Overview - ISO/IEC 23009-5:2017 (SAND)
ISO/IEC 23009-5:2017 defines Server and Network Assisted DASH (SAND) as an extension to Dynamic Adaptive Streaming over HTTP (DASH). The standard specifies a functional SAND architecture, the semantics of SAND messages exchanged among DASH clients, DASH aware network elements (DANE) and metrics servers, an encoding scheme for those messages, and the transport/delivery protocols to carry them. Its purpose is to improve streaming efficiency and Quality of Experience (QoE) by enabling real‑time exchange of operational and client status information.
Key Topics and Technical Requirements
- SAND reference architecture: identifies network elements (e.g., DASH clients, DANE, metrics servers) and interfaces for SAND message exchange.
- SAND messages: formalizes message classes used in SAND - metrics, status, Parameters Enhancing Reception (PER) and Parameters Enhancing Delivery (PED) - and defines their semantics.
- Message encoding and format: includes an XML schema for SAND messages (normative annex) and MIME type registration guidance.
- Transport and delivery protocols: specifies message delivery mechanisms and optional transports such as WebSocket, attachment to HTTP requests, and MPD signaling.
- Signalling and metadata: details how to signal SAND channels via the MPD and how to report metrics through SAND protocols.
- Normative references & conventions: interoperates with ISO/IEC 23009-1 (DASH MPD/segment formats), ISO 8601, and relevant IETF RFCs (e.g., WebSocket RFC 6455, HTTP range requests RFC 7233).
Practical Applications - Who Uses ISO/IEC 23009-5 (SAND)
- CDN and network operators: use SAND to inform delivery decisions (caching, prioritization, resource allocation) based on real‑time network and client metrics.
- Streaming service providers and OTT platforms: leverage SAND for improved adaptive bitrate decisions, reduced rebuffering and better QoE insights.
- Device and client implementers: report client buffer levels, representation switches, and throughput metrics to networks/servers to enable assisted delivery strategies.
- Streaming architects and engineers: design systems that combine DASH MPDs with SAND signalling for dynamic optimization across servers, proxies, and edge elements.
- Monitoring and analytics teams: collect standardized metrics from clients and network elements for operational visibility and SLA enforcement.
Related Standards (applicable)
- ISO/IEC 23009-1 - DASH Media Presentation Description (MPD) and segment formats
- IETF RFC 6455 - WebSocket Protocol (optional transport)
- IETF RFC 7233 - HTTP Range Requests
- ISO 8601 - date/time representation
By standardizing message semantics, formats and transport, ISO/IEC 23009-5 (SAND) enables interoperable server- and network-assisted enhancements to DASH streaming-helping stakeholders reduce stalls, optimize bandwidth use, and improve viewer experience.
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