Internet DRAFT - draft-bmwg-dcbench-methodology
draft-bmwg-dcbench-methodology
Internet Engineering Task Force L. Avramov
Internet-Draft, Intended status: Informational Cisco Systems
Expires April 2015 J. Rapp
October 17, 2014 Hewlett-Packard
Data Center Benchmarking Methodology
draft-bmwg-dcbench-methodology-03
Abstract
The purpose of this informational document is to establish test and
evaluation methodology and measurement techniques for physical
network equipment in the data center.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
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Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 5
1.2. Methodology format and repeatability recommendation . . . . 5
2. Line Rate Testing . . . . . . . . . . . . . . . . . . . . . . . 5
2.1 Objective . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Methodology . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3 Reporting Format . . . . . . . . . . . . . . . . . . . . . . 6
3. Buffering Testing . . . . . . . . . . . . . . . . . . . . . . . 7
3.1 Objective . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2 Methodology . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3 Reporting format . . . . . . . . . . . . . . . . . . . . . . 10
4 Microburst Testing . . . . . . . . . . . . . . . . . . . . . . . 10
4.1 Objective . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.2 Methodology . . . . . . . . . . . . . . . . . . . . . . . . 10
4.3 Reporting Format . . . . . . . . . . . . . . . . . . . . . . 11
5. Head of Line Blocking . . . . . . . . . . . . . . . . . . . . . 11
5.1 Objective . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.2 Methodology . . . . . . . . . . . . . . . . . . . . . . . . 11
5.3 Reporting Format . . . . . . . . . . . . . . . . . . . . . . 13
6. Incast Stateful and Stateless Traffic . . . . . . . . . . . . . 13
6.1 Objective . . . . . . . . . . . . . . . . . . . . . . . . . 13
6.2 Methodology . . . . . . . . . . . . . . . . . . . . . . . . 13
6.3 Reporting Format . . . . . . . . . . . . . . . . . . . . . . 14
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
7.1. Normative References . . . . . . . . . . . . . . . . . . . 16
7.2. Informative References . . . . . . . . . . . . . . . . . . 16
7.3. URL References . . . . . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
Traffic patterns in the data center are not uniform and are
constantly changing. They are dictated by the nature and variety of
applications utilized in the data center. It can be largely east-west
traffic flows in one data center and north-south in another, while
some may combine both. Traffic patterns can be bursty in nature and
contain many-to-one, many-to-many, or one-to-many flows. Each flow
may also be small and latency sensitive or large and throughput
sensitive while containing a mix of UDP and TCP traffic. All of which
can coexist in a single cluster and flow through a single network
device all at the same time. Benchmarking of network devices have
long used RFC1242, RFC2432, RFC2544, RFC2889 and RFC3918. These
benchmarks have largely been focused around various latency
attributes and max throughput of the Device Under Test [DUT] being
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benchmarked. These standards are good at measuring theoretical max
throughput, forwarding rates and latency under testing conditions
however, they do not represent real traffic patterns that may affect
these networking devices.
The following provides a methodology for benchmarking Data Center DUT
including congestion scenarios, switch buffer analysis, microburst,
head of line blocking, while also using a wide mix of traffic
conditions.
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1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [6].
1.2. Methodology format and repeatability recommendation
The format used for each section of this document is the following:
-Objective
-Methodology
-Reporting Format
MUST: minimum test for the scenario described
SHOULD: recommended test for the scenario described
MAY: ideal test for the scenario described
For each test methodology described, it is key to obtain
repeatability of the results. The recommendation is to perform enough
iterations of the given test to make sure the result is accurate,
this is especially important for section 3) as the buffering testing
has been historically the least reliable.
2. Line Rate Testing
2.1 Objective
Provide at maximum rate test for the performance values for
throughput, latency and jitter. It is meant to provide the tests to
run and methodology to verify that a DUT is capable of forwarding
packets at line rate under non-congested conditions.
2.2 Methodology
A traffic generator SHOULD be connected to all ports on the DUT. Two
tests MUST be conducted: a port-pair test [RFC 2544/3918 compliant]
and also in a full mesh type of DUT test [RFC 2889/3918 compliant].
