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Inband Network Telemetry

Packet Forwarding Engine provides In-Band Network Telemetry (INT) in the data plane to collect and report network state information without control plane intervention.

In the INT architectural model, network devices interpret the packets's header fields as telemetry instructions. These instructions specify the type of network state information to collect at each INT-capable device. Network state information is either exported to a telemetry monitoring system or embedded within the packet as it moves through the network. When telemetry data is embedded in packets, INT sink nodes collect and report the aggregated information, enabling precise visibility into the data plane as packets are forwarded.

INT Application Modes

INT supports multiple application modes based on how telemetry instructions and metadata are handled. Original data packets are monitored and modified to carry INT instructions and metadata. There are three variations based on the level of packet modifications.

  • INT-XD (eXport Data): INT nodes directly export metadata from their dataplane to the monitoring system based on the INT instructions configured at their flow watchlists. No packet modification is needed. This mode was previously known as Postcard mode.
  • INT-MX (eMbed instruct(X)ions): The INT Source node embeds INT instructions in the packet header, then the INT Source, each INT Transit, and the INT Sink directly send the metadata to the monitoring system by following the instructions embedded in the packets. The INT Sink node strips the instruction header before forwarding the packet to the receiver.
  • INT-MD (eMbed Data): In this mode both INT instructions and metadata are written into the packets. This is the classic hop-by-hop INT where

    1. INT Source embeds instructions

    2. INT Source and Transit embed metadata

    3. INT Sink removes the instructions and aggregated metadata out of the packet and sends the data to the monitoring system.

    This mode involves the highest level of packet modification but reduces the need for the monitoring system to correlate data from multiple nodes. INT-MD is the default operating mode.

Use the forwarding-options (Routing Instance) command to enable or disable INT.