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QoS ( Intserv & Diffserv)

QoS ( Intserv & Diffserv). BY ANJALI KULKARNI YI-AN CHEN. QoS. Current Internet offers best effort service only As the Internet is the ubiquitous communications infrastructure, there is a clear need for providing differentiated classes of service to network traffic. What is Intserv.

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QoS ( Intserv & Diffserv)

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  1. QoS ( Intserv & Diffserv) BY ANJALI KULKARNI YI-AN CHEN

  2. QoS • Current Internet offers best effort service only • As the Internet is the ubiquitous communications infrastructure, there is a clear need for providing differentiated classes of service to network traffic

  3. What is Intserv • Service differentiation in the Internet • Focuses on individual packet flows • Each flow requests specific levels of service from network • Levels of service quantified as a minimum service rate, or a maximum tolerable end-to-end delay or loss rate • Network grants or rejects the flow requests, based on availability of resources and the guarantees provided to other flows

  4. Interserv • Best effort service • Real time service • Controlled link sharing • Multi-entity link-sharing • Multi-protocol link-sharing • Multi-service sharing

  5. Framework of IS Model • Packet scheduler • Admission control • Classifier • Reservation setup protocol(RSVP)

  6. RSVP • Path messages • Resv messages • PathErr, PathTear, ResvErr, ResvTear, ResvConf Messages Phop, Sender template, Tspec, Adspec Reservation style, Filter specification, Rspec, Tspec

  7. Processing and Propagation of Path Messages by Network Routers • Update the path state entry • Set cleanup timer • Create and forward Path message Any change to stored path state or a change in the set of outgoing interfaces in the data forwarding path Every refresh period timeout interval

  8. RSVP

  9. RSVP Filters

  10. Factors Impeding Deployment of Intserv/RSVP • Use of per-flow state and per-flow processing raises scalability concerns for large network • The necessary policy control mechanisms have only recently become available

  11. What is Diffserv • Based on a model where traffic entering a network is classified , possibly conditioned at the boundaries of the network, and assigned to different service classes • Here, we avoid complexity and maintenance of per-flow state information in core nodes and push unavoidable complexity to the network edges

  12. What is Diffserv • Provide scalable service differentiated in the internet that can be used to permit differentiated pricing of internet service • Separate packet forwarding model from routing model

  13. Terminology • Per Hop Behavior(PHB) • DS Domain( e.g. ISP, intranet) • DS Boundary Node(Egress & Ingress) • DS Interior Node • DS Codepoint(DSCP) • DS Behavior Aggregate

  14. Terminology • Bandwidth Broker (BB) • Logical entity, can be mapped to a single or multiple physical entity • A logical entity residing in each administrative domain managing internal demands & resources according to some policy database (who can do what where and when) • Setting up & maintaining bilateral agreement with neighbor domains

  15. Terminology • SLA(SLS) & TCA(TCS) • Customer/Provider boundaries • Service Level Agreement A set of parameters and their values which together define the service offered to a traffic stream by a DS domain • Traffic Conditioning Agreement A set of parameters and their values which together specify a set of classifier rules and traffic profile

  16. SLA

  17. Logical View of Packet Classifier and Traffic Conditioner

  18. Terminology • Classifier • Traffic Profile Specifies the temporal properties of a traffic stream selected by a classifier. It provides rules for determining whether a particular packet is in-profile or out-of-profile • BA Classifier • MF Classifier

  19. Terminology • Traffic Conditioner • Meter • Marker • Shaper • Dropper • Host Marking • Router Marking

  20. Service Taxonomy • Quantitative Service • Qualitative Service • Relative Quantification Service Traffic offered at service level A will be delivered with low latency 90% of in profile traffic delivered at service level B will experience of no more than 50 msec latency Traffic with drop precedence AF12 has a higher probability of delivery than traffic with drop precedence AF13

