draft-ietf-ippm-tcp-throughput-tm-05.txt		draft-ietf-ippm-tcp-throughput-tm-06.txt
	Network Working Group B. Constantine		Network Working Group B. Constantine
	Internet-Draft JDSU		Internet-Draft JDSU
	Intended status: Informational G. Forget		Intended status: Informational G. Forget
	Expires: February 12, 2011 Bell Canada (Ext. Consultant)		Expires: February 27, 2011 Bell Canada (Ext. Consultant)
	L. Jorgenson		L. Jorgenson
	nooCore		nooCore
	Reinhard Schrage		Reinhard Schrage
	Schrage Consulting		Schrage Consulting
	August 12, 2010		August 27, 2010
	TCP Throughput Testing Methodology		TCP Throughput Testing Methodology
	draft-ietf-ippm-tcp-throughput-tm-05.txt		draft-ietf-ippm-tcp-throughput-tm-06.txt
	Abstract		Abstract
	This memo describes a methodology for measuring sustained TCP		This memo describes a methodology for measuring sustained TCP
	throughput performance in an end-to-end managed network environment.		throughput performance in an end-to-end managed network environment.
	This memo is intended to provide a practical approach to help users		This memo is intended to provide a practical approach to help users
	validate the TCP layer performance of a managed network, which should		validate the TCP layer performance of a managed network, which should
	provide a better indication of end-user application level experience.		provide a better indication of end-user application level experience.
	In the methodology, various TCP and network parameters are identified		In the methodology, various TCP and network parameters are identified
	that should be tested as part of the network verification at the TCP		that should be tested as part of the network verification at the TCP
	layer.		layer.
			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].
	Status of this Memo		Status of this Memo
	This Internet-Draft is submitted to IETF in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF), its areas, and its working groups. Note that		Task Force (IETF). Note that other groups may also distribute
	other groups may also distribute working documents as Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts. Creation date August 12, 2010.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	The list of current Internet-Drafts can be accessed at		This Internet-Draft will expire on February 27, 2011.
	http://www.ietf.org/ietf/1id-abstracts.txt.
	The list of Internet-Draft Shadow Directories can be accessed at
	http://www.ietf.org/shadow.html.
	This Internet-Draft will expire on February 12, 2011.
	Copyright Notice		Copyright Notice
	Copyright (c) 2010 IETF Trust and the persons identified as the		Copyright (c) 2010 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
	2. Goals of this Methodology. . . . . . . . . . . . . . . . . . . 4		2. Goals of this Methodology. . . . . . . . . . . . . . . . . . . 4
	2.1 TCP Equilibrium State Throughput . . . . . . . . . . . . . 5		2.1 TCP Equilibrium State Throughput . . . . . . . . . . . . . 5
	2.2 Metrics for TCP Throughput Tests . . . . . . . . . . . . . 6		2.2 Metrics for TCP Throughput Tests . . . . . . . . . . . . . 6
	3. TCP Throughput Testing Methodology . . . . . . . . . . . . . . 7		3. TCP Throughput Testing Methodology . . . . . . . . . . . . . . 7
	3.1 Determine Network Path MTU . . . . . . . . . . . . . . . . 8		3.1 Determine Network Path MTU . . . . . . . . . . . . . . . . 8
	3.2. Baseline Round-trip Delay and Bandwidth. . . . . . . . . . 10		3.2. Baseline Round-trip Delay and Bandwidth. . . . . . . . . . 10
	skipping to change at page 2, line 41		skipping to change at page 2, line 41
	3.3. TCP Throughput Tests . . . . . . . . . . . . . . . . . . . 11		3.3. TCP Throughput Tests . . . . . . . . . . . . . . . . . . . 11
	3.3.1 Calculate Optimum TCP Window Size. . . . . . . . . . . 12		3.3.1 Calculate Optimum TCP Window Size. . . . . . . . . . . 12
	3.3.2 Conducting the TCP Throughput Tests. . . . . . . . . . 14		3.3.2 Conducting the TCP Throughput Tests. . . . . . . . . . 14
	3.3.3 Single vs. Multiple TCP Connection Testing . . . . . . 15		3.3.3 Single vs. Multiple TCP Connection Testing . . . . . . 15
	3.3.4 Interpretation of the TCP Throughput Results . . . . . 16		3.3.4 Interpretation of the TCP Throughput Results . . . . . 16
	3.4. Traffic Management Tests . . . . . . . . . . . . . . . . . 16		3.4. Traffic Management Tests . . . . . . . . . . . . . . . . . 16
	3.4.1 Traffic Shaping Tests. . . . . . . . . . . . . . . . . 16		3.4.1 Traffic Shaping Tests. . . . . . . . . . . . . . . . . 16
	3.4.1.1 Interpretation of Traffic Shaping Test Results. . . 17		3.4.1.1 Interpretation of Traffic Shaping Test Results. . . 17
	3.4.2 RED Tests. . . . . . . . . . . . . . . . . . . . . . . 18		3.4.2 RED Tests. . . . . . . . . . . . . . . . . . . . . . . 18
	3.4.2.1 Interpretation of RED Results . . . . . . . . . . . 18		3.4.2.1 Interpretation of RED Results . . . . . . . . . . . 18
	4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19		4. Security Considerations . . . . . . . . . . . . . . . . . . . 18
	5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19		5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
			5.1. Registry Specification . . . . . . . . . . . . . . . . . . 19
			5.2. Registry Contents . . . . . . . . . . . . . . . . . . . . 19
			6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19
			7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
			7.1 Normative References . . . . . . . . . . . . . . . . . . . 19
			7.2 Informative References . . . . . . . . . . . . . . . . . . 20
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20
	1. Introduction		1. Introduction
	Testing an operational network prior to customer activation is referred		Testing an operational network prior to customer activation is
	to as "turn-up" testing and the SLA is generally Layer 2/3 packet		referred to as "turn-up" testing and the SLA (Service Level
	throughput, delay, loss and jitter.		Agreement) is generally based upon Layer 2/3 packet throughput,
			delay, loss and jitter.
	Network providers are coming to the realization that Layer 2/3 testing		Network providers are coming to the realization that Layer 2/3
	and TCP layer testing are required to more adequately ensure end-user		testing and TCP layer testing are required to more adequately ensure
	satisfaction. Therefore, the network provider community desires to		end-user satisfaction. Therefore, the network provider community
	measure network throughput performance at the TCP layer. Measuring		desires to measure network throughput performance at the TCP layer.
	TCP throughput provides a meaningful measure with respect to the end		Measuring TCP throughput provides a meaningful measure with respect
	user's application SLA (and ultimately reach some level of TCP		to the end user experience (and ultimately reach some level of
	testing interoperability which does not exist today).		TCP testing interoperability which does not exist today).
	Additionally, end-users (business enterprises) seek to conduct		Additionally, end-users (business enterprises) seek to conduct
	repeatable TCP throughput tests between enterprise locations. Since		repeatable TCP throughput tests between enterprise locations. Since
	these enterprises rely on the networks of the providers, a common test		these enterprises rely on the networks of the providers, a common
	methodology (and metrics) would be equally beneficial to both parties.		test methodology (and metrics) would be equally beneficial to both
			parties.
	So the intent behind this TCP throughput draft is to define		So the intent behind this TCP throughput draft is to define
	a methodology for testing sustained TCP layer performance. In this		a methodology for testing sustained TCP layer performance. In this
	document, sustained TCP throughput is that amount of data per unit		document, sustained TCP throughput is that amount of data per unit
	time that TCP transports during equilibrium (steady state), i.e.		time that TCP transports during equilibrium (steady state), i.e.
	after the initial slow start phase. We refer to this state as TCP		after the initial slow start phase. We refer to this state as TCP
	Equilibrium, and that the equalibrium throughput is the maximum		Equilibrium, and that the equilibrium throughput is the maximum
	achievable for the TCP connection(s).		achievable for the TCP connection(s).
