[P4-dev] Cut-through switching specification at P4 level

Andy Fingerhut andy.fingerhut at gmail.com
Wed May 17 18:59:11 EDT 2017

I am not aware of any way to specify this in the P4 language (and I've read
through the spec several times in the last couple of weeks).  The most the
spec has to say about it is to note that if you want to access a packet
length field, that would be impossible on a cut-through target
implementation, so a program accessing such information would not be
portable to such a target (Section 11.8 "Data Extraction" of the P4-16

Just about everything I can think of that you would want to write a P4
program would be independent of whether the target was cut-through or
store-and-forward.  Do you have some application or feature in mind where
that would make a difference to you when writing P4 code?


On Wed, May 17, 2017 at 5:36 AM, Saulo Queiroz <ssaulojorge at gmail.com>

> Hi all,
> Is it possible to specify at P4 level whether a given target operate
> as cut-though or store-and-forward?
> BTW, does switch.p4 support cut-through?
> thanks in advance
> --
> Saulo Jorge bq
> - "Beware of bugs in the above code; I have only proved it correct, not
> tried it."
> Donald Knuth.
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