A computer network, is a collection of computers and devices interconnected by communications channels that facilitate communications and allows sharing of resources and information among interconnected devices. In other words, a computer network is a collection of two or more computers which are linked together for the purposes of sharing information, resources, among other things.As today, all the media in the world are standing on data communication and computer networking,it is always important to understand the basics of networking. In the present book, the different types of network topology, details of baseband and broadband are described. There is a precise overview on data and signal bits. The book also described the modulation and multiplexing in computer networking. Different type of data transmission and details of ethernet and TCP/IP are also described in this book.