	There are many variables to consider when conducting a TCP throughput		There are many variables to consider when conducting a TCP throughput
	test and this methodology focuses on some of the most common		test and this methodology focuses on some of the most common
	parameters that should be considered such as:		parameters that should be considered such as:
	- Path MTU and Maximum Segment Size (MSS)		- Path MTU and Maximum Segment Size (MSS)
	- RTT and Bottleneck BW		- RTT and Bottleneck BW
	- Ideal TCP Window (Bandwidth Delay Product)		- Ideal TCP Window (Bandwidth Delay Product)
	- Single Connection and Multiple Connection testing		- Single Connection and Multiple Connection testing
	One other important note, it is highly recommended that traditional		One other important note, it is highly recommended that traditional
	Layer 2/3 type tests are conducted to verify the integrity of the		Layer 2/3 type tests are conducted to verify the integrity of the
	network before conducting TCP tests. Examples include RFC2544, iperf		network before conducting TCP tests. Examples include RFC 2544
	(UDP mode), or manual packet layer test techniques where packet		[RFC2544], iperf (UDP mode), or manual packet layer test techniques
	throughput, loss, and delay measurements are conducted.		where packet throughput, loss, and delay measurements are conducted.
	2. Goals of this Methodology		2. Goals of this Methodology
	Before defining the goals of this methodology, it is important to		Before defining the goals of this methodology, it is important to
	clearly define the areas that are not intended to be measured or		clearly define the areas that are not intended to be measured or
	analyzed by such a methodology.		analyzed by such a methodology.
	- The methodology is not intended to predict TCP throughput		- The methodology is not intended to predict TCP throughput
	behavior during the transient stages of a TCP connection, such		behavior during the transient stages of a TCP connection, such
	as initial slow start.		as initial slow start.
	skipping to change at page 4, line 43		skipping to change at page 4, line 43
	- Provide a practical test approach that specifies the more well		- Provide a practical test approach that specifies the more well
	understood (and end-user configurable) TCP parameters such as Window		understood (and end-user configurable) TCP parameters such as Window
	size, MSS (Maximum Segment Size), # connections, and how these affect		size, MSS (Maximum Segment Size), # connections, and how these affect
	the outcome of TCP performance over a network.		the outcome of TCP performance over a network.
	- Provide specific test conditions (link speed, RTT, window size,		- Provide specific test conditions (link speed, RTT, window size,
	etc.) and maximum achievable TCP throughput under TCP Equilbrium		etc.) and maximum achievable TCP throughput under TCP Equilbrium
	conditions. For guideline purposes, provide examples of these test		conditions. For guideline purposes, provide examples of these test
	conditions and the maximum achievable TCP throughput during the		conditions and the maximum achievable TCP throughput during the
	equilbrium state. Section 2.1 provides specific details concerning		equilibrium state. Section 2.1 provides specific details concerning
	the definition of TCP Equilibrium within the context of this draft.		the definition of TCP Equilibrium within the context of this draft.
	- Define two (2) basic metrics that can be used to compare the		- Define two (2) basic metrics that can be used to compare the
	performance of TCP connections under various network conditions		performance of TCP connections under various network conditions
	- In test situations where the recommended procedure does not yield		- In test situations where the recommended procedure does not yield
	the maximum achievable TCP throughput result, this draft provides some		the maximum achievable TCP throughput result, this draft provides
	possible areas within the end host or network that should be		some possible areas within the end host or network that should be
	considered for investigation (although again, this draft is not		considered for investigation (although again, this draft is not
	intended to provide a detailed diagnosis of these issues)		intended to provide a detailed diagnosis of these issues)
	2.1 TCP Equilibrium State Throughput		2.1 TCP Equilibrium State Throughput
	TCP connections have three (3) fundamental congestion window phases		TCP connections have three (3) fundamental congestion window phases
	as documented in RFC2581. These states are:		as documented in RFC 5681 [RFC5681]. These states are:
	- Slow Start, which occurs during the beginning of a TCP transmission		- Slow Start, which occurs during the beginning of a TCP transmission
	or after a retransmission time out event		or after a retransmission time out event
	- Congestion avoidance, which is the phase during which TCP ramps up		- Congestion avoidance, which is the phase during which TCP ramps up
	to establish the maximum attainable throughput on an end-end network		to establish the maximum attainable throughput on an end-end network
	path. Retransmissions are a natural by-product of the TCP congestion		path. Retransmissions are a natural by-product of the TCP congestion
	avoidance algorithm as it seeks to achieve maximum throughput on		avoidance algorithm as it seeks to achieve maximum throughput on
	the network path.		the network path.
	- Retransmission phase, which include Fast Retransmit (Tahoe) and Fast		- Retransmission phase, which include Fast Retransmit (Tahoe) and
	Recovery (Reno and New Reno). When a packet is lost, the Congestion		Fast Recovery (Reno and New Reno). When a packet is lost, the
	avoidance phase transitions to a Fast Retransmission or Recovery		Congestion avoidance phase transitions to a Fast Retransmission or
	Phase dependent upon the TCP implementation.		Recovery Phase dependent upon the TCP implementation.
	The following diagram depicts these states.		The following diagram depicts these states.
	| ssthresh		| ssthresh
	TCP | |		TCP | |
	Through- | | Equilibrium		Through- | | Equilibrium
	put | |\ /\/\/\/\/\ Retransmit /\/\ ...		put | |\ /\/\/\/\/\ Retransmit /\/\ ...
	| | \ / | Time-out /		| | \ / | Time-out /
	| | \ / | _______ _/		| | \ / | _______ _/
	| Slow _/ |/ | / | Slow _/		| Slow _/ |/ | / | Slow _/
	| Start _/ Congestion |/ |Start_/ Congestion		| Start _/ Congestion |/ |Start_/ Congestion
	| _/ Avoidance Loss | _/ Avoidance		| _/ Avoidance Loss | _/ Avoidance
	| _/ Event | _/		| _/ Event | _/
	| _/ |/		| _/ |/
	|/___________________________________________________________		|/__________________________________________________________
	Time		Time
	This TCP methodology provides guidelines to measure the equilibrium		This TCP methodology provides guidelines to measure the equilibrium
	throughput which refers to the maximum sustained rate obtained by		throughput which refers to the maximum sustained rate obtained by
	congestion avoidance before packet loss conditions occur (which would		congestion avoidance before packet loss conditions occur (which would
	cause the state change from congestion avoidance to a retransmission		cause the state change from congestion avoidance to a retransmission
	phase). All maximum achievable throughputs specified in Section 3 are		phase). All maximum achievable throughputs specified in Section 3 are
	with respect to this Equilibrium state.		with respect to this equilibrium state.
	2.2 Metrics for TCP Throughput Tests		2.2 Metrics for TCP Throughput Tests
	This draft focuses on a TCP throughtput methodology and also		This draft focuses on a TCP throughput methodology and also
	provides two basic metrics to compare results of various throughput		provides two basic metrics to compare results of various throughput
	tests. It is recognized that the complexity and unpredictability of		tests. It is recognized that the complexity and unpredictability of
	TCP makes it impossible to develop a complete set of metrics that		TCP makes it impossible to develop a complete set of metrics that
	account for the myriad of variables (i.e. RTT variation, loss		account for the myriad of variables (i.e. RTT variation, loss
	conditions, TCP implementation, etc.). However, these two basic		conditions, TCP implementation, etc.). However, these two basic
	metrics faciliate TCP throughput comparisons under varying network		metrics will faciliate TCP throughput comparisons under varying
	conditions and between network traffic management techniques.		network conditions and between network traffic management techniques.
	The TCP Efficiency metric is the percentage of bytes that were not		The TCP Efficiency metric is the percentage of bytes that were not
	retransmitted and is defined as:		retransmitted and is defined as:
	Transmitted Bytes - Retransmitted Bytes		Transmitted Bytes - Retransmitted Bytes
	--------------------------------------- x 100		--------------------------------------- x 100
	Transmitted Bytes		Transmitted Bytes
	This metric provides a comparative measure between various QoS		This metric provides a comparative measure between various QoS
	mechanisms such as traffic management, congestion avoidance, and also		mechanisms such as traffic management, congestion avoidance, and also
	various TCP implementations (i.e. Reno, Vegas, etc.).		various TCP implementations (i.e. Reno, Vegas, etc.).
