PPP IPCP MIB: The Definitions of Managed Objects for the IP Network Control Protocol of the Point-to-Point Protocol
The SNMP objects a network manager can read and set to watch and control IP running over a PPP link.
Kastenholz, F., "The Definitions of Managed Objects for the IP Network Control Protocol of the Point-to-Point Protocol", RFC 1473, DOI 10.17487/RFC1473, June 1993, <https://www.rfc-editor.org/info/rfc1473>.
@misc{rfc1473,
series = {Request for Comments},
number = 1473,
howpublished = {RFC 1473},
publisher = {RFC Editor},
doi = {10.17487/RFC1473},
url = {https://www.rfc-editor.org/info/rfc1473},
author = {F. Kastenholz},
title = {{The Definitions of Managed Objects for the IP Network Control Protocol of the Point-to-Point Protocol}},
pagetotal = 10,
year = 1993,
month = jun,
} RFC text
Contents
Network Working Group F. Kastenholz
Request for Comments: 1473 FTP Software, Inc.
June 1993
The Definitions of Managed Objects for
the IP Network Control Protocol of
the Point-to-Point Protocol
Status of this Memo
This RFC specifies an IAB standards track protocol for the Internet
community, and requests discussion and suggestions for improvements.
Please refer to the current edition of the "IAB Official Protocol
Standards" for the standardization state and status of this protocol.
Distribution of this memo is unlimited.
Abstract
This memo defines a portion of the Management Information Base (MIB)
for use with network management protocols in TCP/IP-based internets.
In particular, it describes managed objects used for managing the IP
Network Control Protocol on subnetwork interfaces using the family of
Point-to-Point Protocols [8, 9, 10, 11, & 12].
Table of Contents
1. The Network Management Framework ...................... 1
2. Objects ............................................... 2
2.1 Format of Definitions ................................ 2
3. Overview .............................................. 2
3.1 Object Selection Criteria ............................ 2
3.2 Structure of the PPP ................................. 2
3.3 MIB Groups ........................................... 3
4. Definitions ........................................... 4
5. Acknowledgements ...................................... 8
6. Security Considerations ............................... 8
7. References ............................................ 8
8. Author's Address ...................................... 9
1. The Network Management Framework
The Internet-standard Network Management Framework consists of three
components. They are:
STD 16/RFC 1155 which defines the SMI, the mechanisms used for
describing and naming objects for the purpose of management. STD
16/RFC 1212 defines a more concise description mechanism, which is
wholly consistent with the SMI.
STD 17/RFC 1213 which defines MIB-II, the core set of managed
objects for the Internet suite of protocols.
STD 15/RFC 1157 which defines the SNMP, the protocol used for
network access to managed objects.
The Framework permits new objects to be defined for the purpose of
experimentation and evaluation.
2. Objects
Managed objects are accessed via a virtual information store, termed
the Management Information Base or MIB. Objects in the MIB are
defined using the subset of Abstract Syntax Notation One (ASN.1) [3]
defined in the SMI. In particular, each object type is named by an
OBJECT IDENTIFIER, an administratively assigned name. The object
type together with an object instance serves to uniquely identify a
specific instantiation of the object. For human convenience, we
often use a textual string, termed the descriptor, to refer to the
object type.
2.1. Format of Definitions
Section 4 contains the specification of all object types contained in
this MIB module. The object types are defined using the conventions
defined in the SMI, as amended by the extensions specified in [5,6].
3. Overview
3.1. Object Selection Criteria
To be consistent with IAB directives and good engineering practice,
an explicit attempt was made to keep this MIB as simple as possible.
This was accomplished by applying the following criteria to objects
proposed for inclusion:
(1) Require objects be essential for either fault or
configuration management. In particular, objects for
which the sole purpose was to debug implementations were
explicitly excluded from the MIB.
(2) Consider evidence of current use and/or utility.
(3) Limit the total number of objects.
(4) Exclude objects which are simply derivable from others in
this or other MIBs.
3.2. Structure of the PPP
This section describes the basic model of PPP used in developing the
PPP MIB. This information should be useful to the implementor in
understanding some of the basic design decisions of the MIB.
