Internet DRAFT - draft-ietf-bmwg-dcbench-terminology
draft-ietf-bmwg-dcbench-terminology
Internet Engineering Task Force L. Avramov
INTERNET-DRAFT, Intended status: Informational Google
Expires: December 24,2017 J. Rapp
June 22, 2017 VMware
Data Center Benchmarking Terminology
draft-ietf-bmwg-dcbench-terminology-19
Abstract
The purpose of this informational document is to establish definitions
and describe measurement techniques for data center benchmarking, as
well as it is to introduce new terminologies applicable to performance
evaluations of data center network equipment. This document establishes
the important concepts for benchmarking network switches and routers in
the data center and, is a pre-requisite to the test methodology
publication [draft-ietf-bmwg-dcbench-methodology]. Many of these terms
and methods may be applicable to network equipment beyond this
publication's scope as the technologies originally applied in the data
center are deployed elsewhere.
Status of this Memo
This Internet-Draft is submitted in full conformance with the provisions
of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF). Note that other groups may also distribute working
documents as Internet-Drafts. The list of current Internet-Drafts is at
http://datatracker.ietf.org/drafts/current.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference material
or to cite them other than as "work in progress."
Copyright Notice
Copyright (c) 2017 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 (http://trustee.ietf.org/license-info) in
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effect on the date of publication of this document. Please review these
documents carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this document
must include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
1.2. Definition format . . . . . . . . . . . . . . . . . . . . . 4
2. Latency . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.3 Measurement Units . . . . . . . . . . . . . . . . . . . . . 6
3 Jitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1 Definition . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3 Measurement Units . . . . . . . . . . . . . . . . . . . . . 7
4 Physical Layer Calibration . . . . . . . . . . . . . . . . . . . 7
4.1 Definition . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.2 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.3 Measurement Units . . . . . . . . . . . . . . . . . . . . . 8
5 Line rate . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.1 Definition . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.2 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.3 Measurement Units . . . . . . . . . . . . . . . . . . . . . 10
6 Buffering . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.1 Buffer . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.1.1 Definition . . . . . . . . . . . . . . . . . . . . . . . 11
6.1.2 Discussion . . . . . . . . . . . . . . . . . . . . . . . 12
6.1.3 Measurement Units . . . . . . . . . . . . . . . . . . . 12
6.2 Incast . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6.2.1 Definition . . . . . . . . . . . . . . . . . . . . . . . 13
6.2.2 Discussion . . . . . . . . . . . . . . . . . . . . . . . 14
6.2.3 Measurement Units . . . . . . . . . . . . . . . . . . . 14
7 Application Throughput: Data Center Goodput . . . . . . . . . . 14
7.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 14
7.2. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 14
7.3. Measurement Units . . . . . . . . . . . . . . . . . . . . . 15
8. Security Considerations . . . . . . . . . . . . . . . . . . . 16
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
10.1. Normative References . . . . . . . . . . . . . . . . . . 16
10.2. Informative References . . . . . . . . . . . . . . . . . 17
10.3. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 17
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Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
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 (server to server inside the data center) in one data
center and north-south (outside of the data center to server) 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.
One or more of these may coexist in a single cluster and flow through
a single network device simultaneously. 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 being
benchmarked. These standards are good at measuring theoretical max
throughput, forwarding rates and latency under testing conditions,
but they do not represent real traffic patterns that may affect these
networking devices. The data center networking devices covered are
switches and routers.
Currently, typical data center networking devices are characterized
by:
-High port density (48 ports of more)
-High speed (up to 100 GB/s currently per port)
-High throughput (line rate on all ports for Layer 2 and/or Layer 3)
-Low latency (in the microsecond or nanosecond range)
-Low amount of buffer (in the MB range per networking device)
-Layer 2 and Layer 3 forwarding capability (Layer 3 not mandatory)
The following document defines a set of definitions, metrics and
terminologies including congestion scenarios, switch buffer analysis
and redefines basic definitions in order to represent a wide mix of
traffic conditions. The test methodologies are defined in [draft-
ietf-bmwg-dcbench-methodology].
