Deploying Multiservice Applications Using RPR Over the Existing SONET Infrastructure Introduction The migration of Ethernet technology from the LAN to metro networks, driven by increasing demand in VoIP,data and video traffic, makes metro Ethernet service one of the most promising networking opportunities. However, due to lack of resiliency in native Ethernet features and current economic conditions, service providers are looking at deploying Ethernet services over their existing, proven and reliable SONET infrastructure with the new, emerging, data friendly, next-generation SONET technologies such as GFP,VCAT and RPR.This paper discusses why these emerging technologies over SONET are attractive to provide metro Ethernet services, how these technologies can be used to deploy Ethernet and what services can be offered. Metro Ethernet Service On The Rise Service providers have increased their CAPEX spending on network transport equipment with Ethernet interfaces to meet growing customer demand for IP and Ethernet services to carry voice, data and video traffic via the metro network.The metro Ethernet equipment market will have a more than 50% CAGR from 2003 to 2008 according to recently published reports. Ethernet was initially developed as a LAN technology.The biggest challenge in deploying Ethernet service in the MAN or WAN is how to offer carrier-class features with a more reliable and manageable solution than Ethernet running in the LAN environment. Many standards bodies, including the IEEE, ITU, IETF and MEF,are working to define new capabilities to make Ethernet services as reliable as traditional TDM services. For example, issues are being addressed to provide faster protected switching with better performance monitoring, troubleshooting, and improved OAM features. Ethernet, which offers higher bandwidth at a lower price per bit, is a simpler protocol and has been deployed for years in the LAN. Ethernet provides a cost-effective, common interface to deliver different services. Service providers plan to offer more IP and Ethernet related services, including Internet access, Wi-Fi, IP VPN, IP telephony,VoD and remote storage. Most of the Ethernet services offered today are either private line service-based (point-to-point) or transparent LAN service-based with best-effort class of service only.With the advancement of Ethernet standards and new emerging services, service providers will begin to roll out classes of service- differentiated offerings supported with SLAs. Also, service providers are moving toward traffic aggregation and switched Ethernet transport to optimize network bandwidth and resources rather than simply providing point-to-point Ethernet transport. A carrier-class Ethernet access technology that can carry multiservice traffic with Layer 2 switching capabilities, SLAs, QoS guarantees and traffic prioritization is highly desirable. FUJITSU NETWORK COMMUNICATIONS INC. For your convenience, a list of acronyms can be found at the end of this document. 2801 Telecom Parkway, Richardson, Texas 75082-3515 1 Telephone: (972) 690-6000 (800) 777-FAST (U.S.) us.fujitsu.com/telecom One of the most promising access technologies is RPR. RPR is designed to provide carrier-class features to transport customer traffic via a shared media ring with multiple service classes. Proprietary versions of RPR have previously been available, but the recent IEEE 802.17 RPR ratification has created an industry standard. This standardization will help to improve interoperability and drive down equipment cost. Standardization of RPR also encourages more service providers, equipment vendors and chip manufacturers to enter the RPR market. What is RPR? RPR consists of two counter-rotating rings called inner and outer ringlets. Packet traffic travels in one direction in one ringlet and in the opposite direction in another ringlet. Unicast packets are stripped from the ring by the destination RPR station. Multicast and broadcast packets are stripped from the ring by the source station, copied into target receiver stations and continue downstream.The stations on the ring can automatically negotiate for bandwidth among themselves via a fairness algorithm. Each station has a topology map of the ring and can send data on the optimal ringlet towards its destination. Both ringlets can be used to carry working traffic.The protection algorithm avoids failed spans to protect against fiber station failure. RPR is a MAC layer protocol and can be carried over different physical media. Key features include: Class of Service One of the key features in the RPR specification provides class of service to support multiservice traffic with different delay and jitter characteristics.Three classes of service are defined for RPR MAC: high, medium and