NET-Simulator

NET-Simulator is a program designed to provide lecturers and students a convenient visual tool for studying basics of computer networks.

NET-Simulator implements two layers of ISO OSI: 2nd - Data Link and 3rd - Network. The 1st - Physical Layer is not emulated, so the electrical and physical specifications for devices are not taken into account. It is supposed that 2nd layer packets are transmitted through an Ethernet-like environment.

Thus NET-Simulator allows users to achieve the following goals:

· Study the principles of operation for 2nd and 3rd layer switches and passive hubs. · Getting practical skills of the static IP4 routing configuration. · Study communication protocols ARP, IP4, ICMP. · Getting skills of trouble shooting in computer networks.

NET-Simulator uses a simple Ethernet-like protocol on the 2nd layer. This protocol uses addressing by 6 byte MAC-address. The uniqueness of the every MAC-address is provided by the NET-Simulator kernel. Actually, a packet of the 2nd layer is a Java object and it does not have any equivalent in real computer networks.

On the 3rd layer there is a restricted implementation of IP4 protocol according to RFC791. In order to resolve IP to MAC-addresses there is an ARP service based on broadcast requests.

There is restricted implementation of ICMP according to RFC792 that allows working services like ping and traceroute.