Question

When using In-band Network Telemetry (INT), at which specific point in the packet processing lifecycle is the metadata regarding path latency and queue depth inserted into the packet?

Accepted Answer

In-band Network Telemetry metadata is inserted into a packet at the egress stage of the packet processing pipeline. When a packet enters a network switch, it undergoes an ingress process where the switch identifies that the packet is marked for telemetry tracking. As the packet traverses the switch fabric, the device monitors its own internal state, specifically calculating path latency, which is the time spent waiting in queues or processing, and queue depth, which is the number of packets currently held in a specific buffer. These metrics are compiled into a metadata header. The switch then injects this metadata into the packet header at the egress port, which is the physical or logical interface where the packet exits the device. By inserting the data at the egress, the switch ensures that the recorded latency reflects the actual time the packet spent transiting that specific hop before being forwarded to the next destination in the network.

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When using In-band Network Telemetry (INT), at which specific point in the packet processing lifecycle is the metadata regarding path latency and queue depth inserted into the packet?

In-band Network Telemetry metadata is inserted into a packet at the egress stage of the packet processing pipeline. When a packet enters a network switch, it undergoes an ingress process where the switch identifies that the packet is marked for telemetry tracking. As the packet traverse....