ATM MANAGEMENT PLANE

 

As shown on the ATM functional reference model, the management plane covers the management of the different ATM layers of both user and control planes as well as the management and coordination across layers and across the different planes to ensure that everything works properly. It manages faults, performances, configuration, accounting and security within the ATM network.

• Layer Management deals with the Physical, ATM, AAL and the higher-layer protocol entities in both the user and control planes. It has the responsibility for fault monitoring, generating alarms, and taking corrective actions, monitoring for compliance to the performed state in the traffic contract, as well as configuring.
• Plane Management links and coordinates the different network layer management entities (so-called agents) through usually a central management system (manager) where the management applications run. The management information are exchanged via a dedicated network (a set of well-defined VCs) and dedicated protocols: SNMP (Simple Network Management Protocol) and ILMI (Interim Local Management Interface) for private ATM networks, CMIP (Common Management Information Protocol) for public ones.

NETWORK MANAGEMENT FRAMEWORK

The different standardized management interfaces are shown below

NMS: Network Management System- CPE: Customer Premises Equipment - NE: Network Element - EML: Element Management Layer - NML: Network Management Layer

This management model is derived from a more general one, the Telecommunication Management Network (TMN). It is based on hierarchical management layers: the NE layer (the Agents), the EML layer (the Network Elements Manager) aggregating similar network devices, the NML (the Network Manage) controlling and consolidating the various network.
In the private domain, a simpler scheme is used with network management center (NMS) driving agents located in the customer premises equipments. In addition a special interface is defined ILMI for direct management interaction between network equipments.

MANAGEMENT INTERFACES

They have been defined between the different entities of the management model

Types	Interaction	Purpose	Services	Protocol
M1	CPE / NMS	Management of user terminal equipment		SNMP
M2	P-Switch / NMS	Management of the ATM private network	Similar to M4	SNMP
M3	NMS / NML	Management interaction between private and public domains	. Public network configuration and status gathering  . Add & deletion of pre-authorized VCs  . new connection request	SNMP
M4	NML / EML or  EML / NE	Management of NE's and EMLs	. Fault and performance management  . Configuration and circuit provisioning  . accounting	CMIP  (Q3)  or SNMP
M5	NML / NML	Management interaction between different owned public domains	Cross public network management	No standard yet
ILMI	Private/public	Service control	Service activation, service assurance (maintenance), usage metering (performance, billing)	ILMI - SNMP

To implement the underlined services at the different mentioned interfaces, Management Information Models (MIB) have been defined for ATM.

ATM MIBS

They define (or will define) the information exchanged at the M1 to M5 interfaces. They are related to the various ATM Management Elements (AME) or ATM managed objects (physical ATM devices, links, connections, services, etc). A summary of the currently standardized MIBs is presented in the next table.

 

MIB	Purpose	Standard
ILMI	Configuration across ATM devices	ATM Forum UNI 3.x & 4.0
Transmission media	AME for SONET/SDH or other Physical Media	ITU G704,G774  IETF RFCs 1595,1407,1406
Inverse Mux	Inverse Mux on N*E1/T1	ATM Forum [M2,M4]
DXI MIB	Router-DSU interface	ATM Forum [M1]
ATM MIB	AME for private networks & devices	IETF RFC 1695  ATM Forum [M1,M2]
CES MIB	AME for circuit emulation	ATM Forum [M2,M4]
LANE MIB	AME for LAN emulation	ATM Forum [M1,M2]
M3 MIB	AME for customer's portion of public network	ATM Forum [M3]
M4 - NE	AME for carrier network elements	ATM Forum [M4 NE]
M4 - Network	AME for carrier network	ATM Forum [M4]
G.ATM	AME for carrier network	ITU-G.ATM (M3100)
M5-NNI	AME for carrier networks interconnection	ATM Forum [M5]

The standardization work is still ongoing and takes into account the ATM service and interface evolutions

An important management interface is the ILMI because it does contribute to ease configuration with a "plug & play" approach.

ILMI

ILMI is a peer-to-peer protocol that facilitates automatic configuration of ATM equipments. It uses the SNMP syntax, has its own service MIB and allows management requests from both the ATM end system and the ATM switch. It has a dedicated ATM channel (VPI=0/VCI=16). The management features of this interface and its evolution with the successive UNI releases are presented in the following table.

 

ILMI features

. Interface configuration, maximum number of connections, speed, media type, private or public interface, operational status and QOS for each connection (VPC & VCC)  . Automatic learning of NSAP network prefix address, address registration  auto-discovery of network topology  Multiple links management

 

The management of the physical and ATM layers is also performed via the Operation, Administration and Maintenance (OAM) flows

OAM FLOWS

As previously mentioned in the "ATM Layer" section of this tutorial, the different levels of transmission channels (transmission path and section, the end-to-end and segment VP, the end-to-end and segment VC) are supervised via the F3 to F5 flows. They provide real time monitoring and troubleshooting which SNMP is incapable of.

More precisely they perform the following functions: performance monitoring (error rates), defect and failure detection, system protection (in case of link failure), forwarding of failure and performance information and fault localization.

FLOW	Supervised object	OAM cells	OAM channel identification
F1	SDH - Regeneration section	N/A	N/A
F2	SDH - Digital section	N/A	N/A
F3	Transmission Path	LOC, failure in idle cells processing	VPI=0, VCI=0, PTI=100
F4 segment	VP Link	AIS, FERF, LOOP	VCI=3
End-to-end F4	VP connection		VCI=4
F5 segment	VC Link		PTI=100
End-to-end F5	VC connection		PTI=101
N/A: Non Applicable (internal to SDH/SONET networks)  AIS: Alarm Indication Signal (sent downstream to notify upstream failure) - RDI: Remote Defect Indication (to notify in the reverse direction the faulty condition) - FERF: Far End Reporting Failure - LOC: Loss of Cell Delineation  LOOP: controls loopbacks to verify part or the end-to-end connection

 

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