For all tests, the percentage of traffic per port capacity sent MUST
be 99.98% at most, with no PPM adjustment to ensure stressing the DUT
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in worst case conditions. Tests results at a lower rate MAY be
provided for better understanding of performance increase in terms of
latency and jitter when the rate is lower than 99.98%. The receiving
rate of the traffic needs to be captured during this test in % of
line rate.
The test MUST provide the latency values for minimum, average and
maximum, for the exact same iteration of the test.
The test MUST provide the jitter values for minimum, average and
maximum, for the exact same iteration of the test.
Alternatively when a traffic generator CAN NOT be connected to all
ports on the DUT, a snake test MUST be used for line rate testing,
excluding latency and jitter as those became then irrelevant. The
snake test consists in the following method: -connect the first and
last port of the DUT to a traffic generator-connect back to back
sequentially all the ports in between: port 2 to 3, port 4 to 5 etc
to port n-2 to port n-1; where n is the total number of ports of the
DUT-configure port 1 and 2 in the same vlan X, port 3 and 4 in the
same vlan Y, etc. port n-1 and port n in the same vlan ZZZ. This
snake test provides a capability to test line rate for Layer 2 and
Layer 3 RFC 2544/3918 in instance where a traffic generator with only
two ports is available. The latency and jitter are not to be
considered with this test.
2.3 Reporting Format
The report MUST include:
-physical layer calibration information as defined into (Placeholder
for definitions draft)
-number of ports used
-reading for throughput received in percentage of bandwidth, while
sending 99.98% of port capacity on each port, across packet size from
64 byte all the way to 9216. As guidance, an increment of 64 byte
packet size between each iteration being ideal, a 256 byte and 512
bytes being also often time used, the most common packets sizes order
for the report is: 64b,128b,256b,512b,1024b,1518b,4096,8000,9216b.
The pattern for testing can be expressed using RFC 6985 [IMIX Genome:
Specification of Variable Packet Sizes for Additional Testing]
-throughput needs to be expressed in % of total transmitted frames
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-for packet drops, they MUST be expressed in packet count value and
SHOULD be expressed in % of line rate
-for latency and jitter, values expressed in unit of time [usually
microsecond or nanosecond] reading across packet size from 64 bytes
to 9216 bytes
-for latency and jitter, provide minimum, average and maximum values.
if different iterations are done to gather the minimum, average and
maximum, it SHOULD be specified in the report along with a
justification on why the information could not have been gathered at
the same test iteration
-for jitter, a histogram describing the population of packets
measured per latency or latency buckets is RECOMMENDED
-The tests for throughput, latency and jitter MAY be conducted as
individual independent events, with proper documentation in the
report but SHOULD be conducted at the same time.
3. Buffering Testing
3.1 Objective
To measure the size of the buffer of a DUT under
typical|many|multiple conditions. Buffer architectures between
multiple DUTs can differ and include egress buffering, shared egress
buffering switch-on-chip [SoC], ingress buffering or a combination.
The test methodology covers the buffer measurement regardless of
buffer architecture used in the DUT.
3.2 Methodology
A traffic generator MUST be connected to all ports on the DUT.
The methodology for measuring buffering for a data-center switch is
based on using known congestion of known fixed packet size along with
maximum latency value measurements. The maximum latency will increase
until the first packet drop occurs. At this point, the maximum
latency value will remain constant. This is the point of inflexion of
this maximum latency change to a constant value. There MUST be
multiple ingress ports receiving known amount of frames at a known
fixed size, destined for the same egress port in order to create a
known congestion event. The total amount of packets sent from the
oversubscribed port minus one, multiplied by the packet size
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represents the maximum port buffer size at the measured inflexion
point.
1) Measure the highest buffer efficiency
First iteration: ingress port 1 sending line rate to egress port 2,
while port 3 sending a known low amount of over subscription traffic
(1% recommended) with a packet size of 64 bytes to egress port 2.
Measure the buffer size value of the number of frames sent from the
port sending the oversubscribed traffic up to the inflexion point
multiplied by the frame size.
