Technical Presentation Series: QoS for MultiService IP Networks Quality of Service for MultiService...

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 -

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


Enterprise Quality of Enterprise Quality of ServiceService

… … What is it & Why do we need it?What is it & Why do we need it?


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)

— Non-RT, Interactive traffic (Web surfing)

— Non-RT, Mission Critical traffic (e-Commerce)

— Non-RT, non-Mission Critical traffic (everything else)

• Service Providers offering/pricing tiered levels of service

• Service differentiation in Intranets

— Ability to assign business priorities to traffic or users


Traffic Classification Proposal

Real-time, Delay Intolerant

Absolute priority with no packet discard.

Delay typically < 50ms

Traffic Category Required Treatment

Inter-human communications (interactive), e.g., VoIP, Video conferencing

Real-time,Delay Tolerant

Guaranteed delivery with little to no packet discard Delay typically < 500ms

Single-human communication (non-interactive), e.g., Steaming audio or video

Application Examples

Non-Real-time, Mission Critical

Guaranteed delivery with minimal packet discard

Delay typically < 5000ms

Transaction processing, e.g., financial transactions, e-commerce

Non-Real-time, Non-Mission Critical

Best effort deliveryEmail, Web, FTP, SNMP, etc.


PEN (Policy Enabled Networking) Strategy

3 Key Focus Areas

• QoS and Service Classification– Define Enterprise End-to-End QoS architecture– Standardize Service Classes used across Nortel products

• Packet Flow Classification– Define Queuing Mechanisms– Define Congestion Avoidance Mechanisms

• Policy Enablement– Define Centralized Policy Management requirements


CoSQoS

CoS CoS CoS

WAN

QoS/CoS: What’s the difference?

For sake of discussion, let us define the following:

• CoS (Nodal):

— Behavioral treatment of traffic flows through a network node

— Traffic Prioritization and Discarding

• QoS (Network):

— Guaranteed level of traffic service performance across network

— CoS plus BW reservation/admission control mechanisms


Simple Message:QoS achieved using CoS Mechanisms

QoS Vision

• QoS over LANs — Achieved using simple CoS mechanisms

• QoS over WANs— Today: Requires BW reservation/admission control mechanisms

— Future: Will only need simple CoS mechanisms

• Vision will be achieved by implementing:— Best CoS and congestion avoidance mechanisms

— Consistent treatment of CoS across all products

— Robust Policy Management solution


Differentiated Services Differentiated Services ModelModel

… … The industry directionThe industry direction


Differential Services (DiffServ) Model

• End-to-End Architecture defined by RFC 2475

— Defines CoS on a Per Hop basis

— Relies on congestion avoidance mechanisms

— Requires all network nodes to comply to be effective

• “Open Loop” system

— No feedback from network to determine if there is congestion

• DiffServ Domain

— Set of DiffServ nodes with common service provisioning policy

— Policy Manager provides the policy


DiffServ Domain

• DiffServ Domain across Campus LAN

Ingress or Egress Nodes(Network Edge)

L2 Switch L3 SwitchInterior LAN Nodes

(Network Core)


Packet Treatment by DS Edge NodesPolicing

Scheduling

MarkingDSCP

Shaping

• Filtering based on:

— S/D IP Address, TCP/UDP Port, Protocol ID, DS Field (ToS)

• Policing— Does the flow conform to policy?

• Marking

— Mark/Re-mark DS Code Point based on policy

• Congestion Management

— Drop Precedence

— Avoidance: RED or WRED

• Shaping

— Improves efficiency and conformance to policy

• Scheduling

— Ensures queues get serviced according to priorities


Shaping

Scheduling

Packet Treatment by DS Core Nodes

Policing

MarkingDSCP

Shaping

• Congestion Management — Drop Precedence— Avoidance: RED or WRED

• Shaping— Improves efficiency and conformance to policy

• Scheduling— Ensures queues get serviced according to priorities

Scheduling


Per-Hop Behaviors (PHBs)

• PHBs are the packet-forwarding treatment that delivers the “differentiated service” to packets at network nodes

— Policing

— Possible remarking of DS Code Point (DSCP)

— Enqueuing treatment (e.g., drop preference)

— Shaping

— Scheduling

• IETF has defined the following DiffServ PHBs:

— Expedited Forwarding (EF) - RFC 2598

— Assured Forwarding (AF) - RFC 2597

— DEfault Forwarding (DE) - RFC 2474


DS Field

• DS Field defined by RFC 2474

• Supercedes existing definitions

— IPv4 ToS Field (RFC 791)

— IPv6 Traffic Class Octet (RFC 2460)


DiffServ Traffic ClassificationDiffServ Traffic Classification


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


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


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


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


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)


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


Mapping IP to/from Link Mapping IP to/from Link LayersLayers

… … preserving DiffServ behavior at Layer 2preserving DiffServ behavior at Layer 2


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


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


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


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


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)


RSVP for QoS SignalingRSVP for QoS Signaling

… … a new use for RSVPa new use for RSVP


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


L2 Switch• Sets DSCP and 802.1p User Priority based on OPS policy setting

L3 Switch• Sets DSCP or 802.1p

User Priority based on OPS policy setting

Etherset • Sets DSCP or

802.1p User Priority

PBX VoIP• Sets DSCP• Upstream devices configured to respect DSCP• Supports H.323

Router (VoIP Media Gateway)• Sets DSCP based on OPS policy setting• “State” is maintained between OPS and

router

IP Classification w/o RSVP QoS Signaling


IP Classification with RSVP QoS signaling

Client PC• QoS signaled via RSVP• Win2000 app. sets DSCP• NIC sets 802.1p user priority

L2 Switch• Detects RSVP packet and forwards to OPS• OPS sends DSCP via COPS• Maps DSCP to 802.1 user priority

L3 Switch• Detects RSVP packet

and forwards to OPS• OPS determines

DSCP and sends via COPS

Etherset• Sets DSCP or

802.1p User Priority

PBX VoIP• Sets DSCP• Upstream devices configured to respect DSCP• Supports H.323

Router VoIP Media Gateway• Detects RSVP packet• Requests policy from OPS based on

RSVP message• Sets DSCP based on Optivity Policy

Server (OPS) policy setting• “State” is maintained between OPS

and router


Summary

• DiffServ is the predominant IP QoS Architecture

• IP QoS is in the early stages of standardization

• Good traffic management required to make all this work

• Policy Enablement simplifies and automates network administration


Thank youThank you

Questions ?Questions ?

John A. Clark - Technical Account ManagerJohn A. Clark - Technical Account Manager

Technical Presentation Series: QoS for MultiService IP Networks Quality of Service for MultiService...

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