ions that belong to SG15. The three WPs consist of WP1: Focuses on the transport aspects of optical and metallic access systems, home net- works, and smart grid networks. Within this framework, WP1 studies performance, field de- ployment, and installation aspects of fiber-optic cables. WP1 is also interested in aspects of network resiliency and recovery during disaster situations. WP2: Focuses on physical interfaces, transmission characteristics, maintenance, and opera- tion of OTNs. This covers features for network equipment, such as routers, switches, re- peaters, multiplexers, amplifiers, transceivers, and SO forth. WP2 covers maintenance and operations of transport networks, including network protec- tion and restoration, resource optimization, scalability, and network agility with Software- Defined Networks (SDN). The network transport media and technologies covered by WP2 are optical fiber cables; dense and coarse wavelength division multiplexing (DWDM and CWDM) optical systems; OTN, Ethernet, and other packet-based data services. WP3: Focuses on the logical layers of the transport network and their characteristics. This program addresses management and control of transport systems covering Operations, Ad- ministration, and Maintenance (OAM), data center interconnect, and home networking ser- vices. WP3 also focuses on synchronization for frequency and precise time and interwork- ing of access technologies and their characteristics to support 5G back-haul and front-haul networks. Most of the recommendations cited by this book come from Question 13, which is part of WP3 (itself a part of SG15). There is more specific information on Q13 (as it is referred to) in "Chapter 8. ITU-T Timing Recommendations". SG16: Multimedia coding, systems, and applications SG16 is responsible for defining all aspects of multimedia standardization, including terminal architecture, protocols, security, mobility, interworking, and QoS. SG16 covers various digital services, including telepresence, IPTV, audio and video coding, sign