03-03-2011, 12:55 PM
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1. INTRODUCTION
Over the fast few years, new promising protocols have emerged at the forefront of Metro Networking. One among them is the Resilient Packet Ring Technology (RPR). Today, as the standards slowly settle, it is finally reaching the stage beyond specification, and into network deployment.
RPR is a MAC layer technology standardized by the IEEE 802.17 workgroup. It is independent of the physical layer and can run on SONET/SDH, Ethernet and Dense Wavelength Division Multiplexing.
Integrating the high reliability of SDH self-healing and Ethernet advantages such as low cost, large bandwidth, flexibility, and scalability, the RPR technology provides bandwidth management with data optimization capability and high performance multiservice transmission on a ring topology. RPR technology, on their own, adds features to Metro Area Networks that are currently lacking.
2. RPR TECHNOLOGY
The rapidly increasing volume of data traffic in metro networks is challenging the capacity limits of existing transport infrastructures that are based on circuit-oriented technologies like SONET and ATM. Packet-based transport technology is considered by many to be the likely alternative for scaling metro networks to meet traffic demands.
2.1. Overview of RPR Technology
RPR Technology is an emerging solution for metro data transport applications that can fully exploit fiber rings. It retains all the inherent advantages of a packet-based transport mechanism like Ethernet. This latest technology is suitable for data, voice, and video applications. The adoption of RPR technology is particularly critical to handle the rapid growth of data traffic in metropolitan networks.
RPR technology reduces operational and equipment costs, increases resiliency to faults and provides higher throughput, while allowing for rapid deployment and efficient bandwidth allocation. RPR technology is being designed specifically for metropolitan area networks of fiber optic rings and will be an important part of new metropolitan data networks. This new protocol will allow metropolitan area service providers to create high-speed, survivable ring networks optimized for IP and other packet data.
Structure Overview
RPR is a reciprocal dual-ring topology, with each optical span working at the same rate. The difference is that both the two rings of RPR can transmit data. These two rings are referred to as Ringlet0 and Ringlet1 respectively.
Data are transmitted clockwise on Ringlet0 while anti-clockwise on Ringlet1.
Each RPR station uses a 48-bit MAC address used in Ethernet as its address ID. From the perspective of the page link layer of the RPR station, these two pairs of physical optical ports of transmission/reception are only one page link layer interface. From the perspective of the network layer, only one IP address needs to be allocated.
The page link between two adjacent RPR stations is refereed to as a span, and multiple continuous spans and the stations on them constitute a domain.
From the perspective of a station, its packet switching structure has changed immensely in comparison with the traditional packet switching structure.
This structure is similar to the ring road of a city, where the stations on the ring are directly connected, with barely any traffic lights needed, and hence higher efficiency. One RPR station has one MAC entity and two physical layer entities. The physical layer entities are associated with the links. Referred to as the access point, the MAC entity includes one MAC control entity and two MAC service page link entities. Each access point is associated with a loop. By direction, physical layer entities are divided into east physical layer and west physical layer. The east and west are based on the assumption that the station is to the north of RPR. The “Tx interface” of the east physical layer and the “Rx interface” of the west physical layer are connected via the MAC entity into the Ringlet0 of RPR. Similarly, the “Rx interface” of the east physical layer and the “Tx interface” of the west physical layer are connected into the Ringlet1 of RPR.
2.2. Key Features of RPR Technology
• Efficient support for ring topology.
• Increases resiliency to faults and provides higher throughput. Fast recovery from fiber cuts and page link failures.
• Data efficiency, simplicity, and cost advantages.
• Problems such as fairness and congestion control solved.
• Efficient bandwidth allocation.
2.3. Basic Ring Operation
Resilient Packet Rings (RPR) are data optimized networks, with at least two counter-rotating fiber ringlets in which multiple nodes share the bandwidth without the requirement of provisioning circuits.
In agreement with the ring, the stations are designed with ADM data switching for various data operations. Common basic data operations are:
Insert: It is the process that the station equipment inserts the packets forwarded from other interfaces into the data stream of the RPR ring;
Copy: It is the process that the station equipment receives data from the data stream of the RPR ring and gives them to the upper layer for processing;
Transit: It is the process that the data stream passing a station is forwarded to the next station;
Strip: It is the process that the data passing a station is stopped from further forwarding.
The data operation for “transit” is similar to that of the SDH ADM equipment, in that the “transit” data streams are not processed by the upper-layer equipment, which greatly enhances the processing performance of the equipment. Such ADM switching of packets can easily support various high-speed page link interfaces.
The stations use one or any combination of these basic data operations to implement unicast, multicast and broadcast traffic.
