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Multimedia Communications E0262 - Multimedia Communications Multimedia Networks(Technical Issues) MM applications and systems require new system mechanisms to handle large volumes of time dependent data in real time (media streams). The most important mechanism is QoS management, which includes resource negotiation, admission control, resource reservation and resource management. Negotiation and admission control ensure that resources are not over allocated, resource management ensures that admitted tasks receive the resources they were allocated. Excessive loss in video transmission affect the performance of video quality. E0262 - Multimedia Communications The necessary traffic management components to support QoS are: · Admission control: The admission control component takes into account resource reservation requests and the available capacity to determine whether to accept a new request with its QoS requirements. Admission control delivers a contract to the application guaranteeing: For each computer: CPU time available at specific intervals, memory etc. Before admission it must assess resource requirement and reserve them for the application. Flow specs provide some information for admission control. There is a optimization problem: clients don't use all the resource that they requested. Flow specs may permit a range of qualities Admission controller must negotiate with applications to produce an acceptable result. · Resource management: QoS can be provided using over-provisioning of a network, which increases the cost incurred by the provider. Efficient resource management is a cost-effective solution for the provider and it ensures that applications will get the specified QoS during the course of its execution. E0262 - Multimedia Communications · Scheduling of resources: The scheduling component provides QoS by allocating resources depending on the service requirements. This requires mapping the user-defined QoS requirement to resource allocations for providing the service. Fair scheduling allows all processes some portion of the resources based on fairness. eg. round robin scheduling (equal turns), fair queuing (keep queue lengths equal) Not appropriate for real time MM because there are deadlines for the delivery of data. Real time scheduling: traditionally used in special OS for system control application. Eg avionics must ensure that tasks are completed by a scheduled time. Real time MM requires real time scheduling with very frequent deadlines. E0262 - Multimedia Communications • Scaling and filtering • Scaling reduces flow rate at source. • Temporal: skip frame or audio samples • Spatial: reduce frame size or audio sample quality • Filtering reduces flow at intermediate points. • e.g: RSVP is QoS negotiation protocol that negotiates the rate at each intermediate node, working from targets to the source. E0262 - Multimedia Communications · Congestion control: Congestion control is required to avoid anything bad from happening inside a network domain. The Internet is a packet switched network that unlike circuit switched networks takes advantage of the statistical multiplexing giving better bandwidth utilisation. Lack of any access control mechanisms in the core Internet concept allows injecting unlimited amount of data into the network. As speed of links and router capabilities are limited, packets buffering in the intermediate routers was introduced, so as to queue incoming packets which cannot be handled instantly. Furthermore, as buffers also have limited space, packets are dropped when the router buffer is filled above some threshold. E0262 - Multimedia Communications • Providing satisfactory service for multiple flows, requires the network end-points to adapt their rates to existing network conditions Figure: illustrates possible congestion scenario E0262 - Multimedia Communications Some applications may not follow the standard protocol description and try to steal resources, thereby deteriorating the QoS of other applications. Mechanisms are needed to recover from congestion and control flows accordingly. · Policing/Shaping: Users might send traffic at a rate higher than the agreement. Policing is necessary to monitor these situations, and shaping makes the traffic smooth and reduces its variations over time. E0262 - Multimedia Communications Challenges in Multimedia Networking We analyze the challenges encountered in realizing scalable multimedia networks with quality of service guarantees. (i) seamless connection management between the network and the multimedia devices, (ii) multimedia abstractions with QOS guarantees, and (iii) the integration of service, traffic control and network management architectures. The fundamental requirement on multimedia networks supporting applications like interactive multimedia, teleconferencing, video on demand etc., is to guarantee quality of service (QOS). E0262 - Multimedia Communications Challenges in multimedia networking based on a reference model for broadband networks and Multimedia Networks. The IRM incorporates monitoring, control, communication, and abstraction primitives that are organized into the Traffic Control Architecture, the Management Architecture, the Information Transport Architecture and the Telebase Architecture, respectively. The sub-division of the IRM into the Management and the Traffic Control Architectures on the one hand, and the Information Transport Architecture on the other, is based on the principle of separation between communications and controls. E0262 - Multimedia Communications Multimedia Network Reference Model E0262 - Multimedia Communications The Integrated Reference Model is organized into five planes The Management Architecture resides in the network management or N- plane, and covers the functional areas of network management, namely, configuration, performance, fault, accounting and security management. Manager and agents, its basic functional components, interact with each other according to the client-server paradigm. E0262 - Multimedia Communications The Traffic Control Architecture