Network Working Group
   INTERNET-DRAFT
   Expires in: October December 2005
                                                   Scott Poretsky
                                                   Quarry Technologies

                                                   Brent Imhoff
						   LightCore

						   February

						   June 2005

             	  	Terminology for Benchmarking
		      IGP Data Plane Route Convergence

		<draft-ietf-bmwg-igp-dataplane-conv-term-05.txt>

		<draft-ietf-bmwg-igp-dataplane-conv-term-06.txt>

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   ABSTRACT
   This draft describes the terminology for benchmarking IGP Route
   Convergence as described in Applicability document [1] and
   Methodology document [2].  The methodology and terminology is to
   be used for benchmarking Route Convergence and can be applied to
   any link-state IGP such as ISIS [3] and OSPF [4].  The data plane
   is measured to obtain the convergence benchmarking metrics
   described in [2].

           	      IGP Data Plane Route Convergence

   Table of Contents

     1. Introduction .................................................2
     2. Existing definitions .........................................3
     3. Term definitions..............................................3
        3.1 Convergence Event.........................................3
        3.2 Route Convergence.........................................4
        3.3 Network Convergence.......................................4
        3.4 Full Convergence..........................................5
        3.5 Convergence Packet Loss...................................5
        3.6 Convergence Event Instant.................................6
        3.7 Convergence Recovery Instant..............................6
        3.8 Rate-Derived Convergence Time.............................7
        3.9 Convergence Event Transition..............................7
        3.10 Convergence Recovery Transition..........................8
        3.11 Loss-Derived Convergence Time............................8
        3.12 Sustained Forwarding Convergence Time....................9
        3.13 Restoration Convergence Time.............................9
        3.14 Packet Sampling Interval.................................10
        3.15 Local Interface..........................................11
        3.16 Neighbor Interface.......................................11
        3.17 Remote Interface.........................................11
        3.18 Preferred Egress Interface...............................12
        3.19 Next-Best Egress Interface...............................12
        3.20 Stale Forwarding.........................................13
        3.21 Nested Convergence Events................................13
     4. Security Considerations.......................................13
     5. Normative References..........................................14
     6. Author's Address..............................................14

   1. Introduction
   This draft describes the terminology for benchmarking IGP Route
   Convergence.  The motivation and applicability for this
   benchmarking is provided in [1].  The methodology to be used for
   this benchmarking is described in [2].  The methodology and
   terminology to be used for benchmarking Route Convergence can be
   applied to any link-state IGP such as ISIS [3] and OSPF [4].  The
   data plane is measured to obtain black-box (externally observable)
   convergence benchmarking metrics.  The purpose of this document is
   to introduce new terms required to complete execution of the IGP
   Route Convergence Methodology [2].  These terms apply to IPv4 and
   IPv6 traffic as well as IPv4 and IPv6 IGPs.

   An example of Route Convergence as observed and measured from the
   data plane is shown in Figure 1.  The graph in Figure 1 shows
   Forwarding Rate versus Time.  Time 0 on the X-axis is on the far
   right of the graph.  The components of the graph and metrics are
   defined in the Term Definitions section.

           	      IGP Data Plane Route Convergence

                           Convergence    Convergence
                           Recovery         Event
                           Instant         Instant      Time = 0sec
	Maximum		       ^	      ^		    ^
	Forwarding Rate--> ----\    Packet   /---------------
				\    Loss   /<----Convergence
	      Convergence------->\	   /  	  Event Transition
	Recovery Transition	  \	  /
				   \_____/<------Packet Loss

	X-axis = Time
	Y-axis = Forwarding Rate
			Figure 1. Convergence Graph

   2.  Existing definitions
   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", "June", and "OPTIONAL" in this
   document are to be interpreted as described in BCP 14, RFC 2119
   [Br97].  RFC 2119 defines the use of these key words to help make the
   intent of standards track documents as clear as possible.  While this
   document uses these keywords, this document is not a standards track
   document.

   3. Term Definitions
   3.1 Convergence Event

	Definition:
	The occurrence of a planned or unplanned action in the network
	that results in a change in the egress interface of the DUT for
	routed packets.

	Discussion:
	Convergence Events include link loss, routing protocol session
	loss, router failure, configuration change, and better next-hop
	learned via a routing protocol.

	Measurement Units:
	N/A

	Issues:
	None

	See Also:
	Convergence Packet Loss
	Convergence Event Instant
           	      IGP Data Plane Route Convergence

   3.2 Route Convergence

	Definition:
	Recovery from a Convergence Event indicated by the DUT
	forwarding rate equal to the offered load.

