What protocols does the network gateway convert?

Question

Computer networks

I do not quite understand what a network gateway is.

Internet users and computers that deliver the user's web pages are hosts, and nodes between different networks are network gateways.

It seems clear from this that a network gateway is just a network node that converts protocols.

But I don't quite understand what it means to convert protocols? That is, there is, for example, the OSI or TCP / IP protocol stack. And at each level there are certain protocols. The network gateway is engaged in conversion of these protocols? To, for example, convert the protocol from Ethernet to HTTP?

Or does it mean something else?

A network gateway is a hardware router or software for interfacing computer networks using different protocols (for example, local and global).

Maybe some kind of protocol for the entire network is meant here?

Answer 1

The OSI model is roughly related to the actual structure of the network.
A gateway is usually a layer 3 device. Its task is to transfer packets from one network to another. The gateway knows nothing about protocols.
Sometimes a higher level device is called a gateway. For example, a sip telephony gateway, but in this case, the gateway transmits packets from one network to another ...

Answer 2

It is not possible to convert protocols :) A protocol is the order of a sequence. It was asked once and then adhered to. They are "converted" by the working group that developed this protocol.
It is possible to convert packets of some protocol by converting it to packets of another protocol, but the gateway does not do this. It doesn’t convert anything into anything at all if it doesn’t have special functions - for example, a Mikrotik that has an SFP where an optical module is inserted converts the hardware level of optics to Ethernet.
In general, usually the gateway simply transfers something from something to somewhere, and these "something" and "somewhere" can be very high-level objects - for example, a VPN gateway connects users to the VPN network, forming a virtual tunnel and transmitting then packages on it.

Answer 3

In common parlance, a network gateway is a router. But more general tasks can also be imposed on the gateway. Authorization, authentication, filtering, media and transfer protocol conversion, etc.
Moreover, this can all be done at different levels of the OSI model. Most often, gateways are used to convert the data transmission medium, from ethernet to frame relay, infiniband, tfop, while providing filtering and perimeter protection ...

Answer 4

Most likely we are talking about NAT when the host of the local network through the gateway goes to another network. Your address range is 192.168.x. y remains on your side of the gateway, and on the other side, requests go with the addresses of that other network. And the gateway redirects responses from the outside to the sender in the local network. it's all at the tcp/ip level.
Also, the same NAT can forward ports and, for example, a request for port 80 turns into a request for port 8080.
And there are also pieces of iron that convert Ethernet to USB and they can also be called network printing gateways :)