, ARP, NDP, OSPF, Tunnels, L2TP, PPP, MAC, Ethernet, DSL, ISDN, FDDI, etc.
## Network device terminology
- Node: any device on a network
- Switch: a node that connects networks on the *data link layer* only
- Also called a bridge
- Router: a node that connects networks on the *network layer*
- Gateway: a node that connects two networks that (potentially) use different protocols
- Also translates addresses, etc.
- Firewall: blocks 'bad' traffic (more on this in a few slides)
![networking diagram](https://phoenix.cs.virginia.edu/~aaron/network-encapsulation.svg)
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