	As an example, if 100,000 bytes were sent and 2,000 had to be		As an example, if 100,000 bytes were sent and 2,000 had to be
	retransmitted, the TCP Efficiency would be calculated as:		retransmitted, the TCP Efficiency would be calculated as:
	100,000 - 2,000		100,000 - 2,000
	---------------- x 100 = 98%		---------------- x 100 = 98%
	100,000		100,000
	Note that the retranmitted bytes may have occurred more than once,		Note that the retransmitted bytes may have occurred more than once,
	and these multiple retransmissions are added to the bytes retransmitted		and these multiple retransmissions are added to the bytes
	count.		retransmitted count.
	The second metric is the TCP Transfer Time, which is simply the time		The second metric is the TCP Transfer Time, which is simply the time
	it takes to transfer a block of data across simultaneous TCP		it takes to transfer a block of data across simultaneous TCP
	connections. The concept is useful when benchmarking traffic		connections. The concept is useful when benchmarking traffic
	management techniques, where multiple connections are generally		management techniques, where multiple connections are generally
	required.		required.
	The TCP Transfer time can also be used to provide a normalized ratio of		The TCP Transfer time can also be used to provide a normalized ratio
	the actual TCP Transfer Time versus ideal Transfer Time. This ratio		of the actual TCP Transfer Time versus ideal Transfer Time. This
	is called the TCP Transfer Index and is defined as:		ratio is called the TCP Transfer Index and is defined as:
	Actual TCP Transfer Time		Actual TCP Transfer Time
	-------------------------		-------------------------
	Ideal TCP Transfer Time		Ideal TCP Transfer Time
	An example would be the bulk transfer of 100 MB upon 5 simultaneous TCP		An example would be the bulk transfer of 100 MB upon 5 simultaneous
	connections over a 500 Mbit/s Ethernet service (each connection		TCP connections over a 500 Mbit/s Ethernet service (each connection
	uploading 100 MB). Each connection may achieve different throughputs		uploading 100 MB). Each connection may achieve different throughputs
	during a test and the overall throughput rate is not always easy to		during a test and the overall throughput rate is not always easy to
	determine (especially as the number of connections increases).		determine (especially as the number of connections increases).
	The ideal TCP Transfer Time would be ~8 seconds, but in this example,		The ideal TCP Transfer Time would be ~8 seconds, but in this example,
	the actual TCP Transfer Time was 12 seconds. The TCP Transfer Index		the actual TCP Transfer Time was 12 seconds. The TCP Transfer Index
	would be 12/8 = 1.5, which indicates that the transfer across all		would be 12/8 = 1.5, which indicates that the transfer across all
	connections took 1.5 times longer than the ideal.		connections took 1.5 times longer than the ideal.
	Note that both the TCP Efficiency and TCP Transfer Time metrics must be		Note that both the TCP Efficiency and TCP Transfer Time metrics must
	measured during each throughput test. The correlation of TCP Transfer		be measured during each throughput test. The correlation of TCP
	Time with TCP Efficiency can help to diagnose whether the TCP Transfer		Transfer Time with TCP Efficiency can help to diagnose whether the
	Time was negatively impacted by retransmissions (poor TCP Efficiency).		TCP Transfer Time was negatively impacted by retransmissions (poor
			TCP Efficiency).
	3. TCP Throughput Testing Methodology		3. TCP Throughput Testing Methodology
	As stated in Section 1, it is considered best practice to verify		As stated in Section 1, it is considered best practice to verify
	the integrity of the network by conducting Layer2/3 stress tests		the integrity of the network by conducting Layer2/3 stress tests
	such as RFC2544 (or other methods of network stress tests). If the		such as RFC2544 (or other methods of network stress tests). If the
	network is not performing properly in terms of packet loss, jitter,		network is not performing properly in terms of packet loss, jitter,
	etc. then the TCP layer testing will not be meaningful since the		etc. then the TCP layer testing will not be meaningful since the
	equalibrium throughput would be very difficult to achieve (in a		equilibrium throughput would be very difficult to achieve (in a
	"dysfunctional" network).		"dysfunctional" network).
	The following represents the sequential order of steps to conduct the		The following represents the sequential order of steps to conduct the
	TCP throughput testing methodology:		TCP throughput testing methodology:
	1. Identify the Path MTU. Packetization Layer Path MTU Discovery		1. Identify the Path MTU. Packetization Layer Path MTU Discovery
	or PLPMTUD (RFC4821) should be conducted to verify the minimum network		or PLPMTUD, [RFC4821], should be conducted to verify the maximum
	path MTU. Conducting PLPMTUD establishes the upper limit for the MSS		network path MTU. Conducting PLPMTUD establishes the upper limit for
	to be used in subsequent steps.		the MSS to be used in subsequent steps.
	2. Baseline Round-trip Delay and Bandwidth. These measurements provide		2. Baseline Round-trip Delay and Bandwidth. These measurements
	estimates of the ideal TCP window size, which will be used in		provide estimates of the ideal TCP window size, which will be used in
	subsequent test steps.		subsequent test steps.
	3. TCP Connection Throughput Tests. With baseline measurements		3. TCP Connection Throughput Tests. With baseline measurements
	of round trip delay and bandwidth, a series of single and multiple TCP		of round trip delay and bandwidth, a series of single and multiple
	connection throughput tests can be conducted to baseline the network		TCP connection throughput tests can be conducted to baseline the
	performance expectations.		network performance expectations.
	4. Traffic Management Tests. Various traffic management and queuing		4. Traffic Management Tests. Various traffic management and queueing
	techniques are tested in this step, using multiple TCP connections.		techniques are tested in this step, using multiple TCP connections.
	Multiple connection testing can verify that the network is configured		Multiple connection testing can verify that the network is configured
	properly for traffic shaping versus policing, various queuing		properly for traffic shaping versus policing, various queueing
	implementations, and RED.		implementations, and RED.
	Important to note are some of the key characteristics and		Important to note are some of the key characteristics and
	considerations for the TCP test instrument. The test host may be a		considerations for the TCP test instrument. The test host may be a
	standard computer or dedicated communications test instrument		standard computer or dedicated communications test instrument
	and these TCP test hosts be capable of emulating both a client and a		and these TCP test hosts be capable of emulating both a client and a
	server.		server.
	Whether the TCP test host is a standard computer or dedicated test		Whether the TCP test host is a standard computer or dedicated test
	instrument, the following areas should be considered when selecting		instrument, the following areas should be considered when selecting
	a test host:		a test host:
	- TCP implementation used by the test host OS, i.e. Linux OS kernel		- TCP implementation used by the test host OS, i.e. Linux OS kernel
	using TCP Reno, TCP options supported, etc. This will obviously be		using TCP Reno, TCP options supported, etc. This will obviously be
	more important when using custom test equipment where the TCP		more important when using custom test equipment where the TCP
	implementation may be customized or tuned to run in higher		implementation may be customized or tuned to run in higher
	performance hardware		performance hardware
	- Most importantly, the TCP test host must be capable of generating		- Most importantly, the TCP test host must be capable of generating
	and receiving stateful TCP test traffic at the full link speed of the		and receiving stateful TCP test traffic at the full link speed of the
	network under test. As a general rule of thumb, testing TCP throughput		network under test. As a general rule of thumb, testing TCP
	at rates greater than 100 Mbit/sec generally requires high		throughput at rates greater than 100 Mbit/sec generally requires high
	performance server hardware or dedicated hardware based test tools.		performance server hardware or dedicated hardware based test tools.
	- To measure RTT and TCP Efficiency per connection, this will generally		- To measure RTT and TCP Efficiency per connection, this will
	require dedicated hardware based test tools. In the absence of		generally require dedicated hardware based test tools. In the absence
	dedciated hardware based test tools, these measurements may need to be		of dedicated hardware based test tools, these measurements may need
	conducted with packet capture tools (conduct TCP throughput tests and		to be conducted with packet capture tools (conduct TCP throughput
	analyze RTT and retransmission results with packet captures).		tests and analyze RTT and retransmission results with packet
			captures).
	3.1. Determine Network Path MTU		3.1. Determine Network Path MTU
	TCP implementations should use Path MTU Discovery techniques (PMTUD).		TCP implementations should use Path MTU Discovery techniques (PMTUD).
	PMTUD relies on ICMP 'need to frag' messages to learn the path MTU.		PMTUD relies on ICMP 'need to frag' messages to learn the path MTU.
