When a transmission network consists of equipment from multiple vendors, the OSI over DCC transparently transmits the management information at the network layer, thereby offering greater flexibility in networking. A user can use the existing DCC resources to uniformly manage the equipment from multiple vendors without creating extra DCN channels.
The OSI protocol supports the following three types of network nodes: ES (End System), L1-IS (Level 1 Intermediate Systems) and L2-IS (Level 2 Intermediate Systems).
The ES only supports limited routing functions. To communicate with other network nodes, an ES can only forward data packets to them by L1-IS or L2-IS that is directly connected to the ES and has the routing function. As a result, only the nodes at the tips of a network rather than the nodes amid a network are allowed to be set to ES. Because of the limited routing function that may be an obstacle in network expansion, it is recommended not to set an NE to an ES during the networking. The networking system of Huawei acts as an ES network node.
L1-IS is the default node type of Huawei optical network equipment. It only supports the routing within an area, also known as Level 1 Routing. If a piece of equipment requires the routing across multiple areas, also known as Level 2 Routing, you need to set the node type of the equipment to L2-IS. An L2-IS-type node is in charge of two routing tables, one for intra-area routing and the other one for inter-area routing.