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Network Working Group E. Decker Request for Comments: 1493 cisco Systems, Inc. Obsoletes: 1286 P. Langille Digital Equipment Corporation A. Rijsinghani Digital Equipment Corporation K. McCloghrie Hughes LAN Systems, Inc. July 1993 Definitions of Managed Objects for Bridges Status of this Memo This RFC specifies an IAB standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "IAB Official Protocol Standards" for the standardization state and status of this protocol. Distribution of this memo is unlimited. Abstract This memo defines a portion of the Management Information Base (MIB) for use with network management protocols in TCP/IP based internets. In particular it defines objects for managing MAC bridges based on the IEEE 802.1D-1990 standard between Local Area Network (LAN) segments. Provisions are made for support of transparent bridging. Provisions are also made so that these objects apply to bridges connected by subnetworks other than LAN segments. Table of Contents 1. The Network Management Framework ...................... 2 2. Objects ............................................... 2 2.1 Format of Definitions ................................ 3 3. Overview .............................................. 3 3.1 Structure of MIB ..................................... 3 3.1.1 The dot1dBase Group ................................ 6 3.1.2 The dot1dStp Group ................................. 6 3.1.3 The dot1dSr Group .................................. 6 3.1.4 The dot1dTp Group .................................. 6 3.1.5 The dot1dStatic Group .............................. 6 3.2 Relationship to Other MIBs ........................... 6 3.2.1 Relationship to the 'system' group ................. 6 3.2.2 Relationship to the 'interfaces' group ............. 7 Decker, Langille, Rijsinghani & McCloghrie [Page 1] RFC 1493 Bridge MIB July 1993 3.3 Textual Conventions .................................. 8 4. Changes from RFC 1286 ................................. 8 5. Definitions ........................................... 9 5.1 Groups in the Bridge MIB ............................. 11 5.2 The dot1dBase Group Definitions ...................... 11 5.3 The dot1dStp Group Definitions ....................... 14 5.4 The dot1dTp Group Definitions ........................ 22 5.5 The dot1dStatic Group Definitions .................... 28 5.6 Traps for use by Bridges ............................. 31 6. Acknowledgments ....................................... 31 7. References ............................................ 33 8. Security Considerations ............................... 33 9. Authors' Addresses .................................... 34 1. The Network Management Framework The Internet-standard Network Management Framework consists of three components. They are: STD16/RFC 1155 which defines the SMI, the mechanisms used for describing and naming objects for the purpose of management. STD16/RFC 1212 defines a more concise description mechanism, which is wholly consistent with the SMI. RFC 1156 which defines MIB-I, the core set of managed objects for the Internet suite of protocols. STD17/RFC 1213, defines MIB-II, an evolution of MIB-I based on implementation experience and new operational requirements. STD15/RFC 1157 which defines the SNMP, the protocol used for network access to managed objects. The Framework permits new objects to be defined for the purpose of experimentation and evaluation. 2. Objects Managed objects are accessed via a virtual information store, termed the Management Information Base or MIB. Objects in the MIB are defined using the subset of Abstract Syntax Notation One (ASN.1) [7] defined in the SMI. In particular, each object is named by an OBJECT IDENTIFIER, an administratively assigned name, which specifies an object type. The object type together with an object instance serves to uniquely identify a specific instantiation of the object. For human convenience, we often use a textual string, termed the descriptor, to also refer to the object type. Decker, Langille, Rijsinghani & McCloghrie [Page 2] RFC 1493 Bridge MIB July 1993 2.1. Format of Definitions Section 5 contains the specification of all object types contained in this MIB module. The object types are defined using the conventions defined in the SMI, as amended by the extensions specified in [9,10]. 3. Overview A common device present in many networks is the Bridge. This device is used to connect Local Area Network segments below the network layer. There are two major modes defined for this bridging; transparent and source route. The transparent method of bridging is defined in the draft IEEE 802.1d specification [11]. This memo defines those objects needed for the management of a bridging entity operating in the transparent mode, as well as some objects applicable to all types of bridges. To be consistent with IAB directives and good engineering practice, an explicit attempt was made to keep this MIB as simple as possible. This was accomplished by applying the following criteria to objects proposed for inclusion: (1) Start with a small set of essential objects and add only as further objects are needed. (2) Require objects be essential for either fault or configuration management. (3) Consider evidence of current use and/or utility. (4) Limit the total of objects. (5) Exclude objects which are simply derivable from others in this or other MIBs. (6) Avoid causing critical sections to be heavily instrumented. The guideline that was followed is one counter per critical section per layer. 