Network Working Group C.Partridge
Request For Comment: 1024 BBN/NNSC
G. Trewitt
Stanford
October 1987
HEMS VARIABLE DEFINITIONS
STATUS OF THIS MEMO
This memo assigns instruction codes, defines object formats and
object semantics for use with the High-Level Monitoring and Control
Language, defined in RFC-1023.
This memo is provisional and the definitions are subject to change.
Readers should confirm that they have the most recent version of the
memo.
The authors assume a working knowledge of the ISO data encoding
standard, ASN.1, and a general understanding of the IP protocol
suite.
Distribution of this memo is unlimited.
INTRODUCTION
In other memos [RFC-1021, RFC-1022] the authors have described a
general system for monitoring and controlling network entities; this
system is called the High-Level Entity Management System (HEMS).
This system permits applications to read and write values in remote
entities which support a simple query processor.
In this memo we standardize the language instruction codes, the
objects which can be read or written, and the meanings of any
constants stored in the objects. There are three parts to this
standardization: (1) the assignment of an ASN.1 tag to each value,
(2) the definition of the external representation of the value (e.g.,
INTEGER, OCTETSTRING, etc.), and (3) the definition of the meaning,
or semantics of a value (e.g., what types of packets a particular
packet counter actually tracks).
This definition is provisional, and the authors hope that it will be
expanded and improved as the community becomes more experienced with
HEMS. Readers with suggestions for additional object definitions, or
improved definitions are encouraged to contact the authors.
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MESSAGE FORMATS
All HEMS values are conveyed between applications and entities using
the High-Level Entity Management Protocol (HEMP) specified in RFC-
1022. All values specified in this memo are passed in the data
sections of HEMP messages. For all message types, the data section
is a SEQUENCE of objects. For requests, these objects are operations
and their operands. Replies contain a sequence of objects retrieved
by a request. Events contain an initial event object followed by an
optional number of objects related to the event.
Messages conforming to this memo should set the link field in the
HEMP CommonHeader to 1, to indicate version 1 of HEMS. The
resourceId field should be set to NULL.
CONTROL LANGUAGE INSTRUCTIONS
The HEMS Monitoring and Control Language defines a suite of
operations which the query processor must be able to perform. These
operations and their operands are ASN.1 objects which are passed to
the query processor over a network connection. The operations and
operands are sent in postfix form (the operation follows the
operands). Operands are pushed onto a stack and are processed when
the operation is encountered.
To ensure that operations are easily recognized in the input stream,
they are all encoded in a single application-specific type. This
type is shown below.
When the query processor encounters an Operation object it consults
the value to determine which operation is to be done (e.g., GET).
GENERAL COMMENTS ON OBJECTS STORED IN ENTITIES
The High-Level Monitoring and Control Language requires the object
space to have a tree-shaped type space. Locating a particular object
requires identifying that section of the tree in which the object
resides. (A more detailed explanation of the scheme is given in
RFC-1023).
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This memo defines a universal type space. A subset of this type
space is expected to be an appropriate type space for any entity
(e.g., a gateway or a multi-user host). The type space is divided
into required and optional portions. Implementors should implement
the required portion of the type space plus that part of the optional
type space which is appropriate for their particular entity.
One problem with defining a universal type space is that certain
interesting objects are not universal, but are instead very machine
specific (for example, status registers on specialized hardware). To
allow implementors to retrieve such implementation-specific objects
using the HEMS system, a special APPLICATION type is reserved for
non-standard values.
Putting objects in ASN.1 form implies an ability to map to and from
ASN.1 format. One of the design goals of this system has been to
minimize the amount of ASN.1 compilation required by the query
processor to reduce the expense of processing queries at entities.
(This implies a certain willingness to force the applications
querying entities to be more powerful). We expect that most of the
complex mapping will be done when objects are read; most writable
objects have a simple format (e.g., an INTEGER, or OCTETSTRING). As
a result, we have made a heavy use of the ASN.1 SET type, which
allows values to be presented in any order. Applications which
require particular fields in an object may use the template structure
to specify particular fields to be retrieved, but this still permits
the query processor to return the fields in whatever order is
convenient.
In addition to ease the problems of ASN.1 compilation, query
processors are not required to reduce an INTEGER to the minimum
number of octets as specified in ASN.1. Applications should be
prepared to receive INTEGERs which have leading octets with all zeros
or ones.
More generally, a design goal of HEMS was to try to limit the data
processing done at the entity, and to place the burden of data
reduction on the querying application. As a result, the objects
presented here are typically counters, or values which the entity has
to compute already. Object definitions which require the entity to
do data reduction are not supported, although consideration might be
given to making them optionally available.
Finally, HEMS is required to support access by multiple network
management centers or applications. This constraint has some
important consequences. First, the SET operation cannot be applied
to any Counter, since changing the value of a Counter may impair data
acquisition by other centers. More generally, there are questions
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about competing or clashing SET requests from management centers.
Currently HEMS does not provide any facilities for protecting against
such requests. If such facilities become necessary, the authors
envision the enhancement of the object definitions to incorporate the
idea of "owned" objects.
READING THE OBJECT DEFINITIONS
Most of the rest of this memo is devoted to ennumerating the objects
managed by the query processor. Many of these objects are
dictionaries, objects which reference other objects. Defining
dictionaries requires that we specify the class of objects they
reference.
Most significant objects, such as packet counts, reside at the leaves
of the object data tree. They need to be carefully defined to ensure
that their meaning is consistent across all HEMS implementations.
These values are defined using the following format:
OBJECT: This is the name of the object.
Type: This is the ASN.1 type of the object.
Definition: The meaning of the data the object contains.
Implementations should ensure that their instance of
the object fulfills this definition since an important
feature of HEMS is that objects have consistent meaning
across all machines. It is better not to implement
an object than to abuse its definition.
Notes: An optional section of the definition which is used
to discuss issues not covered in other sections of
this specification.
Object Status: An optional section of the definition which
is used to indicate whether the object is required of all
HEMS implementations, encouraged of HEMS implementations
or simply considered useful. Currently, there are four
levels of status:
Required: The object is felt to provide critical
information and must be included in a fully
conforming HEMS implementation.
Required On Condition: The object is felt to
provide critical information about an optional
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feature of an IP entity (for example, support of
the Transmission Control Protocol). The object
is required if the feature is implemented in the
entity.
Encouraged: The object is felt to provide very
useful management information and implementors
are encouraged to implement it.
Defined: The object may be useful and has been
defined so that all implementations of the object
are consistent.
If the object status is not specified, the object should
be considered required. If the parent dictionary is optional,
then the object should be considered required if the parent
dictionary is supported.
Operations on Object: The definition of how each monitoring
and control operation acts on the object. Many operations
have the same effect on almost all values, so some
default definitions are presented here. In the absence
of an operation specification, implementors should use
the default operations defined here.
BEGIN: The default is for BEGIN to be defined for
dictionaries, and an error if performed on leaf
objects in the tree.
CREATE: The default is that CREATE is undefined.
DELETE: The default is that DELETE is undefined.
END: END is a stack operation and is defined for all objects.
Note that END may fail if there is no object on the
stack.
GET-ATTRIBUTES: The default is that GET-ATTRIBUTES is
defined on the contents of all dictionaries specified
in this memo. The text description attributes
are optional for values defined in this memo, but
are required for implementation-specific objects.
Any descriptions of object listed in this memo should
cite this memo. GET-ATTRIBUTES must be supported on
all entity-specific values. GET-ATTRIBUTES
returns a Attributes object, which is defined in
the well-known types section below.
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GET-ATTRIBUTES-MATCH: The default is that
GET-ATTRIBUTES-MATCH is optionally defined on any
object which supports GET-MATCH, and is an error
otherwise. The rules for attributes returned by
GET-ATTRIBUTES-MATCH are the same as those for
GET-ATTRIBUTES.
GET: The default definition of GET is to emit the operand
specified is a leaf object, and if the operand is a
dictionary, to recursively GET the entire dictionary and
its subdictionaries.
GET-MATCH: Unless otherwise specified, GET-MATCH is not
supported on an object.
GET-RANGE: Unless otherwise specified, GET-RANGE is not
supported on an object.
SET: Unless otherwise specified, SET is not supported on an
object.
SET-MATCH: Unless otherwise specified, SET-MATCH is not
supported on an object.
ATTRIBUTES
HEMS requires that remote applications be able to discover the
meaning of an object by querying the entity in which the object is
stored. This is done through use of the GET-ATTRIBUTES operator,
which causes an Attributes object to be returned to the application.
The Attributes object is described below.
The meanings of the various attributes are given below.
tagASN1: The ASN.1 tag for this object.
This attribute is required.
