G.8031 Protected Ethernet Tunnels - Alcatel-Lucent 7750 SR Manual

G.8031 Protected Ethernet Tunnels

Alcatel-Lucent implementation of Ethernet Tunnels offers ITU-T G.8031 specification compliance
to achieve 50 ms resiliency for failures in a native Ethernet backbone for native Layer 2 networks.
Ethernet Automatic Protection Switching (APS) as defined in ITU-T recommends G.8031
provides a linear 1:1 or 1+1 protection switching mechanism for VLAN-based Ethernet networks.
The 7750 SR OS implementation of G.8031 supports 1:1 linear protection through implementation
of point-to-point Ethernet Tunnels providing a working and protecting Ethernet circuit, where the
path providing the protection is always available through health-monitoring. The 1:1 model is
common practice for packet based services since it makes best use of available bandwidth.
Within each path, Y.1731 Maintenance Entity Group (MEG) Endpoints (MEPs) are used to
exchange APS-specific information (specifically to co-ordinate switchovers) as well as optionally
fast Continuity Check Messages (CCM) providing an inherent fault detection mechanism as part
of the protocol. Failure detection of a working path by one of the mechanisms triggers to move
from working to protecting circuits. Upon failure, re-convergence times are a dependent on the
failure detection mechanisms. In the case of Y.1731, the CCM transmit interval determines the
response time. The 7750 SR OS supports message timers as low as 10 milliseconds so the
restoration times are comparable to SONET/SDH. Alternatively, 802.3ah (Ethernet in the First
Mile) or simple Loss of Signal can act as a trigger for a protection switch where appropriate.
Revertive or nonrevertive behavior can be configured based on service provider environment.
Revertive behavior is commonly deployed since it restores the traffic to a predictable state.
Ethernet APS can be configured on any port configured for access mode using dot1q or Q-in-Q
encapsulation enabling support for Ethernet APS protected services on the service edge towards
the customer site, or within the Ethernet backbone. ELINE, ELAN, and ETREE services can be
afforded Ethernet APS protection and, although the Ethernet Tunnel providing the protection has a
working/protecting path that is presented to the service as a single logical entity to the service
layer. The intention of this is to cause minimum disruption to the service during Ethernet APS
failure detection and recovery.
Page 54 7750 SR OS Services Guide