RESILIENT PACKET RING NETWORK(RPR)

INTRODUCION The nature of the public network has changed. Demand for Internet Protocol(IP)data is growing at a compound annual rate of between 100% and 800%1,while voice demand remains stable. Over the last 10 years, as data traffic has grown both in importance and volume,technologies such as frame relay,ATM,and point-to-point protocol (PPP) have been developed to force fit data onto the circuit network More recently,Gigabit Ethernet has been adopted by many network service providers. Gig has shortcomings when applied in carrier networks were recognized and for these problems, a technology called Resilient Packet Ring Technology were developed.

Resilient Packet Ring Technology (RPR).

Resilient Packet Ring (RPR) is an emerging network architecture and technology designed to meet the requirements of a packet-based metropolitan area network(MAN).

Neither SONET nor Ethernet is ideal for handling multimedia traffic on a ring network

Resilient Packet Ring (RPR) is a network topology being developed as a new standard for fiber optic rings

It works in point to point ,ring or mesh networks.Uses MAC layer tech.(Standardized as IEEE 802.17)

Resilience proactive span protection automatically avoids failed spans within 50 ms.

Services support for latency/jitter sensitive traffic such as voice and video.support for committed information rate (CIR) services.

Efficiency spatial reuse:Unlike SONET,bandwidth is consumed only between the source and destination nodes.packets are removed at their destination ,leaving this bandwidth available to downstream nodes on the ring.

Scalable supports topologies of more than 100 nodes per ring.

RPRs Key features

RPR uses a dual counter rotating fiber ring topologyBoth rings inner and outer are used to transport working traffic between nodes By utilizing both fibers

RPR utilizes the total available ring bandwidth fibers are used to carry control messages control message flow in the opposite direction

of the traffic that they represent.using bandwidth-control messages

a RPR node can be dynamically negotiate for bandwidth with the other nodes on the ring.

It has ability to differentiate between low-and high-priority packets nodes have the ability to transmit high-priority packets

before those of low priority  

RPR Operation

• RPR nodes also have a transit path • It has a transit buffer capable of holding multiple packets • Nodes with smaller transit buffers

use bandwidth-control messages

RPR Media Access Control(MAC). • one of the basic building blocks of RPR. • responsible for providing access to the fiber media. • can receive,transit and transmit packets.

Receive Decision

TX BW Control

Transit Path

To Host

Topology

From Host

ProtectionTXBW

To Host From Host

From West Fiber

To West Fiber

To East Fiber

MAC Block Diagram

Receive Decision • Every station has 48 bit MAC address.• MAC will receive any packets with a matching destination address • MAC receive both unicast and multi cast packets • there are also control packets that are meant for the neighboring node• these packets do not need a destination or source address.Transit Path • nodes with non matching dstn address are allowed to circulate• RPR packets are only inspected for a matching address

and header errors Transmit and Bandwidth Controls RPR MAC can transmit both high-and-low priority packets for low-priority packets bandwidth algorithm controls

whether a node is within its negotiated bandwidth allotment bandwidth-control algorithm

Protection RPR has the ability to protect the network from single

span failures. Wrapping

Nodes neighbouring the failed span diverts the packet by wrapping traffic around to the other fiberspan Topology Discovery:

RPR has a topology discovery mechanism Physical Layer

RPR packet can be transported over both SONET and Ethernet physical layers

SONET physical layer offers robust error and performance monitoring.

when using SONET physical layer,RPR can be carried over dark fiber.

RPR packets can be encapsulated within the synchronous payload envelope(SPE)

RPR Mac frame

Flow ID

Header Error Check(2)

Destination Address(6)

Source Address (6)

Payload Type(2)

TTL(1)

Payload

CRC (4)

C E

Destination Address: •is the MAC address of the ring to which the frame

is being transmitted

• address can also be a broadcast address. Source Address

• is the MAC address of the ring nodefrom which the frame is being transmitted.