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valueFormat: The underlying ASN.1 type of the object
(e.g., SEQUENCE, or OCTETSTRING). This attribute
is required.
longDesc: A potentially lengthy text description which
fully defines the object. This attribute is optional
for objects defined in this memo and required for
entity-specific objects.
shortDesc: A short mnemonic string of less than 15 octets
which is suitable for labelling the value on a display.
This attribute is optional.
unitsDesc: A short string used for integer values to
indicate the units in which the value is measured
(e.g. "ms", "sec", "packets", etc). This attribute
is optional.
precision: For Counter objects, the value at which the
Counter will roll-over. Required for all Counter
objects.
properties: A bitstring of boolean properties of the
object. If the bit is on, it has the given property.
This attribute is optional. The bits currently
defined are:
0 -- If true, the difference between two values
of this object is significant. For example,
the changes in a packet count is always
significant, it always conveys information.
In this case, the 0 bit would be set. On the
other hand, the difference between two readings
of a queue length may be meaningless.
IMPLEMENTATION SPECIFIC TYPES
Each vendor or implementation specific value must be contained within
an VendorSpecific object. The format of the VendorSpecific object is
shown below.
Type: VendorSpecific
VendorSpecific ::= [APPLICATION 3] IMPLICIT SET of ANY
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For a detailed discussion of the need for this type, see RFC 1023.
WELL-KNOWN TYPES
There are some generally useful types which are defined across the
system and are considered well-known. These types support abstract
notions that are frequently used in other definitions.
The Error type is returned within reply messages when an error is
countered. The errorCode is a number specifying a general class of
error. The errorOffset is the octet in the query where the error was
discovered. Note that the query starts at the first octet (octet 0)
of the HEMP data section. The errorDescription is a text message
explaining the error. Note that the definition of this section is
the same (except for the start of the offset) as that of the HEMP
protocol error structure and the error codes have been selected to
keep the code spaces distinct. This is intended to ease the
processing of error messages. The defined errorCodes are:
100 -- Any error not listed below.
101 -- System error. The query processor has failed
in some way.
102 -- Format error. An error has been detected in
the input stream.
103 -- Stack error. A stack overflow or underflow has
occurred.
104 -- Instruction error. The instruction is either
unknown, or not supported on the object to which
it has been applied.
105 -- Operand error. The wrong number of operands or
inappropriate operands have been given to an
instruction.
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TYPE: Counter
Counter ::= [APPLICATION 4] IMPLICIT INTEGER
The Counter type is an unsigned integer which is defined to roll-over
to 0 when incremented past a certain value. (The roll-over point may
be found by examining the attributes for the particular counter.)
Counter sizes should be chosen such that the counters will not roll
over more than once every 24 hours.
TYPE: InstructionGroup
InstructionGroup ::= [APPLICATION 5] IMPLICIT SEQUENCE
of ANY
An InstructionGroup is an encapsulated sequence of operands and
operations. It allows applications to encode queries as objects.
A Histogram associates a count, histCount, with a numeric value,
histValue. No meaning is placed on the count or value by this
definition. Each HistEntry may represent a simple map (e.g.,
histCount instances of histValue), or a more complex relationship
(e.g., a count of all values between this histValue and the next
lowest histValue in the Histogram). The meaning of the particular
Histogram is given in the object definition.
A TrafficMatrix measures traffic observed between two IP addresses.
Typically it is used to count packets flowing through a gateway.
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TYPE: IpAddress
IpAddress ::= OCTETSTRING
The 4 octet IP address. If the length of the string is less than 4
then the missing octets are wildcarded. A zero length string is a
default address (e.g., for indicating default routes).
TYPE: Fraction
Fraction ::= INTEGER
A Fraction is an integer representation of a fractional value. It
contains the numerator of a value as expressed over 256. (For
example dividing the Fraction by 256 gives the fractional value.)
TYPE: BootClock
BootClock ::= INTEGER
The time in milliseconds since the machine was last booted or reset.
This value is always defined.
TYPE: localClock
LocalClock ::= INTEGER
The local system clock, measured in milliseconds since 00:00 1
January 1900 UTC. Assumed to be only a local estimate of the time.
The value 0 is reserved for an uninitialized clock (For example, an
uninitialized time-of-day chip.)
TYPE: NetClock
NetClock ::= INTEGER
A network synchronized clock, which is assumed to be synchronized
across some part of a network. The clock value is measured in
milliseconds since 00:00 1 January 1900 UTC. Specific information
about the synchronization protocol is found in the system variable
dictionary. The value 0 is used to indicate an uninitialized clock.
TYPE: TimeStamp
TimeStamp ::= CHOICE {
[0] BootClock
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[1] localClock
[2] NetClock
}
A TimeStamp, which was taken from the boot clock, system clock or the
synchronized clock. In general, a time of day is preferred to the
time since boot, and a synchronized clock is preferred to an
unsynchronized clock. It is more useful to know that an event
occurred at a particular time, than that it happened so many
milliseconds after the machine booted.
OBJECT DEFINITIONS
The Root Dictionary
In HEMS, all data is stored in dictionaries, where a dictionary is
thought to represent a conceptual grouping of values. The top-level
dictionary is the root dictionary. The form of the root dictionary
for is shown below.
The root dictionary is split into seven general dictionaries:
- SystemVariables, which stores general system values such
as the system clock, machine memory and system up/down
status.
- EventControls, which stores all objects necessary to
observe and control the event generating mechanism in
entities which support events.
- interfaces, which contains all information on all
the network interfaces and IP to physical address
maps (ARP tables, X.25 Standard mappings, etc).
- IpNetworkLayer, which contains information about the
workings of the IP layer. This includes information such
as routing tables, general packet counts, and host-traffic
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matrices.
- IpRoutingTable, which contains information on how the
machine routes packets. It proved more useful to segregate
routing information than to keep it stored with the network
layer data.
- IpTransportLayer, which stores information on the transport
protocols that the entity supports.
- IpApplications, which may store information about various
internet applications such as the domain system. This
section is not required of HEMS entities.
The next several sections define the values stored in the five
dictionaries.
The SystemVariables Dictionary
The SystemVariables dictionary stores objects which are not strictly
protocol, network, or application specific. Such objects include
values such as the machine load, clocks and the processor status.
The form of the dictionary is shown below.
The estError is the estimated error in milliseconds. The
refClockType is a value indicating the type of reference
clock consulted for network time (the values are taken
directly from the Network Time Protocol specification,
RFC-958).
Object Status: Required if the referenceClock is a NetClock.
OBJECT: processorLoad
Type: Fraction
Definition: A value, expressed as a Fraction, which indicates
the current processing load on the entity. A value of
256 (= 1.0) is defined to be running at capacity. It
is recognized that this is an imprecise definition since
capacity can be measured in several ways. For example,
a multiprocessor may still have plenty of capacity
even if one processor is running at capacity,
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or it may be at capacity because that processor is the
master processor and handles all context switching.
The idea is for remote applications to be able to get some
sense of the current workload on the entity. Also note
that the time scale of the measurement should be small.
A load measure that averages over the past 10 seconds
is acceptable but a load measure that averages over the
past 10 minutes is not. Implementors should chose some
mapping between system load and this scale such that 256
represents a machine under severe strain. (Note that this
suggests that values greater than 256 may be returned in
rare cases.)
OBJECT: entityState
Type: INTEGER
Definition: An object which indicates the system state. There are
several defined object values. Some values are read-only and
can only be read from the object. Over values are write-only
and will never be read from the object. Over values are
write-only and will never be read from the object.The values
are:
The read-only values are:
(0) -- reserved.
(1) -- running. The entity is up and running.
(2) -- testing. The entity is running some sort of
diagnostics which may affect its network
operation.
The write-only values are:
(0) -- reserved.
(1) -- reset the entity.
(2) -- reboot the entity. This value is assumed to
cause a more aggressive recycling of the system
than reset, though this need not be the case.
(3) -- halt the entity. This value stops the
entity. It assumed to prevent the entity from
operating until it is manually restarted. (I.e.
the halt takes the machine off the network).
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Note: The ability to change an entity's state requires very strong
access controls.
Operations on Object: The defaults except as noted below.
SET: Optionally writes the value into the object.
The message requesting the SET must be authenticated.
SET-MATCH: Optionally writes the value into the object
if the current value is matched.
OBJECT: kernelMemory
Type: OCTETSTRING
Definition: A sequence of octets which represents the image of the
kernel software running on the entity. This facility is
provided to allow remote network debugging.
By kernel software, we mean that software which controls the
operations and access to the hardware. In particular, the kernel
is expected to contain all network software up through the IP
layer.
Implementations which use lightweight processes or segmented
images should consider providing some way to map their internal
representation into a single contiguous stream of octets.
Note: Access control is required to read this object.
Object Status: Useful.
Operations on Object: The defaults except as noted below.
GET-RANGE: Emits the section of memory specified.