3.1. Structure of MIB Objects in this MIB are arranged into groups. Each group is organized as a set of related objects. The overall structure and assignment of objects to their groups is shown below. Where appropriate the corresponding IEEE 802.1d [11] management object name is also included. Decker, Langille, Rijsinghani & McCloghrie [Page 3] RFC 1493 Bridge MIB July 1993 Bridge MIB Name IEEE 802.1d Name dot1dBridge dot1dBase BridgeAddress Bridge.BridgeAddress NumPorts Bridge.NumberOfPorts Type PortTable Port BridgePort.PortNumber IfIndex Circuit DelayExceededDiscards .DiscardTransitDelay MtuExceededDiscards .DiscardOnError dot1dStp ProtocolSpecification Priority SpanningTreeProtocol .BridgePriority TimeSinceTopologyChange .TimeSinceTopologyChange TopChanges .TopologyChangeCount DesignatedRoot .DesignatedRoot RootCost .RootCost RootPort .RootPort MaxAge .MaxAge HelloTime .HelloTime HoldTime .HoldTime ForwardDelay .ForwardDelay BridgeMaxAge .BridgeMaxAge BridgeHelloTime .BridgeHelloTime BridgeForwardDelay .BridgeForwardDelay PortTable Port SpanningTreeProtocolPort .PortNumber Priority .PortPriority State .SpanningTreeState Enable PathCost .PortPathCost DesignatedRoot .DesignatedRoot DesignatedCost .DesignatedCost DesignatedBridge .DesignatedBridge DesignatedPort .DesignatedPort ForwardTransitions dot1dTp LearnedEntryDiscards BridgeFilter.DatabaseSize .NumDynamic,NumStatic AgingTime BridgeFilter.AgingTime FdbTable Address Port Decker, Langille, Rijsinghani & McCloghrie [Page 4] RFC 1493 Bridge MIB July 1993 Status PortTable Port MaxInfo InFrames BridgePort.FramesReceived OutFrames .ForwardOutbound InDiscards .DiscardInbound dot1dStatic StaticTable Address ReceivePort AllowedToGoTo Status The following IEEE 802.1d management objects have not been included in the Bridge MIB for the indicated reasons. IEEE 802.1d Object Disposition Bridge.BridgeName Same as sysDescr (MIB II) Bridge.BridgeUpTime Same as sysUpTime (MIB II) Bridge.PortAddresses Same as ifPhysAddress (MIB II) BridgePort.PortName Same as ifDescr (MIB II) BridgePort.PortType Same as ifType (MIB II) BridgePort.RoutingType Derivable from the implemented groups SpanningTreeProtocol .BridgeIdentifier Combination of dot1dStpPriority and dot1dBaseBridgeAddress .TopologyChange Since this is transitory, it is not considered useful. SpanningTreeProtocolPort .Uptime Same as ifLastChange (MIB II) .PortIdentifier Combination of dot1dStpPort and dot1dStpPortPriority .TopologyChangeAcknowledged Since this is transitory, it is not considered useful. .DiscardLackOfBuffers Redundant Transmission Priority These objects are not required as per the Pics Proforma and not considered useful. .TransmissionPriorityName .OutboundUserPriority .OutboundAccessPriority Decker, Langille, Rijsinghani & McCloghrie [Page 5] RFC 1493 Bridge MIB July 1993 3.1.1. The dot1dBase Group This mandatory group contains the objects which are applicable to all types of bridges. 3.1.2. The dot1dStp Group This group contains the objects that denote the bridge's state with respect to the Spanning Tree Protocol. If a node does not implemented the Spanning Tree Protocol, this group will not be implemented. 3.1.3. The dot1dSr Group This group contains the objects that describe the entity's state with respect to source route bridging. If source routing is not supported this group will not be implemented. This group is applicable to source route only, and SRT bridges. This group will be described in a separate document applicable only to source route bridging. 3.1.4. The dot1dTp Group This group contains objects that describe the entity's state with respect to transparent bridging. If transparent bridging is not supported this group will not be implemented. This group is applicable to transparent only and SRT bridges. 3.1.5. The dot1dStatic Group This group contains objects that describe the entity's state with respect to destination-address filtering. If destination-address filtering is not supported this group will not be implemented. This group is applicable to any type of bridge which performs destination-address filtering. 3.2. Relationship to Other MIBs As described above, some IEEE 802.1d management objects have not been included in this MIB because they overlap with objects in other MIBs applicable to a bridge implementing this MIB. In particular, it is assumed that a bridge implementing this MIB will also implement (at least) the 'system' group and the 'interfaces' group defined in MIB- II [6]. 3.2.1. Relationship to the 'system' group In MIB-II, the 'system' group is defined as being mandatory for all systems such that each managed entity contains one instance of each Decker, Langille, Rijsinghani & McCloghrie [Page 6] RFC 1493 Bridge MIB July 1993 object in the 'system' group. Thus, those objects apply to the entity as a whole irrespective of whether the entity's sole functionality is bridging, or whether bridging is only a subset of the entity's functionality. 3.2.2. Relationship to the 'interfaces' group In MIB-II, the 'interfaces' group is defined as being mandatory for all systems and contains information on an entity's interfaces, where each interface is thought of as being attached to a `subnetwork'. (Note that this term is not to be confused with `subnet' which refers to an addressing partitioning scheme used in the Internet suite of protocols.) The term 'segment' is used in this memo to refer to such a subnetwork, whether it be an Ethernet segment, a 'ring', a WAN link, or even an X.25 virtual circuit. Implicit in this Bridge MIB is the notion of ports on a bridge. Each of these ports is associated with one interface of the 'interfaces' group, and in most situations, each port is associated with a different interface. However, there are situations in which multiple ports are associated with the same interface. An example of such a situation would be several ports each corresponding one-to-one with several X.25 virtual circuits but all on the same interface. Each port is uniquely identified by a port number. A port number has no mandatory relationship to an interface number, but in the simple case a port number will have the same value as the corresponding interface's interface number. Port numbers are in the range (1..dot1dBaseNumPorts). Some entities perform other functionality as well as bridging through the sending and receiving of data on their interfaces. In such situations, only a subset of the data sent/received on an interface is within the domain of the entity's bridging functionality. This subset is considered to be delineated according to a set of protocols, with some protocols being bridged, and other protocols not being bridged. For example, in an entity which exclusively performed bridging, all protocols would be considered