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Network monitoring is the use of a system that constantly monitors a computer network for slow or failing components and that notifies the network administrator (via email, SMS or other alarms) in case of outages or other trouble. Network monitoring is part of network management. [1]
While an intrusion detection system monitors a network threats from the outside, a network monitoring system monitors the network for problems caused by overloaded or crashed servers, network connections or other devices.
For example, to determine the status of a web server, monitoring software may periodically send an HTTP request to fetch a page. For email servers, a test message might be sent through SMTP and retrieved by IMAP or POP3.
Commonly measured metrics are response time, availability and uptime, although both consistency and reliability metrics are starting to gain popularity. The widespread addition of WAN optimization devices is having an adverse effect on most network monitoring tools, especially when it comes to measuring accurate end-to-end delay because they limit round-trip delay time visibility. [2]
Status request failures, such as when a connection cannot be established, it times-out, or the document or message cannot be retrieved, usually produce an action from the monitoring system. These actions vary; An alarm may be sent (via SMS, email, etc.) to the resident sysadmin, automatic failover systems may be activated to remove the troubled server from duty until it can be repaired, etc.
Monitoring the performance of a network uplink is also known as network traffic measurement.
Network tomography is an important area of network measurement, which deals with monitoring the health of various links in a network using end-to-end probes sent by agents located at vantage points in the network/Internet.
Route analytics is another important area of network measurement. It includes the methods, systems, algorithms and tools to monitor the routing posture of networks. Incorrect routing or routing issues cause undesirable performance degradation or downtime.
Site monitoring services can check HTTP pages, HTTPS, SNMP, FTP, SMTP, POP3, IMAP, DNS, SSH, TELNET, SSL, TCP, ICMP, SIP, UDP, Media Streaming and a range of other ports with a variety of check intervals ranging from every four hours to every one minute. Typically, most network monitoring services test your server anywhere between once per hour to once per minute.
For monitoring network performance, most tools use protocols like SNMP, NetFlow, Packet Sniffing, or WMI.
Monitoring an internet server means that the server owner always knows if one or all of their services go down. Server monitoring may be internal, i.e. web server software checks its status and notifies the owner if some services go down, and external, i.e. some web server monitoring companies check the status of the services with a certain frequency. Server monitoring can encompass a check of system metrics, such as CPU usage, memory usage, network performance and disk space. It can also include application monitoring, such as checking the processes of programs such as Apache HTTP server, MySQL, Nginx, Postgres and others.
External monitoring is more reliable, as it keeps on working when the server completely goes down. Good server monitoring tools also have performance benchmarking, alerting capabilities and the ability to link certain thresholds with automated server jobs, such as provisioning more memory or performing a backup.
Network monitoring services usually have several servers around the globe - for example in America, Europe, Asia, Australia and other locations. By having multiple servers in different geographic locations, a monitoring service can determine if a Web server is available across different networks worldwide. The more the locations used, the more complete the picture of network availability.
When monitoring a web server for potential problems, an external web monitoring service checks several parameters. First of all, it monitors for a proper HTTP return code. By HTTP specifications RFC 2616, any web server returns several HTTP codes. Analysis of the HTTP codes is the fastest way to determine the current status of the monitored web server. Third-party application performance monitoring tools provide additional web server monitoring, alerting and reporting capabilities.
As the information brought by web server monitoring services is in most cases urgent and may be of crucial importance, various notification methods may be used: e-mail, landline and cell phones, messengers, SMS, fax, pagers, etc.
Email is a method of transmitting and receiving messages using electronic devices. It was conceived in the late–20th century as the digital version of, or counterpart to, mail. Email is a ubiquitous and very widely used communication medium; in current use, an email address is often treated as a basic and necessary part of many processes in business, commerce, government, education, entertainment, and other spheres of daily life in most countries.
In computing, the Post Office Protocol (POP) is an application-layer Internet standard protocol used by e-mail clients to retrieve e-mail from a mail server. Today, POP version 3 (POP3) is the most commonly used version. Together with IMAP, it is one of the most common protocols for email retrieval.
