CMSC691C Multimedia Networking A Course Overview - PowerPoint PPT Presentation

Title: CMSC691C Multimedia Networking A Course Overview


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CMSC691C Multimedia NetworkingA Course Overview

• Padma Mundur
• CSEE, UMBC
• pmundur_at_csee.umbc.edu

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List of Topics

• Multimedia Networking Source Representations,
  Networks, and Applications
• Multimedia Compression Fundamentals Coding
  Standards
• Scalable Video Coding for Heterogeneous Networks
• Fundamentals of IP Routing
• IETF QoS Efforts
• Existing Solutions for Scalable Multimedia QoS

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The Telephone (Voice) Network

• Circuit switched network
• Analog (since1890) manually switching
• Digital voice ? bit stream (64 Kbps)
• Better channel utilization by time-division
  multiplexing
• Reservation fixed for the whole transmission

A
C
B
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The Internet (Data) Network

• Packet-switched network
• packets share resources (buffers, links)
• reservation not fixed, but on-demand
• multiple links (connectivity, reliability)
• buffers (store, process, forward)
• control information in packets (s,d,seq)

5
Internet Users Growth
Source www.isc.org

• 1B mobile users by 2005 and 1B Internet users by
  2005
• 90 of all new mobile phones will have internet
  access by 2003 (Morgan Stanley Dean Witter, May
  2000)

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Multimedia over IP Networks
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Multimedia Networking Applications

• Media Broadcast simultaneous pushing of content
  to multiple recipients
• Network IP Multicast Multicast enabled routers
  and switches
• Hosted Streaming content users initiate requests
  and content networks/providers push content
  through network
• Interactive Conferencing no centralized source
  of contents

8
Multimedia Broadcast over IP
IP (internet protocol) makes it possible to link
all (global) nodes together independent of
applications and terminal devices
content provider
clients
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Hosted Multimedia Streaming
To hear or view a media file without downloading
it
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Interactive Conferencing and Meeting Server
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How A Server Distributes the Data
Meeting Token Holder
12
Dynamic Token Passing
Old Token Holder
New Token Holder
13
Multimedia Signals and Bitrates
14
Audio Video Quality Requirements
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IP Networks

• IP uses packet switching
• Suitable for unexpected burst of data without
  establishing an explicit connection.
• Bandwidth is shared statistically so data can be
  sent at any time.
• IP is not reliable nor delay-bounded.
• Best effort
• Queuing delay, especially when congested.
• Network failures can cause temporary packet loss.
• Time critical applications cannot operate well
  due to large e-mail attachments and Web surfing
• Delay and jitter degrade voice and video
  performance

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Multimedia Signals

• Text
• Speech
• Audio
• Image (B/W and color)
• Video
• Graphics Animation
• Documents (various formats)

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Image Video Coding Standards

• Combination of lossy (transform coding) and
  lossless (run-length, Huffman, Arithmetic coding,
  LZW, etc) coding techniques along space and time.
• JPEG - Joint Photographic Experts Group
• Still image compression, intraframe picture
  technology
• Motion JPEG (MJPEG) is sequence of images coded
  with JPEG
• MPEG - Moving Picture Experts Group
• Defined by ISO/IEC, several standards MPEG1,
  MPEG2, and now MPEG4
• H.263/H.263/H.26L - Videophone/Conferencing
• Low to medium bit rate, quality, and
  computational cost defined by ITU
• Used in H.320 and H.323 video conferencing
  standards

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A Complete JPEG Encoding
DCT
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From Image to Video Coding

• Intra-frame compression (similar to JPEG)
• Remove redundancy within frame (spatial)
• Inter-frame compression (motion compensation)
• Remove redundancy between frames (temporal)
• Rate Control (constant bit-rate or constant SNR)

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Video Coding Standards

• MPEG1 VHS quality, VCD (1992)
• CIF images, 420 sampling, 1.5 Mbs, Frame
  encoding
• MPEG2 - broadcast quality, HDTV and DVD (1994)
• CCIR 601 images, 422 sampling, 4-15 Mbs
• Interlaced and progressive scanning, Frame and
  field
• H.261 for videotelephony (p1,2)
  videoconferencing (pgt 6) (1992)
• Improve JPEG through temporal redundancy
• H.263 low bitrate video coding (1995)
• Half pixel motion compensation, 4 (optional)
  modes
• Optimized VLC tables better motion vector
  prediction
• H.26L(H.264) flexible, high quality video
  applications (2002)
• 1/4 pixel accuracy for MC, 7 different block
  sizes for ME/MC
• Residual coding uses 4x4 blocks an integer
  transform

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MPEG-4 An Emerging Standard

• For multimedia applications
• Interactive natural synthetic contents
• Various access conditions low bit-rate, error
  prone, heterogeneous (scalable)
• Management and protection of media contents
• Standard
• 1st generation (1998-2000) 1st2nd versions,
  frame based content creation communication,
  64-384 Kbps, mobile videophone (3G and IP) and
  digital camcorder
• next generation (2001-) upto 2Mbps, frame/object
  based, scalable streaming, interactive set-top
  box

