5 System Description

26.2473GPPProgressive Download and Dynamic Adaptive Streaming over HTTP (3GP-DASH)Release 17Transparent end-to-end Packet-switched Streaming Service (PSS)TS

5.1 Overview

Progressive Download and Dynamic Adaptive Streaming over HTTP (3GP-DASH) enables to provide services to deliver continuous media content over Hypertext Transfer Protocol (HTTP) in a sense that all resources that compose the service are accessible through HTTP-URLs and the HTTP/1.1 protocol as specified in RFC 2616 [9] may be used to deliver the metadata and media data composing the service. This enables that standard HTTP servers and standard HTTP caches can be used for hosting and distributing continuous media content. Figure 1 shows the architecture for services using progressive download and Figure 2 shows the architecture for services using 3GP-DASH.

The present document deals with the specification of interfaces between the Client and the Server. Specifically, it defines the formats that may be delivered exclusively over the HTTP interface to enable progressive download and streaming
services.

Figure 1: Architecture for Progressive Download over HTTP

Services using the features described in this specification may be deployed within PSS as specified in TS 26.233 [2] and TS 26.234 [3]. In this case the Progressive Download/3GP-DASH Server may be a sub-function of the PSS server and the Progressive Download/3GP-DASH client may be a sub-function of the PSS client.

Figure 2: Architecture for 3GP-DASH

Services using the features defined in this specification may also be deployed independent of the PSS servers and
clients. In this case the Progressive Download/3GP-DASH client shall support the formats and codecs according to this specification.

Access to services based on the features defined in the present document is introduced in clause 5.2.

The protocol support for services using the features defined in this specification is provided in clause 5.3.

Clients supporting progressive download-based services shall support the features and formats as specified in clause 6 of this specification.

Clients supporting 3GP-DASH shall support the features and formats as specified in clause 7 of this specification.

Clients supporting QoE Metrics and Reporting shall support the features as specified in clause 10 of this specification.

Clients supporting SAND functionality shall support the features as specified in clause 13 of this specification. Figure 2a shows the extended architecture for services for 3GP-DASH using SAND. The new interface between the DASH-Aware Network Element (DANE) and 3GP-DASH enables the SAND functionality.

Figure 2a: Extended architecture for 3GP-DASH using SAND functionality

5.2 Service Access

Service access refers to the method by which a Client initially accesses the service. Service access for services based in the specification can be achieved e.g. by a Media Presentation Description or a URL to the media file.

The service access URL can be made available to a client in many different ways. Clients supporting services based on the features in this specification shall be able to access services that are provided through an HTTP-URL. However, it is out of the scope of this specification to mandate any specific mechanism. A preferred way may be to embed URLs for service establishment within HTML pages.

5.3 Protocols

5.3.1 General

Progressive Download and 3GP-DASH clients shall comply with a client as specified in RFC 2616 [9]. The resource hosting the 3GP files and DASH Segments shall comply with a server as specified in RFC 2616 [9].

Progressive Download and 3GP-DASH clients should use the HTTP GET method or the HTTP partial GET method, as specified in RFC 2616 [9], clause 9.3, to access media offered at HTTP-URLs.

Figure 3 shows a protocol stack for services in the context of this specification. 3GP Files in progressive download as well as Segments based on the 3GPP File Format shall be accessible through HTTP.

Figure 3: Overview of the protocols stack

Transport security in Progressive Download and Dynamic Adaptive Streaming over HTTP (3GP-DASH) is achieved using the HTTPS (Hypertext Transfer Protocol Secure) specified in RFC 2818 [12] and TLS as specified in TLS profile of Annex E in TS 33.310 [23]. In case secure delivery is desired, HTTPS should be used to authenticate the server and to ensure secure transport of the content from server to client.

NOTE 1: The use of HTTPS for delivering Media Segments may inhibit caching at proxies and add overhead at the server and the client.

5.3.2 Partial File Handling

In certain cirumstances, for example in the case of MBMS download delivery of 3GP-DASH content, a file or segment may only be partially available on the HTTP server.

If the application, i.e. the 3GP file format client or the 3GP-DASH client supports the handling of partial files, it shall signal its capability using the partial-file-accept request defined in TS26.346 [42], clause 7.9.2.1, i.e. using the Accept header application/3gpp-partial in combination with e.g. an HTTP GET request. If the application uses a partial-file-accept request, then the application shall also be able to handle the request response as defined in TS26.346 [42], clause 7.9.2.2.

If the 3GP file format server or the 3GP-DASH server supports the handling of partial files, it should support the HTTP response format as defined in TS 26.346 [42], clause 7.9.2.2.