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rfc:rfc1028

Network Working Group J. Davin Request for Comments: 1028 Proteon, Inc.

                                                               J. Case
                                  University of Tennessee at Knoxville
                                                              M. Fedor
                                                    Cornell University
                                                        M. Schoffstall
                                      Rensselaer Polytechnic Institute
                                                         November 1987
                A Simple Gateway Monitoring Protocol

1. Status of this Memo

 This document is being distributed to members of the Internet
 community in order to solicit their reactions to the proposals
 contained in it.  While the issues discussed may not be directly
 relevant to the research problems of the Internet, they may be
 interesting to a number of researchers and implementors.
 This memo defines a simple application-layer protocol by which
 management information for a gateway may be inspected or altered by
 logically remote users.
 This proposal is intended only as an interim response to immediate
 gateway monitoring needs while work on more elaborate and robust
 designs proceeds with the care and deliberation appropriate to that
 task.  Accordingly, long term use of the mechanisms described here
 should be seriously questioned as more comprehensive proposals emerge
 in the future.  Distribution of this memo is unlimited.

2. Protocol Design Strategy

 The proposed protocol is shaped in large part by the desire to
 minimize the number and complexity of management functions realized
 by the gateway itself.  This goal is attractive in at least four
 respects:
 (1)  The development cost for gateway software necessary to
      support the protocol is accordingly reduced.
 (2)  The degree of management function that is remotely
      supported is accordingly increased, thereby admitting
      fullest use of internet resources in the management task.

Davin, Case, Fedor and Schoffstall [Page 1] RFC 1028 Simple Gateway Monitoring November 1987

 (3)  The degree of management function that is remotely
      supported is accordingly increased, thereby imposing the
      fewest possible restrictions on the form and sophistication
      of management tools.
 (4)  A simplified set of management functions is easily
      understood and used by developers of gateway management
      tools.
 A second design goal is that the functional paradigm for monitoring
 and control be sufficiently extensible to accommodate additional,
 possibly unanticipated aspects of gateway operation.
 A third goal is that the design be, as much as possible, independent
 of the architecture and mechanisms of particular hosts or particular
 gateways.
 Consistent with the foregoing design goals are a number of decisions
 regarding the overall form of the protocol design.
 One such decision is to model all gateway management functions as
 alterations or inspections of various parameter values.  By this
 model, a protocol entity on a logically remote host (possibly the
 gateway itself) interacts with a protocol entity resident on the
 gateway in order to alter or retrieve named portions (variables) of
 the gateway state.  This design decision has at least two positive
 consequences:
 (1)  It has the effect of limiting the number of essential
      management functions realized by the gateway to two: one
      operation to assign a value to a specified configuration
      parameter and another to retrieve such a value.
 (2)  A second effect of this decision is to avoid introducing
      into the protocol definition support for imperative
      management commands: the number of such commands is in
      practice ever-increasing, and the semantics of such
      commands are in general arbitrarily complex.
 The exclusion of imperative commands from the set of explicitly
 supported management functions is unlikely to preclude any desirable
 gateway management operation.  Currently, most gateway commands are
 requests either to set the value of some gateway parameter or to
 retrieve such a value, and the function of the few imperative
 commands currently supported is easily accommodated in an
 asynchronous mode by this management model.  In this scheme, an
 imperative command might be realized as the setting of a parameter
 value that subsequently triggers the desired action.

Davin, Case, Fedor and Schoffstall [Page 2] RFC 1028 Simple Gateway Monitoring November 1987

 A second design decision is to realize any needed authentication
 functionality in a distinct protocol layer that provides services to
 the monitoring protocol itself.  The most important benefit of this
 decision is a reduction in the complexity of the individual protocol
 layers - thereby easing the task of implementation.
 Consistent with this layered design strategy is a third design
 decision that the identity of an application protocol entity is known
 to its peers only by the services of the underlying authentication
 protocol.  Implicit in this decision is a model of access control by
 which access to variables of a gateway configuration is managed in
 terms of the association between application entities and sessions of
 the authentication protocol.  Thus, multi-level access to gateway
 variables is supported by multiple instances of the application
 protocol entity, each of which is characterized by:
 (1)  the set of gateway variables known to said entity,
 (2)  the mode of access (READ-ONLY or READ-WRITE) afforded to
      said set of variables, and
 (3)  the authentication protocol session to which belong the
      messages sent and received by said entity.
 A fourth design decision is to adopt the conventions of the CCITT
 X.409 recommendation [1] for representing the information exchanged
 between protocol entities.  One cost of this decision is a modest
 increase in the complexity of the protocol implementation.  One
 benefit of this decision is that protocol data are represented on the
 network in a machine-independent, widely understood, and widely
 accepted form.  A second benefit of this decision is that the form of
 the protocol messages may be concisely and understandably described
 in the X.409 language defined for such purposes.
 A fifth design decision, consistent with the goal of minimizing
 gateway complexity, is that the variables manipulated by the protocol
 assume only integer or octet string type values.
 A sixth design decision, also consistent with the goal of minimizing
 gateway complexity, is that the exchange of protocol messages
 requires only an unreliable datagram transport, and, furthermore,
 that every protocol message is entirely and independently
 representable by a single transport datagram.  While this document
 specifies the exchange of protocol messages via the UDP protocol [2],
 the design proposed here is in general suitable for use with a wide
 variety of transport mechanisms.

Davin, Case, Fedor and Schoffstall [Page 3] RFC 1028 Simple Gateway Monitoring November 1987

 A seventh design decision, consistent with the goals of simplicity
 and extensibility, is that the variables manipulated by the protocol
 are named by octet string values.  While this decision departs from
 the architectural traditions of the Internet whereby objects are
 identified by assigned integer values, the naming of variables by
 octet strings affords at least two valuable benefits.  Because the
 set of octet string values constitutes a variable name space that, as
 convenient, manifests either flat or hierarchical structure,
 (1)  a single, simple mechanism can provide both random access
      to individual variables and sequential access to
      semantically related groups of variables, and
 (2)  the variable name space may be extended to accommodate
      unforeseen needs without compromising either the
      relationships among existing variables or the potential
      for further extensions to the space.
 An eighth design decision is to minimize the number of unsolicited
 messages required by the protocol definition.  This decision is
 consistent with the goal of simplicity and motivated by the desire to
 retain maximal control over the amount of traffic generated by the
 network management function - even at the expense of additional
 protocol overhead.  The strategy implicit in this decision is that
 the monitoring of network state at any significant level of detail is
 accomplished primarily by polling for appropriate information on the
 part of the monitoring center.  In this context, the definition of
 unsolicited messages in the protocol is confined to those strictly
 necessary to properly guide a monitoring center regarding the timing
 and focus of its polling.

3. The Gateway Monitoring Protocol

 The gateway monitoring protocol is an application protocol by which
 the variables of a gateway's configuration may be inspected or
 altered.
 Communication among application protocol entities is by the exchange
 of protocol messages using the services of the authentication
 protocol described elsewhere in this document.  Each such message is
 entirely and independently represented by a single message of the
 underlying authentication protocol.  An implementation of this
 protocol need not accept protocol messages whose length exceeds 484
 octets.
 The form and function of the four message types recognized by a
 protocol entity is described below.  The type of a given protocol
 message is indicated by the value of the implicit type tag for the

Davin, Case, Fedor and Schoffstall [Page 4] RFC 1028 Simple Gateway Monitoring November 1987

 data structure that is represented by said message according to the
 conventions of the CCITT X.409 recommendation.

