Use Ping to check availability of Server

One important facet of site monitoring is knowing as soon as possible that servers have failed or are not accessible. A web server provides multiple services not just HTTP. Just because a server is not responding to HTTP requests does not imply it is not functioning at all.

The simplest means of establishing whether a site or server is alive is using the Interface Control Message Protocol (ICMP) protocol to Ping a server. This is a much simpler request than fetching an HTML page in terms of the communication overheads. It runs over the IP protocol and so checks that the IP part of TCP/IP is functioning OK. This protocol is also used by the tracert command line utility to find the route that communication is taking to a server.

The Ping connectivity check works well in an Office Intranet situation too, it can regularly monitor whether the key servers and workstations are responding properly to IP traffic within an office local area network.

The protocol supports a number of commands but the ECHO command is the one of interest for Ping monitoring. It instructs routers to pass the message over IP to a particular destination IP address requesting an ECHO REPLY to be sent back. Measuring the time between from issuing the ECHO and receiving the ECHO REPLY determines the responsiveness of the remote server. The ICMP echo reply includes a Time to Live (TTL) value. This indicates the number of router hops that the message has gone through from the source. Normally the packet starts off with a 255 TTL value and then each router it passes through decrements the value by one. If the number of hops is erratic or suddenly becomes large this indicates a router problem.

The same ECHO command can be used to trace a route over the Internet (as used in tracert program). In this case the protocol's TTL field is used to limit how many hops between routers it can make before the request fails. If the limit is reached then a failure response is returned, with the IP address of the most distant router on the path returned. By iterating over all TTL values until the destination server is reached all the routers can be identified. By inspecting the time delay between reaching routers along the communication path bottlenecks can be easily identified.

monitor ping

monitor ping

Site Vigil lets you check whether a server is accessible or not you using the Ping protocol. As some servers have blocked ping requests you can also use a socket connect on any port to achieve a similar result.

This feature is also very useful for Intranets where a network administrator needs to check that a whole set of different servers are accessible.

The picture shows the measured latency between issuing a ping request and receiving a ping echo response over a day. The server went offline at about 6:30 pm.

check ping

check ping

Site Vigil™ is a sophisticated web site monitoring tool that lets you thoroughly check your site. Improve the effectiveness of your web site by tracking the flow of visitors. Make sure your site is operational and your web host is giving a fast, trouble-free service. Automatically check the position of your site on search engines and the validity of all the links.

It runs on an ordinary Windows® PC, using your normal Internet connection to gather data quietly in the background. Periodically it will alert you as soon as a problem is spotted.

Site Vigil is available for a free 40 day trial, give it a try by going to the download page.
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We have a large reference section and a set of case studies to help you with all your monitoring needs.