Internet Draft Web Based Management June 13, 1996
Web Based System and Network Management
<draft-mellquist-web-sys-00.txt>
Brian Harrison
Hewlett-Packard Company
harrison@ppg01.sc.hp.com
Peter E. Mellquist
Hewlett-Packard Company
mellqust@hprnd.rose.hp.com
Adrian Pell
Hewlett-Packard Company
arp@hplb.hpl.hp.com
June, 13 1996
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its
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1. Abstract
This document describes the application of the Hyper Text
Transfer Protocol (HTTP) for system and network management.
Presented are mechanisms which facilitate system and network
management including the discovery of HTTP management entities,
how management content may be accessed, and lastly, the role of
a Simple Network Management Protocol (SNMP) agent providing
SNMP information through the use of HTTP.
Management and HTTP may be categorized into two groups, the
management of HTTP[3] and management using HTTP. The focus of
this document is on the latter, "web based management".
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2. Overview
Web based management is the application of World Wide Web (WWW)
tools for the management of systems and networks. This includes
using HTTP servers and browsers for providing static, dynamic and
interactive content of management information. An HTTP server
acting in a management role can provide information in a variety
of forms including Hyper Text Markup Language (HTML), graphics,
executable code and binary encoded information. Together, this
capability allows HTTP to function as a powerful protocol for
the management of systems and networks. For HTTP servers acting
in a management role, the HTTP server may also be providing non-
management content. It is therefore necessary to provide a mechanism
for a WWW browser or network management application to have direct
access to the management information.
As presented in this document, HTTP is not meant to replace SNMP.
HTTP working together with SNMP can provide many benefits including
ease-of-use, zero client-side installation, and security. SNMP
is required for the instrumentation of systems and networks.
3. HTTP Management Transport Control Protocol (TCP) Port Definition
The standardized TCP port for HTTP is port 80 [1]. A HTTP server
listening on this port may provide content spanning a wide
information base including non-management related content.
For management usage, this requires that the management content
be inter-mixed with non-management content. A WWW browser or
network management application must therefore have knowledge or
the ability to determine where the management content resides on
a HTTP server. A well known HTTP management TCP port solves this
problem by allowing only management content through the HTTP
management interface. This allows a browser or network management
application to easily use or discover a HTTP server acting in a
management role. The proposed HTTP management TCP port is
port 280 (The actual port number is pending IANA[4] approval). The
recommended port for management is therefore port 280. In cases
where this port is not available, port 80 may be used. An
alternative to a standardized HTTP management port, a standardized
Universal Request Indicator (URI), was considered. Although this
mechanism could work, it was decided that the problems of
attempting to standardize on a character sequence would prove to
be too difficult.
A HTTP server operating in a management mode on port 280 may
also be using port 80 for non-management content. This allows
for the clean separation of management and non-management
content. A TCP port 280 interface should only supply management
content. A HTTP server which does not utilize TCP port 280 for
management content may inter-mix management and non-management
content on port 80. In this case, a browser or network management
application must determine the HTTP management capability through
other means, see HTTP Manageable MIB.
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4. HTTP Manageable MIB
A SNMP agent in operation together with an HTTP server allows
management information to be accessed using either the SNMP
protocol or using HTTP. In order to determine if an SNMP agent
also supports HTTP, a SNMP Management Information Base (MIB) is
utilized. The "HTTP Manageable MIB" provides SNMP objects which
advertise an agent's HTTP capabilities. This allows a network
management application using SNMP to query the "HTTP Manageable
MIB" to determine its HTTP management capabilities and interface.
The presence of this MIB in an agent implies that a HTTP server is
operational in a management context. In order to determine the
exact interface for HTTP access, the "HTTP Manageable MIB" provides
a MIB object, "httpMgDefaultURL". This object represents the
complete Universal Request Locator (URL) for management access to
the agent via HTTP. The value of this URL will reflect port 280
usage when applicable.
A second MIB object defines an agent's capability to perform SNMP
over HTTP. The "httpMgSNMPEnabled" object represents a truth
value indicating if the HTTP server can perform SNMP over HTTP.
If set true, the HTTP server supports the SNMP over HTTP tunneling
protocol as described in the subsequent section.
