CISCO-NTP-MIB

File: CISCO-NTP-MIB.mib (54333 bytes)

Imported modules

SNMPv2-SMI SNMPv2-CONF SNMPv2-TC
INET-ADDRESS-MIB CISCO-SMI

Imported symbols

MODULE-IDENTITY OBJECT-TYPE NOTIFICATION-TYPE
Integer32 IpAddress Gauge32
Unsigned32 MODULE-COMPLIANCE OBJECT-GROUP
NOTIFICATION-GROUP TEXTUAL-CONVENTION TruthValue
RowStatus InetAddress InetAddressType
ciscoMgmt

Defined Types

NTPTimeStamp  
NTP timestamps are represented as a 64-bit unsigned fixed-point number, in seconds relative to 00:00 on 1 January 1900. The integer part is in the first 32 bits and the fraction part is in the last 32 bits.
TEXTUAL-CONVENTION    
  OCTET STRING Size(8)  

NTPLeapIndicator  
This is a two-bit code warning of an impending leap second to be inserted in the NTP timescale. The bits are set before 23:59 on the day of insertion and reset after 00:00 on the following day. This causes the number of seconds (rollover interval) in the day of insertion to be increased or decreased by one. The two bits are coded as below, 00, no warning 01, last minute has 61 seconds 10, last minute has 59 seconds 11, alarm condition (clock not synchronized)
TEXTUAL-CONVENTION    
  INTEGER noWarning(0), addSecond(1), subtractSecond(2), alarm(3)  

NTPSignedTimeValue  
The time in seconds that could represent signed quantities like time delay with respect to some source. This textual-convention is specific to Cisco implementation of NTP where 32-bit integers are used for such quantities. The signed integer part is in the first 16 bits and the fraction part is in the last 16 bits.
TEXTUAL-CONVENTION    
  OCTET STRING Size(4)  

NTPUnsignedTimeValue  
The time in seconds that could represent unsigned quantities like maximum error of the local clock with respect to some source. This textual-convention is specific to Cisco implementation of NTP where 32-bit integers are used for such quantities. The unsigned integer part is in the first 16 bits and the fraction part is in the last 16 bits.
TEXTUAL-CONVENTION    
  OCTET STRING Size(4)  

NTPStratum  
Indicates the stratum of the clock. The stratum defines the accuracy of a time server. Higher the stratum, lower the accuracy. 0, unspecified 1, primary reference (e.g., calibrated atomic clock, radio clock) 2-255, secondary reference (via NTP)
TEXTUAL-CONVENTION    
  Integer32 0..255  

NTPRefId  
The reference clock identifier. In the case of stratum 0 (unspecified) or stratum 1 (primary reference source), this is a four-octet, left-justified, zero-padded ASCII string as defined in RFC-1305. In the case of stratum 2 and greater (secondary reference) this is the four-octet Internet address of the peer selected for synchronization. Some examples of stratum 0 identifiers are, DCN, DCN routing protocol NIST, NIST public modem TSP, TSP time protocol DTS, Digital Time Service Some examples of stratum 1 identifiers are, ATOM, Atomic clock (calibrated) VLF, VLF radio (OMEGA,, etc.) LORC, LORAN-C radionavigation GOES, GOES UHF environment satellite GPS, GPS UHF satellite positioning
TEXTUAL-CONVENTION    
  OCTET STRING Size(4)  

NTPPollInterval  
The minimum interval between transmitted NTP messages, in seconds as a power of two. For instance, a value of six indicates a minimum interval of 64 seconds.
TEXTUAL-CONVENTION    
  Integer32 -20..20  

NTPAssocIdentifier  
The association identifier of the peer. Every peer with which an NTP server is associated with is identified by an association identifier.
TEXTUAL-CONVENTION    
  Integer32 0..2147483647  

