Network Working Group C. Kalbfleisch
Request for Comments: 2039 OnRamp Technologies, Inc.
Category: Informational November 1996
Applicablity of Standards Track MIBs to Management of World Wide
Web Servers
Status of this Memo
This memo provides information for the Internet community. This memo
does not specify an Internet standard of any kind. Distribution of
this memo is unlimited.
This document was produced at the request of the Network Management
Area Director following the HTTP-MIB BOF at the 35th IETF meeting to
report on the applicability of the existing standards track MIBs to
management of WWW servers.
Requirements for management of a World Wide Web (WWW) server are
presented. The applicable existing standards track MIBs are then
examined. Finally, an analysis of the additional groups of MIB
attributes that are needed to meet the requirements is presented.
Table of Contents
1. Abstract.................................................12. Overview.................................................23. Requirements.............................................33.1 Operational Model Requirements...........................33.1.1. Host specific and Application Monitoring.................33.1.2. Dependencies among applications..........................33.1.3. Error generation and reporting...........................33.1.4. Capacity planning........................................43.1.5. Log Digester.............................................43.2. Service Model Requirements...............................43.2.1. Retrieval services.......................................43.2.2. Document information store -- managing documents.........43.2.3. Server configuration.....................................43.2.4. Server Control...........................................43.2.5. Quality of Service.......................................44. Relationship to existing IETF efforts....................54.1. MIB-II [2]...............................................54.2. Host Resources MIB [3]...................................54.3. Network Services Monitoring MIB [4]......................64.4. Application MIB [5]......................................7
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5. Summary of Existing Standards Track MIBs.................86. Definition of additional attributes......................97. Usage Scenarios.........................................118. Conclusion..............................................119. References..............................................1310. Acknowledgments.........................................1311. Further Information.....................................1412. Security Considerations.................................1413. Authors' Address........................................14
The World Wide Web (WWW) is a network of information, accessible via
a simple easy to use interface. The information is often presented
in HyperText or multi-media. The information is provided by servers
which are located all around the world. The usability of the web
depends largely on the performance of these servers. WWW servers are
typically monitored through log files. This becomes a difficult task
when a single organization is responsible for a number of servers.
Since many organizations currently use the Internet Standard SNMP to
manage their network devices, it is desirable to treat these WWW
servers as additional devices within this framework. This will allow
a single Network Management Station (NMS) to automate the management
of a number of WWW servers as well as the entire enterprise. Defining
a standard for this purpose allows a single management application to
manage a number of servers from a variety of vendors. Additionally,
a formal definition of what has to be managed and how to manage it
tends to lead to integrated and improved performance and fault
management.
Content providers are interested in the access statistics and
configuration of their sites. The content provider may be the same or
a different organization than the one that maintains the server as a
whole. It may be possible to realize the new paradigm of "Customer
Network Management" to provide this information to the content
provider. This means that there exists a distinct organization
different than the network operations center that is also interested
in the management information from a device. Customer network
management is desirable to allow each content provider on a server to
access information about his own documents independent of the rest.
Various organizations may be interested in SNMP manageable WWW
clients and proxies as well. At this time, our focus is on WWW
servers. A natural extension to this work could be a framework for
managing WWW Clients and general information retrieval systems like
WWW proxies, NNTP, GOPHER, FTP and WAIS. The focus of this document
remains the management of WWW servers.
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WWW servers can be viewed from several perspectives when assigning
management responsibilities. For the sake of discussion, these
perspectives are named the Operational Model and the Service Model.
The Operational Model views WWW servers as computers with hardware,
disk, OS and web server software. This model represents the actual
resources that make up the machine so that it can be monitored from
the perspective of resource utilization. The Service Model views the
WWW server as a black box that simply handles the responses to
requests from clients located on the web.
The two models compliment each other while providing distinct
information about the server. Members of the organization
responsible for the WWW server, may be interested in one and/or both
of the management models. For this reason, the management
information should be scalable, for one or both models to be
implemented independent of the other.