Below is the MIB definition for the "HTTP Manageable MIB". Note, the
MIB is currently designed to reside under the Hewlett-Packard MIB
branch. The long term intent will be to move this MIB under a
standard branch (The actual MIB branch is pending IANA[4] approval).
HP-httpManageable-MIB DEFINITIONS ::= BEGIN
IMPORTS
OBJECT-TYPE, MODULE-IDENTITY, NOTIFICATION-TYPE
FROM SNMPv2-SMI
DisplayString, TruthValue
FROM SNMPv2-TC
OBJECT-GROUP, MODULE-COMPLIANCE
FROM SNMPv2-CONF;
hp OBJECT IDENTIFIER ::= { enterprises 11 }
nm OBJECT IDENTIFIER ::= { hp 2 }
hpWebMgmt OBJECT IDENTIFIER ::= { nm 36 }
httpMgMod MODULE-IDENTITY
LAST-UPDATED "9606120000Z"
ORGANIZATION "Hewlett-Packard Web-based Management Working Group"
CONTACT-INFO
"WG E-mail: webmgmt@sysman.hpl.hp.com
Chair: Brian Harrison
Postal: Hewlett-Packard
5301 Stevens Creek Blvd
Santa Clara CA 95052 USA
Tel: +1-408-553-3786
Fax: +1-408-553-2909
E-mail: harrison@ppg01.sc.hp.com"
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DESCRIPTION
"Management information for HTTP manageable devices.
This MIB gives SNMP systems information on how to
manage a device using HTTP."
REVISION "9606120000Z"
DESCRIPTION "Initial Version"
::= { hpWebMgmt 1 }
httpMgTraps OBJECT IDENTIFIER ::= { httpMgMod 0 } -- future
httpMgObjects OBJECT IDENTIFIER ::= { httpMgMod 1 }
httpMgGroups OBJECT IDENTIFIER ::= { httpMgMod 2 }
httpMgCompliances OBJECT IDENTIFIER ::= { httpMgMod 3 }
-- MIB Objects
-- Default attributes for managing via HTTP
httpMgDefaults OBJECT IDENTIFIER ::= { httpMgObjects 1 }
httpMgDefaultURL OBJECT-TYPE
SYNTAX DisplayString
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"A Uniform Resource Locator (URL), as defined in RFC1738,
for the default management information for this device.
This URL is typically used by a HTTP browser to display
management information for this device. This default
page should contain links to any other management
pages for this device."
::= { httpMgDefaults 1}
httpMgSNMPEnabled OBJECT-TYPE
SYNTAX TruthValue
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"Indicates whether a HTTP server supports SNMP
over HTTP where SNMP requests may be contained
in the Entity-Body of a HTTP POST operation"
::= { httpMgDefaults 2 }
-- Compliance statements
httpMgMinCompliance MODULE-COMPLIANCE
STATUS current
DESCRIPTION
"The compliance statement for SNMP entities which
are http manageable."
MODULE -- this module
MANDATORY-GROUPS { httpMgDefaultGroup }
::= { httpMgCompliances 1 }
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httpMgDefaultGroup OBJECT-GROUP
OBJECTS { httpMgDefaultURL, httpMgSNMPEnabled }
STATUS current
DESCRIPTION
"The objects providing information applicable to all
http manageable systems"
::= { httpMgGroups 1 }
END
5. SNMP over HTTP
A HTTP server acting in a management role may provide a variety of
content including HTML, graphics, executable code and binary data.
SNMP Protocol Data Units (PDUs) may be transmitted over HTTP in the
following manner as "application/octet-stream" Content-Type data.
As described in the "HTTP Manageable MIB", the "httpMgSNMPEnabled"
MIB object determines if a SNMP / HTTP agent can support SNMP over
HTTP. If this object is set true, SNMP / HTTP tunneling is
supported. The URL used for this capability is the one defined
in the "httpMgDefaultURL" MIB object. This URL will include port
280 reference when appropriate.
Once a HTTP server has been determined to support SNMP over HTTP,
SNMP requests may be made by encapsulating the encoded PDU in a
HTTP request entity body [1].
