure 65.on page 118 which shows the D/C-A INS-A configuration and
Figure 66. on page 118 which shows the D/C-A INS-B configuration.
Technical Handbook Common
Functional Description
Alcatel 1850 TSS-320 Rel. 1.1
8DG 07734 AAAA Edition 01 117/270