TECNOLOGÍAS DE RED AVANZADAS – Master IC – 1- Protocolos de transporte con QoS  Clases de aplicaciones multimedia  Redes basadas en IP y QoS  Gestión de los recursos: IntServ vs DiffServ RSVP  RTP/RTCP: Transporte de flujos multimedia  RTSP: Control de sesión y localización de medios  Multicasting Thanks to : RADCOM technologies H. Shulzrinne Paul. E. Jones (from packetizer.com) Computer Networking: A Top Down Approach Featuring the Internet, 3 rd edition. Jim Kurose, Keith Ross Addison-Wesley, July 2004.

TECNOLOGÍAS DE RED AVANZADAS – Master IC What is multimedia?  Definition of multimedia Hard to find a clear-cut definition In general, multimedia is an integration of text, graphics, still and moving images, animation, sounds, and any other medium where every type of information can be represented, stored, transmitted and processed digitally  Characteristics of multimedia Digital – key concept Integration of multiple media type, usually including video or/and audio May be interactive or non-interactive 2

TECNOLOGÍAS DE RED AVANZADAS – Master IC Various Media Types  Text, Graphics, image, video, animation, sound, etc.  Classifications of various media types Captured vs. synthesized media Captured media (natural) : information captured from the real world –Example: still image, video, audio Synthesized media (artificial) : information synthesize by the computer –Example: text, graphics, animation Discrete vs. continuous media Discrete media: space-based, media involve the space dimension only –Text, Image, Graphics Continuous media: time-based, media involves both the space and the time dimension –Video, Sound, Animation 3

TECNOLOGÍAS DE RED AVANZADAS – Master IC Classification of Media Type 4 Sound Video Image Animation Text Graphics Captured From real world Synthesized By computer Discrete Continuous

TECNOLOGÍAS DE RED AVANZADAS – Master IC Text  Plain text Unformatted Characters coded in binary form ASCII code All characters have the same style and font  Rich text Formatted Contains format information besides codes for characters No predominant standards Characters of various size, shape and style, e.g. bold, colorful 5

TECNOLOGÍAS DE RED AVANZADAS – Master IC Plain Text vs. Rich Text 6 An example of Plain text Example of Rich text

TECNOLOGÍAS DE RED AVANZADAS – Master IC Graphics  Revisable document that retains structural information  Consists of objects such as lines, curves, circles, etc  Usually generated by graphic editor of computer programs 7 Example of graphics (FIG file)

TECNOLOGÍAS DE RED AVANZADAS – Master IC Images  2D matrix consisting of pixels Pixel—smallest element of resolution of the image One pixel is represented by a number of bits Pixel depth– the number of bits available to code the pixel  Have no structural information  Two categories: scanned vs. synthesized still image 8 Computer software Computer software Capture and A/D conversion Capture and A/D conversion Digital still image Synthesized image Scanned image Camera

TECNOLOGÍAS DE RED AVANZADAS – Master IC Images (cont.)  Examples of images Binary image – pixel depth 1 Gray-scale – pixel depth 8 Color image – pixel depth 24 9 Binary image Gray-scale imagecolor image

TECNOLOGÍAS DE RED AVANZADAS – Master IC Video vs. Animation  Both images and graphics can be displayed as a succession of view which create an impression of movement  Video – moving images or moving pictures Captured or Synthesized Consists of a series of bitmap images Each image is called a frame Frame rate: the speed to playback the video (frame per second)  Animation – moving graphics Generated by computer program (animation authoring tools) Consists of a set of objects The movements of the objects are calculated and the view is updated at playback 10

TECNOLOGÍAS DE RED AVANZADAS – Master IC Sound  1-D time-based signal  Speech vs. non-speech sound Speech – supports spoken language and has a semantic content Non-speech – does not convey semantics in general  Natural vs. structured sound Natural sound – Recorded/generated sound wave represented as digital signal Example: Audio in CD, WAV files Structured sound – Synthesize sound in a symbolic way Example: MIDI file 11

TECNOLOGÍAS DE RED AVANZADAS – Master IC Networked Multimedia  Local vs. networked multimedia Local: storage and presentation of multimedia information in standalone computers Sample applications: DVD Networked: involve transmission and distribution of multimedia information on the network Sample applications: videoconferencing, web video broadcasting, multimedia , etc. 12 Internet Video server Image server A scenario of multimedia networking

TECNOLOGÍAS DE RED AVANZADAS – Master IC Consideration of Networked Multimedia  Requirements of multimedia applications on the network Typically delay sensitive end-to-end delay delay jitter: –Jitter is the variability of packet delays within the same packet stream Quality requirement Satisfactory quality of media presentation Synchronization requirement Continuous requirement (no jerky video/audio) Can tolerant some degree of information loss 13

TECNOLOGÍAS DE RED AVANZADAS – Master IC Technologies of Multimedia Networking  Challenges of multimedia networking 1.Conflict between media size and bandwidth limit of the network 2.Conflict between the user requirement of multimedia application and the best-effort network 3.How to meet different requirements of different users?  Media compression – reduce the data volume Address the 1st challenge Image compression Video compression Audio compression  Multimedia transmission technology Address the 2nd and 3rd challenges Protocols for real-time transmission Rate / congestion control Error control 14

TECNOLOGÍAS DE RED AVANZADAS – Master IC Multimedia Networking Systems  Live media transmission system Capture, compress, and transmit the media on the fly (example?)  Send stored media across the network Media is pre-compressed and stored at the server. This system delivers the stored media to one or multiple receivers. (example?)  Differences between the two systems For live media delivery: Real-time media capture, need hardware support Real-time compression– speed is important Compression procedure can be adjusted based on network conditions For stored media delivery Offline compression – better compression result is important Compression can not be adjusted during transmission 15

TECNOLOGÍAS DE RED AVANZADAS – Master IC Classes of multimedia applications  Streaming stored audio and video  Streaming live audio and video  Real-time interactive audio and video 16

TECNOLOGÍAS DE RED AVANZADAS – Master IC Streaming Stored Multimedia: What is it? 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 t>0 100%

TECNOLOGÍAS DE RED AVANZADAS – Master IC Streaming vs. Download of Stored Multimedia Content 18  Download: Receive entire content before playback begins High “start-up” delay as media file can be large ~ 4GB for a 2 hour MPEG II movie  Streaming: Play the media file while it is being received Reasonable “start-up” delays Reception Rate >= playback rate. Why?

