[nsteel]

Vendors I've seen usually use one of a few "standard" packet size mixes e.g. imix. Nobody uses smallest size frames because nobody can hit their headline perf numbers for that, and it's not representative of real-world usage anyway.

https://en.m.wikipedia.org/wiki/Internet_Mix

[Hikikomori]

I think this applies more to firewalls used for simple internet connections than switches/routers.

[nsteel]

I was specifically talking about enterprise/core routers where the packet processing can be non-trivial and small frames hurt performance.

[Hikikomori]

What core routers uses imix?

[nsteel]

Not sure what you mean, but an example of using imix to measure perf of a core router is Cisco 8000 series https://miercom.com/wp-content/uploads/2024/02/Performance-V...

[Hikikomori]

That 8200 for example is capable of line rate at the smallest packet size so that imix marketing is kinda useless. When evaluating these kinds of devices this is what matters.

IMIX makes sense on devices that are not capable of small packet line rate like firewalls where bandwidth is much more costly and need to be sized appropriately.

[nsteel]

I don't have any Cisco core routers, not have I personally tested any, but that document I provided found their Q200 ASIC (in the 8000 series) required at least 170B frames to hit line rate:

> Both DUTs can achieve line rate performance on all ports with an NDR of 170 Bytes for the 88-LC0-36FH-M line card and 215 Bytes for 8201-32FH router. Same values were observed for both IPv4 and IPv6 traffic. This exceeds all real-life deployments requirements regardless of position in the network.

The 9000 series analysis reports something like 400B packets to hit line rate.

Fundamentally, everyone has to scale their internal bus width and clock rate to hit the headline numbers, always at the cost of small frame performance.