	Discussion:
	Route Convergence is the action of all components of the router
	being updated with the most recent route change(s) including the
	RIB and FIB, along with software and hardware tables. Route
	Convergence can be observed externally by the rerouting of data
	Traffic to a new egress interface.

	Measurement Units:
	N/A

	Issues:
	None

	See Also:
	Network Convergence
	Full Convergence
  	Convergence Event

   3.3 Network Convergence

	Definition:
	The completion of updating of all routing tables, including the
	FIB, in all routers throughout the network.

	Discussion:
	Network Convergence is bounded by the sum of Route Convergence
	for all routers in the network.  Network Convergence can be
	determined by recovery of the forwarding rate to equal the offered
	load, no Stale Forwarding, and no blenders[5][6].

	Measurement Units:
	N/A

	Issues:
	None

	See Also:
	Route Convergence
	Stale Forwarding
           	      IGP Data Plane Route Convergence

   3.4 Full Convergence
	Definition:
	Route Convergence for an entire FIB.

	Discussion:
	When benchmarking convergence it is useful to measure
	the time to converge an entire FIB.  For example,
	a Convergence Event can be produced for an OSPF table of
        5000 routes so that the time to converge routes 1 through
        5000 is measured.  Full Convergence is externally observable
        from the data plane when the forwarding rate on the Next-Best
        Egress Interface equals the offered load.

	Measurement Units:
	N/A

	Issues:
	None

	See Also:
	Network Convergence
	Route Convergence
  	Convergence Event

   3.5 Convergence Packet Loss

	Definition:
	The amount of packet loss produced by a Convergence Event
	until Route Convergence occurs.

	Discussion:
	Packet loss can be observed as a reduction of forwarded traffic from
	the maximum forwarding rate.  Convergence Packet Loss include packets
	that were lost and packets that were delayed due to buffering.
	Convergence Packet Loss may June or may June not reach 100%.

	Measurement Units:
	number of packets

	Issues:
	None

	See Also:
	Route Convergence
	Convergence Event
	Rate-Derived Convergence Time
	Loss-Derived Convergence Time
           	      IGP Data Plane Route Convergence

   3.6 Convergence Event Instant

	Definition:
	The time instant that a Convergence Event becomes observable in the
	data plane.

	Discussion:
	Convergence Event Instant is observable from the data
	plane as the precise time that the device under test begins
	to exhibit packet loss.

	Measurement Units:
	hh:mm:ss:uuu

	Issues:
	None

	See Also:
	Convergence Event
	Convergence Packet Loss
	Convergence Recovery Instant

   3.7 Convergence Recovery Instant

	Definition:
        The time instant that Full Convergence is measured
        and then maintained for an interval of duration equal to
        the Sustained Forwarding Convergence Time

	Discussion:
	Convergence Recovery Instant is measurable from the data
	plane as the precise time that the device under test
	achieves Full Convergence.

	Measurement Units:
	hh:mm:ss:uuu

	Issues:
	None

	See Also:
        Sustained Forwarding Convergence Time
        Convergence Packet Loss
        Convergence Event Instant
           	      IGP Data Plane Route Convergence

   3.8 Rate-Derived Convergence Time
	Definition:
	The amount of time for Convergence Packet Loss to persist upon
        occurrence of a Convergence Event until occurrence of Route
        Convergence.

        Rate-Derived Convergence Time can be measured as the time
	difference from the Convergence Event Instant to the
	Convergence Recovery Instant, as shown with Equation 1.

	(eq 1)	Rate-Derived Convergence Time =
		Convergence Recovery Instant - Convergence Event Instant.

	Discussion:
	Rate-Derived Convergence Time should be measured at the maximum
	forwarding rate.  Failure to achieve Full Convergence results in
	a Rate-Derived Convergence Time benchmark of infinity.

	Measurement Units:
	seconds/milliseconds

	Issues:
	None

	See Also:
	Convergence Packet Loss
	Convergence Recovery Instant
	Convergence Event Instant
	Full Convergence

   3.9 Convergence Event Transition
	Definition:
	The characteristic of a router in which forwarding rate
	gradually reduces to zero after a Convergence Event.

	Discussion:
	The Convergence Event Transition is best observed for
	Full Convergence.  The Convergence Event Transition may June
	not be linear.