With this in mind, the requirements for WWW server management can are
summarized below by expanding upon those generated at the HTTP-MIB
BOF.
Some systems implement a number of services within a single piece of
code. Others use multiple pieces of code to implement the same set of
services. Because of this, dependencies develop among processes.
These dependencies become critical when a particular process needs to
be stopped, restarted or reconfigured. These dependencies need to be
defined within the management information so that management
applications can operate the systems correctly.
The WWW server generally reports errors via logging facilities. The
format of the log file is not well defined. It is required that a
standard facility for error reporting be utilized.
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It is required to obtain statistics which can be used for capacity
planning purposes. This includes planning for increased network
bandwidth, computing power, disk space, number of concurrent server
threads, etc.
WWW servers generally report status information by data generated in
Common Log Format [1]. This information needs to be preserved as
attributes in a MIB to facilitate remote monitoring providing a
standard way to represent and retrieve the management information.
Retrieval services are an abstract decoupling the information space
from the underlying transport mechanism. The goal at this time is to
focus on the requirements for management of WWW servers. There may be
considerable overlap with other types of servers like (FTP, NNTP,
GOPHER and WAIS). The term "retrieval services" is used here to
retain this abstraction. It is required to get statistics about the
usage and performance of the retrieval services.
Information from a WWW server can be static (a file) or dynamic (the
output of some processing). Management of these two types of
information sources range from maintaining access statistics and
access permissions to verifying the operational status of all
applications that provide the dynamic information.
In general, a WWW server is made up of or depends upon the following
components:
-a general purpose workstation running some operating system
-http server software to answers requests from the network
-various support routines like CGI programs or external
applications (like DBMS) used to access information
-a document store on one or more storage devices
The health and performance of each of the above components is of
interest when managing a WWW server.
There are a number of standards track MIB modules that are of
interest to the above list of items. This list includes MIB-II [2],
Host Resources MIB [3], Network Service Monitoring MIB [4] and
Application MIB [5].
This creates an impressive list of attributes to be implemented. A
definition of various levels of management of a WWW server is desired
so that the implementor may scale his implementation in chunks which
may include various components of each section. For instance, this
may allow customer network management without requiring the other
groups being implemented.
MIB-II defines the managed objects which should be contained within
TCP/IP based devices.
The WWW server should support the applicable portions of MIB-II.
This set probably includes, as a minimum, the following groups:
system, interfaces, udp, icmp, tcp and snmp.
This MIB defines a uniform set of objects useful for the management
of host computers independently of the operating system, network
services, or any software application.
The MIB is structured as six groups; each specified as either
"mandatory" or "optional". If ANY "optional" group of the MIB is
implemented, then ALL "mandatory" groups of the MIB must also be
implemented. This may cause implementation problems for some
developers since many of these attributes require intimate knowledge
of the OS.
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The groups defined by the MIB are:
-System Group Mandatory
-Storage Group Mandatory
-Device Group Mandatory
-device types
-device table
-processor table
-network table
-printer table
-disk storage table
-partition table
-file-system table
-file-system types
-Running Software Group Optional
-Running Software Performance Group Optional
-Installed Software Group Optional
The system group provides general status information about the host.
The storage and device groups define the information about the
configuration and status of the resources which compose the host. It
defines the resources which make up a generic host system and how
they relate to each other. Much of this information is useful for
managing various aspects of a WWW server, like the file system and
CPU utilization. This information is useful for meeting the
operational requirements. Much of this information is however more
detailed than many WWW server managers require for service level
requirements.
The remaining groups define software components which are installed
and/or running on the host. Performance information is defined which
extends that defined for each running process. Unfortunately, the
mapping between running software and installed software is difficult
since it is related by a foreign key (Product ID) which does not
appear to be required to exist in either table [6]. There is no
provision to represent a group of processes which together perform
some task (IE an application made up of multiple processes). The
Applications MIB WG plans to address these deficiencies.