The PPP is not one single protocol but a large family of protocols.
Each of these is, in itself, a fairly complex protocol. The PPP
protocols may be divided into three rough categories:
Control Protocols
The Control Protocols are used to control the operation of the
PPP. The Control Protocols include the Link Control Protocol
(LCP), the Password Authentication Protocol (PAP), the Link
Quality Report (LQR), and the Challenge Handshake Authentication
Protocol (CHAP).
Network Protocols
The Network Protocols are used to move the network traffic over
the PPP interface. A Network Protocol encapsulates the datagrams
of a specific higher-layer protocol that is using the PPP as a
data link. Note that within the context of PPP, the term "Network
Protocol" does not imply an OSI Layer-3 protocol; for instance,
there is a Bridging network protocol.
Network Control Protocols (NCPs)
The NCPs are used to control the operation of the Network
Protocols. Generally, each Network Protocol has its own Network
Control Protocol; thus, the IP Network Protocol has its IP Control
Protocol, the Bridging Network Protocol has its Bridging Network
Control Protocol and so on.
This document specifies the objects used in managing one of these
protocols, namely the IP Network Control Protocol.
3.3. MIB Groups
Objects in this MIB are arranged into several MIB groups. Each group
is organized as a set of related objects.
These groups are the basic unit of conformance: if the semantics of a
group are applicable to an implementation then all objects in the
group must be implemented.
The PPP MIB is organized into several MIB Groups, including, but not
limited to, the following groups:
o The PPP Link Group
o The PPP LQR Group
o The PPP LQR Extensions Group
o The PPP IP Group
o The PPP Bridge Group
o The PPP Security Group
This document specifies the following group:
The PPP IP Group
The PPP IP Group contains configuration, status, and control
variables that apply to the operation of IP over PPP.
Implementation of this group is mandatory for all implementations
of PPP that support IP over PPP.
4. Definitions
PPP-IP-NCP-MIB DEFINITIONS ::= BEGIN
IMPORTS
Counter
FROM RFC1155-SMI
ifIndex
FROM RFC1213-MIB
OBJECT-TYPE
FROM RFC-1212
ppp
FROM PPP-LCP-MIB;
-- The PPP IP Group.
-- Implementation of this group is mandatory for all
-- PPP implementations that support operating IP over PPP.
pppIp OBJECT IDENTIFIER ::= { ppp 3 }
pppIpTable OBJECT-TYPE
SYNTAX SEQUENCE OF PppIpEntry
ACCESS not-accessible
STATUS mandatory
DESCRIPTION
"Table containing the IP parameters and
statistics for the local PPP entity."
::= { pppIp 1 }
pppIpEntry OBJECT-TYPE
SYNTAX PppIpEntry
ACCESS not-accessible
STATUS mandatory
DESCRIPTION
"IPCP status information for a particular PPP
link."
INDEX { ifIndex }
::= { pppIpTable 1 }
PppIpEntry ::= SEQUENCE {
pppIpOperStatus
INTEGER,
pppIpLocalToRemoteCompressionProtocol
INTEGER,
pppIpRemoteToLocalCompressionProtocol
INTEGER,
pppIpRemoteMaxSlotId
INTEGER,
pppIpLocalMaxSlotId
INTEGER
}
-- The following object reflect the values of the option
-- parameters used in the PPP IP Control Protocol
-- pppIpLocalToRemoteCompressionProtocol
-- pppIpRemoteToLocalCompressionProtocol
-- pppIpRemoteMaxSlotId
-- pppIpLocalMaxSlotId
-- These values are not available until after the PPP Option
-- negotiation has completed, which is indicated by the link
-- reaching the open state (i.e., pppIpOperStatus is set to
-- opened).
--
-- Therefore, when pppIpOperStatus is not opened
-- the contents of these objects is undefined. The value
-- returned when accessing the objects is an implementation
-- dependent issue.
pppIpOperStatus OBJECT-TYPE
SYNTAX INTEGER {opened(1), not-opened(2)}
ACCESS read-only
STATUS mandatory
DESCRIPTION
"The operational status of the IP network
protocol. If the value of this object is up
then the finite state machine for the IP
network protocol has reached the Opened state."
