Internet QOS by huanghengdong

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									Internet QoS

By: Öner Tekin - Mustafa Güler
      Outline
           Introduction
           Need for QoS
           Service Models and Mechanisms for QoS
             Integrated Services and RSVP
             Differentiated Services
             MPLS
             Traffic Engineering and Constraint Based Routing

           Comparison of Router and ATM Networks
           An End-to-End Network
           Summary
2001, Jan                  Internet QoS, Ö.Tekin & M.Güler
           Introduction
           Need for QoS
           Service Models and Mechanisms for QoS
             Integrated Services and RSVP
             Differentiated Services
             MPLS
             Traffic Engineering and Constraint Based Routing

           Comparison of Router and ATM Networks
           An End-to-End Network
           Summary
2001, Jan                  Internet QoS, Ö.Tekin & M.Güler
      Introduction



           Availability - Ideally, %100 of the time
           Throughput - Effective data transfer rate
           Packet Loss - Queue overflows at routers
           Delay - Source-to-destination time
           Jitter - Delay variation

2001, Jan                  Internet QoS, Ö.Tekin & M.Güler
      QoS Enabling a Network
      Goals
             Improve  network service perceived by applications
             Give control the network administrator over network
              resource usage
      If there were infinite network resources, QoS
       would not be necessary
             but - there are congestion points
             QoS is about deciding what traffic gets access to
              resources at these points
2001, Jan                  Internet QoS, Ö.Tekin & M.Güler
           Introduction
           Need for QoS
           Service Models and Mechanisms for QoS
             Integrated Services and RSVP
             Differentiated Services
             MPLS
             Traffic Engineering and Constraint Based Routing

           Comparison of Router and ATM Networks
           An End-to-End Network
           Summary
2001, Jan                  Internet QoS, Ö.Tekin & M.Güler
      Application Requirements




2001, Jan      Internet QoS, Ö.Tekin & M.Güler
           Introduction
           Need for QoS
           Service Models and Mechanisms for QoS
             Integrated Services and RSVP
             Differentiated Services
             MPLS
             Traffic Engineering and Constraint Based Routing

           Comparison of Router and ATM Networks
           An End-to-End Network
           Summary
2001, Jan                  Internet QoS, Ö.Tekin & M.Güler
      QoS Enabled Internet Structure




2001, Jan       Internet QoS, Ö.Tekin & M.Güler
           Introduction
           Need for QoS
           Service Models and Mechanisms for QoS
             Integrated Services and RSVP
             Differentiated Services
             MPLS
             Traffic Engineering and Constraint Based Routing

           Comparison of Router and ATM Networks
           An End-to-End Network
           Summary
2001, Jan                  Internet QoS, Ö.Tekin & M.Güler
      Integrated Services
           Charecterized by resource reservation.
           In addition to Best Effort Service, proposes:
               Guaranteed Service - fixed delay bound
               Predictive Service - probabilistic delay bound
           Implemented by four components:
               Signalling Protocol(e.g. RSVP)
               Admission Control Routine
               Classifier
               Packet Scheduler
2001, Jan                     Internet QoS, Ö.Tekin & M.Güler
      RSVP Signaling

                                          (2) PATH
             (1) PATH                                                       (3) PATH



                                      RSVP Cloud
    sender              router                                     router              receiver


             (6) RESV                                                        (4) RESV
                                            (5) RESV



2001, Jan                        Internet QoS, Ö.Tekin & M.Güler
      Problems with IntServ.

           The amount of the state information
            increases with the number of flows.
           The requirement on routers is high.
           Ubiquitous deployment is required for
            Guarenteed Service.



2001, Jan               Internet QoS, Ö.Tekin & M.Güler
           Introduction
           Need for QoS
           Service Models and Mechanisms for QoS
             Integrated Services and RSVP
             Differentiated Services
             MPLS
             Traffic Engineering and Constraint Based Routing

           Comparison of Router and ATM Networks
           An End-to-End Network
           Summary
2001, Jan                  Internet QoS, Ö.Tekin & M.Güler
      Differentiated Services
           Is a relative-priority scheme
           Defines:
             the   layout of the TOS byte - DS Field,
            a   base set of packet forwarding treatments
           Customers must have a Service Level
            Agreement (SLA) with their ISPs


2001, Jan                   Internet QoS, Ö.Tekin & M.Güler
      DS Field
           DS code specifies the PHB of packet

                           DSCP                   CU




                VER HLEN    TOS               TLEN ...          DATA

                              IP Packet


            P    DA   SA T/L                  DATA FIELD               CRC
                           Ethernet Frame
2001, Jan                     Internet QoS, Ö.Tekin & M.Güler
      Standard Services of DiffServ
           Using the classification, policing, shaping
            and scheduling mechanisms, two service
            seen below have been standardized:
             Expedited   Forwarding PHB for applications
              requiring low delay and low jitter service;
             Assured   Forwarding PHB for applications
              requiring better reliability than Best Effort
              Service

