Nortel Networks NTRN10AN, 3500 manual Per-site dedicated STS, Vtx, Stx

2-176Operation, administration, and maintenance (OAM) features

Two ways to manage VTs on a UPSR are:

•Use dedicated STS at each node and provision STS connections at each pass-throughVT-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 2-176shows a configuration that uses dedicated STS at each site and Figure 2-64 on page 2-177shows 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 2-178shows a configuration that uses a virtual ring with shared VT-managed STS and Figure 2-66 on page 2-179shows 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

VT#n, STS-1 #1

OM3500

(W/VTX)

OC-3/12/48

UPSR ring

OM3500

(W/VTX)

VT#n, STS-1 #2

OM3500

(W/STX)

All VTs STS-1 #1

OK

OK

STS-1 #1

Path bridge & select

STS-1 #2

Path bridge & select

OK

OK

All VTs STS-1 #2

Backbone

Network

Note: For simplicity only one direction is shown.

OPTera Metro 3500 Multiservice Platform NTRN10AN Rel 12.1 Standard Iss 1 Apr 2004