This MIB is one of three documents produced by the MADMAN (Message
And Directory MANagement) Working group. It defines a set of general
purpose attributes which would be appropriate for a range of
applications that provide network services. This definition is from
the perspective of the service without considering the implementation
in terms of host computers or processes. Attributes provide
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statistics and status on the in-bound and out-bound associations that
are currently active, and which have been active.
This MIB is intended to be the minimum set of attributes common
across a number of Network Service Applications. Additional
attributes are to be defined as necessary to manage specific network
service applications. WWW servers clearly fall into the category of
network service applications. All attributes in this MIB are
relevant to WWW servers.
The MIB consists of two tables:
-applTable Mandatory
-assocTable Optional
The applTable describes applications that provide network services
and keeps statistics of the current number of active associations and
the total number of associations since application initialization.
The assocTable contains more detailed information about active
associations.
The other two MIBs defined by MADMAN, MTA MIB [7] and DSA MIB [8],
are not relevant to the management of WWW services. They do,
however, demonstrate how to extend the Network Services Monitoring
MIB for a specific set of applications.
The Application MIB WG is defining two separate MIBs: the sysApplMib
and the applMib. The first defines attributes that can be monitored
without instrumenting the applications. The second will define
additional attributes requiring application instrumentation.
The sysApplMIB allows for the description of applications as a
collection of executables, and files installed and executing on a
host computer. The objects support configuration, fault and
performance management of some of the basic attributes of application
software.
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The groups defined in the sysApplMIB are:
-System Application Installed Group Mandatory
-sysApplInstalledTable
-sysApplCfgElmtTable
-System Application Run Group Mandatory
-sysApplRunTable
-SysApplPastRunTable
-sysApplElmtRunTable
-sysApplElmtPastRunTable
The sysApplInstalledTable captures what applications are installed on
a particular host and the sysApplCfgElmtTable provides information
regarding the executables and non executable files which collectively
compose the application. The sysApplRunTable contains the application
instances which are currently running and the sysApplPastRunTable
contains a history about applications which have previously executed
on the host. The sysApplElmtRunTable contains the process instances
which are currently running and sysApplElmtPastRunTable contains a
history about processes which have previously executed on the host.
It should be noted that two implementations of the same set of
network services may each define a different set of processes and
files within this MIB. Ultimately enough management information is
needed so that these different implementations can at least be
managed similarly.
WWW servers fall into the general category of application software.
Therefore the attributes of this MIB are applicable if the process
level detail is requested to meet the Operational Model requirements.
The Application MIB WG is to resolve the problems described above
with the relationship between the running and installed software of
the Host Resources MIB.
The existing MIBs are largely orthogonal as demonstrated by the
diagram below. Host Resources relates network information to the
interfaces defined in MIB-II. The system application MIB relates its
running element table to the equivalent entry in the Host Resources
running software table.
It should be noted that the running software of the Host Resources
includes ALL software running on the host, while the running element
table of the system application MIB only includes "interesting"
processes of monitored applications.
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In the diagram below, "Other Services", "Application Specific MIBs"
and "Application MIB" represent work to be done or in progress.
+---------------+
| Application |
| Specific MIBs |
+---------------+
|
+--------+ +---+ +---+ +---------------+
|Other | |MTA| |DSA| | Application |
|services| |MIB| |MIB| | MIB |
+--------+ +---+ +---+ +---------------+
| | | |
+--------------------+ +---------------+ +--------------+ +------+
| Network Services | | System | |Host Resources| |MIB-II|
| Monitoring MIB | |Application MIB|--| MIB |--| |
+--------------------+ +---------------+ +--------------+ +------+
The stack of MIBs above "Network Services Monitoring MIB" represent
monitoring from the Service Model. The other stacks represent
monitoring from the Operational Model. Neither of these stacks goes
to the level of specific detail for any application. The author is of
the opinion that HTTP or Web Server specific MIBs would exist at the
top of each stack to represent the service and implementation view of
the server respectively. There should be a relationship between
these two perspectives defined so that the correlations between the
two perspectives is possible. This relationship would be useful for
general application and service monitoring in addition to just web
servers. However, it is not of specific interest to either the
MADMAN WG or the Application MIB WG. It is therefore suggested that
such a relationship is defined in a general case outside of either of
those groups that would be applicable for WWW servers as well as for
other application to service mappings.
