introduction: this article makes a systematic analysis of "taiwan cn2's routing priority and traffic policy" from the perspective of a network engineer. the article focuses on bgp routing attributes, common cn2 practices, traffic engineering and monitoring methods, to help operations and architecture teams optimize cross-ocean link performance and availability.
cn2 overview: what is cn2 and its characteristics
cn2 usually refers to china telecom's high-quality backbone network (variants such as cn2/gia), which focuses on low latency, stability and differentiated services. for taiwan's inbound and outbound traffic, cn2 provides controllable paths, better qos and multi-point access, which is suitable for delay-sensitive applications and enterprise interconnection.
taiwan network environment and cross-ocean link characteristics
links from taiwan to mainland china or internationally are affected by submarine cables, interconnection points (ix), and local isp policies and regulations. link selection needs to consider submarine cable redundancy, node delay, packet loss, and the peering/forwarding relationship between operators to formulate an effective routing priority strategy.
basics of bgp route priority: key attributes and route selection order
bgp route selection relies on multiple attributes: local_pref, as_path, med, origin, igp distance and weight, etc. for ingress and egress traffic control, local preferences are commonly used to adjust priorities, as_path prepending is used for downgrading, and med is used for adjacency influence to form predictable traffic directions.
common practice of cn2 in routing priority in taiwan
when connecting to cn2, bgp community, local-pref, and link blackhole policies are often used to achieve granular control. operators often negotiate priorities through community tags, and the client implements detailed traffic distribution through route-map and policy routing.
traffic engineering methods: mpls, segment routing, and sd-wan
for more refined traffic engineering, mpls-te or segment routing can provide deterministic paths within the operator's network; enterprises can use sd-wan to make application-aware link selection and implement dynamic offloading strategies based on delay, packet loss, or cost.
multi-link, load balancing and failover strategies
in a multi-link environment, bgp ecmp, policy routing or traffic mapping can be used to achieve load balancing. for failover, it is recommended to combine bfd, fast convergence strategy and health detection to achieve fast switchover when the link fails and avoid route flapping.
performance monitoring and sla indicator focus
effective strategies need to be data-driven and focus on monitoring latency, jitter, packet loss, and availability. active detection (ping/icmp/tcp), synthetic transactions and passive traffic sampling should be deployed, combined with sla indicators to determine path quality and trigger automated policy adjustments.
security protection and routing management suggestions
cross-ocean links can easily become ddos targets, so it is recommended to deploy traffic cleaning, prefix filtering and rpki/roa verification. combined with prefix whitelisting, community tags, and rate limiting, it protects its own resources while maintaining routing stability with cn2 peers.
summary and operation and maintenance suggestions
summary: in taiwan's cn2 scenario, priority control should be combined with bgp attributes, community policies and traffic engineering methods, supplemented by active monitoring and security protection. it is recommended to define traffic baseline and sli first, and then implement local preferences, route mapping and sd-wan policies in stages to achieve stable and observable cross-ocean connections.