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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 [RFC2119].
1.2. Definition format
Term to be defined. (e.g., Latency)
Definition: The specific definition for the term.
Discussion: A brief discussion about the term, its application and
any restrictions on measurement procedures.
Measurement Units: Methodology for the measure and units used to
report measurements of this term, if applicable.
2. Latency
2.1. Definition
Latency is a the amount of time it takes a frame to transit the
Device Under Test (DUT). Latency is measured in units of time
(seconds, milliseconds, microseconds and so on). The purpose of
measuring latency is to understand the impact of adding a device in
the communication path.
The Latency interval can be assessed between different combinations
of events, regardless of the type of switching device (bit forwarding
aka cut-through, or store-and-forward type of device). [RFC1242]
defined Latency differently for each of these types of devices.
Traditionally the latency measurement definitions are:
FILO (First In Last Out)
The time interval starting when the end of the first bit of the input
frame reaches the input port and ending when the last bit of the
output frame is seen on the output port.
FIFO (First In First Out):
The time interval starting when the end of the first bit of the input
frame reaches the input port and ending when the start of the first
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bit of the output frame is seen on the output port. [RFC1242] Latency
for bit forwarding devices uses these events.
LILO (Last In Last Out):
The time interval starting when the last bit of the input frame
reaches the input port and the last bit of the output frame is seen
on the output port.
LIFO (Last In First Out):
The time interval starting when the last bit of the input frame
reaches the input port and ending when the first bit of the output
frame is seen on the output port. [RFC1242] Latency for bit
forwarding devices uses these events.
Another possibility to summarize the four different definitions above
is to refer to the bit position as they normally occur: Input to
output.
FILO is FL (First bit Last bit). FIFO is FF (First bit First bit).
LILO is LL (Last bit Last bit). LIFO is LF (Last bit First bit).
This definition explained in this section in context of data center
switching benchmarking is in lieu of the previous definition of
Latency defined in RFC 1242, section 3.8 and is quoted here:
For store and forward devices: The time interval starting when the
last bit of the input frame reaches the input port and ending when
the first bit of the output frame is seen on the output port.
For bit forwarding devices: The time interval starting when the end
of the first bit of the input frame reaches the input port and ending
when the start of the first bit of the output frame is seen on the
output port.
To accommodate both types of network devices and hybrids of the two
types that have emerged, switch Latency measurements made according
to this document MUST be measured with the FILO events. FILO will
include the latency of the switch and the latency of the frame as
well as the serialization delay. It is a picture of the 'whole'
latency going through the DUT. For applications which are latency
sensitive and can function with initial bytes of the frame, FIFO (or
RFC 1242 Latency for bit forwarding devices) MAY be used. In all
cases, the event combination used in Latency measurement MUST be
reported.
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2.2 Discussion
As mentioned in section 2.1, FILO is the most important measuring
definition.
Not all DUTs are exclusively cut-through or store-and-forward. Data
Center DUTs are frequently store-and-forward for smaller packet sizes
and then adopting a cut-through behavior. The change of behavior
happens at specific larger packet sizes. The value of the packet size
for the behavior to change MAY be configurable depending on the DUT
manufacturer. FILO covers all scenarios: Store-and-forward or cut-
through. The threshold of behavior change does not matter for
benchmarking since FILO covers both possible scenarios.
LIFO mechanism can be used with store forward type of switches but
not with cut-through type of switches, as it will provide negative
latency values for larger packet sizes because LIFO removes the
serialization delay. Therefore, this mechanism MUST NOT be used when
comparing latencies of two different DUTs.