::= { pppIpEntry 1 }
pppIpLocalToRemoteCompressionProtocol OBJECT-TYPE
SYNTAX INTEGER {
none(1),
vj-tcp(2)
}
ACCESS read-only
STATUS mandatory
DESCRIPTION
"The IP compression protocol that the local
PPP-IP entity uses when sending packets to the
remote PPP-IP entity. The value of this object
is meaningful only when the link has reached
the open state (pppIpOperStatus is opened)."
::= { pppIpEntry 2 }
pppIpRemoteToLocalCompressionProtocol OBJECT-TYPE
SYNTAX INTEGER {
none(1),
vj-tcp(2)
}
ACCESS read-only
STATUS mandatory
DESCRIPTION
"The IP compression protocol that the remote
PPP-IP entity uses when sending packets to the
local PPP-IP entity. The value of this object
is meaningful only when the link has reached
the open state (pppIpOperStatus is opened)."
::= { pppIpEntry 3 }
pppIpRemoteMaxSlotId OBJECT-TYPE
SYNTAX INTEGER(0..255)
ACCESS read-only
STATUS mandatory
DESCRIPTION
"The Max-Slot-Id parameter that the remote node
has advertised and that is in use on the link.
If vj-tcp header compression is not in use on
the link then the value of this object shall be
0. The value of this object is meaningful only
when the link has reached the open state
(pppIpOperStatus is opened)."
::= { pppIpEntry 4 }
pppIpLocalMaxSlotId OBJECT-TYPE
SYNTAX INTEGER(0..255)
ACCESS read-only
STATUS mandatory
DESCRIPTION
"The Max-Slot-Id parameter that the local node
has advertised and that is in use on the link.
If vj-tcp header compression is not in use on
the link then the value of this object shall be
0. The value of this object is meaningful only
when the link has reached the open state
(pppIpOperStatus is opened)."
::= { pppIpEntry 5 }
--
-- The PPP IP Configuration table.
-- This is a separate table in order to facilitate
-- placing these variables in a separate MIB view.
--
pppIpConfigTable OBJECT-TYPE
SYNTAX SEQUENCE OF PppIpConfigEntry
ACCESS not-accessible
STATUS mandatory
DESCRIPTION
"Table containing configuration variables for
the IPCP for the local PPP entity."
::= { pppIp 2 }
pppIpConfigEntry OBJECT-TYPE
SYNTAX PppIpConfigEntry
ACCESS not-accessible
STATUS mandatory
DESCRIPTION
"IPCP information for a particular PPP link."
INDEX { ifIndex }
::= { pppIpConfigTable 1 }
PppIpConfigEntry ::= SEQUENCE {
pppIpConfigAdminStatus
INTEGER,
pppIpConfigCompression
INTEGER
}
pppIpConfigAdminStatus OBJECT-TYPE
SYNTAX INTEGER {open(1), close(2)}
ACCESS read-write
STATUS mandatory
DESCRIPTION
"The immediate desired status of the IP network
protocol. Setting this object to open will
inject an administrative open event into the IP
network protocol's finite state machine.
Setting this object to close will inject an
administrative close event into the IP network
protocol's finite state machine."
::= { pppIpConfigEntry 1 }
pppIpConfigCompression OBJECT-TYPE
SYNTAX INTEGER {
none(1),
vj-tcp(2)
}
ACCESS read-write
STATUS mandatory
DESCRIPTION
"If none(1) then the local node will not
attempt to negotiate any IP Compression option.
Otherwise, the local node will attempt to
negotiate compression mode indicated by the
enumerated value. Changing this object will
have effect when the link is next restarted."
REFERENCE
"Section 4.0, Van Jacobson TCP/IP Header
Compression of RFC1332."
DEFVAL { none }
::= { pppIpConfigEntry 2 }
END
5. Acknowledgements
This document was produced by the PPP working group. In addition to
the working group, the author wishes to thank the following
individuals for their comments and contributions:
Bill Simpson -- Daydreamer
Glenn McGregor -- Merit
Jesse Walker -- DEC
Chris Gunner -- DEC
6. Security Considerations
The PPP MIB affords the network operator the ability to configure and
control the PPP links of a particular system, including the PPP
authentication protocols. This represents a security risk.
