CGNAT scaling cost (was Re: V6 still not supported)

Vasilenko Eduard vasilenko.eduard at
Wed Mar 30 16:25:37 UTC 2022

CGNAT cost was very close to 3x compared to routers of the same performance.
Hence, 1 hop through CGNAT = 3 hops through routers.
3 router hops maybe the 50% of overall hops in the particular Carrier (or even less).

DWDM is 3x more expensive per hop. Fiber is much more expensive (greatly varies per situation and distance).
Hence, +50% for IP does not mean +50% for the whole infrastructure, not at all.

I was on all primary vendors for 2.5 decades. 3x cost of NAT was consistent for all vendors and at all times.
Because it is a "Network processor" (really flexible one with a big memory) against "specialized ASIC". COTS (x86) is much worse for the big scale - does not make sense to compare.
It has started to decrease recently when SFPs have become the bigger part of the router (up to 50% for single-mode).
Hence, I expect the decrease of the difference between router and CGNAT cost to 2x long-term.
Optical vendors are more capable to protect their margins.

It is a different situation in Mobile Carriers, where Packet Core and Gi-LAN were never accelerated in hardware.
Everything else is so expensive (x86) per Gbps, that CGNAT is not visible in the cost.

-----Original Message-----
From: NANOG [ at] On Behalf Of Jared Brown
Sent: Wednesday, March 30, 2022 6:33 PM
To: nanog at
Subject: CGNAT scaling cost (was Re: V6 still not supported)

An oft-cited driver of IPv6 adoption is the cost of scaling CGNAT or equivalent infrastructure for IPv4.

Those of you facing costs for scaling CGNAT, are your per unit costs rising or declining faster or slower than your IPv4 traffic growth?

I ask because I realize I am not fit to evaluate the issue on a general level, as, most probably due to our insignificant scale, our CGNAT marginal costs are zero. This is mainly because our CGNAT solution is oversized to our needs. Even though scaling up our currently oversized system further would lower per unit costs, I understand this may not be the case outside our bubble.

- Jared

More information about the NANOG mailing list