Network Working Group
   INTERNET-DRAFT
   Expires in: December 2003 April 2004
                                                Scott Poretsky
                                                Avici Systems
                                                Quarry Technologies

								Brent Imhoff
								Wiltel Communications

                                       		June

                                       		October 2003

            	Benchmarking Methodology for
		    IGP Data Plane Route Convergence

	<draft-ietf-bmwg-igp-dataplane-conv-meth-00.txt>

	<draft-ietf-bmwg-igp-dataplane-conv-meth-01.txt>

   Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force  (IETF), its areas, and its working groups.  Note that
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   Drafts.

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   http://www.ietf.org/ietf/1id-abstracts.txt

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   Table of Contents
     1. Introduction ...............................................2
     2. Existing definitions .......................................2
     3. Test Setup..................................................2
     3.1 Test Topologies............................................2
     3.2 Test Considerations........................................3 Considerations........................................4
     3.2.1 IGP Selection............................................4
     3.2.2 BGP Configuration........................................4
     3.2.3 IGP Route Scaling........................................5
     3.2.4 Timers...................................................5
     3.2.5 Convergence Time Metrics.................................5
     3.2.6 Packet Sampling Interval.................................6
     3.2.7 Interface Type...........................................6
     3.3 Reporting Format...........................................6
           	      IGP Data Plane Route Convergence

     4. Test Cases..................................................4 Cases..................................................7
     4.1 Local Events...............................................4
     4.1.1 Convergence Due to SONET Link Failure....................4 Failure............................7
     4.1.1 Convergence Due to Local Interface Failure...............7
     4.1.2 Convergence Due to Neighbor Interface Failure............8
     4.1.3 Convergence Due to Remote Interface Failure..............8
     4.2 Convergence Due to PPP Session Failure...................5
     4.1.3 Failure.....................9
     4.3 Convergence Due to IGP Adjacency Failure.................5
     4.1.4 Failure...................10
     4.4 Convergence Due to Route Withdrawal......................6
     4.1.5 Withdrawal........................10
     4.5 Convergence Due to Cost Change...........................7
     4.2 Remote Events..............................................7
     4.2.1 Change.............................11
     4.6 Convergence Due to Remote SONET Link Failure.............7
           	      IGP Data Plane Route ECMP Member Interface Failure...........11
     4.7 Convergence Due to Parallel Link Interface Failure.........12
     5. Measuring Convergence Times.................................8
     5.1 Measuring Peak-to-Peak Convergence Time....................8
     5.2 Measuring Impact of Components for Convergence.............8
     6. Security Considerations.....................................9 Considerations.....................................13
     6. References..................................................13
     7. Acknowledgements............................................9
     8. References..................................................9
     9. Author's Address............................................9
     10. Address............................................13
     8. Full Copyright Statement...................................10 Statement....................................13

   1. Introduction
   This draft describes the methodology for benchmarking IGP Route
   Convergence.  The applicability of this testing is described in
   [1] and the new terminology that it introduces is defined in [2].
   Service Providers use IGP Convergence time as a key metric of
   router design and architecture.  Customers of Service Providers
   observe convergence time by packet loss. loss, so IGP Route Convergence
   is considered a Direct Measure of Quality (DMOQ) when benchmarking the data
   plane and not the control plane. (DMOQ).  The test cases
   in this document are black-box tests that emulate the network
   events that cause route convergence, as described in [1].  Black-box  The
   black-box test design
   accounts designs benchmark the data plane accounting for
   all of the factors for contributing to route convergence time, as
   provided
   discussed in [1].  The methodology and terminology is to be used (and terminology) for
   benchmarking route convergence and can be applied to any link-state
   IGP such as ISIS [3] and OSPF [4].

   2.  Existing definitions

   For the sake of clarity and continuity this RFC adopts the template
   for definitions set out in Section 2 of RFC 1242.  Definitions are
   indexed and grouped together in sections for ease of reference.

   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.