TECNOLOGÍAS DE RED AVANZADAS – Master IC Streaming Stored Multimedia: Interactivity 19 VCR-like functionality: client can pause, rewind, FF, push slider bar 10 sec initial delay OK 1-2 sec until command effect OK RTSP often used (more later) timing constraint for still-to-be transmitted data: in time for playout

TECNOLOGÍAS DE RED AVANZADAS – Master IC Streaming Multimedia: Client Buffering 20  Client-side buffering, playout delay compensate for network-added delay, delay jitter constant bit rate video transmission Cumulative data time variable network delay client video reception constant bit rate video playout at client client playout delay buffered video

TECNOLOGÍAS DE RED AVANZADAS – Master IC Streaming Multimedia: Client Buffering  Client-side buffering, playout delay compensate for network-added delay, delay jitter 21 buffered video variable fill rate, x(t) constant drain rate, d

TECNOLOGÍAS DE RED AVANZADAS – Master IC Interactive, Real-Time Multimedia applications: IP telephony, video conference, distributed interactive worlds  end-end delay requirements: audio: < 150 msec good, < 400 msec OK includes application-level (packetization) and network delays higher delays noticeable, impair interactivity  session initialization how does callee advertise its IP address, port number, encoding algorithms? 22

TECNOLOGÍAS DE RED AVANZADAS – Master IC Internet multimedia: simplest approach 23 audio, video not streamed:  no, “pipelining,” long delays until playout!  audio or video stored in file  files transferred as HTTP object received in entirety at client then passed to player

TECNOLOGÍAS DE RED AVANZADAS – Master IC Progressive Download 24  browser GETs metafile  browser launches player, passing metafile  player contacts server  server downloads audio/video to player

TECNOLOGÍAS DE RED AVANZADAS – Master IC Streaming from a streaming server  This architecture allows for non-HTTP protocol between server and media player  Can also use UDP instead of TCP. 25

TECNOLOGÍAS DE RED AVANZADAS – Master IC Multimedia Over Today’s Internet  TCP/UDP/IP: “best-effort service”  no guarantees on delay, loss  But multimedia apps requires QoS and level of performance to be effective!  Today’s Internet multimedia applications use application-level techniques to mitigate (as best possible) effects of delay, loss 26

TECNOLOGÍAS DE RED AVANZADAS – Master IC Streaming Multimedia: UDP or TCP? UDP  server sends at rate appropriate for client (oblivious to network congestion!) often send rate = encoding rate = constant rate then, fill rate = constant rate - packet loss  short playout delay (2-5 seconds) to compensate for network delay jitter  error recover: time permitting TCP  send at maximum possible rate under TCP  fill rate fluctuates due to TCP congestion control  larger playout delay: smooth TCP delivery rate  HTTP/TCP passes more easily through firewalls 27

TECNOLOGÍAS DE RED AVANZADAS – Master IC – 1- Protocolos de transporte con QoS.  Clases de aplicaciones multimedia  Redes basadas en IP y QoS  Gestión de los recursos: IntServ vs DiffServ RSVP  RTP/RTCP: Transporte de flujos multimedia  RTSP: Control de sesión y localización de medios  Multicasting Thanks to : RADCOM technologies H. Shulzrinne Paul. E. Jones (from packetizer.com)

TECNOLOGÍAS DE RED AVANZADAS – Master IC Requisitos de red.  Se definen 3 parámetros críticos que la red debería suministrar a las aplicaciones multimedia: Productividad (Throughput) Número de bits que la red es capaz de entregar por unidad de tiempo (tráfico soportado). CBR (streams de audio y vídeo sin comprimir) VBR (ídem comprimido) –Ráfagas (Peak Bit Rate y Mean Bit Rate) Retardo de tránsito (Transit delay) 29 Retardo extremo-a-extremo Retardo de acceso Retardo de tránsito Retardo de transmisión Mensaje listo para envío Envío del primer bit del mensaje Primer bit del mensaje recibido Ultimo bit del mensaje recibido Retardo de acceso Mensaje listo para recepción

TECNOLOGÍAS DE RED AVANZADAS – Master IC Requisitos de red (II). Varianza del retardo (Jitter) Define la variabilidad del retardo de una red. Jitter físico (redes de conmutación de circuito) –Suele ser muy pequeño ( ns ) LAN jitter (Ethernet, FDDI). –Jitter físico + tiempo de acceso al medio. Redes WAN de conmutación de paquete (IP, X.25, FR) –Jitter físico + tiempo de acceso + retardo de conmutación de paquete en conmutadores de la red D1D1 D 2 = D 1 D 3 > D 1 t t Emisor Receptor

TECNOLOGÍAS DE RED AVANZADAS – Master IC Internet y las aplicaciones multimedia  ¿Qué podemos añadir a IP para soportar los requerimientos de las aplicaciones multimedia? Técnicas de ecualización de retardos (buffering) Protocolos de transporte que se ajusten mejor a las necesidades de las aplicaciones multimedia: RTP (Real-Time Transport Protocol) RFC RTSP (Real-Time Streaming Protocol) RFC Técnicas de control de admisión y reserva de recursos (QoS) RSVP (Resource reSerVation Protocol) RFC 2205 Arquitecturas y protocolos específicos: Protocolos SIP (RFC 2543), SDP (RFC 2327), SAP (RFC 2974), etc.. ITU H

TECNOLOGÍAS DE RED AVANZADAS – Master IC Internet Protocols 32 Slide thanks to Henning Schulzrinne

TECNOLOGÍAS DE RED AVANZADAS – Master IC Multimedia, Quality of Service: What is it? 33 Multimedia applications: network audio and video (“continuous media”) network provides application with level of performance needed for application to function. QoS

TECNOLOGÍAS DE RED AVANZADAS – Master IC Improving QOS in IP Networks  Thus far: “making the best of best effort”  Future: next generation Internet with QoS guarantees RSVP: signaling for resource reservations Differentiated Services: differential guarantees Integrated Services: firm guarantees  simple model for sharing and congestion studies: 34

TECNOLOGÍAS DE RED AVANZADAS – Master IC Principles for QOS Guarantees  Example: 1Mbps IPphone, FTP share 1.5 Mbps link. bursts of FTP can congest router, cause audio loss want to give priority to audio over FTP 35 packet marking needed for router to distinguish between different classes; and new router policy to treat packets accordingly Principle 1

TECNOLOGÍAS DE RED AVANZADAS – Master IC Principles for QOS Guarantees (more)  what if applications misbehave (audio sends higher than declared rate) policing: force source adherence to bandwidth allocations  marking and policing at network edge: similar to ATM UNI (User Network Interface) 36 provide protection (isolation) for one class from others Principle 2

TECNOLOGÍAS DE RED AVANZADAS – Master IC Principles for QOS Guarantees (more)  Allocating fixed (non-sharable) bandwidth to flow: inefficient use of bandwidth if flows doesn’t use its allocation 37 While providing isolation, it is desirable to use resources as efficiently as possible Principle 3

