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7.9.4
Protection Switching Time
Under automatic control, switching is completed within 50ms of detection of a fault
condition at the tributary port when there are <20 connections in broadcast mode. This
switching time increases linearly up to a maximum of 500ms for >20 connections.
For manual operation, switching is completed within eight seconds, this time being
measured from your entry of the command at the NMI to the confirmation to you.
During the period in which the selected input traffic is switched-over, errors are
generated in the V4 byte.
For compatibility with the switch unit protection mechanism or to prevent a switch unit
failure indication (in the case of an unprotected switch unit), the maximum duration of
any disruption of traffic from the output of the switch unit due to switching between
input ports is less than the persistency figures. This avoids exceeding the persistence
check period of the V4 byte diagnostic message check.
7.9.5
PDH Port Protection Architecture
The switch function on the core card monitors for fault conditions in the traffic streams
from PDH tributary cards and from the P12 function on the core card. The switch
function selects incoming traffic from the port with the highest quality and broadcasts
outgoing traffic on both ports.
7.10
MULTIPLEX SECTION SHARED PROTECTION (MS–
SPRING)
7.10.1
Introduction
MS-Spring schemes provide SDH trail protection by re-routing the AU-4 payloads of
aggregate STM-n signals in the event of a failure detected on a particular span, or
spans, of the Ring. The schemes provide protection against failure of the components
of SDH physical spans including optical fibres, regenerators and the electrical/optical
transducers at the multiplexer section termination points. Whilst MS-Spring schemes
are principally defined for 'external' Network level protection, the implementation also
provides protection against 'internal' NE equipment failures on the STM-n Interface
Units.
In MS-Springs normal traffic is transported on the Worker AU-4 channels of the
multiplexed STM-n Line signal. Reserved Protection AU-4 channels are provisioned to
transport the protected traffic in the event of failure of the Working sections.
The OMS 1200-16 provides 2-Fibre MS-Spring. In this case there is only one physical
ring and the multiplexed STM-n Line signal carries both Worker and reserved
Protection AU-4 channels. Accordingly, half the traffic channel capacity on the Ring is
logically assigned to Worker channels, and the other half is assigned to reserved
Protection channels. Lower Group channels (e.g: 1-8) carry Normal traffic, and Upper
Group channels (e.g: 9-16) are reserved for transporting the traffic during a protection
event.
221 02-ZAP 701 25/1 Rev C 2006-08-04
03PHB00004AAV-CUA
Marconi OMS 1200
Technical Product Description
© Ericsson AB 2006
Commercial in confidence
127
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