Dell Force10 E300, Configuration Manual, Page: 94 / 1262

94 | 802.3ah
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• Remote Loopback —directs the remote system to reflects back frames that the local system transmits
so that an administrator can isolate a fault.
• Remote Failure Indication —notifies a peer of a critical link event.
Link Layer OAMPDUs
Link Layer OAM is conducted using OAMPDUs, shown in Figure 6-1 . OAM is a slow protocol and by
requirement may transmit no more than 10 frames per second, transmits to a multicast destination MAC,
and uses an Ethernet subtype.
Figure 6-1. OAMPFU Frame Format
There are six OAMPDU types, identified by the Code field:
• Information —carries state information and Local Information and/or Remote Information TLVs.
Information OAMPDUs are used in discovery, and as keepalives.
• Local Information TLVs —indicates support for variable retrieval, link performance events, and
remote loopback, unidirectional support, and OAM mode
• Remote Information TLVs —a copy of the peer’s Local Information TLV.
• Event Notification —carries TLVs for each concurrent link fault.
• Variable Request —carries MIB object descriptors for which the remote peer should return values.
• Variable Response —carries the requested MIB object values.
• Loopback Control —carries the loopback control command (enable and disable).
• Organization Specific —contains and OUI followed by data, the format and function of which is
defined by the organization.
OAMPDU Flags
1-bit flags are used it indicate OAM state and link state. During discovery, flags 3-6 are used to indicate the
state of peership establishment. Flags 0-2 are used to indicate a local critical link event to the remote peer.
Destination MAC
(01-80-c2-00-00-02)
Source MAC Length/Type
(0x8809)
Payload
(TLVs)
Padding
FCS Sub-type
(0x03)
Flags Code
Slow Protocol
multicast address
Slow Protocols
use a subtype
0: Link Fault
1: Dying Gasp
2: Critical Event
3: Local Evaluating
4: Local Stable
5: Remote Evaluating
6: Remote Stable
7-15: Reserved
00: Information
01: Event Notification
02: Variable Request
03: Variable Response
04: Loopback Control
05-FD: Reserved
FE: Organization Specific
FF: Reserved