TECNOLOGÍAS DE RED AVANZADAS – Master IC Principles for QOS Guarantees (more)  Basic fact of life: can not support traffic demands beyond link capacity 38 Call Admission: flow declares its needs, network may block call (e.g., busy signal) if it cannot meet needs Principle 4

TECNOLOGÍAS DE RED AVANZADAS – Master IC – 1- Protocolos de transporte con QoS.  Clases de aplicaciones multimedia  Redes basadas en IP y QoS  Gestión de los recursos: IntServ vs DiffServ RSVP  RTP/RTCP: Transporte de flujos multimedia  RTSP: Control de sesión y localización de medios  Multicasting Thanks to : RADCOM technologies H. Shulzrinne Paul. E. Jones (from packetizer.com)

TECNOLOGÍAS DE RED AVANZADAS – Master IC Scheduling And Policing Mechanisms  scheduling: choose next packet to send on link  FIFO (first in first out) scheduling: send in order of arrival to queue discard policy: if packet arrives to full queue: who to discard? Tail drop: drop arriving packet priority: drop/remove on priority basis random: drop/remove randomly 40

TECNOLOGÍAS DE RED AVANZADAS – Master IC Scheduling Policies: more Priority scheduling: transmit highest priority queued packet  multiple classes, with different priorities class may depend on marking or other header info, e.g. IP source/dest, port numbers, etc.. 41

TECNOLOGÍAS DE RED AVANZADAS – Master IC Scheduling Policies: still more round robin scheduling:  multiple classes  cyclically scan class queues, serving one from each class (if available) 42

TECNOLOGÍAS DE RED AVANZADAS – Master IC Scheduling Policies: still more Weighted Fair Queuing:  generalized Round Robin  each class gets weighted amount of service in each cycle 43

TECNOLOGÍAS DE RED AVANZADAS – Master IC Policing Mechanisms  Goal: limit traffic to not exceed declared parameters  Three common-used criteria: (Long term) Average Rate: how many pkts can be sent per unit time (in the long run) crucial question: what is the interval length: 100 packets per sec or 6000 packets per min have same average! Peak Rate: e.g., 6000 pkts per min. (ppm) avg.; 1500 pps peak rate (Max.) Burst Size: max. number of pkts sent consecutively (with no intervening idle) 44

TECNOLOGÍAS DE RED AVANZADAS – Master IC Policing Mechanisms Token Bucket: limit input to specified Burst Size and Average Rate.  bucket can hold b tokens  tokens generated at rate r token/sec unless bucket full  over interval of length t: number of packets admitted less than or equal to (r t + b). 45

TECNOLOGÍAS DE RED AVANZADAS – Master IC Policing Mechanisms (more)  token bucket, WFQ combine to provide guaranteed upper bound on delay, i.e., QoS guarantee! 46 WFQ token rate, r bucket size, b per-flow rate, R D = b/R max arriving traffic

TECNOLOGÍAS DE RED AVANZADAS – Master IC IETF Integrated Services  architecture for providing QOS guarantees in IP networks for individual application sessions  resource reservation: routers maintain state info of allocated resources, QoS req’s  admit/deny new call setup requests: 47 Question: can newly arriving flow be admitted with performance guarantees while not violated QoS guarantees made to already admitted flows?

TECNOLOGÍAS DE RED AVANZADAS – Master IC Intserv: QoS guarantee scenario 48  Resource reservation call setup, signaling (RSVP) traffic, QoS declaration per-element admission control QoS-sensitive scheduling (e.g., WFQ) request/ reply

TECNOLOGÍAS DE RED AVANZADAS – Master IC Call Admission Arriving session must :  declare its QOS requirement R-spec: defines the QOS being requested  characterize traffic it will send into network T-spec: defines traffic characteristics  signaling protocol: needed to carry R-spec and T-spec to routers (where reservation is required) RSVP 49

TECNOLOGÍAS DE RED AVANZADAS – Master IC Intserv QoS: Service models [RFC2211, RFC2212] 50 Guaranteed service:  worst case traffic arrival: leaky-bucket- policed source  simple (mathematically provable) bound on delay [Parekh 1992, Cruz 1988] Controlled load service:  "a quality of service closely approximating the QoS that same flow would receive from an unloaded network element." WFQ token rate, r bucket size, b per-flow rate, R D = b/R max arriving traffic

TECNOLOGÍAS DE RED AVANZADAS – Master IC IETF Differentiated Services Concerns with Intserv:  Scalability: signaling, maintaining per-flow router state difficult with large number of flows  Flexible Service Models: Intserv has only two classes. Also want “qualitative” service classes “behaves like a wire” relative service distinction: Platinum, Gold, Silver Diffserv approach:  simple functions in network core, relatively complex functions at edge routers (or hosts)  Don’t define service classes, provide functional components to build service classes 51

TECNOLOGÍAS DE RED AVANZADAS – Master IC Diffserv Architecture 52 Edge router:  per-flow traffic management  marks packets as in-profile and out-profile Core router:  per class traffic management  buffering and scheduling based on marking at edge  preference given to in-profile packets  Assured Forwarding scheduling... r b marking

TECNOLOGÍAS DE RED AVANZADAS – Master IC Edge-router Packet Marking  class-based marking: packets of different classes marked differently  intra-class marking: conforming portion of flow marked differently than non- conforming one  profile: pre-negotiated rate A, bucket size B  packet marking at edge based on per-flow profile Possible usage of marking: User packets Rate A B

TECNOLOGÍAS DE RED AVANZADAS – Master IC Classification and Conditioning  Packet is marked in the Type of Service (TOS) in IPv4, and Traffic Class in IPv6  6 bits used for Differentiated Service Code Point (DSCP) and determine PHB that the packet will receive  2 bits are currently unused 54

TECNOLOGÍAS DE RED AVANZADAS – Master IC Classification and Conditioning may be desirable to limit traffic injection rate of some class:  user declares traffic profile (e.g., rate, burst size)  traffic metered, shaped if non-conforming 55

TECNOLOGÍAS DE RED AVANZADAS – Master IC Forwarding (PHB)  PHB result in a different observable (measurable) forwarding performance behavior  PHB does not specify what mechanisms to use to ensure required PHB performance behavior  Examples: Class A gets x% of outgoing link bandwidth over time intervals of a specified length Class A packets leave first before packets from class B 56

TECNOLOGÍAS DE RED AVANZADAS – Master IC Forwarding (PHB) PHBs being developed:  Expedited Forwarding: pkt departure rate of a class equals or exceeds specified rate logical link with a minimum guaranteed rate  Assured Forwarding: 4 classes of traffic each guaranteed minimum amount of bandwidth each with three drop preference partitions 57

