03-03-2011, 02:32 PM
presented by:
Anusha P Vijayan
[attachment=9450]
RPR Introduction
Packet based ring network for Metropolitan Area Networks (MANs)
Support up to 255 station attachments
Optimized for rings with maximum circumference of 2000 kilometers
SONET in MAN
SONET is designed for point-to-point, circuit-switched applications
Some of the disadvantages are
Fixed Circuits
Wasted Bandwidth for Meshing
Multicast Traffic
Wasted Protected Bandwidth
Ethernet in MAN
Ethernet over a ring
Make efficient use of available bandwidth
Far simpler and inexpensive solution for data
Optimized for point-to-point or meshed topologies
Disadvantages
Not take advantage of ring topology to implement fast protection mechanism
Slow recovery from fiber cuts
No global fairness policy
RPR Operation
Uses a dual counter rotating fiber ring topology
Utilizes the total available ring bandwidth
The fibers or ringlets are used to carry the control messages
RPR has the ability to differentiate between low and high priority packets
The RPR MAC
The MAC layer contains much of the functionality for the RPR network
It is responsible for providing access to the fiber media
It can receive, transit and transmit packets
MAC Frame format
Advantages of Packet Ring
Each node can assume that a packet sent on the ring will eventually reach it’s destination node regardless of the path taken
Only three basic packet-handling actions are needed:
Insertion
Forwarding
Stripping
Reduces the amount of work individual nodes have to do
RPR Characteristics
Resiliency
Bandwidth fairness
Broadcast or multicast traffic
Physical layer versatility
Resiliency
Ring built using switches needs to distribute failure information across an entire network to recover fully from fiber cuts
Packet ring protocol can use a “ring wrap” at the nodes surrounding the cut
Ring failure is often described as “self healing” or “automatic recovery”
Bandwidth Fairness
Implement fairness algorithms to regulate bandwidth usage
A fairness algorithm is a mechanism that gives every node on the ring a predetermined “fair” share of the ring bandwidth
A ring level fairness algorithm can and should allocate ring bandwidth as one global source
Broadcast or Multicast Traffic
Packet rings are natural fit for the broadcast and multicast traffic.
Physical layer versatility
Packet ring standards in development create only a new MAC addressing scheme, that has the advantage of leaving layer 1 open
Packet ring technologies will be compatible with Ethernet, SONET and DWDM physical layer standards
A dark fiber is available, a packet ring can operate without the need to purchase expensive layer 1 gear
Disadvantages of RPR
Higher system cost due to the additional MAC layer
Without a cross-ring standard, RPR information cannot be transferred from one ring to another
RPR uses a shared access mode, and has only one layer of MAC address forwarding. Therefore, network and service expansibility is somewhat limited.
Packet rings in application
Packet rings suit the needs of many types of service providers in the metro area
A single packet ring serves the needs of multiple buildings in a metro area
This solution has several notable features
1. the packet ring at the centre of this solution will allow the service provider to sell true protected bandwidth to the end users
2. Prevent any single node “starving” other nodes
3. Small form-factor packet ring routers will mean mode equipment that can easily fit into existing configured spaces
4. The presented solution demonstrates a healthy integration of Ethernet and packet ring technologies
Standardization
Some of the goals of the 802.17 working groups are:
1) Support for dual counter rotating ring topology
2) Full compatibility with IEEE’s 802 architecture as well as 802.1D,802.1Q and 802.1f
3) Protection mechanism with sub 50ms fail-over
4) Destination stripping of packets
5) Adoption of existing physical layer medium to avoid technical risk
Conclusion
RPR is a MAC protocol and operates at Layer 2 of the OSI protocol stack
By design RPR is a Layer 1 agnostic, which means that RPR can run over either SONET or Ethernet
RPR enables service providers to build more scalable and efficient metro networks using SONET or Ethernet as physical layers
The time is ripe for a transport technology that both fully exploits the potential of ring networking and is also easy to integrate with existing Ethernet and SONET