GET: Emits all of memory, but note that a GET on the system
dictionary should *not* emit this object.
OBJECT: pktBuffers
Type: INTEGER
Definition: The total number of packet buffers in the entity.
Object Status: Required if the entity has a maximum number of
buffers. Note that most entities do have a limit (even if it
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is for practical purposes, near infinite) and should return
that limit.
OBJECT: pktOctets
Type: INTEGER
Definition: The maximum number of octets that can be buffered in the
entity at any one time.
Object Status: Required if the entity has a maximum number of octets
it can buffer. Note that most entities do have a limit and
should return that limit.
OBJECT: pktBuffersFree
Type: INTEGER
Definition: The number of packet buffers currently available.
Subtracting pktBuffersFree from pktBuffers should give the
number of buffers in use.
Object Status: Required if there is a limit on the number of
buffers.
OBJECT: pktOctetsFree
Type: INTEGER
Definition: The number of octets currently available including those
not used in allocated buffers. Subtracting this value from
pktOctets should give the number of octets in use.
This object can be used to track how well the entity buffers its
data.
Object Status: Required if there is a limit on the number of
octets that can be buffered.
OBJECT: systemID
Type: IA5STRING
Definition: The text identification of the entity. This value
should include the full name of the vendor, the type of system,
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and the version number of the hardware and software running on
the entity.
The EventControls Dictionary
The EventControls dictionary contains objects to control and
monitor the delivery of event messages to operations centers.
The format of this dictionary is shown below.
EventControls ::= [APPLICATION 34] IMPLICIT SET OPTIONAL {
lastEvent [0] IMPLICIT OCTETSTRING OPTIONAL,
eventMessageID [1] IMPLICIT Counter,
eventCenters [2] IMPLICIT SET of IpAddress,
eventList [3] IMPLICIT SET of eventEntry,
}
OBJECT: eventControls
Type: SET
Definition: See above.
Object Status: This object will be required in entities which
support events, after the event definitions have been
properly specified. See discussion of the event formats
at the end of this memo.
A description of the fields in this dictionary are given below.
OBJECT: lastEvent
Type: OCTETSTRING
Definition: The last event message sent.
Object Status: Implementation of this object is encouraged if the
transport protocol used for events is unreliable (e.g., UDP).
OBJECT: eventMessageID
Type: Counter
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Definition: The HEMP MessageId to be used in the next event
message. Equals the number of events sent.
OBJECT: eventCenters
Type: SET of IpAddress
Definition: The list of IP addresses to which events are sent.
This list receives all events. For more selective event
monitoring, centers should list themselves under the
particular events of interest.
Note: If the SET operator is defined then use of some form of
access control is recommended.
Operations on Object: The defaults except as listed below.
CREATE: Adds an address to the list. The new address may
not be a broadcast address (it may be a multicast
address).
DELETE: Deletes an address from the list.
SET-MATCH: Defined on the IP address. Replaces the
address with a new value.
EMIT-MATCH: Defined on the IP address.
OBJECT: eventList
Type: SET of eventEntry
Definition: An array of entries which contain objects which allow
management centers to control how and when events are sent.
(The contents of the eventEntry structure are explained below.)
The eventControls Dictionary: eventList/eventEntry
The eventEntry provides the necessary control objects to manage how
a particular event is sent. The format of the eventEntry is shown
below.
thresholdIncr [4] IMPLICIT INTEGER,
eventExecution [5] IMPLICIT InstructionGroup OPTIONAL,
eventCenters [6] IMPLICIT SET of IpAddress
}
OBJECT: eventEntry
Type: SET
Definition: See Above.
OBJECT: eventID
Type: INTEGER
Definition: The particular event ID.
OBJECT: eventMode
Type: INTEGER
Definition: A control object which determines how and whether this
event is sent. The three modes are:
0 -- unused.
1 -- off. The event is not sent.
2 -- on. The event is sent every time it occurs.
3 -- threshold. The event is sent every time the
event count reaches the threshold.
OBJECT: eventCount
Type: Counter
Definition: The number of times this event has occurred.
OBJECT: threshold
Type: Counter
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Definition: The event threshold. If the eventMode is "threshold"
then a event is sent every time the eventCount equals this
value.
Operations on Object: The defaults except as noted below.
SET: Changes the threshold.
OBJECT: thresholdIncr
Type: INTEGER
Definition: The threshold increment. Every time a event threshold
is reached, the threshold value is incremented by this value
(modulo the precision of the Counter) to find the new
threshold.
Operations on Object: The defaults except as noted below.
SET: Changes the increment.
OBJECT: eventExecution
Type: InstructionGroup
Definition: A query to be executed whenever the event is actually
sent. Any data retrieved by this query is appended to the
event message.
Object Status: Encouraged.
Operations on Object: The defaults except as noted below.
SET: Changes the buffer.
OBJECT: eventCenters
Type: SET
Definition: The IP addresses of the monitoring centers which wish
to listen to this particular event. Note that events should be
sent to both these centers and the global list of event centers.
Operations on Object: The defaults except as noted below.
CREATE: Adds an address to the list of centers.
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DELETE: Deletes an address from the list.
SET-MATCH: Defined on the IP address. Replaces the
entry with a new value.
EMIT-MATCH: Defined on the IP address.
The Interfaces Dictionary
The Interfaces dictionary a list of per-interface objects. Since
one of the fundamental goals of HEMS is to use generic interfaces
across differing hardwares, all hardware interfaces are described by
the same data structure, the InterfaceData.
Interfaces ::= [APPLICATION 35] IMPLICIT SET OF InterfaceData
OBJECT: Interfaces
Type: SET
Definition: see above.
The Interfaces Dictionary: The InterfaceData structure.
The InterfaceData structure contains all information on a particular
interface. The form of the structure is shown below.
upTime [18] IMPLICIT TimeStamp,
broadcast [19] IMPLICIT BITSTRING
multicast [20] IMPLICIT SET of BITSTRING,
addressList [21] IMPLICIT SET OPTIONAL,
}
OBJECT: InterfaceData
Type: SET
Definition: see above.
Operations on Object: The defaults except as noted below.
SET-MATCH: This operation is optionally defined on the
address field of the structure. Only certain fields
in this structure may be changed. The fields which
may be SET are indicated in the descriptions below.
GET-MATCH: Defined to emit information on the interface
which matches the address given.
The fields in the structure are defined below.
OBJECT: addresses
Type: SET of IpAddress
Definition: The IP addresses that the interface accepts. Note that
additional information on multicast addresses may be found in
the IgmpValues dictionary.
OBJECT: mtu
Type: INTEGER
Definition: The maximum transmission unit of the device.
OBJECT: netMask
Type: IpAddress
Definition: The subnet mask, which is an address with all the
network bits set to 1 and all the hosts bits set to 0. Used to
identify subnets.
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OBJECT: pktsIn
Type: Counter
Definition: The total number of packets received on this interface
including those in error.
OBJECT: pktsOut
Type: Counter
Definition: The total number of packets that higher levels have
attempted to send, including those that were not sent.
OBJECT: inputPktsDropped
Type: Counter
Definition: The number of good inbound packets dropped (presumably
to free up buffer space).
OBJECT: outputPktsDropped
Type: Counter
Definition: The number of good outbound packets dropped (presumably
to free up buffer space).
OBJECT: bcastPktsIn
Type: Counter
Definition: The number of broadcast packets received including
those in error.
Object Status: Encouraged on interfaces that support broadcast.
OBJECT: bcastPktsOut
Type: Counter
Definition: The number of broadcast packets that higher levels
attempted to send, including those that were not sent.
Object Status: Encouraged on interfaces that support broadcast.
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OBJECT: mcastPktsIn
Type: Counter
Definition: The number of multicast packets received including
those in error.
Object Status: Encouraged on interfaces that support multicast.
OBJECT: mcastPktsOut
Type: Counter
Definition: The number of multicast packets sent, including those
that were not sent.
Object Status: Encouraged on interfaces that support multicast.
OBJECT: inputErrors
Type: Counter
Definition: The number of inbound packets that could not be
delivered. The number of inbound packets delivered
should equal inputPkts less this value and inputPktsDropped.
OBJECT: outputErrors
Type: Counter
Definition: The number of outbound packets that could not be
transmitted because of errors. The number of outbound
packets placed on the network should equal outputPkts
less this value and outputPktsDropped.
OBJECT: outputQLen
Type: INTEGER
Definition: The length of the output packet queue (in packets).
OBJECT: name
Type: IA5String
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RFC 1024 HEMS Definitions October 1987
Definition: A text string completely identifying the interface.
This string should include the name of the manufacturer, the
product name and the version of the hardware.
OBJECT: status
Type: INTEGER
Definition: The status of the object. The status values are:
0 -- reserved
1 -- testing (the interface is in some test mode)
2 -- down (the interface is down)
3 -- up (the interface is up ready to pass packets)
Note: If set operations are defined, access control is required.
