LECTURE NOTES 12
MULTIMEDIA & NETWORKS
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A Chinese proverb tells, “Tell me and I shall forget;
show me and I shall remember; involve me and I
shall understand.” This is what is the spirit behind
multimedia.
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INTEGRATING ASPECTS OF MULTIMEDIA
Image/Video
Capture
Audio/Video
Perception/
Playback
Audio/Video
Presentation
Playback
Image/Video Information
Representation
Transmission
Audio
Capture
Transmission
Compression
Processing
Audio Information
Representation
Media
Server
Storage
A/V
Playback
INTEGRATING ASPECTS OF MULTIMEDIA
Image/Video
Capture
Audio/Video
Perception/
Playback
Audio/Video
Presentation
Playback
Image/Video Information
Representation
Transmission
Audio
Capture
Transmission
Compression
Processing
Audio Information
Representation
Media
Server
Storage
A/V
Playback
INTEGRATING ASPECTS OF MULTIMEDIA
Image/Video
Capture
Audio/Video
Perception/
Playback
Audio/Video
Presentation
Playback
Image/Video Information
Representation
Transmission
Audio
Capture
Transmission
Compression
Processing
Audio Information
Representation
Media
Server
Storage
A/V
Playback
FOR NEXT FOUR WEEKS WE WILL COVER
TRANSMISSION/NETWORKS OF MULTIMEDIA
Image/Video
Capture
Audio/Video
Perception/
Playback
Audio/Video
Presentation
Playback
Image/Video Information
Representation
Transmission
Audio
Capture
Transmission
Compression
Processing
Audio Information
Representation
Media
Server
Storage
A/V
Playback
MULTIMEDIA SYSTEM/NETWORK
Sender/Server
MM
Application
OS/Distributed
Systems/Network
Receiver/Client
Capture AV
Code AV
Display AV
DecodeAV
Stream AV, Sync AV, Schedule AV,
Queue/Buffer AV, Shape AV,
Manage AV, Route AV, Retrieve AV,
Pre-fetch/Cache AV, Record AV
Network
MM
Application
OS/DS/Network
WHAT IS MULTIMEDIA?
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It is said that in the future, multimedia shall be the rule and
monomedia shall be the exception.
Multimedia is a tele-service concept that provides integrated
and simultaneous services of more than one telecommunication
services, namely, voice-world, video-world and data-world.
Truly, multimedia is supposed to provide such service in real
time and in interactive mode.
Typical examples of multimedia applications are: WWW,
video conferencing, video on demand, interactive TV,
interactive movies, electronic magazines and journals,
groupware, digital video editing and home shopping.
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Basic three communication media or services are Voice, Video
and Data; and in terms of these the multimedia can
graphically be seen as in Fig. 1. Multimedia is therefore 2 or
more in 1, and in general, N (N>1) in 1 service.
•
Multimedia is telling stories or having entertainments or giving
education etc. with sound, video and picture etc. In general,
multimedia delivers information with audio, video, picture etc.
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FIG. 1: MULTIMEDIA AS COMBINATION MONOMEDIA
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WHAT IS MULTIMEDIA COMMUNICATION?
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Multimedia communication refers to the transmission of the
multimedia information over multimedia networks.
Multimedia networks are to support transmission of multiple
media, namely voice, video, text, data, graphics and still
images often at the same time in interactive and possibly real
time modes.
The several components of a multimedia network are shown in
Fig. 2 (a – d).
The basic five communication networks used to provide
multimedia communication services are: telephone (circuitswitched network), data networks (packet-switched networks),
broadcast networks (television), ISDN (Integrated Services
Digital Network) and BISDN (broadband counterpart to11
Integrated Services Digital Network).
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Fig. 2a (Components of multimedianetwork
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The source is actually the media to be transmitted. The media to be
transmitted is often represented in the digital form.
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The source terminal does the job of compressing source data.
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The backbone networks may be circuit switched telephone network,
packet switched data network, and Internet. The access and the
delivery networks are shared networks and therefore have packet
loss and delay and rate constraint characteristics. The backbone
network has the characteristics of bandwidth, latency, jittering, skew,
packet loss and possible QoS (Quality of Service).
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The destination terminal does the decompression and delivers media
to the destination.
The access and the delivery networks, often known as last-mile
network, are shared capacity networks. The first five entries in Table
(1) are used as access/ delivery networks.
