Bandwidth Metrics

7/28/2019 Bandwidth Metrics

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Bandwidth Metrics and

Measurement Tools

Xin, Lu

High-Performance Computing Group

Computer Science University of Windsor


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Bandwidth Metrics

NMWG divide bandwidth into four sub-

metrics:

Bandwidth Capacity Achievable Bandwidth

Available Bandwidth

Bandwidth Utilization

FOR MORE INFO...

http://www-didc.lbl.gov/NMWG

http://www-didc.lbl.gov/NMWG/docs/measurements.pdf


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Other Metric Terms

Throughput Throughput is the same as achievable bandwidth.

Bulk Transfer Capacity (BTC) Defined by RFC 3148

BTC = data_sent / elapsed_time

The throughput of a persistent TCP transfer.

Each of these metrics can be used to describe

the entire path (end-to-end) as well as paths

link (hop-by-hop)characteristics.


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Bandwidth Capacity vs.

Achievable Bandwidth Capacity is the maximum amount of data per time unit

that the link or path has available, when there is no

competing traffic.

Achievable bandwidth is the maximum amount of dataper time unit that a link or path can provide to an

application, given the current utilization, the protocol and

operating system used, and the end-host performance

capability and load. (Throughput )

Reference: [2]


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Bandwidth Capacity vs.

Achievable Bandwidth Cont. If a path consists of several links, the link with

the minimum transmission rate determinesthe capacity of the path.

While the link with the minimum unusedcapacity limits the achievable bandwidth. i.e.

at high-speed networks, hardwareconfiguration or software load on the endhosts actually limit the bandwidth delivered tothe application.


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Available Bandwidth vs.

Bandwidth Utilization Available bandwidth is the maximum amount of

data per time unit that a link or path can provide,given the current utilization.

Utilization is the aggregate capacity currentlybeing consumed on a link or path.

Available Bandwidth =

Bandwidth Capacity Bandwidth Utilization

Reference: [2]


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BTC vs. Available Bandwidth

Available Bandwidth is the amount of usable

bandwidth without affecting cross-traffic,

whereas, the BTC is measured by sendingas much packets as possible, limiting other

traffic.

BTC is simulating steady state persistent

flow, taking considerable time and overhead.

FOR MORE INFO...

RFC 3148 : A Frame Work for Defining Empirical Bulk

Transfer Capacity Metrics


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BTC vs. Available Bandwidth

Cont.

The BTC definition assumes an ideal TCP

implementation, actually, this doesnt exist,and what BTC measured is the variant of

achievable bandwidth.

FOR MORE INFO...

RFC 3148 : A Frame Work for Defining Empirical Bulk

Transfer Capacity Metrics


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Passive vs. Active measurement

Active measurement means that the tool

actively sends probing packets into the

network. Passive measurement tools monitors the

passing traffic without interfering.

Passive measurement is appreciated,

however, less reliable than active, as it

cant extract any data pass through it.


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Receiver-based vs. Sender-

based techniques Receiver-based (end-to-end)

techniques usually use the one-

direction TCP stream to probe thepath bandwidth.

Sender-based (echo-based)

techniques force the receiver to replythe ICMP query, UDP echo or TCP-

FIN.


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Sender-based technique

Advantage:

Flexible deployment.

Clock neednt synchronized at two ends.

Disadvantage:

ICMP and UDP echo packets usually be rate-limitedor filtered out by some routers.

Round-trip is much more possibility influenced bycross-traffic than that of one-way delay

Response packets may come back through adifferent path


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Receiver-based technique

Advantage:

More accurate than sender-based technique.

Disadvantage:

Difficult to deployment.

The clock have to be synchronized at twoends.


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Bandwidth Measurement

Technology Packet Dispersion technology

packet pair and packet train

Self-Loading Periodic streams (SLOPS)

Variable Packet Size (VPS)

technology

VPS even/odd

Tailgating technique


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Packet Dispersion Technique

Cont.Bottleneck bandwidth = packet size/ t


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Cont. If sender sends the packets as one

observation sample more than two, called

packet train. Tools usually apply robust statistical

filtering techniques to find valid samples.


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Packet pair vs. packet train

Packet train is more likely to be interferedby cross traffic than packet pair.