Operations on Object: The defaults except as noted below.
SET: Optionally defined to change the state of the interface.
OBJECT: ifType
Type: INTEGER
Definition: A flag which indicates the type of interface in use. The
currently defined types are:
Definition: Most interfaces maintain tables mapping physical
network address to IP address. An example is an ARP table.
This table stores that map as a series of entries which map
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RFC 1024 HEMS Definitions October 1987
IP addresses to the physical address.
Object Status: Required if the interface has to map IP addresses to
physical addresses.
The IpNetworkLayer Dictionary
The IpNetworkLayer dictionary contains all information about the IP
Layer. The format of the dictionary is shown below.
Definition: A boolean value which is true if the entity gateways
packets.
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RFC 1024 HEMS Definitions October 1987
OBJECT: inputPkts
Type: Counter
Definition: The total number of input packets received including
those in error.
OBJECT: inputErrors
Type: Counter
Definition: The number of input packets discarded due to errors
(unknown protocols, format errors, etc).
OBJECT: inputPktsDropped
Type: Counter
Definition: The number of input packets dropped for lack of buffer
space.
OBJECT: inputQLen
Type: INTEGER
Definition: The number of inbound packets currently waiting to be
processed by the IP layer.
Object Status: Encouraged.
OBJECT: outputPkts
Type: Counter
Definition: The total number of outbound packets including both
those packets presented to the IP layer by higher layers and
packets which are gatewayed.
OBJECT: outputErrors
Type: Counter
Definition: The number of output packets discarded because of
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RFC 1024 HEMS Definitions October 1987
errors (unable to route, format errors, etc).
OBJECT: outputPktsDropped
Type: Counter
Definition: The number of output packets dropped for lack of
buffer space.
OBJECT: outputQLen
Type: INTEGER
Definition: The number of outbound packets waiting to be processed
by the IP layer.
Object Status: Encouraged.
OBJECT: ipID
Type: Counter
Definition: The next IP packet ID identifier to be used. Note
that in some implementations the transport layer may set the
IP identifier, in which case this value is used if the IP
identifier has not been set by the transport layer.
OBJECT: fragCreated
Type: Counter
Definition: The number of IP fragments created at this entity.
(e.g., if an IP is split into three fragments at this entity,
then this counter is incremented by three).
Object Status: Encouraged.
OBJECT: fragRcvd
Type: Counter
Definition: The number of IP fragments received at this entity.
Object Status: Encouraged.
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OBJECT: fragDropped
Type: Counter
Definition: The number of IP fragments discarded at this entity
for whatever reason (timed out, errors, etc).
Object Status: Encouraged.
OBJECT: pktsReassembled
Type: Counter
Definition: The number of IP datagrams that have been reassembled
at this entity.
Object Status: Encouraged
OBJECT: pktsFragmented
Type: Counter
Definition: The number of IP datagrams that have been fragmented
at this entity.
Object Status: Encouraged.
OBJECT: htm
Type: TrafficMatrix
Definition: A host traffic matrix, mapping all traffic switched any
pair of sources and destinations. The count in each trafficEntry
routeDst is expressed in packets. Source routed IP packets
should be logged as being between their source and the
destination (i.e., they should not be treated as destined for
this entity).
Notes: This information may be considered sensitive.
Object Status: Encouraged in gateways.
OBJECT: itm
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RFC 1024 HEMS Definitions October 1987
Type: TrafficMatrix
Definition: An interface traffic matrix showing traffic switched
between interfaces in an entity. The source and destinations
fields are the IP addresses of the interfaces between which
the packet was switched. The count in each trafficEntry is
expressed in packets.
Object Status: Useful.
The IpRoutingTable Dictionary
The IpRoutingTable dictionary contains all routing information.
Note that information about any routing protocols used to maintain
the routing table is found under the entry for the routing protocol.
The format of the routing dictionary is shown below.
The objects contained in the dictionary are described below.
OBJECT: routingProtocols
Type: OCTETSTRING
Definition: A sparse list of the routing protocols used to update
the routing table (e.g., EGP and ICMP). Each octet contains one
of the following values:
0 -- anything not specified below.
1 -- local (non-protocol) information. (E.g.
routing tables can be changed by hand).
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RFC 1024 HEMS Definitions October 1987
2 -- HEMS (was changed/set by a HEMS operation)
3 -- Internet Control Message Protocols, (i.e.
ICMP redirects).
4 -- Exterior Gateway Protocol (EGP).
5 -- Gateway-to-Gateway Protocol (GGP).
6 -- Dissimilar Gateway Protocol (DGP).
7 -- HELO
8 -- RIP
9 -- Proprietary IGP
OBJECT: coreRouter
Type: BOOLEAN
Definition: This value is set to true if this entity is a reference
router for any other router (i.e., if it distributes any of its
routes to other machines).
OBJECT: autoSys
Type: INTEGER
Definition: The autonomous system number of the autonomous system in
which this entity resides.
OBJECT: metricUsed
Type: OCTET
Definition: Classifies the routing metric used in the routing table
entries. The value should be chosen from the list of values for
routingProtocols above, and indicates the metric definition used
(e.g., this entity uses an EGP metric internally).
OBJECT: RoutingEntries
Type: SET of RoutingEntry
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Definition: The set of all routing entries. The RoutingEntry is
defined below.
The IpRoutingTable Dictionary: The RoutingEntry
The RoutingEntry contains all information on a particular route.
The format of the structure is shown below.
Operations on Object: Defaults except as specified below.
CREATE: Adds a new routing entry. It should be confirmed
that the entry is new.
DELETE: Deletes a routing entry.
GET-MATCH: The match operator is defined on the routeDst
field. A match on an IpAddress is defined to be a
search to find the route or routes which would be
used to reach the IpAddress. More than one route
may be applicable, in which case all possible routes
should be returned.
SET-MATCH: Is optionally defined on the object. A SET
on an entire RoutingEntry replaces the entire entry
with a new value. Certain fields (indicated below)
can also be changed using a SET-MATCH.
The match operator is defined on the routeDst and
routeTOS fields. To SET a value, the match must be
exact on the IP address (this is different from the
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RFC 1024 HEMS Definitions October 1987
search definition for GET-MATCH).
Note that support of the operator on an entity
which uses a dynamic routing protocol such as
GGP or EGP will require close coordination with
the routing protocol to ensure consistent data.
(Arguably, this facility should not be supported
on such machines).
The definitions of the fields in the RoutingEntry are given below.
OBJECT: routeMetric
Type: INTEGER
Definition: The routing metric on this route. Note that the type of
metric is defined in the metricUsed field of the IpRoutingTable
dictionary.
OBJECT: routeDst
Type: IpAddress
Definition: The final destination that can be reached via this
route.
OBJECT: nextHop
Type: IpAddress
Definition: The next hop to the final destination.
OBJECT: routeAuthor
Type: IpAddress
Definition: The IP address of the entity from which this route was
*first* received. That is, the first entity which stated that
was reached via nextHop. The default IpAddress should be used
to indicate routes which originated on the entity.
Object Status: Encouraged.
OBJECT: routeProto
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RFC 1024 HEMS Definitions October 1987
Type: Octet
Definition: The routing protocol from which this route was learned.
The value is taken from the list of values for routingProtocols
above.
Object Status: Encouraged.
OBJECT: routeTime
Type: TimeStamp
Definition: When this route was first received.
Object Status: Encouraged.
OBJECT: routeTOS
Type: INTEGER
Definition: The IP Type of Service which this routing entry serves.
Object Status: Required if type of service routing is supported.
OBJECT: valid
Type: BOOLEAN
Definition: Whether the route is active. (Some machines retain
routes which are no longer valid for various reasons.)
The IpTransportLayer Dictionary
The IpTransportLayer Dictionary contains any information which
pertains to transport protocols which use the IP protocol as the
network protocol. For ease of reference, the ASN.1 tag of each
transport protocol's dictionary is the same as the assigned IP
Protocol number. The definition of the IpTransportLayer
dictionary is shown below. Note that dictionaries for many
protocols are not yet defined.
The IpTransportLayer Dictionary: ProtocolsSupported
OBJECT: protocolsSupported
Type: OCTETSTRING
Definition: Sparse list of transport protocols supported. Each
octet in the OCTETSTRING contains the IP protocol number of a
supported protocol. For the purposes of this definition, an
entity supports a protocol if it both contains software to
makes it possible for the protocol to be used in
communications with the entity, AND the entity keeps the
required values (if any) defined in this memo for that protocol.
The IpTransportLayer Dictionary: IcmpValues
The IcmpValues dictionary is a subdictionary of the IpTransportLayer
dictionary which tracks the workings of the Internet Control Message
Protocol, defined in RFC-792. The form of the dictionary is shown
below.
