OSPF Design in Light of LSA Types

OSPF’s main design trade-offs consist of choosing links for particular areas, with the goal of speeding convergence, reducing memory and computing resources, and keeping routing tables small through route summarization. For instance, by using a larger number of areas, and the implied conversion of dense types 1 and 2 LSAs into sparser type 3 LSAs, the OSPF LSDBs can be made smaller. Also, link flaps in one area require SPF calculations only in that area, due to the partial ..

Convergence Times

Another distinguishing characteristic of routing protocols is speed. Convergence times aregenerally grouped as slow or fast. Fast convergence means that the routing protocol is ableto recognize a problem and fix it faster than a user can call to report the problem. Slowprotocols, such as RIP and IGRP, can take minutes to converge. Fast protocols, such asOSPF, IS-IS, and EIGRP, generally converge in less than ten seconds. Table 1-7 shows the convergence speeds of the routing ..

Everything Is a Target

As a designer of secure networks, one of the first things you must consider is the vast interdependency of today's larger networks. The Internet is the best example, but within each organization there exists a microcosm of the Internet. From an attacker's perspective, these interdependencies allow for the attacker's goals to be met in any number of ways. As an example, assume an attacker wants to bring down your website. The following list outlines the attacker's options: ..

Using Priority Queuing

To enable priority queuing on an interface, you must first define the priority list, and then you can apply it to the interface: Router#configure terminal Enter configuration commands, one per line.  End with CNTL/Z. Router(config)#access-list 101 permit ip any any precedence 5 tos 12 Router(config)#access-list 102 permit ip any any precedence 4 Router(config)#access-list 103 permit ip any any precedence 3 Router(config)#priority-list 1 protocol ip high list 101 Router(..

Configuring Discard Eligibility (DE)

The users can opt to specify which Frame Relay packets should have a lower priority or time sensitivity and should be subjected to be dropped when the Frame Relay switch experiences congestion. The Discard Eligibility (DE) mechanism allows the Frame Relay switch to identify packets that can be dropped during network congestion. This command assumes that the Frame Relay switch is able to detect and recognize the DE bit and to take action accordingly. Some Frame Relay switches ..