2001, Jan                 Internet QoS, Ö.Tekin & M.Güler
      Assured Forwarding PHB
           Intended for customers that need reliable
            services from their ISPs
           Implemented as follows:
             Classification              and policing are done
             All       packets are put into an Assured Queue(AQ)
             AQ    is managed by a queue management
                scheme called RED* with In and Out (RIO)
      (*) RED: Random Early Discard


2001, Jan                             Internet QoS, Ö.Tekin & M.Güler
      Expedited Forwarding PHB
           Provides low-delay and low-jitter for
            customers that generate fixed peak-bit rate
            traffic
           Customers are responsible for not exceeding
            peak rate
           Suitable for Internet Telephony, Video
            Conferencing and Virtual Private Networks

2001, Jan                Internet QoS, Ö.Tekin & M.Güler
      Expedited Forwarding PHB
           Implemented as follows:
             Customer   decides which application uses EF
              PHB
             Leaf Routers does MF classifications and shape
              the traffic
             DS fields are set
             ISP routers police the traffic
             All EF packets enter a Premium Queue(PQ)


2001, Jan                 Internet QoS, Ö.Tekin & M.Güler
      Service Allocation
       How to mark the DS fields at customer side
       Which DS codepoint to use
            –  Central Controller: Bandwidth Broker
             – OS or applications

           Who marks the packets
            –  Hosts
             – Routers



2001, Jan                 Internet QoS, Ö.Tekin & M.Güler
      Service Delivering
           Ingress routers
               Classification, policing and shaping
           Interior routers
               Behavior Aggregate (BA) classification
           Egress routers
               (Optionally) policing and re-shaping
           All routers
               queueing and scheduling based on DS field
               P-Queue for premium traffic, high priority
               A-Queue for assured and best effort traffic
                    RED with In and Out (RIO)
                    may be further divided into Gold, Silver, Bronze and Best Effort
                     queues, with rate-based scheduling

2001, Jan                          Internet QoS, Ö.Tekin & M.Güler
      The Delivery Process of AF PHB
      with a static SLA

                BB
       1
                  2                                                             9
                           5        6              7                8
            3         4

    Host S LR1            ER1        BR1       Core Router   BR2   ER2         Host D

                CN1                                                      CN2
                                                ISP1



2001, Jan                       Internet QoS, Ö.Tekin & M.Güler
      The Delivery Process of EF PHB
      with a dynamic SLA

                  CN1-BB                                ISP1-BB                       CN2-BB
                   2                   3                                 4
       1                                                           6
                             7                  6                                 5
                   7                                    14                   15             16
            8,9                  12        13
                        11
            10
    Host S LR1               ER1           BR1       Core Router   BR2       ER2            Host D

                  CN1                                                                 CN2
                                                      ISP1



2001, Jan                             Internet QoS, Ö.Tekin & M.Güler
           Introduction
           Need for QoS
           Service Models and Mechanisms for QoS
             Integrated Services and RSVP
             Differentiated Services
             MPLS
             Traffic Engineering and Constraint Based Routing

           Comparison of Router and ATM Networks
           An End-to-End Network
           Summary
2001, Jan                  Internet QoS, Ö.Tekin & M.Güler
      MPLS
           An advanced forwarding scheme
               evolves from Tag Switching, Layer 2.5
           Provide an efficient tunneling mechanism
               efficient in terms of header overhead
           Good for Traffic Engineering




2001, Jan                       Internet QoS, Ö.Tekin & M.Güler
      MPLS
           Header
               20-bit label, 3-bit COS, 1-bit stack, 8-bit TTL
               map the DS field to label + the COS field
           Binding
               Address prefix or flow or multicast group
           Label Switched Path (LSP) setup
               Label Distribution Protocol (LDP) or RSVP or Piggybacking
               Hop-by-hop or Explicit Route (ER)
           A LSP is very similar to an ATM VC
               LSP is unidirectional

2001, Jan                        Internet QoS, Ö.Tekin & M.Güler
           Introduction
           Need for QoS
           Service Models and Mechanisms for QoS
             Integrated Services and RSVP
             Differentiated Services
             MPLS
             Traffic Engineering and Constraint Based Routing

           Comparison of Router and ATM Networks
           An End-to-End Network
           Summary
2001, Jan                  Internet QoS, Ö.Tekin & M.Güler
      Traffic Engineering (TE)
       the process of planning how traffic flows
        through one’s networks
       Goal - to avoid congestion
       How - load balancing
       TE and DiffServ are complementary
             TrafficEngineering: avoid congestion
             Diffserv: when there is congestion, how to
              degrade performance in a differentiated manner