3.1. The Get Request Message Type

 The form of a message of Get Request type is described below in the
 language defined in the CCITT X.409 recommendation:
 var_value_type          ::=     CHOICE {
                                 INTEGER,
                                 OCTET STRING
                                   }
 var_name_type           :=      OCTET STRING
 var_op_type             ::=     SEQUENCE {
                         var_name                var_name_type,
                         var_value               var_value_type
                         }
 var_op_list_type        ::=     SEQUENCE OF var_op_type
 error_status_type       ::=     INTEGER {
                         gmp_err_noerror         (0),
                         gmp_err_too_big         (1),
                         gmp_err_nix_name        (2),
                         gmp_err_bad_value       (3)
                         }
 error_index_type        ::=     INTEGER
 request_id_type         ::=     INTEGER
 get_req_message_type    ::=     [ APPLICATION 1 ] IMPLICIT
                         SEQUENCE {
                         request_id              request_id_type,
                         error_status            error_status_type,
                         error_index             error_index_type,
                         var_op_list             var_op_list_type

Davin, Case, Fedor and Schoffstall [Page 5] RFC 1028 Simple Gateway Monitoring November 1987

                         }
 Upon receipt of a message of this type, the receiving entity responds
 according to any applicable rule in the list below:
 (1)  If, for some var_op_type component of the received message, the
      value of the var_name field does not lexicographically precede
      the name of some variable known to the receiving entity, then
      the receiving entity sends to the originator of the received
      message a message of identical form except that the indicated
      message type is Get Response, the value of the error_status
      field is gmp_err_nix_name, and the value of the error_index
      field is the unit-based index of said var_op_type component in
      the received message.
 (2)  If the size of the Get Response type message generated as
      described below would exceed the size of the largest message
      for which the protocol definition requires acceptance, then the
      receiving entity sends to the originator of the received message
      a message of identical form except that the indicated message
      type is Get Response, the value of the error_status field is
      gmp_err_too_big, and the value of the error_index field is zero.
 If none of the foregoing rules apply, then the receiving entity sends
 to the originator of the received message a Get Response type message
 such that, for each var_op_type component of the received message, a
 corresponding component of the generated message represents the name
 and value of that variable whose name is, in the lexicographical
 ordering of the names of all variables known to the receiving entity
 together with the value of the var_name field of the given component,
 the immediate successor to that value.  The value of the error_status
 field of the generated message is gmp_err_noerror and the value of
 the error_index field is zero.  The value of the request_id field of
 the generated message is that for the received message.
 Messages of the Get Request type are generated by a protocol entity
 only at the request of the application user.

3.2. The Get Response Message Type

 The form of messages of this type is identical to that of Get Request
 type messages except for the indication of message type. In the CCITT
 X.409 language,
 get_rsp_message_type    ::=     [ APPLICATION 2 ] IMPLICIT
                         SEQUENCE {

Davin, Case, Fedor and Schoffstall [Page 6] RFC 1028 Simple Gateway Monitoring November 1987

                         request_id              request_id_type,
                         error_status            error_status_type,
                         error_index             error_index_type,
                         var_op_list             var_op_list_type
                         }
 The response of a protocol entity to a message of this type is to
 present its contents to the application user.
 Messages of the Get Response type are generated by a protocol entity
 only upon receipt of Set Request or Get Request type messages as
 described elsewhere in this document.

3.3. The Trap Request Message Type

 The form of a message of this type is described below in the language
 defined in the CCITT X.409 recommendation:
 val_list_type           ::=     SEQUENCE OF var_value_type
 trap_type_type          ::=     INTEGER
 trap_req_message_type   ::=     [ APPLICATION 3 ] IMPLICIT
                         SEQUENCE {
                         trap_type               trap_type_type,
                         val_list                val_list_type
                         }
 The response of a protocol entity to a message of this type is to
 present its contents to the application user.
 Messages of the Trap Request type are generated by a protocol entity
 only at the request of the application user.
 The significance of the val_list component of a Trap Request type
 message is implementation-specific.
 Interpretations for negative values of the trap_type field are
 implementation-specific.  Interpretations for non-negative values of
 the trap_type field are defined below.

3.3.1. The Cold Start Trap Type

 A Trap Request type message for which the value of the trap_type

Davin, Case, Fedor and Schoffstall [Page 7] RFC 1028 Simple Gateway Monitoring November 1987

 field is 0, signifies that the sending protocol entity is
 reinitializing itself such that the gateway configuration or the
 protocol entity implementation may be altered.

3.3.2. The Warm Start Trap Type

 A Trap Request type message for which the value of the trap_type
 field is 1, signifies that the sending protocol entity is
 reinitializing itself such that neither the gateway configuration nor
 the protocol entity implementation is altered.

3.3.3. The Link Failure Trap Type

 A Trap Request type message for which the value of the trap_type
 field is 2, signifies that the sending protocol entity recognizes a
 failure in one of the communication links represented in the gateway
 configuration.

3.3.4. The Authentication Failure Trap Type

 A Trap Request type message for which the value of the trap_type
 field is 3, signifies that the sending protocol entity is the
 addressee of a protocol message that is not properly authenticated.

3.3.5. The EGP Neighbor Loss Trap Type

 A Trap Request type message for which the value of the trap_type
 field is 4, signifies that an EGP neighbor for whom the sending
 protocol entity was an EGP peer has been marked down and the peer
 relationship no longer obtains.

3.4. The Set Request Message Type

 The form of messages of this type is identical to that of Get Request
 type messages except for the indication of message type.  In the
 CCITT X.409 language:
 set_req_message_type    ::=     [ APPLICATION 4 ] IMPLICIT
                         SEQUENCE {
                         request_id              request_id_type,
                         error_status            error_status_type,
                         error_index             error_index_type,
                         var_op_list             var_op_list_type
                         }

Davin, Case, Fedor and Schoffstall [Page 8] RFC 1028 Simple Gateway Monitoring November 1987

 Upon receipt of a message of this type, the receiving entity responds
 according to any applicable rule in the list below:
 (1)  If, for some var_op_type component of the received message, the
      value of the var_name field names no variable known to the
      receiving entity, then the receiving entity sends to the
      originator of the received message a message of identical form
      except that the indicated message type is Get Response, the
      value of the error_status field is gmp_err_nix_name, and the
      value of the error_index field is the unit-based index of said
      var_op_type component in the received message.
 (2)  If, for some var_op_type component of the received message, the
      contents of the var_value field does not, according to the CCITT
      X.409 recommendation, manifest a type, length, and value that is
      consistent with that required for the variable named by the
      value of the var_name field, then the receiving entity sends to
      the originator of the received message a message of identical
      form except that the indicated message type is Get Response, the
      value of the error_status field is gmp_err_bad_value, and the
      value of the error_index field is the unit-based index of said
      var_op_type component in the received message.
 (3)  If the size of the Get Response type message generated as
      described below would exceed the size of the largest message for
      which the protocol definition requires acceptance, then the
      receiving entity sends to the originator of the received
      message a message of identical form except that the indicated
      message type is Get Response, the value of the error_status
      field is gmp_err_too_big, and the value of the error_index field
      is zero.
 If none of the foregoing rules apply, then for each var_op_type
 component of the received message, according to the sequence of such
 components represented by said message, the value represented by the
 var_value field of the given component is assigned to the variable
 named by the value of the var_name field of that component.  The
 receiving entity sends to the originator of the received message a
 message of identical form except that the indicated message type is
 Get Response, the value of the error_status field is gmp_err_noerror,
 and the value of the error_index field is zero.
 Messages of the Set Request type are generated by a protocol entity
 only at the request of the application user.
 Recognition and processing of Set Request type frames is not required
 by the protocol definition.