as being bridged, whereas in an entity which performed IP routing on IP datagrams and only bridged other protocols, only the non-IP data would be considered as being bridged. Thus, this Bridge MIB (and in particular, its counters) are applicable only to that subset of the data on an entity's interfaces which is sent/received for a protocol being bridged. All such data is sent/received via the ports of the bridge. Decker, Langille, Rijsinghani & McCloghrie [Page 7] RFC 1493 Bridge MIB July 1993 3.3. Textual Conventions The datatypes, MacAddress, BridgeId and Timeout, are used as textual conventions in this document. These textual conventions have NO effect on either the syntax nor the semantics of any managed object. Objects defined using these conventions are always encoded by means of the rules that define their primitive type. Hence, no changes to the SMI or the SNMP are necessary to accommodate these textual conventions which are adopted merely for the convenience of readers. 4. Changes from RFC 1286 (1) Updated all text to remove references to source route bridging where not applicable. SR MIB will be a separate document. (2) Removed dot1dSrPortTable. Retained OID definition of dot1dSr. (3) Updated all references of "draft P802.1d/D9" to "IEEE 802.1D-1990". (4) Updated bibliography. (5) Added clarification to description of dot1dPortPathCost. (6) Put recommended default in description of dot1dStaticAllowedToGoTo. (7) Put recommended default in description of dot1dStaticStatus. (8) Put recommended default in description of dot1dTpAgingTime. Specified range of (10..1000000). (9) Updated all port number syntaxes, when used as index, to use the range (1..65535). (10) Updated definition of dot1dTpPortInFrames and dot1dTpPortOutFrames. (11) Added text to the traps indicating that they are optional. (12) Clarified definition of dot1dStpForwardDelay. Decker, Langille, Rijsinghani & McCloghrie [Page 8] RFC 1493 Bridge MIB July 1993 5. Definitions BRIDGE-MIB DEFINITIONS ::= BEGIN IMPORTS Counter, TimeTicks FROM RFC1155-SMI mib-2 FROM RFC1213-MIB OBJECT-TYPE FROM RFC-1212 TRAP-TYPE FROM RFC-1215; -- All representations of MAC addresses in this MIB Module -- use, as a textual convention (i.e. this convention does -- not affect their encoding), the data type: MacAddress ::= OCTET STRING (SIZE (6)) -- a 6 octet address -- in the -- "canonical" -- order -- defined by IEEE 802.1a, i.e., as if it were transmitted -- least significant bit first, even though 802.5 (in -- contrast to other n802.x protocols) requires MAC -- addresses to be transmitted most significant bit first. -- -- 16-bit addresses, if needed, are represented by setting -- their upper 4 octets to all 0's, i.e., AAFF would be -- represented as 00000000AAFF. -- Similarly, all representations of Bridge-Id in this MIB -- Module use, as a textual convention (i.e. this -- convention does not affect their encoding), the data -- type: BridgeId ::= OCTET STRING (SIZE (8)) -- the -- Bridge-Identifier -- as used in the -- Spanning Tree -- Protocol to uniquely identify a bridge. Its first two -- octets (in network byte order) contain a priority -- value and its last 6 octets contain the MAC address -- used to refer to a bridge in a unique fashion -- (typically, the numerically smallest MAC address -- of all ports on the bridge). Decker, Langille, Rijsinghani & McCloghrie [Page 9] RFC 1493 Bridge MIB July 1993 -- Several objects in this MIB module represent values of -- timers used by the Spanning Tree Protocol. In this -- MIB, these timers have values in units of hundreths of -- a second (i.e. 1/100 secs). -- These timers, when stored in a Spanning Tree Protocol's -- BPDU, are in units of 1/256 seconds. Note, however, -- that 802.1D-1990 specifies a settable granularity of -- no more than 1 second for these timers. To avoid -- ambiguity, a data type is defined here as a textual -- convention and all representation of these timers -- in this MIB module are defined using this data type. An -- algorithm is also defined for converting between the -- different units, to ensure a timer's value is not -- distorted by multiple conversions. -- The data type is: Timeout ::= INTEGER -- a STP timer in units of 1/100 seconds -- To convert a Timeout value into a value in units of -- 1/256 seconds, the following algorithm should be used: -- -- b = floor( (n * 256) / 100) -- -- where: -- floor = quotient [ignore remainder] -- n is the value in 1/100 second units -- b is the value in 1/256 second units -- -- To convert the value from 1/256 second units back to -- 1/100 seconds, the following algorithm should be used: -- -- n = ceiling( (b * 100) / 256) -- -- where: -- ceiling = quotient [if remainder is 0], or -- quotient + 1 [if remainder is non-zero] -- n is the value in 1/100 second units -- b is the value in 1/256 second units -- -- Note: it is important that the arithmetic operations are -- done in the order specified (i.e., multiply first, divide -- second). dot1dBridge OBJECT IDENTIFIER ::= { mib-2 17 } Decker, Langille, Rijsinghani & McCloghrie [Page 10] RFC 1493 Bridge MIB July 1993 -- groups in the Bridge MIB dot1dBase OBJECT IDENTIFIER ::= { dot1dBridge 1 } dot1dStp OBJECT IDENTIFIER ::= { dot1dBridge 2 } dot1dSr OBJECT IDENTIFIER ::= { dot1dBridge 3 } -- separately documented dot1dTp OBJECT IDENTIFIER ::= { dot1dBridge 4 } dot1dStatic OBJECT IDENTIFIER ::= { dot1dBridge 5 } -- the dot1dBase group -- Implementation of the dot1dBase group is mandatory for all -- bridges. dot1dBaseBridgeAddress OBJECT-TYPE SYNTAX MacAddress ACCESS read-only STATUS mandatory DESCRIPTION "The MAC address used by this bridge when it must be referred to in a unique fashion. It is recommended that this be the numerically smallest MAC address of all ports that belong to this bridge. However it is only required to be unique. When concatenated with dot1dStpPriority a unique BridgeIdentifier is formed which is used in the Spanning Tree Protocol." REFERENCE "IEEE 802.1D-1990: Sections 6.4.1.1.3 and 3.12.5" ::= { dot1dBase 1 } dot1dBaseNumPorts OBJECT-TYPE SYNTAX INTEGER ACCESS read-only STATUS mandatory DESCRIPTION "The number of ports controlled by this bridging