draft-ietf-ippm-connectivity-02.txt		draft-ietf-ippm-connectivity-03.txt
	Network Working Group J. Mahdavi, Pittsburgh Supercomputer Center		Network Working Group J. Mahdavi, Pittsburgh Supercomputer Center
	Internet Draft V. Paxson, Lawrence Berkeley National Laboratory		Internet Draft V. Paxson, Lawrence Berkeley National Laboratory
	Expiration Date: February 1999 August 1998		Expiration Date: April 1999 October 1998
	IPPM Metrics for Measuring Connectivity		IPPM Metrics for Measuring Connectivity
	<draft-ietf-ippm-connectivity-02.txt>		<draft-ietf-ippm-connectivity-03.txt>
	1. Status of this Memo		1. Status of this Memo
	This document is an Internet Draft. Internet Drafts are working		This document is an Internet Draft. Internet Drafts are working
	documents of the Internet Engineering Task Force (IETF), its areas,		documents of the Internet Engineering Task Force (IETF), its areas,
	and its working groups. Note that other groups may also distribute		and its working groups. Note that other groups may also distribute
	working documents as Internet Drafts.		working documents as Internet Drafts.
	Internet Drafts are draft documents valid for a maximum of six		Internet Drafts are draft documents valid for a maximum of six
	months, and may be updated, replaced, or obsoleted by other documents		months, and may be updated, replaced, or obsoleted by other documents
	skipping to change at page 2, line 5		skipping to change at page 2, line 5
	define several such metrics, some of which serve mainly as building		define several such metrics, some of which serve mainly as building
	blocks for the others.		blocks for the others.
	This memo defines a series of metrics for connectivity between a pair		This memo defines a series of metrics for connectivity between a pair
	of Internet hosts. It builds on notions introduced and discussed in		of Internet hosts. It builds on notions introduced and discussed in
	RFC 2330, the IPPM framework document. The reader is assumed to be		RFC 2330, the IPPM framework document. The reader is assumed to be
	familiar with that document.		familiar with that document.
	The structure of the memo is as follows:		The structure of the memo is as follows:
	ID IPPM Metrics for Measuring Connectivity August 1998		ID IPPM Metrics for Measuring Connectivity October 1998
	+ An analytic metric, called Type-P-Instantaneous-Unidirectional-		+ An analytic metric, called Type-P-Instantaneous-Unidirectional-
	Connectivity, will be introduced to define one-way connectivity at		Connectivity, will be introduced to define one-way connectivity at
	one moment in time.		one moment in time.
	+ Using this metric, another analytic metric, called Type-P-		+ Using this metric, another analytic metric, called Type-P-
	Instantaneous-Bidirectional-Connectivity, will be introduced to		Instantaneous-Bidirectional-Connectivity, will be introduced to
	define two-way connectivity at one moment in time.		define two-way connectivity at one moment in time.
	+ Using these metrics, corresponding one- and two-way analytic		+ Using these metrics, corresponding one- and two-way analytic
	metrics are defined for connectivity over an interval of time.		metrics are defined for connectivity over an interval of time.
	+ Using these metrics, an analytic metric, called Type-P1-P2-		+ Using these metrics, an analytic metric, called Type-P1-P2-
	skipping to change at page 3, line 5		skipping to change at page 3, line 5
	3.3. Metric Units:		3.3. Metric Units:
	Boolean.		Boolean.
	3.4. Definition:		3.4. Definition:
	Src has *Type-P-Instantaneous-Unidirectional-Connectivity* to Dst at		Src has *Type-P-Instantaneous-Unidirectional-Connectivity* to Dst at
	time T if a type-P packet transmitted from Src to Dst at time T will		time T if a type-P packet transmitted from Src to Dst at time T will
	arrive at Dst.		arrive at Dst.
	ID IPPM Metrics for Measuring Connectivity August 1998		ID IPPM Metrics for Measuring Connectivity October 1998
	3.5. Discussion:		3.5. Discussion:
	For most applications (e.g., any TCP connection) bidirectional		For most applications (e.g., any TCP connection) bidirectional
	connectivity is considerably more germane than unidirectional		connectivity is considerably more germane than unidirectional
	connectivity, although unidirectional connectivity can be of interest		connectivity, although unidirectional connectivity can be of interest
	for some security applications (e.g., testing whether a firewall		for some security applications (e.g., testing whether a firewall
	correctly filters out a "ping of death"). Most applications also		correctly filters out a "ping of death"). Most applications also
	require connectivity over an interval, while this metric is		require connectivity over an interval, while this metric is
	instantaneous, though, again, for some security applications		instantaneous, though, again, for some security applications
	skipping to change at page 4, line 5		skipping to change at page 4, line 5
	the unidirectional connectivity defined in this metric.		the unidirectional connectivity defined in this metric.