	When a device has a packet to send which has the Don't Fragment (DF)		When a device has a packet to send which has the Don't Fragment (DF)
	bit in the IP header set and the packet is larger than the Maximum		bit in the IP header set and the packet is larger than the Maximum
	Transmission Unit (MTU) of the next hop link, the packet is dropped		Transmission Unit (MTU) of the next hop link, the packet is dropped
	and the device sends an ICMP 'need to frag' message back to the host		and the device sends an ICMP 'need to frag' message back to the host
	that originated the packet. The ICMP 'need to frag' message includes		that originated the packet. The ICMP 'need to frag' message includes
	skipping to change at page 10, line 16		skipping to change at page 10, line 16
	Before stateful TCP testing can begin, it is important to baseline		Before stateful TCP testing can begin, it is important to baseline
	the round trip delay and bandwidth of the network to be tested.		the round trip delay and bandwidth of the network to be tested.
	These measurements provide estimates of the ideal TCP window size,		These measurements provide estimates of the ideal TCP window size,
	which will be used in subsequent test steps. These latency and		which will be used in subsequent test steps. These latency and
	bandwidth tests should be run during the time of day for which		bandwidth tests should be run during the time of day for which
	the TCP throughput tests will occur.		the TCP throughput tests will occur.
	The baseline RTT is used to predict the bandwidth delay product and		The baseline RTT is used to predict the bandwidth delay product and
	the TCP Transfer Time for the subsequent throughput tests. Since this		the TCP Transfer Time for the subsequent throughput tests. Since this
	methodology requires that RTT be measured during the entire throughput		methodology requires that RTT be measured during the entire
	test, the extent by which the RTT varied during the throughput test can		throughput test, the extent by which the RTT varied during the
	be quantified.		throughput test can be quantified.
	3.2.1 Techniques to Measure Round Trip Time		3.2.1 Techniques to Measure Round Trip Time
	Following the definitions used in the references of the appendix;		Following the definitions used in the references of the appendix;
	Round Trip Time (RTT) is the time elapsed between the clocking in of		Round Trip Time (RTT) is the time elapsed between the clocking in of
	the first bit of a payload packet to the receipt of the last bit of the		the first bit of a payload packet to the receipt of the last bit of
	corresponding acknowledgement. Round Trip Delay (RTD) is used		the corresponding acknowledgement. Round Trip Delay (RTD) is used
	synonymously to twice the Link Latency.		synonymously to twice the Link Latency.
	In any method used to baseline round trip delay between network		In any method used to baseline round trip delay between network
	end-points, it is important to realize that network latency is the		end-points, it is important to realize that network latency is the
	sum of inherent network delay and congestion. The RTT should be		sum of inherent network delay and congestion. The RTT should be
	baselined during "off-peak" hours to obtain a reliable figure for		baselined during "off-peak" hours to obtain a reliable figure for
	network latency (versus additional delay caused by congestion).		network latency (versus additional delay caused by congestion).
	During the actual sustained TCP throughput tests, it is critical		During the actual sustained TCP throughput tests, it is critical
	to measure RTT along with measured TCP throughput. Congestive		to measure RTT along with measured TCP throughput. Congestive
	skipping to change at page 10, line 48		skipping to change at page 10, line 48
	This is not meant to provide an exhaustive list, but summarizes some		This is not meant to provide an exhaustive list, but summarizes some
	of the more common ways to determine round trip time (RTT) through		of the more common ways to determine round trip time (RTT) through
	the network. The desired resolution of the measurement (i.e. msec		the network. The desired resolution of the measurement (i.e. msec
	versus usec) may dictate whether the RTT measurement can be achieved		versus usec) may dictate whether the RTT measurement can be achieved
	with standard tools such as ICMP ping techniques or whether		with standard tools such as ICMP ping techniques or whether
	specialized test equipment would be required with high precision		specialized test equipment would be required with high precision
	timers. The objective in this section is to list several techniques		timers. The objective in this section is to list several techniques
	in order of decreasing accuracy.		in order of decreasing accuracy.
	- Use test equipment on each end of the network, "looping" the		- Use test equipment on each end of the network, "looping" the
	far-end tester so that a packet stream can be measured end-end. This		far-end tester so that a packet stream can be measured end-end. This
	test equipment RTT measurement may be compatible with delay		test equipment RTT measurement may be compatible with delay
	measurement protocols specified in RFC5357.		measurement protocols specified in RFC5357.
	- Conduct packet captures of TCP test applications using for example		- Conduct packet captures of TCP test applications using for example
	"iperf" or FTP, etc. By running multiple experiments, the packet		"iperf" or FTP, etc. By running multiple experiments, the packet
	captures can be studied to estimate RTT based upon the SYN -> SYN-ACK		captures can be studied to estimate RTT based upon the SYN -> SYN-ACK
	handshakes within the TCP connection set-up.		handshakes within the TCP connection set-up.
	- ICMP Pings may also be adequate to provide round trip time		- ICMP Pings may also be adequate to provide round trip time
	estimations. Some limitations of ICMP Ping are the msec resolution		estimations. Some limitations of ICMP Ping are the msec resolution
	and whether the network elements respond to pings (or block them).		and whether the network elements respond to pings (or block them).
	3.2.2 Techniques to Measure End-end Bandwidth		3.2.2 Techniques to Measure End-end Bandwidth
	There are many well established techniques available to provide		There are many well established techniques available to provide
	estimated measures of bandwidth over a network. This measurement		estimated measures of bandwidth over a network. This measurement
	should be conducted in both directions of the network, especially for		should be conducted in both directions of the network, especially for
	access networks which are inherently asymmetrical. Some of the		access networks which are inherently asymmetrical. Some of the
	asymmetric implications to TCP performance are documented in RFC-3449		asymmetric implications to TCP performance are documented in RFC 3449
	and the results of this work will be further studied to determine		[RFC3449].
	relevance to this draft.
	The bandwidth measurement test must be run with stateless IP streams		The bandwidth measurement test must be run with stateless IP streams
	(not stateful TCP) in order to determine the available bandwidth in		(not stateful TCP) in order to determine the available bandwidth in
	each direction. And this test should obviously be performed at		each direction. And this test should obviously be performed at
	various intervals throughout a business day (or even across a week).		various intervals throughout a business day (or even across a week).
	Ideally, the bandwidth test should produce a log output of the		Ideally, the bandwidth test should produce a log output of the
	bandwidth achieved across the test interval AND the round trip delay.		bandwidth achieved across the test interval AND the round trip delay.
	And during the actual TCP level performance measurements (Sections		And during the actual TCP level performance measurements (Sections
	3.3 - 3.5), the test tool must be able to track round trip time		3.3 - 3.5), the test tool must be able to track round trip time
	of the TCP connection(s) during the test. Measuring round trip time		of the TCP connection(s) during the test. Measuring round trip time
	variation (aka "jitter") provides insight into effects of congestive		variation (aka "jitter") provides insight into effects of congestive
	delay on the sustained throughput achieved for the TCP layer test.		delay on the sustained throughput achieved for the TCP layer test.
	3.3. TCP Throughput Tests		3.3. TCP Throughput Tests
	This draft specifically defines TCP throughput techniques to verify		This draft specifically defines TCP throughput techniques to verify
	sustained TCP performance in a managed business network. Defined		sustained TCP performance in a managed business network. Defined
	in section 2.1, the equalibrium throughput reflects the maximum		in section 2.1, the equilibrium throughput reflects the maximum
	rate achieved by a TCP connection within the congestion avoidance		rate achieved by a TCP connection within the congestion avoidance
	phase on a end-end network path. This section and others will define		phase on a end-end network path. This section and others will define
	the method to conduct these sustained throughput tests and guidelines		the method to conduct these sustained throughput tests and guidelines
	of the predicted results.		of the predicted results.
	With baseline measurements of round trip time and bandwidth		With baseline measurements of round trip time and bandwidth
	from section 3.2, a series of single and multiple TCP connection		from section 3.2, a series of single and multiple TCP connection
	throughput tests can be conducted to baseline network performance		throughput tests can be conducted to baseline network performance
	against expectations.		against expectations.
