20 Ironically, these management protocols would not be usable without the Ethernet (layer 2) being
operational. This scenario is somewhat ridiculous??”when there is an issue in Layer 2, then the higher
layer??“based (i.e., Layer 3) management protocol is useless, defeating the very purpose of having a
management capability.
21 There is not yet a formally defined OAM-layered model available, but the ones employed are generally close.
Figure 2.20 Ethernet OAM??”a layered perspective
Service Layer
Operator 1 Operator 2 First Mile
First Mile
Provider
Edge (PE)
Provider
Edge (PE) LAN
LAN
Service Provider IEEE 802.1ag
Connectivity Layer
Transport/Link Layer
UNI
UNI
Service Domain
First Mile
(IEEE 802.3ah)
First Mile
(IEEE 802.3ah) Sectionalized Management
88 Chapter 2
Service Layer OAM at the service layer provides the capability to manage the entire
Carrier Ethernet service being offered, i.e., a service instance represented as a uniquely
identified Ethernet Virtual Circuit (EVC) offered between two or more customer UNIs.
This end-to-end domain of the service??”basically the customer domain??”is ultimately
what matters to the end-user experience, so here the OAM is focused on ensuring the
service being offered is compliant with any agreed upon SLAs.
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