Discovery

Discovery is the first phase of EFM-OAM. At this phase, EFM-OAM identifies network devices along with their OAM capabilities. The Discovery process relies on the Information OAMPDUs. During discovery, the following information is advertised through the TLVs within periodic information OAMPDUs:

  • OAM capabilities: Advertises the capabilities of the local OAM entity. Using this information, a peer can determine what functions are supported and accessible (for example, loopback capability).
  • OAM mode: The OAM mode is conveyed to the remote OAM entity. The mode can be either active or passive, and can also be used to determine a device’s functionality.
  • OAMPDU configuration: This configuration includes the maximum OAMPDU size to delivery. In combination with the limited rate of 10 frames per second, this information can be used to limit the bandwidth allocated to OAM traffic.

Timers

Two configurable timers control the protocol, one determining the rate at which OAMPDUs are to be sent, and the second controlling the rate at which OAMPDUs are to be received to maintain the Discovery procedure from resetting.

  • The timer should generate PDUs in the range of 1 - 10 PDUs per second. The default value is 1 PDU per second.
  • The Hold timer assumes the peer is dead if no packet is received for a period of 1 - 10 seconds. The default value is 5 seconds.

Flags

Included in every OAMPDU is a flags field, which contains, besides other information, the status of the discovery process. There are three possible values for the status:

  • Discovering: Discovery is in progress.
  • Stable: Discovery is completed. Once aware of this, the remote OAM entity can start sending any type of OAMPDU.
  • Unsatisfied: When there are mismatches in the OAM configuration that prevent OAM from completing the discovery, the discovery process is considered unsatisfied and cannot continue.
Parent topic: EFM-OAM Protocol