CntpPeersVarEntry  
SEQUENCE    
  cntpPeersAssocId NTPAssocIdentifier
  cntpPeersConfigured TruthValue
  cntpPeersPeerAddress IpAddress
  cntpPeersPeerPort Integer32
  cntpPeersHostAddress IpAddress
  cntpPeersHostPort Integer32
  cntpPeersLeap NTPLeapIndicator
  cntpPeersMode INTEGER
  cntpPeersStratum NTPStratum
  cntpPeersPeerPoll NTPPollInterval
  cntpPeersHostPoll NTPPollInterval
  cntpPeersPrecision Integer32
  cntpPeersRootDelay NTPSignedTimeValue
  cntpPeersRootDispersion NTPUnsignedTimeValue
  cntpPeersRefId NTPRefId
  cntpPeersRefTime NTPTimeStamp
  cntpPeersOrgTime NTPTimeStamp
  cntpPeersReceiveTime NTPTimeStamp
  cntpPeersTransmitTime NTPTimeStamp
  cntpPeersUpdateTime Integer32
  cntpPeersReach Integer32
  cntpPeersTimer Integer32
  cntpPeersOffset NTPSignedTimeValue
  cntpPeersDelay NTPSignedTimeValue
  cntpPeersDispersion NTPUnsignedTimeValue
  cntpPeersFilterValidEntries Gauge32
  cntpPeersEntryStatus RowStatus
  cntpPeersUpdateTimeRev1 Unsigned32
  cntpPeersPrefPeer TruthValue
  cntpPeersPeerType InetAddressType
  cntpPeersPeerName InetAddress

CntpFilterRegisterEntry  
SEQUENCE    
  cntpFilterIndex Integer32
  cntpFilterPeersOffset NTPSignedTimeValue
  cntpFilterPeersDelay NTPSignedTimeValue
  cntpFilterPeersDispersion NTPUnsignedTimeValue

Defined Values

ciscoNtpMIB 1.3.6.1.4.1.9.9.168
This MIB module defines a MIB which provides mechanisms to monitor an NTP server. The MIB is derived from the Technical Report #Management of the NTP with SNMP# TR No. 98-09 authored by A.S. Sethi and Dave Mills in the University of Delaware. Below is a brief overview of NTP system architecture and implementation model. This will help understand the objects defined below and their relationships. NTP Intro: The Network Time Protocol (NTP) Version 3, is used to synchronize timekeeping among a set of distributed time servers and clients. The service model is based on a returnable-time design which depends only on measured clock offsets, but does not require reliable message delivery. The synchronization subnet uses a self-organizing, hierarchical master-slave configuration, with synchronization paths determined by a minimum-weight spanning tree. While multiple masters (primary servers) may exist, there is no requirement for an election protocol. System Archiecture: In the NTP model a number of primary reference sources, synchronized by wire or radio to national standards, are connected to widely accessible resources, such as backbone gateways, and operated as primary time servers. The purpose of NTP is to convey timekeeping information from these servers to other time servers via the Internet and also to cross-check clocks and mitigate errors due to equipment or propagation failures. Some number of local-net hosts or gateways, acting as secondary time servers, run NTP with one or more of the primary servers. In order to reduce the protocol overhead, the secondary servers distribute time via NTP to the remaining local-net hosts. In the interest of reliability, selected hosts can be equipped with less accurate but less expensive radio clocks and used for backup in case of failure of the primary and/or secondary servers or communication paths between them. NTP is designed to produce three products: clock offset, round-trip delay and dispersion, all of which are relative to a selected reference clock. Clock offset represents the amount to adjust the local clock to bring it into correspondence with the reference clock. Roundtrip delay provides the capability to launch a message to arrive at the reference clock at a specified time. Dispersion represents the maximum error of the local clock relative to the reference clock. Since most host time servers will synchronize via another peer time server, there are two components in each of these three products, those determined by the peer relative to the primary reference source of standard time and those measured by the host relative to the peer. Each of these components are maintained separately in the protocol in order to facilitate error control and management of the subnet itself. They provide not only precision measurements of offset and delay, but also definitive maximum error bounds, so that the user interface can determine not only the time, but the quality of the time as well. Implementation Model: In what may be the most common client/server model a client sends an NTP message to one or more servers and processes the replies as received. The server interchanges addresses and ports, overwrites certain fields in the message, recalculates the checksum and returns the message immediately. Information included in the NTP message allows the client to determine the server time with respect to local time and adjust the local clock accordingly. In addition, the message includes information to calculate the expected timekeeping accuracy and reliability, as well as select the best from possibly several servers. While the client/server model may suffice for use on local nets involving a public server and perhaps many workstation clients, the full generality of NTP requires distributed participation of a number of client/servers or peers arranged in a dynamically reconfigurable, hierarchically distributed configuration. It also requires sophisticated algorithms for association management, data manipulation and local-clock control. Glossary: 1. Host: Refers to an instantiation of the NTP protocol on a local processor. 2. Peer: Refers to an instantiation of the NTP protocol on a remote processor connected by a network path from the local host.
MODULE-IDENTITY    

