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Prof Pallapa Venkataram, Electrical Communication Engineering, Indian Institute of Science, Bangalore – 560012, India. QoS Management. Quality of Service. Provide guarantees on the ability of a network to deliver predictable results.
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Prof Pallapa Venkataram, Electrical Communication Engineering, Indian Institute of Science, Bangalore – 560012, India QoS Management
Quality of Service Provide guarantees on the ability of a network to deliver predictable results. Elements of network performance within the scope of QoS often include availability (uptime), bandwidth (throughput), latency (delay), and error rate. Multimedia Traffic Parameters peak arrival rate of the multimedia data when the source is in the active state(peak rate); average data unit arrival rate; burstiness: ratio between the peak data rate and the average data rate; average duration of the active state.
Multimedia Traffic Characterization A requirement for real-time transmission of continuous media information (audio and video); Substantial volumes of data to be exchanged due to the encoding of continuous media information; Distribution-oriented applications; and Long-range dependency (or similarity)
Quality of Service requirements throughput transit delay delay variation error rate multicasting and broadcasting capabilities document caching capabilities The QoS is the collective eect of service performances which determine the degree of satisfaction of a user of the service..
QoS Co-ordination QoS translation captures application QoS requirements and configures system and network QoS specification correspondingly. QoS control mechanisms provide real-time traffic control of flows based on requested levels of QoS established during the connection. The basic QoS control mechanisms include traffic shaping, scheduling and flow control. QoS management mechanisms ensure the contracted QoS is sustained, which operate on a slower time scale and implement the QoS monitoring, maintenance, renegotiation and scalability.
QoS Co-ordination Allow explicit specification of QoS parameters when creating a session for multimedia transmission; Translate application QoS parameters into network layer QoS parameters; Negotiate QoS demands on the application's behaviours; reserve the necessary resources at communication systems if negotiation is successful; Perform dynamic QoS management on existing sessions; Employ admission control to check if enough resources are available to satisfy a new application; and Regulate and monitor all sessions to protect network resources from misbehaving users.
Generalized QoS Framework Access Provider Service Level Agreement Service Provider Service Level Specification Network Provider Resource Provider Autonomous Systems
QoS Principles for MM Data Traffic Governing integration principle states that QoS must be configurable, predictable and maintainable over all architectural layers to meet end-to-end QoS. separation principle states that media transfer, control and management are functionally distinct architectural activities. transparency principle states that applications should be shielded from the complexity of underlying QoS specification and QoS management. multiple timescales principle guides the division of functionality between architectural modules and pertains to the modeling of control and management mechanisms. performance principle subsumes a number of widely agreed rules for the implementation of QoS-driven communications systems
QoS Provision Mechanisms Components QoS Mapping Automatic translation between representations of QoS at different system levels
QoS Provision Mechanisms Admission Testing It is responsible for comparing the resource requirement arising from the requested QoS against the available resources in the system. Resource reservation protocols These protocols arrange for the allocation of suitable end-system and network resources according to the user QoS specication.
QoS Control Mechanisms Flow shaping regulates flows based on user supplied flow performance specifications Flow scheduling manages the forwarding of flows in the end-system and network in an integrated manner Flow policing: dual monitoring: observes whether QoS contracted by a provider is being maintained whereas the former observes whether the QoS contracted by a user is being adhered to Flow control which includes both open-loop and closed loop schemes Flow synchronisation which is required to control the event ordering and precise timings of multimedia interaction
QoS Management Mechanisms QoS monitoring allows each level of the system to track the ongoing QoS levels achieved by the lower layer QoS maintenance compares the monitored QoS against the expected performance and then exerts tuning operations on resource modules to sustain the delivered QoS. QoS degradation issues a QoS indication to the user when it determines that the lower layers have failed to maintain the QoS of the flow QoS availability allows the application to specify the interval over which one or more QoS parameters QoS scalability comprises QoS filtering and QoS adaptation mechanisms.
QoS System Layers protocols - transport, network network middleware operating system - scheduling, resource management, real-time support distributed platforms - CPU, memory/buyers, devices application
QoS Specification QoS specification encompasses requirements for: performance - expected performance characteristics are needed to establish resource commitments, synchronization - characterizes the degree of synchronization required between related services, events, or information flows, level of service - species the degree of resource commitment required to maintain performance guarantees, cost of service - the price a user is willing to incur to obtain a level of service, QoS management - the degree of QoS adaptation that can be tolerated and scaling actions to be taken in the event the contracted QoS cannot be met.