Davin, Case, Fedor and Schoffstall [Page 9] RFC 1028 Simple Gateway Monitoring November 1987

4. The Authentication Protocol

 The authentication protocol is a session-layer protocol by which
 messages specified by a protocol user are selectively delivered to
 other protocol users.  The protocol definition precludes delivery to
 a protocol user of any user message for which the protocol
 representation lacks a specified "authentic" form.
 Communication among authentication protocol entities is accomplished
 by the exchange of protocol messages, each of which is entirely and
 independently represented by a single UDP datagram.  An
 authentication protocol entity responds to protocol messages received
 at UDP port 153 on the host with which it is associated.
 A half-session of the authentication protocol is, for any ordered
 pair of protocol users, the set of messages sent from the first user
 of the pair to the second user of said pair.  A session of the
 authentication protocol is defined to be union of two complementary
 half-sessions of the protocol - that is, the set of messages
 exchanged between a given pair of protocol users.  Associated with
 each protocol half-session is a triplet of functions:
 (1)  The authentication function for a given half-session is a
      boolean-valued function that characterizes the set of
      authentication protocol messages that are of acceptable,
      authentic form with respect to the set of all possible
      authentication protocol messages.
 (2)  The message interpretation function for a given half-
      session is a mapping from the set of authentication
      protocol messages accepted by the authentication function
      for said half-session to the set of all possible user
      messages.
 (3)  The message representation function for a given half-
      session is a mapping that is the inverse of the message
      interpretation function for said half-session.
 The association between half-sessions of the authentication protocol
 and triplets of functions is not defined in this document.
 The form and function of the single message type recognized by a
 protocol entity is described below.  The type of a given protocol
 message is indicated by the value of the implicit type tag for the
 data structure that is represented by said message according to the
 conventions of the CCITT X.409 recommendation.

Davin, Case, Fedor and Schoffstall [Page 10] RFC 1028 Simple Gateway Monitoring November 1987

4.1. The Data Request Message Type

 Messages of this type are represented by a sequence of fields whose
 form and interpretation are described below.

4.1.1. The Message Length Field

 The Message Length field of a given Data Request message represents
 the length of said message as an unsigned, 16-bit, binary integer.
 This value is encoded such that more significant bits precede less
 significant bits in the order of transmission and includes the length
 of the Message Length field itself.

4.1.2. The Session ID Length Field

 The Session ID Length field of a given Data Request message
 represents the length, in octets, of the Session ID field of said
 message.  This value is encoded as an unsigned, 8-bit, binary
 integer.

4.1.3. The Session ID Field

 The Session ID field of a given Data Request message represents the
 name of the protocol session to which said message belongs.  The
 value of this field is encoded as asequence of octets whose length is
 the value of the Session ID Length field for said message.

4.1.4. The User Data Field

 The User Data field of a given Data Request message represents a
 message being passed from one protocol user to another.  The value of
 this field is encoded according to conventions implicit in the
 message representation function for the appropriate half of the
 protocol session named by the value of the Session ID field for said
 message.
 Upon receipt of a Data Request type message, the receiving
 authentication protocol entity verifies the form of said message by
 application of the authentication function associated with its half
 of the session named by the value of the Session ID field in the
 received message.  If the form of the received message is accepted as
 "authentic" by said function, then the user message computed by the
 application of the message interpretation function for said half-
 session to the value of the User Data field of the received message
 is presented to the protocol user together with an indication of the
 protocol session to which the received message belongs.

Davin, Case, Fedor and Schoffstall [Page 11] RFC 1028 Simple Gateway Monitoring November 1987

 Otherwise, the message is discarded and an indication of the receipt
 of an unauthenticated message is presented to the protocol user.
 A message of this type is generated only at the request of the
 protocol user to communicate a message to another user of the
 protocol.  Such a request specifies the user message to be sent as
 well as the session of the authentication protocol to which said user
 message belongs.  The value of the Session ID field of the generated
 message is the name of the session specified in the user request.
 The value of the User Data field of the generated message is computed
 by applying the message representation function for the appropriate
 half of the specified session to the specified user message.

5. Variable Names

 The variables retrieved or manipulated by the application protocol
 are named by octet string values.  Such values are represented in
 this document in two ways:
 (1)  A variable name octet string may be represented
     numerically by a sequence of hexadecimal numbers, each of
     which denotes the value of the corresponding octet in
     said string.
 (2)  A variable name octet string may be represented
      symbolically by a character string whose form reflects
      the sequence of octets in said name while at the same
      time suggesting to a human reader the semantics of the
      named variable.
 Variable name octet strings are represented symbolically according to
 the following two rules:
 (1)  The symbolic character string representation of the
      variable name of zero length is the character string of
      zero length.
 (2)  The symbolic character string representation of a
      variable name of non-zero length n is the concatenation
      of the symbolic character string representation of the
      variable name formed by the first (n - 1) octets of the
      given name together with the underscore character ("_")
      and a character string that does not include the
      underscore character, such that the resulting character
      string is unique among the symbolic character string
      representations for all variable names of length n.

Davin, Case, Fedor and Schoffstall [Page 12] RFC 1028 Simple Gateway Monitoring November 1987

 Thus, for example, the variable names represented numerically as:
                       01 01 01,
                       01 01 02,
                       01 02 01,
                       01 03 01 03 01,
                       01 03 01 03 02,
                       01 03 01 04 01, and
                       01 03 01 04 02
 might be represented symbolically by the character strings:
                       _GW_version_id,
                       _GW_version_rev,
                       _GW_cfg_nnets,
                       _GW_net_if_type_net1,
                       _GW_net_if_type_net2,
                       _GW_net_if_speed_net1, and
                       _GW_net_if_speed_net2.
 All variable names are terminated by an implementation specific octet
 string of non-zero length.  Thus, a complete variable name is not
 specified for any of the variables defined in this document.  Rather,
 for each defined variable, some prefix portion of its name is
 specified, with the understanding that the rightmost portion of its
 name is specific to the protocol implementation.
 Fullest exploitation of the semantics of the Get Request type message
 requires that names for related variables be chosen so as to be
 contiguous in the lexicographic ordering of all variable names
 recognized by an application protocol entity.  This principle is
 observed in the naming of variables currently defined by this
 document, and it should be observed as well for variables defined by
 subsequent revisions of this document and for variables introduced by
 particular implementations of the protocol.
 A particular implementation of a protocol entity may present
 variables in addition to those defined by this document, provided
 that in no case will an implementation-specific variable be presented
 as having a name identical to that for one of the variables defined
 here.  By convention, the names of variables specific to a particular
 implementation share a common prefix that distinguishes said
 variables from those defined in this document and from those that may
 be presented by other implementations of an application protocol
 entity.  For example, variables specific to an implementation of this
 protocol in version 1.3 of the Squeaky gateway product of the
 Swinging Gateway company might have the names represented by:

