Network-20181212-Juniper Device Per-Second Bandwidth

Problem

網上搜索到的 Input Bandwidth 計算方法普遍採用的思路爲取單位時間內的平均值，即 (第 [n+m] 秒的 ifHCInOctets 存量值 - 第 [n] 秒的 ifHCInOctets 存量值) / m，這個在網絡設備更新 ifHCInOctets 值的頻率和 m 秒（單位時間）存在差距的時候，就會出現異常的數值抖動和不準確。

Solution

每秒帶寬 MIB

可用 Juniper 設備的 MIB 庫查詢到直接的每秒出入帶寬，如下：

1. ifIn1SecRate

• oid: 1.3.6.1.4.1.2636.3.3.1.1.1
• The number of bits per second (bps), delivered by this (sub-)layer to its next higher (sub-)layer.

2. ifIn1SecOctets

• oid: 1.3.6.1.4.1.2636.3.3.1.1.2
• The number of octets per second (Bps, Bytes per second), delivered by this (sub-)layer to its next higher (sub-)layer.

3. ifHCIn1SecRate

• oid: 1.3.6.1.4.1.2636.3.3.1.1.7
• The number of bits per second (bps), delivered by this (sub-)layer to its next higher (sub-)layer. This object is a 64 bit version of ifIn1SecRate.

4. ifHCIn1SecOctets

• oid: 1.3.6.1.4.1.2636.3.3.1.1.34
• The number of bytes per second (Bps), delivered by this (sub-)layer to its next higher (sub-)layer. This object is a 64 bit version of ifIn1SecOctets.

Oid Sample with netsnmp Python Library

import netsnmp

#---------------------------------------------------------------------------------------------
# deviceip		設備 ip
# interface	端口 index 號
#				*	形如以下：
#				*		Interface index: 166, SNMP ifIndex: 612
#				*		Logical interface et-2/3/0.0 (Index 353) (SNMP ifIndex 523)
#				*	則，取 612 爲參數 interface 的值
#---------------------------------------------------------------------------------------------

def getinfo(deviceip, interface):
	"""get oid info"""
	session = netsnmp.Session(Version = 3, DestHost = deviceip, SecLevel = authPriv, SecName = securityname, PrivProto = privacyprotocol, PrivPass = privacyphrase, AuthProto = authenticationprotocol, AuthPass = authenticationphrase)
	varList = netsnmp.VarList(netsnmp.Varbind("ifDescr." + interface), netsnmp.Varbind(".1.3.6.1.4.1.2636.3.3.1.1.7." + interface), netsnmp.Varbind(".1.3.6.1.4.1.2636.3.3.1.1.8." + interface))
	values = session.get(varList)
	return values
	

Extends

Oid 數據類型

1. Integer 整型
   Signed 32bit Integer (values between -2147483648 and 2147483647). 有符號32位整數（值範圍: -2147483648 - [phone]）
2. Integer32
   Same as Integer. 與Integer相同。
3. UInteger32
   Unsigned 32bit Integer (values between 0 and 4294967295). 無符號32位整數（值範圍：0－4294967295）.
4. Octet String
   Arbitrary binary or textual data, typically limited to 255 characters in length. 任意二進制或文本數據，通常長度限制在255個字符內。
5. Object Identifier
   An OID. 一個OID。
6. Bit String
   Represents an enumeration of named bits. This is an unsigned datatype. 表示取名的位的枚舉。這是一個無符號的數據類型。
7. IpAddress
   An IP address. 一個IP地址。
8. Counter32
   Represents a non-negative integer which monotonically increases until it reaches a maximum value of 32bits-1 (4294967295 dec), when it wraps around and starts increasing again from zero. 表示一個非負的整數（可遞增到32位最大值－1），然後恢復並從0開始遞增。
9. Counter64
   Same as Counter32 but has a maximum value of 64bits-1. 與Counter32相同，最大值爲64位的最大值－1。
10. Gauge32
    Represents an unsigned integer, which may increase or decrease, but shall never exceed a maximum value. 表示無符號整數，可增加或減少，但是不超過最大值。
11. TimeTicks
    Represents an unsigned integer which represents the time, modulo 2ˆ32 (4294967296 dec), in hundredths of a second between two epochs. 表示代表數據的一個無符號整數，2^32取模（4294967296），兩個值之間爲百分之一秒。
12. Opaque
    Provided solely for backward-compatibility, its no longer used. 提供向下兼容，不再使用的數據類型
13. NsapAddress
    Represents an OSI address as a variable-length OCTET STRING. 表示一個用變長八進制字符窗表示的OSI地址。

不同 Oid 數據類型 Sample

SNMPv2-SMI::enterprises.2636.3.3.1.1.2.111 = Gauge32: 7571581
SNMPv2-SMI::enterprises.2636.3.3.1.1.7.111 = Counter64: 60572648

這裏的 Gauge32, Counter64 其實就是說明對應着不同的數據類型，和編程語言中理解的沒啥大概念上的不同。（便於理解所謂的 64 bit 是啥意思，其實就是簡單的一種數據類型罷了）

Reference

1. Juniper Official MIB Search-ifIn1SecOctets
2. SNMP介紹，OID及MIB庫