	Measurement Units:
	seconds/milliseconds

	Issues:
	None

	See Also:
	Convergence Event
	Rate-Derived Convergence Time
	Convergence Packet Loss
	Convergence Recovery Transition
           	      IGP Data Plane Route Convergence

   3.10 Convergence Recovery Transition

	Definition:
	The characteristic of a router in which forwarding rate
	gradually increases to equal the offered load.

	Discussion:
	The Convergence Recovery Transition is best observed for
	Full Convergence.  The Convergence Event Transition may June
	not be linear.

	Measurement Units:
	seconds/milliseconds

	Issues:
	None

	See Also:
	Full Convergence
	Rate-Derived Convergence Time
	Convergence Packet Loss
	Convergence Event Transition

   3.11 Loss-Derived Convergence Time

	Definition:
	The amount of time it takes for Route Convergence to
	to be achieved as calculated from the Convergence Packet
	Loss.  Loss-Derived Convergence Time can be calculated
        from Convergence Packet Loss that occurs due to a
        Convergence Event and Route Convergence.as shown with
        Equation 2.

	(eq 2) Loss-Derived Convergence Time =
		Convergence Packets Loss / Offered Load
		NOTE: Units for this measurement are
		packets / packets/second = seconds

	Discussion:
	Loss-Derived Convergence Time gives a better than
	actual result when converging many routes simultaneously.
	Rate-Derived Convergence Time takes the Convergence Recovery
	Transition into account, but Loss-Derived Convergence Time
	ignores the Route Convergence Recovery Transition because
	it is obtained from the measured Convergence Packet Loss.
	Ideally, the Convergence Event Transition and Convergence
       Recovery Transition are instantaneous so that the
	Rate-Derived Convergence Time = Loss-Derived Convergence Time.
	However, router implementations are less than ideal.
	For these reasons the preferred reporting benchmark for IGP
	Route Convergence is the Rate-Derived Convergence Time.

           	      IGP Data Plane Route Convergence

	Guidelines for reporting Loss-Derived Convergence Time are
	provided in [2].

	Measurement Units:
	seconds/milliseconds

	Issues:
	None

	See Also:
	Route Convergence
	Convergence Packet Loss
	Rate-Derived Convergence Time
	Convergence Event Transition
	Convergence Recovery Transition

   3.12 Sustained Forwarding Convergence Time

	Definition:
	The amount of time for which Full Convergence is maintained without
        additional packet loss.

	Discussion:
	The purpose of the Sustained Forwarding Convergence Time is to produce
        Convergence Time benchmarks protected against fluctuation in Forwarding
        Rate after Full Convergence is observed.  The Sustained Forwarding
        Convergence Time to be used is calculated as shown in Equation 3.

        (eq 3)
        Sustained Forwarding Convergence Time =
        5 x (# routes in FIB) / (Offered Load)

        for which at least one packet per destination MUST be received at
        the DUT.

	Measurement Units:
        seconds or milliseconds

	Issues: None

	See Also:
	Full Convergence
        Convergence Recovery Instant

   3.13 Restoration Convergence Time

	Definition:
	The amount of time for the router under test to restore
	traffic to the original outbound port after recovery from
	a Convergence Event.

           	      IGP Data Plane Route Convergence

	Discussion:
	Restoration Convergence Time is the amount of time to
	Converge back to the original outbound port.  This is achieved
	by recovering from the Convergence Event, such as restoring
	the failed link.  Restoration Convergence Time is measured
	using the Rate-Derived Convergence Time calculation technique,
	as provided in Equation 1.  It is possible, but not desired
	to have the Restoration Convergence Time differ from the
	Rate-Derived Convergence Time.

	Measurement Units:
	seconds or milliseconds

	Issues:
	None

	See Also:
	Convergence Event
	Rate-Derived Convergence Time

   3.14 Packet Sampling Interval
	Definition:
	The interval at which the tester (test equipment) polls to make
	measurements for arriving packet flows.

	Discussion:
	Metrics measured at the Packet Sampling Interval may June include
	Forwarding Rate and Convergence Packet Loss.

	Measurement Units:
	seconds or milliseconds

	Issues:
	Packet Sampling Interval can influence the Convergence Graph.
	This is particularly true as implementations achieve Full
	Convergence in less than 1 second.  The Convergence Event
	Transition and Convergence Recovery Transition can become
	exaggerated when the Packet Sampling Interval is too long.
	This will produce a larger than actual Rate-Derived
	Convergence Time.  The recommended value for configuration
	of the Packet Sampling Interval is provided in [2].