IcmpValues ::= SET {
inputPktCount [0] IMPLICIT Counter,
inputPktErrors [1] IMPLICIT Counter,
inputPktDeliver [2] IMPLICIT Counter,
inputPktTypes [3] IMPLICIT Histogram OPTIONAL,
outputPktCount [4] IMPLICIT Counter,
outputPktErrors [5] IMPLICIT Counter,
outputPktTypes [6] IMPLICIT Histogram OPTIONAL,
icmpTraffic [7] IMPLICIT TrafficMatrix OPTIONAL,
ipID [8] IMPLICIT Counter OPTIONAL
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RFC 1024 HEMS Definitions October 1987
}
OBJECT: IcmpValues
Type: SET
Definition: see above.
The objects in the dictionary are defined below.
OBJECT: inputPktCount
Type: Counter
Definition: The total number of ICMP packets received (including
those in error).
OBJECT: inputPktErrors
Type: Counter
Definition: The number of ICMP packets received which proved to
have errors (bad checksums, bad length etc). Subtracting this
value from the inputPktCount field should give the number of
valid ICMP packets received.
OBJECT: inputPktDeliver
Type: Counter
Definition: The number of valid ICMP packets which were
successfully processed (e.g., delivered to the higher
protocol).
OBJECT: inputPktTypes
Type: Histogram
Definition: A histogram of ICMP messages types and codes received,
not including those messages that proved to contain errors.
The histogram histValue field contains a 16-bit value which is
the the (ICMP type * 256) + ICMP code, and the histCount field
contains the number of valid messages containing this
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RFC 1024 HEMS Definitions October 1987
type/code pair which have been received.
The message type and code values are those defined in RFC-792
(e.g., the Time Exceeded Message with a code of "fragment
reassembly time exceeded" is (11 * 256) + 1 = 2817).
Object Status: Useful.
Operations on Object: The defaults except as listed below:
GET-MATCH: Match is defined on the value of the histValue
field.
OBJECT: outputPktCount
Type: Counter
Definition: The total number of ICMP packets that the entity
attempted to send (including those that failed due to lack of
buffers, a missing route or other transient transmission
problems).
OBJECT: outputPktErrors
Type: Counter
Definition: The number of ICMP packets which the entity could not
send due to transmission problems such as the lack of buffers, a
missing route or other transient transmission problems. This
value is not required to include errors which the ICMP layer
could not reasonably be expected to detect such as damage to the
packet in transit. Subtracting this value from the PktCount
field should give the number of ICMP packets the entity believes
it successfully sent.
OBJECT: outputPktTypes
Type: Histogram
Definition: A histogram of ICMP messages types and codes sent,
including those messages that later failed to be transmitted.
The histogram histValue field contains a 16-bit value which is
the the (ICMP type * 256) + ICMP code, and the histCount field
contains the number of valid messages containing this type/code
pair which have been sent.
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RFC 1024 HEMS Definitions October 1987
The message type and code values are those defined in RFC-792
(e.g., the Time Exceeded Message with a code of "fragment
reassembly time exceeded" is (11 * 256) + 1 = 2817).
Object Status: Useful.
Operations on Object: The defaults except as listed below:
GET-MATCH: Match is defined on the value of the histValue
field.
OBJECT: icmpTraffic
Type: TrafficMatrix
Definition: All ICMP traffic which has originated on this machine.
The source address in the traffic matrix should be the interface
from which the packet was sent. The destination is the address
to which the packet is to finally be delivered (not an
intermediate hop).
Object Status: Useful.
OBJECT: ipID
Type: Counter
Definition: The next IP packet ID identifier to be used by the ICMP
code.
Object Status: Required if the ICMP code generates its own IP
identifiers.
igmpGroups [8] IMPLICIT SET of IgmpGroupEntry,
ipID [9] IMPLICIT Counter OPTIONAL,
}
OBJECT: IgmpValues
Type: SET
Definition: The dictionary of information on the Internet Group
Management Protocol (RFC-988).
Object Status: Required in hosts which support IGMP.
The objects stored in this dictionary are defined below.
OBJECT: conformance
Type: INTEGER
Definition: The level of conformance with RFC-988. The conformance
levels are:
0 -- Level 0. No support for IP multicasting
1 -- Level 1. Support for sending but not receiving
multicast datagrams.
2 -- Level 2. Full support for IP multicasting.
These values are taken directly from RFC-988.
OBJECT: inputPktCount
Type: Counter
Definition: The number of IGMP packets received including those
that proved to be in error.
OBJECT: inputPktErrors
Type: Counter
Definition: The number of IGMP packets received which proved to
be in error. This value subtracted from inputPktCount should
give the number of valid IGMP packets received.
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RFC 1024 HEMS Definitions October 1987
OBJECT: inputPktTypes
Type: Histogram
Definition: A histogram of IGMP messages types and codes sent,
including those messages that later failed to be transmitted.
The histogram histValue field contains a 16-bit value which
is the the (IGMP type * 256) + IGMP code, and the histCount
field contains the number of valid messages containing this
type/code pair which have been sent.
The type and code values are taken from RFC-988.
OBJECT: outputPktCount
Type: Counter
Definition: The total number of IGMP packets that the entity
attempted to send (including those that failed due to lack
of buffers, a missing route or other transient transmission
problems).
OBJECT: outputPktErrors
Type: Counter
Definition: The number of IGMP packets which the entity could not
send due to transmission problems such as the lack of buffers,
a missing route or other transient transmission problems.
This value is not required to include errors which the IGMP
layer could not reasonably be expected to detect such as damage
to the packet in transit. Subtracting this value from the
outputPktCount field should give the number of IGMP packets
the entity believes it successfully sent.
OBJECT: outputPktTypes
Type: Histogram
Definition: A histogram of IGMP messages types and codes sent,
including those messages that later failed to be transmitted.
The histogram histValue field contains a 16-bit value which is
the the (IGMP type * 256) + IGMP code, and the histCount field
contains the number of valid messages containing this type/code
pair which have been sent.
The type and code values are taken from RFC-988.
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RFC 1024 HEMS Definitions October 1987
OBJECT: igmpTraffic
Type: TrafficMatrix
Definition: All IGMP traffic which has originated on this machine.
The source address in the traffic matrix should be the interface
from which the packet was sent. The destination is the address
to which the packet is to finally be delivered (not an
intermediate hop).
Object Status: Useful.
OBJECT: igmpGroups
Type: SET
Definition: The various igmpGroups of which this host is aware.
This is stored as a set of IgmpGroupEntry. The format of an
IgmpGroupEntry is shown below.
The groupAddress is the multicast IP address. The
groupAccessKey is the 8 octet key -- this key may be
confidential and should only be available to authorized querying
entities. The groupAgent field is true if this entity is an
agent for the multicast group.
OBJECT: ipID
Type: Counter
Definition: The next IP packet ID identifier to be used by the IGMP
code.
Object Status: Required if the IGMP code generates its own IP
identifiers.
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RFC 1024 HEMS Definitions October 1987
The IpTransportLayer Dictionary: GgpValues
The definition of the GgpValues dictionary is left for further
study.
The IpTransportLayer Dictionary: TcpValues
The TcpValues dictionary is a subdictionary of the IpTransportLayer
dictionary which tracks the workings of the Transmission Control
Protocol, defined in RFC-793. The definitions of several objects in
this dictionary refer to definitions in RFC-793. The form of the
dictionary is shown below.
TcpValues ::= SET {
[0] IMPLICIT TcpParam
[1] IMPLICIT TcpStats OPTIONAL,
tcpConnData [2] IMPLICIT SET of TcpConn,
}
OBJECT: TcpValues
Type: IMPLICIT SET
Definition: see above.
Object Status: Required if the entity supports TCP.
The objects in the dictionary are defined in the next few sections.
The IpTransportLayer Dictionary: TcpValues/TcpParam
The TcpParam dictionary contains information about certain
parameters such as round-trip timer estimation constants which are
managed on a per-machine basis. The form of the dictionary is shown
below.
The definition of the objects in the tcpParam dictionary are given
below.
OBJECT: tcpRtoA
Type: IA5String
Definition: The TCP retransmission timeout algorithm used. The
algorithm is expressed as one or more equations to generate
a target value, "RTO[N]", which is the retransmission timeout
for packet "N". Expressions should use well understood
symbols such as * for multiplication and / for division, and
parentheses to indicate precedence. Variables should begin
with an upper case character. Multiple equations should be
separated by semi-colons. Comments should be in braces (i.e.,
{}). Constants should begin with a lower case character. In
addition to "RTO[N]" the symbol "S[N]" is defined to mean the
round-trip sample for packet N. Using this syntax, the
algorithm in RFC-793 would be expressed as:
Note: The syntax probably needs to be refined so that it can be
parsed and interpreted by a program. This is left for future
study.
