Quality of Service in IP Networks

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Quality of Service in IP Networks
Lucent Worldwide Services Knowledge Seminars
Sharing the Knowledge Behind the Network

• Presented by
• John Railsback jrailsback_at_lucent.com
• Rick Blum rickblum_at_lucent.com

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Background

• Lucent Worldwide Services is a provider of
  communications consulting, intelligent
  maintenance, and management solutions for next
  generation networks
• Seminar objectives
• Present the major factors driving QoS
• Highlight current QoS technologies and techniques
• Provide insight into the future direction of QoS
  for IP networks

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QoS Research

• Web-based industry survey conducted September
  2000
• 108 respondents
• Represent a cross-section of end-user
  organizations and network solutions providers
• Survey report available at www.lucentnps.com/surve
  ys

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QoS Definition

• Management of available bandwidth to deliver
  consistent, predictable data (packets) over an
  IP-based network in terms of
• Latency - delay that an application can tolerate
  in delivering a packet of data
• Jitter - variation in latency
• Loss - percentage of lost data
• Throughput - amount of data carried
• Availability - network uptime

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Importance of Implementing/ Improving QoS
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The IP Network Problem

• Congestion continues to plague the Internet
• Traffic expands or gt bandwidth
• Best-effort" performance dictated by the very
  design of the Internet Protocol (IP)
• Mission critical applications, e.g., IP Telephony
  and ERP, require prioritization
• Service Level Agreements (SLAs) expected
• Customer expectations increase with bandwidth

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Why QoS

• Over-provisioning bandwidth not cost effective in
  the long run
• Users will consume bandwidth as fast as produced
• Need reliable data delivery
• Mission critical applications
• ERP, SAP, Financial Market data
• High bandwidth, low latency applications
• Video and audio streaming, video conferencing,
  voice
• Provide value-added services with SLAs

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Contributing Factors to Importance of QoS
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QoS Technologies

• Reservation
• Allocates resources on a per-flow basis
• Flows include information such as transport
  protocol, source address port, destination
  address and port
• Intserv/RSVP
• Prioritization
• Traffic flows are aggregated and categorized by
  "class of service
• DiffServ and IEEE 802.1p

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Integrated Services

• Defined in RFCs 2205, 2206 - www.ietf.org/rfc.ht
  ml
• Implemented by four components
• Signaling protocol (RSVP)
• Reserves resources and establishes paths before
  transmitting data
• Admission control routine
• Determines whether a request for resources can be
  granted
• Classifier
• Places packets in specific queues based on
  classification result
• Packet scheduler
• Schedules the packet to meet its QoS requirements

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RSVP

• Signaling protocol that can operate in "native
  mode" or "encapsulated mode" within a UDP header
• Operates in tandem with either a TCP or UDP
  "flow" to reserve resources among RSVP-enabled
  routers
• Also being used to signal QoS into DiffServ and
  MPLS networks

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RSVP Request
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Differentiated Services (DiffServ)

• Defined in RFCs 2474, 2475
• Creates classes of service for traffic flows with
  different priorities
• Aggregates large numbers of individual flows at
  the edge of the network into small numbers of
  aggregated flows through the core of the network
• Flows are marked at network edge in the IPv4 ToS
  field (DS field).
• Services applied through the core

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Building Blocks of DiffServ

• Packet Classifiers
• Packets sorted into queues based on values in the
  DS (DiffServ) field
• Traffic Conditioning Policies
• Metering, Marking, Shaping and Policing based on
  DSCP and packet header data
• Forwarding/Per Hop Behaviors
• Expedited Forwarding and Assured Forwarding
• Policy Managers
• apply and communicate QoS policy

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Packet Classifiers

• DiffServ Code Point (DSCP)
• Maximum of 64 classes of service
• Replaces IP TOS field
• Packets sorted into queues based on DSCP values

Source QoS Forum
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Traffic Conditioning

