Duo to the high cost of network entity equipment environment, network laboratory is not established completely in colleges and universities in china, students find that it is difficult to grasp the complex and abstract network concepts. Virtual learning tool software named Cisco Packet Tracer is free for students in anytime, which provides the same configuration environment as true network entity equipment. This paper presents the example of Dynamic Routing Protocol (RIP), and offers experimental design topology of RIP. This teaching mode not only reduces the dependence on the real environment, but also helps students to master the abstract network concepts and enhance theirs practical operation skills. This can cultivate student's innovative spirit.

As network environment is becoming more and more complex, it is difficult for students to understand and master the complex and abstract network concepts. A virtual learning tool named Cisco Packet Tracer has been introduced into the classroom teaching, which provides the virtual configuration environment as real one. This article presents the features of the virtual simulation tool, and the configuration example for mini practice project, which can inspire students creativity. It makes teaching and learning computer network much easier than traditional teaching method.

This paper presents a new multi-hop routing algorithm for wireless sensor networks. Each sensor node makes a local decision to forward or drop a packet, via a forwarding probability, either static or dynamic. This probability can be associated with local information such as residual energy of the node, packet properties, in order to optimize network performance. The direction of forwarding is guided by received signal strength indication (RSSI) relative to the sink node. Moreover, based on the characteristic of wireless communication that all packets are broadcast at the radio level, an implicit ARQ mechanism, where a receiver does not send an ACK frame explicitly to the sender, is adopted in our method. RSSI guided direction, probability based forwarding and implicit ARQ are three key points of this algorithm. The proposed algorithm reaches a good compromise between the successful delivery rate and work nodes. At last, computer simulations illustrate its effectiveness.