Route Reflector Layer 2 Route Calculation Using Sequence Numbers
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Solution Overview
Problem
In EVPN networks, route reflector routers face challenges in accurately selecting the best Layer 2 route for customer network devices during MAC mobility, leading to traffic loss and misconfiguration due to reliance on IP addresses for path selection.
Innovation Solution
A mechanism is introduced in route reflector network devices to perform Layer 2 route calculation by receiving and processing MAC/IP routes with sequence numbers, allowing for the determination of the best route based on the sequence number indicative of the order of advertisement, thereby ensuring accurate route selection during MAC mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If route reflector routers rely on IP addresses for path selection during MAC mobility, then routing decisions can be made, but accurate route selection fails leading to traffic loss and misconfiguration
Solution Approach 1:
The patent changes the selection parameter from IP address to sequence number associated with MAC advertisement routes. The sequence number explicitly indicates the order of MAC address advertisement, allowing the route reflector to accurately identify the most recent MAC location. This parameter change resolves the contradiction by providing reliable route selection information that directly reflects MAC mobility state.
2Adaptability or versatility
If multiple MAC advertisement routes are advertised for the same customer network device, then route options increase, but determining the best route becomes complex without sequence numbers
Solution Approach 1:
The patent introduces sequence numbers as an additional parameter in MAC advertisement routes. This parameter provides a clear ordering indicator that simplifies the route selection process. Instead of complex analysis of multiple route attributes, the route reflector simply compares sequence numbers to determine the most recent MAC location, reducing determination logic complexity while maintaining multiple route options.
Solution Approach 2:
The sequence number acts as feedback information that explicitly indicates the current valid MAC location. Each MAC advertisement includes a sequence number that reflects the latest known position of the MAC address, providing immediate feedback to the route reflector about which route to prefer without requiring complex analysis of route history or timing.
3Loss of information
If the route reflector advertises routes to all network devices, then route information is widely distributed, but traffic loss occurs when using outdated routes during MAC mobility
Solution Approach 1:
The sequence number provides feedback to all network devices about the current valid MAC location. When the route reflector receives a MAC advertisement with a higher sequence number, it updates its routing table and propagates this information to all connected devices. This feedback mechanism ensures all devices have consistent, up-to-date route information, preventing traffic loss during MAC mobility while maintaining wide route information distribution.
Data Source
AI summary
A network device (ND) receives a first media access control (MAC)/Internet Protocol (IP) route for a customer ND. The ND installs the first MAC/IP route in a MAC/IP routing table and transmits the first MAC/IP route to a first subset of NDs causing the NDs to install the first route. The ND receives a second MAC/IP route for the customer ND and a sequence number indicative of an order of advertisement of the second MAC/IP route. The ND determines, based on the sequence number, that the second MAC/IP route is a best route for the customer ND. The ND installs the second MAC/IP route as the best route for the customer ND; and transmits the second MAC/IP route to a second subset of NDs including a first ND from which the first MAC/IP route originated, causing the first ND to request withdrawal of the first MAC/IP route.