Technical Presentation Series: QoS for MultiService IP Networks Quality of Quality of Service Service for for MultiService IP Networks MultiService IP Networks 8th March 2000 8th March 2000 John A. Clark John A. Clark - Technical Account Manager - Technical Account Manager
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Technical Presentation Series: QoS for MultiService IP Networks Quality of Service for MultiService IP Networks 8th March 2000 Quality of Service for MultiService.
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Technical Presentation Series: QoS for MultiService IP Networks
Quality of ServiceQuality of Service for for
MultiService IP Networks MultiService IP Networks 8th March 20008th March 2000
John A. ClarkJohn A. Clark - Technical Account Manager- Technical Account Manager
Technical Presentation Series: QoS for MultiService IP Networks - Page 2
Agenda
• Overview of Enterprise Quality of Service
• The Differentiated Services Model
• DiffServ Traffic Classification
• Mapping DiffServ to/from Link Layers
• RSVP for QoS Signaling
• Summary
Technical Presentation Series: QoS for MultiService IP Networks
Enterprise Quality of Enterprise Quality of ServiceService
… … What is it & Why do we need it?What is it & Why do we need it?
Technical Presentation Series: QoS for MultiService IP Networks - Page 4
What is driving the need for QoS?
• Increasing number of network users and applications
• New applications and traffic dynamics
— RT, Interactive traffic (VoIP)
— RT, non-Interactive traffic (Video on Demand, RealMedia)
Technical Presentation Series: QoS for MultiService IP Networks - Page 17
Expedited Forwarding (EF) PHB - RFC 2598
• “Virtual leased line” Substitute “Service”— Police and drop on network ingress— Modest buffering needed (no burst)— Typically uses strict priority queuing— Shape on egress to maintain contract with next DS Domain
• Network Engineering Requirements
— Egress rate must exceed ingress rate
• Traffic Engineering Guidelines
— For multiservice networks, EF Traffic is typically kept to a small fraction of total network traffic, e.g., 10%
— However, this is completely application-dependent
EFDSCP = 101110
Technical Presentation Series: QoS for MultiService IP Networks - Page 18
Assured Forwarding (AF) PHB - RFC 2597
DropPrecedence
Class 1 Class 2 Class 3 Class 4
Low 001010(AF11)
010010(AF21)
011010(AF31)
100010(AF41)
Medium 001100(AF12)
010100(AF22)
011100(AF32)
100100(AF42)
High 001110(AF13)
010110(AF23)
011110(AF33)
100110(AF43)
LowestLatency
HighestLatency
HighestDiscard
LowestDiscard
• 4 AF Classes (priority classes)
• 3 Drop Precedences per AF class
• 6-bit value located in the DS Field
Technical Presentation Series: QoS for MultiService IP Networks - Page 19
Proposed Service Classification for Nortel
User TrafficCategory
Service ClassName
Real-time,Delay Intolerant
Premium
PlatinumReal-time,Delay Tolerant Gold
SilverNon-Real-time,Mission Critical Bronze
Non-Real-time,Non-Mission Critical
Standard
EF PHB
DE PHB
AF PHBs
Service Class names make configuration more intuitive
DiffServ PHBs
Technical Presentation Series: QoS for MultiService IP Networks - Page 20
Congestion Avoidance Mechanisms
• Required for DiffServ architecture to work properly
• Drop Precedence
— AF PHB offers 3 levels of drop precedence for each AF class
— All DE PHB traffic is eligible to discard
— No EF PHB traffic is eligible to discard
• RED
— Required to break global synchronization of TCP/IP sessions
— Actively and randomly drops packets
— WRED/MRED variants allow weighting of different queues
Technical Presentation Series: QoS for MultiService IP Networks - Page 21
Traffic Scheduling
• Strict Priority Schedulers
— Assigns a fixed % of total BW to a queue
— Queue must be emptied prior to others being serviced
• Weighted Bandwidth Schedulers
