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Spatial Reuse Protocol:Spatial Reuse Protocol:A Ring BasedA Ring Based

LAN / MAN / WANLAN / MAN / WANMAC ProtocolMAC Protocol

Mike TakefmanMike Takefman

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SRP GoalsSRP Goals

Improve economics via layer eliminationand BW multiplication

Provide fast protection and restoration

Enable Plug and Play operation

Support LAN, MAN and WAN applications

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Dedicated AccessPoP Ring

LeasedLines

Cable DataAccess Ring

Metro AccessRing

Server AccessRing

RegionalTransport

Ring

BackboneRing

RegionalTransport

Ring

HFCHFCHFCHFC

HFCHFC

HFCHFC

SiSi

SRP ApplicationsSRP Applications

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Accepted transport

architecture

Performance monitoringand self-healing

Expensive andinefficient for packets

Multiple equipment layers

Bandwidth inefficiency

SONET/SDH-BasedSONET/SDH-Based

TDM TransportTDM Transport

ProvisionedConnections

ProvisionedConnections ProtectionProtection

SONET

ADM

SONETSONET

ADMADMSONET

ADM

SONETSONET

ADMADM

SONET

ADM

SONETSONET

ADMADM

WorkingWorkingSONET

ADM

SONETSONET

ADMADM

SONET/SDHRing

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Runs over dark fiber, SONET, or WDMEnables transport mix and match

Provides efficient evolution path for existing networks

Provides optimized transport for greenfield builds

Transport Flexibility andTransport Flexibility and

EvolutionEvolution

SONETADM

SONETADM

SONETADM

SONETADM

SONETADM

SONETADM

SONETADM

SONETADM

SRPRing

WDM~~~~~~

~~~~~~

Dark Fiber

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Existing topologiesFDDI ring

Switched FDDI

ATM or Fast Ethernet

Point-to-point POS

Issues

BW limits

Complex load balanceMultiple boxes

Port counts

Previous Intra-POPPrevious Intra-POP

Connectivity OptionsConnectivity Options

SharedFDDI Ring

Internet Backbone

622 Mb/s ATM1 Gbps Ethernet

622-MbpsPOS

155- or 622- Mbps ATM100-Mb Ethernet

Internet Backbone

622-MbpsPOS

155-Mbps POS

Internet Backbone

FDDISwitch

XX XX

Internet Backbone

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SRP OverviewSRP Overview

Maximize BW efficiency

dual counter rotating ringsdestination stripping

statistical muxing of BFP

Extend IP functionality

over MAN & WAN Minimize provisioning

and configuration

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SRP OverviewSRP Overview

Multicast support

2 Traffic priorities on ring

High priority traffic has low latency patharound ring

SRP fairness algorithm (SRP-fa) controls

access to ring BW for low priority traffic

8 priority levels for Tx and Rx queueing

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SRP Cooperates with Layer 3 CoSSRP Cooperates with Layer 3 CoS

to Extend Functionalityto Extend Functionality

Layer 3 provides rich functionality and granular controls

MAC provides speed and simplicity

Enables low delay/jitter for voice and video packets

Layer 3IPLayer 3IP

Layer 2SRP MACLayer 2SRP MAC

Precedence Setting Rate Control

Congestion ControlRED/WRED

Granular SchedulingDRR on Eight Classes

Big Fat Pipes

High-Priority Bypass

Low-Priority Fairness

Precedence Mapping

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SRP fairness algorithm

Distributed algorithm

Propagates and usesMAC usage info

Source and forward ratecontrols

Rapid adaptation

and convergence

(1)(1)

(4)(4)

(2)(2)

(5)(5)(3)(3)

SRP OverviewSRP Overview

Node 1Node 1

Node 2Node 2

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SRP OverviewSRP Overview

Scalable: Bit-rate; Circumference of

ring; Up to 128 nodes

Intelligent Protection Switching (IPS)

Survivability in the event of single fiber /node failure, or signal degradation

Media independent protocolInitial implementation uses SONET/SDHframing

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SRP PacketSRP Packet

SRP is a media independent MAC layer protocol

The initial implementations utilizes ByteSynchronous HDLC within SONET/SDH framing(OC-12c, OC-48c, OC-192c)

Allows transport via: Dark Fiber; SONET/SDH;WDM

TransportTransport

OverheadOverheadPathPath

OverheadOverhead

FFLLAA

GG

MACMAC

HeaderHeaderPayloadPayload

FFLLAA

GG

FFCCSS

PayloadPayload

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Comparison with DQDBComparison with DQDB

No segmentation and reassembly

complete packets stored and forwarded

Distributed fairness without master nodes

Protection switching without master

High priority traffic for delay sensitiveapplications

No support for isochronous traffic

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Comparison with FDDIComparison with FDDI

Greater than 2x bandwidth improvement

both rings carry traffic

Destination stripping allows spatial reuse

No token to pass

FDDI-2 supported isochronous traffic &

master node

not generally implemented

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SummarySummary

Scalable packet ring technology

Bit-rate; Number of Nodes; RingCircumference

High bandwidth efficiency

Cost effectiveness

Distributed fault tolerance

LAN, MAN and WAN applications