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Advanced Ping

The usefulness of ping is greatly increased when it is used at regular intervals. For example, a monitored system could be "pinged" at one to ten second intervals or so.
 
  1. Large variations in the ping time can indicate impending congestion in the routers between the monitored system and the network management station -- such variations are usually related to packets waiting in router buffers.
     
  2. Some pings (or ping responses) may be dropped in the network, indicating actual congestion (ie, routers experiencing buffer exhaustion) or possibly a "flakey" connection somewhere. Since an occasional loss of a packet is actually quite normal, the most interesting parameter here is the packet loss rate, expressed as a percentage of total pings sent.
     
  3. Most ping implementations can flood ping -- sending pings as fast as the originating system can generate them! Such stress testing can reveal problems with the network that only show up under heavy load. Needless to say, this option should be used sparingly!
     
  4. Most pings allow the user to set both the size of the ping packet (which can be up to the maximum possible datagram size) and the contents, which will pad the data area beyond the section needed for ping itself. These options can be used to reveal size and data-dependent problems with network components.
     
One other thing. The "man" page for ping wisely states:
This program is intended for use in network testing, measurement and management. Because of the load it can impose on the network, it is unwise to use ping during normal operations or from automated scripts.
Even more importantly -- you should only use ping for management purposes within your own network. Repeated pings to external hosts can be interpreted as indicating a Denial-of-Service attack.
 
Lecture 21: Network Management #1 Copyright © 2005 P.Scott, La Trobe University Bendigo.


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