Editing Synchronous optical networking (section)

==SONET/SDH network management protocols==
{{See also|Telecommunications Management Network}}
{{Technical|section|date=November 2010}}

===Overall functionality===
Network management systems are used to configure and monitor SDH and SONET equipment either locally or remotely.

The systems consist of three essential parts, covered later in more detail:
* Software running on a ''network management system terminal'', e.g. workstation, dumb terminal or laptop housed in an exchange/central office.
* Transport of network management data between the ''network management system terminal'' and the SONET/SDH equipment, e.g. using TL1/Q3 protocols.
* Transport of network management data between SDH/SONET equipment using ''dedicated embedded data communication channels'' (DCCs) within the section and line overhead.

The main functions of network management thereby include:
;Network and network-element provisioning
:In order to allocate bandwidth throughout a network, each network element must be configured. Although this can be done locally, through a craft interface, it is normally done through a network management system (sitting at a higher layer) that, in turn, operates through the SONET/SDH network management network.
;Software upgrade
:Network-element software upgrades are done mostly through the SONET/SDH management network in modern equipment.
;Performance management
:Network elements have a very large set of standards for performance management. The performance-management criteria allow not only monitoring the health of individual network elements, but isolating and identifying most network defects or outages. Higher-layer [[network monitoring]] and management software allows the proper filtering and troubleshooting of network-wide performance management, so that defects and outages can be quickly identified and resolved.

Consider the three parts defined above:

===Network management system terminal===
;Local Craft interface
:Local "craftspersons" (telephone network engineers) can access a SDH/SONET network element on a "craft port" and issue commands through a [[dumb terminal]] or terminal emulation program running on a laptop. This interface can also be attached to a [[console server]], allowing for remote [[out-of-band management]] and [[Data logging|logging]].

; Network management system (sitting at a higher layer)
This will often consist of software running on a Workstation covering a number of SDH/SONET network elements

===TL1/Q3 Protocols===

;TL1
SONET equipment is often managed with the [[TL1]] protocol. TL1 is a telecom language for managing and reconfiguring SONET network elements. The command language used by a SONET network element, such as TL1, must be carried by other management protocols, such as [[Simple Network Management Protocol|SNMP]], [[CORBA]], or [[XML]].
;Q3
SDH has been mainly managed using the Q3 interface protocol suite defined in ITU recommendations Q.811 and Q.812. With the convergence of SONET and SDH on switching matrix and network elements architecture, newer implementations have also offered TL1.<ref>{{Cite web |title= Framework for the Integrated Management of Hybrid Circuit/Packet Networks
| date=2003
|url=https://www.ietf.org/lib/dt/documents/LIAISON/ITU-SG4-M3017.htm |access-date=2023-06-15 |website=www.ietf.org}}</ref>

Most SONET [[network element|NEs]] have a limited number of management interfaces defined:

;TL1 Electrical interface
:The electrical interface, often a [[50 Ω|50-ohm coaxial cable]], sends SONET TL1 commands from a local management network physically housed in the [[telephone exchange|central office]] where the SONET network element is located. This is for local management of that network element and, possibly, remote management of other SONET network elements.

===Dedicated embedded data communication channels (DCCs)===

: SONET and SDH have dedicated data communication channels (DCCs) within the section and line overhead for management traffic. Generally, section overhead (''regenerator section'' in SDH) is used. According to [[ITU-T]] G.7712, there are three modes used for management:<ref name="G.7712"/>
:*[[Internet Protocol|IP]]-only stack, using [[Point-to-Point Protocol|PPP]] as data-link
:*[[Open Systems Interconnection|OSI]]-only stack, using LAP-D as data-link
:*Dual (IP+OSI) stack using PPP or LAP-D with tunneling functions to communicate between stacks.

To handle all of the possible management channels and signals, most modern network elements contain a router for the network commands and underlying (data) protocols.