The existing MIB attributes meet the Operational Model Requirement
for tracking information specific to a host. Specifically, MIB-II,
Host Resources and the Applications MIB address these items. The
Network Services MIB addresses a portion of the service model
requirement for the decoupling of the information space from the
transport mechanism.
Several sets of additional attributes are needed to meet the
remaining requirements. These additional attributes may be generally
applicable to other network information retrieval services (like FTP,
NNTP, GOPHER and WAIS) as well as client and proxy management.
Management of these services is not the scope of this document.
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These additional attributes can be classified as:
1) Definition of relationship between the Network Services Monitoring
and Application MIBs. This allows the functional organization of
the server to be known. It allows the management application to
understand the effect of restarting specific processes on the
services provided. This addresses the Operational Model
requirement to model dependencies between applications.
2) Additions to generic Network Services Monitoring MIB. A draft [9]
has already been circulated due to the work of a mailing list and
a sample implementation. These attributes list a summary at the
service level of the configuration and the health of the server.
From this, performance metrics can be observed. In addition, the
health of the server in terms of data timeouts is known. These
attributes address the requirement for Operational Model tracking
of specific activity and the requirement for Service Model
retrieval services.
3) Document storage and access statistics are needed to address
service model requirements.
4) Additions to Application MIB are required to address server
configuration requirements in the service model.
5) Error and fault management attributes are required to address
requirements for tracking specific activity of the web server.
6) Configuration and Control are items that may be able to be defined
in a general way within the applications MIB. If not, a specific
definition would be required here.
Of the items listed above, (1) is needed on a general basis. The
others appear to the author as WWW server specific unless the scope
of the work is opened to WWW clients and proxies as well as other
services (like NNTP, FTP, GOPHER and WAIS).
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The example scenario will be a single host computer which implements
WWW services using the "virtual domain" concept. In this model, a
single host performs as the WWW server for one or more addresses.
For the purpose of example, we will specify that there are three
domains being serviced from this host whose WWW servers are:
-www.a.com
-www.b.com
-www.c.com
Some implementations may implement these services as one set of
processes that handle requests for each of the addresses. Others may
implement these services as a set of processes for each address.
This means that the relationship defined between the Network Services
Monitoring MIB and Application MIB components of the management
information may vary between different implementations of the same
configuration.
MIB-II and Host Resources would provide the information about the
host including the CPU, disk and network. The Host Resource running
table provide information on the processes in the system.
There would be an entry in the Network Services Monitoring applTable
for each virtual domain. In addition, the assocTable shows which
connections are currently active. An extension to the association
table would be helpful to provide information as to what is being
transmitted.
The sysApplMib would have entries in its installed software tables
for the web server software and each "interesting" component. This
should include the server binary, CGI programs, configuration files
and possibly the server log files. Depending on the implementation
of the server, the processes for each domain may show up in the same
or different running software tables.
Additional information as described in the previous section would
round out the management information that would be available for the
WWW server.
A number of currently defined attributes are useful for management of
a WWW server. Specifically, MIB-II and Host Resources should be
considered for monitoring the health of the machine in terms of host
and network configuration and capacity. The Network Services
Monitoring MIB and the Application MIBs provide a general framework
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to represent the components of the WWW server from both a service and
implementation perspective. The Network Services Monitoring MIB
suggests that extensions are necessary to cover specific network
application monitoring. A set of such attributes can be well defined
to provide status information of the WWW server. The Application MIB
suggests similar extensions. Some of these attributes may be generic
to all applications, and thus be implemented within the scope of the
applMib. It is the opinion of this author that there will still
remain specific instrumentation for WWW servers that can not, and
should not, be covered in the Network Services Monitoring and
Application MIBs.