Payload Type• this two byte field tells the system what type of the payload

follows the RPR field. For example MPEG,ATM or Ethernet.

Class of service(CoS): • this three byte CoS field allows the identification of

up to eight Classes of services, including Expedited Forwarding(EF), six levels of Assured Forwarding(AFI through AF6),

and Best Effort(BE).

Extension(E) Bitindicates that there is an extension to the RPR headerallows for fields that may be added in the future.

Flow ID(optional)allows the simple manual or automatic setup of

connection oriented services includingTime Division Multiplexed(TDM)20 BIT field.

Time to live(TTL): the one bit TTL field is included to allow the RPR ring topology Header Error Check(HEC)

provides a way to test the integrity of the header, allowing for persistent delivery of frames

Cyclic Redundancy Check(CRC)this 4 byte CRC works differently in RPR than it does for standard Ethernet .

Comparison between Gigabit Ethernet and RPR

GIGABIT ETHERNET RPR

Enterprise-class equipment Carrier-class equipment

Provides Data service only Data, circuit or video service

Works in Point-to-point or mesh topology(No Rings)

Point-to-point,linear,ring,or mesh topology

Protection in 50 seconds Protection in 50 milliseconds or less

simple management complex management

Has Limited scalability Contains 254 nodes per ring,multiple rings

SONET RPR

Has Manual topology Confg Auto-topology config.

16 nodes per ring 254 nodes ring

management bandwidth is fixed Time division multiplexing

Management bandwidth used as needed Statistical multiplexing

Has Manual provisioning of bandwidth and routes

Manual or dynamic provisioning

No service class awareness Differentiated services in eight classes

Fixed direction traffic routing

Least-cost traffic routing

Technical aspects of RPR

Multicast packet can be transmitted around the ring andcan be received by multiple nodes. Mesh topologies requires multicast packets

to be replicated over all possible paths,wasting bandwidth.

Spatial Reuse RPR has the ability to switch traffic over multiple spans of the rings simultaneously

Bandwidth on a particular span between ring nodes is utilized async.Fairness

most important features in carrier-class networks RPR protocol can guarantee fairness

across the metropolitan network.

Quality of Service• is required in order to let a carrier effectively charge for the services it provides.• ATM promised to deliver multiple services due to its rich QoS set.several parameters govern the characteristics of a delivered service

• Service availability,• delay,• delay variation and

•RPR Market DevelopmentISP Network

RPR solutions are helping ISPs todeliver reliable internet services (such and IP and video) andaddress the growing bandwidth service requirements for the next generation intra-point of presence (POP),

• exchange point, • and server frame/storage applications.

Regional Metro Network. RPR regional metro solutions are available for transport

• over dark fiber,• over wavelength division multiplexing (WDM), and • over SONET• cable, and • enterprise/campus MANs

Metro Access Networksprovide direct Ethernet connectivity for

multi-tenant/multidwelling customers and edge programmability.

        Packets-optimized, Layer-1 independent protocol that allows transport, switching and

routing functions in a single platform.

      Provides  Differentiated data services, with advanced QoS mechanisms.

        Provides Point-to-point and multipoint services.

Benefits of RPR

Provides End-to-end networking through a standard,

        Maximum utilization of the fiber bandwidth

Faster deployment of services.

   Ease of provisioning and management of the ring.

     

Main objectives of RPR

enable a true alternative to SONET providing carriers with resiliency fast protection and restoration and performance monitoring designed to combine SONET strengths of

high availability reliability and TDM services support,

superior bandwidth utilization and

high service granularity characteristics.

Conclusion

RPR is reliable, efficient

promoted and standardized by industry leaders- as well as by innovative startup companies,

positioned to take a major role in deployment of next generation carrier-class networks.

References

Data Networks by Dimitri Bertsekas and Robert Gallagar.

Computer Networks by Andrew .S. and Taneabaum.

Computer Network – A system approach by

Larry.L.Petterson and Bruces David.