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Internet QoS

Internet QoS

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Internet QoS

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  1. Internet QoS • Differentiated Services (DiffServ) • Multiprotocol Label Switching (MPLS) Reference Zheng Wang, Internet QoS, Architectures and Mechanisms for QoS, ISBN 1-55860-608-4, 2001. Network Architecture and Design

  2. DiffServ - Overview • Integrated services provides QoS; but • Problem of scalability • The routers have to maintain state on every flow passing through them. • Heterogeneous networks may not be able to provide particular QoS controls or even RSVP. • Differentiated service (DiffServ) aims to offer QoS to aggregated flows. Network Architecture and Design

  3. DiffServ - Overview • DiffServ defines Differentiated Service Code Point (DSCP) in • IPv4 TOS field, • IPv6 Traffic Class field. • All traffic in one DSCP is treated the same. • Per hop behaviour (PHB) is determined by DSCP of packet. • Service Level Agreements concern aggregate traffic not individual flows. Network Architecture and Design

  4. DiffServ - Operation • Per Hop Behaviour (PHB) • Assured Forwarding • provides low loss probability for compliant traffic. Guarantees ordering of packets in a given AF class. • Expedited Forwarding: • near constant delay/throughput • Virtual Wire aggregate Network Architecture and Design

  5. DiffServ - Operation • Resource allocation • BB: Bandwidth Broker: global view of resources • Static provisioning: may give poor service to flows • Signalling: use of RSVP to allocate resources Network Architecture and Design

  6. DiffServ - Operation Network Architecture and Design

  7. DiffServ - Operation meter Shaper/dropper To interiornodes classifier marker Input Network Architecture and Design

  8. DiffServ - Operation • Classification: marks packets according to classification rules to be specified • Metering: checks whether the traffic falls within the negotiated profile • Marking: marks traffic that falls within profile • Conditioning: delays and then forwards, discards, or remarks other traffic Network Architecture and Design

  9. DiffServ - Operation • 2-Bit Differentiated Services Architecture for the Internet • Premium service • Premium service levels are specified as a desired peak bit rate for a specific flow • Assured service • Best-effort service Network Architecture and Design

  10. DiffServ - Operation • In-profile traffic is marked: • A-bit is set in every packet • Out-of-profile (excess) traffic is unmarked • A-bit is cleared (if it was previously set) in every packet; this traffic treated as best-effort r bps user profile (token bucket) b bits assured traffic in-profile traffic set A-bit metering out-of-profile traffic clear A-bit Network Architecture and Design

  11. DiffServ - Operation • In-profile traffic marked: • Set P-bit in each packet • Out-of-profile traffic is delayed, and when buffer overflows it is dropped r bps user profile (token bucket) b bits premium traffic Metering/ Shaper/ Set P-bit in-profile traffic out-of-profile traffic (delayed and dropped) Network Architecture and Design

  12. IntServ Vs DiffServ Network Architecture and Design

  13. IntServ Vs DiffServ • IntServ provides fine grain control and handles dynamic allocation of resources to flows • DiffServ provides course grain control of flows through their aggregates • The two together can be combined to provide scalable end to end Integrated service, using a DiffServ region as a single element • Controlled Load can be implemented over Assured Forwarding PHB • Guaranteed can be implemented over Expedited Forwarding PHB Network Architecture and Design

  14. IntServ & DiffServ Network Architecture and Design

  15. Internet QoS • Differentiated Services (DiffServ) • Multiprotocol Label Switching (MPLS) Network Architecture and Design

  16. Current Situation • Geographically dispersed enterprise networks need to be connected for transparent and secure private IP interconnection. • Full (n^2) mesh of virtual-circuits needs for desired guaranteed performance, or partial meshing for low cost. • IP uses 64K size packets whereas ATM uses 53 byte-cells. • IP and circuit-switching (e.g., ATM) technologies use different addressing scheme. Network Architecture and Design

  17. MPLS Overview • MPLS (Multiprotocol Label Switching) • Improves the forwarding speed of a router. • Introduces new capabilities for large IP networks • Introduction of many of the qualities and attributes of switched networks to IP networks • Integrates Layers 2 and 3. Network Architecture and Design

  18. MPLS Operation • MPLS Components • Edge-LSR: Edge-Label Switching Router • Assigns a label in an incoming IP packet • Removes the label of an incoming IP packet • LSP: Label Switching Path • The path that a packet follows in an MPLS network • LSR: Label Switching Router • Makes forwarding decisions based SOLELY on the contents of the label (basic advantage) • Strips off the existing label and applies a new label which tells the next hop how to forward the packet Network Architecture and Design

  19. IP MPLS – Traditional IP Routing 47.1 1 IP 2 IP 1 3 2 IP 1 47.2 47.3 3 2 Network Architecture and Design

  20. IP IP MPLS – MPLS Routing 1 47.1 3 3 2 1 1 2 47.3 3 47.2 2 Network Architecture and Design

  21. MPLS - Example 1a. Existing routing protocols (e.g. OSPF, ISIS) establish reachability to destination networks 4. Label Edge Router at egress removes label and delivers packet 1b. Label Distribution Protocol (LDP) establishes label to destination network mappings. 3. Label Switches switch label packets using label swapping 2. Ingress Label Edge Router receives packet, performs Layer 3 value-added services, and “label” packets Network Architecture and Design

  22. MPLS Label Format • IP packet is encapsulated in MPLS header and sent down LSP • IP packet is restored at end of LSP by egress router • TTL is adjusted also … IP Packet 32-bit MPLS Header Network Architecture and Design

  23. MPLS Label format • Label • Class of service • Stacking bit • Time to live • Decrement at each LSR, or • Pass through unchanged Label CoS S TTL Network Architecture and Design

  24. Label Distribution Protocols • CR-LDP • RSVP-TE Network Architecture and Design

  25. MPLS • Fast forwarding speed • Traffic Engineering • constraint-based routing • explicit routing • ability to compute a path at the source • ability to reserve network resources and to modify link attributes • Voice/Video on IP • delay variation + QoS constraints • Virtual Private Networks • controllable tunneling mechanism • equivalent to a Frame Relay or ATM VC Network Architecture and Design

  26. MPLS Benefits Network Architecture and Design 14

  27. Second Intermediate Report • Integrated and Differentiated Services • I. Stergiou • Group Communication, MBONE, MPLS • A. Sgora • Deadline: 11/02/03 Network Architecture and Design

  28. Second Intermediate Report • Structure • Overview of examined technology • Focus on open research points • Related to open points works - State of the art behind open points • Your own interests - Ideas • Conclusions • References Network Architecture and Design

  29. Second Intermediate Report • Report (soft and hard copy) • A related presentation (about twenty minutes). Network Architecture and Design

  30. End of Fourth Lecture Network Architecture and Design