2.3 Measurement Units
The measuring methods to use for benchmarking purposes are as
follows:
1) FILO MUST be used as a measuring method, as this will include the
latency of the packet; and today the application commonly needs to
read the whole packet to process the information and take an action.
2) FIFO MAY be used for certain applications able to proceed the data
as the first bits arrive, as for example for a Field-Programmable
Gate Array (FPGA)
3) LIFO MUST NOT be used, because it subtracts the latency of the
packet; unlike all the other methods.
3 Jitter
3.1 Definition
Jitter in the data center context is synonymous with the common term
Delay variation. It is derived from multiple measurements of one-way
delay, as described in RFC 3393. The mandatory definition of Delay
Variation is the Packet Delay Variation (PDV) from section 4.2 of
[RFC5481]. When considering a stream of packets, the delays of all
packets are subtracted from the minimum delay over all packets in the
stream. This facilitates assessment of the range of delay variation
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(Max - Min), or a high percentile of PDV (99th percentile, for
robustness against outliers).
When First-bit to Last-bit timestamps are used for Delay measurement,
then Delay Variation MUST be measured using packets or frames of the
same size, since the definition of latency includes the serialization
time for each packet. Otherwise if using First-bit to First-bit, the
size restriction does not apply.
3.2 Discussion
In addition to PDV Range and/or a high percentile of PDV, Inter-
Packet Delay Variation (IPDV) as defined in section 4.1 of [RFC5481]
(differences between two consecutive packets) MAY be used for the
purpose of determining how packet spacing has changed during
transfer, for example, to see if packet stream has become closely-
spaced or "bursty". However, the Absolute Value of IPDV SHOULD NOT be
used, as this collapses the "bursty" and "dispersed" sides of the
IPDV distribution together.
3.3 Measurement Units
The measurement of delay variation is expressed in units of seconds.
A PDV histogram MAY be provided for the population of packets
measured.
4 Physical Layer Calibration
4.1 Definition
The calibration of the physical layer consists of defining and
measuring the latency of the physical devices used to perform tests
on the DUT.
It includes the list of all physical layer components used as listed
here after:
-Type of device used to generate traffic / measure traffic
-Type of line cards used on the traffic generator
-Type of transceivers on traffic generator
-Type of transceivers on DUT
-Type of cables
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-Length of cables
-Software name, and version of traffic generator and DUT
-List of enabled features on DUT MAY be provided and is recommended
(especially the control plane protocols such as Link Layer Discovery
Protocol, Spanning-Tree etc.). A comprehensive configuration file MAY
be provided to this effect.
4.2 Discussion
Physical layer calibration is part of the end to end latency, which
should be taken into acknowledgment while evaluating the DUT. Small
variations of the physical components of the test may impact the
latency being measured, therefore they MUST be described when
presenting results.
4.3 Measurement Units
It is RECOMMENDED to use all cables of: The same type, the same
length, when possible using the same vendor. It is a MUST to document
the cables specifications on section 4.1 along with the test results.
The test report MUST specify if the cable latency has been removed
from the test measures or not. The accuracy of the traffic generator
measure MUST be provided (this is usually a value in the 20ns range
for current test equipment).
5 Line rate
5.1 Definition
The transmit timing, or maximum transmitted data rate is controlled
by the "transmit clock" in the DUT. The receive timing (maximum
ingress data rate) is derived from the transmit clock of the
connected interface.
The line rate or physical layer frame rate is the maximum capacity to
send frames of a specific size at the transmit clock frequency of the
DUT.
The term "nominal value of Line Rate" defines the maximum speed
capability for the given port; for example 1GE, 10GE, 40GE, 100GE
etc.
The frequency ("clock rate") of the transmit clock in any two
connected interfaces will never be precisely the same; therefore, a
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tolerance is needed. This will be expressed by Parts Per Million
(PPM) value. The IEEE standards allow a specific +/- variance in the
transmit clock rate, and Ethernet is designed to allow for small,
normal variations between the two clock rates. This results in a
tolerance of the line rate value when traffic is generated from a
testing equipment to a DUT.