Second iteration: ingress port 1 sending line rate to egress port 2,
while port 3 sending a known low amount of over subscription traffic
(1% recommended) with same packet size 65 bytes to egress port 2.
Measure the buffer size value of the number of frames sent from the
port sending the oversubscribed traffic up to the inflexion point
multiplied by the frame size.
Last iteration: ingress port 1 sending line rate to egress port 2,
while port 3 sending a known low amount of over subscription traffic
(1% recommended) with same packet size B bytes to egress port 2.
Measure the buffer size value of the number of frames sent from the
port sending the oversubscribed traffic up to the inflexion point
multiplied by the frame size..
When the B value is found to provide the highest buffer size, this is
the highest buffer efficiency
2) Measure maximum port buffer size
At fixed packet size B determined in 3.2.1, for a fixed default COS
value of 0 and for unicast traffic proceed with the following:
First iteration: ingress port 1 sending line rate to egress port 2,
while port 3 sending a known low amount of over subscription traffic
(1% recommended) with same packet size to the egress port 2. Measure
the buffer size value by multiplying the number of extra frames sent
by the frame size.
Second iteration: ingress port 2 sending line rate to egress port 3,
while port 4 sending a known low amount of over subscription traffic
(1% recommended) with same packet size to the egress port 3. Measure
the buffer size value by multiplying the number of extra frames sent
by the frame size.
Last iteration: ingress port N-2 sending line rate traffic to egress
port N-1, while port N sending a known low amount of over
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subscription traffic (1% recommended) with same packet size to the
egress port N Measure the buffer size value by multiplying the number
of extra frames sent by the frame size.
This test series MAY be repeated using all different COS values of
traffic and then using Multicast type of traffic, in order to find if
there is any COS impact on the buffer size.
3) Measure maximum port pair buffer sizes
First iteration: ingress port 1 sending line rate to egress port 2;
ingress port 3 sending line rate to egress port 4 etc. Ingress port
N-1 and N will respectively over subscribe at 1% of line rate egress
port 2 and port 3. Measure the buffer size value by multiplying the
number of extra frames sent by the frame size for each egress port.
Second iteration: ingress port 1 sending line rate to egress port 2;
ingress port 3 sending line rate to egress port 4 etc. Ingress port
N-1 and N will respectively over subscribe at 1% of line rate egress
port 4 and port 5. Measure the buffer size value by multiplying the
number of extra frames sent by the frame size for each egress port.
Last iteration: ingress port 1 sending line rate to egress port 2;
ingress port 3 sending line rate to egress port 4 etc. Ingress port
N-1 and N will respectively over subscribe at 1% of line rate egress
port N-3 and port N-2. Measure the buffer size value by multiplying
the number of extra frames sent by the frame size for each egress
port.
This test series MAY be repeated using all different COS values of
traffic and then using Multicast type of traffic.
4) Measure maximum DUT buffer size with many to one ports
First iteration: ingress ports 1,2,... N-1 sending each [(1/[N-
1])*99.98]+[1/[N-1]] % of line rate per port to the N egress port.
Second iteration: ingress ports 2,... N sending each [(1/[N-
1])*99.98]+[1/[N-1]] % of line rate per port to the 1 egress port.
Last iteration: ingress ports N,1,2...N-2 sending each [(1/[N-
1])*99.98]+[1/[N-1]] % of line rate per port to the N-1 egress port.
This test series MAY be repeated using all different COS values of
traffic and then using Multicast type of traffic.
Unicast traffic and then Multicast traffic SHOULD be used in order to
determine the proportion of buffer for documented selection of tests.
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Also the COS value for the packets SHOULD be provided for each test
iteration as the buffer allocation size MAY differ per COS value. It
is RECOMMENDED that the ingress and egress ports are varied in a
random, but documented fashion in multiple tests to measure the
buffer size for each port of the DUT.
3.3 Reporting format
The report MUST include:
- The packet size used for the most efficient buffer used, along
with COS value
- The maximum port buffer size for each port
- The maximum DUT buffer size
- The packet size used in the test
- The amount of over subscription if different than 1%
- The number of ingress and egress ports along with their location
on the DUT.
4 Microburst Testing
4.1 Objective
To find the maximum amount of packet bursts a DUT can sustain under
various configurations.
