Difference Between Centralized Routing and Distributed Routing

Centralized Routing vs Distributed Routing | Centralised Routing vs Distributed Routing

路由是一个过程of choosing which paths to be used to send network traffic, and sending the packets along the selected sub-network. Centralized routing model is a routing model in which routing is centrally carried out using a centralized database. On the contrary, distributed routing model is a routing model, which deals with carrying out routing using a distributed database.

What is Centralized Routing?

Centralized routing model is a routing model in which routing is centrally carried out using a centralized database. In other words, the routing table is kept at a single “central” node, which should be consulted when other nodes need to make a routing decision. This centralized database possesses a global network view. Centralized routing is most appropriate in specific domains with systems providing DWDM (Dense Wavelength Division Multiplexing) transmission. The reason for this is that these DWDM systems contain OADM (Optical Add-Drop Multiplexer) that can be reconfigured, within the starting point and end point of the communication medium. Proponents of centralized routing suggest that because most information such as details on SRLG (Shared Risk Link Group) and parameters of performance do no change frequently (and these information may never be self-discovered or advertized), they are ideal to be resided in a central database. In a centralized model, information of state can easily be accessed. Therefore, the information on dependencies (with regard to routing) between circuits (to make sure the diversity exists) can be handled relatively easily when terminals are not shared between circuits, and this is ideal for a centralized routing model. The centralized model uses global state information. The computations that are carried out (such as pre-computing the paths for restoring) can be highly benefitted from this global information and therefore this is suitable for a centralized model.

What is Distributed Routing?

In distributed routing model, each node keeps a separate routing table. Distributed routing model is a routing model, which is excellent for domains that can be identified as entirely opaque. The main reason for this is that constraints on impairments do not play any role in routing within these aforementioned domains. In case of a failure (when there is a need to restore rapidly), distributed routing system can be relied upon to bear the responsibility of the on-demand computation of a paths of recovery for each of the light-paths that have failed (even at the point of detecting an expected failure). Finally, the distributed routing model is highly consistent with the existing Internet’s own distributed routing philosophy.

What is the difference between Centralized Routing and Distributed Routing?

集中式路由模型使用集中式数据库进行路由，而分布式路由模型则处理使用分布式数据库进行路由。简而言之，一个中央节点将路由表保存在集中模型中，而每个节点则在分布式模型中保留一个路由表。由于许多信息不经常变化，因此许多人认为此信息非常适合驻留在集中式数据库中。恢复所需的预计可以利用集中式数据库中可用的全局信息。但是，与分布式路由系统不同，不能依靠集中式系统来承担每一个失败的轻道（在检测预期失败的时候）恢复路径的按需计算。与集中式方法不同，分布式路由模型与现有互联网自己的分布式路由理念高度一致。