What is the Protocol and Default Port for the following:

1. Provides connections to computers over a TCP/IP network.
2. Sends e-mail over a TCP/IP network.
3. Translates URLs to IP address.
4. Transports web pages over a TCP/IP network.
5. Automates assignments of IP address on a network.
6. Securely transports web pages over a TCP/IP network.
7. Transports files over a TCP/IP network.

–Any help would be appreciated–

What are the real fundamental limits that prevent Layer 2 bridges from being used to connect networks to form the Internet?
Yes, these days we have routers, and on top of the basic functionalities are added many “clever” features such as firewall etc… But just in terms of the ability to connect networks over the world, send and receive packets securely between any 2 computers, is there any reason why bridges won’t do the job?