   3.  Test Setup
   3.1 Test Topologies

	---------    Ingress Traffic Path	---------
	|      	|<------------------------------|	|
	| 	|				|	|
	|  	|    Preferred Egress Path	|	|
	|  DUT  |------------------------------>|Tester	|
	| 	| 				|	|
	|      	|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~>|	|
	| 	|    Backup Egress Path		|	|
	---------				---------

	Figure 1.  IGP Route Convergence Test Topology
			for Local Changes
           	      IGP Data Plane Route Convergence

   Figure 1 shows the test topology to measure IGP Route Convergence due
   to local changes Convergence Events such as SONET Link Failure, PPP Session
   Failure, IGP  Adjacency Failure, Route Withdrawal, and Route route cost
   change.  These test cases are described discussed in section 4.1.  These test cases 4 provide
   IGP Route Convergence route
   convergence times that consider account for the Event Detection time, SPF
           	      IGP Data Plane Route Convergence

   Processing time, and FIB Update time.  These times are measured
   by observing packet loss in the data plane.  Physical Links may be of
   any type, such as Sonet or Ethernet, and any speed.

	--------- 	Ingress Interface		    ---------
	|       |<------------------------------|		|
	| 	  |					    |		|
	|  	  | Preferred Egress Interface    |		|
	|  DUT  |------------------------------>|Tester	|
	| 	  | 					    |		|
	|       |~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~>|		|
	| 	  | Next-Best Egress Interface    |		|
	---------					    ---------

	Figure 1.  IGP Route Convergence Test Topology for Local Changes

   Figure 2 shows the test topology to measure IGP Route Convergence
   time due to remote changes in the network topology.  These times are
   measured by observing packet loss in the data plane.  Physical Links
   may be of any type, such as Sonet or Ethernet, and any speed.  In this
   topology,
   topology the three routers are considered a System Under Test (SUT).
   Application of this topology and test cases described in section 4.2
   account for the impact of IGP Advertisement on Route Convergence, as
   described in [1].

		  -----              		-----------
		  |   |	Preferred   	|         |
	-----	  |R2 |------------->| |---------------------->|	    |
	|   |---->|   |-->|   | Egress Path Interface  	|	    |
	|   |	  -----		     		|	    |
	|R1 |			     			|  Tester |
	|   |	  -----		     		|	    |
	|   |---->|   |-->|   |	  Backup	Next-Best     	|	    |
	-----	  |R3 |~~~~~~~~~~~~~>| |~~~~~~~~~~~~~~~~~~~~~~>|	    |
	  ^	  |   |	Egress Path Interface  |	    |
	  |	  -----		     		-----------
	  |				                |
	  |--------------------------------
	  |--------------------------------------
		Ingress Traffic Path Interface

	Figure 2.  IGP Route Convergence Test Topology
			for Remote Changes

   Figure 3 shows the test topology to measure IGP Route Convergence
   time with members of an ECMP Set.  These times are measured by
   observing packet loss in the data plane.  In this topology, the DUT
   is configured with each Egress interface as a member of an ECMP set
   and the Tester emulates multiple next-hop routers (emulates one
   router for each member).

           	      IGP Data Plane Route Convergence

	--------- 		Ingress Interface		---------
	|       |<--------------------------------|	  |
	| 	  |						|	  |
	|  	  |	ECMP Set Interface 1		|	  |
	|  DUT  |-------------------------------->| Tester|
	|	  |		.				|	  |
	|	  |		.				|	  |
	| 	  | 		.				|	  |
	|       |~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~>|	  |
	| 	  |	ECMP Set Interface N		|	  |
	---------						---------

	Figure 3.  IGP Route Convergence Test Topology
			for ECMP Convergence

   Figure 4 shows the test topology to measure IGP Route Convergence
   time with members of a Parallel Link.  These times are measured by
   observing packet loss in the data plane.  In this topology, the DUT
   is configured with each Egress interface as a member of a Parallel
   Link and the Tester emulates the single next-hop router.

	--------- 		Ingress Interface		---------
	|       |<--------------------------------|	  |
	| 	  |						|	  |
	|  	  |	Parallel Link Interface 1	|	  |
	|  DUT  |-------------------------------->| Tester|
	|	  |		.				|	  |
	|	  |		.				|	  |
	| 	  | 		.				|	  |
	|       |~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~>|	  |
	| 	  |	Parallel Link Interface N	|	  |
	---------						---------

	Figure 4.  IGP Route Convergence Test Topology
		      for Parallel Link Convergence

   3.2 Test Considerations

   3.2.1 IGP Selection
   The test cases described in section 4 can be used for ISIS or
   OSPF.  The Route Convergence test methodology for both is
   identical.  The IGP adjacencies are established on the Preferred
   Egress Path Interface and Backup Next-Best Egress Path. Interface.