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Heterogeneous IP Networks

• Adaptive Rate Control
• Scalable Coding
• Real-time bandwidth estimation
• Receiver feedback
• Adaptive Multicast control

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Video Scalable Coding

• Why a scalable video codec?
• Compression efficiency
• Robustness with respect to packet loss
• Adaptation to the changing bandwidth
• Techniques of scalable video coding
• Temporal
• Spatial
• Signal-to-Noise Ratio (SNR)
• Data Partition
• Wavelet
• Fine Granularity Scalability (FGS)

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IP Stack A Layered Architecture
Web (HTTP), E-mail (SMTP), File transfer (FTP),
Name resolution (DNS), Remote terminal (TELNET),

Reliable multi-connection bit-stream
(TCP), unreliable multi-connection (UDP).
Unreliable end-to-end delivery of packets up to
64 KB.
Point-to-point links (PPP, SONET, ), LANs
(Ethernet, FDDI, wireless, )
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IP Packet Routing Delay and Loss
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Queuing and Scheduling (1)

• FIFO - First In First Out queuing, definitely not
  compatible with QoS since high priority packets
  can get stuck behind low priority packets

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Queuing and Scheduling (2)

• Priority Scheduling - services higher priority
  queue whenever there are packets present, can
  lead to starvation of lower priority queues

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Queuing and Scheduling (3)

• Custom Queuing (or Weighted Round Robin
  Scheduling) - services all queues (with different
  service time) within a traffic class, round robin
  assuring that all queues get appropriate treatment

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Queuing and Scheduling (4)

• Weighted Fair Queuing (WFQ) - queue is serviced
  based on a weight proportional to the bandwidth
  dynamically allocated to it

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Congestion Control Queue Discard

• Tail Drop
• Drops arriving packets when buffers in queue are
  full, can lead to network meltdown due to TCP
  global synchronization
• RED Random Early Detection
• Queuing algorithm for congestion avoidance that
  randomly discards packets from queues in an
  attempt to prevent TCP retransmits simultaneously
  on all flows

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Congestion Control Queue Discard

• WRED Weighted Random Early Discard
• A variant of RED that attempts to weight queues
  for random early discard
• Tri-Color Marking (deterministic)

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IP QoS and Multimedia

• Quality of Service (QoS) methods aim at trading
  quality vs. resources to meet the constraints
  dictated by the user, the functionality and the
  platform.
• QoS originally developed in network
  communication, and recently extended to the
  domain of multimedia communication.
• QoS relevant in multimedia scalable systems,
  where the resources and the functionality can be
  controlled by a set of parameters.

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IP Quality of Service (QoS)

• Techniques to intelligently match the
  performance needs of applications to available
  network resources
• QoS Metrics
• availability
• delay (latency)
• delay variation (jitter)
• throughput (average and peak rates)
• packet loss

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IETF IP QoS Efforts

• Policy based IP QoS Solutions
• Integrated Services (RSVP protocol) flow based
• Differentiated Services (DiffServ byte settings)
  packet based
• Multi-Protocol Label Switching (MPLS)
  flowpacket based
• IP Multicast and Anycast
• IPv6 QoS Support

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Connection Oriented QoS

• Int-Serv (Integrated Services) IETF RFC 1633
• Defined by RSVP requires resource reservation at
  each hop end-to-end for each IP packet flow, and
  end-to-end signaling along nodes in the path
• Reserve resources at the routers so as to provide
  QoS for specific user packet stream
• This architecture does not scale well (large
  amount of states)
• Many Internet flows are short lived, not worth
  setting up VC

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Integrated Services / RSVP

• Sender sends a PATH message to the receiver
  specifying characteristics of
  traffic
• every intermediate router along the path
  forwards the PATH message to the next hop
  determined by the routing protocol
• Receiver responds with RESV message after
  receiving PATH. RESV requests resources for
  flow

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Connectionless QoS IP Diff Serv

• Mark IP packet to specify treatment IETF RFC
  2474, e.g., first class, business class, coach,
  standby
• Per Hop Behaviors (PHBs) based on network-wide
  traffic classes
• Flows are classified at the edge router based on
  rules, and are aggregated into traffic classes,
  allowing scalability
• Diff Serv uses the IP header TOS byte (first 6
  bits), which is renamed the DS field
• Diff Serv defines code points (DSCP) for the DS
  field, DE (default) 000000 best effort, and
  EF (Expedited Forwarding) 101110 low latency,
  etc.

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DiffServ Operation

• Each ISP configures its own routers to match the
  service that it offers, and each ISP has its own
  DiffServ Domain.

