[ale] Some networking definitions

[Michael Trausch]

It would appear that there is a decent amount of miscommunication that is in
part a result of not being on the same page.

The following things are all separate:

Firewall
Router
NAT
ALG
Proxy
Switch/Bridge

A firewall provides packet filtering. Stateful, stateless, doesn't matter.

A router moves packets between IP nets.

A NAT acts sort of like a router. More like a transparent proxy. It
intercepts packets, keeps a bit of state in the common case, and rewrites
all packets passing through it.

An ALG (application layer gateway) helps NATs be more transparent. They have
other uses but that is today the primary usage. Used for FTP, SIP, and some
other protocols (the linux kernel has some built-in, IIRC).

A proxy is just that. SOCKS and HTTP proxies are the most common, but there
are others.

Switches and bridges are essentially the same. They are transparent to IP.

HTH.

--
Sent from da phone.
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