   3.2.2 BGP Configuration
   The obtained results for IGP Route Convergence may vary if
   BGP routes are installed.  For results similar to those that
   would be observed in an operational network it  It is recommended that a BGP session be established on the Ingress Traffic Path
   with IGP
   Convergence times be benchmarked without BGP routes installed.

           	      IGP Data Plane Route Convergence

   3.2.3 IGP Route Scaling
   The number of IGP routes will impact the measured IGP Route
   Convergence because convergence for the entire IGP route table is
   measured.   For results similar to those that would be observed in
   an operational network it is recommended that the number of
   installed routes closely approximate that for routers in the
   network.

   3.2.4 BGP Route Scaling
   The number of installed BGP routes may Timers
   There are some timers that will impact the IGP Convergence
   time.  For results similar to those that would be observed in an
   operational Network it is recommended that the number of installed
   routes closely approximate that for routers in the network.

   3.2.5 Timers
   There are some timers that will impact the measured measured IGP Convergence
   time. The following timers should be configured to the minimum value
   prior to beginning execution of the test cases:

	Timer						Recommended Value
	-----						-----------------
   	SONET Failure Indication Delay	<10milliseconds
   	IGP Hello Timer				1 second
   	IGP Dead-Interval				3 seconds
   	LSA Generation Delay			0
   	LSA Flood Packet Pacing			0
   	LSA Retransmission Packet Pacing	0
   	SPF Delay

   4. Test Cases
   4.1 Local Events					0

   3.2.5 Convergence Time Metrics
   Figure 5 shows a graph model of Convergence Time as measured
   from the data plane.  Refer to [2] for definitions of the terms
   used. Rate-Derived Convergence Time and Loss-Derived Convergence
   Time are the two metrics for convergence time. An offered Load of
   maximum forwarding rate at a fixed packet size is recommended for
   accurate measurement.  The test cases duration must be greater than the
   convergence time.

   Ideally, Convergence Event Transition and Convergence Recovery
   Transition are instantaneous so that the
   Rate-Derived Convergence Time = Loss-Derived Convergence Time.

   When the Convergence Event Transition and Convergence Recovery
   Transition are not instantaneous so that there is a slope, as
   shown in Figure 5, the accuracy of the Rate-Derived Convergence
   Time and Loss-Derived Convergence Time are dependent upon the
   Packet Sampling Interval.

   Under this section use condition and the Packet Sampling Interval <= 100
   millisecond, the Rate-Derived Convergence Time > Loss-Derived
   Convergence Time and Rate-Derived Convergence Time is the preferred
   metric.  Under this condition and the Packet Sampling Interval > 100
   millisecond the Rate-Derived Convergence Time < Loss-Derived
   Convergence Time and Loss-Derived Convergence Time is the better
   metric.  For all test topology shown in cases, the Rate-Derived Convergence Time
   and Loss-Derived Convergence Time must be recorded.

           	      IGP Data Plane Route Convergence

		            Recovery  Convergence Event   Time = 0sec
	Maximum		     ^		 ^		    ^
	Forwarding Rate--> ----\    Packet   /---------------
					\    Loss   /<----Convergence
	      Convergence------->\	     /  	  Event Transition
	Recovery Transition	  \	    /
				   	   \_____/<------100% Packet Loss

	X-axis = Time
	Y-axis = Forwarding Rate

			Figure 1.

   4.1.1 5. Convergence Graph

   3.2.6 Packet Sampling Interval
   Selection of the Packet Sampling Interval on the Test Equipment
   impacts the measured Rate-Derived Convergence Time.  Packet
   Sampling Interval time is that is too large exaggerates the
   slope of the Convergence Event Transition and Convergence
   Recovery Transition producing a larger than the actual Rate-Derived
   Convergence Time.  This impact is greater as routers achieve
   millisecond convergence times.  The recommended value for the
   Packet Sampling Interval is 100 millisecond.  It is possible to
   have commercially available test equipment with a minimum
   configurable Packet Sampling Interval of 1 second.

