1) PRC: When the destination node detects failures, the path switches directly to the protection route,
which requires a minimum configuration of network devices, earns the highest reliability and consumes
the shortest restoration time, usually within 50ms. But it needs network to provide more redundant
resource, which leads to the performance and cost are the highest, so it is used to protect the most
important business of optical transport network, usually used in long-distance backbone network and
metropolitan core network.
2) SNCP: Compared with the PRC, SNCP has the same restoration time roughly, and it needs less
network equipment, but it only has the protection route without the restoration route, so the reliability is
low. There is no need to provide redundant network resource for SNCP, so its performance and cost is
lower than PRC.Thus it is used for the network that has less demanding on the reliability.
3) GR: when one node detects failures, it will notify the source node. Source node will start the protection
route that is previously computed and the path will switch to the protection path through the interaction
between the source nodes and destination nodes. Its reliability is relatively high and restoration time is
normally less than 200ms. The resource that the business used to recover is shared, so it needs a relatively
less network redundant resource. Considering the restoration time and resources compromise, GR is an
ideal choice, which is often used in some important business of metro and access networks.
4) SBR: This type of circuit is mainly related to the re-routing. SBR needs many configuration and
interaction nodes, and the redundant resource may not be enough, so its reliability is not very good. Its
restoration time is relative to the network size, resource utilization and traffic load, generally costs less
than 200ms. It is used for the network that requires not very high reliability.
Thus, ASON can provide varieties of protection and restoration requirements for different levels of
business. Operators can make their own survival strategies of ASON according to the device level,
network topology, business requirements and other factors.