Davin, Case, Fedor and Schoffstall [Page 13] RFC 1028 Simple Gateway Monitoring November 1987

               01 FF 01 01 13 01,
               01 FF 01 01 13 02, and
               01 FF 01 01 13 03,
 for which the corresponding symbolic representations might be:
               _GW_impl_Swinging_Squeaky_v1.3_variableA,
               _GW_impl_Swinging_Squeaky_v1.3_variableB, and
               _GW_impl_Swinging_Squeaky_v1.3_variableC.
 The names and semantics of implementation-specific variables are not
 otherwise defined by this document, although implementors are
 encouraged to publish such definitions either as appendices to this
 document or by other appropriate means.
 Variable names of which the initial portion is represented
 numerically as 02 and symbolically as "_HOST" are reserved for future
 use.  Variable names of which the initial portion is represented
 numerically as 03 and symbolically as "_TS" are similarly reserved.

6. Required Variables

 To the extent that the information represented by a variable defined
 in this section is also represented internally by a gateway for which
 this protocol is realized, access to that variable must be afforded
 by at least one application protocol entity associated with said
 gateway.

6.1. The _GW_version_id Variable

 The variable such that the initial portion of its name is represented
 symbolically as "_GW_version_id" and numerically as:
               01 01 01
 has an octet string value that identifies the protocol entity
 implementation (e.g., "ACME Packet-Whiz Model II").

6.2. The _GW_version_rev Variable

 The variable such that the initial portion of its name is represented
 symbolically as "_GW_version_rev" and numerically as:
               01 01 02
 has an integer value that identifies the revision level of the entity
 implementation.  The encoding of the revision level as an integer

Davin, Case, Fedor and Schoffstall [Page 14] RFC 1028 Simple Gateway Monitoring November 1987

 value is implementation-specific.

6.3. The _GW_cfg_nnets Variable

 The variable such that the initial portion of its name is represented
 symbolically as "_GW_cfg_nnets" and numerically as:
               01 02 01
 has an integer value that represents the number of logical network
 interfaces afforded by the configuration of the gateway.

6.4. Network Interface Variables

 This section describes a related set of variables that represent
 attributes of the logical network interfaces afforded by the gateway
 configuration.  Each such network interface is uniquely identified by
 an octet string.  The convention by which names are assigned to the
 network interfaces of a gateway is implementation-specific.

6.4.1. The _GW_net_if_type Variable Class

 A variable such that the initial portion of its name is represented
 symbolically as "_GW_net_if_type" and numerically as:
               01 03 01 03
 has an integer value that represents the type of the network
 interface identified by the remainder of the name for said variable.
 The value of a variable of this class represents network type
 according to the conventions described in Appendix 1.

6.4.2. The _GW_net_if_speed Variable Class

 A variable such that the initial portion of its name is represented
 symbolically as "_GW_net_if_speed" and numerically as:
               01 03 01 04
 has an integer value that represents the estimated nominal bandwidth
 in bits per second of the network interface identified by the
 remainder of the name for said variable.

6.4.3. The _GW_net_if_in_pkts Variable Class

 A variable such that the initial portion of its name is represented
 symbolically as "_GW_net_if_in_pkts" and numerically as:

Davin, Case, Fedor and Schoffstall [Page 15] RFC 1028 Simple Gateway Monitoring November 1987

               01 03 01 01 01
 has an integer value that represents the number of packets received
 by the gateway over the network interface identified by the remainder
 of the name for said variable.

6.4.4. The _GW_net_if_out_pkts Variable Class

 A variable such that the initial portion of its name is represented
 symbolically as "_GW_net_if_out_pkts" and numerically as:
               01 03 01 02 01
 has an integer value that represents the number of packets
 transmitted by the gateway over the network interface identified by
 the remainder of the name for said variable.

6.4.5. The _GW_net_if_in_bytes Variable Class

 A variable such that the initial portion of its name is represented
 symbolically as "_GW_net_if_in_bytes" and numerically as:
               01 03 01 01 02
 has an integer value that represents the number of octets received by
 the gateway over the network interface identified by the remainder of
 the name for said variable.

6.4.6. The _GW_net_if_out_bytes Variable Class

 A variable such that the initial portion of its name is represented
 symbolically as "_GW_net_if_out_bytes" and numerically as:
               01 03 01 02 02
 has an integer value that represents the number of octets transmitted
 by the gateway over the network interface identified by the remainder
 of the name for said variable.

6.4.7. The _GW_net_if_in_errors Variable Class

 A variable such that the initial portion of its name is represented
 symbolically as "_GW_net_if_in_errors" and numerically as:
               01 03 01 01 03
 has an integer value that represents the number of reception errors
 encountered by the gateway on the network interface identified by the

Davin, Case, Fedor and Schoffstall [Page 16] RFC 1028 Simple Gateway Monitoring November 1987

 remainder of the name for said variable.  The definition of a
 reception error is implementation-specific and may vary according to
 network type.

6.4.8. The _GW_net_if_out_errors Variable Class

 A variable such that the initial portion of its name is represented
 symbolically as "_GW_net_if_out_errors" and numerically as:
              01 03 01 02 03
 has an integer value that represents the number of transmission
 errors encountered by the gateway on the network interface identified
 by the remainder of the name for said variable.  The definition of a
 transmission error is implementation-specific and may vary according
 to network type.

6.4.9. The _GW_net_if_status Variable Class

 A variable such that the initial portion of its name is represented
 symbolically as "_GW_net_if_status" and numerically as:
               01 03 01 05
 has an integer value that represents the current status of the
 network interface identified by the remainder of the name for said
 variable.  Network status is represented according to the conventions
 described in Appendix 2.

6.5. Internet Protocol Variables

 This section describes variables that represent information related
 to protocols and mechanisms of the Internet Protocol (IP) family [3].

6.5.1. Protocol Address Variable Classes

 This section describes a related set of variables that represent
 attributes of the the IP interfaces presented by a gateway on the
 various networks to which it is attached.  Each such protocol
 interface is uniquely identified by an octet string.  The convention
 by which names are assigned to the protocol interfaces for a gateway
 is implementation-specific.

6.5.1.1. The _GW_pr_in_addr_value Variable Class

 A variable such that the initial portion of its name is represented
 symbolically as "_GW_pr_in_addr_value" and numerically as:

Davin, Case, Fedor and Schoffstall [Page 17] RFC 1028 Simple Gateway Monitoring November 1987

               01 04 01 01 01
 has an octet string value that literally represents the 32-bit
 Internet address for the IP interface identified by the remainder of
 the name for said variable.