	It is recommended to run the tests in each direction independently		It is recommended to run the tests in each direction independently
	first, then run both directions simultaneously. In each case, the TCP		first, then run both directions simultaneously. In each case, the
	Efficiency and TCP Transfer Time metrics must be measured in each		TCP Efficiency and TCP Transfer Time metrics must be measured in each
	direction.		direction.
	3.3.1 Calculate Optimum TCP Window Size		3.3.1 Calculate Optimum TCP Window Size
	The optimum TCP window size can be calculated from the bandwidth delay		The optimum TCP window size can be calculated from the bandwidth
	product (BDP), which is:		delay product (BDP), which is:
	BDP (bits) = RTT (sec) x Bandwidth (bps)		BDP (bits) = RTT (sec) x Bandwidth (bps)
	By dividing the BDP by 8, the "ideal" TCP window size is calculated.		By dividing the BDP by 8, the "ideal" TCP window size is calculated.
	An example would be a T3 link with 25 msec RTT. The BDP would equal		An example would be a T3 link with 25 msec RTT. The BDP would equal
	~1,105,000 bits and the ideal TCP window would equal ~138,000 bytes.		~1,105,000 bits and the ideal TCP window would equal ~138,000 bytes.
	The following table provides some representative network link speeds,		The following table provides some representative network link speeds,
	latency, BDP, and associated "optimum" TCP window size. Sustained		latency, BDP, and associated "optimum" TCP window size. Sustained
	TCP transfers should reach nearly 100% throughput, minus the overhead		TCP transfers should reach nearly 100% throughput, minus the overhead
	of Layers 1-3 and the divisor of the MSS into the window.		of Layers 1-3 and the divisor of the MSS into the window.
	For this single connection baseline test, the MSS size will effect		For this single connection baseline test, the MSS size will effect
	the achieved throughput (especially for smaller TCP window sizes).		the achieved throughput (especially for smaller TCP window sizes).
	Table 3.2 provides the achievable, equalibrium TCP throughput (at		Table 3.2 provides the achievable, equilibrium TCP throughput (at
	Layer 4) using 1460 byte MSS. Also in this table, the case of 58 byte		Layer 4) using 1460 byte MSS. Also in this table, the 58 byte L1-L4
	L1-L4 overhead including the Ethernet CRC32 is used for simplicity.		overhead including the Ethernet CRC32 is used for simplicity.
	Table 3.2: Link Speed, RTT and calculated BDP, TCP Throughput		Table 3.2: Link Speed, RTT and calculated BDP, TCP Throughput
	Link Ideal TCP Maximum Achievable		Link Ideal TCP Maximum Achievable
	Speed* RTT (ms) BDP (bits) Window (kbytes) TCP Throughput(Mbps)		Speed* RTT (ms) BDP (bits) Window (kbytes) TCP Throughput(Mbps)
	----------------------------------------------------------------------		---------------------------------------------------------------------
	T1 20 30,720 3.84 1.17		T1 20 30,720 3.84 1.17
	T1 50 76,800 9.60 1.40		T1 50 76,800 9.60 1.40
	T1 100 153,600 19.20 1.40		T1 100 153,600 19.20 1.40
	T3 10 442,100 55.26 42.05		T3 10 442,100 55.26 42.05
	T3 15 663,150 82.89 42.05		T3 15 663,150 82.89 42.05
	T3 25 1,105,250 138.16 41.52		T3 25 1,105,250 138.16 41.52
	T3(ATM) 10 407,040 50.88 36.50		T3(ATM) 10 407,040 50.88 36.50
	T3(ATM) 15 610,560 76.32 36.23		T3(ATM) 15 610,560 76.32 36.23
	T3(ATM) 25 1,017,600 127.20 36.27		T3(ATM) 25 1,017,600 127.20 36.27
	100M 1 100,000 12.50 91.98		100M 1 100,000 12.50 91.98
	100M 2 200,000 25.00 93.44		100M 2 200,000 25.00 93.44
	100M 5 500,000 62.50 93.44		100M 5 500,000 62.50 93.44
	1Gig 0.1 100,000 12.50 919.82		1Gig 0.1 100,000 12.50 919.82
	1Gig 0.5 500,000 62.50 934.47		1Gig 0.5 500,000 62.50 934.47
	1Gig 1 1,000,000 125.00 934.47		1Gig 1 1,000,000 125.00 934.47
	10Gig 0.05 500,000 62.50 9,344.67		10Gig 0.05 500,000 62.50 9,344.67
	10Gig 0.3 3,000,000 375.00 9,344.67		10Gig 0.3 3,000,000 375.00 9,344.67
	* Note that link speed is the minimum link speed throughput a network;		* Note that link speed is the minimum link speed throughput a
	i.e. WAN with T1 link, etc.		network; i.e. WAN with T1 link, etc.
	Also, the following link speeds (available payload bandwidth) were		Also, the following link speeds (available payload bandwidth) were
	used for the WAN entries:		used for the WAN entries:
	- T1 = 1.536 Mbits/sec (B8ZS line encoding facility)		- T1 = 1.536 Mbits/sec (B8ZS line encoding facility)
	- T3 = 44.21 Mbits/sec (C-Bit Framing)		- T3 = 44.21 Mbits/sec (C-Bit Framing)
	- T3(ATM) = 36.86 Mbits/sec (C-Bit Framing & PLCP, 96000 Cells per		- T3(ATM) = 36.86 Mbits/sec (C-Bit Framing & PLCP, 96000 Cells per
	second)		second)
	The calculation method used in this document is a 3 step process :		The calculation method used in this document is a 3 step process :
	1 - We determine what should be the optimal TCP Window size value		1 - We determine what should be the optimal TCP Window size value
	based on the optimal quantity of "in-flight" octets discovered by		based on the optimal quantity of "in-flight" octets discovered by
	the BDP calculation. We take into consideration that the TCP		the BDP calculation. We take into consideration that the TCP
	Window size has to be an exact multiple value of the MSS.		Window size has to be an exact multiple value of the MSS.
	2 - Then we calculate the achievable layer 2 throughput by multiplying		2 - Then we calculate the achievable layer 2 throughput by
	the value determined in step 1 with the MSS & (MSS + L2 + L3 + L4		multiplying the value determined in step 1 with the
	Overheads) divided by the RTT.		MSS & (MSS + L2 + L3 + L4 Overheads) divided by the RTT.
	3 - Finally, we multiply the calculated value of step 2 by the MSS		3 - Finally, we multiply the calculated value of step 2 by the MSS
	versus (MSS + L2 + L3 + L4 Overheads) ratio.		versus (MSS + L2 + L3 + L4 Overheads) ratio.
	This gives us the achievable TCP Throughput value. Sometimes, the		This gives us the achievable TCP Throughput value. Sometimes, the
	maximum achievable throughput is limited by the maximum achievable		maximum achievable throughput is limited by the maximum achievable
	quantity of Ethernet Frames per second on the physical media. Then		quantity of Ethernet Frames per second on the physical media. Then
	this value is used in step 2 instead of the calculated one.		this value is used in step 2 instead of the calculated one.
	The following diagram compares achievable TCP throughputs on a T3 link		The following diagram compares achievable TCP throughputs on a T3 link
	with Windows 2000/XP TCP window sizes of 16KB versus 64KB.		with Windows 2000/XP TCP window sizes of 16KB versus 64KB.
	skipping to change at page 14, line 5		skipping to change at page 14, line 5
	| | | | | |64K|		| | | | | |64K|
	15| 14.5M____| | | | | |		15| 14.5M____| | | | | |
	| |16K| | | | | |		| |16K| | | | | |
	10| | | | 9.6M+---+ | | |		10| | | | 9.6M+---+ | | |
	| | | | |16K| | 5.8M____+ |		| | | | |16K| | 5.8M____+ |
	5| | | | | | | |16K| |		5| | | | | | | |16K| |
	|______+___+___+_______+___+___+_______+__ +___+_______		|______+___+___+_______+___+___+_______+__ +___+_______
	10 15 25		10 15 25
	RTT in milliseconds		RTT in milliseconds
	The following diagram shows the achievable TCP throughput on a 25ms T3		The following diagram shows the achievable TCP throughput on a 25ms
	when the TCP Window size is increased and with the RFC1323 TCP Window		T3 when the TCP Window size is increased and with the RFC1323 TCP
	scaling option.		Window scaling option.