TECNOLOGÍAS DE RED AVANZADAS – Master IC – 1- Protocolos de transporte multimedia.  Clases de aplicaciones multimedia  Redes basadas en IP y QoS  Gestión de los recursos: IntServ vs DiffServ RSVP  RTP/RTCP: Transporte de flujos multimedia  RTSP: Control de sesión y localización de medios  Multicasting

TECNOLOGÍAS DE RED AVANZADAS – Master IC Signaling in the Internet  New requirement: reserve resources along end-to-end path (end system, routers) for QoS for multimedia applications  RSVP: Resource Reservation Protocol [RFC 2205] “ … allow users to communicate requirements to network in robust and efficient way.” i.e., signaling !  earlier Internet Signaling protocol: ST-II [RFC 1819] 59 connectionless (stateless) forwarding by IP routers best effort service no network signaling protocols in initial IP design + =

TECNOLOGÍAS DE RED AVANZADAS – Master IC RSVP Design Goals 1.accommodate heterogeneous receivers (different bandwidth along paths) 2.accommodate different applications with different resource requirements 3.make multicast a first class service, with adaptation to multicast group membership 4.leverage existing multicast/unicast routing, with adaptation to changes in underlying unicast, multicast routes 5.control protocol overhead to grow (at worst) linear in # receivers 6.modular design for heterogeneous underlying technologies 60

TECNOLOGÍAS DE RED AVANZADAS – Master IC RSVP: does not…  specify how resources are to be reserved rather: a mechanism for communicating needs  determine routes packets will take that’s the job of routing protocols signaling decoupled from routing  interact with forwarding of packets separation of control (signaling) and data (forwarding) planes 61

TECNOLOGÍAS DE RED AVANZADAS – Master IC RSVP: overview of operation  senders, receiver join a multicast group done outside of RSVP senders need not join group  sender-to-network signaling path message: make sender presence known to routers path teardown: delete sender’s path state from routers  receiver-to-network signaling reservation message: reserve resources from sender(s) to receiver reservation teardown: remove receiver reservations  network-to-end-system signaling path error reservation error 62

TECNOLOGÍAS DE RED AVANZADAS – Master IC Call Admission  Session must first declare its QOS requirement and characterize the traffic it will send through the network  R-spec: defines the QOS being requested  T-spec: defines the traffic characteristics  A signaling protocol is needed to carry the R-spec and T- spec to the routers where reservation is required;  RSVP is a leading candidate for such signaling protocol 63

TECNOLOGÍAS DE RED AVANZADAS – Master IC RSVP request (T-Spec)  A token bucket specification bucket size, b token rate, r the packet is transmitted onward only if the number of tokens in the bucket is at least as large as the packet  peak rate, p p > r  maximum packet size, M  minimum policed unit, m All packets less than m bytes are considered to be m bytes Reduces the overhead to process each packet Bound the bandwidth overhead of link-level headers 64

TECNOLOGÍAS DE RED AVANZADAS – Master IC Call Admission  Call Admission: routers will admit calls based on their R- spec and T-spec and base on the current resource allocated at the routers to other calls. 65

TECNOLOGÍAS DE RED AVANZADAS – Master IC Integrated Services: Classes  Guaranteed QOS: this class is provided with firm bounds on queuing delay at a router; envisioned for hard real-time applications that are highly sensitive to end-to-end delay expectation and variance  Controlled Load: this class is provided a QOS closely approximating that provided by an unloaded router; envisioned for today’s IP network real-time applications which perform well in an unloaded network 66

TECNOLOGÍAS DE RED AVANZADAS – Master IC R-spec  An indication of the QoS control service requested Controlled-load service and Guaranteed service  For Controlled-load service Simply a Tspec  For Guaranteed service A Rate (R) term, the bandwidth required R  r, extra bandwidth will reduce queuing delays A Slack (S) term The difference between the desired delay and the delay that would be achieved if rate R were used With a zero slack term, each router along the path must reserve R bandwidth A nonzero slack term offers the individual routers greater flexibility in making their local reservation Number decreased by routers on the path. 67

TECNOLOGÍAS DE RED AVANZADAS – Master IC QoS Routing: Multiple constraints  A request specifies the desired QoS requirements e.g., BW, Delay, Jitter, packet loss, path reliability etc  Two type of constraints: Additive: e.g., delay Maximum (or Minimum): e.g., Bandwidth  Task Find a (min cost) path which satisfies the constraints if no feasible path found, reject the connection 68

TECNOLOGÍAS DE RED AVANZADAS – Master IC Path msgs: RSVP sender-to-network signaling  path message contents: address: unicast destination, or multicast group flowspec: bandwidth requirements spec. filter flag: if yes, record identities of upstream senders (to allow packets filtering by source) previous hop: upstream router/host ID refresh time: time until this info times out  path message: communicates sender info, and reverse- path-to-sender routing info later upstream forwarding of receiver reservations 69

TECNOLOGÍAS DE RED AVANZADAS – Master IC RSVP: simple audio conference  H1, H2, H3, H4, H5 both senders and receivers  multicast group m1  no filtering: packets from any sender forwarded  audio rate: b  only one multicast routing tree possible 70 H2 H5 H3 H4 H1 R1 R2R3

TECNOLOGÍAS DE RED AVANZADAS – Master IC RSVP: building up path state  H1, …, H5 all send path messages on m1: (address=m1, Tspec=b, filter-spec=no-filter,refresh=100)  Suppose H1 sends first path message 71 in out in out in out H2 H5 H3 H4 H1 R1 R2R3 L1 L2 L3 L4 L5 L6 L7 L5 L7 L6 L1 L2 L6L3 L7 L4 m1:

TECNOLOGÍAS DE RED AVANZADAS – Master IC RSVP: building up path state  next, H5 sends path message, creating more state in routers 72 in out in out in out H2 H5 H3 H4 H1 R1 R2R3 L1 L2 L3 L4 L5 L6 L7 L5 L7 L6 L1 L2 L6L3 L7 L4 L5 L6 L1 L6 m1:

TECNOLOGÍAS DE RED AVANZADAS – Master IC RSVP: building up path state  H2, H3, H5 send path msgs, completing path state tables 73 in out in out in out H2 H5 H3 H4 H1 R1 R2R3 L1 L2 L3 L4 L5 L6 L7 L5 L7 L6 L1 L2 L6L3 L7 L4 L5 L6 L1 L6 L7 L4 L3 L7 L2 m1:

