ABSTRACT
Introduction .......................................................................................................... 48 Overview .............................................................................................................. 49
Defi nition of Communications Networks ................................................... 49 Layering Concept in Communication Networks and Protocols ................. 49 Standard Organizations ............................................................................... 51 Brief History of Communication Networks ............................................... 53
Types of Communication Networks .................................................................... 53 Local Area Networks .................................................................................. 53 Wireless LANs ............................................................................................ 56 Campus Networks ....................................................................................... 61 MANs and WANs ....................................................................................... 62
The Internet ..................................................................................... 66 Wireless WANs ............................................................................... 68
Communications Layers and Protocols ............................................................... 70 Application Layer Functions and Protocols ............................................... 70
WWW Applications and Related Protocols .................................... 70 E-Mail Applications and Related Protocols .................................... 71
Transport Layer Functions and Protocols ................................................... 73 Port Numbers .................................................................................. 73 Segmentation and Reassembly ....................................................... 74 Message Delivery ............................................................................ 75 Other Transport Layer Protocols .................................................... 76
Network Layer Functions and Protocols .................................................... 76 Addressing Function ....................................................................... 77 Routing Function ............................................................................ 80
Data Link Layer Functions and Protocols .................................................. 81 MAC Function ................................................................................ 81 Error Control Function ................................................................... 82 Message Delineation and Formatting Function .............................. 82
Physical Layer Functions and Protocols ..................................................... 83 Characteristics of Physical Media .............................................................. 84
Analog versus Digital Transmission ............................................... 84
Techniques for Transmitting Digital Data over Digital Circuits ................................................................. 84
Techniques for Transmitting Digital Data over Analog Circuits ................................................................ 85
Techniques for Transmitting Analog Data over Digital Circuits ................................................................. 86
Network Design and Management ....................................................................... 86 Future Trends ....................................................................................................... 88
Gigabit Ethernet Trends .............................................................................. 88 Next Generation Internet ............................................................................ 88 4G Cellular Networks ................................................................................. 89 Wireless Ad Hoc Networks and WSNs ....................................................... 90
Bibliography ........................................................................................................ 90
Networking in general has become mission critical so much so that integrated and effi cient use of all networking technologies available in an enterprise is essential in carrying out its mission. This chapter provides the state of the knowledge on various technologies and concepts used in networking, especially from an enterprise perspective. The rest of the chapter is organized into fi ve additional sections as follows:
Overview-This section starts with a defi nition of a communications net-• work and its components, and continues with a discussion of the network models and layering concept along with standardization of the protocols and interfaces. It concludes with a brief history of communications networking. Types of Communications Networks-This section provides a detailed dis-• cussion of various types of communications network used in an enterprise. This includes Local Area Networks (LANs), Metropolitan Area Networks (MANs) and Wide Area Networks (WANs). The Internet and cellular networks are also discussed in this section as two popular and important examples of WANs. Communications Layers and Protocols-This section discusses the major • protocols used in communications networks. The discussion is structured around the Internet layers, namely: application layer, transport and network layers, data link layer, and physical layer. Communications Network Design and Management-This section provides • a brief discussion of the design and management of communication networks. The topic of network security is also discussed. Future Trends-Finally, the future networking techno logies such as perva-• sive networking, wireless ad-hoc networks, and wireless sensor networks (WSNs) are overviewed.