— Lower priority queues borrow higher priority queue BW when available– Higher priority queues reclaim borrowed BW as needed
— Two Commonly used algorithms– Weighted Round Robin (WRR)– Weighted Fair Queuing (WFQ)
Technical Presentation Series: QoS for MultiService IP Networks - Page 22
Nodal Handling
Traffic Category ServiceClass
SchedulingMechanism
DiscardEligibility
DiffServ PHB
Real-time,Delay Intolerant
Premium Strict Priority None withinprofile
EF
Platinum WFQ, WRR Lowestwith RED
AF1Real-time,Delay Tolerant
Gold WFQ, WRR Lowwith RED
AF2
Silver WFQ, WRR Mediumwith RED
AF3Non-Real-time,Mission Critical
Bronze WFQ, WRR Medium-Highwith RED
AF4
Non-Real-time,Non-Mission Critical
Standard WFQ, WRR Highwith RED
DE
Technical Presentation Series: QoS for MultiService IP Networks
Mapping IP to/from Link Mapping IP to/from Link LayersLayers
… … preserving DiffServ behavior at Layer 2preserving DiffServ behavior at Layer 2
Technical Presentation Series: QoS for MultiService IP Networks - Page 24
IP/Layer 2 Traffic Classification
• IP Filtering on:— Source/Destination IP Address— Source/Destination TCP/UDP Port number— DSCP— Protocol ID
• Ethernet 802.1p User Priorities— 8 User Priorities— Highest level queue serviced before next lower level queue
• ATM— CBR, rt-VBR, nrt-VBR, ABR, UBR— Single or Multiple Virtual Circuits
• Frame Relay— CIR, EIR, DE— Single or Multiple Virtual Circuits
Technical Presentation Series: QoS for MultiService IP Networks - Page 25
Ethernet 802.1p User Priorities
• 8 User Priorities (traffic classes)
• DiffServ PHB mapped to/from 802.1p User Priorities
6 bytes 6 bytes
DestMAC
SourceMAC
802.1qTAG
4 bytes
ProtocolType
2 bytes
Data
64-1500 bytes
TagProtocolIdentifier
TagControlInfo
81 - 00Priority
bitsCFI
VLANID
Technical Presentation Series: QoS for MultiService IP Networks - Page 26
DSCP to 802.1p Mapping Example
ServiceClass
DiffServ Code Point(DSCP)
802.1p UserPriority
Premium EF 7
Platinum AF11, AF12 or AF13 6
Gold AF21, AF22 or AF23 5 (or 4)
Silver AF31, AF32 or AF33 3 (or 2)
Bronze AF41, AF42 or AF43 0 (Default)
Standard DE 1
• Standard, power-up default mapping
• Egress to non-Layer 3 “aware” L2 Switch— Required because L2 switch cannot interpret DSCP
Technical Presentation Series: QoS for MultiService IP Networks - Page 27
DSCP to ATM CoS Mapping Example
Service ClassName
DiffServ CodePoint (DSCP)
ATM CoS
Premium EF CBR
Platinum AF11, AF12 or AF13
Gold AF21, AF22 or AF23 rt-VBR
Silver AF31, AF32 or AF33
Bronze AF41, AF42 or AF43 nrt-VBR
Standard DE ABR or UBR
• Sample, power-up default mapping
• ATM to DSCP mapping not required
— IP DSCP is preserved across ATM network
Technical Presentation Series: QoS for MultiService IP Networks - Page 28
DSCP to Frame Relay VC Mapping Example
ServiceClass
DiffServ Code Point(DSCP)
Frame RelaySVC or PVC
Premium EF VC#1
Platinum AF11, AF12 or AF13 VC#2
Gold AF21, AF22 or AF23 VC#3
Silver AF31, AF32 or AF33 VC#4
Bronze AF41, AF42 or AF43 VC#5
Standard DE VC#6
• Frame Relay does not have any native CoS mechanisms
• Each VC is assigned the following for each flow— Guaranteed BW (CIR) — Burst BW (EIR) — Discard Eligibility (DE)
Technical Presentation Series: QoS for MultiService IP Networks
RSVP for QoS SignalingRSVP for QoS Signaling
… … a new use for RSVPa new use for RSVP
Technical Presentation Series: QoS for MultiService IP Networks - Page 30
New use for RSVP
• RSVP for DiffServ
— Used as a QoS signaling mechanism
— Application or appliance uses RSVP to request:– Bandwidth– Prioritization– Authentication– Authorization
— Request made to edge device in DiffServ domain
— Edge device or Policy Server admit or reject request
— Driven by Microsoft’s inclusion of RSVP enabling technology in Windows 2000
Technical Presentation Series: QoS for MultiService IP Networks - Page 31
L2 Switch• Sets DSCP and 802.1p User Priority based on OPS policy setting