TECNOLOGÍAS DE RED AVANZADAS – Master IC reservation msgs: receiver-to-network signaling  reservation message contents: desired bandwidth: filter type: no filter: any packets address to multicast group can use reservation fixed filter: only packets from specific set of senders can use reservation dynamic filter: senders who’s packets can be forwarded across link will change (by receiver choice) over time. filter spec  reservations flow upstream from receiver-to-senders, reserving resources, creating additional, receiver-related state at routers 74

TECNOLOGÍAS DE RED AVANZADAS – Master IC RSVP: receiver reservation example 1 H1 wants to receive audio from all other senders  H1 reservation msg flows uptree to sources  H1 only reserves enough bandwidth for 1 audio stream  reservation is of type “no filter” – any sender can use reserved bandwidth 75 H2 H5 H3 H4 H1 R1 R2R3 L1 L2 L3 L4 L5 L6 L7

TECNOLOGÍAS DE RED AVANZADAS – Master IC RSVP: receiver reservation example 1  H1 reservation msgs flows uptree to sources  routers, hosts reserve bandwidth b needed on downstream links towards H1 76 in out H2 H5 H3 H4 H1 R1 R2R3 L1 L2 L3 L4 L5 L6 L7 L1 L2 L6 L1 (b)(b) in out L5 L6 L7 L5 (b)(b) L6 in out L3 L4 L7 L3 (b)(b) L4 L2 b b b b b b b m1:

TECNOLOGÍAS DE RED AVANZADAS – Master IC RSVP: receiver reservation example 1 (more) 77  next, H2 makes no-filter reservation for bandwidth b  H2 forwards to R1, R1 forwards to H1 and R2 (?)  R2 takes no action, since b already reserved on L6 in out H2 H5 H3 H4 H1 R1 R2R3 L1 L2 L3 L4 L5 L6 L7 L1 L2 L6 L1 (b)(b) in out L5 L6 L7 L5 (b)(b) L6 in out L3 L4 L7 L3 (b)(b) L4 L2 b b b b b b b b b (b)(b) m1:

TECNOLOGÍAS DE RED AVANZADAS – Master IC RSVP: receiver reservation: issues 78 What if multiple senders (e.g., H3, H4, H5) over link (e.g., L6)?  arbitrary interleaving of packets  L6 flow policed by leaky bucket: if H3+H4+H5 sending rate exceeds b, packet loss will occur in out H2 H5 H3 H4 H1 R1 R2R3 L1 L2 L3 L4 L5 L6 L7 L1 L2 L6 L1 (b)(b) in out L5 L6 L7 L5 (b)(b) L6 in out L3 L4 L7 L3 (b)(b) L4 L2 b b b b b b b b b (b)(b) m1:

TECNOLOGÍAS DE RED AVANZADAS – Master IC RSVP: example 2  H1, H4 are only senders send path messages as before, indicating filtered reservation Routers store upstream senders for each upstream link  H2 will want to receive from H4 (only) 79 H2 H3 H4 H1 R1 R2R3 L1 L2 L3 L4 L6 L7 H2 H3 L2 L3

TECNOLOGÍAS DE RED AVANZADAS – Master IC RSVP: example 2  H1, H4 are only senders send path messages as before, indicating filtered reservation 80 H2 H3 H4 H1 R1 R3 L1 L2 L3 L4 L6 L7 H2 H3 L2 L3 L2(H1-via-H1 ; H4-via-R2 ) L6(H1-via-H1 ) L1(H4-via-R2 ) in out L6(H4-via-R3 ) L7(H1-via-R1 ) in out L1, L6 L6, L7 L3(H4-via-H4 ; H1-via-R3 ) L4(H1-via-R2 ) L7(H4-via-H4 ) in out L4, L7 R2

TECNOLOGÍAS DE RED AVANZADAS – Master IC RSVP: example 2  receiver H2 sends reservation message for source H4 at bandwidth b propagated upstream towards H4, reserving b 81 H2 H3 H4 H1 R1 R3 L1 L2 L3 L4 L6 L7 H2 H3 L2 L3 L2(H1-via-H1 ;H4-via-R2 ) L6(H1-via-H1 ) L1(H4-via-R2 ) in out L6(H4-via-R3 ) L7(H1-via-R1 ) in out L1, L6 L6, L7 L3(H4-via-H4 ; H1-via-R2 ) L4(H1-via-R2 ) L7(H4-via-H4 ) in out L4, L7 R2 (b) L1 b b b b

TECNOLOGÍAS DE RED AVANZADAS – Master IC RSVP: soft-state 82  senders periodically resend path msgs to refresh (maintain) state  receivers periodically resend resv msgs to refresh (maintain) state  path and resv msgs have TTL field, specifying refresh interval H2 H3 H4 H1 R1 R3 L1 L2 L3 L4 L6 L7 H2 H3 L2 L3 L2(H1-via-H1 ;H4-via-R2 ) L6(H1-via-H1 ) L1(H4-via-R2 ) in out L6(H4-via-R3 ) L7(H1-via-R1 ) in out L1, L6 L6, L7 L3(H4-via-H4 ; H1-via-R3 ) L4(H1-via-R2 ) L7(H4-via-H4 ) in out L4, L7 R2 (b) L1 b b b b

TECNOLOGÍAS DE RED AVANZADAS – Master IC RSVP: soft-state 83  suppose H4 (sender) leaves without performing teardown H2 H3 H4 H1 R1 R3 L1 L2 L3 L4 L6 L7 H2 H3 L2 L3 L2(H1-via-H1 ;H4-via-R2 ) L6(H1-via-H1 ) L1(H4-via-R2 ) in out L6(H4-via-R3 ) L7(H1-via-R1 ) in out L1, L6 L6, L7 L3(H4-via-H4 ; H1-via-R3 ) L4(H1-via-R2 ) L7(H4-via-H4 ) in out L4, L7 R2 (b) L1 b b b b  eventually state in routers will timeout and disappear! gone fishing!