	See Also:
	Convergence Packet Loss
	Convergence Event Transition
	Convergence Recovery Transition
           	      IGP Data Plane Route Convergence

   3.15 Local Interface
	Definition:
	An interface on the DUT.

	Discussion:
	None

	Measurement Units:
	N/A

	Issues:
	None

	See Also:
	Neighbor Interface
	 Remote Interface

   3.16 Neighbor Interface

	Definition:
	The interface on the neighbor router or tester that is
	directly linked to the DUT's Local Interface.

	Discussion:
	None

	Measurement Units:
	N/A

	Issues:
	None

	See Also:
	Local Interface
	Remote Interface

   3.17  Remote Interface

	Definition:
	An interface on a neighboring router that is not directly
	connected to any interface on the DUT.

	Discussion:
	None

	Measurement Units:
	N/A

	Issues:
	None
           	      IGP Data Plane Route Convergence

	See Also:
	Local Interface
	Neighbor Interface

   3.18 Preferred Egress Interface

	Definition:
	The outbound interface from the DUT for traffic routed to the
	preferred next-hop.

	Discussion:
	Preferred Egress Interface is the egress interface prior to
	a Convergence Event

	Measurement Units:
	N/A

	Issues:
	None

	See Also:
        Next-Best Egress Interface

   3.19 Next-Best Egress Interface

	Definition:
	The outbound interface from the DUT for traffic routed to the
	second-best next-hop.  It is the same media type and link speed
	as the Preferred Egress Interface

	Discussion:
	 Next-Best Egress Interface is the egress interface after
	a Convergence Event.

	Measurement Units:
	N/A

	Issues:
	None

	See Also:
	Preferred Egress Interface
           	      IGP Data Plane Route Convergence

  3.20 Stale Forwarding
	Definition:
	Forwarding of traffic to route entries that no longer exist
	or to route entries with next-hops that are no longer preferred.

	Discussion:
	Stale Forwarding can be caused by a Convergence Event and is
	also known as a "black-hole" since it may June produce packet loss.
	Stale Forwarding exists until Network Convergence is achieved.

	Measurement Units:
	N/A

	Issues:
	None

	See Also:
	Network Convergence

   3.21 Nested Convergence Events
	Definition:
        The occurence of Convergence Event while the route table
        is converging from a prior Convergence Event.

	Discussion:
	The Convergence Events for a Nested Convergence Events
        MUST occur with different neighbors.  A common
        observation from a Nested Convergence Event will be
        the withdrawal of routes from one neighbor while the
        routes of another neighbor are being installed.

	Measurement Units:
	N/A

	Issues:
	None

	See Also:
	Convergence Event

   4. Security Considerations

        Documents of this type do not directly affect the security of
        Internet or corporate networks as long as benchmarking
        is not performed on devices or systems connected to operating
        networks.

           	      IGP Data Plane Route Convergence

   5. Normative References

   [1]   Poretsky, S., "Benchmarking Applicability for IGP Data Plane
	 Route Convergence", draft-ietf-bmwg-igp-dataplane-conv-app-05,
	 work in progress, February 2005.

   [2]   Poretsky, S., "Benchmarking Methodology for IGP Data Plane
	 Route Convergence", draft-ietf-bmwg-igp-dataplane-conv-meth-05,
	 work in progress, February 2005.

   [3]   Callon, R., "Use of OSI IS-IS for Routing in TCP/IP and Dual
	 Environments", RFC 1195, December 1990.

   [4]   Moy, J., "OSPF Version 2", RFC 2328, IETF, April 1998.

   [5]   S. Casner, C. Alaettinoglu, and C. Kuan, "A Fine-Grained View
	 of High Performance Networking", NANOG 22, May June 2001.

   [6]   L. Ciavattone, A. Morton, and G. Ramachandran, "Standardized
	 Active Measurements on a Tier 1 IP Backbone", IEEE Communications
	 Magazine, pp90-97, June, 2003.

  6. Author's Address

     	Scott Poretsky
   	Quarry Technologies
  	8 New England Executive Park
   	Burlington, MA 01803
    	USA
    	Phone: + 1 781 395 5090
   	EMail: sporetsky@quarrytech.com

	Brent Imhoff
	USA
	EMail: bimhoff@planetspork.com

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           	      IGP Data Plane Route Convergence

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