RRDTool & SmokepingPhilippines Network Operators Group, March 2018Jonathan BrewerTelco2 LimitedNew Zealand

ObjectivesParticipants will understand the basics of:

• Time Series Data• Round-Robin Databases• Latency, Loss, & Jitter• Smokeping for Performance Monitoring

Time Series Data• Point in Time Measurement• Taken at Equal Intervals• For Example

• Tide Height• Temperature• Round-Trip Latency

• High Resolution Requires Massive Storage

Round-Robin Database• Also Known as Circular Buffer, Cyclic Buffer or Ring

Buffer• Provides a Fixed Size Storage Bucket• When it's Out of Room, Old Data Disappears

• Old Data can be Overwritten• Old Data can be Compressed

• Examples include Data Turbine & RRDTool

RRDTool• Originated from MRTG• Written in Perl by Tobias Oetiker • Used for networks, engineering, and science• Consolidates data when buffer is full

Latency• The time it takes to move information across a

network• Typically considered as a "Round Trip Time" or RTT• More Latency = More Slow!• Most people notice latency above 280 ms

People Notice Latency

Distance = Latency

Image from The Wonder Network: https://wondernetwork.com/pings

Loss• Packet loss can occur in several situations

• Interference problems with RF transmissions• Discards by traffic policers• Interface errors• Full buffers

• Most of the time loss makes things slower

Imact of Loss on TCP

Image from Šošić & Stojanović: http://www.gisss.matf.bg.ac.rs/GISS/network.html

Jitter• Also Known as Inter-Packet Delay Variation• Is a Measure of How Evenly Packets are Transmitted

Time 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Low Jitter

A B C D E F G H I J

Medium Jitter

A B C D E F G H I J

High Jitter

A B C D E F G H

Impact of Jitter on Voice• Jitter buffers in VoIP Help Make Conversations

Smooth• Digital Signal Processing can "Fill In" Gaps Caused by

Medium Jitter• High Jitter Causes Buffers to Fill Up & Packets to be

Discarded• Discarded Packets Lead to Pauses and Dropouts in

Voice Conversations

Smokeping• Best Known for Helping Monitor ICMP Latency Loss

& Jitter• Can also Monitor DHS, HTTP, LDAP, and Other

Services• Also Written in Perl by Tobias Oetiker • Uses RRDTool + FPing + Apache + Perl + CGI

Hoes does it work?• By default, it uses fping to measure ICMP

performance• 20 packets are sent out every five minutes• Their performance is recorded in an RRD• Graphs are drawn to show their performance

Smokeping

An example of Smokeping showing the pings & the smoke. What's going on here?

Smokeping

These charts are the same size as the higher resolution ones What's going on here?

Multi-Variable Smokeping

Multiple server DNS query response time chart from https://oss.oetiker.ch/smokeping-demo/?target=multi.DNSJ

Smokeping Notes• Smokeping can easily monitor a small network from

a Raspberry Pi• Changing the time resolution of an RRD once it's

established is not possible.• It is possible to extract information from Smokeping

and save to SQL• High resolution data (every 30 seconds) can be very

useful for diagnosis

RRDTool & SmokepingPhilippines Network Operators Group, March 2018Jonathan BrewerTelco2 LimitedNew Zealand