	45|		45|
	| +-----+42.47M		| +-----+42.47M
	40| | |		40| | |
	TCP | | |		TCP | | |
	Throughput 35| | |		Throughput 35| | |
	in Mbps | | |		in Mbps | | |
	30| | |		30| | |
	| | |		| | |
	25| | |		25| | |
	| ______ 21.23M | |		| ______ 21.23M | |
	20| | | | |		20| | | | |
	| | | | |		| | | | |
	15| | | | |		15| | | | |
	| | | | |		| | | | |
	10| +----+10.62M | | | |		10| +----+10.62M | | | |
	| _______5.31M | | | | | |		| _______5.31M | | | | | |
	5| | | | | | | | |		5| | | | | | | | |
	|__+_____+______+____+___________+____+________+_____+___		|__+_____+______+____+__________+____+________+_____+___
	16 32 64 128		16 32 64 128
	TCP Window size in KBytes		TCP Window size in KBytes
	3.3.2 Conducting the TCP Throughput Tests		3.3.2 Conducting the TCP Throughput Tests
	There are several TCP tools that are commonly used in the network		There are several TCP tools that are commonly used in the network
	world and one of the most common is the "iperf" tool. With this tool,		world and one of the most common is the "iperf" tool. With this tool,
	hosts are installed at each end of the network segment; one as client		hosts are installed at each end of the network segment; one as client
	and the other as server. The TCP Window size of both the client and		and the other as server. The TCP Window size of both the client and
	the server can be maunally set and the achieved throughput is measured,		the server can be manually set and the achieved throughput is
	either uni-directionally or bi-directionally. For higher BDP		measured, either uni-directionally or bi-directionally. For higher
	situations in lossy networks (long fat networks or satellite links,		BDP situations in lossy networks (long fat networks or satellite
	etc.), TCP options such as Selective Acknowledgment should be		links, etc.), TCP options such as Selective Acknowledgment should be
	considered and also become part of the window size / throughput		considered and also become part of the window size / throughput
	characterization.		characterization.
	Host hardware performance must be well understood before conducting		Host hardware performance must be well understood before conducting
	the TCP throughput tests and other tests in the following sections.		the TCP throughput tests and other tests in the following sections.
	Dedicated test equipment will generally be required, especially for		Dedicated test equipment will generally be required, especially for
	line rates of GigE and 10 GigE.		line rates of GigE and 10 GigE.
	The TCP throughput test should be run over a a long enough duration		The TCP throughput test should be run over a a long enough duration
	to properly exercise network buffers and also characterize performance		to properly exercise network buffers and also characterize
	during different time periods of the day. The results must be logged		performance during different time periods of the day. The results
	at the desired interval and the test must record RTT and TCP		must be logged at the desired interval and the test must record RTT
	retransmissions at each interval.		and TCP retransmissions at each interval.
	This correlation of retransmissions and RTT over the course of the		This correlation of retransmissions and RTT over the course of the
	test will clearly identify which portions of the transfer reached		test will clearly identify which portions of the transfer reached
	TCP Equilbrium state and to what effect increased RTT (congestive		TCP Equilbrium state and to what effect increased RTT (congestive
	effects) may have been the cause of reduced equilibrium performance.		effects) may have been the cause of reduced equilibrium performance.
	Additionally, the TCP Efficiency and TCP Transfer time metrics should		Additionally, the TCP Efficiency and TCP Transfer time metrics should
	be logged in order to further characterize the window size tests.		be logged in order to further characterize the window size tests.
	3.3.3 Single vs. Multiple TCP Connection Testing		3.3.3 Single vs. Multiple TCP Connection Testing
	The decision whether to conduct single or multiple TCP connection		The decision whether to conduct single or multiple TCP connection
	tests depends upon the size of the BDP in relation to the window sizes		tests depends upon the size of the BDP in relation to the window
	configured in the end-user environment. For example, if the BDP for a		sizes configured in the end-user environment. For example, if the
	long-fat pipe turns out to be 2MB, then it is probably more realistic		BDP for a long-fat pipe turns out to be 2MB, then it is probably more
	to test this pipe with multiple connections. Assuming typical host		realistic to test this pipe with multiple connections. Assuming
	computer window settings of 64 KB, using 32 connections would		typical host computer window settings of 64 KB, using 32 connections
	realistically test this pipe.		would realistically test this pipe.
	The following table is provided to illustrate the relationship of the		The following table is provided to illustrate the relationship of the
	BDP, window size, and the number of connections required to utilize the		BDP, window size, and the number of connections required to utilize
	the available capacity. For this example, the network bandwidth is		the available capacity. For this example, the network bandwidth is
	500 Mbps, RTT is equal to 5 ms, and the BDP equates to 312 KBytes.		500 Mbps, RTT is equal to 5 ms, and the BDP equates to 312 KBytes.
	#Connections		#Connections
	Window to Fill Link		Window to Fill Link
	------------------------		------------------------
	16KB 20		16KB 20
	32KB 10		32KB 10
	64KB 5		64KB 5
	128KB 3		128KB 3
	The TCP Transfer Time metric is useful for conducting multiple		The TCP Transfer Time metric is useful for conducting multiple
	connection tests. Each connection should be configured to transfer		connection tests. Each connection should be configured to transfer
	a certain payload (i.e. 100 MB), and the TCP Transfer time provides		a certain payload (i.e. 100 MB), and the TCP Transfer time provides
	a simple metric to verify the actual versus expected results.		a simple metric to verify the actual versus expected results.
	Note that the TCP transfer time is the time for all connections to		Note that the TCP transfer time is the time for all connections to
	complete the transfer of the configured payload size. From the		complete the transfer of the configured payload size. From the
	example table listed above, the 64KB window is considered. Each of		example table listed above, the 64KB window is considered. Each of
	the 5 connections would be configured to transfer 100MB, and each		the 5 connections would be configured to transfer 100MB, and each
	TCP should obtain a maximum of 100 Mb/sec per connection. So for this		TCP should obtain a maximum of 100 Mb/sec per connection. So for
	example, the 100MB payload should be transferred across the connections		this example, the 100MB payload should be transferred across the
	in approximately 8 seconds (which would be the ideal TCP transfer time		connections in approximately 8 seconds (which would be the ideal TCP
	for these conditions).		transfer time for these conditions).
	Additionally, the TCP Efficiency metric should be computed for each		Additionally, the TCP Efficiency metric should be computed for each
	connection tested (defined in section 2.2).		connection tested (defined in section 2.2).
	3.3.4 Interpretation of the TCP Throughput Results		3.3.4 Interpretation of the TCP Throughput Results
	At the end of this step, the user will document the theoretical BDP		At the end of this step, the user will document the theoretical BDP
	and a set of Window size experiments with measured TCP throughput for		and a set of Window size experiments with measured TCP throughput for
	each TCP window size setting. For cases where the sustained TCP		each TCP window size setting. For cases where the sustained TCP
	throughput does not equal the predicted value, some possible causes		throughput does not equal the predicted value, some possible causes
	are listed:		are listed:
	- Network congestion causing packet loss; the TCP Efficiency metric		- Network congestion causing packet loss; the TCP Efficiency metric
	is a useful gauge to compare network performance		is a useful gauge to compare network performance
	- Network congestion not causing packet loss but increasing RTT		- Network congestion not causing packet loss but increasing RTT
	- Intermediate network devices which actively regenerate the TCP		- Intermediate network devices which actively regenerate the TCP
	connection and can alter window size, MSS, etc.		connection and can alter window size, MSS, etc.
	- Over utilization of available link or rate limiting (policing). More		- Over utilization of available link or rate limiting (policing).
	discussion of traffic management tests follows in section 3.4		More discussion of traffic management tests follows in section 3.4
	3.4. Traffic Management Tests		3.4. Traffic Management Tests
	In most cases, the network connection between two geographic locations		In most cases, the network connection between two geographic
	(branch offices, etc.) is lower than the network connection of the		locations (branch offices, etc.) is lower than the network connection
	host computers. An example would be LAN connectivity of GigE and		of the host computers. An example would be LAN connectivity of GigE
	WAN connectivity of 100 Mbps. The WAN connectivity may be physically		and WAN connectivity of 100 Mbps. The WAN connectivity may be
	100 Mbps or logically 100 Mbps (over a GigE WAN connection). In the		physically 100 Mbps or logically 100 Mbps (over a GigE WAN
	later case, rate limiting is used to provide the WAN bandwidth per the		connection). In the later case, rate limiting is used to provide the
	SLA.		WAN bandwidth per the SLA.
