Cross-Domain Segment Routing Packet Processing to Avoid URPF Drops
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Solution Overview
Problem
Packets are discarded due to unicast reverse path forwarding (URPF) check failures when segment routing (SR) paths cross underlay networks in different routing domains.
Innovation Solution
Update the source and destination IP addresses of packets based on endpoint IP addresses of connections, using tunnel virtual connections (TVCs) to avoid dependency on underlay network routing protocols, and utilize a controller device for path orchestration and SID assignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If segment routing paths cross underlay networks in different routing domains, then network flexibility and routing control are improved, but packets are discarded due to URPF check failures
Solution Approach 1:
The patent introduces a head end device as an intermediary that performs source routing encapsulation. This head end device acts as a mediator between the source host and the SR path, encapsulating packets with segment lists that guide forwarding through multiple routing domains. The intermediary handles the complexity of cross-domain routing while maintaining reliable packet delivery by ensuring proper source IP address preservation throughout the SR path.
2Device complexity
If source IP address is always an IP address of a head end in SR packets, then routing simplicity is improved, but URPF check fails in cross-domain scenarios
Solution Approach 1:
The patent applies preliminary action by having the head end device perform source routing encapsulation before packets enter the SR path. The head end device pre-configures the segment list and ensures the source IP address is properly set to the head end's IP address. This preliminary configuration enables intermediate nodes to forward packets reliably without needing to perform complex URPF checks, as the source routing information is already established.
3Adaptability or versatility
If underlay network devices run IGP routing protocols to support SR, then routing protocol compatibility is improved, but implementation complexity and dependency on underlay protocols increase
Solution Approach 1:
The patent extracts the source routing functionality from the underlay network devices and concentrates it in the head end device. By removing the requirement for underlay devices to run IGP routing protocols supporting SR, the patent eliminates the dependency on underlay protocol compatibility. The head end device independently performs encapsulation and routing control, allowing SR to operate over any underlay network without requiring the underlay devices to understand or support SR-specific routing protocols.
Data Source
AI summary
A packet processing method, a network device, and a network system are provided, which are related to the field of communication technologies. According to the method, an intermediate node updates a source IP address of a packet based on an IP address that belongs to a local end in an endpoint IP address of a connection, and updates a destination IP address of the packet based on an IP address that belongs to a remote end in the endpoint IP address of the connection. Therefore, in a scenario in which an SR path crosses underlay transport networks in a plurality of different routing domains, a problem that a packet is discarded because a source IP address is always an IP address of a head end and URPF check fails is avoided.