Packet train can be used to measure thebottleneck link that is multichannel whilepacket pair cant deal with.

Packet train can reduce the limitation of

clock resolution. Sophisticated tools apply both methods in

their implementation. i.e. Pathrate


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Cont.

FOR MORE INFO...

Bprobe and cprobe http://cs-people.bu.edu/carter/tools/Tools.html

Nettest http://www-didc.lbl.gov/pipechar

Tool

Name

Active/

Passive

Method-

ology

Protocol Metrics Path/Per-

link

bprobe Active Packetpair

ICMP BandwidthCapacity Path

cprobe Active Packet

pair

ICMP Bandwidthutilization

Path

Netest Active Packetpair

UDP Bandwidthcapacity Path
http://cs-people.bu.edu/carter/tools/Tools.htmlhttp://www-didc.lbl.gov/pipecharhttp://www-didc.lbl.gov/pipecharhttp://www-didc.lbl.gov/pipecharhttp://www-didc.lbl.gov/pipecharhttp://cs-people.bu.edu/carter/tools/Tools.htmlhttp://cs-people.bu.edu/carter/tools/Tools.htmlhttp://cs-people.bu.edu/carter/tools/Tools.html


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Cont.

FOR MORE INFO...

Pathrate http://www.cc.gatech.edu/fac/Constantinos.Dovrolis

Pipecharhttp://www-didc.lbl.gov/pipechar

SProbe http://sprobe.cs.washington.edu

Pathrate Active Packet pair,packet train

UDP Bandwidthcapacity

Path

Pipechar

Active Packettrain UDPAvailable

bandwidth Per-link

Sprobe Active Packet

pair

TCP Bandwidthcapacity

Path
http://www.cc.gatech.edu/fac/Constantinos.Dovrolishttp://www-didc.lbl.gov/pipecharhttp://sprobe.cs.washington.edu/http://sprobe.cs.washington.edu/http://www-didc.lbl.gov/pipecharhttp://www-didc.lbl.gov/pipecharhttp://www-didc.lbl.gov/pipecharhttp://www.cc.gatech.edu/fac/Constantinos.Dovrolis


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Self-Loading Periodic

Streams(SLOPS) Sender sends series of packets to the sink

at the rate of larger than the bottlenecklink available bandwidth.

Every packets get a timestamp at senderside.

Compare the difference of successive

packets timestamp and their arrival timesto infer the available bandwidth.

Rate-adjustment adaptive algorithm toconverge to the available bandwidth.


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Self-Loading Periodic Streams

Cont.

FOR MORE INFO...

Pathload http://www.cc.gatech.edu/fac/Constantinos.Dovrolis

Tool

Name

Active/

Passive

Method-

ology

Protocol Metrics Path/Per

-linkpathload Active SLOPS UDP Available

bandwidthPath
http://www.cc.gatech.edu/fac/Constantinos.Dovrolishttp://www.cc.gatech.edu/fac/Constantinos.Dovrolis


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Variable Packet Size (VPS)

Technique Step1. Sender set TTL=1, send out the packet, and

wait for the ICMP TTL-exceeded packet back.

Step2. Upon receiving ICMP, estimate the RTT.

Estimate the RTT multiple times for various size

packets.The minimum RTT of various packets are

believed to be the valid sample.

Step3. The first link capacity is C=1/b , b is slope ofRTT graph.

Set the TTL=2,3n, repeat the process of step1 to 3, to

Calculate the C=1/bibi-1


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VPS technique cont.


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Even-odd VPS

The VPS probing technique is not altered,

Mathematical trick to improve reliability.

For each of the probing sizes, divide the setof samples into even and odd numbers.

Calculation is based on even-odd samples.

i.e. the even sample of link i, the odd sample

of link i+1.


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Tailgating Technique

Tailgating technique divides into two phrase:

Phase one: Like VPS probing, but for entire path

instead of per link.Phase two: (tailgating phase) The largest possible

non-fragmented packet followed by a tailgater

which is the smallest possible packet size (i.e

40 bytes). This causes the smaller packetalways queue behind the larger packet.Reference: Kevin Lai, Mary Baker Measuring Link Bandwidths

Using a Deterministic Model of Packet Delay ACM SIGCOMM 2000


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Tailgating Technique cont.