ciscoNtpMIBNotifs 1.3.6.1.4.1.9.9.168.0
OBJECT IDENTIFIER    

ciscoNtpMIBObjects 1.3.6.1.4.1.9.9.168.1
OBJECT IDENTIFIER    

ciscoNtpMIBConformance 1.3.6.1.4.1.9.9.168.2
OBJECT IDENTIFIER    

cntpSystem 1.3.6.1.4.1.9.9.168.1.1
OBJECT IDENTIFIER    

cntpPeers 1.3.6.1.4.1.9.9.168.1.2
OBJECT IDENTIFIER    

cntpFilter 1.3.6.1.4.1.9.9.168.1.3
OBJECT IDENTIFIER    

cntpSysLeap 1.3.6.1.4.1.9.9.168.1.1.1
Two-bit code warning of an impending leap second to be inserted in the NTP timescale. This object can be set only when the cntpSysStratum has a value of 1.
Status: current Access: read-write
OBJECT-TYPE    
  NTPLeapIndicator  

cntpSysStratum 1.3.6.1.4.1.9.9.168.1.1.2
The stratum of the local clock. If the value is set to 1, i.e., this is a primary reference, then the Primary-Clock procedure described in Section 3.4.6, in RFC-1305 is invoked.
Status: current Access: read-write
OBJECT-TYPE    
  NTPStratum  

cntpSysPrecision 1.3.6.1.4.1.9.9.168.1.1.3
Signed integer indicating the precision of the system clock, in seconds to the nearest power of two. The value must be rounded to the next larger power of two; for instance, a 50-Hz (20 ms) or 60-Hz (16.67 ms) power-frequency clock would be assigned the value -5 (31.25 ms), while a 1000-Hz (1 ms) crystal-controlled clock would be assigned the value -9 (1.95 ms).
Status: current Access: read-only
OBJECT-TYPE    
  Integer32 -20..20  

cntpSysRootDelay 1.3.6.1.4.1.9.9.168.1.1.4
A signed fixed-point number indicating the total round-trip delay in seconds, to the primary reference source at the root of the synchronization subnet.
Status: current Access: read-only
OBJECT-TYPE    
  NTPSignedTimeValue  

cntpSysRootDispersion 1.3.6.1.4.1.9.9.168.1.1.5
The maximum error in seconds, relative to the primary reference source at the root of the synchronization subnet. Only positive values greater than zero are possible.
Status: current Access: read-only
OBJECT-TYPE    
  NTPUnsignedTimeValue  

cntpSysRefId 1.3.6.1.4.1.9.9.168.1.1.6
The reference identifier of the local clock.
Status: current Access: read-only
OBJECT-TYPE    
  NTPRefId  

cntpSysRefTime 1.3.6.1.4.1.9.9.168.1.1.7
The local time when the local clock was last updated. If the local clock has never been synchronized, the value is zero.
Status: current Access: read-only
OBJECT-TYPE    
  NTPTimeStamp  

cntpSysPoll 1.3.6.1.4.1.9.9.168.1.1.8
The interval at which the NTP server polls other NTP servers to synchronize its clock.
Status: current Access: read-only
OBJECT-TYPE    
  NTPPollInterval  