	4. Instantaneous Two-way Connectivity		4. Instantaneous Two-way Connectivity
	4.1. Metric Name:		4.1. Metric Name:
	Type-P-Instantaneous-Bidirectional-Connectivity		Type-P-Instantaneous-Bidirectional-Connectivity
	4.2. Metric Parameters:		4.2. Metric Parameters:
	ID IPPM Metrics for Measuring Connectivity August 1998		ID IPPM Metrics for Measuring Connectivity October 1998
	+ A1, the IP address of a host		+ A1, the IP address of a host
	+ A2, the IP address of a host		+ A2, the IP address of a host
	+ T, a time		+ T, a time
	4.3. Metric Units:		4.3. Metric Units:
	Boolean.		Boolean.
	4.4. Definition:		4.4. Definition:
	skipping to change at page 5, line 5		skipping to change at page 5, line 5
	5. One-way Connectivity		5. One-way Connectivity
	5.1. Metric Name:		5.1. Metric Name:
	Type-P-Interval-Unidirectional-Connectivity		Type-P-Interval-Unidirectional-Connectivity
	5.2. Metric Parameters:		5.2. Metric Parameters:
	+ Src, the IP address of a host		+ Src, the IP address of a host
	ID IPPM Metrics for Measuring Connectivity August 1998		ID IPPM Metrics for Measuring Connectivity October 1998
	+ Dst, the IP address of a host		+ Dst, the IP address of a host
	+ T, a time		+ T, a time
	+ dT, a duration		+ dT, a duration
	{Comment: Thus, the closed interval [T, T+dT] denotes a time		{Comment: Thus, the closed interval [T, T+dT] denotes a time
	interval.}		interval.}
	5.3. Metric Units:		5.3. Metric Units:
	Boolean.		Boolean.
	skipping to change at page 6, line 5		skipping to change at page 6, line 5
	Boolean.		Boolean.
	6.4. Definition:		6.4. Definition:
	Addresses A1 and A2 have *Type-P-Interval-Bidirectional-Connectivity*		Addresses A1 and A2 have *Type-P-Interval-Bidirectional-Connectivity*
	between them during the interval [T, T+dT] if address A1 has Type-P-		between them during the interval [T, T+dT] if address A1 has Type-P-
	Interval-Unidirectional-Connectivity to address A2 during the		Interval-Unidirectional-Connectivity to address A2 during the
	interval and address A2 has Type-P-Interval-Unidirectional-		interval and address A2 has Type-P-Interval-Unidirectional-
	Connectivity to address A1 during the interval.		Connectivity to address A1 during the interval.
	ID IPPM Metrics for Measuring Connectivity August 1998		ID IPPM Metrics for Measuring Connectivity October 1998
	6.5. Discussion:		6.5. Discussion:
	This metric is not quite what's needed for defining "generally		This metric is not quite what's needed for defining "generally
	useful" connectivity - that requires the notion that a packet sent		useful" connectivity - that requires the notion that a packet sent
	from A1 to A2 can elicit a response from A2 that will reach A1. With		from A1 to A2 can elicit a response from A2 that will reach A1. With
	this definition, it could be that A1 and A2 have full-connectivity		this definition, it could be that A1 and A2 have full-connectivity
	but only, for example, at at time T1 early enough in the interval [T,		but only, for example, at at time T1 early enough in the interval [T,
	T+dT] that A1 and A2 cannot reply to packets sent by the other. This		T+dT] that A1 and A2 cannot reply to packets sent by the other. This
	deficiency motivates the next metric.		deficiency motivates the next metric.
	skipping to change at page 7, line 5		skipping to change at page 7, line 5
	Address Src has *Type-P1-P2-Interval-Temporal-Connectivity* to		Address Src has *Type-P1-P2-Interval-Temporal-Connectivity* to
	address Dst during the interval [T, T+dT] if there exist times T1 and		address Dst during the interval [T, T+dT] if there exist times T1 and
	T2, and time intervals dT1 and dT2, such that:		T2, and time intervals dT1 and dT2, such that:
	+ T1, T1+dT1, T2, T2+dT2 are all in [T, T+dT].		+ T1, T1+dT1, T2, T2+dT2 are all in [T, T+dT].
	+ T1+dT1 <= T2.		+ T1+dT1 <= T2.
	+ At time T1, Src has Type-P1 instantanous connectivity to Dst.		+ At time T1, Src has Type-P1 instantanous connectivity to Dst.
	+ At time T2, Dst has Type-P2 instantanous connectivity to Src.		+ At time T2, Dst has Type-P2 instantanous connectivity to Src.
