Spatial Reuse in Network Topology

RPR Technology

• RPR (Resilient Packet Ring) technology uses a dual counter-rotating fiber ring topology to transport working traffic between nodes.
• Both rings (inner and outer) are used to transport traffic, utilizing the total available ring bandwidth.
• Control messages for topology updates, protection, and bandwidth control are carried on the ring, flowing in the opposite direction of the traffic they represent.
• RPR nodes can dynamically negotiate for bandwidth with other nodes on the ring.
• RPR has the capability to differentiate between low and high-priority traffic and can transmit high-priority packets before those of low priority.

RPR Operation

• RPR nodes have a transit path, through which packets destined to downstream nodes on the ring flow.
• RPR nodes have a transit buffer that can hold multiple packets, allowing them to transmit higher-priority packets while temporarily holding other lower-priority packets.
• There is no master node on the ring; bandwidth management and congestion control are fully distributed over all nodes.
• Each node processes three traffic streams: exit traffic, ingress traffic, and transit traffic.
• Nodes ensure that ingress and transit traffic don't interfere with each other's QoS and share the ring resources fairly to avoid congestion.

Receive Decision

• Every station has a 48-bit MAC address.
• Nodes only receive packets with a matching MAC destination address.
• Multicast packets are copied to the host and allowed to continue through the transit path, while unicast packets are stripped from the ring and do not consume bandwidth on downstream spans.
• Control packets may not need a destination or source address.

Transit Path

• Nodes with a non-matching destination address are allowed to continue circulating around the ring.
• RPR packets undergo minimal processing per hop on a ring, with only a matching address and header errors being inspected.

Transmit and Bandwidth Control

• The RPR MAC can transmit both high and low-priority packets.
• The bandwidth control algorithm ensures that nodes are not disadvantaged due to their location on the ring or changing traffic patterns, and only manages congestion, enabling nodes to maximize the use of any spare capacity.

Topology Discovery

• RPR has a topology discovery mechanism that allows nodes on the ring to be inserted or removed without manual management intervention.
• Nodes circulate a topology discovery message to learn the MAC addresses of other stations on the ring.
• Each node that receives a topology message appends its MAC address and passes it to its neighbor, eventually creating a topology map of the ring.

Protection

• RPR has the ability to protect the network from single span (node or fiber) failures.
• Two protection mechanisms are available: wrapping and steering.
• Wrapping involves moving packets away from the failed span by wrapping traffic around to the other fiber (ringlet), requiring only two nodes to participate in the protection event.
• Steering notifies all nodes on the ring of the failed span.

MNG-PAN Network

• BSNL deployed MNG-PAN Aggregation Network in 15 cities, with 421 PAN-COAU and 287 OC-PAN switches.
• The deployment architecture of MNG-PAN and OC-PAN involves the OC-PAN ring aggregating traffic from all nodes and handing it over to the upper MNG-PAN ring.
• The Central Office Aggregation Unit (COAU) switch of the PAN ring aggregates traffic from all PAN nodes and hands it over to the IP-MPLS core.

Features of MNG-PAN Network

• The solution is based on Pseudo Wire over MPLS-TP technology, supporting efficient Ethernet aggregation.
• The PAN platform offers a wide range of protocols, standards, and interfaces, coupled with high reliability.
• Carrier-class features include sub-50ms recovery resiliency, hard QoS/SLA guarantees, end-to-end and multi-layer OAM, network-wide time/clock synchronization, and efficient multicast data distribution.
• Range of interfaces up to 10GE, low power consumption, and centralized management are also available.

Advantages of MNG-PAN Transport Network

• Scalability: Support of electrical and optical Ethernet interfaces from FE to 10GE, with large switching capacity.
• Reliability: Carrier-class reliability with fully redundant hardware architecture.
• Resilience: Various protection schemes, sub-50ms failure recovery.
• Manageability: Enhanced OAM capability with end-to-end service management, and NMS-based operation.
• Inter-operability: Compliant with ITU-T MPLS-TP standard, with easy integration with core IP/MPLS or OTN networks.
• Bandwidth Efficiency: Packet nature of the network with flexible data-pipes enables users to request service in smaller increments and provides better utilization at the aggregation level.
• Lower TCO: Low power consumption, bandwidth efficiency, fast fault isolation, and simple management, resulting in a smaller form factor.