Objective 1.1: Explain the function of common networking protocols
In computing, a protocol is a convention or standard that controls or enables the connection, communication, and data transfer between computing endpoints. In its simplest form, a protocol can be defined as the rules governing the syntax, semantics, and synchronization of communication. Protocols may be implemented by hardware, software, or a combination of the two. At the lowest level, a protocol defines the behavior of a hardware connection.
While protocols can vary greatly in purpose and sophistication, most specify one or more of the following properties:
- Detection of the underlying physical connection (wired or wireless), or the existence of the other endpoint or node
- Handshaking (dynamically setting parameters of a communications channel)
- Negotiation of various connection characteristics
- How to start and end a message
- How to format a message
- What to do with corrupted or improperly formatted messages (error correction)
- How to detect unexpected loss of the connection, and what to do next
- Termination of the session and or connection.
The Internet Protocol Suite (commonly known as TCP/IP) is the set of communications protocols used for the Internet and other similar networks. The Internet Protocol Suite, like many protocol suites, may be viewed as a set of layers. Each layer solves a set of problems involving the transmission of data, and provides a well-defined service to the upper layer protocols based on using services from some lower layers. Upper layers are logically closer to the user and deal with more abstract data, relying on lower layer protocols to translate data into forms that can eventually be physically transmitted. The TCP/IP model consists of four layers. From lowest to highest, these are the Link Layer, the Internet Layer, the Transport Layer, and the Application Layer.
Some have attempted to map the Internet Protocol model onto the seven-layer OSI Model. The mapping results in the TCP/IP Link Layer corresponding to the OSI Data Link and Physical layers in terms of functionality. The Internet Layer is usually directly mapped to the OSI's Network Layer. At the top of the hierarchy, the Transport Layer is always mapped directly into the OSI Layer 4 of the same name. OSI's Application Layer, Presentation Layer, and Session Layer are collapsed into TCP/IP's Application Layer.
The following table provides some examples of the protocols grouped in their respective layers. See the below sections for details on each protocol.
|Application||DNS, TFTP, TLS/SSL, FTP, HTTP, IMAP4, POP3, SIP, SMTP, SNMP, SSH, Telnet, RTP|
|Internet||IP (IPv4, IPv6), ICMP, IGMP|