low. The high-priority class supports strictly bounded delay and jitter applications such as VoIP and real-time video applications with non-preemptive bandwidth guarantees. The medium-priority class supports applications that are less sensitive to delay and jitter such as non-real-time video and VPN services. User-provisioned CIR and EIR guarantees are supported for different service requirements. The low-priority class of service supports best-effort applications that do not need bandwidth guarantees such as consumer Internet access. With three unique classes of service, service providers can offer differentiated Ethernet services with different price points to satisfy different customer requirements. Spatial Reuse Removing the packet from the ring by the destination station provides spatial reuse of the ring bandwidth since the path between the source and destination RPR stations only belongs to part of the total ring length. FUJITSU NETWORK COMMUNICATIONS INC. 2801 Telecom Parkway, Richardson, Texas 75082-3515 2 Telephone: (972) 690-6000 (800) 777-FAST (U.S.) us.fujitsu.com/telecom Fairness Algorithm The fairness algorithm is important for resource allocation, ensuring the fairness-eligible traffic has fair access to the ring bandwidth.The fairness-eligible traffic is low-priority or excess traffic in the medium- priority class and the fairness algorithm regulates this traffic.The goal is to inject as much traffic into the ring for best utilization, without violating the SLA. Protection RPR has a dual ringlet.Two paths always exist between any two nodes in the ring so if a span in one ringlet fails, traffic can be automatically switched into another path within 50 ms. Why use RPR and what are the challenges? RPR is a distributed switch, peer-to-peer architecture.The most significant economic impact RPR offers is in driving down the CAPEX savings by maximizing the bandwidth utilization in the network. RPR provides a high-capacity gain by sharing the entire ring bandwidth with all the RPR stations that belong to the ring. Therefore, RPR simplifies the network architecture and reduces the network equipment used.The major challenge for RPR is that the technology is still new so interoperability and management support can be an issue. Most of the incumbent service providers’ OSSs are circuit-based for point-to-point circuits so enhancements are needed to support a shared multi-point solution such as RPR. Why RPR over SONET? RPR was originally designed as a possible alternative to SONET. Special attention was given in the standard to ensure that RPR provided a SONET-like sub-50 ms resiliency. RPR uses packet-switching technology while SONET uses TDM technology to add and drop traffic from nodes in ring topologies. But SONET is still the dominant transport infrastructure and has a large installed base. Replacing embedded SONET networks with any new architecture is not feasible under current economic conditions.The slow down of the North American telecommunication industry and the cost pressures faced by carriers are contributing to the viability of SONET for today's transport network. So instead of replacing SONET with RPR, service providers plan to deploy RPR over SONET and equipment vendors are working to integrate RPR functionality into their MSPPs. MSPPs provide an optimized, cost-saving solution to consolidate video, data and voice services on the existing SONET-based network infrastructure. Running RPR over SONET gives service providers efficiency in supporting Ethernet while continuing to run TDM services (DS1, DS3, OC-N) over the remaining SONET capacity. RPR and other SONET architectures such as UPSR can co-exist on the same ring. For example, in Figure 1, the OC-48 SONET ring is running a STS-24 RPR ring for data service with the other half of ring bandwidth used for traditional TDM services. So, part of the ring bandwidth can be used to run TDM service with UPSR or BLSR protection and the other ring bandwidth can be used to run data or video traffic using an RPR layer of protection. FUJITSU NETWORK COMMUNICATIONS INC. 2801 Telecom Parkway, Richardson, Texas 75082-3515 3 Telephone: (972) 690-6000 (800) 777-FAST (U.S.) us.fujitsu.com/telecom P, RPR MSP n Statio ernet, Eth S1, DS3, D OC-n 1, DS3, DS OC-n ing DM ONET R P/A over S MSP RPR OC-48 1, DS3, DS OC-n DM MSPP/A Ring et, 24 RPR Ethern STS- TDM , DS1, 24 for ernet, DS3 STS- Eth S1, OC-n DS3, D OC-n P, RPR MSP ns Statio Figure 1: RPR Shared Path Over Existing SONET Transport of data or digital video over SONET has traditionally been problematic due to the inefficient manner tha because nonet da ofta the or currentvideo is data mapp or video interface standards was designed for WAN transport.VCAT with point-to-point EoS solutions has reduced this inefficiency