Anusha P Vijayan
[attachment=9450]
RPR Introduction
Packet based ring network for Metropolitan Area Networks (MANs)
Support up to 255 station attachments
Optimized for rings with maximum circumference of 2000 kilometers
SONET in MAN
SONET is designed for point-to-point, circuit-switched applications
Some of the disadvantages are
Fixed Circuits
Wasted Bandwidth for Meshing
Multicast Traffic
Wasted Protected Bandwidth
Ethernet in MAN
Ethernet over a ring
Make efficient use of available bandwidth
Far simpler and inexpensive solution for data
Optimized for point-to-point or meshed topologies
Disadvantages
Not take advantage of ring topology to implement fast protection mechanism
Slow recovery from fiber cuts
No global fairness policy
RPR Operation
Uses a dual counter rotating fiber ring topology
Utilizes the total available ring bandwidth
The fibers or ringlets are used to carry the control messages
RPR has the ability to differentiate between low and high priority packets
The RPR MAC
The MAC layer contains much of the functionality for the RPR network
It is responsible for providing access to the fiber media
It can receive, transit and transmit packets
MAC Frame format
Advantages of Packet Ring
Each node can assume that a packet sent on the ring will eventually reach it’s destination node regardless of the path taken
Only three basic packet-handling actions are needed:
Insertion
Forwarding
Stripping
Reduces the amount of work individual nodes have to do
RPR Characteristics
Resiliency
Bandwidth fairness
Broadcast or multicast traffic
Physical layer versatility
Resiliency
Ring built using switches needs to distribute failure information across an entire network to recover fully from fiber cuts
Packet ring protocol can use a “ring wrap” at the nodes surrounding the cut
Ring failure is often described as “self healing” or “automatic recovery”
Bandwidth Fairness
Implement fairness algorithms to regulate bandwidth usage
A fairness algorithm is a mechanism that gives every node on the ring a predetermined “fair” share of the ring bandwidth
A ring level fairness algorithm can and should allocate ring bandwidth as one global source
Broadcast or Multicast Traffic
Packet rings are natural fit for the broadcast and multicast traffic.
Physical layer versatility
Packet ring standards in development create only a new MAC addressing scheme, that has the advantage of leaving layer 1 open
Packet ring technologies will be compatible with Ethernet, SONET and DWDM physical layer standards
A dark fiber is available, a packet ring can operate without the need to purchase expensive layer 1 gear
Disadvantages of RPR
Higher system cost due to the additional MAC layer
Without a cross-ring standard, RPR information cannot be transferred from one ring to another
RPR uses a shared access mode, and has only one layer of MAC address forwarding. Therefore, network and service expansibility is somewhat limited.
Packet rings in application
Packet rings suit the needs of many types of service providers in the metro area
A single packet ring serves the needs of multiple buildings in a metro area
This solution has several notable features
1. the packet ring at the centre of this solution will allow the service provider to sell true protected bandwidth to the end users
2. Prevent any single node “starving” other nodes
3. Small form-factor packet ring routers will mean mode equipment that can easily fit into existing configured spaces
4. The presented solution demonstrates a healthy integration of Ethernet and packet ring technologies
Standardization
Some of the goals of the 802.17 working groups are:
1) Support for dual counter rotating ring topology
2) Full compatibility with IEEE’s 802 architecture as well as 802.1D,802.1Q and 802.1f
3) Protection mechanism with sub 50ms fail-over
4) Destination stripping of packets
5) Adoption of existing physical layer medium to avoid technical risk
Conclusion
RPR is a MAC protocol and operates at Layer 2 of the OSI protocol stack
By design RPR is a Layer 1 agnostic, which means that RPR can run over either SONET or Ethernet
RPR enables service providers to build more scalable and efficient metro networks using SONET or Ethernet as physical layers
The time is ripe for a transport technology that both fully exploits the potential of ring networking and is also easy to integrate with existing Ethernet and SONET
