Nortel Networks OPTera Metro 3500 - Manual (Page 214)

2-176 Operation, administration, and maintenance (OAM) features
OPTera Metro 3500 Multiservice Platform NTRN10AN Rel 12.1 Standard Iss 1 Apr 2004
Two ways to manage VTs on a UPSR are:
• Use dedicated STS at each node and provision STS connections at each
pass-through VT-managed OPTera Metro 3000 node on the subtending
UPSR. This option is simple to implement and prevents VT traffic loss in
case of a fiber cut.
Figure 2-63 on page 2-176 shows a configuration that
uses dedicated STS at each site and Figure 2-64 on page 2-177 shows the
same configuration after a fiber cut. There is no loss of VT traffic.
• Use a virtual ring with shared VT-managed STS. Figure 2-65 on page
2-178 shows a configuration that uses a virtual ring with shared
VT-managed STS and Figure 2-66 on page 2-179 shows the same
configuration after a fiber cut. There is no loss of VT traffic.
Note: Using shared VT-managed STS can result in traffic loss in case of
a fiber cut if the VTs are not managed correctly. For example, using an STS
path selector on STS-managed OPTera Metro 3500 to terminate an STS
which contains VTs from various nodes (a shared VT-managed STS) can
result in VT traffic loss in case of a single fiber cut. See
Figure 2-67 on
page 2-180 .
Figure 2-63
Per-site dedicated STS
EX1545p
OM3500
(W/VTX)
OM3500
(W/STX)
OM3500
(W/VTX)
OC-3/12/48
UPSR ring
Note: For simplicity only one direction is shown.
OK
OK
VT#n, STS-1 #1
STS-1 #1 All VTs
STS-1 #2 All VTs
STS-1 #1
Path bridge & select
STS-1 #2
Path bridge & select
VT#n, STS-1 #2
OK
OK
Backbone
Network