FreeBSD® Unleashed

Network Protocols

We've mentioned that most Internet traffic—HTTP, e-mail, FTP, and so on—use TCP/IP as their transport protocol, but also that it's more complicated than that alone. IP, the Internet Protocol, is the backbone of the vast majority of Internet traffic—the “network”layer of the TCP/IP stack—but TCP isn't the only commonly used “transport” layer protocol. There's also UDP, which differs from TCP in a few key ways. IP also isn't the only means of carrying traffic at the “network” level; it has a number of contemporaries, too, but they're mostly useful on LANs: AppleTalk, IPX, IGMP, and so on. Then there's ICMP, which exists partly on the “network” layer and partly on the “transport” layer; it's the mechanism by which the ping and ...