Streaming Media Protocols

Jani HautakorpiHenry Pohan

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Contents

• Protocols and languages – Overview• Session control – RTSP and SIP• Media description – SDP• Media transportation – RTP• 3GPP Packet-Switched Streaming Service (PSS)• Protocols in 3GPP PSS• 3GPP PSS Domain Architecture & Framework• 3GPP PSS Release 6 extensions• Summary

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Protocols and Languages – Overview

Session control• RTSP• SIP• H.323• SAP• WSP

Media descrip.• SDP• SMIL• CC/PP

Media transpor.• RTP• HTTP

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Session Control – RTSP (1/2)

• Real-Time Streaming control Protocol• Used in streaming communication• Transaction-oriented, request-response protocol• Text-based, data is carried out-of-band• Messages can contain a message body• Example methods: play, forward, rewind, pause, …• Current development: Usage with NATs, key

management extension.

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Session Control – RTSP (2/2)

Client Server

SETUP200 OK

PLAY200 OK

TEARDOWN

200 OK

Media

Has SDP

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Session Control – SIP (1/2)

• Session Initiation Protocol• Mostly used with conversational media (preliminary

discussion on the use with streaming media)• Very popular protocol (used e.g. in IMS)• Very similar to RTSP (text-based, request-response,

data out-of-band)• Current development: Security and privacy

extension, integration with QoS mechanisms, …

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Session Control – SIP (2/2)

Initiator Responder

INVITE180 Ringing

200 OKACK

BYE200 OK

Media

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Media Description – SDP (1/2)

• Session Description Protocol• Widely deployed• Carried as a payload of session control protocol• Text-based• Capability negotiation (offer/answer model)• Current development: Offer/answer model,

exchange of encryption keys, SDPng, …

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Media Description – SDP (2/2)v=0o=bill 2890844526 2890842807 IN IP4 193.34.4.2s=Streaming media protocolsi=A presentation on the media protocolsu=http://www.barfoo.com/bill/media.pse=bill@barfoo.com (Bill Huxton)c=IN IP4 193.3.44.21t=2873397496 2873404696

a=recvonlym=audio 49170 RTP/AVP 0m=video 51372 RTP/AVP 31m=application 32416 udp wba=orient:portrait

Sess

ion

Med

ia

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Media Transportation – RTP

• Real-time Transport Protocol• Dominant streaming media transport protocol• Runs usually on top of UDP• Accompanied with RTCP• Binary protocol• Can also transport encrypted media

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Packet-Switched Streaming Service (PSS)

• PSS – an umbrella standard (IETF, 3GPP, W3C, MPEG, ITU)– Signaling and control protocols (RTSP and SDP from IETF) – Transport protocols (RTP, RTCP, and various payload formats from IETF) – Audio codecs (AMR and AMR-WB from 3GPP, AAC from MPEG-4) – Visual codecs (H.263 from ITU, Simple Visual Profile from MPEG-4) – File format (MP4 file format from MPEG-4 Systems) – Scene description (SMIL from W3C)

• 3GPP PSS Versions:– Release 4 – 1st version, Q1 2001– Release 5 – Q2 2002– Release 6 – Q3 2004

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3GPP PSS – Protocols

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3GPP PSS – Protocol Stack

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3GPP PSS – Domain Architecture• Streaming Client & Content Server

– main component• Proxy Server

– provide QoS streaming service• User and Profile Servers

– keep user preferences and device capabilities• Content Cache (optional)

– for improving overall service quality• Portals

– servers for convenient access to streamed media content• SGSN

– gateway betwen user equipments within its serving area (UEs) • GGSN

– gateway between UMTS core network and internet (IP-PDN)

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3GPP PSS – Domain Architecture (cont.)

StreamingClient

ContentServers

User andterminalprofiles

Portals

IP Network

Content Cache

UMTS Core Network

UTRAN

GERAN

SGSN GGSNGi

Gb

Iups

StreamingClient

Internet Multimedia Subsystem (IMS)

Proxy

Gi

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PDP Context Activation Procedure

UE SGSN

Activate PDP Context Request

Security Functions

RAB Assignment Request

Create PDP Context Response

Activate PDP Context Accept

Radio Bearer

GGSNUTRAN/GERAN

RAB Assignment Response

Create PDP Context Request

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Streaming Multimedia Session Establishment in PSS

UEPresentation and Content Server

[RTSP] DESCRIBE

[RTSP] 200 OK

[RTSP] SET UP

[RTSP] 200 OK

[RTSP] PLAY[RTSP] 200 OK

GGSN

Primary PDP Context Activation

Secondary PDP Context Activation

RTP and RTCP flows

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3GPP PSS Release 6 Some Extensions• 3GPP file format:

– General profile– Progressive-download profile– Streaming server profile

• DRM for Streaming– Based on OMA DRM 2.0

• Quality of experience– At the end of the session end user experience is reported back to the server– Metrics: rebuffering duration, initial buffering duration, successive loss of RTP packets.

• Adaptive Streaming– Adaptation of transmission and content rates to the available network resources

• Avoid network buffer overflow• Avoid client buffer underflow/overflow• Highes possible quality of experience

– Client buffer feedback using RTCP is defined– Server centric approach (implementation specific):

• Estimation of available network resources• Setting of transmission and content rate

Interworking with charging / billing services for next 3GPP PSS release…?

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Summary

• Media sessions require three components:– Session control protocol– Session description language– Media transportation protocol

• 3GPP PSS is standard specification at application layer that evolved from simple streaming service (Rel. 4) to more advanced one (Rel. 5 & Rel. 6) with concern in backwards compatibility.

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References• Sudhir Dixit and Tao Wu, Content Networking in The Mobile Internet• H. Schulzrinne et al., Real Time Streaming Protocol (RTSP), IETF, RFC 2326,

proposed standard, 1998.• J. Rosenberg et al., SIP: Session Initiation Protocol, IETF, RFC3261, proposed

standard, 2002.• M. Handley and V. Jacobson, SDP: Session Description Protocol, IETF, RFC

2327, proposed standard, 1998.• H. Schulzrinne et al., RTP: A Transport Protocol for Real-Time Applications,

IETF, RFC 3550, standard, 2003.• 3GPP TS 26.233 Transparent end-to-end packet switched streaming service

(PSS); General description (Release 6). • 3GPP TS 26.233 Transparent end-to-end packet switched streaming service

(PSS); Protocols and codecs (Release 6). • 3GPP TS 26.233 Transparent end-to-end packet switched streaming service

(PSS); Stage 1 (Release 6). • Presentation Slide from Ericsson Research in Aachen, Status of the 3GPP PSS

(Packet-Switched Streaming) Standard, June 2004.

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Questions, comments?