Customer Site
ASP
email
Video
Voice
PHB
PHB
PHB
SLA (service level agreement)
SLA
SLA
Edge Router
Interior Nodes
39
MPLS Fundamentals

• MPLS is a forwarding scheme that tags packets
  with labels (independent of layers 2,3) that
  specify routing and priority (IETF RFC 3031)
• Enables scalability by alleviating IP over ATM
  problems
• Defines a homogeneous network based upon
  label-switching
• Requires all devices (i.e., ATM switches) to be
  capable of routing
• Enables differentiated services via QoS-aware
  label switched paths (LSPs)
• Designed to run over a wide range of media
• ATM, frame relay, and Ethernet

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Unicast/Multicast
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Multimedia IP Multicast

• Why multicast?
• When sending same data to multiple receivers
• Better bandwidth utilization
• Lesser host/router processing
• Receivers addresses unknown
• Applications
• Video/audio conferencing
• Resource discovery/service advertisement
• Media streaming and distribution

42
IP Multicast Service Model

• IETF RFC 1112, each multicast group is identified
  by a class D IP address
• Range from 224.0.0.0 through 239.255.255.255
• Well known addresses designated by Internet
  Assigned Number Authority (IANA)
• Reserved use 224.0.0.0 through 224.0.0.255
• Members join and leave the group and indicate
  this to the routers
• Multicast routers listen to all multicast
  addresses and use multicast routing protocols to
  manage groups

43
What IPv6 can Offer?

• Global Addressing (128 bits)
• 1 million networks per human
• 20 hosts per m2 of Earth
• Plug and play
• Efficient mobility (instant-on ad-hoc networking)

44
IPv6 Key Features and Advantages

• Increased Address Space (128 bits)
• Efficient and extensible IP datagram
• Improved host and router discovery
• Plug and Play
• Enhancements for Quality of Service (QoS)
• Improved Mobile IP support
• Coexistence with IPv4
• Built in security (authentication and encryption)
  in IP layer

45
IPv6 Support of QoS

• IPv6 Flow Labels provide support for Data Flows
• Packet Prioritizing-- sure that high priority
  traffic is not interrupted by less critical data
• IPv6 supports Multicast Anycast
• Multicast delivers data simultaneously to all
  hosts that sign up to receive it
• Anycast allows one host initiate the efficient
  updating of routing tables for a group of hosts.

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Existing Scalable Multicast Solutions

• Content Distribution Networks
• Receiver-Driven Layer Multicast (RDLM)
• Source Adaptive Multi-Layer Multicast (SAMM)
• Filtering Method
• Destination Set Grouping (DSG)
• Multiple Description Coding (MDS) of Multimedia

47
Distributing Content to the Edges

• Adding backbone bandwidth is not the best
  solution, the last mile (edge) connection is even
  more critical.
• How to direct traffic to the site (routing) and
  resolve the appropriate server (load balancing)
  that will perform best for a particular query
  (front-end content delivery).
• How to keep content updated efficiently (back-end
  content delivery)

48
Getting Contents to the Edge

• Caching (on-demand pull)
• Contents may be pulled from another proxy cache
  in the hierarchy or the origin of the contents.
• Problems stale content delivery, hit statistics
  loss, dynamic contents
• Replication (changes made on the origin server)
• Updates are pushed to replica using a
  back-end content delivery system.
• The origin server is in total control (database
  keep track of content changes), with scalable
  architecture (multicast or packet-relay).

49
Getting Contents to the Edge

• Resolution Problem
• The best site geographic vs. network proximity
  (quickest service)
• Domain Name Service (DNS) criteria of
  authoritative servers (domain) hops, of router
  hops, health/load of site, round trip latency,
  packet loss rate, etc.
• Hybrids of Caching/Replication
• Reverse Proxy Cache all queries directed to
  proxy caches by load balancer for front-end
  delivery.
• Pre-Filling of Proxy Caches parts of the Web
  site are pre-filled to the cache i.e., replica
  in proxy cache form

50
Content Distribution Network (CDN)

• Service providers using proprietary
  caching/replication technologies to build overlay
  networks (internet or satellite) to deliver
  contents application level multicast

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Receiver-driven Layer Multicast (RLM)

• RLM Protocol Concepts (McCanne 1996) Source
  No active role in the protocol. Receivers On
  congestion, drop a layer. On spare
  capacity, add a layer.
• When to drop a layer Whenever congestion
  happens. Congestion is expressed explicitly in
  the data stream through lost packets.
• When to add a layerJoin-experiment To carry
  out active experiments by spontaneously adding
  layers at well chosen time.

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RLM Characteristics

• A fixed number of multicast groups.
• Lack of granularity adaptation
• Severe quality degradation when pack loss on
  base layer.
• Slow adaptation to changes of varying network
  bandwidth (Liu, Hwang 2002)
• Synchronization is crucial
• Well-developed protocol is crucial

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Source Adaptive Multi-layer Multicast

• SAMM Protocol Concepts (Suda 1998)
• Video is encoded into several layers and each
  layer has an unique discarding priority.
• When a network link experiences congestion,
  packets from the lowest priority layer are
  discarded.
• The video source obtains backward feedbacks from
  receivers to adjust the number of video layers
  and also the encoding rate for each layer.