entity." REFERENCE "IEEE 802.1D-1990: Section 6.4.1.1.3" ::= { dot1dBase 2 } dot1dBaseType OBJECT-TYPE Decker, Langille, Rijsinghani & McCloghrie [Page 11] RFC 1493 Bridge MIB July 1993 SYNTAX INTEGER { unknown(1), transparent-only(2), sourceroute-only(3), srt(4) } ACCESS read-only STATUS mandatory DESCRIPTION "Indicates what type of bridging this bridge can perform. If a bridge is actually performing a certain type of bridging this will be indicated by entries in the port table for the given type." ::= { dot1dBase 3 } -- The Generic Bridge Port Table dot1dBasePortTable OBJECT-TYPE SYNTAX SEQUENCE OF Dot1dBasePortEntry ACCESS not-accessible STATUS mandatory DESCRIPTION "A table that contains generic information about every port that is associated with this bridge. Transparent, source-route, and srt ports are included." ::= { dot1dBase 4 } dot1dBasePortEntry OBJECT-TYPE SYNTAX Dot1dBasePortEntry ACCESS not-accessible STATUS mandatory DESCRIPTION "A list of information for each port of the bridge." REFERENCE "IEEE 802.1D-1990: Section 6.4.2, 6.6.1" INDEX { dot1dBasePort } ::= { dot1dBasePortTable 1 } Dot1dBasePortEntry ::= SEQUENCE { dot1dBasePort INTEGER, dot1dBasePortIfIndex INTEGER, dot1dBasePortCircuit Decker, Langille, Rijsinghani & McCloghrie [Page 12] RFC 1493 Bridge MIB July 1993 OBJECT IDENTIFIER, dot1dBasePortDelayExceededDiscards Counter, dot1dBasePortMtuExceededDiscards Counter } dot1dBasePort OBJECT-TYPE SYNTAX INTEGER (1..65535) ACCESS read-only STATUS mandatory DESCRIPTION "The port number of the port for which this entry contains bridge management information." ::= { dot1dBasePortEntry 1 } dot1dBasePortIfIndex OBJECT-TYPE SYNTAX INTEGER ACCESS read-only STATUS mandatory DESCRIPTION "The value of the instance of the ifIndex object, defined in MIB-II, for the interface corresponding to this port." ::= { dot1dBasePortEntry 2 } dot1dBasePortCircuit OBJECT-TYPE SYNTAX OBJECT IDENTIFIER ACCESS read-only STATUS mandatory DESCRIPTION "For a port which (potentially) has the same value of dot1dBasePortIfIndex as another port on the same bridge, this object contains the name of an object instance unique to this port. For example, in the case where multiple ports correspond one- to-one with multiple X.25 virtual circuits, this value might identify an (e.g., the first) object instance associated with the X.25 virtual circuit corresponding to this port. For a port which has a unique value of dot1dBasePortIfIndex, this object can have the value { 0 0 }." ::= { dot1dBasePortEntry 3 } dot1dBasePortDelayExceededDiscards OBJECT-TYPE SYNTAX Counter Decker, Langille, Rijsinghani & McCloghrie [Page 13] RFC 1493 Bridge MIB July 1993 ACCESS read-only STATUS mandatory DESCRIPTION "The number of frames discarded by this port due to excessive transit delay through the bridge. It is incremented by both transparent and source route bridges." REFERENCE "IEEE 802.1D-1990: Section 6.6.1.1.3" ::= { dot1dBasePortEntry 4 } dot1dBasePortMtuExceededDiscards OBJECT-TYPE SYNTAX Counter ACCESS read-only STATUS mandatory DESCRIPTION "The number of frames discarded by this port due to an excessive size. It is incremented by both transparent and source route bridges." REFERENCE "IEEE 802.1D-1990: Section 6.6.1.1.3" ::= { dot1dBasePortEntry 5 } -- the dot1dStp group -- Implementation of the dot1dStp group is optional. It is -- implemented by those bridges that support the Spanning Tree -- Protocol. dot1dStpProtocolSpecification OBJECT-TYPE SYNTAX INTEGER { unknown(1), decLb100(2), ieee8021d(3) } ACCESS read-only STATUS mandatory DESCRIPTION "An indication of what version of the Spanning Tree Protocol is being run. The value 'decLb100(2)' indicates the DEC LANbridge 100 Spanning Tree protocol. IEEE 802.1d implementations will return 'ieee8021d(3)'. If future versions of the IEEE Spanning Tree Protocol are released that are incompatible with the current version a new value will be defined." Decker, Langille, Rijsinghani & McCloghrie [Page 14] RFC 1493 Bridge MIB July 1993 ::= { dot1dStp 1 } dot1dStpPriority OBJECT-TYPE SYNTAX INTEGER (0..65535) ACCESS read-write STATUS mandatory DESCRIPTION "The value of the write-able portion of the Bridge ID, i.e., the first two octets of the (8 octet long) Bridge ID. The other (last) 6 octets of the Bridge ID are given by the value of dot1dBaseBridgeAddress." REFERENCE "IEEE 802.1D-1990: Section 4.5.3.7" ::= { dot1dStp 2 } dot1dStpTimeSinceTopologyChange OBJECT-TYPE SYNTAX TimeTicks ACCESS read-only STATUS mandatory DESCRIPTION "The time (in hundredths of a second) since the last time a topology change was detected by the bridge entity." REFERENCE "IEEE 802.1D-1990: Section 6.8.1.1.3" ::= { dot1dStp 3 } dot1dStpTopChanges OBJECT-TYPE SYNTAX Counter ACCESS read-only STATUS mandatory DESCRIPTION "The total number of topology changes detected by this bridge since the management entity was last reset or initialized." REFERENCE "IEEE 802.1D-1990: Section 6.8.1.1.3" ::= { dot1dStp 4 } dot1dStpDesignatedRoot OBJECT-TYPE SYNTAX BridgeId ACCESS read-only STATUS mandatory DESCRIPTION "The bridge identifier of the root of the spanning tree as determined by the Spanning Tree Protocol as executed by this node. This value is used as Decker, Langille, Rijsinghani & McCloghrie [Page 15] RFC 1493 Bridge MIB July 1993 the Root Identifier parameter in all Configuration Bridge PDUs originated by this node." REFERENCE "IEEE 802.1D-1990: Section 4.5.3.1" ::= { dot1dStp 5 } dot1dStpRootCost OBJECT-TYPE SYNTAX INTEGER ACCESS read-only STATUS mandatory DESCRIPTION "The cost of the path to the root as seen from this bridge." REFERENCE "IEEE 802.1D-1990: Section 4.5.3.2" ::= { dot1dStp 6 } dot1dStpRootPort OBJECT-TYPE SYNTAX INTEGER ACCESS read-only STATUS mandatory DESCRIPTION "The port number of the port which offers the lowest cost path from this bridge to the root bridge." REFERENCE "IEEE 802.1D-1990: Section 4.5.3.3" ::= { dot1dStp 7 } dot1dStpMaxAge OBJECT-TYPE SYNTAX Timeout ACCESS read-only STATUS mandatory DESCRIPTION "The maximum age of Spanning Tree Protocol information learned from the network on any port before it is discarded, in units of hundredths of a second. This is the actual value