   3.2.7 Interface Types
   All test cases in this methodology document may be executed with
   any interface type.  SONET is recommended and specifically
   mentioned in the procedures because it can be configured to have
   no or negligible affect on the measured convergence time.
   Ethernet (10Mb, 100Mb, 1Gb, and 10Gb) is not preferred since
   broadcast media are unable to detect loss of host and rely upon
   IGP Hellos to detect session loss.

   3.3 Reporting Format
   For each test case, it is recommended that the following reporting
   format be completed:

           	      IGP Data Plane Route Convergence

	Parameter						Units
	---------						-----
   	IGP							(ISIS or OSPF)
   	Interface Type					(GigE, POS, ATM, etc.)
   	Packet Size						bytes
   	IGP Routes 						number of IGP routes
   	Packet Sampling Interval			seconds or milliseconds
   	IGP Timer Values
		SONET Failure Indication Delay	seconds or milliseconds
   		IGP Hello Timer				seconds or milliseconds
   		IGP Dead-Interval				seconds or milliseconds
   		LSA Generation Delay			seconds or milliseconds
   		LSA Flood Packet Pacing			seconds or milliseconds
   		LSA Retransmission Packet Pacing	seconds or milliseconds
   		SPF Delay					seconds or milliseconds
      Results
		Rate-Derived Convergence Time		seconds or milliseconds
		Loss-Derived Convergence Time		seconds or milliseconds
		Restoration Convergence Time		seconds or milliseconds

   4. Test Cases
   4.1 Convergence Due to Link Failure
   4.1.1 Convergence Due to Local Interface Failure
	Objective
	To obtain the IGP Route Convergence due to a local link
	failure event at the DUT's Local Interface.

	Procedure
	1. Advertise matching IGP routes from Tester to DUT on
         Preferred Egress Interface [2] and Next-Best Egress Interface
	   [2] using the topology shown in Figure 1.  Set the cost of the
	   routes so that the Preferred Egress Interface is the preferred
   next-hop.
	2. Send traffic at maximum forwarding rate to destinations
         matching all IGP routes from Tester to DUT on Ingress Interface
	   [2].
	3. Verify traffic routed over Preferred Egress Interface.
	4. Remove SONET on DUT's Local Interface [2] by performing an
	   administrative shutdown of the interface.
	5. Measure Rate-Derived Convergence Time [2] and Loss-Derived
	   Convergence Time [2] as DUT detects the link down event and
	   converges all IGP routes and traffic over the Next-Best Egress
 	   Interface.
	6. Restore SONET on DUT's Local Interface by administratively
	   enabling the interface.
	7. Measure Restoration Convergence Time [2] as DUT detects the link
	   up event and converges all IGP routes and traffic back to the
	   Preferred Egress Interface.

	Results
	The measured IGP Convergence time is influenced by the Local
	SONET indication, SPF delay, SPF Holdtime, SPF Execution
	Time, Tree Build Time, and Hardware Update Time.

           	      IGP Data Plane Route Convergence
   4.1.2 Convergence Due to Neighbor Interface Failure
	Objective
	To obtain the IGP Route Convergence due to a local link
	failure event at the Tester's Neighbor Interface.

	Procedure
	1. Advertise matching IGP routes from Tester to DUT on
         Preferred Egress Interface [2] and Next-Best Egress Interface
	   [2] using the topology shown in Figure 1.  Set the cost of
	   the routes so that the Preferred Egress Interface is the
   preferred next-hop.
	2. Send traffic at maximum forwarding rate to destinations
         matching all IGP routes from Tester to DUT on Ingress
	   Interface [2].
	3. Verify traffic routed over Preferred Egress Interface.
	4. Remove SONET on Tester's Neighbor Interface [2] connected to
   	   DUT' s Preferred Egress Interface.
	5. Measure Rate-Derived Convergence Time [2] and Loss-Derived
	   Convergence Time [2] as DUT detects the link down event and
	   converges all IGP routes and traffic over the Next-Best
	   Egress Interface.
	6. Restore SONET on Tester's Neighbor Interface connected to
   	   DUT's Preferred Egress Interface.
	7. Measure Restoration Convergence Time [2] as DUT detects the
	   link up event and converges all IGP routes and traffic back to
	   the Preferred Egress Interface.