  21. Assured Forwarding (AF) Class • As long as aggregate traffic from some sites connecting to internet does not exceed the subscribed information rate, forward packets with high probability • AF PHB group - Forwarding of IP packets in N independent AF classes. Within each class, an IP packet is assigned M different levels of drop precedence • Queuing and discard behavior

  22. Expedited Forwarding (EF) Class • Providing low loss, low latency, low jitter, assured bandwidth, end-to-end service through DS domains • EF PHB A router uses policing and shaping mechanism to ensure that the maximum arrival rate of a traffic aggregate is less than its minimum departure rate

  23. Working within a Domain

  24. Working within a Domain • Step 1 Source sends request message to first hop router • Step 2 First hop router sends request to BB, which sends back either a accept or reject • Step 3 If accept, either source or first hop router will mark DSCP and start sending packets

  25. Working within a Domain • Step 4 Edge router checks compliance with SLA and does policing. Excess packets are either discarded or marked as low priority to comply with the SLA • Step 5 Core routers will just look at DSCP and decide PHB

  26. Intra-Domain Resource Allocation Architecture

  27. Edge Router-BB Communication • BB contains the flow database containing information regarding flows requesting increased level of service . It contains ingress/egress interface, resources requested, start/finish time • BB sends the TCA to the domain’s edge routers

  28. Edge Router-BB Communication • COPS is used for this. BB’s COPS server TCA to COPS client residing at edge router • COPS client translates these commands to parameters understood by forwarding path via the Forwarding path driver(FPD)

  29. Interdomain Communication

  30. Functions of BB • Negotiation of SLAs with BBs of neighboring domains • Translation of SLAs into one or several TCAs for edge devices • Delivery of the TCAs to the edge routers of the administered domain, using one of many proposed protocols

  31. Steps in Interdomain Communication • Assumption Needs of domain 1 towards domain 3 are satisfied by a 64kb/s flow of premium traffic • Step 1 BB1 learns internally that a 64kb/s SLA is needed • Step2 BB1 requests the SLA from BB2, BB2 performs admission control

  32. Steps in Interdomain Communication • Step 3 If the request is admitted, BB2 sends a TCA derived from the SLA requested to R2( it’s administered edge router) • Step 4 BB2 responds positively to BB1. This TCA models the traffic to be transferred from domain1 via R2

  33. Steps in Interdomain Communication • Step 5 A similar TCA is sent by BB1 to it’s administered edge router R1 instructing it to allow the given traffic to flow out to domain 2 • Step 6 BB2 may request more premium resources from BB3 to aggregate the new premium traffic demand to the existing SLA between BB2 and BB3

  34. Multicasting in DS Domain • Neglected Reservation Subtree Problem (NRS) • Heterogeneous Multicasting Groups • Dynamic of Arbitrary Sender Change

  35. NRS Multicast packet replication in a DS router

  36. NRS cont.

  37. NRS cont.

  38. Heterogeneous Multicasting Groups • Participants requesting a best effort quality only should also be able to participate in a group communication which otherwise utilises a better service class • Support heterogeneous groups with different service classes in a consistent way

  39. Dynamics of Arbitrary Sender Change • A sender resource must be reserved seperately if simultaneous sending delivery trees are used

  40. Security Consideration • Theft of service • Denial of service

  41. 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

  42. Block Diagram of First Hop Router Input Functionality

  43. Markers to Implement the 2 Different Services

  44. Border Router Input Interface Profile Meters

  45. Router Output Interface for 2-bit Architecture

  46. Statically Configured Example with no BB Messages Exchanged • All allocations are statically preallocated through purely bilateral agreements between users. This negotiation is done by human repreentatives of each domain • BBs perform function to allocate profile within their local domain

  47. End-to-End Example with Static Allocation

  48. End-to-End Static Allocation eg. with no Remaining Allocation

  49. First Step in End-to-End Dynamic Allocation Example

  50. Second Step in End-to-End Dynamic Allocation Example

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