Internet & Video
Salvatore Loreto
Salvatore.loreto@ieee.org
www.sloreto.com
May 21st, 2009
1

Outline
Ì Internet Video vs IPTV
Ì MultiMedia Streaming
Ì The Internet Stability
Ì UDP a challenge for the future
Ì Suggestions
2

Outline
Ì Internet Video vs IPTV
Ì MultiMedia Streaming
Ì The Internet Stability
Ì UDP a challenge for the future
Ì Suggestions
3

Internet Video vs IPTV
Internet Video: IPTV:
Internet Video runs on Is a provider offered,
top of the Best managed service with
Effort network certain quality of
service requirements.
Ì Challenge: Ì The provider does not
Deal with multimedia in a best- simultaneously broadcast
effort network: everything due to limited
technical challenges bandwidth on the access
network
Ì Challenge:
How the Internet might evolve
to better support
multimedia?
4

Outline
Ì Internet Video vs IPTV
Ì MultiMedia Streaming
Ì The Internet Stability
Ì UDP a challenge for the future
Ì Suggestions
5

MultiMedia
Classes of MultiMedia: Fundamental
characteristics:
1) Streaming stored
Ì Typically delay sensitive
r end-to-end delay
2) Streaming live r delay jitter
3) Real-time interactive Ì But loss tolerant:
infrequent losses cause
minor glitches
6

Streaming Stored Multimedia
Streaming:
Ì media stored at source
Ì transmitted to client
Ì streaming: client playout
begins before all data has
arrived
Ì timing constraint for still-to-be
transmitted data: in time for play
out
7

Streaming Stored Multimedia: Interactivity
Ì VCR-like functionality: client can
pause, rewind, FF, push slider bar
r 10 sec initial delay OK
r 1-2 sec until command effect OK
8

Streaming Live Multimedia
Examples:
Ì Internet radio talk show
Ì Live sporting event
Streaming
Ì play can lag tens of seconds
Ì still have timing constraint (but shorter delay
required)
Interactivity
Ì fast forward impossible
Ì rewind, pause possible!
9

Interactive, Real-Time Multimedia
Ì applications:
IP telephony, video conference,
distributed interactive worlds
Ì end-end delay requirements:
r audio: < 150 msec good, < 400 msec OK
• includes application-level (packetization) and network
delays
• higher delays noticeable, impair interactivity
Ì session initialization
r callee be able to advertise its IP address, port
number, encoding algorithms.
10

Multimedia telephony services
-P2PSIP realization
SN A
DSN
UE A UE B
SN E
AAA
server
Ì 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
Distribute Service Network
Ì 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.

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

Outline
Ì Internet Video vs IPTV
Ì MultiMedia Streaming
Ì The Internet Stability
Ì UDP a challenge for the future
Ì Suggestions
14

The Internet Stack
APPLICATION
TCP/UDP
IP
Link
15

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.
16

The Internet Stability
Ì The stability of the Internet is due to the TCP
congestion control algorithm
Ì ...Indeed almost all the Internet traffic
nowadays is over TCP
Ì ...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
Ì ...In this way the generated traffic is not
harmful for the stability of the Internet 17

Streaming from Web Server
Ì multimedia files stored in
Web servers
Ì Browser requests file with
HTTP request message
Ì Web server sends file in
Browser launches media player, and
HTTP response message passes file to media player
Ì Content-type header line
indicates an audio/video
encoding
Open Issues
Ì How to improve
Browser launches media player and passes it the
HTTP streaming meta file. Player sets up a TCP connection with
Ì HTML 5 server and sends HTTP request 18

The Internet Stability
Ì ...moreover, it is not clear if the perceived
quality is satisfactory for the user
Ì ...indeed TCP doe not provide content delivery
within delay constrains
Ì ...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
19

Outline
Ì Internet Video vs IPTV
Ì MultiMedia Streaming
Ì The Internet Stability
Ì UDP a challenge for the future
Ì Suggestions
20

UDP a challenge for the future
Ì UDP protocol does not employ a congestion
control neither a retransmission mechanism
Ì ... 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:
Ì UDP works very well with the NAT
Ì UDP is optimall for multimedia streams
21

UDP a challenge for the future
Ì ...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
22

UDP a challenge for the future
Ì RTP/RTCP/RTSP are protocols that have been
designed to run on top of UDP, to transport
multimedia streaming
RTP: RTCP:
provides provides
Ì Payload type Ì Minimal control to the
identification application
Ì Sequence numbering Ì Quality monitoring
Ì Time-stamping service for RTP
transport
23

RTSP/RTCP/RTP
HTTP GET
Web Web
browser presentation desc. server
RTSP
media
player RTCP media
server
RTP
client server
RTSP: Real-Time Signaling Protocol
RTCP: Real-Time Control Protocol
RTP: Real-Time Transport Protocolc
24

RTSP: Initialization and Control
HTTP GET
Web Web
browser presentation desc. server
SETUP
PLAY
media media stream (RTP) media
player server
RTCP
PAUSE
TEARDOWN
client
server
25

UDP a challenge for the future
Ì ...UDP lacks congestion control algorithms
Ì … however High-bandwidth UDP applications
must implement congestion control themselves
- a difficult task – or risk rendering congested
network unusable!
26

UDP a challenge for the future
Ì ...RTP/RTCP/RTSP do not provide any congestion
control neither
Ì ..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!
27

UDP a challenge for the future
Is not clear YET the impact of Multimedia
traffic 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
Ì business model and
Ì network stability
28

Outline
Ì Internet Video vs IPTV
Ì MultiMedia Streaming
Ì The Internet Stability
Ì UDP a challenge for the future
Ì Suggestions
29

Suggestions
From a protocol point of view,
-there is a need to standardize and implement the
right algorithm:
Ì 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.:
Ì Forward Error Correction (FEC)
Ì Retransmission approach based on RTP/RTCP
30

Suggestions
From a network point of view,
there is a need to increase the bandwidth and
improve its usage
Ì the optical Broadband (for the wireline)
Ì Multimedia Broadcast Multicast Service (MBMS) (for
the wireless)
31

Q&A
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RTMP – Real Time Messaging
Protocol
Real 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