Foundry NetIron M2404C and M2404F Metro Access Switches
Network Administration Tools (Rev. 03)
MEF OAM
© 2008 Foundry Networks, Inc.
Page 3 of 155
MEF OAM
Metro Ethernet Forum (MEF) Operations, Administration and Maintenance (OAM) standard is
generally described as implementing bridged-Ethernet per-VLAN network-wide Ping and Hello
packets for estimating service assurance metrics and specific connectivity tests. Furthermore,
traceroute is available for finding and displaying an Ethernet-level path from the current device to
a specified device in the network. OAM functionality provides reliable service assurance
mechanisms for both provider and customer networks.
By enabling MEF OAM the user gains the ability to monitor the activity of the single-link/entire
bridged Ethernet network by using a built-in mechanism. The OAM feature is a powerful tool for
the network engineers to test in real-time connectivity, latency, jitter and frame-loss parameters on
the bridged network without need for higher-layer implementations.
OAM offers the ability to perform automatic periodic network-wide service assurance and quality
verifications.
Overview
MEF OAM provides mechanisms to perform Ethernet network-wide service assurance for
providers and end-to-end service assurance for the Ethernet customers. Bridges implementing this
standard will be added to the MEF OAM domains on the 802.1q bridged network and will
participate in service-level assurance and fault isolation.
From the operational aspect, the following basic functions are supported:
•
Network discovery (802.1q bridged network – discovery per VLAN)
•
Connectivity verification
•
OAM over VPLS connectivity verification
•
Latency and loss measurement
•
Delay variation measurement
•
Traceroute functions.
Each device may send a multicast Ping request for other devices to answer. Regular Ping and Hello
frames to other devices on the same network may be used to measure delay, jitter and frame-loss.
An OAM domain is defined by a connected topology of bridges within which OAM operates
unobstructed. At the edges of a domain, filtering constructs prevent Ethernet Service OAM frames
from exiting their domain. On each bridge, each port is classified as interior or exterior for that
domain. Up to seven domains can exist on a device at a time.
The discovery process creates a table of the reachable bridges within the OAM domain. The
connectivity verification process may send a connectivity test request to the specified bridge and
wait for a connectivity test reply message.
The alternative mechanism is to use periodic Hello frames between the devices on the OAM
domain. Each Hello frame between two OAM domain members indicates that direct connectivity
from the source bridge A to the target bridge B exists.
The most widely used implementation will be for CE-to-CE or PE-to-PE service assurance. The
following service assurance possibilities exist:
•
The network administrator will define general thresholds for the network behavior
(network-wide connectivity, network-wide jitter).