At the most basic level, TCP/IP offers a set of rules for conversing among networks. The network protocol governs the complex web of Internet-based communications.
TCP/IP (Transmission Control Protocol/Internet Protocol) sets the communications standard for trillions of data packets. The protocol prescribes a well-specified set of procedures for these packets to follow as they zip from node to node.
"TCP/IP is a set of protocols that enables packets to be run across wires," explains Bruce Robertson, program director for Global Networking Strategies at Meta Group Inc. in Stamford, Conn.
The wire that connects each node - computer, modem or routing device - consists primarily of copper wire or fiber-optic cables. But as the demand for digital data transmission increases, so does the use of TCP/IP in other media, such as telephony and air- and radio-wave broadcasting.
Originally designed by the U.S. Department of Defense, TCP/IP was widely used in information technology systems at universities and government agencies. But its commercial usage paled in comparison to competing approaches, like Novell Inc.'s SPX/IPX, Microsoft Corp.'s NetBEUI protocol suite or IBM's SNA. Until the Web, which also set TCP/IP as its protocol of choice, grew in popularity, a debate raged over which communications protocol would dominate network communications.
"Why did TCP/IP win the battle for the ubiquitous networking protocol?" says Raymond Keneipp, director of market research firm The Burton Group in Midvale, Utah. "The Internet ended the debate, because if you want to play on the Internet, you must use TCP/IP. The real power of the Internet is the fact that anybody can talk to anybody. Previously, it was a major project for company A to talk to company B [through networked computers]."
While TCP/IP has emerged as the cornerstone of Internet transport in the past few years, alternative networking communication frameworks have moved to the sidelines.
By the fall of 1998, Novell ended its reliance on SPX/IPX and reworked its NetWare 5.0 software to natively support TCP/IP. Novell officials said customers overwhelmingly demanded an open system based on TCP/IP. Microsoft added TCP/IP support to its software sooner, even though NetBEUI continues to exist in Windows and runs over TCP/IP.
"That's the ugly secret inside Windows today," says Tim Sloane, managing director for Internet infrastructure research at Aberdeen Group Inc. in Boston.
NetBEUI "is the original DOS communications protocol, and it creates lots of network confusion and traffic in mixed-node networks."
IBM introduced SNA in 1974 to support network routing communications in mainframe computing environments. But it has long since adopted TCP/ IP support. "Of all the protocols, the one that people want is TCP/IP," says Bill Reedy, vice president of marketing for business integration at IBM. "Even where SNA has a big advantage in terms of reliability and even performance, the customers are standardizing their network to intermix devices, voice and data.
TCP/IP is the way we communicate over the Internet."
"This is a done deal; there's not a question about this anymore," adds Robertson. "In the last five years, it's become clear TCP/IP is the protocol.
And in the last two years, the Internet completely anointed it."
Even so, TCP/IP doesn't provide the best fit for every network. Because not all networks transmit their packets of data at consistent speeds or within well-defined WAN and LAN perimeters with standard bandwidth, in many cases TCP/IP proves too cumbersome to use.
For example, many wireless networks utilize lower-level protocols such as the Wireless Application Protocol and Cellular Digital Packet Data to handle digital data transmission on handheld devices. A roaming cellular phone user requires a more resilient protocol to accommodate fluctuations in bandwidth and network availability. Other devices, such as communications satellites, also present challenges.
"It is admittedly not perfect for every possible network environment, but it's so good at most of them that it becomes a very simple way for applications to use most networks," Robertson says. "Even if it's not the most efficient, it's the most practical."
As networks and their data traffic evolve, so do the protocols designed to support them. Working groups at the Internet Engineering Task Force continue to augment the communications stack with new, complementary protocols like Dynamic Host Configuration Protocol (DHCP), which automatically assigns IP addresses to client stations as they log on to a TCP/IP network. Without DHCP, IT administrators must manually assign IP addresses to network devices.
The upcoming version of TCP/IP will also support expanded Internet addressing.
"One of the problems with TCP/IP today is that it does not have enough address space," Keneipp says. "Every single network device has its own address, and this means millions of addresses."
Keneipp says TCP/IP Version 6 expands today's four-group format to six (from xxx.xxx.xxx.xxx to xxx.xxx.xxx.xxx.xxx.xxx) to handle the growing number of handheld and embedded devices that require their own Internet addresses.
TCP/IP 4.0 helps networked computers and other devices communicate. Although many proprietary approaches for handling network communications have been introduced, by the early 1990s, TCP/IP emerged as the dominant model for linking nodes over the Internet.