WAN Underlay Path Discovery Using TTL Probe Packets

The patent introduces probe packets as intermediary carriers that transport unique identifiers and TTL values through the network tunnel. These probe packets act as mediators between the source and destination, enabling path tracing without being affected by the inconsistent IP addresses, port numbers, or network fragmentation that plague traditional tracing methods. The probe packets maintain their integrity throughout the tunnel traversal, allowing precise path determination.

The patent utilizes the TTL (Time To Live) parameter as a changing identifier that decrements at each network hop. By monitoring the TTL value changes and associated unique identifiers in the probe packets, the system can precisely determine the path taken through the tunnel. This parameter-based approach overcomes the limitations of traditional methods that rely on consistent IP addresses and port numbers, which are disrupted by load-balancing and fragmentation.

The patent enhances existing BFD (Bidirectional Forwarding Detection) packets to serve multiple functions: traditional link detection, path tracing, and network parameter measurement. By making BFD packets multi-functional, the system achieves precise path discovery without requiring entirely new packet types or protocols. The same packet structure carries identifier fields, TTL values, and path information, reducing the need for separate specialized tools.

The probe packets are designed to be self-sufficient, carrying all necessary information (unique identifiers, TTL values, path markers) within their own structure. As they traverse the network tunnel, they automatically decrement TTL at each hop and generate responses without requiring external intervention or complex processing at intermediate nodes. This self-service approach simplifies the overall system architecture despite the enhanced packet capabilities.