	Results
	The measured IGP Convergence time is influenced by the Local
	SONET indication, SPF delay, SPF Holdtime, SPF Execution
	Time, Tree Build Time, and Hardware Update Time.

   4.1.3 Convergence Due to Local SONET Link Remote Interface Failure

      Objective
	To obtain the IGP Route Convergence due to a Local SONET Link Remote
	Interface failure event.

	Procedure
	1. Advertise IGP routes from Tester to DUT on Ingress Traffic
         Path.
	2. Advertise matching IGP routes from Tester to DUT SUT on
         Preferred Egress Path Interface [2] and Backup Next-Best Egress Path. Interface
	   [2] using the topology shown in Figure 2.  Set the cost of the
	   routes so that the IGP routes along the Preferred Egress Path Interface is the preferred
   next-hop.
3.  NOTE: All routers in the SUT must be the same model
   and identically configured.
	2. Send traffic at maximum forwarding rate to destinations
         matching all IGP routes from Tester to DUT on Ingress Traffic
         Path.
	4. Interface
	   [2].
	3. Verify traffic is routed over Preferred Egress Path.
	5. Interface.
	4. Remove SONET on Tester Tester's Neighbor Interface [2] connected to
   	   SUT' s Preferred Egress
	   Path.
	6. Interface.

           	      IGP Data Plane Route Convergence

	5. Measure Peak-to-Peak Rate-Derived Convergence Time [2] and Loss-Derived
	   Convergence Time [2] as DUT SUT detects the link down event and
	   converges all IGP routes and traffic over the Backup Next-Best
	   Egress Path.

           	      IGP Data Plane Route Interface.
	6. Restore SONET on Tester's Neighbor Interface connected to
   	   SUT's Preferred Egress Interface.
	7. Measure Restoration Convergence Time [2] as SUT detects the
	   link up event and converges all IGP routes and traffic over
	   the Preferred Egress Interface.

	Results
	The measured IGP Convergence time is influenced by the Local
	SONET failure indication, LSA/LSP Flood Packet Pacing,
	LSA/LSP Retransmission Packet Pacing, LSA/LSP Generation
	time, SPF delay, SPF Holdtime, SPF Execution Time, Tree
	Build Time, and Hardware Update Time.  The additional
	convergence time contributed by LSP Propagation can be
	obtained by subtracting the Rate-Derived Convergence Time
	measured in 4.1.2 (Convergence Due to Neighbor Interface
	Failure) from the Rate-Derived Convergence Time measured in
	this test case.

   4.2 Convergence Due to PPP Session Failure
	Objective
	To obtain the IGP Route Convergence due to a Local PPP Session
	failure event.

	Procedure
	1. Advertise IGP routes from Tester to DUT on Ingress Traffic
   	   Path.
	2. Advertise matching IGP routes from Tester to DUT on
           Preferred Egress Path Interface [2] and Backup Next-Best Egress Path. Interface
	   [2] using the topology shown in Figure 1.  Set the cost of
	   the routes so that the IGP routes along the Preferred Egress Path
	   Interface is the preferred next-hop.
	3.
	2. Send traffic at maximum forwarding rate to destinations
	   matching all IGP routes from Tester to DUT on Ingress
	   Traffic Path.
	4.
	   Interface [2].
	3. Verify traffic routed over Preferred Egress Path.
	5. Interface.
	4. Remove PPP session from Tester Tester's Neighbor Interface [2]
	   connected to Preferred Egress Path.
	6. Interface.
	5. Measure Peak-to-Peak Rate-Derived Convergence Time [2] and Loss-Derived
	   Convergence Time [2] as DUT detects the PPP session down event
	   and converges all IGP routes and traffic over the Backup Next-Best
	   Egress Path. Interface.
	6. Restore PPP session on DUT's Preferred Egress Interface.
	7. Measure Restoration Convergence Time [2] as DUT detects the
	   session up event and converges all IGP routes and traffic over
	   the Preferred Egress Interface.

