802.1Ag; Ethernet Cfm - Dell S4048–ON Configuration Manual

802.1ag

Ethernet operations, administration, and maintenance (OAM) are a set of tools used to install, monitor, troubleshoot, and manage
Ethernet infrastructure deployments. Ethernet OAM consists of three main areas:
• Service layer OAM — IEEE 802.1ag connectivity fault management (CFM)
• Link layer OAM — IEEE 802.3ah OAM
• Ethernet local management Interface — (MEF-16 E-LMI)

Ethernet CFM

Ethernet CFM is an end-to-end per-service-instance Ethernet OAM scheme which enables: proactive connectivity monitoring, fault
verification, and fault isolation.
The service-instance with regard to OAM for Metro/Carrier Ethernet is a virtual local area network (VLAN). This service is sold to an
end-customer by a network service provider. Typically the service provider contracts with multiple network operators to provide end-
to-end service between customers. For end-to-end service between customer switches, connectivity must be present across the
service provider through multiple network operators.
Layer 2 Ethernet networks usually cannot be managed with IP tools such as internet control message protocol (ICMP) Ping and IP
Traceroute. Traditional IP tools often fail because:
• there are complex interactions between various Layer 2 and Layer 3 protocols such as spanning tree protocol (STP), link
aggregation group (LAG), virtual router redundancy protocol (VRRP), and electronic commerce messaging protocol (ECMP)
configurations.
• ping and traceroute are not designed to verify data connectivity in the network and within each node in the network (such as in
the switching fabric and hardware forwarding tables).
• when networks are built from different operational domains, access controls impose restrictions that cannot be overcome at the
IP level, resulting in poor fault visibility. There is a need for hierarchical domains that can be monitored and maintained
independently by each provider or operator.
• routing protocols choose a subset of the total network topology for forwarding, making it hard to detect faults in links and nodes
that are not included in the active routing topology. This is made more complex when using some form of traffic engineering (TE)
based routing.
• network and element discovery and cataloging is not clearly defined using IP troubleshooting tools.
There is a need for Layer 2 equivalents to manage and troubleshoot native Layer 2 Ethernet networks. With these tools, you can
identify, isolate, and repair faults quickly and easily, which reduces operational cost of running the network. OAM also increases
availability and reduces mean time to recovery, which allows for tighter service level agreements, resulting in increased revenue for
the service provider.
In addition to providing end-to-end OAM in native Layer 2 Ethernet Service Provider/Metro networks, you can also use CFM to
manage and troubleshoot any Layer 2 network including enterprise, datacenter, and cluster networks.
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