that this bridge is currently using." REFERENCE "IEEE 802.1D-1990: Section 4.5.3.4" ::= { dot1dStp 8 } dot1dStpHelloTime OBJECT-TYPE SYNTAX Timeout ACCESS read-only STATUS mandatory DESCRIPTION Decker, Langille, Rijsinghani & McCloghrie [Page 16] RFC 1493 Bridge MIB July 1993 "The amount of time between the transmission of Configuration bridge PDUs by this node on any port when it is the root of the spanning tree or trying to become so, in units of hundredths of a second. This is the actual value that this bridge is currently using." REFERENCE "IEEE 802.1D-1990: Section 4.5.3.5" ::= { dot1dStp 9 } dot1dStpHoldTime OBJECT-TYPE SYNTAX INTEGER ACCESS read-only STATUS mandatory DESCRIPTION "This time value determines the interval length during which no more than two Configuration bridge PDUs shall be transmitted by this node, in units of hundredths of a second." REFERENCE "IEEE 802.1D-1990: Section 4.5.3.14" ::= { dot1dStp 10 } dot1dStpForwardDelay OBJECT-TYPE SYNTAX Timeout ACCESS read-only STATUS mandatory DESCRIPTION "This time value, measured in units of hundredths of a second, controls how fast a port changes its spanning state when moving towards the Forwarding state. The value determines how long the port stays in each of the Listening and Learning states, which precede the Forwarding state. This value is also used, when a topology change has been detected and is underway, to age all dynamic entries in the Forwarding Database. [Note that this value is the one that this bridge is currently using, in contrast to dot1dStpBridgeForwardDelay which is the value that this bridge and all others would start using if/when this bridge were to become the root.]" REFERENCE "IEEE 802.1D-1990: Section 4.5.3.6" ::= { dot1dStp 11 } dot1dStpBridgeMaxAge OBJECT-TYPE SYNTAX Timeout (600..4000) Decker, Langille, Rijsinghani & McCloghrie [Page 17] RFC 1493 Bridge MIB July 1993 ACCESS read-write STATUS mandatory DESCRIPTION "The value that all bridges use for MaxAge when this bridge is acting as the root. Note that 802.1D-1990 specifies that the range for this parameter is related to the value of dot1dStpBridgeHelloTime. The granularity of this timer is specified by 802.1D-1990 to be 1 second. An agent may return a badValue error if a set is attempted to a value which is not a whole number of seconds." REFERENCE "IEEE 802.1D-1990: Section 4.5.3.8" ::= { dot1dStp 12 } dot1dStpBridgeHelloTime OBJECT-TYPE SYNTAX Timeout (100..1000) ACCESS read-write STATUS mandatory DESCRIPTION "The value that all bridges use for HelloTime when this bridge is acting as the root. The granularity of this timer is specified by 802.1D- 1990 to be 1 second. An agent may return a badValue error if a set is attempted to a value which is not a whole number of seconds." REFERENCE "IEEE 802.1D-1990: Section 4.5.3.9" ::= { dot1dStp 13 } dot1dStpBridgeForwardDelay OBJECT-TYPE SYNTAX Timeout (400..3000) ACCESS read-write STATUS mandatory DESCRIPTION "The value that all bridges use for ForwardDelay when this bridge is acting as the root. Note that 802.1D-1990 specifies that the range for this parameter is related to the value of dot1dStpBridgeMaxAge. The granularity of this timer is specified by 802.1D-1990 to be 1 second. An agent may return a badValue error if a set is attempted to a value which is not a whole number of seconds." REFERENCE "IEEE 802.1D-1990: Section 4.5.3.10" ::= { dot1dStp 14 } Decker, Langille, Rijsinghani & McCloghrie [Page 18] RFC 1493 Bridge MIB July 1993 -- The Spanning Tree Port Table dot1dStpPortTable OBJECT-TYPE SYNTAX SEQUENCE OF Dot1dStpPortEntry ACCESS not-accessible STATUS mandatory DESCRIPTION "A table that contains port-specific information for the Spanning Tree Protocol." ::= { dot1dStp 15 } dot1dStpPortEntry OBJECT-TYPE SYNTAX Dot1dStpPortEntry ACCESS not-accessible STATUS mandatory DESCRIPTION "A list of information maintained by every port about the Spanning Tree Protocol state for that port." INDEX { dot1dStpPort } ::= { dot1dStpPortTable 1 } Dot1dStpPortEntry ::= SEQUENCE { dot1dStpPort INTEGER, dot1dStpPortPriority INTEGER, dot1dStpPortState INTEGER, dot1dStpPortEnable INTEGER, dot1dStpPortPathCost INTEGER, dot1dStpPortDesignatedRoot BridgeId, dot1dStpPortDesignatedCost INTEGER, dot1dStpPortDesignatedBridge BridgeId, dot1dStpPortDesignatedPort OCTET STRING, dot1dStpPortForwardTransitions Counter } dot1dStpPort OBJECT-TYPE SYNTAX INTEGER (1..65535) Decker, Langille, Rijsinghani & McCloghrie [Page 19] RFC 1493 Bridge MIB July 1993 ACCESS read-only STATUS mandatory DESCRIPTION "The port number of the port for which this entry contains Spanning Tree Protocol management information." REFERENCE "IEEE 802.1D-1990: Section 6.8.2.1.2" ::= { dot1dStpPortEntry 1 } dot1dStpPortPriority OBJECT-TYPE SYNTAX INTEGER (0..255) ACCESS read-write STATUS mandatory DESCRIPTION "The value of the priority field which is contained in the first (in network byte order) octet of the (2 octet long) Port ID. The other octet of the Port ID is given by the value of dot1dStpPort." REFERENCE "IEEE 802.1D-1990: Section 4.5.5.1" ::= { dot1dStpPortEntry 2 } dot1dStpPortState OBJECT-TYPE SYNTAX INTEGER { disabled(1), blocking(2), listening(3), learning(4), forwarding(5), broken(6) } ACCESS read-only STATUS mandatory DESCRIPTION "The port's current state as defined by application of the Spanning Tree Protocol. This state controls what action a port takes on reception of a frame. If the bridge has detected a port that is malfunctioning it will place that port into the broken(6) state. For ports which are disabled (see dot1dStpPortEnable), this object will have a value of disabled(1)." REFERENCE "IEEE 802.1D-1990: Section 4.5.5.2" ::= { dot1dStpPortEntry 3 } Decker, Langille, Rijsinghani & McCloghrie [Page 20] RFC 1493 Bridge MIB July 1993 dot1dStpPortEnable OBJECT-TYPE SYNTAX INTEGER { enabled(1), disabled(2) } ACCESS read-write STATUS mandatory DESCRIPTION "The enabled/disabled status of the port." REFERENCE "IEEE 802.1D-1990: Section 4.5.5.2" ::= { dot1dStpPortEntry 4 } dot1dStpPortPathCost OBJECT-TYPE SYNTAX INTEGER (1..65535) ACCESS read-write STATUS mandatory DESCRIPTION "The contribution of this port to the path cost of paths