4.2 Methodology
A traffic generator MUST be connected to all ports on the DUT. In
order to cause congestion, two or more ingress ports MUST bursts
packets destined for the same egress port. The simplest of the setups
would be two ingress ports and one egress port (2-to-1).
The burst MUST be measure with an intensity of 100%, meaning the
burst of packets will be sent with a minimum inter-packet gap. The
amount of packet contained in the burst will be variable and increase
until there is a non-zero packet loss measured. The aggregate amount
of packets from all the senders will be used to calculate the maximum
amount of microburst the DUT can sustain.
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It is RECOMMENDED that the ingress and egress ports are varied in
multiple tests to measure the maximum microburst capacity.
The intensity of a microburst MAY be varied in order to obtain the
microburst capacity at various ingress rates.
It is RECOMMENDED that all ports on the DUT will be tested
simultaneously and in various configurations in order to understand
all the combinations of ingress ports, egress ports and intensities.
An example would be:
First Iteration: N-1 Ingress ports sending to 1 Egress Ports
Second Iterations: N-2 Ingress ports sending to 2 Egress Ports
Last Iterations: 2 Ingress ports sending to N-2 Egress Ports
4.3 Reporting Format
The report MUST include:
- The maximum value of packets received per ingress port with the
maximum burst size obtained with zero packet loss
- The packet size used in the test
- The number of ingress and egress ports along with their location
on the DUT
5. Head of Line Blocking
5.1 Objective
Head-of-line blocking (HOL blocking) is a performance-limiting
phenomenon that occurs when packets are held-up by the first packet
ahead waiting to be transmitted to a different output port. This is
defined in RFC 2889 section 5.5. Congestion Control. This section
expands on RFC 2889 in the context of Data Center Benchmarking
The objective of this test is to understand the DUT behavior under
head of line blocking scenario and measure the packet loss.
5.2 Methodology
In order to cause congestion, head of line blocking, groups of four
ports are used. A group has 2 ingress and 2 egress ports. The first
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ingress port MUST have two flows configured each going to a different
egress port. The second ingress port will congest the second egress
port by sending line rate. The goal is to measure if there is loss
for the first egress port which is not not oversubscribed.
A traffic generator MUST be connected to at least eight ports on the
DUT and SHOULD be connected using all the DUT ports.
1) Measure two groups with eight DUT ports
First iteration: measure the packet loss for two groups with
consecutive ports
The first group is composed of: ingress port 1 is sending 50% of
traffic to egress port 3 and ingress port 1 is sending 50% of traffic
to egress port 4. Ingress port 2 is sending line rate to egress port
4. Measure the amount of traffic loss for the traffic from ingress
port 1 to egress port 3.
The second group is composed of: ingress port 5 is sending 50% of
traffic to egress port 7 and ingress port 5 is sending 50% of traffic
to egress port 8. Ingress port 6 is sending line rate to egress port
8. Measure the amount of traffic loss for the traffic from ingress
port 5 to egress port 7.
Second iteration: repeat the first iteration by shifting all the
ports from N to N+1
the first group is composed of: ingress port 2 is sending 50% of
traffic to egress port 4 and ingress port 2 is sending 50% of traffic
to egress port 5. Ingress port 3 is sending line rate to egress port
5. Measure the amount of traffic loss for the traffic from ingress
port 2 to egress port 4.
the second group is composed of: ingress port 6 is sending 50% of
traffic to egress port 8 and ingress port 6 is sending 50% of traffic
to egress port 9. Ingress port 7 is sending line rate to egress port
9. Measure the amount of traffic loss for the traffic from ingress
port 6 to egress port 8.
Last iteration: when the first port of the first group is connected
on the last DUT port and the last port of the second group is
connected to the seventh port of the DUT
Measure the amount of traffic loss for the traffic from ingress port
N to egress port 2 and from ingress port 4 to egress port 6.
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2) Measure with N/4 groups with N DUT ports
First iteration: Expand to fully utilize all the DUT ports in
increments of four. Repeat the methodology of 1) with all the group
of ports possible to achieve on the device and measure for each port
group the amount of traffic loss.
