Pras, Aiko

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Book reviews: Red Hat Linux Network Management Tools

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The Simple Times 12tation can either happen at installation time or duringruntime. As an example, consider an SNMP agentrunning on a Linux system. Some capabilities of thisagent may depend on the configuration options usedby the system administrator when installing the agent.Other capabilities may depend on the presence of certainoperating system features which are determined duringruntime.As noted before, agent capabilities specifications arerelatively static. Thus, the question is whether an agentcapabilities statement indicates exactly what an agentactually supports at any moment or whether an agentcapabilities statement defines the maximally possiblesupport. Either interpretation has its problems. Theresult is that agent capabilities statements are useful insome but not necessarily all environments.What should MIB compilers do with agent capabil-ities specifications?First, lets define the term MIB compiler. The termis simple, but there seem to be many interpretations.A MIB compiler should validate that a collection ofMIB modules is syntactically valid, and check that itis semantically valid as far as possible that can bedone by a computer program. (Note that much of thesemantics associated with a MIB module are specified intext for humans and not for computer programs.) Aftervalidation, a MIB compiler generates output in anotherformat that is directly usable or is input to anotherprogram. For example, a MIB compiler could create datastructure definitions and code stubs to assist in creatingan SNMP agent. Note that the data structures and stubcode for one agent implementation would probably be oflittle use for other agent implementations. Alternatively,a MIB compiler could output information that assists aprogram that graphs values of objects. There are manyuses.So what should a MIB compiler do with an agentcapabilities specification? Of course, a MIB compilershould validate agent capabilities specifications like allother SMIv2 constructs. Unfortunately, many MIBcompilers “skip over” agent capabilities specificationswithout any checking to see if they are valid. They dothis because implementors could not figure out what todo with the agent capabilities specifications. Other MIBcompilers try to use agent capabilities specifications todrive how data structures and stub code is generatedfor agents. My experience and belief is the opposite.That is, the control mechanisms that are used to specifythe implementation characteristics of an agent and usedto drive a code generator, should be used to drive thecreation of agent capabilities specifications.What should a MIB browser do with agent capa-bilities specifications?A MIB browser is a program that allows a user toexamine and change the values of MIB objects. It shouldalso allow the creation of new instances of objects. It ispossible for a MIB browser to give hints to its user aboutwhich objects can be accessed based on information froman agent capabilities specification. However, the benefitseems to be little. I am not aware of any MIB browserthat uses agent capabilities specifications.I have not seen any agent capabilities specifica-tions from vendors, why not?There are three primary reasons why equipment ven-dors do not ship agent capabilities specifications withtheir devices:1. It is difficult to get agent implementors to com-pletely document their implementation. It is “extra”work to do after they have finished. And it isoften almost impossible to create agent capabilitiesspecifications for old agents without re-engineeringthe agent implementation.2. The product marketing managers do not like topublish specifications that appear to look like buglists, even when an agent conforms to compliancespecifications.3. Since the agent capabilities are identified by OIDvalues, it is difficult for users to find the appropriateMIB modules. One of the most common requestson the SNMP news group is for MIB modules fromvendors that define a given OID value.Book ReviewsThe reviews published in this column represent the opin-ion of the author(s). Please contact the author(s) directlyif you want to share your comments. Please contactthe editors of The Simple Times if you are interested topublish your own book review in this column.Red Hat Linux Network Management ToolsReviewed by Aiko Pras, University of TwenteThe book starts with the usual explanation of TCP/IPand SNMP. Although the book was published in April2000, the explanation focuses on SNMPv1 and spendsonly a few words on SNMPv3. This is a missed opportu-nity, since the main tools discussed in the book alreadyVOLUME 8, NUMBER 1 SEPTEMBER, 2000The Simple Times 13support SNMPv3 and many readers may have questionsrelated to that version.After the introduction the book continues with some ofthe core Linux utilities and tools, such as arp, ifconfig,netstat, ping, tcpdump and traceroute. For each ofthese tools there are about 10 pages of text; this text maybe quite useful for many readers. The following sectiondiscusses additional system utilities and tools, suchas arpwatch, ethereal, fping, nmap and xtraceroute.Again, the text is useful, although some of the examplescould be shorter without loss of information.The remaining two third of the book focuses on SNMP.First there is a discussion of 80 pages on MIB-II; un-fortunately this discussion is very similar to the text ofRFC1213 and similar information is already availablefrom many other sources. After MIB-II, the book contin-ues with a discussion of UCD SNMP and SUN’s SolsticeEnterprise Agents. Although many readers may find theUCD-SNMP text valuable, it is unclear why a book withthe title “Red Hat Linux Network Management Tools”discusses tools for a Solaris platform. Fortunately, thetotal text on UCD-SNMP is much larger than the texton the SUN agent.After the discussion on agents, the book continueswith some of the most popular Web-enabled tools: mrtgand ntop. Although there is already many documen-tation on the Web related to these two packages, thebook is still interesting to read. The last chapters ofthe book concentrate on the Linux control panel andon scotty’s tkined. It is unclear why the discussion onthe Linux control panel was postponed until the end ofthe book; it would have been more logical to discuss itearlier. The chapter on tkined is quite useful; there areabout 50 pages of information which can not easily befound elsewhere. It is not clear, however, why the Tnmpart of the scotty package has not been discussed. Itwould have been a good replacement for the sections onthe SUN agent.The book is surely a valuable source of informationfor people relatively new to Linux based network man-agement. What is absolutely missing, however, arereferences to sources elsewhere. Although all packagesthat were discussed are contained on the two CDs thataccompany the book, the book should at least haveincluded the URLs from where the readers can downloadthe latest versions of these packages. In fact, except fora few examples like UCD-SNMP, the book does not evenmention the source and authors of these packages (thepublisher even claims that “the software and informa-tion on the diskette are the property of The McGraw-HillCompanies”!).Standards SummaryPlease consult the latest version of Internet OfficialProtocol Standards. As of this writing, the latest versionis RFC 2700.SMIv1 Data Definition LanguageFull Standards: RFC 1155 - Structure of Management Information RFC 1212 - Concise MIB DefinitionsInformational: RFC 1215 - A Convention for Defining TrapsSMIv2 Data Definition LanguageFull Standards: RFC 2578 - Structure of Management Information RFC 2579 - Textual Conventions RFC 2580 - Conformance StatementsSNMPv1 ProtocolFull Standards: RFC 1157 - Simple Network Management ProtocolProposed Standards: RFC 1418 - SNMP over OSI RFC 1419 - SNMP over AppleTalk RFC 1420 - SNMP over IPXSNMPv2 ProtocolDraft Standards: RFC 1905 - Protocol Operations for SNMPv2 RFC 1906 - Transport Mappings for SNMPv2 RFC 1907 - MIB for SNMPv2Experimental: RFC 1901 - Community-based SNMPv2 RFC 1909 - Administrative Infrastructure RFC 1910 - User-based Security ModelVOLUME 8, NUMBER 1 SEPTEMBER, 2000

Book reviews: Red Hat Linux Network Management Tools

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