1. INTRODUCTION
Over the fast few years, new promising protocols have emerged at the forefront of Metro Networking. One among them is the Resilient Packet Ring Technology (RPR). Today, as the standards slowly settle, it is finally reaching the stage beyond specification, and into network deployment.
RPR is a MAC layer technology standardized by the IEEE 802.17 workgroup. It is independent of the physical layer and can run on SONET/SDH, Ethernet and Dense Wavelength Division Multiplexing.
Integrating the high reliability of SDH self-healing and Ethernet advantages such as low cost, large bandwidth, flexibility, and scalability, the RPR technology provides bandwidth management with data optimization capability and high performance multiservice transmission on a ring topology. RPR technology, on their own, adds features to Metro Area Networks that are currently lacking.
2. RPR TECHNOLOGY
The rapidly increasing volume of data traffic in metro networks is challenging the capacity limits of existing transport infrastructures that are based on circuit-oriented technologies like SONET and ATM. Packet-based transport technology is considered by many to be the likely alternative for scaling metro networks to meet traffic demands.
2.1. Overview of RPR Technology
RPR Technology is an emerging solution for metro data transport applications that can fully exploit fiber rings. It retains all the inherent advantages of a packet-based transport mechanism like Ethernet. This latest technology is suitable for data, voice, and video applications. The adoption of RPR technology is particularly critical to handle the rapid growth of data traffic in metropolitan networks.
RPR technology reduces operational and equipment costs, increases resiliency to faults and provides higher throughput, while allowing for rapid deployment and efficient bandwidth allocation. RPR technology is being designed specifically for metropolitan area networks of fiber optic rings and will be an important part of new metropolitan data networks. This new protocol will allow metropolitan area service providers to create high-speed, survivable ring networks optimized for IP and other packet data.
Structure Overview
RPR is a reciprocal dual-ring topology, with each optical span working at the same rate. The difference is that both the two rings of RPR can transmit data. These two rings are referred to as Ringlet0 and Ringlet1 respectively.
Data are transmitted clockwise on Ringlet0 while anti-clockwise on Ringlet1.
Each RPR station uses a 48-bit MAC address used in Ethernet as its address ID. From the perspective of the page link layer of the RPR station, these two pairs of physical optical ports of transmission/reception are only one page link layer interface. From the perspective of the network layer, only one IP address needs to be allocated.
The page link between two adjacent RPR stations is refereed to as a span, and multiple continuous spans and the stations on them constitute a domain.
From the perspective of a station, its packet switching structure has changed immensely in comparison with the traditional packet switching structure.
This structure is similar to the ring road of a city, where the stations on the ring are directly connected, with barely any traffic lights needed, and hence higher efficiency. One RPR station has one MAC entity and two physical layer entities. The physical layer entities are associated with the links. Referred to as the access point, the MAC entity includes one MAC control entity and two MAC service page link entities. Each access point is associated with a loop. By direction, physical layer entities are divided into east physical layer and west physical layer. The east and west are based on the assumption that the station is to the north of RPR. The “Tx interface” of the east physical layer and the “Rx interface” of the west physical layer are connected via the MAC entity into the Ringlet0 of RPR. Similarly, the “Rx interface” of the east physical layer and the “Tx interface” of the west physical layer are connected into the Ringlet1 of RPR.
2.2. Key Features of RPR Technology
• Efficient support for ring topology.
• Increases resiliency to faults and provides higher throughput. Fast recovery from fiber cuts and page link failures.
• Data efficiency, simplicity, and cost advantages.
• Problems such as fairness and congestion control solved.
• Efficient bandwidth allocation.
2.3. Basic Ring Operation
Resilient Packet Rings (RPR) are data optimized networks, with at least two counter-rotating fiber ringlets in which multiple nodes share the bandwidth without the requirement of provisioning circuits.
In agreement with the ring, the stations are designed with ADM data switching for various data operations. Common basic data operations are:
Insert: It is the process that the station equipment inserts the packets forwarded from other interfaces into the data stream of the RPR ring;
Copy: It is the process that the station equipment receives data from the data stream of the RPR ring and gives them to the upper layer for processing;
Transit: It is the process that the data stream passing a station is forwarded to the next station;
Strip: It is the process that the data passing a station is stopped from further forwarding.
The data operation for “transit” is similar to that of the SDH ADM equipment, in that the “transit” data streams are not processed by the upper-layer equipment, which greatly enhances the processing performance of the equipment. Such ADM switching of packets can easily support various high-speed page link interfaces.
The stations use one or any combination of these basic data operations to implement unicast, multicast and broadcast traffic.
