PRESENTED BY :PRESENTED BY :

INTRODUCTIONINTRODUCTION

• Rings are the dominant topology in metropolitan backbonesRings are the dominant topology in metropolitan backbones

• Because of fast protection propertyBecause of fast protection property

-- even under a link failure, full connectivity among -- even under a link failure, full connectivity among all ring nodes is maintainedall ring nodes is maintained

• Rings have reduced deployment costs from those of star or mesh Rings have reduced deployment costs from those of star or mesh topologies as ring nodes are only connected to their two nearest topologies as ring nodes are only connected to their two nearest neighborsneighbors

TRANSPORT TECHNOLOGIESTRANSPORT TECHNOLOGIES

CIRCUIT:SONET/ATM

PACKET

MESH:ETHERNET

RING: ???

• Resilient Packet Ring (RPR) is a new packet-based transport technology for ring-based metropolitan area networks

• RPR systems are seen as the successors to SONET/SDH ADM- based rings for the efficient delivery of IP-based data traffic

• RPR technology standardized by IEEE as IEEE 802.17 RPR

• Support up to 255 station attachments

• Optimized for rings with maximum circumference of 2000 kilometers

LIMITATIONS OF SONET IN MANLIMITATIONS OF SONET IN MAN

• SONET is designed for point-to-point, circuit-switched applications

– Fixed Circuits

– Wasted Bandwidth for Meshing

– Multicast Traffic

– Wasted Protected Bandwidth

LIMITATION OF ETHERNET IN MANLIMITATION OF ETHERNET IN MAN

• Ethernet over a ringEthernet over a ring

– Make efficient use of available bandwidthMake efficient use of available bandwidth

– Far simpler and inexpensive solution for dataFar simpler and inexpensive solution for data

– Optimized for point-to-point or meshed topologiesOptimized for point-to-point or meshed topologies

• DisadvantageDisadvantage

– Not take advantage of ring topology to implement fast Not take advantage of ring topology to implement fast protection mechanismprotection mechanism

– Spanning tree protocol runs comparatively slowSpanning tree protocol runs comparatively slow

– No global fairness policyNo global fairness policy

FEATURES OF RPR FEATURES OF RPR

• Advanced protection mechanismsAdvanced protection mechanisms• Distributed controlDistributed control• Interoperability with major transmission standardsInteroperability with major transmission standards• Scalability in speed and number of nodesScalability in speed and number of nodes• Plug-and-play operationPlug-and-play operation• Performance monitoring capabilitiesPerformance monitoring capabilities• Support for a limited number of priorities (two or three)Support for a limited number of priorities (two or three)• OAM and advanced traffic and bandwidth managementOAM and advanced traffic and bandwidth management• Support for unicast, multicast and broadcast data traffic.Support for unicast, multicast and broadcast data traffic.

RING STRUCTURERING STRUCTURE• RPR networks are based on two RPR networks are based on two

symmetric counter-rotating rings symmetric counter-rotating rings

(external and internal ring) that (external and internal ring) that

carry data and control information.carry data and control information.

• The nodes/stations may send data The nodes/stations may send data

on either of the two ringlets.on either of the two ringlets.

• In most cases, the shortest path to In most cases, the shortest path to

the destination is used.the destination is used.

• Topology discovery protocol to Topology discovery protocol to

obtain a topology map of the ring. obtain a topology map of the ring.

• Packet forwarding

– Intermediate nodes forward packet if they don’t recognize destination MAC address in packet header

– Forwarding methods

• Cut-through

– Packet forwarded before completely received

• Store-and-forward

– Packet forwarded after completely received

– Supplementary 1-byte time-to-live (TTL) field

• Added to each packet by RPR MAC control entity

• Value decremented by each intermediate node

• Prevents packets with unrecognized destination MAC address from circulating forever

PHYSICAL LAYER VERSATILITYPHYSICAL LAYER VERSATILITY

• RPR create a new MAC addressing schemeRPR create a new MAC addressing scheme

• It leave Layer 1 open i.e RPR is compatible with Ethernet, It leave Layer 1 open i.e RPR is compatible with Ethernet, SONET, and DWDM physical layer standards.SONET, and DWDM physical layer standards.

NETWORK LAYER

DATA LINK LAYER

PHYSICAL LAYER

LAYERED ARCHITECTURE

RPR MACRPR MAC

• RPR MAC is responsible for providing access to the fiber RPR MAC is responsible for providing access to the fiber mediamedia

• RPR MAC can receive, transit, and transmit packets.RPR MAC can receive, transit, and transmit packets.

• Receive Decision -- Every station has a 48-bit MAC address. -- MAC will receive any packets with a matching destination address.

