USING TCP FOR REAL TIME MULTIMEDIA APPLICATIONS

R. Lavanya Sree

M.Sc Software Engineering

Sri Krishna College of Engineering and Technology

Abstract

In this paper, we investigate

exactly this question. Our test bed-based and

public Internet experiment results show that

the combination of a relatively modest

extension to TCP, what we call real-time

mode (RTM), and several application

techniques allow real-time applications to

operate well over TCP, making all the

benefits of TCP, including error recovery,

available to the real-time application

developers.

Introduction

TCP is the most well-developed,

extensively used and widely available

Internet transport protocol. Years of

extensive network research has resulted in

numerous improvements to the protocol and

its implementation, including slow-start,

congestion back-off and fast retransmit.

TCP-RTM Modification

1. TCP-RTM Packet Reception

TCP is modified to support real-

time mode (RTM) by two simple

changes to the TCP packet reception

algorithm, namely:

1. On application-level read on the

TCP connection.

2. On reception of an out-of-order

packet with a sequence number logically

greater than the current receive pointer (rcv

next ptr).

2. TCP Framing

A TCP-RTM application uses

application-level framing (ALF) [15] to

recognize and handle TCP-level packet loss

that may occur, as described above.

3. Sender-side TCP-RTM

In general, the sender’s send

buffer should be large enough to

accommodate all the data segments that

have not been acknowledged and that are to

be transmitted

Using TCP-RTM and Application-level

Techniques

A few simple application level

techniques enable real time multimedia

applications to operate well over TCP-

RTM.We describe these techniques in the

following subsections.

1. TCP-sized Playback Buffer

Real-time streaming

applications use a playback buffer to

insulate the playback from jitter arising from

the variable delay through the Internet.

2. Application-Level Heartbeat

A TCP-RTM real time

application is programmed to periodically

send an application-level packet back to the

source if it has not received any data within

the heartbeat time period

3. Framing Techniques

For applications with fixed-

sized frames, typically true for audio

applications, the following method is

generally sufficient.

4. RTM Receiver

A TCP-RTM receiver

application uses non-blocking read and

always has the read complete immediately,

only returning no data when there is no data

at all that has been received since the last

read.

Further section describes about the

application of the real time multimedia

works.

Conclusion

TCP-RTM provides a new mode for

TCP that allows it to support a range of real-

time applications with performance superior

to using a basic datagram service such as

UDP.

Second, we showed how structuring

an application to use the TCP buffering for

the playback buffer together with fast

retransmit allows retransmission on packet

loss without introducing jitter at normal

levels of network packet drop.

Finally, we showed that a minor

modification to the SACK implementation

enables TCP to provide congestion response

that is compatible to regular TCP, whet

her in RTM mode or not.