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Network protocols

Network protocols

Network protocols are sets of established rules that dictate how to format, transmit and receive data so computer network devices -- from servers and routers to endpoints -- can communicate regardless of the differences in their underlying infrastructures, designs or standards.

To successfully send and receive information, devices on both sides of a communication exchange must accept and follow protocol conventions. Support for network protocols can be built into software, hardware or both.

Standardized network protocols provide a common language for network devices. Without them, computers wouldn't know how to engage with each other. As a result, except for specialty networks built around a specific architecture, few networks would be able to function, and the internet as we know it wouldn't exist. Virtually all network end users rely on network protocols for connectivity.

How network protocols work?

Network protocols break larger processes into discrete, narrowly defined functions and tasks across every level of the network. In the standard model, known as the Open Systems Interconnection (OSI) model, one or more network protocols govern activities at each layer in the telecommunication exchange.

A set of cooperating network protocols is called a protocol suite. The TCP/IP suite includes numerous protocols across layers -- such as the data, network, transport and application layers -- working together to enable internet connectivity. These include:

  • Transmission Control Protocol (TCP), which uses a set of rules to exchange messages with other internet points at the information packet level;
  • User Datagram Protocol (UDP), which acts as an alternative communication protocol to TCP and is used to establish low-latency and loss-tolerating connections between applications and the Internet.
  • Internet Protocol (IP), which uses a set of rules to send and receive messages at the Internet address level; and
  • additional network protocols that include the Hypertext Transfer Protocol (HTTP) and File Transfer Protocol (FTP), each of which has defined sets of rules to exchange and display information.

Types of network protocols.

Internet Protocol Suite

Internet protocol suite is the set of communication protocols that implement the protocol stack on which the internet runs. The Internet protocol suite is sometimes called the TCP/IP protocol suite, after TCP\IP, which refers to the important protocols in it, the Transmission Control Protocol(TCP) and the Internet Protocol(IP). The Internet protocol suite can be described by the analogy with the OSI model, but there are some differences. Also not all of the layers correspond well.


Protocol Stack

A protocol stack is the complete set of protocol layers that work together to provide networking capabilities.


Transmission Control Protocol (TCP)

The Transmission Control Protocol is the core protocol of the internet protocol suite. It originated in the network implementation in which it complemented the Internet Protocol. Therefore the entire suite is commonly referred to as TCP/IP. TCP provides reliable delivery of a stream of octets over an IP network. Ordering and error-checking are main characteristics of the TCP. All major Internet applications such as World Wide Web, email and file transfer rely on TCP.


Internet Protocol(IP)

The Internet Protocol is the principal protocol in the Internet protocol suite for relaying data across networks. Its routing function essentially establishes the internet. Historically it was the connectionless datagram service in the original Transmission Control Program; the other being the connection oriented protocol(TCP). Therefore, the Internet protocol suite is referred as TCP/IP.


Common Protocols Used and Their Ports

Hypertext Transfer Protocol (HTTP)

The HTTP is the foundation of data communication for the World Wide Web. The hypertext is structured text that uses hyperlinks between nodes containing texts. The HTTP is the application protocol for distributed and collaborative hypermedia information system.

The default port of HTTP is 80 and 443 is the secured port.


File Transfer Protocol (FTP)

The FTP is the most common protocol used in the file transferring in the Internet and within private networks.

The default port of FTP is 20/21.


Secured Shell (SSH)

SSH is the primary method used to manage the network devices securely at the command level. It usually used as the alternative of the Telnet which does not support secure connections.

The default port of SSH is 22.



Telnet is the primary method used to manage network devices at the command level. Unlike SSH, Telnet does not provide a secure connection, but it provides a basic unsecured connection.

The default port of Telnet is 23.


Simple Mail Transfer Protocol (SMTP)

SMTP is used for two primary functions. It is used to transfer email from source to destination between mail servers and it is used to transfer email from end users to a mail system.

The default port of SMTP is 25 and secured (SMTPS) is 465 (Not standard).


Domain Name System (DNS)

Domain name system is used to convert the domain name to IP address. There are root servers, TLDs and authoritative servers in the DNS hierarchy.

The default port of DNS is 53.


Post Office Protocol version 3 (POP 3)

The Post Office Protocol version 3 is one of the two main protocols used to retrieve mail from the internet. It is very simple as it allows the client to retrieve complete content from the server mail box and deletes contents from the server.

The default port of POP3 is 110 and secured is 995.


Internet Message Access Protocol (IMAP)

IMAP version 3 is another main protocol that used to retrieve mail from a server. IMAP does not delete the content from the mail box of the server.

The default port of IMAP is 143 and secured is 993.


Simple Network Management Protocol (SNMP)

The Simple Network Management Protocol is used to manage networks. It has abilities to monitor, configure and control network devices. SNMP traps can also be configured on network devices to notify a central server when specific action are occurring.

The default port of SNMP is 161/162.


Hypertext Transfer Protocol over SSL/TLS (HTTPS)

HTTPS is used with HTTP to provide same services, but with a secured connection which is provided by SSL or TLS.

The default port of HTTPS is 443.

Every packet transmitted and received over a network contains binary data. Most protocols will add a header at the beginning of each packed in order to store information about the sender and the message's intended destination. Some protocols may also include a footer at the end with additional information. Network protocols process these headers and footers as part of the data moving among devices in order to identify messages of their own kind.

Network protocols are often set forth in an industry standard -- developed, defined and published by groups such as:

Major types of network protocols

Generally speaking, networks have three types of protocols -- communication, such as Ethernet; management, such as the Simple Mail Transfer Protocol (SMTP); and security, such as Secure Shell (SSH).

Falling into these three broad categories are thousands of network protocols that uniformly handle an extensive variety of defined tasks, including authenticationautomation, correction, compressionerror handling, file retrieval, file transfer, link aggregation, routing, semantics, synchronization and syntax.

Implementing network protocols

In order for network protocols to work, they must be coded within software, either a part of the computer's operating system (OS) or as an application, or implemented within the computer's hardware. Most modern operating systems possess built-in software services that are prepared to implement some network protocols. Other applications, such as web browsers, are designed with software libraries that support whatever protocols are necessary for the application to function. Furthermore, TCP/IP and routing protocol support is implemented in direct hardware for enhanced performance.

Whenever a new protocol is implemented, it is added to the protocol suite. The organization of protocol suites is considered to be monolithic since all protocols are stored in the same address and build on top of one another.

Vulnerabilities of network protocols

One major vulnerability found in network protocols is that they are not designed for security. Their lack of protection can sometimes allow malicious attacks, such as eavesdropping and cache poisoning, to affect the system. The most common attack on network protocols is the advertisement of false routes, causing traffic to go through compromised hosts instead of the appropriate ones.

Network protocol analyzers have been designed and installed in response to these vulnerabilities. Network protocol analyzers protect systems against malicious activity by supplementing firewalls, anti-virus programs and anti-spyware software.

Uses of network protocols

Network protocols are what make the modern Internet possible since they allow computers to communicate across networks without users having to see or know what background operations are occurring. Some specific examples of network protocols and their uses are:

  • Post Office Protocol 3 (POP3), which is the most recent version of a standard protocol that is used for receiving incoming e-mails.
  • Simple main transport Protocol, which is used to send and distribute outgoing e-mails.
  • File Transfer Protocol (FTP), which is used to transfer files from one machine to another.
  • Telnet, which is a collection of rules used to connect one system to another via a remote login. In this protocol, the system that send the request for connection is the local computer and the system that accepts the connection is the remote computer.

Some other network protocol examples include: