• No results found

1731310019 RTP

N/A
N/A
Protected

Academic year: 2020

Share "1731310019 RTP"

Copied!
20
0
0

Loading.... (view fulltext now)

Full text

(1)

RTP REAL TIME TRANSPORT PROTOCOL

BY RAGAVENDRA

A(1731310019)

(2)

PRESENTATION OUTLINE

 Overview

 Introduction  What is RTP

 Protocol structure  RTP generalities  RTP packets

 Working of RTP  RTCP

(3)

OVERVIEW

The Real-time Transport Protocol defines a

standardized packet format for delivering audio and video over networks

->

It provides transparent transfer of data between end users

USAGE:

 Faster

 Avoid Starvation

 Monitoring services

 Independent of network protocol

(4)

INTRODUCTION

 RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony,

video teleconference applications, television services and web-based push-to-talk(instant messaging) features.

ORIGIN:

 Developed by the Audio-Video Transport Working Group of

the IETF(Internet Engg Task Force)

 H. Schulzrinne (Columbia University)

 S. Casner (Packet Design)

 R. Frederick (Blue Coat Systems Inc.)

 V. Jacobson (Packet Design)

 First published as RFC 1889 in the year 1996

(5)

WHAT IS RTP

RTP consists of two components a data and a control part. The latter is called RTCP.

 The data part of RTP is a thin protocol providing support

for applications with real-time properties such as

continuous media (e.g., audio and video), timing reconstruction,

loss detection,

security and content identification.

 RTCP provides support for real-time conferencing of

groups of any size within an internet. This support includes:

Source identification and support for gateways like

audio and video bridges

(6)

PROTOCOL STRUCTURE

Application layer protocol

Typically used on top of UDP

Applications that use RTP are:

Less sensitive to packet loss Very sensitive to packet delays

UDP provides key services:

(7)

RTP GENERALITIES

 carry data that has real-time properties

 Simple Multicast Audio Conference  Audio and Video Conference

 Scalable: unicast, multicast, from 2 to 

 Timing:

 intra-media synchronization: remove jitter with playout buffers

(8)

GENERAL SCENARIO

 One-to-one  One-to-many  Many-to-many  Local

transmission

(access within

one machine)

 RTCP (Sender

and

(9)

RTP PACKETS

 Consist of RTP header, optional payload headers and the

payload itself

 RTP overhead = 12 bytes

 IP+UDP+RTP overhead = 20+8+12 = 40 bytes

 It is advisable to keep coded slice sizes as close to, but never

bigger than, the MTU size (largest size of a packet that can be transmitted without being split/recombined on the transport and network layer), because:

1. It optimizes the payload/header overhead relationship

2. Minimizes the loss probability of a (fragmented) coded slice due to the loss of a single fragment on the network/transport layer and the resulting discarding of all other fragments belonging to the coded

slice

 MTU sizes: ~1500 bytes for wireline IP links (max. size of an

(10)

RTP PACKET FORMAT

V) Version; 2 bits (P) Padding; 1 bit.

(X) Extension; 1 bit. (CC) CSRC Count; 4 bits.

(M) Marker; 1 bit. (PT) Payload Type; 7 bits.

Sequence Number; 16 bits. Time Stamp; 32 bits.

(11)

PACKET HEADER INFO:

RTP header contains the following:

 sequence number (used for packet-loss

detection),

 timestamp (timing information,

synchronization of media streams),

 Payload type (identifies the media codec of the

payload),

 marker bit (detecting the end of a group of

related packets),

 source identifiers(contributing and

(12)

HOW RTP WORKS

Ip header->udp header->RTP header ->RTP Video Payload Ip header->udp header->RTP header

->RTP audio payload

 Video and audio payloads are sent separately

 Uses sequence number to synchronise audio and

(13)

RTP SESSION

RTP session is sending and receiving of RTP data by a group of participants

For each participant, a session is a pair of transport addresses used to

communicate with the group

 If multiple media types are communicated by the group, the

(14)

RTP BASIC DATA TRANSMISSION

Same synchronous source Different seq no

Different payloads and timestamp

End user

(15)

RTCP

 Real-time Transport Control Protocol (RTCP) for transmitting

control information.

It consists of a data and control (RTCP) component that work

together.

 It provides support for streaming data, Timing reconstruction, loss

detection, etc.

This is the control part of RTP, and provides the following functions:

 Data delivery monitoring

 Source identification

(16)

CONTD…

Which port numbers do they use?

RTP or RTCP are not assigned any well-known port number.

The port numbers are assigned on demand.

Restriction:

For RTP, port number must be even.2p For RTCP, port number must be odd.2p+1

The control protocol RTCP is used to specify quality of service

(QoS) feedback and synchronization between the media streams.

 The bandwidth of RTCP traffic compared to RTP is small,

(17)

EG: SIMPLE MULTICAST AUDIO

CONFERENCE

1. Call connection established

2. Audio sampled at 20ms durations

3. Each data chunk is packaged with an RTP header

4. RTP packet is wrapped around UDP packet 5. Sent through network

6. Receiver receives and parses RTP header

(18)

MIXER AND TRANSLATOR

Accommodate participant network resources

->Mixer – Low Bandwidth

->Mixer – Combining media streams

(19)

PAYLOAD FORMATS

Media types:

 Application -> smpte336m  Application -> H.261

 Audio -> ac3

 Audio ->attrac3 (44100-clockrate)  Text -> rtx

 Text -> ulpfec

 Video ->h263 (90000-clockrate)  Video ->nv ……..etc

(20)

CONCLUSION

 RTP provides powerful instruments for

adaptive video transmission

 Potential applications include wireless links  Optimization can be done within the frames of

References

Related documents

Det ”å groove” dreier seg med andre ord ikke om å spille samtidig etter en fastlagt ”ytre” puls, men heller å spille omkring en puls eller ”beat” som musikerne

Changes population structure: generates genetic diversity (new mosaic genes, reassortment of genes, sharing of genes)... Sex and Bacteria - Diversity and Population Structures Low

In this story: Jesus said to Mary, “Did you not know that I must be in my Father’s House?” Mary referred to Joseph as Jesus’s father, and Jesus reveals that His father is

Polarization studies revealed that these compounds behave as mixed type inhibitors and inhibit corrosion by parallel adsorption on the surface of stainless steel due to

To help address disruptive physician behaviour, medical organizations are establishing programs to help doctors change their behaviour, particularly in the context of

1801: Pie chart, circle graph invented- William Playfair 1819: First modern statistical map (illiteracy in France)- Charles Dupin 1844: variable- width, divided bars, area

The RING formula helps marketers understand and diagnose important information about the contribution their inbound programs are making to the bottom line: Revenue desired

In short, preventing bribe payments must be treated as an ethical issue, not just a legal compliance issue, and the corporation must actively manage its corporate culture to ensure