These risks are addressed in the following manners:
(1) All variables which represent a significant security risk
are placed in separate, optional, MIB Groups. As the MIB
Group is the quantum of implementation within a MIB, the
implementor of the MIB may elect not to implement these
groups.
(2) The implementor may choose to implement the variables
which present a security risk so that they may not be
written, i.e., the variables are READ-ONLY. This method
still presents a security risk, and is not recommended,
in that the variables, specifically the PPP
Authentication Protocols' variables, may be easily read.
(3) Using SNMPv2, the operator can place the variables into
MIB views which are protected in that the parties which
have access to those MIB views use authentication and
privacy protocols, or the operator may elect to make
these views not accessible to any party. In order to
facilitate this placement, all security-related variables
are placed in separate MIB Tables. This eases the
identification of the necessary MIB View Subtree.
7. References
[1] Rose M., and K. McCloghrie, "Structure and Identification of
Management Information for TCP/IP-based internets", STD 16, RFC
1155, Performance Systems International, Hughes LAN Systems, May
1990.
[2] McCloghrie K., and M. Rose, Editors, "Management Information Base
for Network Management of TCP/IP-based internets", STD 17, RFC
1213, Performance Systems International, March 1991.
[3] Information processing systems - Open Systems Interconnection -
Specification of Abstract Syntax Notation One (ASN.1),
International Organization for Standardization, International
Standard 8824, December 1987.
[4] Information processing systems - Open Systems Interconnection -
Specification of Basic Encoding Rules for Abstract Notation One
(ASN.1), International Organization for Standardization,
International Standard 8825, December 1987.
[5] Rose, M., and K. McCloghrie, Editors, "Concise MIB Definitions",
STD 16, RFC 1212, Performance Systems International, Hughes LAN
Systems, March 1991.
[6] Rose, M., Editor, "A Convention for Defining Traps for use with
the SNMP", RFC 1215, Performance Systems International, March
1991.
[7] McCloghrie, K., "Extensions to the Generic-Interface MIB", RFC
1229, Hughes LAN Systems, Inc., May 1991.
[8] Simpson, W., "The Point-to-Point Protocol for the Transmission of
Multi-protocol Datagrams over Point-to-Point Links, RFC 1331,
Daydreamer, May 1992.
[9] McGregor, G., "The PPP Internet Protocol Control Protocol", RFC
1332, Merit, May 1992.
[10] Baker, F., "Point-to-Point Protocol Extensions for Bridging", RFC
1220, ACC, April 1991.
[11] Lloyd, B., and W. Simpson, "PPP Authentication Protocols", RFC
1334, L&A, Daydreamer, October 1992.
[12] Simpson, W., "PPP Link Quality Monitoring", RFC 1333, Daydreamer,
May 1992.
8. Author's Address
Frank Kastenholz
FTP Software, Inc.
2 High Street
North Andover, Mass 01845 USA
Phone: (508) 685-4000
EMail: kasten@ftp.com
AI ELI5
On this page
§1The Management Framework It Plugs Into
The Internet-standard Network Management Framework has three components. SMI (RFC 1155, with the more concise description style in RFC 1212) describes how objects are named and described. MIB-II (RFC 1213) is the core set of managed objects. SNMP (RFC 1157) is the protocol used to reach those objects over the network.
Managed objects live in a virtual information store called the Management Information Base (MIB). Each object type is named by an OBJECT IDENTIFIER and is written in the subset of ASN.1 that the SMI allows. This memo adds new objects to that store.
Think of a big instruction panel for network gear. There are rules for how each dial is named, a basic set of dials every device has, and a way to read them from far away. This memo adds some new dials.
§2What PPP Looks Like and What This MIB Covers
The memo explains that PPP is not one protocol but a large family, and splits it into three rough categories. Control Protocols (LCP, PAP, LQR and CHAP) control PPP itself. Network Protocols carry the traffic of a specific higher-layer protocol over the PPP interface. Network Control Protocols (NCPs) control the Network Protocols, usually one NCP for each, so IP has the IP Control Protocol.
