# Built-in library for existed network protocols

**URL:** <https://forum.p4.org/t/built-in-library-for-existed-network-protocols/773>\
**Category:** Getting Started with P4\
**Created:** [May 8, 2023, 12:36pm UTC](https://forum.p4.org/t/built-in-library-for-existed-network-protocols/773 "2023-05-08T12:36:14Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![elwinzhao](https://avatars.discourse-cdn.com/v4/letter/e/58956e/32.png) [@elwinzhao](https://forum.p4.org/u/elwinzhao)\
**Post date:** [May 8, 2023, 12:36pm UTC](https://forum.p4.org/t/built-in-library-for-existed-network-protocols/773/1 "2023-05-08T12:36:14Z")

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Does P4 support existed network protocols? For example, suppose I want to use P4 to implement ICMP protocol, do I need to rewrite all packet forwarding logic? Or I can just use built-in library?

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**Author:** ![andyfingerhut](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.p4.org/andyfingerhut/32/17_2.png) [@andyfingerhut](https://forum.p4.org/u/andyfingerhut)\
**Post date:** [May 8, 2023, 6:39pm UTC](https://forum.p4.org/t/built-in-library-for-existed-network-protocols/773/2 "2023-05-08T18:39:28Z")

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If you find someone else who has written and published P4 code for what you want to do, then subject to the license under which that code was release, and/or other agreements you might make for using their code, you can use it.

But no, there is no built-in support for “do the right thing with ICMP packets” in P4, nor for any other protocol or header.