ABwE: Available Bandwidth Estimator
Jiri Navratil R. Les. Cottrell
Stanford Linear Accelerator Center (SLAC),
2575 Sand Hill Road, Menlo Park, California 94025
jiri@slac.stanford.edu, cottrell@slac.stanford.edu

ABwE: Available Bandwidth Estimator

Introduction (motivation, needs,..)

Basic principles

Path characteristics and the examples of packet pair dispersion delays

Bandwidth estimation

ABwE versus Iperf

Conclusions

Introduction 1

The HEP community is increasingly dependent on networking as internal cooperation grows (needs transfer huge amount of data between experimental sites as SLAC,CERN,etc. and home institutes spread over the world)

Our main task is to provide the physicists reliable access to the network (and the integral part of this activity is NETWORK MONITORING)

We have several monitoring system in operation (active: as ping or iperf, and passive: reading SNMP counts or using netflows data

Introduction 2

Network administrators and the users need to know RTT,losses, routing path, and estimations of available bandwidth to our partners

Currently we have such information in limited sampling periods.The big question is. Do we have valid information if we do measurements once per 90 minutes and can we do measurements with tools as Iperf or to transfer the test files more frequently? Probably no.

We need a tool that could be used in continuous mode 24 hours a day 7 days a week which can quickly and non intrusively detect changes on multiple path

Specification

Tool based on dispersion techniques which doesn’t pollute Internet (and overload an entry point to the Internet) with huge amount of testing packets

Get the result from one path during in a few seconds and produce results that could be easily preprocessed by graphical tools or enter to other systems (prediction, warning etc.)

Easily configurable and manageable from one site

We evaluated several tools using dispersion techniques but none of them in their current implementation met our demands.(Some of them were slow,some of them failed for high capacity paths and some of them were just technically too complicated).

Basic principles of ABwE

ABwE is based on the simplest way of probing (using only Packet pairs)

Evaluation is based on detailed technical analysis of how the packets pass via queuing devices

Complete path is cascade of queuing devices with different capacities

The separation of probing packets will happen even if there is no cross traffic

The final dispersion PP1 and PP2 is the results of superposition of many factors

How we measure the dispersion time

Using Netdyn package (package from University of Maryland 1991)

20 packets pairs probes for each path

Probes are repeated with the period 20 msec and once a minute per each path. Set of 20 probes is called bunch. The bunch is evaluated as one statistical set of measurements.

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Iperf versus ABwE
(few unclear points)

How to configure Iperf to achieve maximum performance in changing environment

( difference ~ 10 - 100 %)

Limitation on the Entry-points to the Internet (SLAC 622Mbits, customer load (10% - 40% )

Machine performance (400-550 Mbits)

Iperf aggressiveness (it suppress bandwidth of other running applications) and reports all what Iperf transferred

Synchronization problem to avoid dependency

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Conclusions

We have demonstrated several network analysis and

a new method for monitoring ABw and bottleneck capacity in the range several Mbits to 1000 Mbits

ABwE is a non intrusive method which can be run in

a continuous mode 24 hours a day 7 days a week

It can detect changes in the path capacity based on heavy traffic and also discover dramatic changes in routing. The usefulness of ABwE has been proven several times since last summer

Unfortunately, ABwE still doesn’t exists as a publicly used tool


	Introduction (motivation, needs,..)
	Basic principles
	Path characteristics and the examples of packet pair dispersion delays
	Bandwidth estimation
	ABwE versus Iperf
	Conclusions


	The HEP community is increasingly dependent on networking as internal cooperation grows (needs transfer huge amount of data between experimental sites as SLAC,CERN,etc. and home institutes spread over the world)

	Our main task is to provide the physicists reliable access to the network (and the integral part of this activity is NETWORK MONITORING)

	We have several monitoring system in operation (active: as ping or iperf, and passive: reading SNMP counts or using netflows data


	Network administrators and the users need to know RTT,losses, routing path, and estimations of available bandwidth to our partners

	Currently we have such information in limited sampling periods.The big question is. Do we have valid information if we do measurements once per 90 minutes and can we do measurements with tools as Iperf or to transfer the test files more frequently? Probably no.

	We need a tool that could be used in continuous mode 24 hours a day 7 days a week which can quickly and non intrusively detect changes on multiple path


	Tool based on dispersion techniques which doesn’t pollute Internet (and overload an entry point to the Internet) with huge amount of testing packets
	Get the result from one path during in a few seconds and produce results that could be easily preprocessed by graphical tools or enter to other systems (prediction, warning etc.)
	Easily configurable and manageable from one site

	We evaluated several tools using dispersion techniques but none of them in their current implementation met our demands.(Some of them were slow,some of them failed for high capacity paths and some of them were just technically too complicated).


	ABwE is based on the simplest way of probing (using only Packet pairs)
	Evaluation is based on detailed technical analysis of how the packets pass via queuing devices
	Complete path is cascade of queuing devices with different capacities
	The separation of probing packets will happen even if there is no cross traffic
	The final dispersion PP1 and PP2 is the results of superposition of many factors


	Using Netdyn package (package from University of Maryland 1991)
	20 packets pairs probes for each path
	Probes are repeated with the period 20 msec and once a minute per each path. Set of 20 probes is called bunch. The bunch is evaluated as one statistical set of measurements.


	How to configure Iperf to achieve maximum performance in changing environment
	( difference ~ 10 - 100 %)
	Limitation on the Entry-points to the Internet (SLAC 622Mbits, customer load (10% - 40% )
	Machine performance (400-550 Mbits)
	Iperf aggressiveness (it suppress bandwidth of other running applications) and reports all what Iperf transferred
	Synchronization problem to avoid dependency


	We have demonstrated several network analysis and
	a new method for monitoring ABw and bottleneck capacity in the range several Mbits to 1000 Mbits

	ABwE is a non intrusive method which can be run in
	a continuous mode 24 hours a day 7 days a week

	It can detect changes in the path capacity based on heavy traffic and also discover dramatic changes in routing. The usefulness of ABwE has been proven several times since last summer

	Unfortunately, ABwE still doesn’t exists as a publicly used tool