1. E0262 - Multimedia Communications Anandi Giridharan Electrical Communication Engineering, Indian Institute of Science, Bangalore – 560012, India Multimedia Communications

2. E0262 - Multimedia Communications Network Topologies Evolution – LAN: Local Area Network – WAN: Wide Area Network – WLAN: Wireless Local Area Network

3. E0262 - Multimedia Communications Network Topologies Evolution ● LAN ● A LAN is a high-speed data network that covers a relatively small geographic area. eg. home, office etc ● LANs offer computer users many advantages, including shared access to devices and applications, file exchange between connected users, and communication between users via electronic mail and other applications. ● LAN data transmissions fall into three classifications: unicast, multicast, and broadcast. ● LAN Topologies: bus, ring, star, and tree. ● WLAN ● WAN

4. E0262 - Multimedia Communications BUS TOPOLOGY Bus networks: A bus network topology is a network architecture in which a set of clients are connected via a shared communications line, called a bus. Bus networks are the simplest way to connect multiple clients, but often have problems when two clients want to transmit at the same time on the same bus. Thus systems which use bus network architectures normally have some scheme of collision handling or collision avoidance for communication on the bus, quite often using Carrier Sense Multiple Access

5. E0262 - Multimedia Communications BUS NETWORK

6. E0262 - Multimedia Communications Ring networks, A ring network is a network topology in which each node connects to exactly two other nodes, forming a circular pathway for signals: a ring. Data travels from node to node, with each node handling every packet. Because a ring topology provides only one pathway between any two nodes, ring networks may be disrupted by the failure of a single link. A node failure or cable break might isolate every node attached to the ring.

7. E0262 - Multimedia Communications Ring network

8. E0262 - Multimedia Communications Tree topology Tree Topology is a combination of the bus and the Star Topology. The tree like structure allows you to have many servers on the network and you can branch out the network in many ways.

9. E0262 - Multimedia Communications WAN A WAN is a data communications network that covers a relatively broad geographic area i.e., any network whose communications links cross metropolitan, regional, or national boundaries. Point-to-Point Links: A point-to-point link provides a single, pre-established WAN communications path from the customer premises through a carrier network, such as a telephone company, to a remote network.

10. E0262 - Multimedia Communications Circuit Switching Switched circuits allow data connections that can be initiated when needed and terminated when communication is complete. This works much like a normal telephone line works for voice communication

11. E0262 - Multimedia Communications Packet Switching Packet switching is a WAN technology in which users share common carrier resources.

12. E0262 - Multimedia Communications Wireless LAN ● A wireless LAN or WLAN is a wireless local area network, which is the linking of two or more computers without using wires. ● WLAN utilizes radio waves to enable communication between devices in a limited area, also known as the basic service set. ● This gives users the mobility to move around within a broad coverage area and still be connected to the network.

13. E0262 - Multimedia Communications Multimedia Communication System – Interactive Multimedia Design – Interlacing – Interleaved – Linear Multimedia – Non-Interactive Multimedia – Nonlinear Multimedia

14. E0262 - Multimedia Communications Interactive Learning System for Conceptualization

15. E0262 - Multimedia Communications Interlace is a technique of improving the picture quality of a video signal by removing flicker without consuming any extra bandwidth. This animation demonstrates the interline twitter effect. The two interlaced images use half the bandwidth of the progressive one.

16. E0262 - Multimedia Communications Interleaving in disk storage The primary purpose of interleaving was to adjust the timing differences between when the computer was ready to transfer data, and when that data was actually arriving at the drive head to be read. Interleaving was used to arrange the sectors in the most efficient manner possible, so that after reading a sector, time would be permitted for processing, and then the next sector in sequence is ready to be read just as the computer is ready to do so. Interleaving is used in digital data transmission technology to protect the transmission against burst errors. These errors overwrite a lot of bits in a row, so a typical error correction scheme that expects errors to be more uniformly distributed can be overwhelmed. Interleaving is used to help stop this from happening.

17. E0262 - Multimedia Communications Linear Multimedia Multimedia may be broadly divided into linear and non- linear categories. Linear active content progresses without any navigation control for the viewer such as a cinema presentation. Non-linear content offers user interactivity to control progress as used with a computer game or used in self-paced computer based training. Non-linear content is also known as hypermedia content.

18. E0262 - Multimedia Communications If the sequence and timing of the multimedia elements can be controlled by the user, then one can name it as Non-Interactive Multimedia. ● Streaming Audio ● RealPlayer ● Streaming Video ● quick time Non-Interactive Multimedia.

19. E0262 - Multimedia Communications Multimedia Networks ● Technical Issues – Admission control:Admission control is a network Quality of Service (QoS) procedure. – Admission control determines how bandwidth and latency are allocated to streams with various requirements. – An application that wishes to use the network to transport traffic with QoS must first request a connection, which involves informing the network about the characteristics of the traffic and the QoS required by the application. – This information is stored in a traffic contract. The network judges whether it has enough resources available to accept the connection, and then either accepts or rejects the connection request. This is known as Admission Control.

20. E0262 - Multimedia Communications Multimedia Networks – Scheduling: Scheduling is a key concept in computer multitasking and multiprocessing operating system design, and in real-time operating system design. It refers to the way processes are assigned priorities in a priority queue. This assignment is carried out by software known as a scheduler. – Different computer operating systems implement different scheduling schemes. Unix implementations use a scheduler with multilevel feedback queues. – Windows 3.1 and Macintosh OS 9 use a simple non-preemptive scheduler which requires programmers to instruct their processes to "yield" in order for other processes to gain some CPU time. Windows NT 4.0-based operating systems use a multilevel feedback queue.

