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Resilient Ethernet

September 2008

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Resilient Ethernet: What is it?

Resilient definition: “tending to recover or adjust from misfortune”

In the case of Ethernet, “misfortune” is congestion

Resilient Ethernet Buffering to minimize or eliminate packet loss

during temporary congestion Extensive traffic management to maintain QoS Does not require:

Carrier Ethernet standards OAM Scalability

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Tools of Resilient Ethernet

Extensive traffic management CIR/EIR CBS/EBS ingress policing Police per port, EVC, traffic-class per EVC

Deep buffering Internal buffering (dedicated) typically at <1MB

At 10Gbps rates: 80us of temporary congestion – no packet loss

External buffering (dynamic) at ~200MB At 10Gbps rates: >100ms of temporary congestion - no packet loss

Congestion avoidance Congestion avoidance per output queue WRED\Tail Drop with configurable thresholds

EIR

CIR 100Mb

400Mb

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Resilient Ethernet Application

Multiple processors or IO connected through L2 Ethernet fabric Unpredictable traffic Random congestion at each port

Potential Applications VoD Servers, IPTV platforms, multi-

protocol transport

10GE MAC

SPI4.2

CPU CPU CPU IO IO

10GE Uplinks

GbE Ports

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Enterprise Switch Operation

500Mbps burst on one port penalizes other traffic for the congested port

Goal is to penalize the “bursty” port only

Possible solutions Move to 10GE links Enterprise Switch

All ports penalized

RESILIENT ETHERNET

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Resilient Ethernet Operation

Bursty port does not penalize well-behaved traffic Penalty for the “bursty” port is gradual

Temporary over-subscription: Packets are stored in deep buffers Long-term over-subscription: “Green” guaranteed, “Yellow” dropped WRED is designed specifically for bursty traffic

Averages queue depths so that only sustained oversubscription causes drops. Deep packet buffers are required to run WRED effectively

(Only bursty port penalized)

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Summary

Resilient Ethernet is required in many triple play applications

Unpredictable and wide range of traffic patterns

Brooklyn-10 is architected to provide Resilient Ethernet

switching through: Carrier-grade QoS features such as policing & congestion avoidance Deep buffers for true WRED operation

Well-behaved ports are NEVER penalized Penalty for the “bursty” port is gradual

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More Information Available

Lightstorm website http://www.lightstormnetworks.com/

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