consists of the resource control, The M-plane comprises the entities and mechanisms responsible for resource control, call scheduling, call admission, and call routing; E0262 - Multimedia Communications C-plane those for connection management and control, and is based on a signalling network. The Information Transport Architecture is located in the user transport or U-plane, and models the protocols and entities for the transport of user information. The U-plane is horizontally layered, following the ISO Reference Model for Open System Interconnection. Finally, the Telebase Architecture resides within the Data Abstraction and Management or D-plane, and implements the principles of data sharing for network monitoring and control primitives. E0262 - Multimedia Communications The extension of this model to the multimedia networking architecture is simple. The functionality of the planes is extended to include Customer Premises Equipment (CPE), i.e., multimedia devices. This simple extension of the IRM is mainly possible due to the fact that multimedia systems and broadband networks consist of producers, consumers and processors of media. The foundations for the operability of these devices in both, multimedia systems and broadband networks, is the same; the only difference appears to be in the overall goal that a group of devices is set to achieve in the network or the multimedia workstation. E0262 - Multimedia Communications Therefore, the N-plane will include system management functionality, and the M-plane will include scheduling, buffer management, routing (when applicable), admission control and flow control. The D-plane will contain objects modeling multimedia devices C-plane binding functionality, and the U-plane transport of user information within the CPE. E0262 - Multimedia Communications Multimedia Hardware/Software Audio/Video Hardware: Traditional photographic and video equipments have digital counterparts to facilitate the process of graphics and mm creation: Digital Video (DV): eliminates the method converting analogue video to digital by capturing video digitally. Analogue to Digital devices: convert analogue video signal to digital video Built-in Hardware: we can create audio file from audio CDs, microphones and other external audio sources. E0262 - Multimedia Communications Digital Video Software Digital Software • The native video format for windows computers is audio/video interleaved files. (AVI) • Once video is obtained, it may need editing via software. • Codecs are sued to compress movie files so that the are small enough to deliver over the internet. • Also for reducing of data transfer rate. E0262 - Multimedia Communications Multimedia software • MM software combines various elements of audio, graphics, video tools. • Flash, quicktime, realmedia. • Realvideo, RealAudio. E0262 - Multimedia Communications Communication architecture for MM systems • The TCP/IP five layer Reference Model is a widely accepted model for designing network protocols. To single out the multimedia characteristics, we logically partition the five layer reference model into a four layer multimedia design model . Application layer, the Multimedia Integration Control and Synchronization (MICS) layer, the Inter-Process Communication and Synchronization layer (IPCS) and the Network layer. E0262 - Multimedia Communications Comparison of Stacks E0262 - Multimedia Communications IPCS Layer The IPCS layer constitutes the foundation of the multimedia communication environment, The layer provides a flexible set of communication and synchronization primitives. The general function of IPCS is to create a set of mechanisms that allow location-independent exchange of multimedia information between two processes, and provide the adequate tools to express different types of synchronization. In other words, the IPCS layer primitives allow the MICS layer to express communication and synchronization requirements that enforce the characteristics of the supported real-time applications. E0262 - Multimedia Communications MICS Layer • The MICS layer is responsible for integrating different types of related communication media, preserving the timing relationships among the elements of the integrated media, and providing the control operations required by the supported applications. • They use essentially the quality of services specified by the user to precisely tailor the behavior of the communication subsystem to the requirements of the user application. E0262 - Multimedia Communications Application layer • The Application layer of the proposed model provides the set of user interaction functionalities required to handle different types of user defined objects. • The interaction of the user with the system comes usually in the form of queries to distributed multimedia database, various editing commands and animation operations. • This layer is characterized by a coarse level of synchronization which has direct implications process scheduling and object manipulation. E0262 - Multimedia Communications on Network layer The network layer protocols are required to provide effective support for high quality video and audio streams. It also is required to handle interactive broadband services and multitasking. E0262 - Multimedia Communications INTERNET E0262 - Multimedia Communications The Internet is an enormous global network of computers. Often called a network of networks it integrates thousands of dissimilar computer networks worldwide through the use of technical standards that enable all types of systems to interoperate • Exchange electronic mail, or e-mail, with any other user at any location participate in offline . • discussions via e-mail with large groups of individuals interested in particular topics, using ``mailing lists" and ``News Groups" •Participate in online (i.e., real-time, or current) discussions with large groups of individuals using the ``Internet Relay Chat" function •Log on to remote computer sites worldwide using the Telnet function •Download files from remote sites and users and upload files to remote sites and users. E0262 - Multimedia