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Integrated Services

Integrated Services

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Integrated Services

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  1. Integrated Services

  2. Introduction • Integrated services is defined as the coexistence of the best-effort datagram delivery in the Internet with additional QoS delivery classes • The level of QoS provided by these enhanced QoS classes is programmable on a per-flow basis • End-to-end QoS commitment for the data flow is achieved through resource reservation

  3. IntServ Architecture • Main elements: Extended service model and reference Implementation framework • IntServ service models targeted for real-time traffic: guaranteed service and predictive service • Service features: • Resource Reservation: Routers need to maintain per-flow state information • Common Infrastructure: Same infrastructure for both QoS-aware and best-effort traffic • Unified Protocol Stack: Interoperability between IntServ-capable an IntServ-incapable Internet systems • Reference Implementation framework is composed of: packet scheduler, admission control routine, classifier, and the reservation set-up protocol

  4. Flow and Service Model • Flow: A distinguishable stream of related datagrams that results from a single user activity and requires the same QoS • A service model defines a set of service request that the network is committed to deliver. The service commitments can be made to the individual flows or to classes of flows

  5. IntServ Service Model • QoS Requirements • Packet delay is the key metric; • Real-time and elastic applications • Resource Sharing Requirements • Resource are negotiated on a per-flow basis but are allocated on an aggregated basis • Packet Dropping • Packet are drops discriminately • Reservation Model • Static and fixed, range, two-pass approach

  6. Traffic Management • Packet Scheduling • Round-robin, WFQ, priority queue • Packet Dropping • Routers drop packets when their buffer is full • Packet Classification • Classification based on QoS needs • Admission Control • Acceptance/rejection of a request based on the resource availability and the required QoS

  7. Resource Reservation Protocol (RSVP) • RSVP is an IP reservation protocol that enables the senders, receivers, and routers to communicate with each other to set up the necessary router states to facilitate the services between the end points • The reservations and route set-ups applies only to packets of a particular session • RSVP identifies a particular session by the combination of destination address, transport-layer protocol type, and destination port number • Drawbacks: scalability and implementation issues

  8. RSVP Design Goals • Accommodate heterogeneous receivers • Adapt to dynamic multicast group • Match network resources to applications • Channel switching capability • Adapt to changes in route • Control protocol overhead • Modular design

  9. RSVP Design Principles • Receiver initiated reservation • Separating reservations from packet filtering • Providing different reservation styles • Maintaining “soft state” in the network • Protocol overhead control • Modularity

  10. RSVP Operations • Uses resource reservation and signaling protocol on a per flow basis (RSVP) • Scalability problem and implementation overhead PATH (1) (3) (2) (5) (6) (4) RESV