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Xsigo Systems 1

Enhanced Flow control inEthernet Networks

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Agenda

• Review the proposal to support thecommunication of congestion information

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Xsigo Systems 3

Some Facts …

• Ethernet has fulfilled the expectations of applications with best effort delivery model forpast 3 decades

• Throwing more bandwidth at the problem does not

solve congestion problem since queuing delays aremore than wire delays• Convergence of mission critical and non-mission

critical applications over shared network infrastructure require traffic differentiation

• Is it time to enhance ethernet?

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Xsigo Systems 4

Ethernet : Is it time to enhance it?

– Businesses rely heavily on predictable performance of IT andnetwork infrastructure

– Businesses needs more intelligent and adaptable network infrastructure to meet business needs

– Commoditization of compute and sharing of same network infrastructure between mission critical and non-mission criticalapplications require

• Intelligent network infrastructure with prioritization anddifferentiation of traffic

• Guaranteed performance per traffic type to meet business SLA

• Ethernet requires enhancements not disruptive changes

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Xsigo Systems 5

802.1p and Flow control in Ethernet Networks

Server #1

Switch #1

Server #2

Switch #2

Ethernet Pipe

Ethernet Pipe

Flow Control

Flow

ControlCongestion

Point

Ethernet Pipe

FlowControl

E t h er n

e t

P i p e

F l

ow

C on

t r ol

Server #3

Flow control inEthernet Networks

802.1p supports

prioritizationof the traffic

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Xsigo Systems 6

Flow control

• Limitations– One traffic class affect another in true loss-less fabric

implementation• Flow control (802.3X) does not have prioritization• One VLAN traffic can block another VLAN traffic

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Xsigo Systems 7

Flow control Requirements

• Traffic type differentiation– Congestion should be reported based on traffic types,

E.g. priority, {VLAN,Pri}, other finer level flows arepossible, not relevant in this group

– Avoid head-of-line blocking between traffic types

• Fairness– Congestion information should be reported to all the

sources who can potentially send traffic to congesteddestination

• Keep Flow control traffic as low as possible

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Xsigo Systems 8

Flow control Proposal

• Flow control per VLAN per priority• Flow control packet per VLAN can be

broadcasted back to all the sources to turnoff traffic destined to a MAC address (End node) orgroup of MAC addresses going throughcongested switch port

• This is in addition to link level flow control

defined today

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Flow control Example

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Congestion Point #1

• Switch #1’s output port connected to switch #2 is congested• This port carry traffic for server #6, VLAN A and server #7,

VLANB• Ingress side of this port sends two broadcast flow control packets• One on VLAN A

– Packet includes DMAC 6, VLAN A, Priority and time to stop

etc …• One on VLAN B

– Packet includes DMAC 7, VLAN B, Priority and time to stopetc …

• Traffic towards server #5 will not be affected

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Xsigo Systems 11

Congestion Point #2

• Server #7 is congested• Server #7 sends broadcast flow control packet on

VLAN B to all sources belong to same VLAN– Packet includes DMAC 7, VLAN B, Priority and time

to stop

• Traffic towards any other server except #7 will notbe affected!

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Xsigo Systems 12

Congestion Point #3

• Server #6 is congested• Server #6 sends broadcast flow control packet on

VLAN B to all sources belong to same VLAN– Packet includes DMAC 6, VLAN B, Priority and time

to stop

• Traffic towards any other server except #6 will notbe affected!

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Xsigo Systems 13

Congestion Point #4

• Server #5 is congested• Server #5 sends broadcast flow control packet on

VLAN A to all sources belong to same VLAN– Packet includes DMAC 5, VLAN A, Priority and time

to stop

• Traffic towards any other server except #5 will notbe affected!

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Xsigo Systems 14

Summary

• Ethernet needs enhancement in congestionreporting mechanism back to sources– The mechanism has to be fair to all the sources

• Use VLAN based broadcast support to reportcongestion information back to sources withfairness

• This proposal allows to differentiate various traffic

types on ethernet networks with fairness andguaranteed service

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Xsigo Systems 15

Thank You