Basic Concepts EISP

To better understand the basic concepts introduced in this section, refer to the legends of the typical topologies of the sub ring mode and hierarchical mode.

1. EIPS domain

An EIPS domain is constructed by interconnected devices with the same domain ID and same control VLAN. It can contain multiple EIPS rings. One is the main ring and the others are the sub rings. An EIPS domain consists of EIPS ring, EIPS control VLAN, master node, transmission node, edge control node, and edge assistant node.

2. EIPS ring

An EIPS ring is identified by an integer ID, physically corresponding to an Ethernet topology in a ring. The EIPS ring includes a main ring and multiple sub rings. A sub ring is intersected with the main ring via the edge node and is intersected with the other sub rings via the main ring. The level of a main ring is 0 and the level of a sub ring is greater than 0.

3. EIPS node

Switches on the EIPS ring are called nodes. Each node has a unique domain ID and ring ID, and is connected to the ring by two ports, one primary port and one secondary port specified by the user.

Master node: initiates the polling of the Ethernet ring status and implements the measures when the network topology status changes. Only one master node is available on a ring.

Transmission node: specifies the nodes excluding the master node on the EIPS main ring. It monitors the status of the link directly connected to the node and reports the status changes to the master node through the EIPS protocol packets. And then, the master node decides how to handle this situation.

The two nodes intersected by the sub ring and the main ring are called edge nodes (also called transmission node on the main ring). Edge nodes include the edge control node and edge assistant node, which should be used in pair to detect the integrity and fault status of the main ring.

4. EIPS control VLAN

A control VLAN is used to transfer the EIPS protocol packets. All ports on the EIPS ring should be configured with control VLANs. The control VLAN interfaces cannot be configured with IP addresses. In the sub ring mode, the ports on the main ring should be added to both the control VLAN of the main ring and the control VLAN of the sub rings, but the ports on the sub ring can only be added to the control VLAN of the sub rings. In the hierarchical mode, the control VLANs can be the same on the main ring and on the low-level links.

5. EIPS port

The EIPS port is an abstract conception, corresponding to a link forming the EIPS ring. This link can be a single physical link or an aggregation port formed by multiple physical links. Each EIPS node has two ports connected to the EIPS ring. Due to the EIPS ring intersection, an EIPS port may belong to multiple EIPS nodes.

Primary EIPS port and secondary EIPS port: The ports on the master node and transmission node are divided into the primary port and secondary port. The main port on the master node sends the Hello packet and the secondary port receives this packet. This method is used to ensure the ring integrity. If the ring is complete, the data VLAN of the secondary port is blocked. For a transmission node, a primary port and a secondary port do not have special meanings.

6. Topology level

Topology level refers to the hierarchical division of the rings in the EIPS domain. The EIPS domain comprises a ring or multiple intersecting rings. When the EIPS domain consists of only one single ring, the ring is the major-level ring and is numbered 0; when the EIPS domain comprises multiple intersecting rings, a ring is selected as the major-level ring and is numbered 0. The low-level segment link refers to the ring connected to the major-level ring excluding the common link intersecting with the major-level ring.

The low-level link refers to the link set excluding the common link connected to the upper layer.

The major-level ring is numbered 0 (the highest level). The lower the level is, the larger the level number is.

7. Topology segment

In a hierarchical EIPS, the segment number is used to identify different low-leve links of the same layer. Multiple low-level links may exist on the same level of the EIPS domain and are defined by different segment numbers. The segment number of the major-level ring is 0.

After the EIPS domain is divided by levels and segments, the corresponding ring or low-level link of each level and segment in the whole domain is identified by unique level number and segment number, which is called level segment. The low-level links defining the level number and segment number are called low-level segment.