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Telephone Networks/Circuit Switched Networks
•PSTN (Public Switched Telephone Network) (backbone, access,
delivery)
• PBX (Private Branch Exchange) (backbone, access, delivery)
Packet Switched Networks/Data Networks
• Internet (backbone)
• LAN (Local Area Network) (access, delivery)
• Intranets (access, delivery)
• ISPN (Internet Service Provider Network) (access, delivery)
• X.25 (Backbone, access, delivery)
Long Haul Broadcast Networks
• Satellite/Terrestrial (backbone, access, delivery)
• Cable (backbone, access, delivery)
Integrated Services Digital Network (ISDN)
• NISDN (access, delivery, backbone)
• BISDN (access, delivery, backbone)
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Backbone
Circuit-switched
Packet-switched Broadcast
Integrated services
networks
networks
networks
digital networks (ISDN)
PSTN, PBX
X.25 Internet
Satellite,
NISDN
Access and
LAN,
ISPN,
Terrestrial
(Narrowband ISDN),
delivery
Intranet
Cable
BISDN (Broadband
ISDN)
Multimedia Applications and Services
Fig. 2(b): Multimedia communication networks
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Fig. 2 (c): Multimedia networks and their services
Circuit Switched Telephone Networks
• Fixed and Mobile Telephony
• Video Telephony /Voice Mail /Fax
• Video Conferencing
• Entertainment/Video on Demand
• Access to Internet
Packet Switched Internet
• E-mail/File Transfer
• Multimedia Mail
• Video Telephony/Video Conferencing/Internet Phone
• E-commerce
• Multimedia Mail
• Video Telephony/Video Conferencing/Internet Phone
• E-commerce
• Analog and Digital Audio andTV
• CD, Video/Audio on Demand/Interactive TV
• Access to Internet/PSTN
• Digital Telephony/Fax
• Video Telephony and Conferencing
• LAN Interconnection
• Access to Internet
• ATM LAN: Interactive Services
•ATM MAN/ ATM WAN as Backbone: High Speed/High Bit Rate
Interconnection
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Voice/Audio/Telephone
—→
ISDN, SONET,
ATM
Video Real Time
—→
SONET, ATM
Video Distributive
—→
IP, SONET, ATM
Data
—→
IP, ISDN, ATM
Fig. 2(d): Services versus technology
Multimedia Services/Traffic —→ Supporting
Communication/Network Technologies
NOTICED THAT FUTURE IS WITHATM
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TABLE 1: CHARACTERISTICS OF
DIFFERENT SERVICES
Services
Typical
Time
supporting
sensitive/
network
Latency
Burstiness
Error
Typical
tolerant
bit rate
Directionality
Typical
session
holding
time
Audio/Voice
PSTN/
Yes
No
Yes
64 Kbps
Bi-directional
Minutes
Yes
Moderate
Yes, but
Around 1
Bi-directional
Minutes/
limited
Mbps
Moderate
Yes, but
A few
Directional
Hours
limited
Mbps
Yes
No
A few
Directional
Hours
Telephone
Digital video
Cable/
(real time)
Terrestrial/
Hours
Satellite
Digital video
Do
No
(distributive)
Data
Internet/
Packet
No
Kbps
Switched
Network
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• Different services of multimedia bear different characteristics (Table 1) requiring different
networks to support different services. For example, data is known as BAD IT, where “B” refersto
bursty; meaning that for a very long time there may not be any data for communication, but
suddenly there may emerge a huge chunk of data for a short duration. Thus, the network and
transmission link should have the provision to cope up with the wide data-rate variation. In voice
communication the data rate is fairly constant.
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“A” refers to asymmetric, meaning that flow of data is heavily tilted towards unidirectional
transport. On a single stroke of command, a destination may have to response for a long period
towards source; the one example of which is the transfer of bank details from a branch bank to the
headquarter of the bank. In the voice communication the bi-directional flow variation is around
40% to 60%.
• “D” stands for delicacy. The data is delicate. It is more error-prone. This is because, in the data
communication, the machines are involved. Unlike voice communication, human perception and
intelligence are absent in data communication. So care must be taken to protect data fromerror.
• “IT” stands for Insensitive to Time. Data normally does not require real time transport or on-line
interactive communication. Data may tolerate delay. Thus, data transport may be made with
intermediate buffering and storage while being delivered in between the source and destination
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INTRODUCTION
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Distributed system
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a collection of independent computers appears to its
users as a single coherent system.
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Often a middleware on top of the operating system.
Computer Networks
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computers are separated but interconnected.
user has to log onto the remote machine to run a
program
Computer Center
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the coherence and middleware are absent.