Line rate SHOULD be measured in frames per second.
5.2 Discussion
For a transmit clock source, most Ethernet switches use "clock
modules" (also called "oscillator modules") that are sealed,
internally temperature-compensated, and very accurate. The output
frequency of these modules is not adjustable because it is not
necessary. Many test sets, however, offer a software-controlled
adjustment of the transmit clock rate. These adjustments SHOULD be
used to compensate the test equipment in order to not send more than
the line rate of the DUT.
To allow for the minor variations typically found in the clock rate
of commercially-available clock modules and other crystal-based
oscillators, Ethernet standards specify the maximum transmit clock
rate variation to be not more than +/- 100 PPM (parts per million)
from a calculated center frequency. Therefore a DUT must be able to
accept frames at a rate within +/- 100 PPM to comply with the
standards.
Very few clock circuits are precisely +/- 0.0 PPM because:
1.The Ethernet standards allow a maximum of +/- 100 PPM (parts per
million) variance over time. Therefore it is normal for the frequency
of the oscillator circuits to experience variation over time and over
a wide temperature range, among external factors.
2.The crystals, or clock modules, usually have a specific +/- PPM
variance that is significantly better than +/- 100 PPM. Often times
this is +/- 30 PPM or better in order to be considered a
"certification instrument".
When testing an Ethernet switch throughput at "line rate", any
specific switch will have a clock rate variance. If a test set is
running +1 PPM faster than a switch under test, and a sustained line
rate test is performed, a gradual increase in latency and eventually
packet drops as buffers fill and overflow in the switch can be
observed. Depending on how much clock variance there is between the
two connected systems, the effect may be seen after the traffic
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stream has been running for a few hundred microseconds, a few
milliseconds, or seconds. The same low latency and no-packet-loss can
be demonstrated by setting the test set link occupancy to slightly
less than 100 percent link occupancy. Typically 99 percent link
occupancy produces excellent low-latency and no packet loss. No
Ethernet switch or router will have a transmit clock rate of exactly
+/- 0.0 PPM. Very few (if any) test sets have a clock rate that is
precisely +/- 0.0 PPM.
Test set equipment manufacturers are well-aware of the standards, and
allow a software-controlled +/- 100 PPM "offset" (clock-rate
adjustment) to compensate for normal variations in the clock speed of
DUTs. This offset adjustment allows engineers to determine the
approximate speed the connected device is operating, and verify that
it is within parameters allowed by standards.
5.3 Measurement Units
"Line Rate" can be measured in terms of "Frame Rate":
Frame Rate = Transmit-Clock-Frequency / (Frame-Length*8 + Minimum_Gap
+ Preamble + Start-Frame Delimiter)
Minimum_Gap represents the inter frame gap. This formula "scales up"
or "scales down" to represent 1 GB Ethernet, or 10 GB Ethernet and so
on.
Example for 1 GB Ethernet speed with 64-byte frames: Frame Rate =
1,000,000,000 /(64*8 + 96 + 56 + 8) Frame Rate = 1,000,000,000 / 672
Frame Rate = 1,488,095.2 frames per second.
Considering the allowance of +/- 100 PPM, a switch may "legally"
transmit traffic at a frame rate between 1,487,946.4 FPS and
1,488,244 FPS. Each 1 PPM variation in clock rate will translate to
a 1.488 frame-per-second frame rate increase or decrease.
In a production network, it is very unlikely to see precise line rate
over a very brief period. There is no observable difference between
dropping packets at 99% of line rate and 100% of line rate.
Line rate can be measured at 100% of line rate with a -100PPM
adjustment.
Line rate SHOULD be measured at 99,98% with 0 PPM adjustment.
The PPM adjustment SHOULD only be used for a line rate type of
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measurement.
