Re: maximum ipv4 bgp prefix length of /24 ?

[Tom Beecher <beecher () beecher cc>]

General Purpose CPU : Can run Doom.
Trio ASIC : Cannot run Doom.

Have a good weekend Bill.

On Fri, Sep 29, 2023 at 5:48 PM William Herrin <bill () herrin us> wrote:

> On Fri, Sep 29, 2023 at 2:13 PM Tom Beecher <beecher () beecher cc> wrote:
> > > My understanding of Juniper's approach to the problem is that instead
> > > of employing TCAMs for next-hop lookup, they use general purpose CPUs
> > > operating on a radix tree, exactly as you would for an all-software
> > > router.
> >
> > Absolutely are not doing that with "general purpose CPUs".
> >
> > The LU block on early gen Trios was a dedicated ASIC (LU by itself, then
> consolidated slightly) , then later gen Trio put everything on a single
> chip, but again dedicated ASIC.
>
> Hi Tom,
>
> For clarity, general purpose CPU refers to an architecture not an
> implementation. It's capable of running arbitrary computer software
> and has the typical functions like loading and saving registers, an
> adder, bit shifts, etc. The CPU in a Raspberry Pi is also part of a
> dedicated ASIC that does wifi, packet switching and a bunch of other
> stuff. It's still a CPU. Compare to a TCAM which is purpose built to
> match input bit patterns and is capable of nothing else.
>
> I suppose the PPEs in the Trio are more like GPUs than CPUs - more
> limited instruction sets but higher parallelism. However, they still
> follow the cache pattern where the frequently used parts of the FIB
> tree are in a fast SRAM cache and the remainder is in slower DRAM
> where it can be loaded into SRAM at the occasional need. The FIB size
> limit before cache thrashing sets in and cuts the PPS is softer than
> the limit with a TCAM but it's still there.
>
> Compare to a TCAM which uses a tristate ram rather than the normal
> two-state sram.
>
> Yes?
>
> Regards,
> Bill Herrin
>
>
>
> --
> William Herrin
> bill () herrin us
> https://bill.herrin.us/