AWS Elastic IP architecture

Michael Helmeste elf at
Thu May 28 18:39:59 UTC 2015

> -----Original Message-----
> From: christopher.morrow at
> Subject: Re: AWS Elastic IP architecture
> > [...]
> > All that is happening is that they have some NAT device somewhere
> > (maybe even just a redundant pair of VMs?) that has a block of public
> > IPs assigned to it and they
> i'd question scalability of that sort of thing... but sure, sounds like a
> reasonable model to think about.

I agree it appears ugly from a traditional network service provider perspective, but to my understanding much of the large scale cloud stuff is built using the cheapest, dumbest switching you can find and as little rich L3 routing gear (e.g. ASR/MX) as you can get away with.

The more functionality you can pack into software (with the universal building block being a VM), the less you have to worry about buying network hardware to any particular requirement other than "forwards Ethernet most of the time." It gives more control and agility to the developers of the platform, and spending a few gigabytes of RAM for every /23 and adding a little more latency and jitter ultimately becomes an economical trade off.

You can also move the network stuff up to the hypervisor layer (which I am sure they have done for things like Security Groups), but it makes rolling out updates harder and increases the general hack-level.

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