Dear friends,

Please explain the functionality of the ping command and explain the network details, and IP layers.

I want some more clarification about following things
i) switch
ii) hub
iii) routers
iv) proxy

HUB
A network hub or concentrator is a device for connecting multiple twisted pair or fiber optic Ethernet devices together, making them act as a single network segment.
Router
A router is a computer whose software and hardware are usually tailored to the tasks of routing and forwarding information.
Switch
A network switch is a computer networking device that connects network segments.
Ping
Ping is one of the most useful network debugging tools available.
In an IP network.
`ping' sends a short data burst - a single packet - and listens for a single packet in reply. Since this tests the most basic function of an IP network (delivery of single packet)