A Practical Approach for Providing QoS: MPLS and

DiffServ

A Practical Approach for Providing QoS: MPLS and

DiffServ

Thomas TelkampDirector Data Architecture and TechnologyGlobal Crossing Telecommunications, Inc.telkamp@gblx.net

MPLSMaximizing the Performance and

Profitability of Optical and Data Networks

July 12 - 13, 2001

Dublin, Ireland

AgendaAgenda

•Global Crossing MPLS deployment•Quality of Service?•A Practical Approach

Network Design and Capacity Planning Differentiated Services MPLS for Traffic Engineering Fast Reroute and Per-Class TE Queuing and Scheduling

•Conclusion

Based on announced network

SAC

PAC

MAC

AC-1PEC

North American Crossing

PC-1

EAC

AC-2

Global Crossing IP Backbone NetworkGlobal Crossing IP Backbone Network

GBLX MPLS DeploymentGBLX MPLS Deployment

•Operational since 2Q 1999 Traffic Engineering IP TTL issues

•Worldwide MPLS mesh 1Q 2001•Currently over 6000 LSPs•Network:

Cisco and Juniper routers OC-48 wavelengths Covering Asia, US, South America and Europe

•New Services: VPN (L2/L3)

MPLS Traffic EngineeringMPLS Traffic Engineering

Quality of Service?Based on a paper with XiPeng Xiao (Photoris, Inc.) and Lionel M. Ni (Michigan State University)

Quality of Service?Based on a paper with XiPeng Xiao (Photoris, Inc.) and Lionel M. Ni (Michigan State University)

•Best Effort (e.g. Internet)•Real-time/Mission-critical traffic (e.g. Voice)•Increase revenue by value-added services•Two extremes:

Overprovisioning of bandwidth without additional mechanisms

Sophisticated mechanisms such as per-flow classification/policing/queuing and scheduling

What Causes Problems?What Causes Problems?

•Overloaded servers, or access to servers Web, E-mail, etc.

•TCP stack implementations•Link failures

fiber cuts transmissions equipment failures

•Router failures complex software early deployment of features configuration

A Practical ApproachA Practical Approach

•Good Network Design•Differentiated Services (DiffServ)•Traffic Engineering•Traffic Protection (Fast Reroute)•Class-based Queuing•Not:

Extremely complex schemes (e.g. per-flow)• affecting equipment reliability• difficult to configure and manage

Network DesignNetwork Design

•Avoid single points of failure•No bottlenecks in normal condition•Overprovisioning

with use of TE network can handle all traffic, even when the most critical links fails

•Routing (IGP and BGP)•Security and Denial of Service attacks•Capacity Planning

Differentiated ServicesDifferentiated Services

•How many classes? What are the targeted applications for each

class? Can end users distinguish between classes?

•Example: Class 1: Real-time

• application: voice Class 2: Assured

• application: trading, non-interactive audio and video

Class 3: Best Effort• application: Internet

MPLS DeploymentMPLS Deployment

•Traffic Engineering Avoid congestion caused by uneven traffic

distribution Macro control Constraint based LSP setup

•Two LSP meshes: Real-time traffic vs Assured/Best Effort Classification based on interface or multi-field

lookup Different metrics

•LSP Hierarchy Scalability and VPNs

MPLS LSP DeploymentMPLS LSP Deployment

Traffic ProtectionTraffic Protection

•IGP convergence (OSPF/IS-IS) takes seconds But can be improved by timer and SPF

tuning• see Packet Design paper

•MPLS Fast Reroute Link or Node protection Pre-configured patch LSPs (sub-optimal) Use for real-time traffic only, or for all

traffic (based on implementation)

MPLS Fast RerouteMPLS Fast Reroute

•Protecting router switches traffic to pre-configured patch LSP after failure detection (fast)

•Ingress router reroutes LSP (slow)

MPLS Cloud

Ingress LSR(k)Protectingrouter

Egressprotected segment

(1) failure detected

(2) patch LSP activated

(3) lsp rerouted

Per-Class Traffic EngineeringPer-Class Traffic Engineering

•Avoid concentration of real-time traffic at any link

•Set upper limit on bandwidth reservations per class E.g. max. 40% of a link for VoIP traffic

•IETF Internet Draft(s) on ‘Diff-Serv-aware MPLS Traffic Engineering’ (Francois Le Faucheur, et al.)

Class-based QueuingClass-based Queuing

•Prefer ‘higher’ classes during congestion sub-optimal fast-reroute period major failures

•Different queuing/scheduling mechanisms Strict Priority Queuing

• Jitter control for EF traffic WRR/WFQ and combinations

•Configuration issues...

Random Early DetectionRandom Early Detection

•Buffer Management prevent tail-drop

• TCP oscillations and synchronization RED drops based on average queue

length WRED drops with different probability for

each class•Only during congestion•Not used to guarantee bandwidth!

ConclusionConclusion

•Use combination of good network design, over-provisioning and MPLS/DiffServ

•Use Traffic Engineering to prevent congestion•Use fast reroute and priority queuing for real-

time traffic•Use WRR/WFQ to differentiate between

Assured and Best Effort traffic

•Too complex and too many features will make the network unreliable/unstable

Questions?Questions?