TECNOLOGÍAS DE RED AVANZADAS – Master IC – 1- Protocolos de transporte multimedia.  Clases de aplicaciones multimedia  Redes basadas en IP y QoS  Gestión de los recursos: IntServ vs DiffServ RSVP  RTP/RTCP: Transporte de flujos multimedia  RTSP: Control de sesión y localización de medios  Multicasting

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTP (Real-time Transport Protocol)  Se basa en el concepto de sesión: la asociación entre un conjunto de aplicaciones que se comunican usando RTP  Una sesión es identificada por: Una dirección IP multicast Dos puertos: Uno para los datos y otro para control (RTCP)  Un participante (participant) puede ser una máquina o un usuario que participa en una sesión  Cada media distinto es trasmitido usando una sesión diferente. Por ejemplo, si se quisiera transmitir audio y vídeo harían falta dos sesiones separadas  Esto permite a un participante solamente ver o solamente oír 85

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTP (Real-time Transport Protocol)  Audio-conferencia con multicast y RTP Sesión de audio: Una dirección multicast y dos puertos Datos de audio y mensajes de control RTCP. Existirá (al menos) una fuente de audio que enviará un stream de segmentos de audio pequeños (20 ms) utilizando UDP. A cada segmento se le asigna una cabecera RTP La cabecera RTP indica el tipo de codificación (PCM, ADPCM, LPC, etc.) Número de secuencia y fechado de los datos. Control de conferencia (RTCP): Número e identificación de participantes en un instante dado. Información acerca de cómo se recibe el audio.  Audio y Vídeo conferencia con multicast y RTP Si se utilizan los dos medios, se debe crear una sesión RTP independiente para cada uno de ellos. Una dirección multicast y 2 puertos por cada sesión. Existencia de participantes que reciban sólo uno de los medios. Temporización independiente de audio y vídeo. 86

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTP: Mezcladores y traductores  Mezcladores (Mixers). Permiten que canales con un BW bajo puedan participar en una conferencia. El mixer re-sincroniza los paquetes y hace todas las conversiones necesarias para cada tipo de canal.  Traductores (Translators). Permiten conectar sitios que no tienen acceso multicast (p.ej. que están en una sub-red protegida por un firewall) 87

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTP: Formato de mensaje (I) 88 V: versión; actualmente es la 2 P: si está a 1 el paquete tiene bytes de relleno (padding) X: presencia de una extensión de la cabecera VPCCX M PTSequence number Timestamp Synchronization Source (SSRC) ID Contributing Source (CSRC) ID 32 bits

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTP: Formato de mensaje (II) 89 CC: Identifica el número de CSRC que contribuyen a los datos M: Marca (definida según el perfil) PT: Tipo de datos (según perfil) VPCCX M PTSequence number Timestamp Synchronization Source (SSRC) ID Contributing Source (CSRC) ID 32 bits

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTP: Formato de mensaje (III) 90 Sequence number: Establece el orden de los paquetes Timestamp: Instante de captura del primer octeto del campo de datos SSRC: Identifica la fuente de sincronización CSRC: Fuentes que contribuyen VPCCX M PTSequence number Timestamp Synchronization Source (SSRC) ID Contributing Source (CSRC) ID 32 bits

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTP header definition 91 /* * RTP data header */ typedef struct { unsigned int version:2; unsigned int p:1; unsigned int x:1; unsigned int cc:4; unsigned int m:1; unsigned int pt:7; u_int16 seq; u_int32 ts; u_int32 ssrc; u_int32 csrc[1]; } rtp_hdr_t; /* * RTP data header */ typedef struct { unsigned int version:2; unsigned int p:1; unsigned int x:1; unsigned int cc:4; unsigned int m:1; unsigned int pt:7; u_int16 seq; u_int32 ts; u_int32 ssrc; u_int32 csrc[1]; } rtp_hdr_t;

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTP y las aplicaciones  La especificación de RTP para una aplicación particular va acompañada de: Un perfil (profile) que defina un conjunto de códigos para los tipos de datos transportados (payload) El formato de transporte de cada uno de los tipos de datos previstos Ej.: RFC 1890 para audio y vídeo 92 PT encoding audio/video clock rate channels name (A/V) (Hz) (audio) ______________________________________________ 0 PCMU A A G721 A GSM A unassigned ? reserved N/A N/A N/A unassigned ? dynamic ? PT encoding audio/video clock rate channels name (A/V) (Hz) (audio) ______________________________________________ 0 PCMU A A G721 A GSM A unassigned ? reserved N/A N/A N/A unassigned ? dynamic ? PCMU Corresponde a la recomendación CCITT/ITU-T G.711. El audio se codifica con 8 bits por muestra, después de una cuantificación logarítmica. PCMU es la codificación que se utiliza en Internet para un media de tipo audio/basic. PCMU Corresponde a la recomendación CCITT/ITU-T G.711. El audio se codifica con 8 bits por muestra, después de una cuantificación logarítmica. PCMU es la codificación que se utiliza en Internet para un media de tipo audio/basic.

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTCP (RTP Control Protocol)  RTCP se basa en envíos periódicos de paquetes de control a los participantes de una sesión RTP Permite realizar una realimentación de la calidad de recepción de los datos (estadísticas). Los paquetes de control siempre llevan la identificación de la fuente RTP: CNAME Asociar más de una sesión a un mismo fuente (sincronización). El envío de estos paquetes debe ser controlado por cada participante (sistema ampliable). Control de sesión (opcional) Información adicional de cada participante. Entrada y salida de participantes en las sesión. Negociación de parámetros y formatos. 93

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTCP (RTP Control Protocol)  RTCP permite controlar el trafico que no se auto-limita (p.ej cuando el número de fuentes aumenta)  Para ello se define el ancho de banda de la sesión. RTCP se reserva el 5% (bwRTCP) A cada fuente se le asigna 1/4 de bwRTCP El intervalo entre cada paquete RTCP es > 5 sec 94

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTCP (RTP Control Protocol)  Formato de un paquete RTCP: Existen distintos tipos de paquetes RTCP: SR (Sender Report): Informes estadísticos de transmisión y recepción de los elementos activos en la sesión. RR (Receiver Report): Informes estadísticos de recepción en los receptores. SDES (Source Description): Información del participante (CNAME, , etc). BYE: Salida de la sesión. APP: Mensajes específicos de la aplicación. Cada paquete RTCP tiene su propio formato. Su tamaño debe ser múltiplo de 32 bits (padding). Se pueden concatenar varios paquetes RTCP en uno (compound RTCP packet). 95

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTCP: Mensajes SR 96 VP RC PT=SR=200 Longitud SSRC del sender 32 bits NTP timestamp msw NTP timestamp lsw RTP timestamp Contador de los paquetes del sender Contador de los bytes del sender SSRC_1 Frac perd Total paquetes perdidos Num sec más alto recibido Jitter de inter-llegada Retraso del último SR (LSR) Ultimo SR (LSR) Report block 1 Sender info cabecera

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTCP: Cálculo del Jitter  Es una estimación de la variancia del tiempo de inter- llegada de los paquetes RTP S i  RTP timestamp del paquete i R i  Instante de llegada del paquete i 97

TECNOLOGÍAS DE RED AVANZADAS – Master IC – 1- Protocolos de transporte multimedia.  Clases de aplicaciones multimedia  Redes basadas en IP y QoS  Gestión de los recursos: IntServ vs DiffServ RSVP  RTP/RTCP: Transporte de flujos multimedia  RTSP: Control de sesión y localización de medios  Multicasting