• Metering
• Monitors traffic patterns against traffic
  profiles
• Marking
• DS field marks packet with specific values for
  each PHB (marked by edge routers)
• Policing
• Ingress routers drop or remark traffic that does
  not meet profiles and policies
• Shaping
• Egress routers control forwarding rate of packets
  and controls traffic flow to avoid congestion

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Per Hop Behaviors

• Assured Forwarding (AF)
• Similar to ATM nr-VBR QoS
• Four AF classes with three codepoints each
• AF classes not specifically defined regarding
  performance or priority between classes
• Non-conforming traffic marked at the edge
• RED queuing most often used.
• Better then Best Effort Delivery
• Gold, Silver, Bronze services

• Expedited Forwarding
• Guaranteed delay and jitter (similar to ATM CBR)
• Provides a Virtual Leased Line service
• Non-conforming policed on ingress and shaped on
  egress of Diffserv domain
• Manual provisioning or signaling protocols
  required for quantitative guarantees.
• Typically implemented with strict priority
  queuing

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DiffServ Code Points for Expedited Forwarding and
Assured Forwarding
Assured
Class 1
Class 2
Class 3
Class 4
Class 5
Forwarding
Low Drop
001010 (AF11)
010010 (AF21)
011010 (AF31)
100010 (AF41)
Precedence
Medium Drop
001100 (AF12)
010100 (AF22)
011100 (AF32)
100100 (AF42)
Precedence
High Drop
001110 (AF13)
010110 (AF23)
011110 (AF33)
100110 (AF43)
Precedence
Expedited
101110
Forwarding
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IEEE 802.1p

• Traffic-handling mechanism for supporting QoS in
  LANs
• Allows a classification/prioritization of
  differentiated services analogous to DiffServ
• Operates at layer 2 (MAC) layer on a switched
  Ethernet network
• Defines a field in the layer-2 header of 802
  packets that can carry one of eight priority
  values

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IEEE 802.1p

• Scope of 802.1p priority mark is limited to the
  LAN. Once packets are carried off the LAN,
  through a layer-3 device, the 802.1p priority is
  removed.
• 802.1p often defined with 802.1q
• Together, define various VLAN (virtual LAN)
  fields, as well as a priority field
• Implemented in hardware (switches and routers)

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Multi Protocol Label Switching (MPLS)

• More scalable mechanism for IP over ATM than
  classical overlay model
• Edge routers can peer with nearby MPLS nodes
• Avoids N2 scaling issues with ATM meshed networks
• Traffic Engineering - using explicit routes and
  constraint-based routing for better load
  balancing.
• As a tunneling mechanism to interconnect
  intra-VPN sites

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MPLS Network

• LSPs provide transport for
• MPLS VPNs
• Traffic Engineered Explicit Routes
• DiffServ Aggregates

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QoS Implementation Status
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Significant Barriers to Implementing QoS
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QoS Implementation Issues

• Inter-domain and Inter-Service Provider
  interoperability
• Vendor interoperability
• Limiting RSVP implementation in the core
• Use RSVP to signal QoS to DiffServ and MPLS
  network cores
• QoS support in applications
• Monitoring and measuring QoS
• Billing, accounting, pricing
• Security and authentication
• Policy management

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Biggest Challenge to Implementing QoS
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The Bottom Line

• For Internet and WANs, DiffServ and MPLS top
  candidates for aggregated traffic flows and QoS
• DiffServ from the edge through the core, or
• DiffServ at the edge, MPLS at the core
• RSVP for signaling

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The Bottom Line

• For LANs and enterprise networks, 802.1p is top
  edge QoS mechanism using RSVP for signaling
• Microsoft supports RSVP in Windows 2000
• Microsoft APIs for application based QoS
  development

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The Bottom Line

• Where do you start?
• Planning
• Match QoS Mechanism to Applications, Services,
  Desired Traffic Types, and SLAs
• Determine needed management and accounting
  platforms for measuring performance and usage
• Design
• Determine required hardware and software
  features, policy manager platforms, and policies,
  perform proof of concept
• Implement
• Deploy QoS mechanisms and associated services
• Operate!

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Question and Answer
11/20/2009 31
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