6.5.1.2. The _GW_pr_in_addr_scope Variable Class

 A variable such that the initial portion of its name is represented
 symbolically as "_GW_pr_in_addr_scope" and numerically as:
               01 04 01 01 02
 has an octet string value that names the network interface with which
 the IP interface identified by the remainder of the name for said
 variable is associated.

6.5.2. Exterior Gateway Protocol (EGP) Variables

 This section describes variables that represent information related
 to protocols and mechanisms of the EGP protocol [4].

6.5.2.1. The _GW_pr_in_egp_core Variable

 A variable such that the initial portion of its name is represented
 symbolically as "_GW_pr_in_egp_core" and numerically as:
               01 04 01 03 01
 has an integer value that characterizes the associated gateway with
 respect to the set of INTERNET core gateways.  A nonzero value
 indicates that the associated gateway is part of the INTERNET core.

6.5.2.2. The _GW_pr_in_egp_as Variable Class

 A variable such that the initial portion of its name is represented
 symbolically as "_GW_pr_in_egp_as" and numerically as:
               01 04 01 03 02
 has an integer value that literally identifies an Autonomous System
 to which this gateway belongs.

6.5.2.3. The EGP Neighbor Variable Classes

 This section describes a related set of variables that represent
 attributes of "neighbors" with which the gateway may be associated by
 EGP.  Each such EGP neighbor is uniquely identified by an octet

Davin, Case, Fedor and Schoffstall [Page 18] RFC 1028 Simple Gateway Monitoring November 1987

 string. The convention by which names are assigned to EGP neighbors
 of a gateway is implementation-specific.

6.5.2.3.1. The _GW_pr_in_egp_neighbor_addr Variable Class

 A variable such that the initial portion of its name is represented
 symbolically as "_GW_pr_in_egp_neighbor_addr" and numerically as:
               01 04 01 03 03 01
 has an octet string value that literally represents the 32-bit
 Internet address for the EGP neighbor identified by the remainder of
 the name for said variable.

6.5.2.3.2. The _GW_pr_in_egp_neighbor_state Variable Class

 A variable such that the initial portion of its name is represented
 symbolically as "_GW_pr_in_egp_neighbor_state" and numerically as:
               01 04 01 03 03 02
 has an octet string value that represents the EGP protocol state of
 the gateway with respect to the EGP neighbor identified by the
 remainder of the name for said variable. The meaningful values for
 such a variable are: "IDLE," "ACQUISITION," "DOWN," "UP," and
 "CEASE."

6.5.2.4. The _GW_pr_in_egp_errors Variable

 The variable such that the initial portion of its name is represented
 symbolically as "_GW_pr_in_egp_errors" and numerically as:
               01 04 01 03 05
 has an integer value that represents the number of EGP protocol
 errors.

6.5.3. Routing Variable Classes

 This section describes a related set of variables that represent
 attributes of the the IP routes by which a gateway directs packets to
 various destinations on the Internet.  Each such route is uniquely
 identified by an octet string that is the concatenation of the
 literal 32-bit value of the Internet address for the destination of
 said route together with an implementation-specific octet string.
 The convention by which names are assigned to the Internet routes for
 a gateway is in all other respects implementation-specific.

Davin, Case, Fedor and Schoffstall [Page 19] RFC 1028 Simple Gateway Monitoring November 1987

6.5.3.1. The _GW_pr_in_rt_gateway Variable Class

 A variable such that the initial portion of its name is represented
 symbolically as "_GW_pr_in_rt_gateway" and numerically as:
               01 04 01 02 01
 has an octet string value that literally represents the 32-bit
 Internet address of the next gateway to which traffic is directed by
 the route identified by the remainder of the name for said variable.

6.5.3.2. The _GW_pr_in_rt_type Variable Class

 A variable such that the initial portion of its name is represented
 symbolically as "_GW_pr_in_rt_type" and numerically as:
               01 04 01 02 02
 has an integer value that represents the type of the route identified
 by the remainder of the name for said variable.  Route types are
 identified according to the conventions described in Appendix 3.

6.5.3.3. The _GW_pr_in_rt_how-learned Variable Class

 A variable such that the initial portion of its name is represented
 symbolically as "_GW_pr_in_rt_how-learned" and numerically as:
                 01 04 01 02 03
 has an octet string value that represents the source of the
 information from which the route identified by the remainder of the
 name for said variable is generated. The meaningful values of such a
 variable are: "STATIC," "EGP," and "RIP."

6.5.3.4. The _GW_pr_in_rt_metric0 Variable Class

 A variable such that the initial portion of its name is represented
 symbolically as "_GW_pr_in_rt_metric0" and numerically as:
               01 04 01 02 04
 has an integer value that represents the quality (in terms of cost,
 distance from the ultimate destination, or other metric) of the route
 identified by the remainder of the name for said variable.

6.5.3.5. The _GW_pr_in_rt_metric1 Variable Class

 A variable such that the initial portion of its name is represented

Davin, Case, Fedor and Schoffstall [Page 20] RFC 1028 Simple Gateway Monitoring November 1987

 symbolically as "_GW_pr_in_rt_metric1" and numerically as:
               01 04 01 02 05
 has an integer value that represents the quality (in terms of cost,
 distance from the ultimate destination, or other metric) of the route
 identified by the remainder of the name for said variable.

6.6. DECnet Protocol Variables

 This section describes variables that represent information related
 to protocols and mechanisms of the DEC Digital Network Architecture.
 DEC and DECnet are registered trademarks of Digital Equipment
 Corporation.

6.7. XNS Protocol Variables

 This section describes variables that represent information related
 to protocols and mechanisms of the Xerox Network System.  Xerox
 Network System and XNS are registered trademarks of the XEROX
 Corporation.

7. Implementation-Specific Variables

 Additional variables that may be presented for inspection or
 manipulation by particular protocol entity implementations are
 described in Appendices to this document.

8. References

 [1]  CCITT, "Message Handling Systems: Presentation Transfer
      Syntax and Notation", Recommendation X.409, 1984.
 [2]  Postel, J., "User Datagram Protocol", RFC-768,
      USC/Information Sciences Institute, August 1980.
 [3]  Postel, J., "Internet Protocol", RFC-760, USC/Information
      Sciences Institute, January 1980.
 [4]  Rosen, E., "Exterior Gateway Protocol", RFC-827, Bolt
      Beranek and Newman, October 1982.

9. Appendix 1: Network Type Representation

Numeric representations for various types of networks are presented

 below:

Davin, Case, Fedor and Schoffstall [Page 21] RFC 1028 Simple Gateway Monitoring November 1987

                       Value   Network Type
                       ====================
                       0       Unspecified
                       1       IEEE 802.3 MAC
                       2       IEEE 802.4 MAC
                       3       IEEE 802.5 MAC
                       4       Ethernet
                       5       ProNET-80
                       6       ProNET-10
                       7       FDDI
                       8       X.25
                       9       Point-to-Point Serial
                       10      Proprietary Point-to-Point Serial
                       11      ARPA 1822 HDH
                       12      ARPA 1822
                       13      AppleTalk
                       14      StarLAN

10. Appendix 2: Network Status Representation

Numeric representations for network status are presented below.