TECNOLOGÍAS DE RED AVANZADAS – Master IC Real-Time Streaming Protocol RFC 2326  Tiene la función de un “mando a distancia por la red” para servidores multimedia  Permite establecer y controlar uno o más flujos de datos sincronizados  NO existe el concepto de conexión RTSP sino de sesión RTSP  Además, una sesión RTSP no tiene relación con ninguna conexión especifica de nivel transporte (p.ej. TCP o UDP)  Los flujos de datos no tienen por que utilizar RTP  Está basado en HTTP/1.1 Diferencias importantes: No es stateless Los clientes y servidores pueden generar peticiones 99

TECNOLOGÍAS DE RED AVANZADAS – Master IC Terminología RTSP  Conferencia  Media stream Una instancia única de un medio continuo: Un stream audio, Un stream vídeo Una “whiteboard”  Presentación: Es el conjunto de uno o más streams, que son vistos por el usuario como un conjunto integrado Voz del público Imagen del conferenciante Imagen del público Imagen de las transparencias Voz del conferenciante

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTSP: Ejemplo de una sesión Web server SETUP PLAY PAUSE TEARDOWN HTTP GET descripción de la sesión RTP audio RTP vídeo RTCP Cliente Media server

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTSP: Comandos de petición Request = Request-Line ; *(general-header | request-header | entity-header ) CRLF [ message-body ] Request-Line = Method SP Request-URI SP RTSP-Version CRLF Method = "DESCRIBE“ | "ANNOUNCE" | "GET_PARAMETER" | "OPTIONS“ | "PAUSE" | "PLAY" | "RECORD" | "REDIRECT" | "SETUP" | "SET_PARAMETER" | "TEARDOWN" | extension-method extension-method = token Request-URI = "*" | absolute_URI RTSP-Version = "RTSP" "/" 1*DIGIT "." 1*DIGIT

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTSP: Mensajes de respuesta Response = Status-Line ; *(general-header |response-header |entity-header ) CRLF [ message-body ] Status-Line = RTSP-version SP Status-Code SP Reason-Phrase CRLF Status-Code = 1xx: Información (Comando recibido, procesando,..) | 2xx: Exito (Comando recibido y ejecutado con éxito) | 3xx: Re-dirección (Comando recibido pero aún no completado) | 4xx: Error del cliente (El comando tiene errores de sintaxis) | 5xx: Error del servidor (Error interno del servidor)

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTSP: Una sesión completa (I) C->W: GET /twister.sdp HTTP/1.1 Host: Accept: application/sdp W->C: HTTP/ OK Content-Type: application/sdp v=0 o= IN IP s=RTSP Session m=audio 0 RTP/AVP 0 a=control:rtsp://audio.example.com/twister/audio.en m=video 0 RTP/AVP 31 a=control:rtsp://video.example.com/twister/video C->W: GET /twister.sdp HTTP/1.1 Host: Accept: application/sdp W->C: HTTP/ OK Content-Type: application/sdp v=0 o= IN IP s=RTSP Session m=audio 0 RTP/AVP 0 a=control:rtsp://audio.example.com/twister/audio.en m=video 0 RTP/AVP 31 a=control:rtsp://video.example.com/twister/video web server W cliente C media server A media server V

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTSP: Una sesión completa (II) C->A: SETUP rtsp://audio.example.com/twister/audio.en RTSP/1.0 CSeq: 1 Transport: RTP/AVP/UDP;unicast;client_port= A->C: RTSP/ OK CSeq: 1 Session: Transport: RTP/AVP/UDP;unicast;client_port= ; server_port= C->V: SETUP rtsp://video.example.com/twister/video RTSP/1.0 CSeq: 1 Transport: RTP/AVP/UDP;unicast;client_port= V->C: RTSP/ OK CSeq: 1 Session: Transport: RTP/AVP/UDP;unicast;client_port= ; server_port= C->A: SETUP rtsp://audio.example.com/twister/audio.en RTSP/1.0 CSeq: 1 Transport: RTP/AVP/UDP;unicast;client_port= A->C: RTSP/ OK CSeq: 1 Session: Transport: RTP/AVP/UDP;unicast;client_port= ; server_port= C->V: SETUP rtsp://video.example.com/twister/video RTSP/1.0 CSeq: 1 Transport: RTP/AVP/UDP;unicast;client_port= V->C: RTSP/ OK CSeq: 1 Session: Transport: RTP/AVP/UDP;unicast;client_port= ; server_port=

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTSP: Una sesión completa (III) C->V: PLAY rtsp://video.example.com/twister/video RTSP/1.0 CSeq: 2 Session: Range: smpte=0:10:00- V->C: RTSP/ OK CSeq: 2 Session: Range: smpte=0:10:00-0:20:00 RTP-Info: url=rtsp://video.example.com/twister/video; seq= ;rtptime= C->A: PLAY rtsp://audio.example.com/twister/audio.en RTSP/1.0 CSeq: 2 Session: Range: smpte=0:10:00- A->C: RTSP/ OK CSeq: 2 Session: Range: smpte=0:10:00-0:20:00 RTP-Info: url=rtsp://audio.example.com/twister/audio.en; seq=876655;rtptime= C->V: PLAY rtsp://video.example.com/twister/video RTSP/1.0 CSeq: 2 Session: Range: smpte=0:10:00- V->C: RTSP/ OK CSeq: 2 Session: Range: smpte=0:10:00-0:20:00 RTP-Info: url=rtsp://video.example.com/twister/video; seq= ;rtptime= C->A: PLAY rtsp://audio.example.com/twister/audio.en RTSP/1.0 CSeq: 2 Session: Range: smpte=0:10:00- A->C: RTSP/ OK CSeq: 2 Session: Range: smpte=0:10:00-0:20:00 RTP-Info: url=rtsp://audio.example.com/twister/audio.en; seq=876655;rtptime=

TECNOLOGÍAS DE RED AVANZADAS – Master IC RTSP: Una sesión completa (IV) C->A: TEARDOWN rtsp://audio.example.com/twister/audio.en RTSP/1.0 CSeq: 3 Session: A->C: RTSP/ OK CSeq: 3 C->V: TEARDOWN rtsp://video.example.com/twister/video RTSP/1.0 CSeq: 3 Session: V->C: RTSP/ OK CSeq: 3 C->A: TEARDOWN rtsp://audio.example.com/twister/audio.en RTSP/1.0 CSeq: 3 Session: A->C: RTSP/ OK CSeq: 3 C->V: TEARDOWN rtsp://video.example.com/twister/video RTSP/1.0 CSeq: 3 Session: V->C: RTSP/ OK CSeq: 3

