Re: IPv6 Performance (was Re: IPv4 Pricing)

[Marco Moock via NANOG <nanog () lists nanog org>]

Am 04.12.2025 um 08:24:18 Uhr schrieb Vasilenko Eduard:

> In the great majority of cases, it was said "IPv6 is faster" without
> clarification that it is for RTT that does not matter. The user is
> misled that it is for FCT that he/she needs. People said
> non-important advantage about 10^6 times - you are not boring with
> this. I said 3 times about important disadvantage - you are already
> boring.

I've experienced faster IPv6 in real situations where CGNAT was
overloaded. Measurements with speed tests are also possible, if someone
want statistics about this. There are also cases where it is slower,
e.g. tunneled IPv6, what I used for some years.

> You did touch ASIC processing. Actually, it is not important because
> it would be pretty fast anyway (X us).

Pretty fast doesn't mean infinite speed. As you are saying IPv6 must be
slower because of more overhead, ASIC processing is indeed relevant.

> What is important that IPv6 architecture has 2x bigger meaningful
> address part, hence, the scalability of tables (for routing,
> filtering) is 2x less for all vendors and all products.

That is just an assumption without any reason. If the XOR comparison is
being done in the same amount of CPU time (buswidth), the decision speed
is exactly the same. This depends heavily on the actual implementation
of software and hardware, there is no general answer.


> Why it is 2x not 4x? Because the second half of addresses is not the
> address, hence, it is typically discarded from such tables.

That also depends on the hardware. Certain DFZ routers will most likely
only process /48.
 
> As you see, IPv6 has many deficiencies against IPv4: more overhead,
> less scale in memory. But most of them are justified.

Although, almost irrelevant in practice, as other factors are more
important.

-- 
Gruß
Marco

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