	+ dT1 is the time taken for a Type-P1 packet sent by Src at time T1		+ dT1 is the time taken for a Type-P1 packet sent by Src at time T1
	to arrive at Dst.		to arrive at Dst.
	ID IPPM Metrics for Measuring Connectivity August 1998		ID IPPM Metrics for Measuring Connectivity October 1998
	+ dT2 is the time taken for a Type-P2 packet sent by Dst at time T2		+ dT2 is the time taken for a Type-P2 packet sent by Dst at time T2
	to arrive at Src.		to arrive at Src.
	7.5. Discussion:		7.5. Discussion:
	This metric defines "generally useful" connectivity -- Src can send a		This metric defines "generally useful" connectivity -- Src can send a
	packet to Dst that elicits a response. Because many applications		packet to Dst that elicits a response. Because many applications
	utilize different types of packets for forward and reverse traffic,		utilize different types of packets for forward and reverse traffic,
	it is possible (and likely) that the desired responses to a Type-P1		it is possible (and likely) that the desired responses to a Type-P1
	skipping to change at page 8, line 5		skipping to change at page 8, line 5
	dT = 60 seconds.		dT = 60 seconds.
	W = 10 seconds.		W = 10 seconds.
	N = 20 packets.		N = 20 packets.
	7.6.3. Algorithm:		7.6.3. Algorithm:
	+ Compute N *sending-times* that are randomly, uniformly distributed		+ Compute N *sending-times* that are randomly, uniformly distributed
	over [T, T+dT-W].		over [T, T+dT-W].
	ID IPPM Metrics for Measuring Connectivity August 1998		ID IPPM Metrics for Measuring Connectivity October 1998
	+ At each sending time, transmit from A1 a well-formed packet of		+ At each sending time, transmit from A1 a well-formed packet of
	type P1 to A2.		type P1 to A2.
	+ Inspect incoming network traffic to A1 to determine if a		+ Inspect incoming network traffic to A1 to determine if a
	successful reply is received. The particulars of doing so are		successful reply is received. The particulars of doing so are
	dependent on types P1 & P2, discussed below. If a successful		dependent on types P1 & P2, discussed below. If a successful
	reply is received, the value of the measurement is "true".		reply is received, the value of the measurement is "true".
	+ If no successful replies are received by time T+dT, the value of		+ If no successful replies are received by time T+dT, the value of
	the measurement is "false".		the measurement is "false".
	skipping to change at page 8, line 32		skipping to change at page 8, line 32
	yet offer solid guidance for picking N. The values given above are		yet offer solid guidance for picking N. The values given above are
	just guidelines.		just guidelines.
	7.6.5. Specific methodology for TCP:		7.6.5. Specific methodology for TCP:
	A TCP-port-N1-port-N2 methodology sends TCP SYN packets with source		A TCP-port-N1-port-N2 methodology sends TCP SYN packets with source
	port N1 and dest port N2 at address A2. Network traffic incoming to		port N1 and dest port N2 at address A2. Network traffic incoming to
	A1 is interpreted as follows:		A1 is interpreted as follows:
	+ A SYN-ack packet from A2 to A1 with the proper acknowledgement		+ A SYN-ack packet from A2 to A1 with the proper acknowledgement
	fields and ports indicates temporal connectivity. The measurement		fields and ports indicates temporal connectivity. The measurement
	terminates immediately with a value of "true". {Comment: the		terminates immediately with a value of "true". {Comment: if, as a
	connection now established between A1 and A2 should be properly		side effect of the methodology, a full TCP connection has been
	torn down using the usual FIN handshake (not by using a RST		established between A1 and A2 -- that is, if A1's TCP stack
	packet, as these are not transmitted reliably).}		acknowledges A2's SYN-ack packet, completing the three-way
			handshake -- then the connection now established between A1 and A2
			is best torn down using the usual FIN handshake, and not using a
			RST packet, because RST packets are not reliably delivered. If
			the three-way handshake is not completed, however, which will
			occur if the measurement tool on A1 synthesizes its own initial
			SYN packet rather than going through A1's TCP stack, then A1's TCP
			stack will automatically terminate the connection in a reliable
			fashion as A2 continues transmitting the SYN-ack in an attempt to
			establish the connection. Finally, we note that using A1's TCP
			stack to conduct the measurement complicates the methodology in
			that the stack may retransmit the initial SYN packet, altering the
			number of probe packets sent.}
			ID IPPM Metrics for Measuring Connectivity October 1998
	+ A RST packet from A2 to A1 with the proper ports indicates		+ A RST packet from A2 to A1 with the proper ports indicates
	temporal connectivity between the addresses (and a *lack* of		temporal connectivity between the addresses (and a *lack* of
	service connectivity for TCP-port-N1-port-N2 - something that		service connectivity for TCP-port-N1-port-N2 - something that
	probably should be addressed with another metric).		probably should be addressed with another metric).
