NET-Simulator0.34a

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.