6 Buffering
6.1 Buffer
6.1.1 Definition
Buffer Size: The term buffer size represents the total amount of
frame buffering memory available on a DUT. This size is expressed in
B (byte); KB (kilobyte), MB (megabyte) or GB (gigabyte). When the
buffer size is expressed it SHOULD be defined by a size metric stated
above. When the buffer size is expressed, an indication of the frame
MTU used for that measurement is also necessary as well as the cos
(class of service) or dscp (differentiated services code point) value
set; as often times the buffers are carved by quality of service
implementation. Please refer to the buffer efficiency section for
further details.
Example: Buffer Size of DUT when sending 1518 byte frames is 18 MB.
Port Buffer Size: The port buffer size is the amount of buffer for a
single ingress port, egress port or combination of ingress and egress
buffering location for a single port. The reason for mentioning the
three locations for the port buffer is because the DUT buffering
scheme can be unknown or untested, and so knowing the buffer location
helps clarify the buffer architecture and consequently the total
buffer size. The Port Buffer Size is an informational value that MAY
be provided from the DUT vendor. It is not a value that is tested by
benchmarking. Benchmarking will be done using the Maximum Port Buffer
Size or Maximum Buffer Size methodology.
Maximum Port Buffer Size: In most cases, this is the same as the Port
Buffer Size. In certain switch architecture called SoC (switch on
chip), there is a port buffer and a shared buffer pool available for
all ports. The Maximum Port Buffer Size , in terms of an SoC buffer,
represents the sum of the port buffer and the maximum value of shared
buffer allowed for this port, defined in terms of B (byte), KB
(kilobyte), MB (megabyte), or GB (gigabyte). The Maximum Port Buffer
Size needs to be expressed along with the frame MTU used for the
measurement and the cos or dscp bit value set for the test.
Example: A DUT has been measured to have 3KB of port buffer for 1518
frame size packets and a total of 4.7 MB of maximum port buffer for
1518 frame size packets and a cos of 0.
Maximum DUT Buffer Size: This is the total size of Buffer a DUT can
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be measured to have. It is, most likely, different than than the
Maximum Port Buffer Size. It can also be different from the sum of
Maximum Port Buffer Size. The Maximum Buffer Size needs to be
expressed along with the frame MTU used for the measurement and along
with the cos or dscp value set during the test.
Example: A DUT has been measured to have 3KB of port buffer for 1518
frame size packets and a total of 4.7 MB of maximum port buffer for
1518 B frame size packets. The DUT has a Maximum Buffer Size of 18 MB
at 1500 B and a cos of 0.
Burst: The burst is a fixed number of packets sent over a percentage
of linerate of a defined port speed. The amount of frames sent are
evenly distributed across the interval, T. A constant, C, can be
defined to provide the average time between two consecutive packets
evenly spaced.
Microburst: It is a burst. A microburst is when packet drops occur
when there is not sustained or noticeable congestion upon a link or
device. A characterization of microburst is when the Burst is not
evenly distributed over T, and is less than the constant C [C=
average time between two consecutive packets evenly spaced out].
Intensity of Microburst: This is a percentage, representing the level
of microburst between 1 and 100%. The higher the number the higher
the microburst is. I=[1-[ (TP2-Tp1)+(Tp3-Tp2)+....(TpN-Tp(n-1) ] /
Sum(packets)]]*100
The above definitions are not meant to comment on the ideal sizing of
a buffer, rather on how to measure it. A larger buffer is not
necessarily better and can cause issues with buffer bloat.
6.1.2 Discussion
When measuring buffering on a DUT, it is important to understand the
behavior for each and all ports. This provides data for the total
amount of buffering available on the switch. The terms of buffer
efficiency here helps one understand the optimum packet size for the
buffer, or the real volume of the buffer available for a specific
packet size. This section does not discuss how to conduct the test
methodology; instead, it explains the buffer definitions and what
metrics should be provided for a comprehensive data center device
buffering benchmarking.