• Transit Path -- Nodes with a non matching address are allowed to continue circulating around the ring

• Transmit And Bandwidth Control -- RPR MAC can transmit both high and low priority packets. -- Bandwidth algorithm controls whether a node is within its negotiated bandwidth allotment for low priority packet

RPR FRAME FORMATRPR FRAME FORMAT

SERVICE CLASSSERVICE CLASS

• CLASS ACLASS A -- support real-time applications that require a guaranteed -- support real-time applications that require a guaranteed bandwidth and low jitter bandwidth and low jitter -- priority over the other types of services -- priority over the other types of services

-- token bucket shaper is provided to ensure that the client -- token bucket shaper is provided to ensure that the client

traffic does not exceed the allocated rate.traffic does not exceed the allocated rate.• CLASS BCLASS B

-- support near real-time applications that are less delay--- support near real-time applications that are less delay-

sensitive but that still require some bandwidth guarantees. sensitive but that still require some bandwidth guarantees.

-- traffic is not statically allocated.-- traffic is not statically allocated.

• CLASS CCLASS C -- best-effort traffic service with no allocated or guaranteed data -- best-effort traffic service with no allocated or guaranteed data rate and no bounds on end-to-end delay or jitter.rate and no bounds on end-to-end delay or jitter.

NODE ARCHITECTURENODE ARCHITECTURE

A three-node IEEE 802.17 RPR ring with a simplified structure of the MAC datapath entity

SPATIAL REUSESPATIAL REUSE

• Increases the overall Increases the overall

aggregate bandwidth of the aggregate bandwidth of the

ringring

• Unicast frames are removed Unicast frames are removed

from the ring at their from the ring at their

destinationdestination

• RPR uses Spatial Reuse RPR uses Spatial Reuse

ProtocolProtocol

ADDRESSINGADDRESSING

• UNICASTUNICAST

• MULTICASTMULTICAST

• BROADCASTBROADCAST

FAIRNESS ALGORITHMFAIRNESS ALGORITHM

• A fairness algorithm is a mechanism that gives every node on A fairness algorithm is a mechanism that gives every node on the ring a predetermined “fair” share of the ring bandwidththe ring a predetermined “fair” share of the ring bandwidth

TWO MODES OF OPERATION FOR THE TWO MODES OF OPERATION FOR THE RPR FAIRNESS ALGORITHMRPR FAIRNESS ALGORITHM

• AGGRESSIVE MODE:AGGRESSIVE MODE:

-- -- evolved from the Spatial Reuse Protocol (SRP) evolved from the Spatial Reuse Protocol (SRP) currently currently

deployed in a number of operational metro networks.deployed in a number of operational metro networks.

-- -- An AM node An AM node n n is said to he congested wheneveris said to he congested whenever

STQ-depth[n] > low-thresholdSTQ-depth[n] > low-threshold

• CONSERVATIVE MODE:CONSERVATIVE MODE:

-- -- Each CM node has an access timer measuring the time Each CM node has an access timer measuring the time

between two consecutive transmissions of station packets.between two consecutive transmissions of station packets.

-- A CM node -- A CM node n is said to be n is said to be congested if the access timer congested if the access timer

for station traffic expires orfor station traffic expires or

forward-rate[n] + add-rate[n] > low-threshold.forward-rate[n] + add-rate[n] > low-threshold.

RPR RESILIENCE MECHANISMSRPR RESILIENCE MECHANISMS

• RPR standard offers powerful protection methods:RPR standard offers powerful protection methods: 1. Ring wrapping 1. Ring wrapping 2. Packet steering2. Packet steering

• They are designed to minimize the traffic losses in case of They are designed to minimize the traffic losses in case of failures failures

• Aim to achieve recovery times of about 50 ms Aim to achieve recovery times of about 50 ms

• Obviating the need for SDH/SONET-based protectionObviating the need for SDH/SONET-based protection

RING WRAPPINGRING WRAPPING

RPR wrapping protection. Interchanged control messages{Request type, Source Address, Wrap Status, Path Indicator}

PACKET STEERINGPACKET STEERING

• Packet steering is based on the ability to choose the ringlet on Packet steering is based on the ability to choose the ringlet on which the data is sent.which the data is sent.

• If the preferred path is unavailable due to failure, the other If the preferred path is unavailable due to failure, the other path will be used.path will be used.