towards the spanning tree root which include this port. 802.1D-1990 recommends that the default value of this parameter be in inverse proportion to the speed of the attached LAN." REFERENCE "IEEE 802.1D-1990: Section 4.5.5.3" ::= { dot1dStpPortEntry 5 } dot1dStpPortDesignatedRoot OBJECT-TYPE SYNTAX BridgeId ACCESS read-only STATUS mandatory DESCRIPTION "The unique Bridge Identifier of the Bridge recorded as the Root in the Configuration BPDUs transmitted by the Designated Bridge for the segment to which the port is attached." REFERENCE "IEEE 802.1D-1990: Section 4.5.5.4" ::= { dot1dStpPortEntry 6 } dot1dStpPortDesignatedCost OBJECT-TYPE SYNTAX INTEGER ACCESS read-only STATUS mandatory DESCRIPTION "The path cost of the Designated Port of the segment connected to this port. This value is compared to the Root Path Cost field in received Decker, Langille, Rijsinghani & McCloghrie [Page 21] RFC 1493 Bridge MIB July 1993 bridge PDUs." REFERENCE "IEEE 802.1D-1990: Section 4.5.5.5" ::= { dot1dStpPortEntry 7 } dot1dStpPortDesignatedBridge OBJECT-TYPE SYNTAX BridgeId ACCESS read-only STATUS mandatory DESCRIPTION "The Bridge Identifier of the bridge which this port considers to be the Designated Bridge for this port's segment." REFERENCE "IEEE 802.1D-1990: Section 4.5.5.6" ::= { dot1dStpPortEntry 8 } dot1dStpPortDesignatedPort OBJECT-TYPE SYNTAX OCTET STRING (SIZE (2)) ACCESS read-only STATUS mandatory DESCRIPTION "The Port Identifier of the port on the Designated Bridge for this port's segment." REFERENCE "IEEE 802.1D-1990: Section 4.5.5.7" ::= { dot1dStpPortEntry 9 } dot1dStpPortForwardTransitions OBJECT-TYPE SYNTAX Counter ACCESS read-only STATUS mandatory DESCRIPTION "The number of times this port has transitioned from the Learning state to the Forwarding state." ::= { dot1dStpPortEntry 10 } -- the dot1dTp group -- Implementation of the dot1dTp group is optional. It is -- implemented by those bridges that support the transparent -- bridging mode. A transparent or SRT bridge will implement -- this group. dot1dTpLearnedEntryDiscards OBJECT-TYPE SYNTAX Counter Decker, Langille, Rijsinghani & McCloghrie [Page 22] RFC 1493 Bridge MIB July 1993 ACCESS read-only STATUS mandatory DESCRIPTION "The total number of Forwarding Database entries, which have been or would have been learnt, but have been discarded due to a lack of space to store them in the Forwarding Database. If this counter is increasing, it indicates that the Forwarding Database is regularly becoming full (a condition which has unpleasant performance effects on the subnetwork). If this counter has a significant value but is not presently increasing, it indicates that the problem has been occurring but is not persistent." REFERENCE "IEEE 802.1D-1990: Section 6.7.1.1.3" ::= { dot1dTp 1 } dot1dTpAgingTime OBJECT-TYPE SYNTAX INTEGER (10..1000000) ACCESS read-write STATUS mandatory DESCRIPTION "The timeout period in seconds for aging out dynamically learned forwarding information. 802.1D-1990 recommends a default of 300 seconds." REFERENCE "IEEE 802.1D-1990: Section 6.7.1.1.3" ::= { dot1dTp 2 } -- The Forwarding Database for Transparent Bridges dot1dTpFdbTable OBJECT-TYPE SYNTAX SEQUENCE OF Dot1dTpFdbEntry ACCESS not-accessible STATUS mandatory DESCRIPTION "A table that contains information about unicast entries for which the bridge has forwarding and/or filtering information. This information is used by the transparent bridging function in determining how to propagate a received frame." ::= { dot1dTp 3 } dot1dTpFdbEntry OBJECT-TYPE SYNTAX Dot1dTpFdbEntry ACCESS not-accessible Decker, Langille, Rijsinghani & McCloghrie [Page 23] RFC 1493 Bridge MIB July 1993 STATUS mandatory DESCRIPTION "Information about a specific unicast MAC address for which the bridge has some forwarding and/or filtering information." INDEX { dot1dTpFdbAddress } ::= { dot1dTpFdbTable 1 } Dot1dTpFdbEntry ::= SEQUENCE { dot1dTpFdbAddress MacAddress, dot1dTpFdbPort INTEGER, dot1dTpFdbStatus INTEGER } dot1dTpFdbAddress OBJECT-TYPE SYNTAX MacAddress ACCESS read-only STATUS mandatory DESCRIPTION "A unicast MAC address for which the bridge has forwarding and/or filtering information." REFERENCE "IEEE 802.1D-1990: Section 3.9.1, 3.9.2" ::= { dot1dTpFdbEntry 1 } dot1dTpFdbPort OBJECT-TYPE SYNTAX INTEGER ACCESS read-only STATUS mandatory DESCRIPTION "Either the value '0', or the port number of the port on which a frame having a source address equal to the value of the corresponding instance of dot1dTpFdbAddress has been seen. A value of '0' indicates that the port number has not been learned but that the bridge does have some forwarding/filtering information about this address (e.g. in the dot1dStaticTable). Implementors are encouraged to assign the port value to this object whenever it is learned even for addresses for which the corresponding value of dot1dTpFdbStatus is not learned(3)." ::= { dot1dTpFdbEntry 2 } Decker, Langille, Rijsinghani & McCloghrie [Page 24] RFC 1493 Bridge MIB July 1993 dot1dTpFdbStatus OBJECT-TYPE SYNTAX INTEGER { other(1), invalid(2), learned(3), self(4), mgmt(5) } ACCESS read-only STATUS mandatory DESCRIPTION "The status of this entry. The meanings of the values are: other(1) : none of the following. This would include the case where some other MIB object (not the corresponding instance of dot1dTpFdbPort, nor an entry in the dot1dStaticTable) is being used to determine if and how frames addressed to the value of the corresponding instance of dot1dTpFdbAddress are being forwarded. invalid(2) : this entry is not longer valid (e.g., it was learned but has since aged-out), but has not yet been flushed from the table. learned(3) : the value of the corresponding instance of dot1dTpFdbPort was learned, and is being used. self(4) : the value of the corresponding instance of dot1dTpFdbAddress represents one of the bridge's addresses. The corresponding instance of dot1dTpFdbPort indicates which of the bridge's ports has this address. mgmt(5) : the value of the corresponding instance of dot1dTpFdbAddress is also the value of an existing instance of dot1dStaticAddress." ::= { dot1dTpFdbEntry 3 } Decker, Langille, Rijsinghani & McCloghrie [Page 25] RFC 1493 