Resilient Packet Ring
Encyclopedia
Resilient Packet Ring also known as IEEE 802.17, is a standard designed for the optimized transport of data traffic over optical fiber ring networks. It is designed to provide the resilience
found in SONET
/SDH networks (50 ms protection) but, instead of setting up circuit oriented connections, provides a packet based transmission, in order to increase the efficiency of Ethernet
and IP
services.
RPR works on a concept of dual counter rotating rings called ringlets. These ringlets are set up by creating RPR stations at nodes where traffic is supposed to drop, per flow (a flow is the ingress and egress of data traffic). RPR uses Media Access Control
protocol (MAC) messages to direct the traffic, which can use either ringlet of the ring. The nodes also negotiate for bandwidth among themselves using fairness algorithms, avoiding congestion and failed spans. The avoidance of failed spans is accomplished by using one of two techniques known as steering and wrapping. Under steering, if a node or span is broken, all nodes are notified of a topology change and they reroute their traffic. In wrapping, the traffic is looped back at the last node prior to the break and routed to the destination station.
All traffic on the ring is assigned a Class of Service
(CoS) and the standard specifies three classes. Class A (or High) traffic is a pure committed information rate (CIR) and is designed to support applications requiring low latency and jitter, such as voice and video. Class B (or Medium) traffic is a mix of both a CIR and an excess information rate (EIR; which is subject to fairness queuing). Class C (or Low) is best effort traffic, utilizing whatever bandwidth is available. This is primarily used to support Internet access traffic.
Another concept within RPR is what is known as spatial reuse. Because RPR strips the signal once it reaches the destination (unlike a SONET UPSR/SDH SNCP
ring, in which the bandwidth is consumed around the entire ring) it can reuse the freed space to carry additional traffic. The RPR standard also supports the use of learning bridges (IEEE 802.1D
) to further enhance efficiency in point to multipoint applications and VLAN tagging (IEEE 802.1Q
).
One drawback of the first version of RPR was that it didn't provide spatial reuse for frame transmission to/from MAC addresses not present in the ring topology. This was addressed by IEEE 802.17b, which defines an optional spatially aware sublayer (SAS). This allows spatial reuse for frame transmission to/from MAC address not present in the ring topology.
Resilience (network)
In computer networking: “Resilience is the ability to provide and maintain an acceptable level of service in the face of faults and challenges to normal operation.”These services include:* supporting distributed processing* supporting networked storage...
found in SONET
Sonet
Sonet may refer to:* Sonet Records, European record label* Synchronous optical networking * Saab Sonett...
/SDH networks (50 ms protection) but, instead of setting up circuit oriented connections, provides a packet based transmission, in order to increase the efficiency of Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
and IP
Internet Protocol
The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
services.
RPR works on a concept of dual counter rotating rings called ringlets. These ringlets are set up by creating RPR stations at nodes where traffic is supposed to drop, per flow (a flow is the ingress and egress of data traffic). RPR uses Media Access Control
Media Access Control
The media access control data communication protocol sub-layer, also known as the medium access control, is a sublayer of the data link layer specified in the seven-layer OSI model , and in the four-layer TCP/IP model...
protocol (MAC) messages to direct the traffic, which can use either ringlet of the ring. The nodes also negotiate for bandwidth among themselves using fairness algorithms, avoiding congestion and failed spans. The avoidance of failed spans is accomplished by using one of two techniques known as steering and wrapping. Under steering, if a node or span is broken, all nodes are notified of a topology change and they reroute their traffic. In wrapping, the traffic is looped back at the last node prior to the break and routed to the destination station.
All traffic on the ring is assigned a Class of Service
Class of service
-Class of service :As related to network technology, CoS is a 3-bit field within an Ethernet frame header when using 802.1Q tagging. The field specifies a priority value of between 0 and 7 inclusive that can be used by quality of service disciplines to differentiate traffic.While CoS operates only...
