Internet Video

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Internet & Video

Salvatore [email protected]

www.sloreto.comMay 21st, 2009

mailto:[email protected]

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Outline❒Internet Video vs IPTV❒MultiMedia Streaming❒The Internet Stability❒UDP a challenge for the future❒Suggestions

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Internet Video vs IPTVInternet Video:

Internet Video runs on top of the Best Effort network

❒ Challenge: Deal with multimedia in a best-

effort network: technical challenges

IPTV:

Is a provider offered, managed service with certain quality of service requirements.

❒ The provider does not simultaneously broadcast everything due to limited bandwidth on the access network

❒ Challenge:How the Internet might evolve

to better support multimedia?

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MultiMediaFundamental

characteristics:

❒ Typically delay sensitive❍ end-to-end delay❍ delay jitter

❒ But loss tolerant: infrequent losses cause minor glitches

Classes of MultiMedia:

1) Streaming stored

2) Streaming live

3) Real-time interactive

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Streaming Stored Multimedia

Streaming: ❒ media stored at source❒ transmitted to client❒ streaming: client playout

begins before all data has arrived

❒ timing constraint for still-to-be transmitted data: in time for play out

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Streaming Stored Multimedia: Interactivity

❒ VCR-like functionality: client can pause, rewind, FF, push slider bar❍10 sec initial delay OK❍1-2 sec until command effect OK

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Streaming Live MultimediaExamples:❒ Internet radio talk show❒ Live sporting event

Streaming❒ play can lag tens of seconds❒ still have timing constraint (but shorter delay

required)Interactivity❒ fast forward impossible❒ rewind, pause possible!

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Interactive, Real-Time Multimedia

❒ end-end delay requirements:❍ audio: < 150 msec good, < 400 msec OK

• includes application-level (packetization) and network delays

• higher delays noticeable, impair interactivity❒ session initialization

❍ callee be able to advertise its IP address, port number, encoding algorithms.

❒ applications: IP telephony, video conference, distributed interactive worlds

Multimedia telephony services-P2PSIP realization

UE B

DSNSN A

AAA server

UE A SN E

❒ P2PSIP in an IETF protocol that uses the Session Initiation Protocol (SIP) for establishing and managing sessions in a Peer to Peer network. In this scenario the DHT are only used to discover the peer to communicate with.The streaming for the call happens end to end.

Streaming services-PPSP realization

❒ Peer to Peer Streaming Protocol (PPSP)the aim of this protocol is locating and transmitting real-time data efficiently from multiple sources with different pieces in peer to peer environment.

Distribute Service Network

Content distribution

It is not clear yet if a pure P2P distribution is good for streaming and especially for live streaming!

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The Internet Stack

IP

TCP/UDP

APPLICATION

Link

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The Internet Stability

The stability of the Internet is what allow everybody to send and receive data on the Internet without occupy all the available bandwidth.

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❒ The stability of the Internet is due to the TCP congestion control algorithm

❒ ...Indeed almost all the Internet traffic nowadays is over TCP

❒ ...This is the reason for which many Web sites (e.g. Youtube) that host small length and low resolution videos use only pseudo-streaming technologies that are based on the simple TCP download

❒ ...In this way the generated traffic is not harmful for the stability of the Internet

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Streaming from Web Server❒ multimedia files stored in

Web servers❒ Browser requests file with

HTTP request message❒ Web server sends file in

HTTP response message❒ Content-type header line

indicates an audio/video encoding

Browser launches media player, and passes file to media player

Browser launches media player and passes it the meta file. Player sets up a TCP connection with server and sends HTTP request

Open Issues❒ How to improve

HTTP streaming❒ HTML 5

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❒ ...moreover, it is not clear if the perceived quality is satisfactory for the user

❒ ...indeed TCP doe not provide content delivery within delay constrains

❒ ...the TCP congestion control is not optimal for VoIP/Multimedia application

As consequence, audio and video applications are in practices transported by hidden proprietary protocols using the UDP protocol

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UDP a challenge for the future

❒ UDP protocol does not employ a congestion control neither a retransmission mechanism

❒ ... that means that it can an application using UDP can consume all the available bandwidth causing congestion

However the usage of UDP is increasing lately for different reasons. The mains are:

❒ UDP works very well with the NAT❒ UDP is optimall for multimedia streams

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❒ ...multimedia streaming service can tolerate some low packet loss percentage,but require more tight quality of service (QoS) requirements in terms of:

- end-to-end delay - jitter

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❒ RTP/RTCP/RTSP are protocols that have been designed to run on top of UDP, to transport multimedia streaming

RTP:

provides❒ Payload type

identification❒ Sequence numbering❒ Time-stamping

RTCP:

provides❒ Minimal control to the

application❒ Quality monitoring

service for RTP transport

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RTSP/RTCP/RTP

HTTP GET

mediaplayer

Webserver

mediaserver

Webbrowser

client server

presentation desc.

RTSP

RTCP

RTP

RTSP: Real-Time Signaling ProtocolRTCP: Real-Time Control ProtocolRTP: Real-Time Transport Protocolc

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RTSP: Initialization and Control

HTTP GET

SETUP

PLAY

media stream (RTP)mediaplayer

Webserver

mediaserver

Webbrowser

clientserver

presentation desc.

TEARDOWN

PAUSE

RTCP

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❒ ...UDP lacks congestion control algorithms

❒ … however High-bandwidth UDP applications must implement congestion control themselves - a difficult task – or risk rendering congested network unusable!

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❒ ...RTP/RTCP/RTSP do not provide any congestion control neither

❒ ..so all the applications that use RTP/RTSP to transport media (e.g. Skype) SHOULD implement a proprietary form of congestion control algorithm to reduce the sending rate when a big packet loss rate is measured

The problem is that those proprietary algorithms are much more aggressive that the TCP one!

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Is not clear YET the impact of Multimediatraffic on the Stability of the Internet when a VERY large amount of this traffic will populate the network

It is a challenge to Telecom operators and ISP both from the point of view of

❒ business model and ❒ network stability

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SuggestionsFrom a protocol point of view, -there is a need to standardize and implement the

right algorithm:❒ e.g. RFC 5348 “TCP Friendly Rate Control

(TFRC) Protocol Specification”

-there is a need to recover from relatively infrequent and short bursts of loss using a combination of video and packet recovery mechanisms and protocols e.g.:

❒ Forward Error Correction (FEC)❒ Retransmission approach based on RTP/RTCP

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Suggestions

From a network point of view,there is a need to increase the bandwidth and improve its usage

❒ the optical Broadband (for the wireline)❒ Multimedia Broadcast Multicast Service (MBMS) (for

the wireless)

Q&A

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RTMP – Real Time Messaging ProtocolReal Time Messaging Protocol (RTMP) is a

proprietary protocol developed by Adobe System for streaming audio, video and data over the Internet, between a Flash player and a server.

• It works on top of TCP• Or can be encapsulated within HTTP requests to

traverse firewalls.

There are also other companies working on similar protocol based on TCP or encapsulated in HTTP e.g. Apple

Datagram Congestion Control Protocol (DCCP) ( RFC 4340)Is a new transport protocol that adds o a UDP-

like foundation the minimum mechanisms necessary to support congestion control.

It is a message-oriented and implements:- Reliable connection setup, teardown- ECN- Congestion control- Feature negotiation

Internet Video

Technology

Transcript of Internet Video