MPLS can be combined with IntServ and DiffServ to support QoS. allow datagram and virtual circuit to be coexisted in an IP network. Originally designed for IP over ATM A short (fixed length) label is encoded for the packet header for packet forwarding Allow Label switched path (LSP) to be setup (explicit routing). ġ2 Multi-Protocol Label Switching (MPLS): Problems with DiffServ: end-to-end service guaranteed is hard to maintain. Forwarding class is encoded in the packet header. Signaling protocol: RSVP IntServ is a reservation based approach Main problem: Router complexity (scalability) ĭefine per-hop behavior instead of end-to-end service model Support a small number of forwarding classes at each router. Trying to match the user demand by providing per flow QoS guarantees. Where is the balance? A guess: Some form of QoS support will be there, per flow QoS guarantee may or may not ever be deployed. 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 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
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