Bridge MIB July 1993 -- Port Table for Transparent Bridges dot1dTpPortTable OBJECT-TYPE SYNTAX SEQUENCE OF Dot1dTpPortEntry ACCESS not-accessible STATUS mandatory DESCRIPTION "A table that contains information about every port that is associated with this transparent bridge." ::= { dot1dTp 4 } dot1dTpPortEntry OBJECT-TYPE SYNTAX Dot1dTpPortEntry ACCESS not-accessible STATUS mandatory DESCRIPTION "A list of information for each port of a transparent bridge." INDEX { dot1dTpPort } ::= { dot1dTpPortTable 1 } Dot1dTpPortEntry ::= SEQUENCE { dot1dTpPort INTEGER, dot1dTpPortMaxInfo INTEGER, dot1dTpPortInFrames Counter, dot1dTpPortOutFrames Counter, dot1dTpPortInDiscards Counter } dot1dTpPort OBJECT-TYPE SYNTAX INTEGER (1..65535) ACCESS read-only STATUS mandatory DESCRIPTION "The port number of the port for which this entry contains Transparent bridging management information." ::= { dot1dTpPortEntry 1 } -- It would be nice if we could use ifMtu as the size of the -- largest INFO field, but we can't because ifMtu is defined Decker, Langille, Rijsinghani & McCloghrie [Page 26] RFC 1493 Bridge MIB July 1993 -- to be the size that the (inter-)network layer can use which -- can differ from the MAC layer (especially if several layers -- of encapsulation are used). dot1dTpPortMaxInfo OBJECT-TYPE SYNTAX INTEGER ACCESS read-only STATUS mandatory DESCRIPTION "The maximum size of the INFO (non-MAC) field that this port will receive or transmit." ::= { dot1dTpPortEntry 2 } dot1dTpPortInFrames OBJECT-TYPE SYNTAX Counter ACCESS read-only STATUS mandatory DESCRIPTION "The number of frames that have been received by this port from its segment. Note that a frame received on the interface corresponding to this port is only counted by this object if and only if it is for a protocol being processed by the local bridging function, including bridge management frames." REFERENCE "IEEE 802.1D-1990: Section 6.6.1.1.3" ::= { dot1dTpPortEntry 3 } dot1dTpPortOutFrames OBJECT-TYPE SYNTAX Counter ACCESS read-only STATUS mandatory DESCRIPTION "The number of frames that have been transmitted by this port to its segment. Note that a frame transmitted on the interface corresponding to this port is only counted by this object if and only if it is for a protocol being processed by the local bridging function, including bridge management frames." REFERENCE "IEEE 802.1D-1990: Section 6.6.1.1.3" ::= { dot1dTpPortEntry 4 } dot1dTpPortInDiscards OBJECT-TYPE SYNTAX Counter ACCESS read-only Decker, Langille, Rijsinghani & McCloghrie [Page 27] RFC 1493 Bridge MIB July 1993 STATUS mandatory DESCRIPTION "Count of valid frames received which were discarded (i.e., filtered) by the Forwarding Process." REFERENCE "IEEE 802.1D-1990: Section 6.6.1.1.3" ::= { dot1dTpPortEntry 5 } -- The Static (Destination-Address Filtering) Database -- Implementation of this group is optional. dot1dStaticTable OBJECT-TYPE SYNTAX SEQUENCE OF Dot1dStaticEntry ACCESS not-accessible STATUS mandatory DESCRIPTION "A table containing filtering information configured into the bridge by (local or network) management specifying the set of ports to which frames received from specific ports and containing specific destination addresses are allowed to be forwarded. The value of zero in this table as the port number from which frames with a specific destination address are received, is used to specify all ports for which there is no specific entry in this table for that particular destination address. Entries are valid for unicast and for group/broadcast addresses." REFERENCE "IEEE 802.1D-1990: Section 6.7.2" ::= { dot1dStatic 1 } dot1dStaticEntry OBJECT-TYPE SYNTAX Dot1dStaticEntry ACCESS not-accessible STATUS mandatory DESCRIPTION "Filtering information configured into the bridge by (local or network) management specifying the set of ports to which frames received from a specific port and containing a specific destination address are allowed to be forwarded." REFERENCE "IEEE 802.1D-1990: Section 6.7.2" Decker, Langille, Rijsinghani & McCloghrie [Page 28] RFC 1493 Bridge MIB July 1993 INDEX { dot1dStaticAddress, dot1dStaticReceivePort } ::= { dot1dStaticTable 1 } Dot1dStaticEntry ::= SEQUENCE { dot1dStaticAddress MacAddress, dot1dStaticReceivePort INTEGER, dot1dStaticAllowedToGoTo OCTET STRING, dot1dStaticStatus INTEGER } dot1dStaticAddress OBJECT-TYPE SYNTAX MacAddress ACCESS read-write STATUS mandatory DESCRIPTION "The destination MAC address in a frame to which this entry's filtering information applies. This object can take the value of a unicast address, a group address or the broadcast address." REFERENCE "IEEE 802.1D-1990: Section 3.9.1, 3.9.2" ::= { dot1dStaticEntry 1 } dot1dStaticReceivePort OBJECT-TYPE SYNTAX INTEGER ACCESS read-write STATUS mandatory DESCRIPTION "Either the value '0', or the port number of the port from which a frame must be received in order for this entry's filtering information to apply. A value of zero indicates that this entry applies on all ports of the bridge for which there is no other applicable entry." ::= { dot1dStaticEntry 2 } dot1dStaticAllowedToGoTo OBJECT-TYPE SYNTAX OCTET STRING ACCESS read-write STATUS mandatory DESCRIPTION "The set of ports to which frames received from a specific port and destined for a specific MAC Decker, Langille, Rijsinghani & McCloghrie [Page 29] RFC 1493 Bridge MIB July 1993 address, are allowed to be forwarded. Each octet within the value of this object specifies a set of eight ports, with the first octet specifying ports 1 through 8, the second octet specifying ports 9 through 16, etc. Within each octet, the most significant bit represents the lowest numbered port, and the least significant bit represents the highest numbered port. Thus, each port of the bridge is represented by a single bit within the value of this object. If that bit has a value of '1' then that port is included in the set of ports; the port is not included if its bit has a value of '0'. (Note that the setting of the bit corresponding to the port from which a frame is received is irrelevant.) The default value of this object is a string of ones of appropriate length." ::= { dot1dStaticEntry 3 } dot1dStaticStatus OBJECT-TYPE