	+ An ICMP port-unreachable from A2 to A1 indicates temporal		+ An ICMP port-unreachable from A2 to A1 indicates temporal
	connectivity between the addresses (and again a *lack* of service		connectivity between the addresses (and again a *lack* of service
	connectivity for TCP-port-N1-port-N2). {Comment: TCP		connectivity for TCP-port-N1-port-N2). {Comment: TCP
	implementations generally do not need to send ICMP port-		implementations generally do not need to send ICMP port-
	unreachable messages because a separate mechanism is available		unreachable messages because a separate mechanism is available
	(sending a RST). However, RFC 1122 states that a TCP receiving an		(sending a RST). However, RFC 1122 states that a TCP receiving an
	ICMP port-unreachable MUST treat it the same as the equivalent		ICMP port-unreachable MUST treat it the same as the equivalent
	transport-level mechanism (for TCP, a RST).}		transport-level mechanism (for TCP, a RST).}
	ID IPPM Metrics for Measuring Connectivity August 1998
	+ An ICMP host-unreachable or network-unreachable to A1 (not		+ An ICMP host-unreachable or network-unreachable to A1 (not
	necessarily from A2) with an enclosed IP header matching that sent		necessarily from A2) with an enclosed IP header matching that sent
	from A1 to A2 *suggests* a lack of temporal connectivity. If by		from A1 to A2 *suggests* a lack of temporal connectivity. If by
	time T+dT no evidence of temporal connectivity has been gathered,		time T+dT no evidence of temporal connectivity has been gathered,
	then the receipt of the ICMP can be used as additional information		then the receipt of the ICMP can be used as additional information
	to the measurement value of "false".		to the measurement value of "false".
	{Comment: Similar methodologies are needed for ICMP Echo, UDP, etc.}		{Comment: Similar methodologies are needed for ICMP Echo, UDP, etc.}
	8. Security Considerations		8. Acknowledgments
			The comments of Guy Almes, Martin Horneffer, Jeff Sedayao, and Sean
			Shapira are appreciated.
			9. Security Considerations
	As noted in RFC 2330, active measurement techniques, such as those		As noted in RFC 2330, active measurement techniques, such as those
	defined in this document, can be abused for denial-of-service attacks		defined in this document, can be abused for denial-of-service attacks
	disguised as legitimate measurement activity. Furthermore, testing		disguised as legitimate measurement activity. Furthermore, testing
	for connectivity can be used to probe firewalls and other security		for connectivity can be used to probe firewalls and other security
	mechnisms for weak spots.		mechnisms for weak spots.
	9. References		10. References
	F. Baker, "Requirements for IP Version 4 Routers", RFC 1812, June		F. Baker, "Requirements for IP Version 4 Routers", RFC 1812, June
	1995.		1995.
	R. Braden, "Requirements for Internet hosts - communication layers",		R. Braden, "Requirements for Internet hosts - communication layers",
	RFC 1122, October 1989.		RFC 1122, October 1989.
	V. Paxson, G. Almes, J. Mahdavi, and M. Mathis, Paxson, "Framework		V. Paxson, G. Almes, J. Mahdavi, and M. Mathis, Paxson, "Framework
	for IP Performance Metrics", RFC 2330, May 1998.		for IP Performance Metrics", RFC 2330, May 1998.
			ID IPPM Metrics for Measuring Connectivity October 1998
	J. Postel, "Internet Protocol", RFC 791, September 1981.		J. Postel, "Internet Protocol", RFC 791, September 1981.
	10. Authors' Addresses		11. Authors' Addresses
	Jamshid Mahdavi <mahdavi@psc.edu>		Jamshid Mahdavi <mahdavi@psc.edu>
	Pittsburgh Supercomputing Center		Pittsburgh Supercomputing Center
	4400 5th Avenue		4400 5th Avenue
	Pittsburgh, PA 15213		Pittsburgh, PA 15213
	USA		USA
	Vern Paxson <vern@ee.lbl.gov>		Vern Paxson <vern@ee.lbl.gov>
	MS 50A-3111		MS 50A-3111
	Lawrence Berkeley National Laboratory		Lawrence Berkeley National Laboratory
	University of California		University of California
	Berkeley, CA 94720		Berkeley, CA 94720
	ID IPPM Metrics for Measuring Connectivity August 1998
	USA		USA
	Phone: +1 510/486-7504		Phone: +1 510/486-7504
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