How A Ping Plotter Works

Ping Plotter identifies the routers through which a connection passes.

Ping Plotter is a network diagnosis tool created by Nessoft, LLC. It has a graphical display that shows a current network connection with the performance of each link in the route between two connected computers. Network communications follows a client-server model where the client is a computer that contacts another computer to request a service or resource, like a file or a Web page. Ping Plotter runs on the client computer.

Basis

Ping Plotter uses three underlying utilities. These are Ping, Traceroute and Whois. A connection to a server on the Internet crosses many other networks. Each connection is created by a router. When the client computer sends a request it does not know the path its messages will take to arrive at the destination. The client networking software only has to address the packets of data it sends out, giving the address of the destination server, and also including its own address so the server knows where to send the reply. The client computer sends the packet to the first router in the chain, but the path from then on is up to each successive router. Ping Plotter has to track the route.

Ping

Ping is a commonly used network administration tool that tests the speed of a route by sending a test packet to a destination and waiting for a reply. The utility relies on the functions of the Internet Control Message Protocol. ICMP is a companion protocol of the Internet Protocol. IP does not have any error messaging functions, it is just concerned with addressing and routing packets. ICMP provides these functions. One of the message types defined in the ICMP specification is a “ECHO_REQUEST” packet. Any computer receiving this packet knows to immediately reply with an “ECHO_RESPONSE” message. Ping records the time difference between the issue of the request and the receipt of the response. This gives the speed of the connection. Also any lost packets are reported back to the user. Ping cannot detect which links in the route cause the connection to be slow, nor can it detect at which point a lost packet was dropped.

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Traceroute

Ping Plotter builds up a map of all the links the messages between client and server cross. It does this by exploiting one of the fields in the IP header of the ping “ECHO_REQUEST” packet. This is the Time to Live field. TTL is set by the sender’s network and specifies the maximum number of routers the packet may cross on its journey. Each router that handles the packet decreases this number by 1. If TTL reaches zero, the router drops the packet and sends an ICMP error packet back to the originator of the packet. Thus, by successively sending out ping packets with progressively higher TTLs, starting with 1, Traceroute forces each router handling packets on the route to identify themselves. The time difference between each successive report also enables the Ping Plotter to identify slow links.

Whois

The involvement of Whois in the Ping Plotter display is an optional extra. The Whois protocol makes information about the owner of an IP address or Web URL available to the public. Ping Plotter queries a Whois server for each link. It shows the name and ownership of each link in the route in a right-click menu on the display or the route.