OBJECT: tcpRtoParam
Type: SET of RtoParam
Definition: The list of the values of the constants used by the
retransmission timeout algorithm. The format of the RtoParam
structure is shown below.
RtoParam ::= SEQUENCE {
name IA5String,
value Fraction
}
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RFC 1024 HEMS Definitions October 1987
The name is the name of the constant as expressed in the
tcpRtoA (e.g., "beta").
OBJECT: ipID
Type: Counter
Definition: The next IP packet ID identifier to be used by the TCP
code.
Object Status: Required if the TCP code generates its own IP
identifiers.
OBJECT: tcpRtoMin
Type: INTEGER
Definition: The minimum value the TCP implementation permits for
the retransmission timeout (RTO), measured in milliseconds.
Note: If the SET operation is optionally defined, access control
must be exercised.
Object Status: Required if the implementation uses the suggested
algorithm in RFC-793 or if the implementation sets any limits
on the minimum RTO.
Operations on Object: The defaults except as listed below:
SET: Optionally defined to change the value. Implementations
should confirm that the new value is less than tcpRtoMax.
OBJECT: tcpRtoMax
Type: INTEGER
Definition: The maximum value the TCP implementation permits for
the retransmission timeout (RTO), measured in milliseconds.
Note: If the SET operation is optionally defined, access control
must be exercised.
Object Status: Required if the implementation uses the suggested
algorithm in RFC-793 or if the implementation sets any limits
on the maximum RTO.
Operations on Object: The defaults except as listed below:
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RFC 1024 HEMS Definitions October 1987
SET: Optionally defined to change the value. Implementations
should confirm that the new value is greater than tcpRtoMax,
and that the value is large (i.e., several seconds).
OBJECT: tcpMaxSegSiz
Type: INTEGER
Definition: The maximum segment size used by this implementation.
Object Status: Required if the entity sets an upper limit on the
MTU. (Some implementations have no constraints, but chose an
MTU from external constraints such as the maximum MTU of the
network interface in use.)
OBJECT: tcpMaxConn
Type: INTEGER
Definition: An optional value, which must be present if the entity
has a limit on the total number of TCP connections it can support.
Object Status: Required if the entity sets limits.
Note: If the SET operation is defined, access control must be
exercised.
Operations on Object: The defaults except as listed below:
SET: Optionally defined to change the value. If the
new value is less than the number of currently
open connections, implementations are *not* required
to close existing connections, but may not open
any additional ones.
OBJECT: tcpMaxWindow
Type: INTEGER
Definition: An optional value, which must be present if the entity
places a fixed upper limit on the size of any connection's TCP
window (i.e., if the maximum window size is not per connection
configurable).
Object Status: Required if the entity sets limits.
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RFC 1024 HEMS Definitions October 1987
Note: If the SET operation is defined, access control must be
exercised.
Operations on Object: The defaults except as listed below:
SET: Optionally defined to change the value. The new
value must be at least the size of one maximum
TCP segment.
The IpTransportLayer Dictionary: TcpValues/TcpStats
The TcpStats dictionary stores general information about the
workings of the TCP layer. The form of the dictionary is shown
below.
The definition of the fields in the dictionary are given below.
OBJECT: connAttempts
Type: Counter
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RFC 1024 HEMS Definitions October 1987
Definition: The number of connection attempts that have been made
from this host. This includes pending attempts.
Object Status: Encouraged.
OBJECT: connOpened
Type: Counter
Definition: The number of connection attempts from this host which
successfully generated an open connection. This includes
currently open connections.
Object Status: Encouraged.
OBJECT: connAccepted
Type: Counter
Definition: The number of connections accepted by listening peers
on this entity. This includes currently open connections.
Object Status: Encouraged.
OBJECT: connClosed
Type: Counter
Definition: The number of connections which were properly closed.
Object Status: Encouraged.
OBJECT: connAborted
Type: Counter
Definition: The number of connections which were aborted. Note
that if implementations trace how the connection was aborted,
they are encouraged to use the connAbortedInfo histogram.
Object Status: Encouraged.
OBJECT: connAbortedInfo
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RFC 1024 HEMS Definitions October 1987
Type: Histogram
Definition: The number of connections which were aborted by type of
abort. The histValue is one of the codes listed below. The
histCount is the number of connections aborted for this reason.
The histValues codes are:
0 -- an abort condition not specified below
1 -- remote abort
2 -- local application abort
3 -- local protocol level abort
Object Status: Useful
OBJECT: octetsIn
Type: Counter
Definition: The total number of TCP octets (not including
duplicates) received at this entity.
Object Status: Required if TcpStats is implemented.
OBJECT: octetsOut
Type: Counter
Definition: The total number of TCP octets (not including
retransmissions) sent from this entity.
Object Status: Required if TcpStats is implemented.
OBJECT: octetsInDup
Type: Counter
Definition: The total number of TCP octets received which were
duplicates.
Object Status: Required if TcpStats is implemented.
OBJECT: octetsReTrans
Type: Counter
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RFC 1024 HEMS Definitions October 1987
Definition: The total number of TCP octets which have been
retransmitted.
Object Status: Required if TcpStats is implemented.
OBJECT: inputPkts
Type: Counter
Definition: The total number of valid packets received, including
those on current connections.
Object Status: Useful.
OBJECT: retransPkts
Type: Counter
Definition: The total number of packets retransmitted.
Object Status: Useful.
OBJECT: outputPkts
Type: Counter
Definition: The total number of packets sent.
Object Status: Useful.
OBJECT: dupPkts
Type: Counter
Definition: The number of packets received which contained only
data already received.
Object Status: Useful.
Partridge & Trewitt [Page 50]
RFC 1024 HEMS Definitions October 1987
The IpTransportLayer Dictionary: TcpValues/TcpConn
The tcpConnData field in the TcpValues dictionary is a set of
TcpConn, where each TcpConn contains information on a particular TCP
connection. The definition of TcpConn is shown below.
The set of TCP connections can be searched in a number of ways based
on the local and foreign addresses (including the port number).
Individual values of a connection cannot be retrieved without a
search.
OBJECT: TcpConn
Type: SET
Definition: The per TCP connection data.
Operations on Object: The defaults except as listed below:
GET-MATCH: Defined on any combination of values of
localAddress, localPort, foreignAddress and
foreignPort. Returns all connections which match
the template. (For example, GET-MATCH on a
particular foreignAddress returns all connections
to that address.)
Partridge & Trewitt [Page 51]
RFC 1024 HEMS Definitions October 1987
The definitions of the fields of the tcpConn structure are given
below.
OBJECT: localPort
Type: INTEGER
Definition: The local port number of this connection.
Operations on Object: Defaults. Note that MATCH operators may be
applied to this object to locate information on a particular TCP
connection.
OBJECT: localAddress
Type: IpAddress
Definition: The local IP address of this connection. May be the
default IP address defined above. This value may not be valid
in certain states.
Operations on Object: Defaults. Note that MATCH operators may be
applied to this object to locate information on a particular
TCP connection.
OBJECT: foreignPort
Type: INTEGER
Definition: The foreign port number of this connection. This value
may be meaningless if the local peer is in certain states (e.g.,
LISTEN).
Operations on Object: Defaults. Note that MATCH operators may be
applied to this object to locate information on a particular TCP
connection.
OBJECT: foreignAddress
Type: IpAddress
Definition: The foreign IP address of this connection. This value
may be meaningless if the local peer is in certain states (e.g.,
LISTEN).
Operations on Object: Defaults. Note that MATCH operators may be
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RFC 1024 HEMS Definitions October 1987
applied to this object to locate information on a particular
TCP connection.
OBJECT: state
Type: INTEGER
Definition: The current state of the local peer. The values
corresponding to the different states are: close(0), listen(1),
syn-sent(2), syn-received(3), established(4), close-wait(5),
fin-wait-1(6), closing(7), last-ack(8), fin-wait-2(9),
time-wait(10). Implementations must map internal
representations of the state into these values.
OBJECT: snduna
Type: INTEGER
Definition: The SND.UNA value as defined in RFC-793.
OBJECT: sndnxt
Type: INTEGER
Definition: The SND.NXT value as defined in RFC-793.
OBJECT: sndwnd
Type: INTEGER
Definition: The SND.WND value as defined in RFC-793.
OBJECT: congwnd
Type: INTEGER
Definition: The congestion window. This value is less than or
equal to sndwnd. If less than sndwnd, then congestion
control is in effect and congwnd is the reduced send window
size in use.
OBJECT: rcvnxt
Type: INTEGER
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Definition: The RCV.NXT value as defined in RFC-793.
OBJECT: rcvwnd
Type: INTEGER
Definition: The RCV.WND value as defined in RFC-793.