cntpSysPeer 1.3.6.1.4.1.9.9.168.1.1.9
The current synchronization source. This will contain the unique association identifier cntpPeersAssocId of the corresponding peer entry in the cntpPeersVarTable of the peer acting as the synchronization source. If there is no peer, the value will be 0.
Status: current Access: read-only
OBJECT-TYPE    
  NTPAssocIdentifier  

cntpSysClock 1.3.6.1.4.1.9.9.168.1.1.10
The current local time. Local time is derived from the hardware clock of the particular machine and increments at intervals depending on the design used.
Status: current Access: read-only
OBJECT-TYPE    
  NTPTimeStamp  

cntpSysSrvStatus 1.3.6.1.4.1.9.9.168.1.1.11
Current state of the NTP server with values coded as follows: 1: server status is unknown 2: server is not running 3: server is not synchronized to any time source 4: server is synchronized to its own local clock 5: server is synchronized to a local hardware refclock (e.g. GPS) 6: server is synchronized to a remote NTP server
Status: current Access: read-only
OBJECT-TYPE    
  INTEGER unknown(1), notRunning(2), notSynchronized(3), syncToLocal(4), syncToRefclock(5), syncToRemoteServer(6)  

cntpPeersVarTable 1.3.6.1.4.1.9.9.168.1.2.1
This table provides information on the peers with which the local NTP server has associations. The peers are also NTP servers but running on different hosts.
Status: current Access: not-accessible
OBJECT-TYPE    
  SEQUENCE OF  
    CntpPeersVarEntry

cntpPeersVarEntry 1.3.6.1.4.1.9.9.168.1.2.1.1
Each peers' entry provides NTP information retrieved from a particular peer NTP server. Each peer is identified by a unique association identifier. Entries are automatically created when the user configures the NTP server to be associated with remote peers. Similarly entries are deleted when the user removes the peer association from the NTP server. Entries can also be created by the management station by setting values for the following objects: cntpPeersPeerAddress or cntpPeersPeerName, cntpPeersHostAddress and cntpPeersMode and making the cntpPeersEntryStatus as active(1). At the least, the management station has to set a value for cntpPeersPeerAddress or cntpPeersPeerName to make the row active.
Status: current Access: not-accessible
OBJECT-TYPE    
  CntpPeersVarEntry  

cntpPeersAssocId 1.3.6.1.4.1.9.9.168.1.2.1.1.1
An integer value greater than 0 that uniquely identifies a peer with which the local NTP server is associated.
Status: current Access: not-accessible
OBJECT-TYPE    
  NTPAssocIdentifier  

cntpPeersConfigured 1.3.6.1.4.1.9.9.168.1.2.1.1.2
This is a bit indicating that the association was created from configuration information and should not be de-associated even if the peer becomes unreachable.
Status: current Access: read-only
OBJECT-TYPE    
  TruthValue  

cntpPeersPeerAddress 1.3.6.1.4.1.9.9.168.1.2.1.1.3
The IP address of the peer. When creating a new association, a value should be set either for this object or the corresponding instance of cntpPeersPeerName, before the row is made active.
Status: current Access: read-create
OBJECT-TYPE    
  IpAddress  

cntpPeersPeerPort 1.3.6.1.4.1.9.9.168.1.2.1.1.4
The UDP port number on which the peer receives NTP messages.
Status: current Access: read-only
OBJECT-TYPE    
  Integer32 1..65535  

cntpPeersHostAddress 1.3.6.1.4.1.9.9.168.1.2.1.1.5
The IP address of the local host. Multi-homing can be supported using this object.
Status: current Access: read-create
OBJECT-TYPE    
  IpAddress  

cntpPeersHostPort 1.3.6.1.4.1.9.9.168.1.2.1.1.6
The UDP port number on which the local host receives NTP messages.
Status: current Access: read-only
OBJECT-TYPE    
  Integer32 1..65535  

