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jafingerhut merged 1 commit into from
Oct 20, 2025
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Add more detail to flowcache README #704

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4 changes: 3 additions & 1 deletion exercises/flowcache/README.md
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Expand Up @@ -23,7 +23,9 @@ necessary to forward traffic between hosts.

The starter code for this assignment is in files called `flowcache.p4` and `mycontroller.py`. Your job will be to finalize the P4 program to properly implement the `PacketIn` and `PacketOut` idle timeout mechanismes.

Let's first compile the new P4 program, start the network, and use `mycontroller.py` to install the flowcache pipeline in the data plane.
First, you need to define the fields in the `packet_in` and `packet_out` headers; otherwise, you’ll get compilation errors. The `packet_in` header should contain three fields: `input_port`, `punt_reason`, and `opcode`. The `packet_out` header should include: `opcode`, `reserved1`, and `operand0` (which represents the egress port in this case). You can see how these header fields are configured and used in the P4 code. More details about `packet_in` and `packet_out` are available in Section 6.4.6 of the [P4Runtime Spec](https://p4.org/specifications/).

After defining the `packet_in` and `packet_out` headers, compile the new P4 program, start the network, and use `mycontroller.py` to install the flowcache pipeline in the data plane.

1. In your shell, run:
```bash
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