The following condition should met: The large packet should not be queued due to

cross traffic.

The large packet should have a TTL field set to L(1n).

The tailgater packet should be queued directlyafter the large packet on link L.

The tailgater packet should not queued afterhaving passing link L.


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VPS Technology

Bing http://www.cnam.fn/reseau/bing.html

Clink http://rocky.wellesley.edu/downey/clink/

Pcharhttp://www.emplyees.org/~bmah/software/pchar

Tool

Name

Active/

Passive

Method-

ology


-link

bing Active VPS ICMPBandwidth

capacity,loss, delay

Path

clink Active VPS/even-odd

UDP Bandwidthcapacity,

Loss

Path

Pchar Active VPS UDP,ICMP

Bandwidthcapacity,

Loss, delay

Per-link
http://www.cnam.fn/reseau/bing.htmlhttp://rocky.wellesley.edu/downey/clink/http://www.emplyees.org/~bmah/software/pcharhttp://www.emplyees.org/~bmah/software/pcharhttp://rocky.wellesley.edu/downey/clink/http://www.cnam.fn/reseau/bing.html


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VPS Technology Cont.

Nettimerhttp://mosquitonet.stanford.edu/~laik/project/nettimer

Pathcharftp://ftp.ee.lbl.gov/pathchar/

Tool

Name

Active/

Passive

Method-

ology


-link

Nettimer Active,Passive

VPS/tailgating

TCP Bandwidthcapacity

Per-link

pathchar Active VPS/eve

n-odd

UDP,

ICMP

Bandwidth

capacity,

Loss, delay

Per-link

FOR MORE INFO...
http://mosquitonet.stanford.edu/~laik/project/nettimerftp://ftp.ee.lbl.gov/pathchar/ftp://ftp.ee.lbl.gov/pathchar/http://mosquitonet.stanford.edu/~laik/project/nettimer


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TCP Simulation and Path Flooding

TCP simulation operates at two mode :UDP/ICMP with low TTL or ICMP echo/reply.It simulates the TCP of using slow-start

algorithm.

Path flooding method injects TCP/UDPpackets into the net as fast as possiblewithin the specific time.

To some degree, both TCP simulation andpath flooding are associated with BulkTransfer Capacity (BTC)metrics.


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Tool

Name

Active/

Passive

Method-

ology


-link

TReno Active TCPsimulation UDP,ICMPBTC Path

ttcp Active Path

flooding

TCP,

UDP

Achievable

bandwidthPath

iperf Active Pathflooding

TCP,UDP

Bandwidthcapacity,

Loss

Path

Netperf Active Path

flooding

TCP,

UDP

BTC, delay

throughputPath

TCP Simulation and Path Flooding Cont.


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TCP Simulation and Path Flooding Cont.

TReno

http://www.psc.edu/networking/treno_info.html

Iperfhttp://dast.nlanr.net/Project/Iperf

Netperf

http://www.netperf.org/netperf/NetperfPage.htmlttcp part of OS

ftp://ftp.arl.mil/pub/ttcp/
http://www.psc.edu/networking/treno_info.htmlhttp://dast.nlanr.net/Project/Iperfhttp://www.netperf.org/netperf/NetperfPage.htmlftp://ftp.arl.mil/pub/ttcp/ftp://ftp.arl.mil/pub/ttcp/http://www.netperf.org/netperf/NetperfPage.htmlhttp://dast.nlanr.net/Project/Iperfhttp://www.psc.edu/networking/treno_info.html


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Bandwidth Measurement Tools

Con.Reference :

1.http://www.caida.org/tools/

2. Bruce Lowekamp, Brain Tierney, Les Cottrell, RichardHughes-Jones, Thilo Kielmann and Martin Swany. A

Hierarchy of Network Measurements for Grid

Applications and Services Document (draft) Global Grid

Forum NMWG Feb 17, 2003.

3. Rody Schoonderwoerd Network Performance

Measurement Tools a comprehensive comparison Nov.,

2002
http://www.caida.org/tools/http://www.caida.org/tools/

Documents

Bandwidth Metrics