Since the Network Services Monitoring MIB and the Applications MIB
represent orthogonal efforts of management, it is desirable to define
the relationship between the two in a standard way. This definition
is probably more than a simple pointer from one table to another.
Since it is outside the scope of either of those efforts, it is this
author's opinion that that definition could and should be addressed
within the scope of defining management of a specific application (IE
WWW servers). This defintion although defined for a particular
application, should be useful in a general way to describe the
relationship between the Network Services Monitoring MIB and the
Applications MIB.
Additional attributes are needed in order to meet all of the
requirements specified in this document. An IETF standard would
prevent independent developments of this effort in many enterprise
MIBs. It also allows management applications to control servers from
multiple vendors. It is likely that as the work in this area
progresses, the management information will be useful for other
Network Information Retrieval services (like FTP, GOPHER, WAIS and
NNTP) as well.
Finally, the Operational Model and Service Model Requirements lead to
two main uses of the management information. Design of the MIB
including the usage of the existing MIBs should allow one or the
other or both of these models to be implemented in a standard way.
This may be desirable depending specifically on the audience of the
data, the cost of instrumentation and the resources of the system.
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[1] Anonymous, "Logging in the W3C httpd",
http://www.w3.org/hypertext/WWW/Daemon/User/Config/Logging.html,
W3C, July 1995.
[2] McCloghrie, K., and M. Rose, Editors, "Management Information
Base for Network Management of TCP/IP-based internets: MIB-
II", STD 17, RFC 1213, Hughes LAN Systems, Performance
Systems International, March 1991.
[3] Grillo, P., and S. Waldbusser, "Host Resources MIB", RFC 1514,
Network Innovations, Intel Corporation, Carnegie Mellon
University, September 1993.
[4] Kille, S., and N. Freed, "Network Services Monitoring MIB",
RFC 1565, ISODE Consortium, Innosoft, January 1994.
[5] Saperia, J., C. Krupczak, R. Sturm, and J. Weinstock, "Definition
of Managed Objects for Applications", Work in Progress.
[6] Krupczak, C. and S. Waldbusser, "Applicability of Host Resources
MIB to Application Management", Empire Technologies, Inc.,
International Network Services, October 1995.
[7] Kille, S., and N. Freed, "Mail Monitoring MIB", RFC 1566, ISODE
Consortium, Innosoft, January 1994.
[8] Mansfield, G., and S. Kille, "X.500 Directory Monitoring MIB",
RFC 1567, AIC Systems Laboratory, ISODE Consortium, January 1994.
[9] Hazewinkel, H., E. van Hengstum, A. Pras, "Definitions of Managed
Objects for HTTP", Work in Progress.
This document was produced at the request of the Network Management
Area Director following the HTTP-MIB BOF at the 35th IETF meeting to
report on the applicability of the existing standards track MIBs to
management of WWW servers.
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The author gratefully acknowledges the comments of the following
individuals:
Ned Freed, ned@innosoft.com
Innosoft, Inc.
Harrie Hazewinkel, hazewink@cs.utwente.nl
University of Twente
Cheryl Krupczak, cheryl@empiretech.com
Empire Technologies, Inc.
Rui Meneses, rui.meneses@jrc.it
Centre for Earth Observation
Jon Saperia, saperia@bgs.com
BGS Systems, Inc.
Juergen Schoenwaelder, schoenw@cs.utwente.nl
University of Twente
Chris Wellens, chrisw@iwl.com
InterWorking Labs, Inc.
The current status of the HTTP-MIB standardization can be found on
the World Wide Web at <URL:http://http-mib.onramp.net/>. An email
list is in operation for discussion of this topic. To subscribe,
send email to "http-mib-request@onramp.net" with the message body of
"subscribe HTTP-MIB".