6.1.3 Measurement Units
When Buffer is measured:
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-The buffer size MUST be measured
-The port buffer size MAY be provided for each port
-The maximum port buffer size MUST be measured
-The maximum DUT buffer size MUST be measured
-The intensity of microburst MAY be mentioned when a microburst test
is performed
-The cos or dscp value set during the test SHOULD be provided
6.2 Incast
6.2.1 Definition
The term Incast, very commonly utilized in the data center, refers to
the traffic pattern of many-to-one or many-to-many traffic patterns.
It measures the number of ingress and egress ports and the level of
synchronization attributed, as defined in this section. Typically in
the data center it would refer to many different ingress server ports
(many), sending traffic to a common uplink (many-to-one), or multiple
uplinks (many-to-many). This pattern is generalized for any network
as many incoming ports sending traffic to one or few uplinks.
Synchronous arrival time: When two, or more, frames of respective
sizes L1 and L2 arrive at their respective one or multiple ingress
ports, and there is an overlap of the arrival time for any of the
bits on the Device Under Test (DUT), then the frames L1 and L2 have a
synchronous arrival times. This is called Incast regardless of in
many-to-one (simpler form) or, many-to-many.
Asynchronous arrival time: Any condition not defined by synchronous
arrival time.
Percentage of synchronization: This defines the level of overlap
[amount of bits] between the frames L1,L2..Ln.
Example: Two 64 bytes frames, of length L1 and L2, arrive to ingress
port 1 and port 2 of the DUT. There is an overlap of 6.4 bytes
between the two where L1 and L2 were at the same time on the
respective ingress ports. Therefore the percentage of synchronization
is 10%.
Stateful type traffic defines packets exchanged with a stateful
protocol such as TCP.
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Stateless type traffic defines packets exchanged with a stateless
protocol such as UDP.
6.2.2 Discussion
In this scenario, buffers are solicited on the DUT. In an ingress
buffering mechanism, the ingress port buffers would be solicited
along with Virtual Output Queues, when available; whereas in an
egress buffer mechanism, the egress buffer of the one outgoing port
would be used.
In either case, regardless of where the buffer memory is located on
the switch architecture, the Incast creates buffer utilization.
When one or more frames having synchronous arrival times at the DUT
they are considered forming an Incast.
6.2.3 Measurement Units
It is a MUST to measure the number of ingress and egress ports. It is
a MUST to have a non-null percentage of synchronization, which MUST
be specified.
7 Application Throughput: Data Center Goodput
7.1. Definition
In Data Center Networking, a balanced network is a function of
maximal throughput and minimal loss at any given time. This is
captured by the Goodput [4]. Goodput is the application-level
throughput. For standard TCP applications, a very small loss can have
a dramatic effect on application throughput. [RFC2647] has a
definition of Goodput; the definition in this publication is a
variance.
Goodput is the number of bits per unit of time forwarded to the
correct destination interface of the DUT, minus any bits
retransmitted.
7.2. Discussion
In data center benchmarking, the goodput is a value that SHOULD be
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measured. It provides a realistic idea of the usage of the available
bandwidth. A goal in data center environments is to maximize the
goodput while minimizing the loss.
7.3. Measurement Units
The Goodput, G, is then measured by the following formula:
G=(S/F) x V bytes per second
-S represents the payload bytes, which does not include packet or TCP
headers
-F is the frame size
-V is the speed of the media in bytes per second
Example: A TCP file transfer over HTTP protocol on a 10GB/s media.
The file cannot be transferred over Ethernet as a single continuous
stream. It must be broken down into individual frames of 1500B when
the standard MTU (Maximum Transmission Unit) is used. Each packet
requires 20B of IP header information and 20B of TCP header
information; therefore 1460B are available per packet for the file
transfer. Linux based systems are further limited to 1448B as they
also carry a 12B timestamp. Finally, the date is transmitted in this
example over Ethernet which adds a 26B overhead per packet.
