snmp - TimeTicks 和 TimeInterval SMI 类型之间的区别

Question

RFC 2578“管理信息结构版本 2 (SMIv2)”包含类型 TimeTicks，定义为 IMPLICIT INTEGER (0..4294967295) 并描述为“表示时间的非负整数，以 2^32 为模(十进制为 4294967296)，以两个纪元之间的百分之一秒为单位。

RFC 2579“SMIv2 的文本约定”包含一个类型 TimeInterval，定义为 TEXTUAL-CONVENTION 和 SYNTAX INTEGER (0..2147483647) 并描述为“一段时间，以 0.01 秒为单位测量。”。

我看不出这两者之间的区别，或者换句话说，为什么在有 TimeTicks 时需要 TimeInterval(除了可能出于历史原因)。如果存在实际差异，它们是什么以及我应该使用什么类型？

Answer 1

我认为 TimeTicks 旨在通过引用两个已知纪元来表示时间点，而 TimeInterval 表示没有引用的时间段。

对于TimeTicks，注意定义的最后一句:

The TimeTicks type represents a non-negative integer which represents the time, modulo 2^32 (4294967296 decimal), in hundredths of a second between two epochs. When objects are defined which use this ASN.1 type, the description of the object identifies both of the reference epochs.

下一段描述了 TimeStamp 如何定义这两个时期:

For example, [3] defines the TimeStamp textual convention which is based on the TimeTicks type. With a TimeStamp, the first reference epoch is defined as the time when sysUpTime [5] was zero, and the second reference epoch is defined as the current value of sysUpTime.

TimeInterval 不是用来计算时间的，而是用来定义一个时间长度的。从 CISCO 查看此对象使用 TimeInterval:

snmpTargetAddrTimeout OBJECT-TYPE
       SYNTAX      TimeInterval
       MAX-ACCESS  read-create
       STATUS      current
       DESCRIPTION           "This object should reflect the expected maximum round
            trip time for communicating with the transport address
            defined by this row.  When a message is sent to this
            address, and a response (if one is expected) is not
            received within this time period, an implementation
            may assume that the response will not be delivered.
            Note that the time interval that an application waits
            for a response may actually be derived from the value
            of this object.  The method for deriving the actual time
            interval is implementation dependent.  One such method
            is to derive the expected round trip time based on a
            particular retransmission algorithm and on the number
            of timeouts which have occurred.  The type of message may
            also be considered when deriving expected round trip
            times for retransmissions.  For example, if a message is
            being sent with a securityLevel that indicates both
            authentication and privacy, the derived value may be
            increased to compensate for extra processing time spent
            during authentication and encryption processing.
"
       DEFVAL { 1500 }
       ::= { snmpTargetAddrEntry 4 }