	Traffic management techniques are employed to provide various forms of		Traffic management techniques are employed to provide various forms
	QoS, the more common include:		of QoS, the more common include:
	- Traffic Shaping		- Traffic Shaping
	- Priority Queuing		- Priority Queueing
	- Random Early Discard (RED, etc.)		- Random Early Discard (RED, etc.)
	Configuring the end-end network with these various traffic management		Configuring the end-end network with these various traffic management
	mechanisms is a complex under-taking. For traffic shaping and RED		mechanisms is a complex under-taking. For traffic shaping and RED
	techniques, the end goal is to provide better performance for bursty		techniques, the end goal is to provide better performance for bursty
	traffic such as TCP (RED is specifically intended for TCP).		traffic such as TCP (RED is specifically intended for TCP).
	This section of the methodology provides guidelines to test traffic		This section of the methodology provides guidelines to test traffic
	shaping and RED implementations. As in section 3.3, host hardware		shaping and RED implementations. As in section 3.3, host hardware
	performance must be well understood before conducting the traffic		performance must be well understood before conducting the traffic
	skipping to change at page 17, line 14		skipping to change at page 17, line 14
	Simply stated, traffic policing marks and/or drops packets which		Simply stated, traffic policing marks and/or drops packets which
	exceed the SLA bandwidth (in most cases, excess traffic is dropped).		exceed the SLA bandwidth (in most cases, excess traffic is dropped).
	Traffic shaping employs the use of queues to smooth the bursty		Traffic shaping employs the use of queues to smooth the bursty
	traffic and then send out within the SLA bandwidth limit (without		traffic and then send out within the SLA bandwidth limit (without
	dropping packets unless the traffic shaping queue is exceeded).		dropping packets unless the traffic shaping queue is exceeded).
	Traffic shaping is generally configured for TCP data services and		Traffic shaping is generally configured for TCP data services and
	can provide improved TCP performance since the retransmissions are		can provide improved TCP performance since the retransmissions are
	reduced, which in turn optimizes TCP throughput for the given		reduced, which in turn optimizes TCP throughput for the given
	available bandwidth. Through this section, the available rate-limited		available bandwidth. Through this section, the available
	bandwidth shall be referred to as the "bottleneck bandwidth".		rate-limited bandwidth shall be referred to as the
			"bottleneck bandwidth".
	The ability to detect proper traffic shaping is more easily diagnosed		The ability to detect proper traffic shaping is more easily diagnosed
	when conducting a multiple TCP connection test. Proper shaping will		when conducting a multiple TCP connection test. Proper shaping will
	provide a fair distribution of the available bottleneck bandwidth,		provide a fair distribution of the available bottleneck bandwidth,
	while traffic policing will not.		while traffic policing will not.
	The traffic shaping tests build upon the concepts of multiple		The traffic shaping tests build upon the concepts of multiple
	connection testing as defined in section 3.3.3. Calculating the BDP		connection testing as defined in section 3.3.3. Calculating the BDP
	for the bottleneck bandwidth is first required and then selecting		for the bottleneck bandwidth is first required and then selecting
	the number of connections / window size per connection.		the number of connections / window size per connection.
	Similar to the example in section 3.3, a typical test scenario might		Similar to the example in section 3.3, a typical test scenario might
	be: GigE LAN with a 100Mbps bottleneck bandwidth (rate limited logical		be: GigE LAN with a 100Mbps bottleneck bandwidth (rate limited
	interface), and 5 msec RTT. This would require five (5) TCP		logical interface), and 5 msec RTT. This would require five (5) TCP
	connections of 64 KB window size evenly fill the bottleneck bandwidth		connections of 64 KB window size evenly fill the bottleneck bandwidth
	(about 100 Mbps per connection).		(about 100 Mbps per connection).
	The traffic shaping should be run over a long enough duration to		The traffic shaping should be run over a long enough duration to
	properly exercise network buffers and also characterize performance		properly exercise network buffers and also characterize performance
	during different time periods of the day. The throughput of each		during different time periods of the day. The throughput of each
	connection must be logged during the entire test, along with the TCP		connection must be logged during the entire test, along with the TCP
	Efficiency and TCP Transfer time metric. Additionally, it is		Efficiency and TCP Transfer time metric. Additionally, it is
	recommended to log RTT and retransmissions per connection over the test		recommended to log RTT and retransmissions per connection over the
	interval.		test interval.
	3.4.1.1 Interpretation of Traffic Shaping Test Restults		3.4.1.1 Interpretation of Traffic Shaping Test Restults
	By plotting the throughput achieved by each TCP connection, the fair		By plotting the throughput achieved by each TCP connection, the fair
	sharing of the bandwidth is generally very obvious when traffic shaping		sharing of the bandwidth is generally very obvious when traffic
	is properly configured for the bottleneck interface. For the previous		shaping is properly configured for the bottleneck interface. For the
	example of 5 connections sharing 500 Mbps, each connection would		previous example of 5 connections sharing 500 Mbps, each connection
	consume ~100 Mbps with a smooth variation. If traffic policing was		would consume ~100 Mbps with a smooth variation. If traffic policing
	present on the bottleneck interface, the bandwidth sharing would not		was present on the bottleneck interface, the bandwidth sharing would
	be fair and the resulting throughput plot would reveal "spikey"		not be fair and the resulting throughput plot would reveal "spikey"
	connection throughput consumption of the competing TCP connections		throughput consumption of the competing TCP connections (due to the
	(due to the retransmissions).		retransmissions).
	3.4.2 RED Tests		3.4.2 RED Tests
	Random Early Discard techniques are specifically targeted to provide		Random Early Discard techniques are specifically targeted to provide
	congestion avoidance for TCP traffic. Before the network element queue		congestion avoidance for TCP traffic. Before the network element
	"fills" and enters the tail drop state, RED drops packets at		queue "fills" and enters the tail drop state, RED drops packets at
	configurable queue depth thresholds. This action causes TCP		configurable queue depth thresholds. This action causes TCP
	connections to back-off which helps to prevent tail drop, which in		connections to back-off which helps to prevent tail drop, which in
	turn helps to prevent global TCP synchronization.		turn helps to prevent global TCP synchronization.
	Again, rate limited interfaces can benefit greatly from RED based		Again, rate limited interfaces can benefit greatly from RED based
	techniques. Without RED, TCP is generally not able to achieve the full		techniques. Without RED, TCP is generally not able to achieve the
	bandwidth of the bottleneck interface. With RED enabled, TCP		full bandwidth of the bottleneck interface. With RED enabled, TCP
	congestion avoidance throttles the connections on the higher speed		congestion avoidance throttles the connections on the higher speed
	interface (i.e. LAN) and can reach equalibrium with the bottleneck		interface (i.e. LAN) and can reach equalibrium with the bottleneck
	bandwidth (achieving closer to full throughput).		bandwidth (achieving closer to full throughput).
	The ability to detect proper RED configuration is more easily diagnosed		The ability to detect proper RED configuration is more easily
	when conducting a multiple TCP connection test. Multiple TCP		diagnosed when conducting a multiple TCP connection test. Multiple
	connections provide the multiple bursty sources that emulate the		TCP connections provide the multiple bursty sources that emulate the
	real-world conditions for which RED was intended.		real-world conditions for which RED was intended.
	The RED tests also build upon the concepts of multiple connection		The RED tests also build upon the concepts of multiple connection
	testing as defined in secion 3.3.3. Calculating the BDP for the		testing as defined in secion 3.3.3. Calculating the BDP for the
	bottleneck bandwidth is first required and then selecting the number of		bottleneck bandwidth is first required and then selecting the number
	connections / window size per connection.		of connections / window size per connection.
