This book"s subtitle, "A Practical Guide to Internetworking", gives a more accurate indication of the ground it covers than the title. While all networking protocols are given space, pride of place goes to TCP/IP, Cisco routers and getting the two to cohabit peacefully on your network. So it"s most relevant to those networks running under UNIX and Windows NT 4.0.Essentially Understanding the Network is a primer, designed to lead the gentle reader through the minefield that is Internetworking and establish a grounding in the basics of building a multiprotocol network. The book claims to be aimed at all levels. However, its dry, techie content will appeal to system administrators, even though it kicks off covering absolute beginner material such as cabling, network topologies and the OSI 7 layer model.Further chapters are devoted to Internetworking technologies, such as Ethernet, Token Ring and FDDI, even though the latter two are now networking has-beens (as the author freely admits). Perhaps these should have been ditched to make room for subjects like VPN and QoS. Another subject that"s consiciously absent from the index is Windows 2000, recently released at publication. This is a shame, because Windows 2000 introduces numerous enhancements to the TCP/IP protocol. NetWare doesn"t get much attention either, though to be fair, the book is OS-neutral.Like so many computing titles, Understanding the Network is unashamedly US in origin. It devotes some space to the US phone system and the anti-trust upheavals it endured, knowledge of which is less than essential on this side of the pond. Similarly, its coverage of ISDN, a key Internetworking medium, is devalued by the US content. Still, there"s some compensation in the final third of the book, which is devoted to configuring Cisco routers (normally a command-line hell) and troubleshooting. The practical, in-depth advice found here is probably worth the cost of the book alone. --Roger Gann