ATM Operation and Maintenance

ATM Operation and Maintenance is a set of protocols defining how Asynchronous Transfer Mode interfaces can test their reliability. Not unlike many other OA&M protocols, ATM OAM relies on a predefined packet format for its monitoring functions.

Packet format

F4 (VP) OAM Cell Format

GFC	VPI	VCI	PT	CLP	HEC	OAM TYPE	Function TYPE	Function Specific Fields	Reserved	CRC-16
	Same as User Cell	3 (Segment) 4 (End-to-End)				4-bits	4-bits	45-octets	6-bits	10-bits

F5 (VC) OAM Cell Format

GFC	VPI	VCI	PT	CLP	HEC	OAM TYPE	Function TYPE	Function Specific Fields	Reserved	CRC-16
	Same as User Cell	Same as User Cell	100 (Segment) 101 (End-to-End)			4-bits	4-bits	45-octets	6-bits	10-bits

Charts from

Types and function types

The following table identifies the type and function type field for the major OAM operations of Fault Management, Performance Management, Activation/Deactivation, and System Management.

OAM Type		Function Types
Fault Management	0001	AIS	0000
	0001	RDI/FERF	0001
	0001	Continuity Check	0100
	0001	Loopback	1000
Performance Management	0010	Forward Monitoring	0000
	0010	Backward Reporting	0001
Activation/Deactivation	1000	Performance Monitoring	0000
	1000	Continuity Check	0001
System Management	1111	Non-Standardized

External links

• ITU-T I.610