Web Based Managed Entity
------------------------------------------
| ----------- ---------- |
| | SNMP | SNMP | HTTP | |
| | Agent |<============>| Server | |
| | | | | |
| | | | | |
| --|-----|--- --|----|-- |
-----|-----|--------------------|----|----
Port 161 | | | | Port 80
--<--->-- | | -<----->-- SNMP/HTTP
Port 162 | | Port 280
------>-------- ------<----->-- SNMP/HTTP
The Backus Naur Form (BNF) for a HTTP 1.0 compliant request is as
follows. Please refer to the HTTP 1.0 specification for more
details on HTTP [1].
Full-Request = Request-Line
*( General-Header
| Request-Header
| Entity-Header ) CRLF
[ Entity-Body ]
Entity-Header fields define optional metainformation about the
Entity-Body or, if no body is present, about the resource
identified by the request. For SNMP / HTTP tunneling, the Entity-
Header and Entity-Body fields are utilized.
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Entity-Header = Allow
| Content-Encoding
| Content-Length
| Content-Type
| Expires
| Last-Modified
| extension-header
For the transfer of a SNMP encoded PDU, the "Content-Type" and
"Content-Length" specifiers are required. HTTP uses Internet
Media Types for the Content-Type found in the Entity-Header
field [4].The Content-Type Entity-Header field indicates the
media type of the Entity-Body. The PDU is treated as
media-type "application/octet-stream". The "Content-Length"
value is the length, in octets, of the encoded PDU.
SNMP over HTTP is defined for SNMP get, set, get-next, get-bulk
and inform operations. When making making SNMP requests over
HTTP, the PDU type is encoded within the request PDU. The HTTP
POST operation is utilized for all SNMP operations. The POST
operation allows sending the enclosed Entity-Body to the
specified URL. Applications such as WWW browsers do not cache
HTTP POST requests. This allows all transactions to go on the
wire.
To differentiate a SNMP / HTTP management request from other
HTTP management requests, a standard URI, "snmp-request" is
utilized. This URI is used for all SNMP get, set, next, bulk
and inform PDUs since the PDU type is encoded within the PDU.
Example of SNMP get over HTTP. Assume we have an encoded SNMP get
PDU of 275 bytes in length.
POST /snmp-request HTTP/1.0
Content-Type: application/octet-stream
Content-Length: 275
[ 275 bytes of PDU ]
Returned will be the HTTP response with the PDU response found in
the Entity-Body.
HTTP/1.0 20 OK
Content-Type: application/octet-stream
Content-Length: 275
[ 275 bytes of PDU]
SNMP get-next, set, get-bulk and inform SNMP operations work in a
similar manner.
It should be mentioned that SNMP over HTTP is accomplished without
the introduction of yet-another-management protocol. Instead, HTTP
can be used to transfer information between a managed entity and WWW
browser or network management application. In doing so, HTTP has the
potential of offering many benefits including secure transfer of
information.
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6. Conclusion
The utilization of web based system and network management offers
much potential. Without proper standardization, this new form of
management will not provide an open systems solution for the
management of heterogenous multi-vendor environments. In intent
of this Internet Draft is to offer areas of standardization for
web based management and in doing so seek a single unified
approach.
7. References:
[1] T. Berners-Lee, R. Fielding,H. Frystyk, "Hypertext Transfer Protocol
HTTP/1.0" RFC 1945, MIT/LCS, UC Irvine, May 1996.
[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] Hazewinkel, H., E. van Hengstum, A. Pras, "Definitions of Managed
Objects for HTTP", draft-hazewinkel-httpmib-00.txt, University of
Twente, April 1996
[4] J. Postel. "Assigned Numbers", STD 2, RFC 1700, USC/ISI,
October 1994.
8. Acknowledgments
This document was produced as a result of the Hewlett-Packard
Web-based Management Working Group and the effort of its
participants.
The authors gratefully acknowledges the work and comments of
the following individuals:
Steve Gase,GASE_STEVE/HP-Boise_unixgw1@hpflash
Hewlett-Packard Company
Jean-Jacques Moreau, jjm@hplb.hpl.hp.com
Hewlett-Packard Company
Jeff Morgan, morgan@hpl.hp.com
Hewlett-Packard Company
Brian O'Keefe, bok@nsmdserv.cnd.hp.com
Hewlett-Packard Company
Jitendra Singh,SINGH_JITENDRA/hp-santaclara_om3@hpflash
Hewlett-Packard Company
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