SYNTAX INTEGER { other(1), invalid(2), permanent(3), deleteOnReset(4), deleteOnTimeout(5) } ACCESS read-write STATUS mandatory DESCRIPTION "This object indicates the status of this entry. The default value is permanent(3). other(1) - this entry is currently in use but the conditions under which it will remain so are different from each of the following values. invalid(2) - writing this value to the object removes the corresponding entry. permanent(3) - this entry is currently in use and will remain so after the next reset of the bridge. deleteOnReset(4) - this entry is currently in use and will remain so until the next reset of the bridge. deleteOnTimeout(5) - this entry is currently in use and will remain so until it is aged out." Decker, Langille, Rijsinghani & McCloghrie [Page 30] RFC 1493 Bridge MIB July 1993 ::= { dot1dStaticEntry 4 } -- Traps for use by Bridges -- Traps for the Spanning Tree Protocol newRoot TRAP-TYPE ENTERPRISE dot1dBridge DESCRIPTION "The newRoot trap indicates that the sending agent has become the new root of the Spanning Tree; the trap is sent by a bridge soon after its election as the new root, e.g., upon expiration of the Topology Change Timer immediately subsequent to its election. Implementation of this trap is optional." ::= 1 topologyChange TRAP-TYPE ENTERPRISE dot1dBridge DESCRIPTION "A topologyChange trap is sent by a bridge when any of its configured ports transitions from the Learning state to the Forwarding state, or from the Forwarding state to the Blocking state. The trap is not sent if a newRoot trap is sent for the same transition. Implementation of this trap is optional." ::= 2 END 6. Acknowledgments This document was produced on behalf of the Bridge Sub-Working Group of the SNMP Working Group of the Internet Engineering Task Force. Over the course of its deliberations, the working group received four separate documents for consideration as the basis for its work. The first was submitted by Stan Froyd of Advanced Computer Communications; the second by Richard Fox of SynOptics; the third by Eric Decker of cisco Inc. and Keith McCloghrie of Hughes LAN Systems; and the fourth by Paul Langille and Anil Rijsinghani of Digital Equipment Corp. After considering the submissions, the working group chose to proceed with a document formed as a conjunction of the latter two submissions. This document is the result. Decker, Langille, Rijsinghani & McCloghrie [Page 31] RFC 1493 Bridge MIB July 1993 The authors wish to thank the members of the Bridge Working Group for their many comments and suggestions which improved this effort. In particular, Fred Baker (chairman of the working group) of ACC, Steve Sherry of Xyplex, and Frank Kastenholz of Clearpoint Research Corp. Others members of the Bridge Working Group who contributed to this effort are: Bill Anderson, Mitre Karl Auerbach, Epilogue Fred Baker, ACC (chair) Terry Bradley, Wellfleet Ted Brunner, Bellcore Jeffrey Buffum, Apollo Chris ChioTasso, Fibronics Anthony Chung, HLS Chuck Davin, MIT-LCS Andy Davis, Spider Eric Decker, cisco Nadya El-Afandi, Network Systems Gary Ellis,HP/Apollo Richard Fox, SynOptics Stan Froyd, ACC Frank Kastenholz, Clearpoint Research Shirnshon Kaufman, Jim Kinder, Fibercom Cheryl Krupczak,NCR Paul Langille, Digital Peter Lin,Vitalink Keith McCloghrie, HLS Donna McMaster, SynOptics Dave Perkins, 3Com Jim Reinstedler, Ungermann Bass Anil Rijsinghani, Digital Mark Schaefer, David Systems Steve Sherry, Xyplex Bob Stewart, Xyplex Emil Sturniolo, Kevin Synott, Retix Ian Thomas, Chipcom Maurice Turcott, Racal Fei Xu, Decker, Langille, Rijsinghani & McCloghrie [Page 32] RFC 1493 Bridge MIB July 1993 7. References [1] Cerf, V., "IAB Recommendations for the Development of Internet Network Management Standards", RFC 1052, NRI, April 1988. [2] Cerf, V., "Report of the Second Ad Hoc Network Management Review Group", RFC 1109, NRI, August 1989. [3] Rose M., and K. McCloghrie, "Structure and Identification of Management Information for TCP/IP-based internets", STD 16, RFC 1155, Performance Systems International, Hughes LAN Systems, May 1990. [4] Case, J., Fedor, M., Schoffstall, M., and J. Davin, "Simple Network Management Protocol", STD 15, RFC 1157, SNMP Research, Performance Systems International, Performance Systems International, MIT Laboratory for Computer Science, May 1990. [5] McCloghrie K., and M. Rose, Editors, "Management Information Base for Network Management of TCP/IP-based internets", STD 17, RFC 1213, Performance Systems International, March 1991. [6] Information processing systems - Open Systems Interconnection - Specification of Abstract Syntax Notation One (ASN.1), International Organization for Standardization, International Standard 8824, December 1987. [7] Information processing systems - Open Systems Interconnection - Specification of Basic Encoding Rules for Abstract Notation One (ASN.1), International Organization for Standardization, International Standard 8825, December 1987. [8] Rose, M., and K. McCloghrie, Editors, "Concise MIB Definitions", STD 16, RFC 1212, Performance Systems International, Hughes LAN Systems, March 1991. [9] Rose, M., Editor, "A Convention for Defining Traps for use with the SNMP", RFC 1215, Performance Systems International, March 1991. [10] ANSI/IEEE Standard 802.1D-1990 MAC Bridges, IEEE Project 802 Local and Metropolitan Area Networks, (March 8, 1991). [11] ISO DIS 10038 MAC Bridges. 8. Security Considerations Security issues are not discussed in this memo. Decker, Langille, Rijsinghani & McCloghrie [Page 33] RFC 1493 Bridge MIB July 1993 9. Authors' Addresses Eric B. Decker cisco Systems, Inc. 1525 O'Brien Dr. Menlo Park, CA 94025 Phone: (415) 326-1941 Email: cire@cisco.com Paul Langille Digital Equipment Corporation Digital Drive, MK02-2/K03 Merrimack, NH 03054 Phone: (603) 884-4045 EMail: langille@edwin.enet.dec.com Anil Rijsinghani Digital Equipment Corporation 550 King Street Littleton, MA 01460 Phone: (508) 486-6786 EMail: anil@levers.enet.dec.com Keith McCloghrie Hughes LAN Systems, Inc. 1225 Charleston Road Mountain View, CA 94043 Phone: (415) 966-7934 EMail: kzm@hls.com Decker, Langille, Rijsinghani & McCloghrie [Page 34]