• Mandatory in RPRMandatory in RPR

• BenefitBenefit• Higher bandwidth efficiency than wrappingHigher bandwidth efficiency than wrapping

TOPOLOGY DISCOVERY ALGORITHMTOPOLOGY DISCOVERY ALGORITHM

– RPR’s topology discovery protocol determines connectivity, order RPR’s topology discovery protocol determines connectivity, order of nodes, and status of each linkof nodes, and status of each link

– At system initializationAt system initialization

• All nodes broadcast topology discovery control packets on both All nodes broadcast topology discovery control packets on both ringlets with TTL value equal to 255 (maximum number of ringlets with TTL value equal to 255 (maximum number of nodes)nodes)

• Each topology control packet contains information about status Each topology control packet contains information about status of corresponding node & its attached linksof corresponding node & its attached links

• By receiving all topology control packets, each node is able to By receiving all topology control packets, each node is able to compute complete topology image (number & ordering of compute complete topology image (number & ordering of nodes, status of each link)nodes, status of each link)

• Topology image is stored in topology database of each nodeTopology image is stored in topology database of each node

Topology map for node A before failure

Topology map for Node A after the running of the TD algorithm

RPR OVER SONETRPR OVER SONET

• RPR uses packet-switching technology while SONET uses RPR uses packet-switching technology while SONET uses TDM technology to add and drop traffic from nodes in ring TDM technology to add and drop traffic from nodes in ring topologiestopologies

• RPR was originally designed as a possible alternative to RPR was originally designed as a possible alternative to SONET that provided a SONET-like sub-50 ms resiliencySONET that provided a SONET-like sub-50 ms resiliency

• SONET is still the dominant transport infrastructure and has a SONET is still the dominant transport infrastructure and has a large installed baselarge installed base

• Instead of replacing SONET with RPR, service providers plan Instead of replacing SONET with RPR, service providers plan to deploy RPR over SONETto deploy RPR over SONET

RPR SHARED PATH OVER EXISTING SONET

RPR over SONET: ApplicationsRPR over SONET: Applications

• Transparent LAN ServiceTransparent LAN Service

TLS or Ethernet Private LAN service is an application to TLS or Ethernet Private LAN service is an application to interconnect enterprise or business users with multiple sites over a interconnect enterprise or business users with multiple sites over a private or public network.private or public network.

• Private RingPrivate Ring

A dedicated ring is a distinct private ring that has all its A dedicated ring is a distinct private ring that has all its bandwidth dedicated to one customer. Deploying RPR over bandwidth dedicated to one customer. Deploying RPR over SONET provides a data-aware SONET ring to the customer’s SONET provides a data-aware SONET ring to the customer’s many locations with better bandwidth management capabilities to many locations with better bandwidth management capabilities to leverage multi-point bursty Ethernet trafficleverage multi-point bursty Ethernet traffic

Ethernet Dedicated Private Ring for a Single Customer

Ethernet Shared Access Ring for Customers A and B

Internet Access using RPR

Video Distribution using RPR

COMPARISON WITH OTHER COMPARISON WITH OTHER TECHNOLOGIESTECHNOLOGIES• RPR-based architectures have major cost advantages over Ethernet-over-RPR-based architectures have major cost advantages over Ethernet-over-

SONET .SONET .

• To compare these technologies let: To compare these technologies let:

1. An 8-node metro ring, with a single hub1. An 8-node metro ring, with a single hub

2. Each node has to support 16 x 1GbE user interfaces 2. Each node has to support 16 x 1GbE user interfaces

with an average utilization of 100 Mbit/s, and peak with an average utilization of 100 Mbit/s, and peak

burst rate of 1000 Mbit/s.burst rate of 1000 Mbit/s.

3. 20% of the traffic is intra-metro and 80% goes out of 3. 20% of the traffic is intra-metro and 80% goes out of

the metro ring through the hub.the metro ring through the hub.

Ethernet-over-SONET ETHERNET NETWORK

RPR BASED NETWORK

RESULTSRESULTS

COST SUMMARY CHART

CONCLUSIONCONCLUSION

• Fiber Rings are extremely common in the metro and other networking environment.

• RPRs provide a reliable, efficient, and service-aware transport for both enterprise and service-provider networks.

• Combining the best features of legacy SONET/SDH and Ethernet into one layer, RPR maximizes profitability while delivering carrier-class service.

• RPR enable the convergence of voice, video and data services transport.

REFERENCESREFERENCES• Ping Yuan, Violeta Gambiroza, and Edward Knightly Rice

University “The IEEE 802.77 Media Access Protocol for High-Speed Mefropolitan-Area Resilient Packet Rings”, 2004

• Amund Kvalbein and Stein Gjessing Simula Research Laboratory, Oslo, Norway “Protection of RPR strict order traffic”,2006

• IEEE Computer Society “Part 17: Resilient packet ring (RPR)

access method and physical layer Specifications”,2007

• Eduardo de la Cruz Gámez PalizaTechnology Institute of Acapulco Acapulco, Guerrero, México “Protection in a RPR- in a RPR-MAN Node”,2006MAN Node”,2006