G= 1460/1526 x 10 Gbit/s which is 9.567 Gbit per second or 1.196 GB
per second.
Please note: This example does not take into consideration the
additional Ethernet overhead, such as the interframe gap (a minimum
of 96 bit times), nor collisions (which have a variable impact,
depending on the network load).
When conducting Goodput measurements please document in addition to
the 4.1 section the following information:
-The TCP Stack used
-OS Versions
-NIC firmware version and model
For example, Windows TCP stacks and different Linux versions can
influence TCP based tests results.
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8. Security Considerations
Benchmarking activities as described in this memo are limited to
technology characterization using controlled stimuli in a laboratory
environment, with dedicated address space and the constraints
specified in the sections above.
The benchmarking network topology will be an independent test setup
and MUST NOT be connected to devices that may forward the test
traffic into a production network, or misroute traffic to the test
management network.
Further, benchmarking is performed on a "black-box" basis, relying
solely on measurements observable external to the DUT.
Special capabilities SHOULD NOT exist in the DUT specifically for
benchmarking purposes. Any implications for network security arising
from the DUT SHOULD be identical in the lab and in production
networks.
9. IANA Considerations
NO IANA Action is requested at this time.
10. References
10.1. Normative References
[draft-ietf-bmwg-dcbench-methodology] Avramov L. and Rapp J., "Data
Center Benchmarking Methodology", RFC "draft-ietf-bmwg-dcbench-
methodology", DATE (to be updated once published)
[RFC1242] Bradner, S. "Benchmarking Terminology for Network
Interconnection Devices", RFC 1242, July 1991, <http://www.rfc-
editor.org/info/rfc1242>
[RFC2544] Bradner, S. and J. McQuaid, "Benchmarking Methodology for
Network Interconnect Devices", RFC 2544, March 1999,
<http://www.rfc-editor.org/info/rfc2544>
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119,
March 1997, <http://www.rfc-editor.org/info/rfc2119>
[RFC5481] , Morton, A., "Packet Delay Variation Applicability
Statement", BCP 14, RFC 5481, March 2009, <http://www.rfc-
editor.org/info/rfc5481>
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10.2. Informative References
[RFC2889] Mandeville R. and Perser J., "Benchmarking
Methodology for LAN Switching Devices", RFC 2889, August 2000,
<http://www.rfc-editor.org/info/rfc2889>
[RFC3918] Stopp D. and Hickman B., "Methodology for IP Multicast
Benchmarking", RFC 3918, October 2004, <http://www.rfc-
editor.org/info/rfc3918>
[4] Yanpei Chen, Rean Griffith, Junda Liu, Randy H. Katz, Anthony D.
Joseph, "Understanding TCP Incast Throughput Collapse in
Datacenter Networks,
"http://yanpeichen.com/professional/usenixLoginIncastReady.pdf"
[RFC2432] Dubray, K., "Terminology for IP Multicast
Benchmarking", BCP 14, RFC 2432, DOI 10.17487/RFC2432, October
1998, <http://www.rfc-editor.org/info/rfc2432>
[RFC2647] Newman D. ,"Benchmarking Terminology for Firewall
Performance" BCP 14, RFC 2647, August 1999, <http://www.rfc-
editor.org/info/rfc2647>
10.3. Acknowledgments
The authors would like to thank Alfred Morton, Scott Bradner,
Ian Cox, Tim Stevenson for their reviews and feedback.
Authors' Addresses
Lucien Avramov
Google
1600 Amphitheatre Parkway
Mountain View, CA 94043
United States
Phone: +1 408 774 9077
Email: lucien.avramov@gmail.com
Jacob Rapp
VMware
3401 Hillview Ave
Palo Alto, CA 94304
United States
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Phone: +1 650 857 3367
Email: jrapp@vmware.com
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