TECNOLOGÍAS DE RED AVANZADAS – Master IC – 1- Protocolos de transporte multimedia.  Clases de aplicaciones multimedia  Redes basadas en IP y QoS  Gestión de los recursos: IntServ vs DiffServ RSVP  RTP/RTCP: Transporte de flujos multimedia  RTSP: Control de sesión y localización de medios  Multicasting

TECNOLOGÍAS DE RED AVANZADAS – Master IC Multicast = Efficient Data Distribution Src

TECNOLOGÍAS DE RED AVANZADAS – Master IC Why Multicast ?  Need for efficient one-to-many delivery of same data  Applications: News/sports/stock/weather updates Distance learning Configuration, routing updates, service location Pointcast-type “push” apps Teleconferencing (audio, video, shared whiteboard, text editor) Distributed interactive gaming or simulations distribution lists Content distribution; Software distribution Web-cache updates Database replication

TECNOLOGÍAS DE RED AVANZADAS – Master IC Why Not Broadcast or Unicast?  Broadcast: Send a copy to every machine on the net Simple, but inefficient All nodes must process packet even if they don’t care Wastes more CPU cycles of slower machines (“broadcast radiation”) Network loops lead to “broadcast storms”  Replicated Unicast: Sender sends a copy to each receiver in turn Receivers need to register or sender must be pre-configured Sender is focal point of all control traffic Reliability => per-receiver state, separate sessions/processes at sender

TECNOLOGÍAS DE RED AVANZADAS – Master IC Multicast Apps Characteristics  Number of (simultaneous) senders to the group  The size of the groups Number of members (receivers) Geographic extent or scope Diameter of the group measured in router hops  The longevity of the group  Number of aggregate packets/second  The peak/average used by source  Level of human interactivity Lecture mode vs interactive Data-only (eg database replication) vs multimedia

TECNOLOGÍAS DE RED AVANZADAS – Master IC Reliable Multicast vs. Unreliable Multicast  When a multicast message is sent by a process, the runtime support of the multicast mechanism is responsible for delivering the message to each process currently in the multicast group.  As each participating process may be on a separate host, due to factors such as failures of network links and/or network hosts, routing delays, and differences in software and hardware, the time between when a message is sent and when it is received may vary among the recipient processes.  Moreover, a message may not be received by one or more of the processes at all

TECNOLOGÍAS DE RED AVANZADAS – Master IC Classification of multicasting mechanisms in terms of message delivery  Unreliable multicast: The arrival of the correct message at each process is not guaranteed.  Reliable multicast: Guarantees that each message is eventually delivered in a non- corrupted form to each process in the group.  The definition of reliable multicast requires that each participating process receives exactly one copy of each message sent. It does not put any restriction of the order the messages delivered.  Reliable multicast can be further classified based on the order of the delivery of the messages: unordered, FIFO, causal order, atomic order

TECNOLOGÍAS DE RED AVANZADAS – Master IC Classification of reliable multicast -- unordered  An unordered reliable multicast system guarantees the safe delivery of each message, but it provides no guarantee on the delivery order of the messages.  Example: Processes P1, P2, and P3 have formed a multicast group. Three messages, m1, m2, m3 have been sent to the group. An unordered reliable multicast system may deliver the messages to each of the three processes in any of these: m1-m2-m3, m1-m3-m2, m2-m1-m3, m2-m3-m1, m3-m1-m2, m3-m2-m1

TECNOLOGÍAS DE RED AVANZADAS – Master IC Classification of reliable multicast - FIFO  If process P sent messages mi and mj, in that order, then each process in the multicast group will be delivered the messages mi and mj, in that order.  Note that FIFO multicast places no restriction on the delivery order among messages sent by different processes. For example, P1 sends messages m11 then m12, and P2 sends messages m21 then m22. It is possible for different processes to receive any of the following orders: m11-m12-m21-m22, m11-m21-m12-m22, m11-m21-m22-m12, m21-m11-m12-m22 m21-m11-m22-m12 m21-m22-m11-m12.

TECNOLOGÍAS DE RED AVANZADAS – Master IC Classification of reliable multicast – Causal order  If message mi causes (results in) the occurrence of message mj, then mi will be delivered to each process prior to mj. Messages mi and mj are said to have a causal or happen-before relationship.  For example, P1 sends a message m1, to which P2 replies with a multicast message m2. Since m2 is triggered by m1, the two messages share a causal relationship of m1-> m2. A causal-order multicast message system ensures that these two messages will be delivered to each of the processes in the order of m1- m

TECNOLOGÍAS DE RED AVANZADAS – Master IC Classification of reliable multicast – Atomic order  In an atomic-order multicast system, all messages are guaranteed to be delivered to each participant in the exact same order. Note that the delivery order does not have to be FIFO or causal, but must be identical for each process.  Example: P1 sends m1, P2 sends m2, and P3 sends m3.  An atomic system will guarantee that the messages will be delivered to each process in only one of the six orders: m1-m2- m3, m1- m3- m2, m2- m1-m3, m2-m3-m1, m3-m1- m2, m3-m2-m1.

TECNOLOGÍAS DE RED AVANZADAS – Master IC IP Multicast Architecture Hosts Routers Service model Host-to-router protocol (IGMP) Multicast routing protocols (various)

TECNOLOGÍAS DE RED AVANZADAS – Master IC IP Multicast model: RFC 1112  Message sent to multicast “group” (of receivers) Senders need not be group members A group identified by a single “group address” Use “group address” instead of destination address in IP packet sent to group Groups can have any size; Group members can be located anywhere on the Internet Group membership is not explicitly known Receivers can join/leave at will  Packets are not duplicated or delivered to destinations outside the group Distribution tree constructed for delivery of packets No more than one copy of packet appears on any subnet Packets delivered only to “interested” receivers => multicast delivery tree changes dynamically Network has to actively discover paths between senders and receivers

TECNOLOGÍAS DE RED AVANZADAS – Master IC IP Multicast Addresses  Class D IP addresses –  Address allocation: Well-known (reserved) multicast addresses, assigned by IANA: x and x Transient multicast addresses, assigned and reclaimed dynamically, e.g., by “sdr” program  Each multicast address represents a group of arbitrary size, called a “host group”  There is no structure within class D address space like subnetting => flat address space Group ID

TECNOLOGÍAS DE RED AVANZADAS – Master IC IP Multicast Service  Sending Uses normal IP-Send operation, with an IP multicast address specified as the destination Must provide sending application a way to: Specify outgoing network interface, if >1 available Specify IP time-to-live (TTL) on outgoing packet Enable/disable loop-back if the sending host is/isn't a member of the destination group on the outgoing interface  Receiving Two new operations Join-IP-Multicast-Group(group-address, interface) Leave-IP-Multicast-Group(group-address, interface) Receive multicast packets for joined groups via normal IP- Receive operation