The promise of P4 is to have a customer change the switch data plane in the field. If the switch runs vendor code, how does the customer merge his/her P4 code with vendor’s? An operator upgrades a switch several times during the lifetime of the switch. The customer also runs feature set A on 100 switches and feature set B on another 100. Each set uses customer P4 programs merged with vendor’s. How is any operator running the network unless a tool exists to automatically merge customer’s P4 program with any version of vendor’s P4 program with different feature sets?

This is where a tool comes in, provided by the switch vendor. The tool facilitates merging customer and vendor P4 programs. The first tool, called daPIPE, is released by Cisco for trials. Our P4-Ansible is second.

A simple example use of our tool merges a small Video RTP TWC P4-16, say, customer program, with large NPB P4-16, say, vendor program. Our tool automatically merges the two programs and creates a new P4 program which is compiled with Tofino compiler. The compiled output has been tested on Tofino to work. Similar to Cisco daPIPE, our tool exposes some vendor P4 program information to customer to help write a P4 program – it is information such as parser states names, data structures, and names of P4 objects such as parser, control, and deparser. All vendor P4 code cannot stay hidden because a simple use case fails to merge customer and vendor programs. The example adds new a tunnel type. After decapsulation, somewhere at the beginning of ingress, you want the rest of pipeline to execute on the decapsulated packet. How do you integrate with code that you can’t see?

A comparison of the two tools is included below.

Cisco (daPIPE)MNK (P4-Ansible)Comments
Supports only P4-14Supports only P4-16MNK helps customer translate P4-14 to P4-16. Open
to adding P4-14 on customer request.
Single parser and deparserMultiple parsers and
deparsers
P4-14 uses single parser
and deparser. P4-16 PSA
models uses two of each.
Tofino model uses 5 parsers and 2 deparsers.
Supports TofinoSupports Tofino, Spectrum from Mellanox, and
softswitch v1model
Does not support all P4
programs
Supports any P4 program
Supports only Cisco switchSupports any switch
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