cntpPeersLeap 1.3.6.1.4.1.9.9.168.1.2.1.1.7
Two-bit code warning of an impending leap second to be inserted in the NTP timescale of the peer.
Status: current Access: read-only
OBJECT-TYPE    
  NTPLeapIndicator  

cntpPeersMode 1.3.6.1.4.1.9.9.168.1.2.1.1.8
The association mode of the NTP server, with values coded as follows, 0, unspecified 1, symmetric active - A host operating in this mode sends periodic messages regardless of the reachability state or stratum of its peer. By operating in this mode the host announces its willingness to synchronize and be synchronized by the peer 2, symmetric passive - This type of association is ordinarily created upon arrival of a message from a peer operating in the symmetric active mode and persists only as long as the peer is reachable and operating at a stratum level less than or equal to the host; otherwise, the association is dissolved. However, the association will always persist until at least one message has been sent in reply. By operating in this mode the host announces its willingness to synchronize and be synchronized by the peer 3, client - A host operating in this mode sends periodic messages regardless of the reachability state or stratum of its peer. By operating in this mode the host, usually a LAN workstation, announces its willingness to be synchronized by, but not to synchronize the peer 4, server - This type of association is ordinarily created upon arrival of a client request message and exists only in order to reply to that request, after which the association is dissolved. By operating in this mode the host, usually a LAN time server, announces its willingness to synchronize, but not to be synchronized by the peer 5, broadcast - A host operating in this mode sends periodic messages regardless of the reachability state or stratum of the peers. By operating in this mode the host, usually a LAN time server operating on a high-speed broadcast medium, announces its willingness to synchronize all of the peers, but not to be synchronized by any of them 6, reserved for NTP control messages 7, reserved for private use. When creating a new peer association, if no value is specified for this object, it defaults to symmetricActive(1).
Status: current Access: read-create
OBJECT-TYPE    
  INTEGER unspecified(0), symmetricActive(1), symmetricPassive(2), client(3), server(4), broadcast(5), reservedControl(6), reservedPrivate(7)  

cntpPeersStratum 1.3.6.1.4.1.9.9.168.1.2.1.1.9
The stratum of the peer clock.
Status: current Access: read-only
OBJECT-TYPE    
  NTPStratum  

cntpPeersPeerPoll 1.3.6.1.4.1.9.9.168.1.2.1.1.10
The interval at which the peer polls the local host.
Status: current Access: read-only
OBJECT-TYPE    
  NTPPollInterval  

cntpPeersHostPoll 1.3.6.1.4.1.9.9.168.1.2.1.1.11
The interval at which the local host polls the peer.
Status: current Access: read-only
OBJECT-TYPE    
  NTPPollInterval  

cntpPeersPrecision 1.3.6.1.4.1.9.9.168.1.2.1.1.12
Signed integer indicating the precision of the peer clock, in seconds to the nearest power of two. The value must be rounded to the next larger power of two; for instance, a 50-Hz (20 ms) or 60-Hz (16.67 ms) power-frequency clock would be assigned the value -5 (31.25 ms), while a 1000-Hz (1 ms) crystal-controlled clock would be assigned the value -9 (1.95 ms).
Status: current Access: read-only
OBJECT-TYPE    
  Integer32 -20..20  

cntpPeersRootDelay 1.3.6.1.4.1.9.9.168.1.2.1.1.13
A signed fixed-point number indicating the total round-trip delay in seconds, from the peer to the primary reference source at the root of the synchronization subnet.
Status: current Access: read-only
OBJECT-TYPE    
  NTPSignedTimeValue  

cntpPeersRootDispersion 1.3.6.1.4.1.9.9.168.1.2.1.1.14
The maximum error in seconds, of the peer clock relative to the primary reference source at the root of the synchronization subnet. Only positive values greater than zero are possible.
Status: current Access: read-only
OBJECT-TYPE    
  NTPUnsignedTimeValue  

cntpPeersRefId 1.3.6.1.4.1.9.9.168.1.2.1.1.15
The reference identifier of the peer.
Status: current Access: read-only
OBJECT-TYPE    
  NTPRefId  

