![]() What is the main problem? Complexity and scalability of QoS mechanisms Which is cheaper: higher network speed or network with QoS support. Traffic monitoring: find problems as early as possible Traffic reshaping (at merge and fork points) ĩ QoS in the Internet: Do we really need it?Īlternative: buy excessive bandwidth Everything is simple in the Internet without QoS, everything seems to be much harder in the Internet with QoS support. Traffic policing Īt routers: classification and scheduling: FCFS won't work, need more advanced packet scheduling scheme (Fair Queuing) Routing algorithm need to improve: find a path that satisfies QoS constraints (QoS/policy/constraint based routing). Traffic specification/desired QoS/supported QoS At network edge: Signaling and admission control Packet classification/marking Traffic shaping Packet classification/marking and traffic shaping is also called traffic conditioning. deterministic QoS guarantees īetween the network and its clients: Traffic contract. VoIP: bounded delay VPN: bounded bandwidth Video conferencing: bounded delay and bounded loss rate Common QoS parameters: delay/delay variation (jitter) Bandwidth error rate Ħ What is QoS(Cont.) Per flow QoS guarantees and aggregate QoS guarantees Statistical QoS guarantees. ĥ What is QoS(Cont.) Applications that need QoS Common QoS parameters: Adding service differentiation is non-trivial. Existing IP networks only support best effort service. ![]() only a small portion of high priority packets. end-to-end service guarantees may be achieved by provisioning. Guaranteed delay (VoIP), Guaranteed bandwidth (VPN) Relaxed definition: Service differentiation: different packets is treated differently. Ĥ What is QoS User point of view: Relaxed definition:Īssurance of end-to-end service. What does it take for the Internet to support QoS? Existing Internet QoS architectures: Integrated services, differentiated services, and MPLS overview. The COPS role for Dynamic DiffServ resource allocation Definition of the COPS Interfaces IP Telephony : A COPS Based QoS model Implementation Testbed conclusion ģ What is QoS What is quality of service? Veltri IEEE Networks, March/April 2002 R 賈 立 R 黃文彬 R 陳育成 R 陳奕安 #Diffserv sip definition codeA six-bit field, known as the Differentiated Services Code Point (DSCP), in the Internet Protocol ( IP) header specifies the per hop behavior for a given flow of packets.ĭifferentiated Services and the Class of Service approach provide a way to control traffic that is both more flexible and more scalability than the Quality of Service approach.Presentation on theme: "QoS control by means of COPS to Support SIP-based applications"- Presentation transcript:ġ QoS control by means of COPS to Support SIP-based applications ![]() For a given set of packet travel rules, a packet is given one of 64 possible forwarding behaviors - known as per hop behaviors (PHBs). An analogy is made to travel services, in which a person can choose among different modes of travel - train, bus, airplane - degree of comfort, the number of stops on the route, standby status, the time of day or period of year for the trip, and so forth. #Diffserv sip definition how toUnlike the earlier mechanisms of 802.1p tagging and Type of Service (ToS), Differentiated Services avoids simple priority tagging and depends on more complex policy or rule statements to determine how to forward a given network packet. Differentiated Services is the most advanced method for managing traffic in terms of what is called Class of Service ( CoS). Differentiated Services (DiffServ, or DS) is a protocol for specifying and controlling network traffic by class so that certain types of traffic get precedence - for example, voice traffic, which requires a relatively uninterrupted flow of data, might get precedence over other kinds of traffic. ![]()
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