Second iteration: Shift by +1 the start of each consecutive ports of
groups
Last iteration: Shift by N-1 the start of each consecutive ports of
groups and measure the traffic loss for each port group.
5.3 Reporting Format
For each test the report MUST include:
- The port configuration including the number and location of ingress
and egress ports located on the DUT
- If HOLB was observed
- Percent of traffic loss
6. Incast Stateful and Stateless Traffic
6.1 Objective
The objective of this test is to measure the effect of TCP Goodput
and latency with a mix of large and small flows. The test is designed
to simulate a mixed environment of stateful flows that require high
rates of goodput and stateless flows that require low latency.
6.2 Methodology
In order to simulate the effects of stateless and stateful traffic on
the DUT there MUST be multiple ingress ports receiving traffic
destined for the same egress port. There also MAY be a mix of
stateful and stateless traffic arriving on a single ingress port. The
simplest setup would be 2 ingress ports receiving traffic destined to
the same egress port.
One ingress port MUST be maintaining a TCP connection trough the
ingress port to a receiver connected to an egress port. Traffic in
the TCP stream MUST be sent at the maximum rate allowed by the
traffic generator. At the same time the TCP traffic is flowing
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through the DUT the stateless traffic is sent destined to a receiver
on the same egress port. The stateless traffic MUST be a microburst
of 100% intensity.
It is RECOMMENDED that the ingress and egress ports are varied in
multiple tests to measure the maximum microburst capacity.
The intensity of a microburst MAY be varied in order to obtain the
microburst capacity at various ingress rates.
It is RECOMMENDED that all ports on the DUT be used in the test.
For example:
Stateful Traffic port variation:
During Iterations number of Egress ports MAY vary as well.
First Iteration: 1 Ingress port receiving stateful TCP traffic and 1
Ingress port receiving stateless traffic destined to 1 Egress Ports
Second Iteration: 2 Ingress port receiving stateful TCP traffic and 1
Ingress port receiving stateless traffic destined to 1 Egress Ports
Last Iteration: N-2 Ingress port receiving stateful TCP traffic and 1
Ingress port receiving stateless traffic destined to 1 Egress Ports
Stateless Traffic port variation:
During Iterations number of Egress ports MAY vary as well. First
Iteration: 1 Ingress port receiving stateful TCP traffic and 1
Ingress port receiving stateless traffic destined to 1 Egress Ports
Second Iteration: 1 Ingress port receiving stateful TCP traffic and 2
Ingress port receiving stateless traffic destined to 1 Egress Ports
Last Iteration: 1 Ingress port receiving stateful TCP traffic and N-2
Ingress port receiving stateless traffic destined to 1 Egress Ports
6.3 Reporting Format
The report MUST include the following:
- Number of ingress and egress ports along with designation of
stateful or stateless.
- Stateful goodput
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- Stateless latency
7. References
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7.1. Normative References
[1] Bradner, S. "Benchmarking Terminology for Network
Interconnection Devices", RFC 1242, July 1991.
[2] Bradner, S. and J. McQuaid, "Benchmarking Methodology for
Network Interconnect Devices", RFC 2544, March 1999.
7.2. Informative References
[3] Mandeville R. and Perser J., "Benchmarking Methodology for LAN
Switching Devices", RFC 2889, August 2000.
[4] Stopp D. and Hickman B., "Methodology for IP Multicast
Benchmarking", BCP 26, RFC 3918, October 2004.
7.3. URL References
[5] Yanpei Chen, Rean Griffith, Junda Liu, Randy H. Katz, Anthony D.
Joseph, "Understanding TCP Incast Throughput Collapse in
Datacenter Networks",
http://www.eecs.berkeley.edu/~ychen2/professional/TCPIncastWREN2009.pdf".
Authors' Addresses
Lucien Avramov
Cisco Systems
170 West Tasman drive
San Jose, CA 95134
United States
Phone: +1 408 526 7686
Email: lavramov@cisco.com
Jacob Rapp
Hewlett-Packard
3000 Hanover Street
Palo Alto, CA
United States
Phone: +1 650 857 3367
Email: jacob.h.rapp@hp.com
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