The Simple Mail Transfer Protocol (SMTP) is an Internet standard communication protocol for electronic mail transmission. Mail servers and other message transfer agents use SMTP to send and receive mail messages. User-level email clients typically use SMTP only for sending messages to a mail server for relaying, and typically submit outgoing email to the mail server on port 587 or 465 per RFC 8314. For retrieving messages, IMAP is standard, but proprietary servers also often implement proprietary protocols, e.g., Exchange ActiveSync.
An email client, email reader or, more formally, message user agent (MUA) or mail user agent is a computer program used to access and manage a user's email.
Mercury Mail Transport System is a standards-compliant mail server developed by David Harris, who also develops the Pegasus Mail client.
The UW IMAP server was the reference server implementation of the Internet Message Access Protocol. It was developed at the University of Washington by Mark Crispin and others.
Push email is an email system that provides an always-on capability, in which when new email arrives at the mail delivery agent (MDA), it is immediately, actively transferred (pushed) by the MDA to the mail user agent (MUA), also called the email client, so that the end-user can see incoming email immediately. This is in contrast with systems that check for new incoming mail every so often, on a schedule. Email clients include smartphones and, less strictly, IMAP personal computer mail applications.
The following tables compare general and technical information for a number of notable webmail providers who offer a web interface in English.
Website monitoring is the process of testing and verifying that end-users can interact with a website or web application as expected. Website monitoring are often used by businesses to ensure website uptime, performance, and functionality is as expected.
hMailServer was a free email server for Windows created by Martin Knafve. It ran as a Windows service and includes administration tools for management and backup. It had support for IMAP, POP3, and SMTP email protocols. It could use external database engines such as MySQL, MS SQL or PostgreSQL, or an internal MS SQL Compact Edition engine to store configuration and index data. The actual email messages were stored on disk in a raw MIME format. As of January 15th, 2022, active support and development were officially halted, although version 5.6 will continue to receive updates for critical bugs.
Argus is a systems and network monitoring application. It is designed to monitor the status of network services, servers, and other network hardware. It will send alerts when it detects problems.
Shinken is an open source computer system and network monitoring software application compatible with Nagios. It watches hosts and services, gathers performance data and alerts users when error conditions occur and again when the conditions clear.
Extromatica Network Monitor is a network monitoring application created and maintained by Extromatica company. It is designed to monitor network hardware, servers and network services for faults and performance degradation. It alerts users when things go wrong and again when they get better. The software supports a variety of real-time notification mechanisms, including Short Message Service (SMS).
GroupWise is a messaging and collaboration platform from OpenText that supports email, calendaring, personal information management, instant messaging, and document management. The GroupWise platform consists of desktop client software, which is available for Windows,, and the server software, which is supported on Windows Server and Linux.
Xymon, a network monitoring application using free software, operates under the GNU General Public License; its central server runs on Unix and Linux hosts.
Icinga is an open-source computer system and network monitoring application. It was created as a fork of the Nagios system monitoring application in 2009.
Checkmk is a software system developed in Python and C++ for IT Infrastructure monitoring. It is used for the monitoring of servers, applications, networks, cloud infrastructures, containers, storage, databases and environment sensors.
PA Server Monitor is a server and network monitoring software from Power Admin LLC. PA Server Monitor focuses primarily on server and network health through numerous resource checks, reports, and alerting options. The agentless, on-premises software can monitor thousands of devices from a single installation. The monitored devices can be desktop computers, servers, routers and other devices.
Endian Firewall is an open-source router, firewall and gateway security Linux distribution developed by the South Tyrolean company Endian. The product is available as either free software, commercial software with guaranteed support services, or as a hardware appliance.
PRTG is a network monitoring software developed by Paessler GmbH. It monitors system conditions like bandwidth usage or uptime and collect statistics from miscellaneous hosts such as switches, routers, servers, and other devices and applications.