* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download project - GEOCITIES.ws
Survey
Document related concepts
Airborne Networking wikipedia , lookup
Multiprotocol Label Switching wikipedia , lookup
Asynchronous Transfer Mode wikipedia , lookup
Video on demand wikipedia , lookup
Internet protocol suite wikipedia , lookup
Zero-configuration networking wikipedia , lookup
Wake-on-LAN wikipedia , lookup
Recursive InterNetwork Architecture (RINA) wikipedia , lookup
Cracking of wireless networks wikipedia , lookup
Deep packet inspection wikipedia , lookup
UniPro protocol stack wikipedia , lookup
SIP extensions for the IP Multimedia Subsystem wikipedia , lookup
Lifecasting (video stream) wikipedia , lookup
Transcript
B.Bharat Shetty 4th 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 Streaming stored audio and video RTSP Protocols for Real-Time Interactive Applications RTP RTCP SIP. RSVP H.323 standard Summary MM Networking Applications Classes of MM applications: Fundamental characteristics: 1) streaming stored audio • Typically delay and video sensitive. 2) streaming live audio and • End-to-end delay. • Delay jitter. video • But loss tolerant: 3) real-time interactive infrequent losses cause audio and video minor glitches. • Antithesis of data, which are loss Jitter -the variability intolerant but delay of packet delays within tolerant. the same packet stream Multimedia, Quality of Service: What is it? Multimedia applications: network audio and video (“continuous media”) QoS level of performance needed for application to function. Streaming Stored Multimedia • Streaming: • media stored at source • transmitted to client • streaming: client playout begins before all data has arrived • timing constraint for still-tobe transmitted data: in time for playout SSM: What Is It? 1. video recorded 2. video sent network delay 3. video received, played out at client streaming: at this time, client playing out early part of video, while server still sending later part of video 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 switch Customer’s House ATM or SONET Backbone network Local spooling server LDN-local distribution network LDN* 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 1889. 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: E-mail 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 e-mail 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 Bob Alice 167.180.112.24 INVITE bob @193.64.2 10.89 c=IN IP4 16 7.180.112.2 4 m=audio 38 060 RTP/A VP 0 193.64.210.89 port 5060 port 5060 Bob's terminal rings 200 OK .210.89 c=IN IP4 193.64 RTP/AVP 3 3 75 m=audio 48 ACK port 5060 port 38060 time • 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. m Law audio GSM • Alice’s SIP invite message indicates her port number & IP address. Indicates encoding that Alice prefers to receive port 48753 time •Default SIP port number is 5060. Example of SIP message INVITE sip:[email protected] SIP/2.0 Via: SIP/2.0/UDP 167.180.112.24 From: sip:[email protected] To: sip:[email protected] Call-ID: [email protected] Content-Type: application/sdp Content-Length: 885 c=IN IP4 167.180.112.24 m=audio 38060 RTP/AVP 0 Notes: r HTTP message syntax r sdp = session description protocol r Call-ID is unique for every call. More details • Here we don’t know Bob’s IP address. Intermediate SIP servers will be necessary. • Alice sends and receives SIP messages using the SIP default port number 506. • Alice specifies in Via: header that SIP client sends and receives SIP messages over UDP 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 H.323 - lications H.323 is applied in a variety of mechanisms Audio Audio Audio Video only and and and (IP telephony) video (video telephony) data and audio data. H.323 can also be applied to multipoint-multimedia communications. H.323 provides myriad services and, therefore, can be applied in a wide variety of areas— consumer, business, and entertainment application The features being added currently include fax-over-packet networks, gatekeeper-gatekeeper. Control Speech RTP RTCP H.225 (RAS) UDP Q.931 H.245(call control) TCP IP Data Link Protocol Physical Layer Protocol H.323 Packet Network The H.323 architectural Model for Internet Telephony Terminal GATEWAY TELEPHONE NETWORK INTERNET Gatekeeper ZONE Similarities b/w H.323 and SIP Allow two Party and multiparty calls Support parameter negotiation Support Encryption Support Media transport on RTP/RTCP protocols Feature sets are almost similar ITEM H.323 SIP Designed By ITU ITEF Compatibility with PSTN Yes Largely Compatibility with net No Yes Architecture Monolithic Modular Completeness Full Protocol Stack Handles only setup Message Format Binary ASCII Multimedia conferences Yes No Addressing Host or Telephone no URL Instant Messaging No Yes Implementation Large and complex Moderate Standards size 1400 pages 250 pages 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-tomultipoint (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. S1 R1 R4 H5 H4 S2 R2 R3 H3 S1 R1 R4 H5 H4 S2 R2 R3 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 Worldwide Statistics of multimedia market compiled by NASDAQ Movies Arcades Video CDs/Tapes Info servers Home video Cable networks Values in Billions TV/Radio Catalog Publishing Computers Telecom 0 20 40 60 80 100 Market Value in Billions 120 140 160 Growth of Multimedia Networks N E T W O R K s 2003 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: 1.www.cis.ohio-state.edu/~jain/ 2.www.google.com 3.University of colombia website. 4.IEEE papers on net B.Bharat Shetty 4th sem CS&E SJCE