How Epsr Works, Epsr Components | Allied Telesis AT-9924T-40

How EPSR Works

EPSR operates on physical rings of switches (note, not on meshed networks). When all nodes and links in the ring are up, EPSR prevents a loop by blocking data transmission across one port. When a node or link fails, EPSR detects the failure rapidly and responds by unblocking the blocked port so that data can flow around the ring.

In EPSR, each ring of switches forms an EPSR domain. One of the domain’s switches is the master node and the others are transit nodes. Each node connects to the ring via two ports.

One or more data VLANs sends data around the ring, and a control VLAN sends EPSR messages. A physical ring can have more than one EPSR domain, but each domain operates as a separate logical group of VLANs and has its own control VLAN and master node.

On the master node, one port is the primary port and the other is the secondary port. When all the nodes in the ring are up, EPSR prevents loops by blocking the data VLAN on the secondary port.

The master node does not need to block any port on the control VLAN because loops never form on the control VLAN. This is because the master node never forwards any EPSR messages that it receives.

The following diagram shows a basic ring with all the switches in the ring up.

	End User Ports
Control VLAN is forwarding										Control VLAN is forwarding
Data VLAN is blocked										Data VLAN is forwarding
	S	P	C	ontr
	S	P		ontr
						ol
				D			V
					at				A
				D		a VL				N
				D				A
					at					N
						a	V			_
							V			1
		Master						L
								A
										N
										_
		Node								2
		Node
End User Ports	Transit			Transit							End User Ports
	Node			Node
	4					1
End User Ports	Transit					Transit					End User Ports
End User Ports	Node					Node					End User Ports
	Node					Node
	3							2
Control VLAN	Control VLAN		Primary Port								P
Data VLAN_1	Data VLAN_1		Primary Port								P
Data VLAN_1	Data VLAN_1		Secondary Port								S
Data VLAN_2	Data VLAN_2		Secondary Port								S
Data VLAN_2	Data VLAN_2
											epsr-basic-ring

EPSR Components

EPSR domain:

A protection scheme for an Ethernet ring that consists of one or more data VLANs and a control VLAN.

Master node:

The controlling node for a domain, responsible for polling the ring state, collecting error messages, and controlling the flow of traffic in the domain.

Transit node:

Other nodes in the domain.

Ring port:

A port that connects the node to the ring. On the master node, each ring port is either the primary port or the secondary port. On transit nodes, ring ports do not have roles.

Primary port:

A ring port on the master node. This port determines the direction of the traffic flow, and is always operational.

Secondary port:

A second ring port on the master node. This port remains active, but blocks all protected VLANs from operating unless the ring fails. Similar to the blocking port in an STP/RSTP instance.

Control VLAN:

The VLAN over which all control messages are sent and received. EPSR never blocks this VLAN.

Data VLAN

A VLAN that needs to be protected from loops. Each EPSR domain has one or more data VLANs.

Page 3 AlliedWare™ OS How To Note: EPSR

AT-9924SP-30, AT-9924T-40, AT-8948, AT-9924T/4SP-A-20, X900-48FE-N specifications

Allied Telesis is a leading provider of networking solutions, renowned for its innovative technologies and high-performance networking equipment. Among its extensive product lineup, the X900-48FE-N, AT-9924T-40, AT-8948, AT-9924T/4SP-A-20, and AT-9924SP-30 stand out for their remarkable features and capabilities.

The X900-48FE-N is a robust layer 2/3 managed switch that features 48 Fast Ethernet ports. This model is particularly known for its energy efficiency and reliability, making it a suitable choice for enterprises with demanding networking needs. It supports a wide range of Layer 2 Ethernet switching technologies, including VLANs, Spanning Tree Protocol (STP), and Link Aggregation Control Protocol (LACP), which enhances network reliability and efficiency.

The AT-9924T-40 is a versatile switch designed for high-performance environments. It offers a rich set of features, including 24 Gigabit Ethernet ports and 4 SFP ports for fiber connectivity. This device is equipped with Advanced Layer 2 and Layer 3 features, including IPv4/IPv6 support, Quality of Service (QoS) capabilities, and robust security options. This switch is ideal for core and distribution deployments within enterprise networks, ensuring fast and reliable connectivity.

The AT-8948 is another important model in Allied Telesis' offerings. It features 48 10/100 Mbps Ethernet ports and 4 Gigabit uplink ports, providing a high density of connectivity options. The AT-8948 is also equipped with advanced management capabilities, including SNMP, RMON, and web-based management, allowing for easy configuration and monitoring of the network.

The AT-9924T/4SP-A-20 offers a combination of 24 Gigabit Ethernet ports and 4 SFP slots to extend network capabilities through fiber connections. It is particularly well-suited for environments requiring high bandwidth and flexible connectivity. Its compact design makes it an excellent choice for data centers and enterprise networks.

Lastly, the AT-9924SP-30 is characterized by its 24 Gigabit SFP ports, offering flexibility in terms of fiber connectivity. This switch supports advanced routing capabilities and is designed for high-availability environments. Its ability to handle diverse network traffic while maintaining optimal performance makes it a valuable asset for any modern enterprise.

In summary, these Allied Telesis models showcase advanced features, network reliability, and versatile management options, making them critical components for efficient and scalable networking solutions.

Allied Telesis AT-9924T-40, X900-48FE-N, AT-9924T/4SP-A-20, AT-8948 How Epsr Works, Epsr Components

Models: AT-9924SP-30 AT-9924T-40 AT-8948 AT-9924T/4SP-A-20 X900-48FE-N