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Home : ITU-T Home : Study Groups : Study Group 15
Question 9/15 – Transport equipment and network protection/restoration
(Continuation of Question 9/15)


The explosive growth of the Internet and standardisation of 40 and 100Gbit/s Ethernet and other packet based traffic are the key drivers for the development of new transport equipment and network protection and restoration related standards. In addition, the development of the Optical Transport Network (OTN) provides the ability to dramatically increase the bandwidth, and thus traffic carrying capacity, of optical networks. Furthermore, the advent of the Generic Framing Procedure (GFP), Virtual Concatenation (VC) and the Link Capacity Adjustment Scheme (LCAS) has enabled efficient data traffic transport over Synchronous Digital Hierarchy (SDH) and OTN. This enhanced capability has resulted in a need for the revision of existing recommendations as well as the development of new recommendations for data equipment such as Ethernet, Multi-Protocol Label Switching (MPLS) and other packet-based transport equipment. Other functional enhancements such as multicast and broadcast must also be developed. Regarding the emergence of Ethernet, it is necessary to distinguish between Ethernet as a client signal and Ethernet as a packet transport technology. In order to ensure these new transport networks achieve carrier-class performance, it is essential that the necessary OAM functionality and network management capabilities be taken into account in the development of transport equipment Recommendations.

Responsibilities under this Question include the following areas of standardization related to these new technologies:

  • Specification of all equipment functions, supervision and protection switching processes related to the OTN and SDH layer networks including equipment functions related to access networks such as SDH/DSL, OTN/DSL and Ethernet/DSL adaptation functions
  • Specification of equipment functions, supervision and protection switching processes for transport of data/packet traffic (e.g., IP, ATM, MPLS, MPLS-TP, Ethernet, other packet-based transport technologies, Storage Area Networks (SAN)) via transport networks
  • Specification of survivability capabilities and development of a strategy for multi-layer survivability interactions (including those where different transport technologies are used at different layers)
  • Examination of Synchronous Ethernet and the impact on synchronization layer functions, which may differ for transport of different client layers (e.g., IP traffic)
  • Specification of fundamental transmission parameters and determination of the effect of various transmission impairments. This includes transmission error and availability performance objectives and allocation methods for efficient design of digital networks and associated transmission equipment.
  • Investigation of power saving mechanisms for transport network equipment in the wider context of ICTs (Information and Communications Technologies).

Recommendations related to transport technologies (e.g., SDH, PDH, OTN, MPLS-TP, Ethernet and other packet-based transport technologies) used in the access environment and not covered by other Questions of ITU-T SG15, such as Flexible Multiplexers, are also covered by this Question. The following major Recommendations, in force at the time of approval of this Question, fall under its responsibility: G.705, G.781, G.783, G.798, G.806, G.841, G.842, G.808.1, G.821, G.826, G.827, G.828, G.829, G.873.1, G.8021, G.8031, G.8121, G.8131, G.8201, I.630 and Y.1720.


What transport equipment functions must be specified to enable compatible transport equipment in inter-office and long distance networks, including evolution to the optical transport network?

What additional characteristics of transport equipment should be recommended to provide enhanced survivability capabilities and a cohesive strategy for multi-layer survivability interactions?

What characteristics should be recommended for equipment for the transport of packet based traffic such as MPLS, MPLS-TP, Ethernet, other packet-based transport technologies, SAN and IP?

What transmission error performance parameters and objectives need to be recommended?

Study items to be considered include, but are not limited to:

  • Enhancement and extension of transport equipment Recommendations
    – for the SDH and OTN (OTN equipment in this context relates to equipment functions and the assembly of optical components and sub-systems)
    – to support the development of CBR transport over packet based networks
  • Transport equipment Recommendations to provide enhanced survivability capabilities and a cohesive strategy for multi-layer survivability interactions. This includes revisions to Recommendations G.841, G.842, G.808.x, I.630, G.8031/Y.1342, G.8131/Y.1382 and Y.1720. These Recommendations cover SDH, OTN, ATM, MPLS, MPLS-TP and Ethernet layer protection, as well as multi-layer survivability, including interactions with protection at data/packet layers
  • Ring protection mechanisms for packet transport networks including Ethernet (G.8032/Y.1343)
  • Specifications of Equipment functions necessary
    – to implement an Automatically Switched Optical Network (ASON)
    – for the transport of packet based traffic such as MPLS-TP, Ethernet services, and SAN
  • Enhancements to SDH equipment characteristics or network protection protocols to support paths with longer delay times, such as satellite systems, submarine cable systems, radio relay systems or systems with numerous regenerators.
  • Enhancements required to the transport equipment Recommendations in order to meet the needs of
    – the access network
    – the NGN and transport of Internet and other packet based traffic. This includes examining the impact, if any, on synchronisation layer functions
  • Clarification and resolution of technical issues in published and draft Recommendations.
  • Impact on equipment functions (such as protection switching) due to different characteristics of satellite networks (e.g., longer delay times).
  • What transport equipment functions should be specified to allow power savings within transport networks?


Tasks include, but are not limited to:

  • Enhancement to relevant Recommendations for Ethernet (as a client or as a server) networks to accommodate 100Gbit/s Ethernet services
  • Complete Recommendation G.808.2 (ex G.gps-2)
  • Complete Recommendation G. 873.2 (ex G.otnprot-2)
  • Enhancements to OTN protection mechanisms, for example nested and M:N ODUk SNC
  • Revisions to Recommendation G.798
  • To maintain and update, as necessary, the error performance recommendations G.821, G.826, G.827, G.828, G.829 and G.8201
  • Enhancements to the Recommendation for equipment for Ethernet (as a client or as a server) services (G.8021/Y.1341)
  • Enhancement and improvement of Recommendation on characteristics of packet-based transport network equipment functional blocks
  • Enhancement to Recommendations for Ethernet (as a client or as a server) linear protection switching (G.8031/Y.1342)
  • Enhancement to Recommendations for other survivability techniques including per packet priority-based protection switching for packet based transport networks
  • Development of ring protection mechanisms for Ethernet (as a client or as a server) (G.8032/Y.1344)
  • Enhancement and improvement of linear and ring protection switching Recommendations
  • Clarification of relationships between protection switching and restoration technologies
  • Clarification of relationships between survivability function of a packet-based transport and survivability function in other layers or other transport technologies (e.g., SDH, OTN, etc.)
  • Enhancement to relevant Recommendations to include broadcast and multicast functionality
  • Enhancement to relevant Recommendations to include partial protection switching in rooted multipoint service (RMPS)
  • Maintain and update of MSR
  • Develop additional Recommendations from progress on the above study items.
  • Develop a revised version of Recommendation G.8121/Y.1381 "Characteristics of Transport MPLS (T-MPLS) equipment functional blocks" and Recommendation G.8131/Y.1382 “Linear protection switching for Transport MPLS (T-MPLS) networks” to align with the MPLS-TP architecture and include the appropriate normative references to the MPLS-TP RFCs that are being developed to address the requirements of the transport network. Update the title to replace T-MPLS with MPLS-TP to reflect the new contents.

NOTE: An up-to-date status of work under this Question is contained in the SG15 Work Programme at




  • G.707, G.709, G.784, G.825, G.957, G.959.1, G.7710, G.693, G.694, G.698, G.8080, G.8010, G.8110, G.8110.1, G.8251, G.8261, G.8262, G.8264, G.993.x, Y.2601 and Y.2611


  • Q3/15, Q4/15, Q6/15, Q10/15, Q11/15, Q12/15, Q13/15, Q14/15, and 15/15.

Study Groups:

  • ITU-T SG2 responsible for telecommunication management
  • ITU-T SG13 responsible for NGN aspects
  • ITU-R SG9 responsible for Radio-relay systems
  • ITU-T SG12 responsible for Ethernet and MPLS error performance

Standardization bodies, forums and consortia:

  • IETF working groups related to MPLS-TP and MPLS-TP Equipment and protectiom
  • MEF on Ethernet Equipment
  • IEEE 802.1, 802.3 on Ethernet Equipment
  • IEEE 802.17 on Ethernet Ring protection
  • IP/MPLS Forum


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Updated : 2008-12-23