                       Value   Network Status
                       ======================
                       0       Interface Operating Normally
                       1       Interface Not Present
                       2       Interface Disabled
                       3       Interface Down
                       4       Interface Attempting Link

11. Appendix 3: Route Type Representation

Numeric representations for route types are presented below.

                       Value   Route Type
                       ==================
                       0       Route to Nowhere -- ignored
                       1       Route to Directly Connected Network
                       2       Route to a Remote Host
                       3       Route to a Remote Network
                       4       Route to a Sub-Network

12. Appendix 4: Initial Implementation Strategy

 The initial objective of implementing the protocol specified in this
 document is to provide a mechanism for monitoring Internet gateways.
 While the protocol design makes some provision for gateway management

Davin, Case, Fedor and Schoffstall [Page 22] RFC 1028 Simple Gateway Monitoring November 1987

 functions as well, this aspect of the design is not fully developed
 and needs further refinement before a generally useful implementation
 could be produced.  Accordingly, initial implementations will not
 generate or respond to the optional Set Request message type.
 The protocol defined here may be subsequently refined based upon
 experience with early implementations or upon further study of the
 problem of gateway management.  Moreover, it may be superceded by
 other proposals in the area of gateway monitoring and control.
 Implementations of the authentication protocol specified in this
 document are likely to evolve in response to the particular security
 and privacy needs of its users.  While, in general, the association
 between particular half-sessions of the authentication protocol and
 the described triplets of functions is specific to an implementation
 and beyond the scope of this document, the desire for immediate
 interoperability among initial implementations of this protocol is
 best served by the temporary adoption of a common authentication
 scheme.  Accordingly, initial implementations will associate with
 every possible half-session a triplet of functions that realizes a
 trivial authentication mechanism:
 (1)  The authentication function is defined to have the value
      TRUE over the entire domain of authentication protocol
      messages.
 (2)  The message interpretation function is defined to be the
      identity function.
 (3)  The message representation function is defined to be the
      identity function.
 Because this initial posture with respect to authentication is not
 likely to remain acceptable indefinitely, implementors are urged to
 adopt designs that isolate authentication mechanism as much as
 possible from other components of the implementation.

13. Appendix 5: Routing Information Propagation Variables

 This section describes a set of related variables that characterize
 the sources and destinations of routing information propagated by
 various routing protocols. These variables have meaning only for
 those routing protocol implementations that afford greater
 flexibility in propagating routing information than is required by
 the various routing protocol specifications.
 Each IP interface afforded by the configuration of the gateway over
 which routing information may propagate via a routing protocol

Davin, Case, Fedor and Schoffstall [Page 23] RFC 1028 Simple Gateway Monitoring November 1987

 (target interface) is named by a string of four octets that literally
 represents the IP address associated with said protocol interface.
 Each IP protocol interface afforded by the configuration of the
 gateway over which routing information may arrive via any routing
 protocol (source interface) is named by a string of four octets that
 literally represents the IP address associated with said protocol
 interface.
 Each routing protocol by which a gateway receives information that it
 uses to route IP traffic (source routing protocol) is named by a
 single-octet string according to the conventions set forth in
 Appendix 6 of this document.
 Each routing protocol by which a gateway propagates routing
 information used by other hosts or gateways to route IP traffic
 (target routing protocol) is named by a single-octet string according
 to the conventions set forth in Appendix 6 of this document.
 A variable such that the initial portion of its name is the
 concatenation of:
 (1)  the octet string represented symbolically as "_GW_pr_in_rif"
      and numerically as 01 04 01 04 followed by:
 (2)  the name of a target routing protocol followed by
 (3)  the name of a target interface followed by
 (4)  the name of a source routing protocol followed by
 (5)  the name of a source interface
 has an integer value that characterizes the propagation of routing
 information between the sources and destinations of such information
 that are identified by the initial portion of that variable's name. A
 non-zero value for such a variable indicates that routing information
 received via the source routing protocol named by the fourth
 component of the variable name on the source interface named by its
 fifth component is propagated via the target routing protocol named
 by the second component of the variable name over the target
 interface named by its third component.  A zero value for such a
 variable indicates that routing information received via the source
 routing protocol on the source interface identified in the variable
 name is NOT propagated via the target routing protocol over the
 target interface identified in the variable name.

Davin, Case, Fedor and Schoffstall [Page 24] RFC 1028 Simple Gateway Monitoring November 1987

14. Appendix 6: Routing Protocol Representation

Numeric representations for routing protocols are presented below.

                      Value   Routing Protocol
                      ========================
                      0       None -- Reserved
                      1       Berkeley RIP Version 1
                      2       EGP
                      3       GGP
                      4       Hello
                      5       Other IGRP

15. Appendix 7: Proteon p4200 Release 7.4 Variables

 This section describes implementation-specific variables presented by
 the implementation of this protocol in Software Release 7.4 for the
 Proteon p4200 Internet Router.  These variable definitions are
 subject to change without notice.

15.1. The Network Interface Variables

 This section describes a related set of variables that represent
 attributes of a network interface in the Proteon p4200 Internet
 Router gateway.  Each such network interface is uniquely named by an
 implementation-specific octet string of length 1.

15.1.1. The Generic Network Interface Variables

 This section describes a related set of variables that represent
 attributes common to all network interfaces in the Proteon p4200
 Internet Router gateway.  Each generic network interface of a p4200
 configuration is uniquely named by the concatenation of the octet
 string represented symbolically as "_GW_impl_Proteon_p4200-R7.4_net-
 if" and numerically as:
              01 FF 01 01 01
 followed by the name of said network interface as described above.

15.1.1.1. The Generic _ovfl-in Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a generic network interface followed by
 the octet string represented symbolically as "_ovfl-in" and
 numerically as 01, has an integer value that represents the number of
 input packets dropped due to gateway congestion for the network
 interface identified by the initial portion of its name.

Davin, Case, Fedor and Schoffstall [Page 25] RFC 1028 Simple Gateway Monitoring November 1987

15.1.1.2. The Generic _ovfl-out Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a generic network interface followed by
 the octet string represented symbolically as "_ovfl-out" and
 numerically as 02, has an integer value that represents the number of
 output packets dropped due to gateway congestion for the network
 interface identified by the initial portion of its name.

15.1.1.3. The Generic _slftst-pass Variable Class A variable

 such that the initial portion of its name is the concatenation of the
 name for a generic network interface followed by the octet string
 represented symbolically as "_slftst-pass" and numerically as 03, has
 an integer value that represents the number of times the interface
 self-test procedure succeeded for the network interface identified by
 the initial portion of its name.

15.1.1.4. The Generic _slftst-fail Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a generic network interface followed by
 the octet string represented symbolically as "_slftst-fail" and
 numerically as 04, has an integer value that represents the number of
 times the interface self-test procedure failed for the network
 interface identified by the initial portion of its name.

15.1.1.5. The Generic _maint-fail Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a generic network interface followed by
 the octet string represented symbolically as "_maint-fail" and
 numerically as 06, has an integer value that represents the number of
 times the network maintenance procedure failed for the network
 interface identified by the initial portion of its name.

