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Server Load Balancing Review by Dr. Lee D. Carlson
Needs more examples
This book gives an organized but purely descriptive overview of server load balancing and should be helpful to anyone who is approaching the subject for the first time but does not require quantitative assessments of the different methods for doing server load balancing. It is written for the network administrator, but anyone, including network managers should find it helpful. Network engineers may find the treatment too qualitative, but it could be supplemented by more rigorous material if needed.
Chapter 1 is a brief overview of the history of load balancing and why it is needed in Internet environments. DNS-based, firewall, and global server load balancing are briefly discussed, along with clustering. This is followed in chapter 2 by a brief review of the OSI model and the different components involved in server load balancing. The author cautions that the use of VRRP (Virtual Router Redundancy Protocol) may cause problems if the load balancers become isolated from each other, but does not give any historical or test examples of this. The same holds true for his caution on the use of fail-over cables.
The discussion becomes a little more detailed in chapter 3, wherein the author discusses the actual functioning of a server load balancer. Direct server return is discussed, with its use of MAC address translation and loopback interfaces. Both server-based and switch-based load balancers are briefly discussed, but the author does not want to commit to which is the better architecture. The inclusion of some benchmarking studies would be helpful here.
Performance metrics, such as connections per second, total concurrent connections, and throughput are discussed in chapter 4. Although the discussion is purely descriptive, the author does give a "metrics matrix" that outlines what metrics are important for different types of traffic.
The author gets down to describing the network infrastructure needed to do server load balancing in chapter 5. The different possibilities for network infrastructure are classified according to the IP configuration (flat-based or NAT-based), the return path (bridge path, route path, or DSR), and physical connectivity (one-armed or two-armed). The advantages of the different types of SLB architectures are discussed briefly, but no real test cases or benchmarking studies are included.
The details of flat-based SLB network architectures are discussed in chapter 6. The simplicity of this architecture is emphasized, along with its ability to pass FTP and stream traffic more readily (no real examples given however).
I did not read the rest of the book which covers administrative matters, and so its review will be omitted.