IEEE 802.1w Rapid Spanning Tree Protocol (RSTP) enhances the 802.1D standard with one goal in mind: improving STP convergence. To do so, RSTP defines new variations on BPDUs between switches, new port states, and new port roles, all with the capability to operate backwardly compatible with 802.1D switches. The key components of speeding convergence with 802.1w are as follows: ■ Waiting for only three missed Hellos on an RP before reacting (versus ten missed Hellos via the ..
Converging to a New STP Topology
STP logic monitors the normal ongoing Hello process when the network topology is stable; when the Hello process changes, STP then needs to react and converge to a new STP topology. When STP has a stable topology, the following occurs: 1. The root switch generates a Hello regularly based on the Hello timer. 2. Each non-root switch regularly (based on the Hello timer) receives a copy of the root’s Hello on its RP. 3. Each switch updates and forwards the Hello out its Desi..
Good Network Security Is Predictable
It is 3 a.m. and you are sleeping like a baby. That's great because you've spent many late nights protecting your new e-commerce site with the best security devices and software money can buy. You have a pair of firewalls that can handle an OC-48, NIDS boxes that allow you to craft your own complex signatures, a very expensive alarm and reporting tool that generates reports for your boss every morning, and the latest in file system checking and log analyzers for your servers...
Frame Relay Compression Design Guidelines
There are many conditions to consider when deploying data compression on WAN connections. Very often, the main cause for using compression is when bandwidth is a major concern. The whole purpose of using compression is to reduce transmission overheads and maximize the available bandwidth. This section takes a look at several compression design issues network administrators typically encounter when faced with the decision of whether to use compression. Design of the Existing..
Preventing Routing Domain Loops with Higher Metrics
One easy method of preventing the domain loop problem is to assign purposefully high metric values when redistributing routes. For example, consider the case shown in Figure 10-3, with a RIP domain on the left, and OSPF on the right. In this case, the two routers doing the redistribution (RD1 and RD2) assign OSPF metric 500 when redistributing routes into OSPF, and metric 5 when redistributing routes into RIP. First, focus on routes inside the RIP domain. This design preve..