cntpPeersRefTime 1.3.6.1.4.1.9.9.168.1.2.1.1.16
The local time at the peer when its clock was last updated. If the peer clock has never been synchronized, the value is zero.
Status: current Access: read-only
OBJECT-TYPE    
  NTPTimeStamp  

cntpPeersOrgTime 1.3.6.1.4.1.9.9.168.1.2.1.1.17
The local time at the peer, when its latest NTP message was sent. If the peer becomes unreachable the value is set to zero.
Status: current Access: read-only
OBJECT-TYPE    
  NTPTimeStamp  

cntpPeersReceiveTime 1.3.6.1.4.1.9.9.168.1.2.1.1.18
The local time, when the latest NTP message from the peer arrived. If the peer becomes unreachable the value is set to zero.
Status: current Access: read-only
OBJECT-TYPE    
  NTPTimeStamp  

cntpPeersTransmitTime 1.3.6.1.4.1.9.9.168.1.2.1.1.19
The local time at which the NTP message departed the sender.
Status: current Access: read-only
OBJECT-TYPE    
  NTPTimeStamp  

cntpPeersUpdateTime 1.3.6.1.4.1.9.9.168.1.2.1.1.20
The local time, when the most recent NTP message was received from the peer that was used to calculate the skew dispersion. This represents only the 32-bit integer part of the NTPTimestamp.
Status: deprecated Access: read-only
OBJECT-TYPE    
  Integer32 0..2147483647  

cntpPeersReach 1.3.6.1.4.1.9.9.168.1.2.1.1.21
A shift register of used to determine the reachability status of the peer, with bits entering from the least significant (rightmost) end. A peer is considered reachable if at least one bit in this register is set to one i.e, if the value of this object is non-zero. The data in the shift register would be populated by the NTP protocol procedures.
Status: current Access: read-only
OBJECT-TYPE    
  Integer32 0..255  

cntpPeersTimer 1.3.6.1.4.1.9.9.168.1.2.1.1.22
The interval in seconds, between transmitted NTP messages from the local host to the peer.
Status: current Access: read-only
OBJECT-TYPE    
  Integer32 0..2147483647  

cntpPeersOffset 1.3.6.1.4.1.9.9.168.1.2.1.1.23
The estimated offset of the peer clock relative to the local clock, in seconds. The host determines the value of this object using the NTP clock-filter algorithm.
Status: current Access: read-only
OBJECT-TYPE    
  NTPSignedTimeValue  

cntpPeersDelay 1.3.6.1.4.1.9.9.168.1.2.1.1.24
The estimated round-trip delay of the peer clock relative to the local clock over the network path between them, in seconds. The host determines the value of this object using the NTP clock-filter algorithm.
Status: current Access: read-only
OBJECT-TYPE    
  NTPSignedTimeValue  

cntpPeersDispersion 1.3.6.1.4.1.9.9.168.1.2.1.1.25
The estimated maximum error of the peer clock relative to the local clock over the network path between them, in seconds. The host determines the value of this object using the NTP clock-filter algorithm.
Status: current Access: read-only
OBJECT-TYPE    
  NTPUnsignedTimeValue  

cntpPeersFilterValidEntries 1.3.6.1.4.1.9.9.168.1.2.1.1.26
The number of valid entries for a peer in the Filter Register Table. Since, the Filter Register Table is optional, this object will have a value 0 if the Filter Register Table is not implemented.
Status: current Access: read-only
OBJECT-TYPE    
  Gauge32  

cntpPeersEntryStatus 1.3.6.1.4.1.9.9.168.1.2.1.1.27
The status object for this row. When a management station is creating a new row, it should set the value for cntpPeersPeerAddress at least, before the row can be made active(1).
Status: current Access: read-create
OBJECT-TYPE    
  RowStatus  

cntpPeersUpdateTimeRev1 1.3.6.1.4.1.9.9.168.1.2.1.1.28
The local time, when the most recent NTP message was received from the peer that was used to calculate the skew dispersion. This represents only the 32-bit integer part of the NTPTimestamp.
Status: current Access: read-only
OBJECT-TYPE    
  Unsigned32  

