TCP/IP is a suite of protocols that allow computers and networking devices to communicate. TCP/IP software resides in your local computer and puts your information into IP packets that have a 32-bit IP address. The address is expressed as a dotted decimal number, for example 125.10.18.99.
Using these addresses, the computer, the intranet or the Internet can send your data to a remote computer. That's where the IP part of TCP/IP comes in. It provides the most basic information to allow your information to be routed to the proper destination. But IP doesn't guarantee that your information will arrive in the same order it was sent, so TCP works with the IP protocol to reassemble the information into an uninterrupted data stream.
In addition to routing information, an IP header also contains other important information, including:
- Version field, indicating which IP version is being used;
- Header length, limited to 60 bytes in IPv4;
- Type of service, used to show the traffic requirements of the packet;
- Length, indicating the length of the entire datagram;
- Identification, which uniquely shows which IP packet belongs to which datagram; and
- Source address and destination address, each limited to 32 bits.
IP frames are both variable in length and can arrive "out of sequence," which allows for variable delay and presents special challenges when trying to use IP for delay-sensitive services like voice.
Additional resources
Introduction to TCP/IP
Overview of pre-IPv6 TCP/IP.