a room with a large computer for users
Client-server model
Peer-to-peer (P2P)
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NETWORK HARDWARE
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Transmission technology
• Broadcast networks: Broadcasting and multicasting
• Point-to-point networks: unicasting
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Scale
• Local Area Network (LAN)
• Ethernet, IEEE 802.3
• Token bus, IEEE 802.5
• Metropolitan Area Network (MAN)
• Cable TV, head end
• WiMAX, IEEE 802.16
• Wide Area Network (WAN)
• Switching element (router),
• routing algorithm
• Store-and-forward or packet-switched
• Wireless Networks (Bluetooth and IEEE 802.11)
• Home Networks and internetworks (gateway)
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SWITCHING TERMS
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Switching Nodes:
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Not concerned with content of data
Stations:
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Intermediate switching device that moves data
End devices that wish to communicate
Each station is connected to a switching node
Communications Network:
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A collection of switching nodes
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TECHNIQUES USED IN SWITCHED
NETWORKS
• Circuit switching
• Dedicated communications path
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between two stations
E.g., public telephone network
• Packet switching
• Message is broken into a series of
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packets
Each node determines next leg of
transmission for each packet
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PHASES OF CIRCUIT SWITCHING
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Circuit establishment
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Information Transfer
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Information transmitted through the network
Data may be analog voice, digitized voice, or binary data
Circuit disconnect
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An end to end circuit is established through switching nodes
Circuit is terminated
Each node deallocates dedicated resources
Characteristics
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Inefficient
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Channel capacity dedicated for duration of connection
Utilization not 100%
Delay prior to signal transfer for establishment
Once established, network is transparent to users
• Information transmitted at fixed data rate with only propagation delay
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TCP/IP LAYERS
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Physical layer
(All layers are relative with wireless
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Network access layer
networks in multimedia Communication)
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Internet layer
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Host-to-host, or transport layer
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Application layer
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TCP/IP ADDRESSING
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TCP/IP LAYERS
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Physical layer covers the physical interface between a data transmission
device and a transmission medium or network
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Physical layer specifies:
• Characteristics of the transmission medium
• The nature of the signals
• The data rate
• Other related matters (coding, Radio Frequence…)
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Network access layer concerned with the exchange of data between an end
system and the network to which it's attached
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Software used depends on type of network
• Circuit switching
• Packet switching (e.g., X.25)
• LANs (e.g., Ethernet)
• Others (WiFi, WiMAX, Bluetooth…)
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TCP/IP LAYERS
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Internet Protocol (IP)
• Provides routing functions to allow data to traverse multiple interconnected networks
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Implemented in end systems and routers (mesh wirelessnetwork)
Transport Layer
• Commonly uses transmission control protocol (TCP)
• Provides reliability during data exchange
• Completeness
• Order
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Application Layer
• Supports user applications
• Uses separate modules that are particular to each different type of application
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COMMON TCP/IP APPLICATIONS
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Simple mail transfer protocol (SMTP)
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File Transfer Protocol (FTP)
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TELNET
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OSI LAYERS
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Application Layer
• Provides access to the OSI environment for users
• Provides distributed information services
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Presentation Layer
• Provides independence to the application processes from differences in data representation
(syntax)
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Session Layer
• Provides the control structure for communication between applications
• Establishes, manages, and terminates connections (sessions) between cooperating
applications
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Transport Layer
• Provides reliable, transparent transfer of data between end points
• Provides end-to-end error recovery and flow control
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OSI LAYERS
• Network Layer
• Provides upper layers with independence from the data transmission and switching
technologies used to connect systems
• Responsible for establishing, maintaining, and terminating connections
• Data Link Layer
• Provides for the reliable transfer of information across the physical link
• Sends blocks (frames) with the necessary synchronization, error control, and flow
control
• Physical Layer
• Concerned with transmission of unstructured bit stream over physical medium
• Deals with accessing the physical medium
• Mechanical characteristics
• Electrical characteristics
• Functional characteristics
• Procedural characteristics
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ASYNCHRONOUS TRANSFER MODE
(ATM)
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Also known as cell relay
Resembles packet switching
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transfer data in discrete chunks
allows multiple logical connections to be multiplexed over a single physical
interface
Fixed-size cells simplify processing at ATM nodes
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ATM TERMINOLOGY
• Virtual channel connection (VCC)
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Logical connection in ATM
Basic unit of switching in ATM network
Analogous to a virtual circuit in packet switching networks
Exchanges variable-rate, full-duplex flow of fixed-size cells
• Virtual path connection (VPC)
• Bundle of VCCs that have the same end points
• Advantages:
• Simplified network architecture
• Increased network performance and reliability
• Reduced processing and short connection setup time
• Enhanced network services
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VIRTUAL CHANNEL CONNECTION
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Between end users
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carry end-to-end user data or control signaling between two users
Between an end user and a network entity
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Used for user-to-network control signaling
Between two network entities
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Used for network traffic management and routing functions
Virtual Path/Virtual Channel Characteristics
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Quality of service
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Specify parameters such as cell loss ratio and cell delay variation
Cell sequence integrity
Traffic parameter negotiation and usage monitoring
Virtual channel identifier restriction within a VPC
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ATM CELL HEADER FORMAT
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Generic flow control (GFC) –
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Routing field
8 bits, used for routing to and from end user
3 bits, indicates type of information in information field
Cell loss priority (CLP) –
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12 bits at network-network interface
Payload type (PT) –
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8 bits at the user-network interface,
Virtual channel identifier (VCI) –
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Used to alleviate short-term overload conditions in network
Virtual path identifier (VPI) –
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4 bits, used only in user-network interface
1 bit, provides guidance to network in the event of congestion
Header error control (HEC) –
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8 bit, Error code
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EXAMPLES
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CBR applications
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Videoconferencing
Interactive audio (e.g., telephony)
Audio/video distribution (e.g., television, distance learning, pay-per-view)
Audio/video retrieval (e.g., video-on-demand, audio library)
UBR applications
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Text/data/image transfer, messaging, distribution, retrieval
Remote terminal (e.g., telecommuting)
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