Interface Configuration
7710 SR OS Interface Configuration Guide
Page 53
Automatic Protection Switching (APS)
APS is designed to protect SONET/SDH equipment from linear uni or bi-directional failures. The
Network Elements (NEs) in a SONET/SDH network constantly monitor the health of the network.
When a failure is detected, the network proceeds through a coordinated predefined sequence of
steps to transfer (or switchover) live traffic to the backup facility (protection facility). This
happens very quickly to minimize lost traffic. Traffic remains on the protection facility until the
primary facility (working facility) fault is cleared, at which time the traffic may optionally be
reverted to the working facility.
This section discusses the different APS architectures and their implementations.
•
→
→
→
APS Protection Switching Byte Failure on page 56
→
APS Channel Mismatch Failure on page 56
→
APS Mode Mismatch Failure on page 56
→
APS Far-End Protection Line Failure on page 57
→
1+1 Switch Operation Example on page 57
→
APS 1+1 Protection and Working Port Management Operations on page 59
APS 1+1
The data path supports 1:1 data path architecture (data is sent only on the active link); however,
the 1+1 signalling is used for full interoperability with signalling-compliant 1+1 architectures.
In the ingress direction, the working and protection signals are selected independently. In the
egress direction, the data is only transmitted on the active circuit. For a single failure, this may
cause a data outage of up to 100 milliseconds. When APS protects IMA groups, IMA cells, but not
user traffic, are sent on the inactive circuit as well to keep IMA protocol up during an APS switch.
The APS channel (bytes K1 and K2 in the SONET header) is used to exchange requests and
acknowledgments for protection switch actions. In both bi-directional and uni-directional
interoperable APS switch modes, the router sends and requires to receive K-bytes to ensure that
data is transmitted on the circuit the far-end has its selector on.
The bit assignment for the K1 and K2 bytes is defined in the following sections:
•
•
Содержание 7710 SR OS
Страница 6: ...Page 6 7710 SR OS Interface Configuration Guide Table of Contents...
Страница 8: ...Page 8 7710 SR OS Interface Configuration Guide List of Tables...
Страница 10: ...Page 10 7710 SR OS Interface Configuration Guide List of Figures...
Страница 14: ...Preface Page 14 7710 SR OS Interface Configuration Guide...
Страница 16: ...Getting Started Page 16 7710 SR OS Interface Configuration Guide...
Страница 100: ...Configuration Process Overview Page 100 7710 SR OS Interface Configuration Guide...
Страница 142: ...Service Management Tasks Page 142 7710 SR OS Interface Configuration Guide...
Страница 428: ...Debug Commands Page 428 7710 SR OS Interface Configuration Guide...
Страница 434: ...Standards and Protocols Page 434 Standards and Protocols...
Страница 436: ...Page 436 7710 SR OS Interface Configuration Guide...