15.1.1.6. The Generic _csr Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a generic network interface followed by
 the octet string represented symbolically as "_csr" and numerically
 as 07, has an integer value that represents the internal address of
 the device CSR for the network interface identified by the initial
 portion of its name.

15.1.1.7. The Generic _vec Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a generic network interface followed by
 the octet string represented symbolically as "_vec" and numerically

Davin, Case, Fedor and Schoffstall [Page 26] RFC 1028 Simple Gateway Monitoring November 1987

 as 08, has an integer value that identifies the device interrupt
 vector used by the network interface identified by the initial
 portion of its name.

15.1.2. The ProNET Network Interface Variables

 This section describes a related set of variables that represent
 attributes of a ProNET type network interface in the Proteon p4200
 Internet Router gateway.  Each network interface of a p4200
 configuration that supports ProNET media is uniquely named by the
 concatenation of the octet string represented symbolically as
 "_GW_impl_Proteon_p4200-R7.4_devpn" and numerically as:
               01 FF 01 01 04
 followed by the name of said network interface as described above.

15.1.2.1. The ProNET _node-number Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a ProNET type network interface
 followed by the octet string represented symbolically as "_node-
 number" and numerically as 01, has an integer value that represents
 the ProNET node number associated with the network interface
 identified by the initial portion of its name.

15.1.2.2. The ProNET _in-data-present Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a ProNET type network interface
 followed by the octet string represented symbolically as "_in-data-
 present" and numerically as 02, has an integer value that represents
 the number of times that unread data was present in the input packet
 buffer for the network interface dentified by the initial portion of
 its name.

15.1.2.3. The ProNET _in-overrun Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a ProNET type network interface
 followed by the octet string represented symbolically as "_in-
 overrun" and numerically as 03, has an integer value that represents
 the number of times that a packet copied from the ring exceeded the
 size of the packet input buffer on the network interface identified
 by the initial portion of its name.

Davin, Case, Fedor and Schoffstall [Page 27] RFC 1028 Simple Gateway Monitoring November 1987

15.1.2.4. The ProNET _in-odd-byte-cnt Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a ProNET type network interface
 followed by the octet string represented symbolically as "_in-odd-
 byte-cnt" and numerically as 04, has an integer value that represents
 the number of times that a packet was received with an odd number of
 bytes on the network interface identified by the initial portion of
 its name.

15.1.2.5. The ProNET _in-parity-error Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a ProNET type network interface
 followed by the octet string represented symbolically as "_in-
 parity-error" and numerically as 05, has an integer value that
 represents the number of times that a parity error was detected in a
 packet copied from the ring on the network interface identified by
 the initial portion of its name.

15.1.2.6. The ProNET _in-bad-format Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a ProNET type network interface
 followed by the octet string represented symbolically as "_in-bad-
 format" and numerically as 06, has an integer value that represents
 the number of times that a format error was detected in a packet
 copied from the ring on the network interface identified by the
 initial portion of its name.

15.1.2.7. The ProNET _not-in-ring Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a ProNET type network interface
 followed by the octet string represented symbolically as "_not-in-
 ring" and numerically as 07, has an integer value that represents the
 number of times that the ProNET wire center relays were detected in
 an unenergized state for the network interface identified by the
 initial portion of its name.

15.1.2.8. The ProNET _out-ring-inits Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a ProNET type network interface
 followed by the octet string represented symbolically as "_out-ring-
 inits" and numerically as 08, has an integer value that represents
 the number of times that ring initialization has been attempted on
 the network interface identified by the initial portion of its name.

Davin, Case, Fedor and Schoffstall [Page 28] RFC 1028 Simple Gateway Monitoring November 1987

15.1.2.9. The ProNET _out-bad-format Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a ProNET type network interface
 followed by the octet string represented symbolically as "_out-bad-
 format" and numerically as 09, has an integer value that represents
 the number of times that an improperly formatted packet was detected
 in the course of an output operation on the network interface
 identified by the initial portion of its name.

15.1.2.10. The ProNET _out-timeout Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a ProNET type network interface
 followed by the octet string represented symbolically as "_out-
 timeout" and numerically as 0A, has an integer value that represents
 the number of times that an attempt to originate a message has been
 delayed by more than 700 ms on the network interface identified by
 the initial portion of its name.

15.1.3. The Ethernet Network Interface Variables

 This section describes a related set of variables that represent
 attributes of an Ethernet type network interface in the Proteon p4200
 Internet Router gateway.  Each network interface of a p4200
 configuration that supports Ethernet media is uniquely named by the
 concatenation of the octet string represented symbolically as
 "_GW_impl_Proteon_p4200-R7.4_dev-ie" and numerically as:
               01 FF 01 01 03
 followed by the name of said network interface as described above.

15.1.3.1. The Ethernet _phys-addr Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for an Ethernet type network interface
 followed by the octet string represented symbolically as "_phys-addr"
 and numerically as 01 has an octet string value that literally
 represents the Ethernet station address associated with the network
 interface identified by the initial portion of its name.

15.1.3.2. The Ethernet _input-ovfl Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for an Ethernet type network interface
 followed by the octet string represented symbolically as "_input-
 ovfl" and numerically as 02, has an integer value that represents the

Davin, Case, Fedor and Schoffstall [Page 29] RFC 1028 Simple Gateway Monitoring November 1987

 number of times the size of a received frame exceeded the maximum
 allowable for the network interface identified by the initial portion
 of its name.

15.1.3.3. The Ethernet _input-dropped Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for an Ethernet type network interface
 followed by the octet string represented0 symbolically as "_input-
 dropped" and numerically as 03, has an integer value that represents
 the number of times the loss of one or more frames was detected on
 the network interface identified by the initial portion of its name.

15.1.3.4. The Ethernet _output-retry Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for an Ethernet type network interface
 followed by the octet string represented symbolically as "_output-
 retry" and numerically as 04, has an integer value that represents
 the number of output operations retried as the result of a
 transmission failure on the network interface identified by the
 initial portion of its name.

15.1.3.5. The Ethernet _output-fail Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for an Ethernet type network interface
 followed by the octet string represented symbolically as "_output-
 fail" and numerically as 05, has an integer value that represents the
 number of failed output operations detected on the network interface
 identified by the initial portion of its name.

15.1.3.6. The Ethernet _excess-coll Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for an Ethernet type network interface
 followed by the octet string represented symbolically as "_excess-
 coll" and numerically as 06, has an integer value that represents the
 number of times a transmit frame incurred 16 successive collisions
 when attempting media access via the network interface identified by
 the initial portion of its name.

15.1.3.7. The Ethernet _frag-rcvd Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for an Ethernet type network interface
 followed by the octet string represented symbolically as "_frag-rcvd"
 and numerically as 07, has an integer value that represents the

Davin, Case, Fedor and Schoffstall [Page 30] RFC 1028 Simple Gateway Monitoring November 1987

 number of collision fragments (i.e., "runt packets") that were
 received and filtered by the controller for the network interface
 identified by the initial portion of its name.

15.1.3.8. The Ethernet _frames-lost Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for an Ethernet type network interface
 followed by the octet string represented symbolically as "_frames-
 lost" and numerically as 08, has an integer value that represents the
 number of frames not accepted by the Receive FIFO due to insufficient
 space for the network interface identified by the initial portion of
 its name.