	For RED testing, the desired effect is to cause the TCP connections to		For RED testing, the desired effect is to cause the TCP connections
	burst beyond the bottleneck bandwidth so that queue drops will occur.		to burst beyond the bottleneck bandwidth so that queue drops will
	Using the same example from section 3.4.1 (traffic shaping), the		occur. Using the same example from section 3.4.1 (traffic shaping),
	500 Mbps bottleneck bandwidth requires 5 TCP connections (with window		the 500 Mbps bottleneck bandwidth requires 5 TCP connections (with
	size of 64Kb) to fill the capacity. Some experimentation is required,		window size of 64Kb) to fill the capacity. Some experimentation is
	but it is recommended to start with double the number of connections		required,but it is recommended to start with double the number of
	to stress the network element buffers / queues. In this example, 10		connections to stress the network element buffers / queues. In this
	connections would produce TCP bursts of 64KB for each connection.		example, 10 connections would produce TCP bursts of 64KB for each
	If the timing of the TCP tester permits, these TCP bursts could stress		connection. If the timing of the TCP tester permits, these TCP
	queue sizes in the 512KB range. Again experimentation will be required		bursts could stress queue sizes in the 512KB range. Again
	and the proper number of TCP connections / window size will be dictated		experimentation will be required and the proper number of TCP
	by the size the network element queue.		connections / window size will be dictated by the size the network
			element queue.
	3.4.2.1 Interpretation of RED Results		3.4.2.1 Interpretation of RED Results
	The default queuing technique for most network devices is FIFO based.		The default queuing technique for most network devices is FIFO based.
	Without RED, the FIFO based queue will cause excessive loss to all of		Without RED, the FIFO based queue will cause excessive loss to all of
	the TCP connections and in the worst case global TCP synchronization.		the TCP connections and in the worst case global TCP synchronization.
	By plotting the aggregate throughput achieved on the bottleneck		By plotting the aggregate throughput achieved on the bottleneck
	interface, proper RED operation can be determined if the bottleneck		interface, proper RED operation can be determined if the bottleneck
	bandwidth is fully utilized. For the previous example of 10		bandwidth is fully utilized. For the previous example of 10
	connections (window = 64 KB) sharing 500 Mbps, each connection should		connections (window = 64 KB) sharing 500 Mbps, each connection should
	consume ~50 Mbps. If RED was not properly enabled on the interface,		consume ~50 Mbps. If RED was not properly enabled on the interface,
	then the TCP connections will retransmit at a higher rate and the net		then the TCP connections will retransmit at a higher rate and the net
	effect is that the bottleneck bandwidth is not fully utilized.		effect is that the bottleneck bandwidth is not fully utilized.
	Another means to study non-RED versus RED implementation is to use		Another means to study non-RED versus RED implementation is to use
	the TCP Transfer Time metric for all of the connections. In this		the TCP Transfer Time metric for all of the connections. In this
	example, a 100 MB payload transfer should take ideally 16 seconds		example, a 100 MB payload transfer should take ideally 16 seconds
	across all 10 connections (with RED enabled). With RED not enabled,		across all 10 connections (with RED enabled). With RED not enabled,
	the throughput across the bottleneck bandwidth would be greatly reduced		the throughput across the bottleneck bandwidth would be greatly
	(generally 20-40%) and the TCP Transfer time would be proportionally		reduced (generally 20-40%) and the TCP Transfer time would be
	longer then the ideal transfer time.		proportionally longer then the ideal transfer time.
	Additionally, the TCP Transfer Efficiency metric is useful, since		Additionally, the TCP Transfer Efficiency metric is useful, since
	non-RED implementations will exhibit a lower TCP Tranfer Efficiency		non-RED implementations will exhibit a lower TCP Tranfer Efficiency
	than RED implementations.		than RED implementations.
	4. Acknowledgements		4. Security Considerations
			The security considerations that apply to any active measurement of
			live networks are relevant here as well. See [RFC4656] and
			[RFC5357].
			5. IANA Considerations
			This memo does not require and IANA registration for ports dedicated
			to the TCP testing described in this memo.
			6. Acknowledgements
	The author would like to thank Gilles Forget, Loki Jorgenson,		The author would like to thank Gilles Forget, Loki Jorgenson,
	and Reinhard Schrage for technical review and original contributions		and Reinhard Schrage for technical review and original contributions
	to this draft-03.		to this draft-06.
	Also thanks to Matt Mathis and Matt Zekauskas for many good comments		Also thanks to Matt Mathis, Matt Zekauskas, Al Morton, and Yaakov
	through email exchange and for pointing us to great sources of		Stein for many good comments and for pointing us to great sources of
	information pertaining to past works in the TCP capacity area.		information pertaining to past works in the TCP capacity area.
	5. References		7. References
	[RFC2581] Allman, M., Paxson, V., Stevens W., "TCP Congestion		7.1 Normative References
	Control", RFC 2581, June 1999.
			[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
			Requirement Levels", BCP 14, RFC 2119, March 1997.
			[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
			Zekauskas, "A One-way Active Measurement Protocol
			(OWAMP)", RFC 4656, September 2006.
			[RFC5681] Allman, M., Paxson, V., Stevens W., "TCP Congestion
			Control", RFC 5681, September 2009.
	[RFC3148] Mathis M., Allman, M., "A Framework for Defining
	Empirical Bulk Transfer Capacity Metrics", RFC 3148, July
	2001.
	[RFC2544] Bradner, S., McQuaid, J., "Benchmarking Methodology for		[RFC2544] Bradner, S., McQuaid, J., "Benchmarking Methodology for
	Network Interconnect Devices", RFC 2544, June 1999		Network Interconnect Devices", RFC 2544, June 1999
	[RFC3449] Balakrishnan, H., Padmanabhan, V. N., Fairhurst, G.,		[RFC3449] Balakrishnan, H., Padmanabhan, V. N., Fairhurst, G.,
	Sooriyabandara, M., "TCP Performance Implications of		Sooriyabandara, M., "TCP Performance Implications of
	Network Path Asymmetry", RFC 3449, December 2002		Network Path Asymmetry", RFC 3449, December 2002
	[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., Babiarz,		[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., Babiarz,
	J., "A Two-Way Active Measurement Protocol (TWAMP)",		J., "A Two-Way Active Measurement Protocol (TWAMP)",
	RFC 5357, October 2008		RFC 5357, October 2008
	skipping to change at page 20, line 4		skipping to change at page 20, line 21
	[RFC3449] Balakrishnan, H., Padmanabhan, V. N., Fairhurst, G.,		[RFC3449] Balakrishnan, H., Padmanabhan, V. N., Fairhurst, G.,
	Sooriyabandara, M., "TCP Performance Implications of		Sooriyabandara, M., "TCP Performance Implications of
	Network Path Asymmetry", RFC 3449, December 2002		Network Path Asymmetry", RFC 3449, December 2002
	[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., Babiarz,		[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., Babiarz,
	J., "A Two-Way Active Measurement Protocol (TWAMP)",		J., "A Two-Way Active Measurement Protocol (TWAMP)",
	RFC 5357, October 2008		RFC 5357, October 2008
	[RFC4821] Mathis, M., Heffner, J., "Packetization Layer Path MTU		[RFC4821] Mathis, M., Heffner, J., "Packetization Layer Path MTU
	Discovery", RFC 4821, June 2007		Discovery", RFC 4821, June 2007
	draft-ietf-ippm-btc-cap-00.txt Allman, M., "A Bulk		draft-ietf-ippm-btc-cap-00.txt Allman, M., "A Bulk
	Transfer Capacity Methodology for Cooperating Hosts",		Transfer Capacity Methodology for Cooperating Hosts",
	August 2001		August 2001
	[MSMO] The Macroscopic Behavior of the TCP Congestion Avoidance		7.2. Informative References
	Algorithm Mathis, M.,Semke, J, Mahdavi, J, Ott, T
	July 1997 SIGCOMM Computer Communication Review,
	Volume 27 Issue 3
	[Stevens Vol1] TCP/IP Illustrated, Vol1, The Protocols
	Addison-Wesley
	Authors' Addresses		Authors' Addresses
	Barry Constantine		Barry Constantine
	JDSU, Test and Measurement Division		JDSU, Test and Measurement Division
	One Milesone Center Court		One Milesone Center Court
	Germantown, MD 20876-7100		Germantown, MD 20876-7100
	USA		USA
	Phone: +1 240 404 2227		Phone: +1 240 404 2227
End of changes. 75 change blocks.
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