21. E0262 - Multimedia Communications Multimedia Networks – Congestion Control: A congestion control system typically monitors various factors like CPU occupancy, link occupancy and messaging delay. Based on these factors it takes a decision if the system is overloaded. If the system is overloaded, it initiates actions to reduce the load by asking front end processors to reject traffic.

22. E0262 - Multimedia Communications Multimedia Networks ● Resource management – resource management is the efficient and effective deployment of an organization's resources when they are needed. – Resource Management and Scheduling Strategies collectively addresses multiple issues including QoS, throughput, responsiveness and efficiency.

23. E0262 - Multimedia Communications INTERNET The Internet is a global network of interconnected computers, enabling users to share information along multiple channels.

24. E0262 - Multimedia Communications Internetworking Despite the incompatibilities among network technologies, researchers devised a scheme for providing universal service among heterogeneous technologies called internetworking. Hardware is used to interconnect a set of physical networks and common software on all the attached computers provides universal service. The resultant system is known as an internetwork or internet.

25. E0262 - Multimedia Communications Connection to Internet

26. E0262 - Multimedia Communications There are many ways to connect to the Internet from a personal workstation: 1. Dial-Up:With a dial-up connection, the Internet user can connect to the Internet via his or telephone line and an Internet service provider. Broadband connections offer another way to connect to the Internet. In this category are cable and DSL connections. cable connection, the user must subscribe to a cable- television/Internet service. DSL (Digital Subscriber Line): DSL offers much faster speeds than those available with dial-up modems. Satellite Internet service is another form of high-speed Internet connection.It employs telecommunications satellites to allow users to connect to the Internet 4.

27. E0262 - Multimedia Communications Multimedia Internet Protocols ● Multimedia over TCP: TCP in connection-oriented protocol that is reliable including flow control and supports byte-stream in full duplex mode. ● The multicast method to send data to more than one client is not supported by the TCP protocol. ● Delays is exactly what we do not want in real-time data transmissions. ● For example in a video transmission, we just drop the lost packet and display the previous packet a second time. For the human eye this little trick does not affect the quality. So reliable transmission on transport layer is not exactly what we need for multimedia transmissions. ● TCP is not a good basis to transport multimedia real-time data over a network, to summarize the usability of TCP.

28. E0262 - Multimedia Communications Multimedia over UDP UDP is a connectionless protocol that tries best effort delivery with no flow-control and included message support. UDP is not reliable and that is one of the key advantages for real-time transmissions. UDP also supports multicast methods. This protocol does not support flow-control and that is actually very important for real-time applications.

29. E0262 - Multimedia Communications RTP ● Real-time Transport Protocol (RTP) provides support for the transport of real-time data such as video and audio streams. ● RTP needs support from lower layers that actually have control over resources in switches and routers ● RTP/RTCP provides functionality and control mechanisms necessary for carrying real-time content. ● RTP/RTCP itself is not responsible for the higher-level tasks like assembly and synchronization. These have to be done at application level.

30. E0262 - Multimedia Communications RTCP ● Real-Time Control Protocol extends RTP ● In an RTP session, participants periodically send RTCP packets to convey feedback on quality of data delivery and information of membership. ● Packets defined for carrying control information: – SR: Sender report, for transmission and reception statistics from session participants that are – active senders. – RR: Receiver report, for reception statistics from session participants, that are not active – senders. – SDES: Source description items, including CNAME – BYE: Indicates end of participation – APP: Application specific functions

31. E0262 - Multimedia Communications Multimedia Internet Protocols ● SAP: Session Announcement Protocol:used to assist the advertisement of multicast multimedia conferences and other multicast sessions, and to communicate the relevant session setup information to prospective participants. ● SDP: Session Description Protocol protocol for multimedia sessions. A common mode of usage is for a client to announce a conference session by periodically multicasting an announcement packet to a well known multicast address and port using the Session Announcement Protocol ● MBONE Tools:MBONE stands for "Multicast Backbone", a virtual network. The network originated from an effort to multicast audio and video from the "Internet Engineering Task Force" (IETF) meetings. MBONE today is used by several hundred researchers for developing protocols and applications for group communication – SDR(Sesion directory tool), VIC(Video Tool), VAT (Audio tool)and RAT(Robust audio tool).

32. E0262 - Multimedia Communications Multimedia Internet Protocols ● RSVP:The Resource ReSerVation Protocol designed to reserve resources across a network for an integrated services Internet. – Network control protocol – Allows data receiver to request a special end-to-end quality of service for its data flows. ● RTSP:Real Time Streaming Protocol which allows a client to remotely control a streaming media server, issuing VCR-like commands such as "play" and "pause", and allowing time-based access to files on a server. – A client-server multimedia presentation protocol to enable controlled delivery of streamed multimedia data over IP network. – Aims to provide the same services on streamed audio and video just as HTTP does for text and graphics.

33. E0262 - Multimedia Communications Multimedia Communications ● High-Density File Transfers. ● Graphics File Transfers: using ftp ● Audio File Transfers ● Video File Transfers ● Audio Communication ● Computer-Based Telephony ● Computer-Based Audio Conferencing ● Streaming Audio ● Video Communication ● Video Conferencing ● Streaming Video