cntpPeersPrefPeer 1.3.6.1.4.1.9.9.168.1.2.1.1.29
This object specifies whether this peer is the preferred one over the others. By default, when the value of this object is 'false', NTP chooses the peer with which to synchronize the time on the local system. If this object is set to 'true', NTP will choose the corresponding peer to synchronize the time with. If multiple entries have this object set to 'true', NTP will choose the first one to be set. This object is a means to override the selection of the peer by NTP.
Status: current Access: read-create
OBJECT-TYPE    
  TruthValue  

cntpPeersPeerType 1.3.6.1.4.1.9.9.168.1.2.1.1.30
Represents the type of the corresponding instance of cntpPeersPeerName object.
Status: current Access: read-create
OBJECT-TYPE    
  InetAddressType  

cntpPeersPeerName 1.3.6.1.4.1.9.9.168.1.2.1.1.31
The address of the peer. When creating a new association, a value must be set for either this object or the corresponding instance of cntpPeersPeerAddress object, before the row is made active.
Status: current Access: read-create
OBJECT-TYPE    
  InetAddress  

cntpFilterRegisterTable 1.3.6.1.4.1.9.9.168.1.3.2
The following table contains NTP state variables used by the NTP clock filter and selection algorithms. This table depicts a shift register. Each stage in the shift register is a 3-tuple consisting of the measured clock offset, measured clock delay and measured clock dispersion associated with a single observation. An important factor affecting the accuracy and reliability of time distribution is the complex of algorithms used to reduce the effect of statistical errors and falsetickers due to failure of various subnet components, reference sources or propagation media. The NTP clock-filter and selection algorithms are designed to do exactly this. The objects in the filter register table below are used by these algorthims to minimize the error in the calculated time.
Status: current Access: not-accessible
OBJECT-TYPE    
  SEQUENCE OF  
    CntpFilterRegisterEntry

cntpFilterRegisterEntry 1.3.6.1.4.1.9.9.168.1.3.2.1
Each entry corresponds to one stage of the shift register, i.e., one reading of the variables clock delay, clock offset and clock dispersion. Entries are automatically created whenever a peer is configured and deleted when the peer is removed.
Status: current Access: not-accessible
OBJECT-TYPE    
  CntpFilterRegisterEntry  

cntpFilterIndex 1.3.6.1.4.1.9.9.168.1.3.2.1.1
An integer value in the specified range that is used to index into the table. The size of the table is fixed at 8. Each entry identifies a particular reading of the clock filter variables in the shift register. Entries are added starting at index 1. The index wraps back to 1 when it reaches 8. When the index wraps back, the new entries will overwrite the old entries effectively deleting the old entry.
Status: current Access: not-accessible
OBJECT-TYPE    
  Integer32 1..8  

cntpFilterPeersOffset 1.3.6.1.4.1.9.9.168.1.3.2.1.2
The offset of the peer clock relative to the local clock in seconds.
Status: current Access: read-only
OBJECT-TYPE    
  NTPSignedTimeValue  

cntpFilterPeersDelay 1.3.6.1.4.1.9.9.168.1.3.2.1.3
Round-trip delay of the peer clock relative to the local clock over the network path between them, in seconds. This variable can take on both positive and negative values, depending on clock precision and skew-error accumulation.
Status: current Access: read-only
OBJECT-TYPE    
  NTPSignedTimeValue  

cntpFilterPeersDispersion 1.3.6.1.4.1.9.9.168.1.3.2.1.4
The maximum error of the peer clock relative to the local clock over the network path between them, in seconds. Only positive values greater than zero are possible.
Status: current Access: read-only
OBJECT-TYPE    
  NTPUnsignedTimeValue  

ciscoNtpSrvStatusChange 1.3.6.1.4.1.9.9.168.0.1
This notification is generated whenever the value of cntpSysSrvStatus changes.
Status: current Access: read-only
NOTIFICATION-TYPE    