OBJECT: srtt
Type: INTEGER
Definition: The smoothed round-trip time in milliseconds.
Object Status: Required if the implementation maintains a smoothed
round-trip time.
OBJECT: lastrtt
Type: INTEGER
Definition: The last round-trip time sample taken in milliseconds.
Object Status: Encouraged.
OBJECT: maxSegSize
Type: INTEGER
Definition: The maximum segment size that can be used on this
connection.
OBJECT: octetsSent
Type: Counter
Definition: The total number of octets transmitted since the
connection was opened, not including retransmissions. Can
alternatively be thought of as the current length of the
stream.
Object Status: Encouraged.
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OBJECT: octetsRXmit
Type: Counter
Definition: The total number of octets retransmitted since the
connection was opened. This plus octetsSent should give the
total number of octets sent.
Object Status: Encouraged.
OBJECT: octetsRcvd
Type: Counter
Definition: The number of octets received since the connection was
opened, not including duplicates received. The receiver's
version of octetsSent.
Object Status: Encouraged.
OBJECT: octetDups
Type: Counter
Definition: The total number of octets received since the
connection was opened which were redundant (i.e., they had been
previously received).
Object Status: Encouraged.
OBJECT: octetPastWin
Type: Counter
Definition: The number of segments which contained data beyond
the upper edge of the receive window.
Object Status: Encouraged
OBJECT: segSizes
Type: Histogram
Definition: A histogram of the sizes of the packets sent on the
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connection (useful for catching cases of silly-window syndrome).
This histogram is an range histogram, measuring the number of
segments whose size fell into a give range. The histogram
histValue field contains a segment size, and the histCount
field contains the number of segments between this size and
the next largest size.
Object Status: Useful.
The IpTransportLayer Dictionary: EgpValues
The EgpValues dictionary stores information about the workings of
the Exterior Gateway Protocol, defined in RFC-904. The format of
the dictionary is shown below.
EgpValues ::= SET {
egpState [0] IMPLICIT INTEGER,
[1] IMPLICIT EgpParam,
[2] IMPLICIT EgpStats OPTIONAL,
egpPeerData [3] IMPLICIT SET of EgpPeer
}
OBJECT: EgpValues
Type: SET
Definition: See above.
Object Status: Required in entities which support EGP.
The definitions of the subdictionaries of this dictionary are given
below.
OBJECT: egpState
Type: INTEGER
Definition: The state of the EGP system. The state values are:
0 -- Idle
1 -- Acquisition
2 -- Down
3 -- Up
4 -- Cease
These values are taken directly from RFC-904.
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The IpTransportLayer Dictionary: EgpValues/EgpParam
The EgpParam dictionary stores the various EGP parameters. The
format of the dictionary is shown below.
The definitions of the objects in this dictionary are given below.
OBJECT: inputPktCount
Type: Counter
Definition: The number of EGP packets received including those that
proved to be in error.
OBJECT: inputPktErrors
Type: Counter
Definition: The number of EGP packets received which proved to be
in error. This value subtracted from inputPktCount should give
the number of valid EGP packets received.
OBJECT: inputPktTypes
Type: Histogram
Definition: A histogram of types of valid EGP messages received.
The histogram histValue field contains the message type number,
and the histCount field contains the number of messages of
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this type which have been received.
Object Status: Useful.
OBJECT: outputPktCount
Type: Counter
Definition: The total number of EGP packets that the entity
attempted to send (including those that failed due to lack of
buffers, a missing route or other transient transmission
problems).
OBJECT: outputPktErrors
Type: Counter
Definition: The number of EGP packets which the entity could not
send due to transmission problems such as the lack of buffers,
a missing route or other transient transmission problems.
This value is not required to include errors which the EGP
layer could not reasonably be expected to detect such as
damage to the packet in transit. Subtracting this value from
the outputPktCount field should give the number of EGP packets
the entity believes it successfully sent.
OBJECT: outputPktTypes
Type: Histogram
Definition: A histogram of EGP messages types sent, including those
that later failed to be transmitted. The histogram histValue
field contains the message type number, and the histCount field
contains the number of messages of this type which have been sent.
Object Status: Useful.
OBJECT: egpTraffic
Type: TrafficMatrix
Definition: All EGP traffic which has originated on this machine.
The source address in the traffic matrix should be the interface
from which the packet was sent. The destination is the address
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to which the packet is to finally be delivered (not an
intermediate hop).
Object Status: Useful.
The IpTransportLayer Dictionary: EgpValues/EgpPeer
The egpPeerData field of the EgpValues dictionary is a set of
EgpPeer structures which contain the state variables for a
particular EGP neighbor. The form of the EgpPeer structure is shown
below.
EgpPeer ::= SET {
r [0] IMPLICIT Counter,
s [1] IMPLICIT Counter,
t1 [2] IMPLICIT INTEGER,
t2 [3] IMPLICIT INTEGER,
t3 [4] IMPLICIT INTEGER,
m [5] IMPLICIT BOOLEAN,
timer1 [6] IMPLICIT INTEGER,
timer2 [7] IMPLICIT INTEGER,
timer3 [8] IMPLICIT INTEGER,
addr [9] IMPLICIT IpAddress
}
OBJECT: EgpPeer
Type: SET
Definition: The state information for a given EGP neighbor.
The definition of each field is given below.
OBJECT: r
Type: Counter
Definition: The receive sequence number as defined in RFC-904.
OBJECT: s
Type: Counter
Definition: The send sequence number as defined in RFC-904.
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OBJECT: t1
Type: INTEGER
Definition: The interval between Hello command retransmissions as
defined in RFC-904.
OBJECT: t2
Type: INTEGER
Definition: The interval between Poll command retransmissions as
defined in RFC-904.
OBJECT: t3
Type: INTEGER
Definition: The interval during which neighbor-reachability
indications are counted, as defined in RFC-904.
OBJECT: m
Type: BOOLEAN
Definition: The Hello Polling mode. True if in active mode, false
if in passive mode.
Operations on Object: The defaults except as noted below.
SET: Optionally defined to change the Hello Polling mode.
OBJECT: timer1
Type: INTEGER
Definition: The value of timer 1 as defined in RFC-904.
OBJECT: timer2
Type: INTEGER
Definition: The value of timer 2 as defined in RFC-904.
OBJECT: timer3
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Type: INTEGER
Definition: The value of timer 3 as defined in RFC-904.
OBJECT: addr
Type: IpAddress
Definition: The IP address of the neighbor.
The IpTransportLayer Dictionary: UdpValues
The UdpValues dictionary stores all information on the User Datagram
Protocol, defined in RFC-768. The format of the dictionary is shown
below.
UdpValues ::= [17] IMPLICIT SET OPTIONAL {
ipID [0] IMPLICIT Counter OPTIONAL,
[1] IMPLICIT UdpStats,
udpPortData [2] IMPLICIT SET of udpPort
}
OBJECT: UdpValues
Type: SET
Definition: See above.
Object Status: Implementation of this dictionary is required if
the entity supports UDP.
The fields of this dictionary are given below.
OBJECT: ipID
Type: Counter
Definition: The next IP packet ID identifier to be used by the UDP
code.
Object Status: Required if the UDP code generates its own IP
identifiers.
The IpTransportLayer Dictionary: UdpValues/UdpStats
The UdpStats dictionary stores general information about the
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behavior of the UDP protocol on the entity. The format of the
dictionary is shown below.
Definition: The total number of UDP packets received at this entity
including any errors.
Object Status: Required if the UdpStats dictionary is implemented.
OBJECT: inputPktsErrors
Type: Counter
Definition: The number of UDP packets which could not be delivered
because of format errors, data corruption or because there was no
application at the destination port.
Object Status: Required if the UdpStats dictionary is implemented.
OBJECT: outputPkts
Type: Counter
Definition: The total number of UDP segments sent from this entity.
Object Status: Required if the UdpStats dictionary is implemented.
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The IpTransportLayer Dictionary: UdpValues/udpPortData
The udpPortData structure stores information about individual UDP
applications. The udpPortData is represented as a set of records,
udpPorts, which track the behavior of individual ports. The format
of both structures are shown below.
Operations on Object: The defaults except as noted below.
GET-MATCH. Defined on any combination of the values of
localAddress, localPort, foreignAddress and foreignPort.
Returns all ports which match the template.
The meaning of the individual fields of the udpPort record are given
below.
OBJECT: localAddress
Type: IpAddress
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Definition: The local IP address of the port. May be the default
IP address if records are accepted from any interface.
OBJECT: localPort
Type: INTEGER
Definition: The local port number.
OBJECT: foreignAddress
Type: IpAddress
Definition: Some UDP implementations permit applications to specify
the remote address from which packets will be accepted. In such
implementations, this field may be used to return the remote IP
address. If this value is set to the default IP address, then
packets from any host are accepted. The default IP address
indicates that the application has not specified the remote
address (but could if it chose).
