CE Router Link-Overload Flood for Black-Hole Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In overlay networks, it is challenging to notify other devices when a provider edge (PE) router is being taken offline for maintenance, leading to potential transient black-holing of network traffic due to the PE router's invisibility within the Interior Gateway Protocol (IGP) domain, which prevents effective rerouting of traffic.
Innovation Solution
A method where a customer edge (CE) router determines that a PE router is going offline and floods link-state messages with 'link-overload information' to other routers in the IGP domain, instructing them to stop sending traffic over the affected link, allowing for rerouting and preventing transient black-holing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a PE router is taken offline for maintenance without notification, then the PE router can be maintained, but network traffic is black-holed and connectivity is lost
Solution Approach 1:
The CE router performs preliminary action by flooding link-state messages with overload information before the PE router is actually taken offline. This advance notification allows other routers to preemptively reroute traffic away from the PE router, preventing transient black-holing during the transition period when the PE router is going offline but has not yet fully stopped forwarding traffic.
Solution Approach 2:
The CE router acts as an intermediary between the PE router and other routers in the IGP domain. Since the PE router is not visible to other CE routers in the overlay network, the CE router that detects the PE router going offline becomes the mediator that propagates this information through flooding link-state messages, enabling other routers to make informed routing decisions without direct visibility of the PE router's status.
2Reliability
If link-state messages include overload information, then traffic rerouting is enabled, but message complexity increases
Solution Approach 1:
The overload information is merged into the existing link-state message structure rather than creating a separate notification mechanism. By combining the overload indicator with the standard link-state messaging protocol, the solution enables traffic rerouting functionality while reusing existing message infrastructure, thereby limiting the increase in complexity to only the essential overload indication fields.
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
In general, techniques are generally described for reducing or preventing transient black-holing of network traffic in an overlay network. A method includes executing, by a network device included in a link state domain, an Interior Gateway Protocol (IGP) to exchange link-state messages with at least one remote network device in the link-state domain; generating, by the network device, an IGP link-state message that includes link overload information to overload a link in the link-state domain that couples the network device to the remote network device; and sending, by the network device and to the at least one other network device, the IGP link-state message that includes the link overload information to direct the remote network device to stop sending network traffic to the network device using the overloaded link.