2001, Jan                Internet QoS, Ö.Tekin & M.Güler
      Constraint Based Routing

           Goals:
               to select routes that can meet certain QoS requirement
               to increase the utilization of the network

           Problems:
               increased communication and computation overhead
               increased routing table size
               longer paths may consume more resources
               potential routing instability
2001, Jan                     Internet QoS, Ö.Tekin & M.Güler
      QoS in the TCP/IP Stack

            Application Layer
                                                  Integrated Service/RSVP
            Transport Layer
                                                   Differentiated Services
                                                 Constraint Based Routing
             Network Layer
                                                              MPLS

               Link Layer




2001, Jan                   Internet QoS, Ö.Tekin & M.Güler
           Introduction
           Need for QoS
           Service Models and Mechanisms for QoS
             Integrated Services and RSVP
             Differentiated Services
             MPLS
             Traffic Engineering and Constraint Based Routing

           Comparison of Router and ATM Networks
           An End-to-End Network
           Summary
2001, Jan                  Internet QoS, Ö.Tekin & M.Güler
      ATM vs. Diffserv+MPLS
           Advantages of ATM Networks:
             ATM networks are currently faster in data forwarding.
             Per-PVC traffic statistics are available.
             QoS and some sort of Traffic Engineering are provided.

           Disadvantages of ATM Networks:
             ATM cell header overhead is large.
             Routers must be used at the boundary of the network.
             Connection-oriented approaches are less resilient in
              failure modes than connection-less approaches.

2001, Jan                  Internet QoS, Ö.Tekin & M.Güler
           Introduction
           Need for QoS
           Service Models and Mechanisms for QoS
             Integrated Services and RSVP
             Differentiated Services
             MPLS
             Traffic Engineering and Constraint Based Routing

           Comparison of Router and ATM Networks
           An End-to-End Network
           Summary
2001, Jan                  Internet QoS, Ö.Tekin & M.Güler
      An End-to-End Network
     1. PATH message arrives at DSBM switch          6. Diffserv ingress router checks policy
                                                        regarding usage of the SLA
     2. DSBM applies sender policy
        check against directory                     7.   Request approved, PATH propagated
     3. Sender approved, PATH forwarded to next          transparently through Diffserv network,
        RSVP hop (router)                                arrives at ATM network ingress router
     4. PATH forwarded RSVP hop to RSVP             8.   ATM ingress router forwards PATH to
        hop in routed network                            receiving host
     5. PATH forwarded to Diffserv ingress router
                                             Directory




                Switched                                Large Routed           ATM
                                Small Routed                                  Network
                Network                                Network(Diffserv)
                                  Network

2001, Jan                         Internet QoS, Ö.Tekin & M.Güler
      An End-to-End Network (Cont’d)
     9. RESV message reaches ingress router      13. Request approved, RESV subjected to hop by
        to ATM network                               hop admission control in routed RSVP network
    10. Admission approved, ATM VC created       14. RESV forwarded to DSBM for resource
                                                     check in 802.1 network
    11. Admitted RESV is forwarded to
        ingress router to diffserv network       15. DSBM verifies resource availability,
                                                     forwards RESV to sender
    12. Router checks resource availability
        per SLA

             Directory




                Switched        Small Routed           Large Routed         ATM
                Network           Network             Network(Diffserv)    Network

2001, Jan                         Internet QoS, Ö.Tekin & M.Güler
           Introduction
           Need for QoS
           Service Models and Mechanisms for QoS
             Integrated Services and RSVP
             Differentiated Services
             MPLS
             Traffic Engineering and Constraint Based Routing

           Comparison of Router and ATM Networks
           An End-to-End Network
           Summary
2001, Jan                  Internet QoS, Ö.Tekin & M.Güler
      Summary
       Today’s Internet based on Best Effort Serv.
       IntServ: Guaranteed and Predictive Services
       DiffServ+RSVP : SLAs, BB, DS Field
       MPLS: Label, COS, LSP
       Traffic Engineering using Constrain Based
        Routing
       ATM or DiffServ+MPLS ?


2001, Jan           Internet QoS, Ö.Tekin & M.Güler
      Thank You!

       Contacts
      •You can reach our presentation and some documents about
      QoS from the web site seen below:
                   http://www.geocities.com/ccn_qos
      •For any comment or question about Internet QoS please feel
      free to contact us:
                          onertek@yahoo.com
                        mustafaguler@visto.com

2001, Jan                Internet QoS, Ö.Tekin & M.Güler

								
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