B.Bharat Shetty 4 th semester CS&E SJCE

DEFNITION: Multimedia is often described as a holy grail by some people.Literally the term multimedia is just two or more media.To be precise “Multimedia” generally means the combination of two or more continuous media i.e. media that has to be played during some well defined interval usually with some user defined interaction. Before Proceeding concept of a protocol must be clear to you

 Multimedia Networking Applications Multimedia Networking Applications  Streaming stored audio and video Streaming stored audio and video  RTSP RTSP  Protocols for Real-Time Interactive Applications  RTP RTP  RTCP RTCP  SIP. SIP.  RSVP RSVP  H.323 standard H.323 standard  Summary Summary

MM Networking Applications Fundamental characteristics: Typically delay sensitive. End-to-end delay. Delay jitter. But loss tolerant: infrequent losses cause minor glitches. Antithesis of data, which are loss intolerant but delay tolerant. Classes of MM applications: 1) streaming stored audio and video 2) streaming live audio and video 3) real-time interactive audio and video Jitter -the variability of packet delays within the same packet stream

Multimedia, Quality of Service: What is it? Multimedia applications: network audio and video (“continuous media”) level of performance needed for application to function. QoS

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 playout

SSM: What Is It? 1. video recorded 2. video sent 3. video received, played out at client Cumulative data streaming: at this time, client playing out early part of video, while server still sending later part of video network delay time

Streaming Stored Multimedia: Interactivity functionality similar to a VCR: client can pause, rewind, FF, push slider bar 10 sec initial delay causes no problem 1-2 sec until command effect OK RTSP often used timing constraint for still-to-be transmitted data: in time for playout

Streaming Live Multimedia Examples: Talk shows over the web. Events brought live to home. Streaming. Playback buffer. Playback can lag tens of seconds after transmission. Still have timing constraint. Interactivity. Fast forward impossible. Rewind, pause possible!

Video servers ATM or SONET Backbone network LDN* Local spooling server switch Customer’s House LDN-local distribution network

User Control of Streaming Media: RTSP RTSP: Client-server application layer protocol. User can control display: rewind, fast forward, pause, resume, repositioning, etc… Disadvantages: Does not define how audio/video is encapsulated for streaming over network. No restrictions on how sm is transported. It can be transported over UDP or TCP. No specifications on how the media player buffers audio/video.

Real-time Protocol (RTP) RTP specifies a packet structure for packets carrying audio and video data. RFC RTP packet provides. Payload type identification. Packet sequence numbering. Timestamping. RTP runs in the end systems. RTP packets are encapsulated in UDP segments. Interoperability: if two internet phone applications run RTP, then they may be able to work together.

RTP Runs on Top of UDP RTP libraries provide a transport-layer interface that extend UDP: port numbers, IP addresses payload type identification packet sequence numbering time-stamping

RTP Header Payload Type (7 bits): Indicates type of encoding currently being used. If sender changes encoding in middle of conference, sender informs the receiver through this payload type field. Payload type 0: PCM mu-law, 64 kbps Payload type 3, GSM, 13 kbps Payload type 7, LPC, 2.4 kbps Payload type 26, Motion JPEG Payload type 31. H.261 Payload type 33, MPEG2 video Sequence Number (16 bits): Increments by one for each RTP packet sent, and may be used to detect packet loss and to restore packet sequence.

Real-time Control Protocol (RTCP)  Works in conjunction with RTP.  Each participant in RTP session periodically transmits RTCP control packets to all other participants.  Each RTCP packet contains sender and/or receiver reports.  Key things: -Number of packets sent. -Number of packets lost. -Inter arrival jitter.

RTCP - Continued - RTP session typically has a single multicast address; all RTP and RTCP packets belonging to the session use the multicast address. - RTP and RTCP packets are distinguished from each other through the use of distinct port numbers. - To limit traffic, each participant reduces his RTCP traffic as the number of conference participants increases.

RTCP Packets Receiver report packets: Fraction of packets lost, last sequence number, average interarrival jitter. Sender report packets: SSRC of the RTP stream,the current time,the number of packets sent and the number of bytes sent. Source description packets: address of sender,sender's name, SSRC of associated RTP stream. Enable mapping between the SSRC and the user/host name.

SIP Session initiation protocol. Comes from IETF. Usually a single module suitable for internetworking. People are identified by names or addresses, rather than by phone numbers. You can reach the callee, no matter where the callee roams, no matter what IP device the callee is currently using.

Calling a Known IP Address Alice’s SIP invite message indicates her port number & IP address. Indicates encoding that Alice prefers to receive Bob’s 200 OK message indicates his port number, IP address & preferred encoding (GSM) SIP messages can be sent over TCP or UDP; here sent over RTP/UDP. Default SIP port number is 5060.

More details

Definition of H.323 standard H.323 is a standard that specifies the components, protocols and procedures that provide multimedia communication services—real-time audio, video, and data communications—over packet networks, including Internet protocol (IP)–based networks. H.323 is part of a family of ITU—T recommendations called H.32x that provides multimedia communication services over a variety of networks

-Emergence of voice-over–IP (VoIP) applications and IP telephony -The absence of a standard for voice over IP meant products that were incompatible. - Such requirements forced the need for a standard for IP telephony. E.g.:Version 2 of H.323—packet-based multimedia communications systems

Data Link Protocol IP TCP UDP H.225 (RAS) H.225 (RAS) RTCP Physical Layer Protocol H.245(call control) Q.931 RTP Control Speech

H.323 Packet Network

INTERNET GATEWAY TELEPHONE NETWORK The H.323 architectural Model for Internet Telephony Terminal Gatekeeper ZONE

Allow two Party and multiparty calls Support parameter negotiation Support Encryption Support Media transport on RTP/RTCP protocols Feature sets are almost similar Similarities b/w H.323 and SIP

H.323SIP ITUITEF YesLargely NoYes MonolithicModular Full Protocol StackHandles only setup BinaryASCII YesNo Host or Telephone noURL NoYes Large and complexModerate 1400 pages250 pages ITEM Designed By Compatibility with PSTN Compatibility with net Architecture Completeness Message Format Multimedia conferences Addressing Instant Messaging Implementation Standards size

RSVP designed at -MIT -PARC -California University. RSVP Features: RSVP is a novel signaling protocol in at least 4 ways: 1.It accommodates multicast, not just point-to- multipoint (one-to-many) reservations. 2.QoS routing can be deployed separately (in more operations, and so is 3.relatively low cost 4. Scalability.

RESERVATION IMPLEMENTATIONS  Reservations are implemented through two types of RSVP messages: PATH and RESV.  The PATH messages are sent periodically from the sender to the multicast address. A PATH message contains flow spec to describe sender template (data format, source address, source port) and traffic characteristics.  RESV messages are generated by the receivers and contains reservation parameters including flow spec and filter spec.

R1 R3R2 R4 S1 S2 H4 H5 H3

R1 R3R2 R4 S1 S2 H4 H5 H3

Multimedia Networking: Summary Video conferencing,distance learning. Distributed networking and sharing of data and info resources. Future holds so much promise. Virtual reality,digital animation,net telephony. Interactivity enabled in all sectors. Next generation internet: Intserv, RSVP, Diffserv. Graphical Analysis Ahead

Multimedia market A graphical analysis

Growth of Multimedia Networks 2003 NETWORKsNETWORKs Years Source: NASDAQ and NASSCOM survey

The real-time challenges However, multimedia networking is not a trivial task. We can expect at least three difficulties. 1. When compared with traditional textual applications, multimedia applications usually require much higher bandwidth. 2. Most multimedia applications require the real-time traffic 3. In addition to the delay, network congestion also has more serious effects on real-time traffic 4. Multimedia data stream is usually bursty

Books: 1.Multimedia Handbook- Jessica Keyes-TMH 2.Computer networks – Andrew Tanenbaum 3.Multimedia systems- a perspective (IEEE) Internet: University of colombia website. 4.IEEE papers on net

B.Bharat Shetty 4 th sem CS&E SJCE