Test and management functions

The ITU-T has been consistently trying to improve operability and maintenance activity on xDSL lines.  As a result it has standardized two important standards which are used by both manufacturers and carriers to ensure maximum effectiveness of DSL lines.  Those standards are G.996.1 (G.test) for testing procedures and G.997.1 (G.ploam) for network management.  Since those are used commonly with ADSL, and are updated every now and then to include next generation standards, we will  discuss it shortly.

G.996.1 Testing procedures (G.test)

Recommendation G.996.1 describes the testing procedures for DSL transceivers.  It is based on V.56bis modem test recommendations .   
G.996.1 is useful for manufacturers during the design and development phase.  Bodies such as the DSLforum and ADSL-consortium are publishing technical reports based on the G.996.1 for functionality testing of DSL transceivers over several loop implementations (over different regions of the world) in various noise conditions (such as crosstalk from other services, impulse noise, POTS signaling), using the specific performance parameters that are included in each draft recommendation.  Also, other recommendations refer to G.996.1 for testing procedures and configurations.
The ITU continues its efforts to include more and models under this recommendation .  Recently (01/03) Annex B was added which describes test loop models and disturber models for ADSL under TCM-ISDN environment.

G.997.1 physical layer management for DSL transceivers (G.ploam)

Recommendation G.997.1 defines the DSL physical layer operations, administrations and maintenance functions.  Based on an Internet management approach (SNMP on HDLC), G.997.1 specifies control data exchange on a sub-channel of the DSL modems. It uses an MIB on the SNMP protocol (in each side) to easily integrate with existing network management systems.

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This concludes the introduction of xDSL shared protocols.  As we can see, many efforts were (and still are) made to create interoperability between the different xDSL methods by creating a unified system of protocols for handshaking, testing, and managing.  There is another standard reference we haven't yet mentioned, named G.995.1, which somewhat bounds all of the xDSL methods and protocols by providing a general overview on all xDSL standards, and the relations between them.  We've seen that the most noticeable in this standardization process is the ITU-T,  which more than once bases on the experience of other smaller standards bodies such as ANSI.

The following figure summarizes the xDSL protocol family.

 
Figure 1. xDSL suit of protocols and their relationships