Bridges, Routers, Switches, and Internetworking Protocols

Radia Perlman

Addison-Wesley 2000
A book review by Danny Yee © 2000
Interconnections is aimed at computer science students studying networking: it covers fundamental concepts and basic theory, and includes a set of "homework" problems with each chapter. But it is solidly grounded in real-life experience — Perlman has spent years designing and implementing network protocols and algorithms (most notably the spanning tree algorithm used in most bridges) and uses that experience to provide practical illustrations of the theory. She is also fun to read, being prepared to laugh at things that deserve it and to offer personal opinions, sometimes quite bluntly.
"I find BGP scary. It is configuration-intensive. Routes can be permanently unstable. It solves only whatever it happens to solve rather than providing a general-purpose solution. But we're stuck with it."

Perlman roughly follows the protocol stack upwards. Four chapters cover general data-link layer issues, transparent and source-routing bridges, the various categories of hub/switch/bridge, and VLANs. Five chapters on the network layer cover connection-oriented protocols (X25 and ATM) and general issues, addressing, and packet formats in connectionless networks, with examples from a range of protocols including IP, IPX, IPv6, CLNP, Appletalk, and DECnet. A chapter covers autoconfiguration and endnode issues (protocols such as ARP). And there are five chapters on routing, covering general routing concepts (distance vector and link state algorithms, link costs and types of service), implementation (algorithms for fast packet forwarding), and specific routing protocols (from RIP to BGP), as well as the more specialised topics of WAN multicast and "sabotage-proof routing".

The bulk of Interconnections may be too detailed for most network administrators or programmers, but those without an interest in the theory may want to track down a copy just for the last two chapters. "To Route, Bridge, or Switch: Is That the Question?" is a good overview of networking terminology and its connection with reality, while "Protocol Design Folklore" attempts

"to capture the tricks and 'gotchas' in protocol design learned from years of layer 2 and layer 3 protocols. Interspersed among the text are boxes containing 'real-world bad protocols.' They share with you the warped way I look at the world, which is to notice and be distracted by suboptimal protocols in everyday life."
Interconnections will do much to improve understanding of networks and network protocols: as well as being an excellent textbook it should command a general audience among computing professionals.

November 2000

External links:
- buy from or
Related reviews:
- Radia Perlman - Network Security: PRIVATE Communication in a PUBLIC World
- books about networking
- books published by Addison-Wesley
%T Interconnections
%S Bridges, Routers, Switches, and Internetworking Protocols
%A Perlman, Radia
%I Addison-Wesley
%D 2000
%O hardcover, 2nd edition, exercises, glossary, index
%G ISBN 0201634481
%P x,537pp