Communications Connection to Internet E0262 - Multimedia Communications How does the Internet work? The first thing your browser has to do is to establish a network connection to the machine where the document lives. To do that, it first has to find the network location of the host www.iisc.ernet.in (host is short for host machine or network host'; www.iisc.ernet.in is a typical hostname). The corresponding location is actually a number called an IP address To do this, your browser queries a program called a name server. The name server may live on your machine, but it's more likely to run on a service machine . When you sign up with an ISP (Internet Service Provider), part of your setup procedure will almost certainly involve telling your Internet software the IP address of a name server on the ISP's network. E0262 - Multimedia Communications The name servers on different machines talk to each other, exchanging and keeping up to date all the information needed to resolve hostnames (map them to IP addresses). Your nameserver may query three or four different sites across the network in the process of resolving www.iisc.ernet.in, but this usually happens very quickly (as in less than a second). The nameserver will tell your browser that www.iisc.ernet.in's IP address is 15.19.25.81(say); knowing this, your machine will be able to exchange bits with www.iisc.ernet.in directly. E0262 - Multimedia Communications The Domain Name System The whole network of programs and databases that cooperates to translate hostnames to IP addresses is called DNS (Domain Name System). When you see references to a DNS server, that means what we just called a nameserver. Internet hostnames are composed of parts separated by dots. A domain is a collection of machines that share a common name suffix. Domains can live inside other domains. For example, the machine www.iisc.ernet.in lives in the .iisc.ernet.in subsubdomain in the .ernet.in subdomain of the .in domain. E0262 - Multimedia Communications Each domain is defined by an authoritative name server that knows the IP addresses of the other machines in the domain. The authoritative (or primary') name server may have backups in case it goes down; if you see references to a secondary name server or (secondary DNS') it's talking about one of those. These secondaries typically refresh their information from their primaries every few hours, so a change made to the hostname-to-IP mapping on the primary will automatically be propagated. E0262 - Multimedia Communications How to get connected to Internet Gateway Access Gateway Access is also known as Level-One connection. It is the access to the Internet from a network, which is not on the Internet. The gateway allows the two different types of networks to ``talk" to each other. But the users of the Gateway Internet have limited access to the Internet. They might not be able to use all the tools available on Internet. The local Internet Service Provider (ISP) normally defines this limitation. Good example of network with Level One connectivity within India is that of VSNL (Videsh Sanchar Nigam Limited). All access to Internet from India are through VSNL gateway. E0262 - Multimedia Communications Dial-up Connection Dial-up' connection is also known as Level Two connection. This provides connection to Internet through a dial-up terminal connection. The computer, which provides Internet access is known as ``Host'' and the computer that receives the access, is ``Client'' or ``Terminal''. The client computer uses modem to access a ``host" and acts as if it is a terminal directly connected to that host. So this type of connection is also known as ``Remote Modem Access'' connection. And the host to which the client gets connected is actually connected to the Internet by a full time connection. In dial-up connection to Internet, Host carries all the command that are typed on a client machine and forward them to Internet. It also receives the data or information from the Internet on behalf of the ``Client'' and passes it to them. The client computer acts as a ``dumb'' terminal connected to remote host. E0262 - Multimedia Communications This type of connection can further be divided into two categories. Shell Connection In this type of Internet Connection, the user will get only textual matter of a Web Page. This connection does not support Graphics display. However the user will be able to surf the Internet, do FTP, receive mail. Shell Accounts were the only type of Internet access available for many years before the Internet entered in to the world of graphics and became more users friendly. E0262 - Multimedia Communications TCP/IP Connection Today's graphical World Wide Web browsers provide easier access with multimedia sound and pictures. The major difference between Shell and TCP/IP account is that, Shell account can only display text and does not support graphics display, whereas TCP/IP can display both. Hence it is more popular Internet connection. Shell accounts are slowly phasing out from the Internet scenario. E0262 - Multimedia Communications To access any of these dial-up accounts you need the followings; Computer Modem Telephone Connection Shell or TCP/IP account from the ISP Internet client software such as Internet browser. E0262 - Multimedia Communications Multimedia Communications High-Density File Transfers Graphics File Transfers Audio File Transfers Video File Transfers Audio Communication Computer-Based Telephony Computer-Based Audio Conferencing Streaming Audio Video Communication Video Conferencing Streaming Video E0262 - Multimedia Communications T E0262 - Multimedia Communications and is based on a signalling network. E0262 - Multimedia Communications E0262 - Multimedia Communications Therefore, the N-plane will include system management functionality, and the M-plane will include scheduling, buffer management, routing (when applicable), admission control and flow control. The D-plane will contain objects modeling multimedia devices, the C-plane binding functionality, and the U-plane transport of user information within the CPE. E0262 - Multimedia Communications