Logical Router Route Propagation via Network Controller
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Solution Overview
Problem
Existing network technologies face challenges in efficiently managing and propagating routes between logical routers in virtualized networks, particularly in implementing dynamic routing and handling different types of routes, which can lead to increased processing complexity and inefficiency.
Innovation Solution
A network control system that enables the connection of logical routers and propagates routes between them, managed by network controllers that compute additional route information, generate routing tables, and distribute them across the network, supporting dynamic routing and various types of routes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If logical routers use only connected routes based on IP prefix configured on ports, then implementation is simple using software forwarding elements, but dynamic routing and multiple route types cannot be supported
Solution Approach 1:
A network controller is introduced as an intermediary between physical routers and logical routers. The controller receives routing information from physical routers, processes it, and distributes appropriate routing tables to logical routers. This mediator handles the complexity of dynamic routing protocols and route type management, allowing logical routers to support multiple route types without requiring complex processing capabilities in the forwarding elements themselves.
Solution Approach 2:
The system creates simplified copies of routing functionality in the form of routing tables generated by the network controller. Instead of implementing full routing protocol stacks in each logical router, the controller generates routing table copies that contain the essential routing information needed by logical routers. This copying approach maintains versatility in route type support while keeping device complexity low.
2Adaptability or versatility
If multiple route types (connected, static, dynamic) are added to logical routers, then routing flexibility improves, but processing techniques become complex and difficult to implement in software forwarding elements
Solution Approach 1:
The network controller serves as an intermediary that handles the complexity of managing multiple route types. It receives connected routes from logical router ports, processes static routes, and learns dynamic routes from physical routers. The controller then synthesizes these into routing tables that are distributed to logical routers, maintaining routing flexibility while simplifying implementation in software forwarding elements.
Solution Approach 2:
The complex processing techniques required for handling multiple route types are extracted from the logical routers and concentrated in the network controller. The controller performs route validation, priority determination, and routing table generation, leaving the logical routers with simpler forwarding decisions based on pre-computed routing tables. This extraction makes the system easier to implement in software forwarding elements.
3Productivity
If network controllers generate and distribute routing tables with dynamic route information, then dynamic routing between logical routers is enabled, but control system complexity increases
Solution Approach 1:
The network controller merges multiple routing information sources (connected routes from logical router ports, static routes, and dynamic routes from physical routers) into unified routing tables. By combining these different route types and processing them centrally, the system achieves efficient dynamic routing between logical routers while consolidating control logic in a single component, which manages complexity rather than increasing it across the distributed system.
Data Source
AI summary
Some embodiments provide a managed network for implementing a logical network for a tenant. The managed network includes a first set of host machines and a second set of host machines. The first set of host machines is for hosting virtual machines (VMs) for the logical network. Each of the first set of host machines operates a managed forwarding element that implements a first logical router for the tenant logical network and a second logical router to which the first logical router connects. The implementation of the second logical router is for processing packets entering and exiting the tenant logical network. The second set of host machines is for hosting L3 gateways for the second logical router. The L3 gateways connect the tenant logical network to at least one external network.