Object Status: Required in entities which permit applications to
specify the remote address.
OBJECT: foreignPort
Type: INTEGER
Definition: Some UDP implementations permit applications to specify
the remote address from which packets will be accepted. In such
implementations, this field may be used to return the remote
port. If this value is set to 0, packets from any remote port
are accepted.
Object Status: Required in entities which permit applications to
specify the remote port.
OBJECT: maxPktSize
Type: INTEGER
Definition: The maximum UDP packet size, if any, supported by this
host.
Object Status: Required if there is a limit on the UDP packet size.
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OBJECT: pktsRcvd
Type: Counter
Definition: The total number of packets received on this port during
the lifetime of this application (i.e., application which opened
this port).
OBJECT: octetsRcvd
Type: Counter
Definition: The total number of octets received at this port.
OBJECT: pktsSent
Type: Counter
Definition: The total number of packets sent on this port during the
lifetime of this application (i.e., the application which opened
this port).
OBJECT: octetsSent
Type: Counter
Definition: The total number of octets sent on this port during the
lifetime of this application (i.e., the application which opened
this port).
The IpTransportLayer Dictionary: HmpValues
The HmpValues dictionary stores all information on the Host
Monitoring Protocol, defined in RFC-869. Since HEMS is designed to
replace HMP, the definition of this dictionary has been deferred
until a clear need for it is demonstrated.
The IpTransportLayer Dictionary: RdpValues
The RdpValues dictionary stores all information on the Reliable
Data Protocol (RDP). Since RDP is currently being tested and
revised, the definition of this dictionary is left for further
study.
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The IpTransportLayer Dictionary: NetbltValues
The NetbltValues dictionary stores all information on the Network
Block Transfer protocol. Since Netblt is currently being tested
and revised, the definition of this dictionary is left for further
study.
The IpApplications Dictionary
The IpApplications dictionary stores information about networking
applications whose operations may affect the proper operation of
the network. Examples of such applications might be domain
nameservers or distributed routing agents (such as gated or
routed). The definition of this dictionary is left for further
study.
NOTES ON RETRIEVAL OF OBJECTS
It is assumed in this system that the query processor is only one
of many concurrently running processes on an entity, and that the
operations of the other processes may affect the values of the
objects managed by the query processor. To permit this
concurrency, the query processor is not required to keep the values
frozen during the execution of a query. As a result, related
values may change during the course of the query's execution.
Applications should be prepared for this possibility.
In several places, specific mathematical relations between objects
have been specified, for example, that object X minus object Y
should yield some well-defined value. Note that in many cases,
objects X and Y are roll-over counters, in which case these
relations are only valid modulo the precision of the counter. This
is acceptable. The relationships are only intended to clarify the
association between objects.
EVENTS
In the remainder of this memo we present the format and definition
of event messages which are unsolicited updates sent from entities
to management centers.
This section needs much further work. The authors provide this
section to illustrate how the trap mechanism works. However, much
more research must be done into the questions of what events need
to be reported, and what information they must carry with them
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before this section can be completed. The authors welcome any
advice from the community on this subject.
Format of Event Messages
Event messages have the same format as replies; they are a sequence
of objects. The only difference between a event message and a
regular reply to a query is that the event message is labelled as a
event in the HEMP message header and the first object in the event
message is a special event leader describing the event. All
objects after the event message are standard objects stored by the
entity which might be useful to a monitoring center in
understanding the machine state which caused the event. Each event
has a certain number of objects that it must return. Additional
objects may be returned by loading instructions into the
eventExecution buffer of the relevant eventEntry.
The eventCode is a number which indicates the type of event. The
eventCodes are defined below.
The eventIndex is an implementation specific value. It is
considered good practice to make sure that a particular event is
only generated in one place. It may be the case that certain HEMS
generic events (for example, "no buffer space") may be generated by
more than one place in an entity's code. To allow implementors and
network managers to determine where the event is actually being
generated, implementors should make sure that a distinct eventIndex
is assigned to each location in the code that generates a
particular event.
The eventThreshold is the value of the event threshold when the
event was sent.
The eventTime indicates when the trap was generated.
The eventDescr is a text string which describes the event. This
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description should explain the general problem (e.g., "no buffer
space") and may also, optionally, include additional information
about why this particular event was generated (e.g., "could not
send ICMP redirect").
Event Definitions
The remainder of this memo presents a few generic events, which are
presented for illustration only. Implementors interested in
supporting events should contact the authors to help work out a
more comprehensive set of definitions.
The format of the event definitions is:
EVENT CODE: The event code number.
Definition: Defines the event.
Related Objects: The list of related objects which *must* be
returned following the event header. All objects should be
returned as fully qualified objects (with ASN.1 codes tracing
a complete path from the root object dictionary). If no
objects are specified, then no related objects are required.
Event Status: Events are either required of all conforming
implementations, required if the entity supports a
particular feature (e.g., TCP events) or optional.
Notes: Any additional notes about the event.
List of Events
The next few event codes are for system (as opposed to more
network oriented) events.
EVENT CODE: 0
Definition: Unused
EVENT CODE: 1
Definition: The entity has rebooted.
Related Objects: An INTEGER which is the highest HEMP
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messageID reached by the trap system before the system
crashed.
EVENT CODE: 2
Definition: The entity is about to go into test mode.
EVENT CODE: 3
Definition: The entity is about to reset.
EVENT CODE: 4
Definition: The entity is about to reboot.
EVENT CODE: 5
Definition: The entity is about to halt.
EVENT CODE: 6
Definition: The system is close to depleting its packet buffer
space.
Event Status: optional
EVENT CODE: 7
Definition: The system has depleted its packet buffer space.
EVENT CODE: 8
Definition: The system has depleted a non-packet buffer space.
Note: The two trap codes above do not deal neatly with
systems which have multiple buffer pools, each of which
may be depleted separately, with very different effects
on the entity.
The next set of event codes apply to events related to network
interfaces.
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EVENT CODE: 1024
Definition: The given interface has just come up.
Related Objects: The InterfaceData structure for the
interface.
EVENT CODE: 1025
Definition: The given interface has just been taken down.
Related Objects: The InterfaceData structure for the
interface.
EVENT CODE: 1026
Definition: The given interface has just gone into test mode.
Related Objects: The InterfaceData structure for the
interface.
The next set of event codes are used to report IP-level errors.
EVENT CODE: 2048
Definition: Unable to route IP packet.
EVENT CODE: 2049
Definition: Bad IP checksum.
EVENT CODE: 2050
Definition: An IP packet with a bad header was received (for
example, with a broadcast or multicast IP address as the
source, or the wrong IP version number, or a header length
which is too short).
Related Objects: Should return the IP header of the packet.
Note that an IP header type has not yet been defined.
EVENT CODE: 2051
Definition: Packet for unsupported IP transport protocol.
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RFC 1024 HEMS Definitions October 1987
Related Objects: Should return the IP header of the packet.
Note that an IP header type has not yet been defined.
EVENT CODE: 2052
Definition: A stunted IP packet was received (smaller than
the IP length says it should be).
Related Objects: Should return the IP header of the packet.
Note that an IP header type has not yet been defined.
EVENT CODE: 2053
Definition: An oversize IP packet was received (larger than
the IP length says it should be).
Related Objects: Should return the IP header of the packet.
Note that an IP header type has not yet been defined.
EVENT CODE: 2054
Definition: A good IP packet was discarded (usually to free
up buffer space).
Related Objects: Should return the IP header of the packet.
Note that an IP header type has not yet been defined.
EVENT CODE: 2055
Definition: An IP packet's time-to-live as expired.
Related Objects: Should return the IP header of the packet.
Note that an IP header type has not yet been defined.
EVENT CODE: 2056
Definition: This IP fragment has timed out.
Related Objects: Should return the header of the fragment.
Note that an IP header type has not yet been defined.
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AREAS FOR FURTHER STUDY
There are several parts of this document that could use additional
study. Comments from readers are welcome.
The whole event system needs thorough examination. It is not clear
that the event control mechanism strikes the proper balance between
sufficient flexibility to allow monitoring centers to customize
their event stream, and keeping the basic mechanism simple.
Further, the problem of defining generic events for all entities is
an immense task. Finally, the system of appending required values
after traps, followed by optional values read from the data tree
feels a bit cumbersome. It would be nice if all values were in the
same data space.
Several readers have suggested it might make more sense to keep TCP
connection parameters on a per-connection basis rather than
globally.
The method for specifying the TCP round-trip time algorithm needs
to be refined. The expression syntax should be sufficiently
general that all round-trip-time-related algorithms (e.g., those
for time or routing protocols) can be expressed in it.
Much more research could be done into what information needs to be
gathered to effectively monitor a network.