QoS Parameters Classification of multimedia QoS in communication layers.
QoS Parameters An example of QoS parameters at different levels specified
Application Level QoS Parameters End-to-end level Unicast or multicast; Dedicated to the transfer of a single Flow of application data; Able to offer a specific QoS; To support multimedia applications, the following six network criteria are critical: through-put; transit delay; delay variation; error rate; multicasting; and broadcasting capabilities document caching capabilities.
Transport Level QoS In addition to QoS parameters, an application must specify four service parameters: The first one characterizes the traffic generated by the multimedia application sender; The second one designates which transport protocol to use (UDP, TCP); The third one designates the IP layer's QoS management desired by the application; The final parameter identifies the address, either unicast or multicast, of set of a destination applications.
Network Level QoS On the data path: QoS functions are applied by routers at the packet level in order to provide different levels of service. On the control path: QoS functions concern routers configuration and act to enforce the QoS provided. Three services have been defined at the IP level: GS (Guaranteed Service) is used for data flows having strong constraints in both delay and reliability; AS (Assured Service) is appropriate for responsive flows having no strong constraints in terms of delay, but requiring a minimum average bandwidth; BE (Best Effort) service offers no QoS guarantees.
Network Services Rule 1: Services are applied end-to-end, between source and destination, at all network elements in the path of the application flow. This includes the systems' device drivers, operating systems, and application interfaces. Rule 2: Services are configurable using QoS characteristics at each network element in the path of the application flow. Rule 3: Services are verifiable within the applicable network. These rules are necessary conditions for services to be meaningful within the network and to their high-priority applications.
Service Components Maintaining service state of all network elements and end systems. User and application support for network services, including a general mapping of application requirements to QoS characteristics. Defining service levels and QoS characteristics. Mechanisms to evaluate service requests, congure authorized requests in the network, and manage network resources. Rules for how services and network resources are allocated and managed are part of these mechanisms. Mechanisms for fault detection and management.
Service Components Service Mechanisms service system will evaluate service requests to determine if the network has sufficient resources to support it Fault Detection and Management When faults occur on the network, such as routing transients, hardware and software failures, the service system will have the capability to recover from faults and re-establish services to its users and applications.
Service Mechanism Components The service system gathers and maintains state for all network elements and end systems.A user makes a request for a network service. The service system evaluates the service request from the user/application, and either denies the request, accepts the request, or offers alternatives to the service level requested If the service request is accepted, the service system configures the network elements and end systems in the path of the application flow with the QoS characteristics associated with the service level. Service system manages network resources for the duration of service request, then releases the resources at the end of the request, updating the service system's state and services tables.
Network Quality of Service Architecture The QoS in the network consists of several software components, implemented on all network elements and end-systems in the path of each application flow that receives QoS from the network. The network service software components of QoS: Service system (server) software. Device drivers for specialized end-equipment. OS/APIs for end-hosts, possible including end-equipment. Sets of rules for how service requests are evaluated and managed, and how network faults are managed, will be developed and integrated into this software.
Service System Software The service system is the kernel of service request handling and support. Service system software is implemented on one or more servers in the network, and it interfaces with users/applications, network elements, and with end-systems. The service system supports all of the components: maintaining service state, user and application support, mechanisms to evaluate, configure, and manage service requests, managing network resources, and mechanisms for fault detection and management.
Device Drivers As agents for service system software in end-equipment, device drivers keep state information about its end equipment, and translate service requests into device-specific configuration characteristics. A device driver for an Magnetic Resonance Imaging keeps information about active and scheduled service requests, fault information, and the types of device-specific services that it can offer to the network. Device-specific service information can be presented by the service system to users/applications, to help them to determine which devices they want to use.
OS/APIs Operating System (OS) software or application programming interfaces (APIs) in end-systems (PCs, workstations, supercomputers, parallel systems) will provide a similar function as device drivers do for end-systems (devices), keeping state information, fault information, and service information specific to end systems. User interface function to users/applications, communicating with the pre-processor of the service system.
Modelling for QoS Management Metadata required for the management of multimedia: metadata about the representation, the structure, the content, the storage and the versions. Categories of QoS information the user the system components the multimedia documents.
QoS Modelling QoS Parameters associated with system components User's QoS Parameters
Model based QoS Management QoS Adoption Space
Policy based QoS Management Authentication, Authorization, and Accounting Policy Server Lightweight Directory Access Protocol
