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Comment by fulafel | Hacker News Reader

Trivia: Strictly speaking a box that does NAT is not a router in the IP protocol sense, it's a kind of proxy. The router requirements RFC explicitly forbids altering most fields (incl the address field) in the IP header.

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The box in people's home's colloquially known as a router actually commonly combines a lot of functions into one:

* router

* firewall

* NAT device

* modem

* switch

* access point

* DNS resolver

* DHCP server

And probably others I'm not thinking of :-)

I call them “terminal adapters”, because I’m still stuck in the ISDN age.

Adding more functions to a router doesn't make it a non-router. But if it's doing NAT and not routing, then it's a different distinction. But yep it depends on the configuration.

ONT in the case of fiber. Don't know if it technically counts as a modem.

Media converter maybe? (Like those $100 or so fiber to ethernet converters, I say this as it’s usually a modem/router plugged into the ONT‘s ethernet port that does isp to cpe authentication, tunneling, etc. so the ONT is just converting fiber (from isps OLT) to ethernet for something more common to plug into)

Modem comes from MODulator/DEModulator. It's taking a signal of one sort (electrical) and modulating light to send info, and also demodulating incoming light to receive. It's a modem.

The NAT RFCs came after the routing RFC and refer to NAT as a router function not as an orthogonal function, boxes that do NAT are referred to as routers in the RFC. This is reflected in the real world where NAT is implemented as part of the routing chain not as a separate module. Remember NAT isn't a box creating 2 sockets and ferrying data between them it is just the translation of fields on top of normal routing functionality.

> boxes that do NAT are referred to as routers in the RFC

This is not the case, certainly if you are referring to the router requirements. Last I looked, the rest of the IETF was also very cognizant of the distinction, as there has been wide anti-NAT sentiment in the IETF, trying to get people to move over to IPv6 etc.

Again router requirements came out before NAT, you're not going to find anything in that RFC about something else they hadn't written yet. You have to look at the RFCs for NAT to see they are referred to as routers e.g. starting with https://tools.ietf.org/html/rfc1631:

"2. Overview of NAT

The design presented in this memo is called NAT, for Network Address Translator. NAT is a router function that can be configured as shown in figure 1. Only the stub border router requires modifications."

The IETF collectively aren't big fans of NAT as a good solution but that hasn't stopped multiple standards track NAT RFCs per year. v6 only increased this with all of the transitional mode NAT types (46, 64, 464, 646).

That's an informational rfc that has no weight in this manner, router requirements is a standards track document.

"4.2.2 Informational

An "Informational" specification is published for the general information of the Internet community, and does not represent an Internet community consensus or recommendation. The Informational designation is intended to provide for the timely publication of a very broad range of responsible informational documents from many sources, subject only to editorial considerations and to verification that there has been adequate coordination with the standards process (see section 4.2.3)."

> boxes that do NAT are referred to as routers in the RFC.

Newer RFCs use different terms such as CPE (customer premises equipment) and AFTR (address family transition router)

Very true. Yet at the same time, it does route traffic to the appropriate boxes. And the name 'router', when referring to something someone has at their house, has entered the vernacular to mean "the box at home which lets me share the internet connection across all my computers".

Most folks have no idea how it works behind the scenes, which typically is a combination of NAT (IPv4), routing (IPv6), DHCP, DNS, UPnP, and more. So, it's just "the router".

...an RFC that was written in 1995, before NAT was really necessary.

My view: If it forwards IP between different networks, it's a router.

Nat existed in somewhat wide use in 95, PIX had come out recently. It's not necessary today either.

It existed, but was definitely not in wide use. I worked for several early internet providers during that period (mid to late 90's.) Most folks had public addresses on their desktops. No customer we ever set up wanted NAT. Most didn't even have firewalls, sadly! Some of these were small companies, some of these were large corporations or universities.

And I'd argue NAT actually is necessary if you want IPv4 for home use. We'd be out of addresses otherwise.

ISPs didn't use it in the early days, but it was used in corporate/organizational networks. The PIX was apparently marketed as a security appliance (heh) so that defined the user base to a large extent.

You can access the web over v4 with other kind of proxies besides NAT, for example application level HTTP proxies. If you want working v4 for all the protocols, NAT is out by definition anyways.

Yes, I remember the PIX! Probably late 97 or 98, I set one up for a large corp. They were not using NAT previously, but HTTP and socks proxies.

RFC 1918 does allow that the internet was changing rather fast back in 1995 and accepts it probably wont be the final word: https://tools.ietf.org/html/rfc1812#section-1.3.1

Trivia: Strictly speaking a box that does NAT is not a kind of proxy. Proxies act as the destination end point of one connection, establish a separate connection to another endpoint and forward data between the two separate connections. A NAT device changes IP header information such as the address field and if also doing PAT the port field but doesn't act as the source or destination for connections.

I have a box that runs various routing protocols including OSPF and BGP, but also does nat where it needs to. It's known as a "router"

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