The Assured Forwarding PHB and DSCP Values
The Assured Forwarding (AF) PHB (RFC 2597) defines four classes for queuing purposes, along with three levels of drop probability inside each queue. To mark packets and distinguish into which of four queues a packet should be placed, along with one of three drop priorities inside each queue, the AF PHB defines 12 DSCP values and their meanings. The names of the AF DSCPs conform to the following format: AFxy where x implies one of four queues (values 1 through 4), and y impli..
Calculating the Cost of a Path to Another Area
OSPF calculates the costs of paths to other areas differently than it calculates paths to other routing domains. The path to another area is calculated as the smallest cost to the ABR, added to the smallest cost across the backbone. Thus, if there were two paths from the ABR into the backbone, the shortest (lowest-cost) path would be added to the cost of the path to the ABR. External routes are routes from another routing domain. External routes discovered by OSPF can ..
Just as the Internet hierarchy had to adapt to accommodate an increase in players, so has the enterprise network. Early data networks facilitated the basic requirement of communication between terminals and a central mainframe. The need for a simple hierarchy, from terminal to IBM cluster controllers to front -end processors, was readily apparent from this basic requirement. In today's world of peer-to-peer networking, however, the reasons for network hierarchy and its inner ..
Appreciating what QoS tools and methods do to packets in a network is fundamental to appreciating the effect of individual QoS tools discussed in later chapters, and ultimately understanding the network designs and methods that constitute the material in this book. End-to-End QoS Regardless of how it is measured, QoS is a vital element in any converged network. To ensure the highest level of quality, however, QoS must be implemented across all areas of the network. QoS is d..
DLSw+ Redundancy and Fault Tolerance
There are several things you can do to improve the reliability and fault tolerance of your network. Many of these solutions have the added benefit of improving performance. The first important thing to consider is having more than one DLSw peer router connected to the mainframe's Token Ring. In this case, you will want to make sure that you balance the load between the two peers as much as possible: dlsw-branch#configure terminal Enter configuration commands, one per line.&n..