15.1.3.9. The Ethernet _multicst-accept Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for an Ethernet type network interface
 followed by the octet string represented symbolically as "_multicst-
 accept" and numerically as 09, has an integer value that represents
 the number of frames received with a multicast-group destination
 address that matches one of those assigned to the controller for the
 network interface identified by the initial portion of said variable
 name.

15.1.3.10. The Ethernet _multicst-reject Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for an Ethernet type network interface
 followed by the octet string represented symbolically as "_multicst-
 reject" and numerically as 0A, has an integer value that represents
 the number of frames detected as having a multicast-group destination
 address that matches none of those assigned to the controller for the
 network interface identified by the initial portion of said variable
 name.

15.1.3.11. The Ethernet _crc-error Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for an Ethernet type network interface
 followed by the octet string represented symbolically as "_crc-error"
 and numerically as 0B, has an integer value that represents the
 number of frames received with a CRC error on the network interface
 identified by the initial portion of its name.

15.1.3.12. The Ethernet _alignmnt-error Variable Class

 A variable such that the initial portion of its name is the

Davin, Case, Fedor and Schoffstall [Page 31] RFC 1028 Simple Gateway Monitoring November 1987

 concatenation of the name for an Ethernet type network interface
 followed by the octet string represented symbolically as "_alignmnt-
 error" and numerically as 0C, has an integer value that represents
 the number of frames received with an alignment error on the network
 interface identified by the initial portion of its name.  A received
 frame is said to have an alignment error if its received length is
 not an integral multiple of 8 bits.

15.1.3.13. The Ethernet _collisions Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for an Ethernet type network interface
 followed by the octet string represented symbolically as
 "_collisions" and numerically as 0D, has an integer value that
 represents the number of collisions incurred during transmissions on
 the network interface identified by the initial portion of its name.

15.1.3.14. The Ethernet _out-of-window-coll Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for an Ethernet type network interface
 followed by the octet string represented symbolically as "_out-of-
 window-coll" and numerically as 0E, has an integer value that
 represents the number of out-ofwindow collisions incurred during
 transmissions on the network interface identified by the initial
 portion of its name.  Outof-window collisions are those occurring
 after the first 51.2 microseconds of slot time.

15.1.4. The Serial Network Interface Variables

 This section describes a related set of variables that represent
 attributes of an serial line type network interface in the Proteon
 p4200 Internet Router gateway.  Each network interface of a p4200
 configuration that supports serial communications is uniquely named
 by the concatenation of the octet string represented symbolically as
 "_GW_impl_Proteon_p4200-R7.4_dev-sl" and numerically as:
               01 FF 01 01 05
 followed by the name of said network interface as described above.

15.1.4.1. The Serial _tx-pkts Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a serial line type network interface
 followed by the octet string represented symbolically as "_tx-pkts"
 and numerically as 01, has an integer value that represents the
 number of packets transmitted on the network interface identified by

Davin, Case, Fedor and Schoffstall [Page 32] RFC 1028 Simple Gateway Monitoring November 1987

 the initial portion of its name.

15.1.4.2. The Serial _tx-framing-error Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a serial line type network interface
 followed by the octet string represented symbolically as "_tx-
 framing-error" and numerically as 02, has an integer value that
 represents the number of transmission framing errors for the network
 interface identified by the initial portion of its name.

15.1.4.3. The Serial _tx-underrns Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a serial line type network interface
 followed by the octet string represented symbolically as "_tx-
 underrns" and numerically as 03, has an integer value that represents
 the number of transmission underrun errors for the network interface
 identified by the initial portion of its name.

15.1.4.4. The Serial _tx-no-dcd Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a serial line type network interface
 followed by the octet string represented symbolically as "_tx-no-dcd"
 and numerically as 04, has an integer value that represents the
 number of times transmission failed due to absence of the EIA Data
 Carrier Detect signal on the network interface identified by the
 initial portion of its name.

15.1.4.5. The Serial _tx-no-cts Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a serial line type network interface
 followed by the octet string represented symbolically as "_tx-no-cts"
 and numerically as 05, has an integer value that represents the
 number of times transmission failed due to absence of the EIA Clear
 To Send signal on the network interface identified by the initial
 portion of its name.

15.1.4.6. The Serial _tx-no-dsr Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a serial line type network interface
 followed by the octet string represented symbolically as "_tx-no-dsr"
 and numerically as 06, has an integer value that represents the
 number of times transmission failed due to absence of the EIA Data
 Set Ready signal on the network interface identified by the initial

Davin, Case, Fedor and Schoffstall [Page 33] RFC 1028 Simple Gateway Monitoring November 1987

 portion of its name.

15.1.4.7. The Serial _rx-pkts Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a serial line type network interface
 followed by the octet string represented symbolically as "_rx-pkts"
 and numerically as 07, has an integer value that represents the
 number of packets received on the network interface identified by the
 initial portion of its name.

15.1.4.8. The Serial _rx-framing-err Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a serial line type network interface
 followed by the octet string represented symbolically as "_rx-
 framing-err" and numerically as 08, has an integer value that
 represents the number of receive framing errors on the network
 interface identified by the initial portion of its name.

15.1.4.9. The Serial _rx-overrns Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a serial line type network interface
 followed by the octet string represented symbolically as "_rx-
 overrns" and numerically as 09, has an integer value that represents
 the number of receive overrun errors on the network interface
 identified by the initial portion of its name.

15.1.4.10. The Serial _rx-aborts Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a serial line type network interface
 followed by the octet string represented symbolically as "_rx-aborts"
 and numerically as 0A, has an integer value that represents the
 number of aborted frames received on the network interface identified
 by the initial portion of its name.

15.1.4.11. The Serial _rx-crc-err Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a serial line type network interface
 followed by the octet string represented symbolically as "_rx-crc-
 err" and numerically as 0B, has an integer value that represents the
 number of frames received with CRC errors on the network interface
 identified by the initial portion of its name.

Davin, Case, Fedor and Schoffstall [Page 34] RFC 1028 Simple Gateway Monitoring November 1987

15.1.4.12. The Serial _rx-buf-ovfl Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a serial line type network interface
 followed by the octet string represented symbolically as "_rx-buf-
 ovfl" and numerically as 0C, has an integer value that represents the
 number of received frames whose size exceeded the maximum allowable
 on the network interface identified by the initial portion of its
 name.

15.1.4.13. The Serial _rx-buf-locked Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a serial line type network interface
 followed by the octet string represented symbolically as "_rx-buf-
 locked" and numerically as 0D, has an integer value that represents
 the number of received frames lost for lack of an available buffer on
 the network interface identified by the initial portion of its name.

15.1.4.14. The Serial _rx-line-speed Variable Class

 A variable such that the initial portion of its name is the
 concatenation of the name for a serial line type network interface
 followed by the octet string represented symbolically as "_rx-line-
 speed" and numerically as 0E, has an integer value that represents an
 estimate of serial line bandwidth in bits per second for the network
 interface identified by the initial portion of its name.

Davin, Case, Fedor and Schoffstall [Page 35]

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