(CoS) and the standard specifies three classes. Class A (or High) traffic is a pure committed information rate (CIR) and is designed to support applications requiring low latency and jitter, such as voice and video. Class B (or Medium) traffic is a mix of both a CIR and an excess information rate (EIR; which is subject to fairness queuing). Class C (or Low) is best effort traffic, utilizing whatever bandwidth is available. This is primarily used to support Internet access traffic.
Another concept within RPR is what is known as spatial reuse. Because RPR strips the signal once it reaches the destination (unlike a SONET UPSR/SDH SNCP
Subnetwork Connection Protection
In telecommunications, subnetwork connection protection, or SNCP, is a type of protection mechanism associated with synchronous optical networks such as synchronous digital hierarchy....
ring, in which the bandwidth is consumed around the entire ring) it can reuse the freed space to carry additional traffic. The RPR standard also supports the use of learning bridges (IEEE 802.1D
IEEE 802.1D
802.1D is the IEEE MAC Bridges standard which includes Bridging, Spanning Tree and others. It is standardized by the IEEE 802.1 working group. It includes details specific to linking many of the other 802 projects including the widely deployed 802.3 , 802.11 and 802.16 standards.VLANs are not...
) to further enhance efficiency in point to multipoint applications and VLAN tagging (IEEE 802.1Q
IEEE 802.1Q
IEEE 802.1Q is the networking standard that supports Virtual LANs on an Ethernet network. The standard defines a system of VLAN tagging for Ethernet frames and the accompanying procedures to be used by bridges and switches in handling such frames...
).
One drawback of the first version of RPR was that it didn't provide spatial reuse for frame transmission to/from MAC addresses not present in the ring topology. This was addressed by IEEE 802.17b, which defines an optional spatially aware sublayer (SAS). This allows spatial reuse for frame transmission to/from MAC address not present in the ring topology.
See also
- Spatial Reuse ProtocolSpatial Reuse ProtocolSpatial Reuse Protocol is a networking protocol developed by Cisco. It is a MAC-layer protocol for ring-based packet internetworking that is commonly used in optical fiber ring networks...
(CiscoCiscoCisco may refer to:Companies:*Cisco Systems, a computer networking company* Certis CISCO, corporatised entity of the former Commercial and Industrial Security Corporation in Singapore...
) - Metro Ring ProtocolMetro Ring ProtocolThe Metro Ring Protocol is a Layer 2 resilience protocol developed by Foundry Networks and currently being delivered in products manufactured by Brocade Communications Systems and Hewlett Packard...
(FoundryFoundryA foundry is a factory that produces metal castings. Metals are cast into shapes by melting them into a liquid, pouring the metal in a mold, and removing the mold material or casting after the metal has solidified as it cools. The most common metals processed are aluminum and cast iron...
) - Open Transport NetworkOpen Transport NetworkOpen Transport Network is a flexible private communication network, based on the fiber optic technology . It is a brand name and not to be mistaken with Optical Transport Network. It is a networking technology that aims at transporting a number of communication protocols over an optical fiber and...
(Nokia Siemens NetworksNokia Siemens NetworksNokia Siemens Networks is a global data networking and telecommunications equipment company headquartered in Espoo, Finland. It is a joint venture between Nokia of Finland and Siemens of Germany...
) - Dynamic Packet TransportDynamic Packet TransportDynamic packet transport is a Cisco transport protocol designed for use in optical fiber ring networks. In overview, it is quite similar to POS and DTM. It was one of the major influences on the Resilient Packet Ring/802.17 standard.-Protocol Design:...
(CiscoCiscoCisco may refer to:Companies:*Cisco Systems, a computer networking company* Certis CISCO, corporatised entity of the former Commercial and Industrial Security Corporation in Singapore...
) - Ethernet Ring Protection SwitchingERPSEthernet Ring Protection Switching, or ERPS, is an effort at ITU-T under G.8032 Recommendation to provide sub-50ms protection and recovery switching for Ethernet traffic in a ring topology and at the same time ensuring that there are no loops formed at the Ethernet layer...
(ITU-TITU-TThe ITU Telecommunication Standardization Sector is one of the three sectors of the International Telecommunication Union ; it coordinates standards for telecommunications....
)