This document manages only one of these: the IP Network Control Protocol. The wider PPP MIB is arranged in groups (Link, LQR, LQR Extensions, IP, Bridge and Security), and this memo specifies just the PPP IP Group. A group is the basic unit of conformance: if its semantics apply to an implementation, all objects in it must be implemented. The IP Group is mandatory for every PPP implementation that supports IP over PPP.
PPP is a toolbox with many tools: some run the line, some carry the mail, and some set up each kind of mail. This memo only covers the tool that sets up Internet mail.
§3Keeping the MIB Small
The author kept the MIB deliberately simple, in line with IAB directives and good engineering practice. Four criteria decided which objects got in.
- Objects must be essential for fault or configuration management. Objects whose only purpose is debugging implementations are excluded.
- Evidence of current use or usefulness is considered.
- The total number of objects is limited.
- Objects that can simply be derived from others, in this or other MIBs, are left out.
The authors only added a dial if someone really needed it. No dials just for the repair crew, and no dials that repeat what another dial already shows.
§4The Status Table
The module is called PPP-IP-NCP-MIB. It hangs pppIp under the ppp object imported from PPP-LCP-MIB, and it holds two tables, each with one row per interface, indexed by ifIndex from MIB-II.
The first, pppIpTable, is read-only status for the IP Control Protocol on a link. pppIpOperStatus is opened(1) or not-opened(2), and says whether the IP network protocol's finite state machine has reached the Opened state. Four more objects report what option negotiation produced: pppIpLocalToRemoteCompressionProtocol and pppIpRemoteToLocalCompressionProtocol (each none(1) or vj-tcp(2)) and pppIpRemoteMaxSlotId and pppIpLocalMaxSlotId (each 0 to 255, and 0 when vj-tcp header compression is not in use).
Those four option objects are meaningful only after negotiation finishes, which means pppIpOperStatus is opened. Otherwise their contents are undefined, and what an implementation returns is up to it.
The first table is a set of gauges. One says whether the Internet part of the line is up, and the others say what speed-up tricks the two ends agreed on.
- pppIp { ppp 3 }
- pppIpTable status, read-only
- pppIpOperStatus
- pppIpLocalToRemoteCompressionProtocol
- pppIpRemoteToLocalCompressionProtocol
- pppIpRemoteMaxSlotId
- pppIpLocalMaxSlotId
- pppIpConfigTable configuration, read-write
- pppIpConfigAdminStatus
- pppIpConfigCompression
- pppIpTable status, read-only
§5The Configuration Table
The second table, pppIpConfigTable, is kept separate so that its variables can be placed in a separate MIB view. It has two read-write objects.
pppIpConfigAdminStatus is open(1) or close(2). Setting it to open injects an administrative open event into the IP network protocol's finite state machine, and setting it to close injects an administrative close event.
pppIpConfigCompression is none(1) or vj-tcp(2) and defaults to none. With none, the local node will not try to negotiate any IP compression option. Otherwise it will try to negotiate the chosen mode. A change takes effect when the link is next restarted. The object cites the Van Jacobson TCP/IP header compression section of RFC 1332.
The second table has switches. One switch turns the Internet part of the line on or off. The other asks the two ends to try a speed-up trick the next time the line restarts.
§6Security Considerations
The PPP MIB lets an operator configure and control PPP links, including the authentication protocols, and the memo says this is a security risk. It names three ways to address it.
- Variables with significant risk go into separate, optional MIB groups, so an implementor may choose not to implement them.
- An implementor may make risky variables read-only. This still leaves a risk, because authentication variables may be easily read, so it is not recommended.
- With SNMPv2, the operator can put the variables into MIB views protected by authentication and privacy protocols, or make the views inaccessible to every party. Security-related variables sit in separate tables to make the view subtree easy to identify.
Because these switches can change how the line works, the memo says to lock the risky ones in a cabinet, make them look-only, or let only people with the right key reach them.