NET 226 - Designing Internetwork Solutions

Chapter 9, Developing Network Management Strategies


This lesson concerns making choices about managing your network. Objectives important to this lesson:

  1. Network management design
  2. Network management architectures
  3. Selecting tools and protocols

Chapter 9

Network management design

The text recommends that we should consider management of a network "from the beginning" of our design process. There have been a few hints about this along the way, and now we have a chapter about it. The text recommends that we select our management tools carefully, because too much measurement will slow down the network, and too little will not give us reliable data on its performance. The text suggests on page 264 that we should use proactive management, measuring the performance during regular operations so we can recognized normal performance and see any trouble as it develops. Reactive management measures performance only when there is a suspected problem, which can be less time consuming, but it does not give us a baseline for network performance, and it will not find problems as they develop, which is a better way to avoid down time.

The text introduces five categories of management that are endorsed by ISO:

  • Fault management - This is about managing problems and failures. The text states that it includes reporting problems to users, which is a function that many IT people consider as an afterthought. Communication with our customers about problems is not an option, it is a requirement. The text recommends that we have reporting tools and problem documentation tools along with tools to monitor and detect problems. Such tools are often based on Simple Network Management Protocol (SNMP) and Remote Monitoring (RMON). The text mentions that Cisco devices produce messages about faults that are tagged with one of eight levels of importance. These messages can be sent to a network management system if desired.
  • Configuration management - Devices, whether on or off a network, can often be installed in several different ways, and they can be configured differently by each person who installs them. A configuration management system can help us provide a standard configuration for various devices, and manage allowed customization. This kind of system can also be used to build and maintain an inventory of network-attached devices. The text mentions that DHCP is an example of a protocol that supports these ideas, and that VLAN Trunking Protocol (VTP) is useful for updating switches with information about VLANs.
  • Accounting management - The text explains that the purpose of accounting management software is to measure use of a network, typically for billing for actual usage. There is also a value to such a system as a problem detection tool, because it will detect large scale usages of network resources which can be examined for abuse or actual business need.
  • Performance management - The text lists several types of performance that should be measured on a network. It clusters them into two categories: end-to-end performance describes performance across all components used in a network service, and component performance measures the performance of specific devices. Measuring the performance of a network from one extremity to another is often done to measure what is supposed to be the performance across the farthest distance. The text mentions that a ping is commonly used for a quick test of this sort, and reminds us that a ping is actually an Internet Control Message Protocol (ICMP) echo request. It is not common for the farthest points in a network to be in the busiest circuits, so we should expect to measure heavily used routes as well, measuring the throughput between various points to find bottlenecks. The text cautions us not to depend on measurements taken with traceroute, because some routers are not programmed to respond as the protocol assumes they will. (See pages 267 and 268.)
  • Security management - A security management system should asssist in providing IDs and passwords to users, in creating and managing encryption keys, and in analyzing the security features of networking and internetworking devices. A security management system should also examine audit logs, which may be created by security or accounting processes
Network management architectures

The text presents a short section on architectures, which may be best understood by examining the graphic on page 269. There are three parts to the architecture displayed there:

  • a managed device - Almost any device on a network may be used to collect and report information to a management system. The text suggests routers, servers, switches, bridges, hubs, end user systems, and printers.
  • an agent - Software that runs on the managed device to collect network information. After collection, the agent will pass the data to the next level in the architecture.
  • a network management system (NMS) - May be implemented as a database and aanalysis system running on higher end hardware. It controls the managed devices and its agents, and it provides analysis and reports from the data. There may be a separate NMS for each kind of management being done on the network.

Network management may be done in-band or out-of-band. In-band systems use the network they are monitoring to carry their data to the NMS. Out-of-band systems use a separate channel to carry their data.

Selecting tools and protocols

SNMP - As discussed above, this protocol is a standard for management systems. The text recommends SNMPv3 or later for better security and authentication features.

Management Information Base (MIB) - The description in the text matches thhe discussion of architectures above. An MIB gathers information from deployed agents and looks for problems in the network.

Remote Monitoring (RMON) - The IETF apparently felt that MIBs didd not collect adequate information on traffic in the bottom two layers of the ISO network model. They developed RMON to watch for problems in these layers.

The chapter concludes with a discussion of some Cisco protocols that also provide management and troubleshooting information. You should review the summary of protocols discussed in the chapter that appears on page 277.

Week 9 Assignment: Chapter 9

  • From Chapter 9:
    • Review Question 4 on page 278
  • Review for the third test next week