Quality of Service for MultiService IP Networks 8th March 2000 John A. Clark - Technical Account Manager

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 Service … 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 Businesses are rapidly becoming aware of the benefits of sharing information across traditional boundaries. Those boundaries may have been within one office area or building to domestic and international locations. Fueling network growth are the applications evolving to simplify the sharing of information across logical and physical boundaries. Some of the more dynamic applications that can have an immediate financial impact and promote collaboration among groups is video and teleconferencing. In a global economy, travel is a necessary evil. Companies looking to improve bottom line performance must become more efficient with valuable , scarce resources. Video and teleconferencing can help reduce unnecessary and expensive trips. However, both video and voice communications have very little tolerance for variations in delay. These kind of applications require special treatment if they are to be effective. Another tool driving networks to provide Quality of Service is thew World Wide Web. The WWW is this generations ultimate answer to sharing information. Businesses have taken the concept and applied it to their own internal networks and coined it the “Intranet”. Extending a subset of the corporate resources to external sources (customers and suppliers) is a version called the “Extranet”. Network managers need to apply a set of rules to the wild and woolly communication resource they have opened. They need to make sure the traffic that drives the companies existence is given a higher priority than recipes for the world’s best chili for the weekend picnic.

Traffic Classification Proposal Traffic Category Application Examples Required Treatment Inter-human communications (interactive), e.g., VoIP, Video conferencing Absolute priority with no packet discard. Delay typically < 50ms Real-time, Delay Intolerant Single-human communication (non-interactive), e.g., Steaming audio or video Guaranteed delivery with little to no packet discard Delay typically < 500ms Real-time, Delay Tolerant Transaction processing, e.g., financial transactions, e-commerce Guaranteed delivery with minimal packet discard Delay typically < 5000ms Non-Real-time, Mission Critical Non-Real-time, Non-Mission Critical Email, Web, FTP, SNMP, etc. Best effort delivery

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

QoS/CoS: What’s the difference? WAN CoS CoS CoS CoS QoS 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 Others: An architecture delivering fast, reliable, predictable, differentiated service over a network

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 Simple Message: QoS achieved using CoS Mechanisms

Differentiated Services Model … The 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

Ingress or Egress Nodes DiffServ Domain DiffServ Domain across Campus LAN L2 Switch L3 Switch Interior LAN Nodes (Network Core) Ingress or Egress Nodes (Network Edge)

Packet Treatment by DS Edge Nodes Policing Shaping Scheduling Marking DSCP 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

Packet Treatment by DS Core Nodes Policing Shaping Scheduling Shaping Marking DSCP Scheduling Congestion Management Drop Precedence Avoidance: RED or WRED Shaping Improves efficiency and conformance to policy Scheduling Ensures queues get serviced according to priorities

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 Prioritization of traffic flows means that traffic is classified in a network, and that the entire “class of service” is given a priority. Each network node point may have its own per-hop-behaviors, depending on the requirements of the traffic and the network. For example, the network can be set up to classify all voice traffic as high, all data traffic as low, all video traffic as medium. Traffic can be “shaped” or smoothed out to minimize the effect of burstiness Traffic can be marked to designate lower-priority packets that can be dropped in cases of high congestion Traffic can be policed, to ensure that it conforms to the levels set forth by Service-Level Agreement in place Traffic is scheduled based on classification, through the priority queuing process The above process of classifying, marking, policing and shaping, is managed at edge and boundary routers that support DiffServ.

DS Field DS Field defined by RFC 2474 Supercedes existing definitions IPv4 ToS Field (RFC 791) IPv6 Traffic Class Octet (RFC 2460)

DiffServ 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 Forwarding treatment requires that (at each node) egress rate exceeds ingress rate for a conforming aggregate “Virtual leased line” Police and drop on network ingress Modest buffering needed (no burst) Some form of priority queuing Shape on egress to maintain contract to next provider Should be kept to a small fraction of total network traffic Proposed Standard EFDSCP = 101110

Assured Forwarding (AF) PHB - RFC 2597 Lowest Latency Highest Latency Lowest Discard Highest Discard Four traffic classes Each with assigned guaranteed bandwidth levels Similar to Frame Relay CIR Three drop preferences for each traffic class High/Medium/Low drop preference Similar to Frame Relay DE Token bucket policers for each priority Enqueuing uses RED or similar mechanism To distinguish between drop preference and control congestion Scheduling based on bandwidth given to the priority 4 AF Classes (priority classes) 3 Drop Precedences per AF class 6-bit value located in the DS Field

Proposed Service Classification for Nortel DiffServ PHBs EF PHB AF PHBs DE PHB Service Class names make configuration more intuitive

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) Weighted Round Robin (WRR) All queues are serviced in sequence, e.g., Q1, Q2, Q3, Q1, etc. % BW assigned to each queue Focus on Throughput Weighted Fair Queuing (WFQ) Suited for delay-intolerant interactive traffic Low BW flows serviced before high BW flows High BW flows share remaining BW Focus on Latency Performance

Nodal Handling

Mapping IP to/from Link Layers … preserving 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

Ethernet 802.1p User Priorities 6 bytes 6 bytes 4 bytes 2 bytes 64-1500 bytes Dest MAC Source MAC 802.1q TAG Protocol Type Data Priority bits C F I VLAN ID 81 - 00 Tag Protocol Identifier Tag Control Info 8 User Priorities (traffic classes) DiffServ PHB mapped to/from 802.1p User Priorities

DSCP to 802.1p Mapping Example 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 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 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 Signaling … a 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 RSVP traditionally associated with IntServ architecture Creates “stateful” connection-oriented end-to-end paths IntServ never gained popularity due to limited scalability RSVP for DiffServ Will not maintain “stateful” end-to-end connections RSVP used to request bandwidth, priority, authentication and authorization DiffServ architecture will provide QoS via associated behavioral treatment of packets in each DS node

IP Classification w/o RSVP QoS Signaling 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 L3 Switch Sets DSCP or 802.1p User Priority based on OPS policy setting L2 Switch Sets DSCP and 802.1p User Priority based on OPS policy setting Etherset Sets DSCP or 802.1p User Priority

IP Classification with RSVP QoS signaling 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 L3 Switch Detects RSVP packet and forwards to OPS OPS determines DSCP and sends via COPS Etherset Sets DSCP or 802.1p User Priority 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

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

Questions ? John A. Clark - Technical Account Manager Thank you Questions ? John A. Clark - Technical Account Manager