ciscoNtpHighPriorityConnFailure 1.3.6.1.4.1.9.9.168.0.2
A failure to connect with an high priority NTP server (e.g. a server at the lowest stratum) is detected.
Status: current Access: read-only
NOTIFICATION-TYPE    

ciscoNtpHighPriorityConnRestore 1.3.6.1.4.1.9.9.168.0.3
A connection with an high priority NTP server (e.g. a server at the lowest stratum) is restored.
Status: current Access: read-only
NOTIFICATION-TYPE    

ciscoNtpGeneralConnFailure 1.3.6.1.4.1.9.9.168.0.4
This trap is sent when the device loses connectivity to all NTP servers.
Status: current Access: read-only
NOTIFICATION-TYPE    

ciscoNtpGeneralConnRestore 1.3.6.1.4.1.9.9.168.0.5
This trap is sent when the connection with at least one NTP server has been restored (e.g. after a ciscoNtpGeneralConnFailure).
Status: current Access: read-only
NOTIFICATION-TYPE    

ciscoNtpMIBCompliances 1.3.6.1.4.1.9.9.168.2.1
OBJECT IDENTIFIER    

ciscoNtpMIBGroups 1.3.6.1.4.1.9.9.168.2.2
OBJECT IDENTIFIER    

ciscoNtpMIBCompliance 1.3.6.1.4.1.9.9.168.2.1.1
The compliance statement for Cisco agents which implement the Cisco NTP MIB.
Status: deprecated Access: read-only
MODULE-COMPLIANCE    

ciscoNtpMIBComplianceRev1 1.3.6.1.4.1.9.9.168.2.1.2
The compliance statement for Cisco agents which implement the Cisco NTP MIB.
Status: deprecated Access: read-only
MODULE-COMPLIANCE    

ciscoNtpMIBComplianceRev2 1.3.6.1.4.1.9.9.168.2.1.3
The compliance statement for Cisco agents which implement the Cisco NTP MIB.
Status: deprecated Access: read-only
MODULE-COMPLIANCE    

ciscoNtpMIBComplianceRev3 1.3.6.1.4.1.9.9.168.2.1.4
The compliance statement for Cisco agents which implement the Cisco NTP MIB.
Status: deprecated Access: read-only
MODULE-COMPLIANCE    

ciscoNtpMIBComplianceRev4 1.3.6.1.4.1.9.9.168.2.1.5
The compliance statement for Cisco agents which implement the Cisco NTP MIB.
Status: current Access: read-only
MODULE-COMPLIANCE    

ciscoNtpSysGroup 1.3.6.1.4.1.9.9.168.2.2.1
The NTP system variables.
Status: current Access: read-only
OBJECT-GROUP    

ciscoNtpPeersGroup 1.3.6.1.4.1.9.9.168.2.2.2
The NTP peer variables.
Status: deprecated Access: read-only
OBJECT-GROUP    

ciscoNtpFilterGroup 1.3.6.1.4.1.9.9.168.2.2.3
The NTP clock-filter variables.
Status: current Access: read-only
OBJECT-GROUP    

ciscoNtpPeersGroupRev1 1.3.6.1.4.1.9.9.168.2.2.4
The NTP peer variables.
Status: deprecated Access: read-only
OBJECT-GROUP    

ciscoNtpPeerExtGroup 1.3.6.1.4.1.9.9.168.2.2.5
The extended set of NTP peer variable(s).
Status: current Access: read-only
OBJECT-GROUP    

ciscoNtpPeersGroupRev2 1.3.6.1.4.1.9.9.168.2.2.6
The NTP peer variables.
Status: current Access: read-only
OBJECT-GROUP    

ciscoNtpSysExtGroup 1.3.6.1.4.1.9.9.168.2.2.7
The extended set of NTP system variable(s).
Status: current Access: read-only
OBJECT-GROUP    

ciscoNtpSrvNotifGroup 1.3.6.1.4.1.9.9.168.2.2.8
The collection of notifications for the NTP Server.
Status: current Access: read-only
NOTIFICATION-GROUP