	Results
	The measured IGP Convergence time is influenced by the Local PPP
      failure indication, SPF delay, SPF Holdtime, SPF Execution
      Time, Tree Build Time, and Hardware Update Time.

   4.1.3

           	      IGP Data Plane Route Convergence

   4.3 Convergence Due to IGP Adjacency Failure

	Objective
	To obtain the IGP Route Convergence due to a Local IGP Adjacency
	failure event.

	Procedure
	1. Advertise IGP routes from Tester to DUT on Ingress Traffic
         Path.
	2. Advertise matching IGP routes from Tester to DUT on
         Preferred Egress Path Interface [2] and Backup Next-Best Egress Path. Interface
	   [2] using the topology shown in Figure 1.  Set the cost of
	   the routes so that the IGP routes along the Preferred Egress Path Interface is the
	   preferred next-hop.
	3.
	2. Send traffic at maximum forwarding rate to destinations
	   matching all IGP routes from Tester to DUT on Ingress
	   Traffic Path.
	4.
	   Interface [2].
	3. Verify traffic routed over Preferred Egress Path.
	5. Interface.
	4. Remove IGP adjacency from Tester interface Tester's Neighbor Interface [2]
	   connected to Preferred Egress Path.

           	      IGP Data Plane Route Convergence

	6. Interface.
	5. Measure Peak-to-Peak Rate-Derived Convergence Time [2] and Loss-Derived
	   Convergence Time [2] as DUT detects the IGP session failure
	   event and converges all IGP routes and traffic over the Backup
	   Next-Best Egress Interface.
	6. Restore IGP session on DUT's Preferred Egress Interface.
	7. Measure Restoration Convergence Time [2] as DUT detects the
	   session up event and converges all IGP routes and traffic over
	   the Preferred Egress Path. Interface.

	Results
	The measured IGP Convergence time is influenced by the IGP
	Hello Interval, IGP Dead Interval, SPF delay, SPF Holdtime,
	SPF Execution Time, Tree Build Time, and Hardware Update
	Time.

   4.1.4

  4.4 Convergence Due to Route Withdrawal

	Objective
	To obtain the IGP Route Convergence due to Route Withdrawal.

	Procedure
	1. Advertise IGP routes from Tester to DUT on Ingress Traffic
         Path.
	2. Advertise matching IGP routes from Tester to DUT on
         Preferred Egress Path Interface [2] and Backup Next-Best Egress Path. Interface
	   [2] using the topology shown in Figure 1.  Set the cost of
	   the routes so that the IGP routes along the Preferred Egress Path Interface is the
	   preferred next-hop.
	3.
	2. Send traffic at maximum forwarding rate to destinations
	   matching all IGP routes from Tester to DUT on Ingress
	   Traffic Path.
	4.
	   Interface [2].
	3. Verify traffic routed over Preferred Egress Path.
	5. Interface.
	4. Tester withdraws all IGP routes from DUT's Local Interface
	   on Preferred Egress Path.
	6. Interface.

           	      IGP Data Plane Route Convergence

	5. Measure Peak-to-Peak Rate-Derived Convergence Time [2] and Loss-Derived
	   Convergence Time [2] as DUT processes the route withdrawal
	   event and converges all IGP routes and traffic over the Backup
	   Next-Best Egress Interface.
	6. Re-advertise IGP routes to DUT's Preferred Egress Interface.
	7. Measure Restoration Convergence Time [2] as DUT converges all
	   IGP routes and traffic over the Preferred Egress Path. Interface.

	Results
	The measured IGP Convergence time is the SPF Processing and FIB
	Update time as influenced by the SPF delay, SPF Holdtime,
	SPF Execution Time, Tree Build Time, and Hardware Update Time.

   4.1.5

   4.5 Convergence Due to Cost Change

	Objective
	To obtain the IGP Route Convergence due to route cost change.

	Procedure
	1. Advertise IGP routes from Tester to DUT on Ingress Traffic
         Path.
	2. Advertise matching IGP routes from Tester to DUT on
         Preferred Egress Path Interface [2] and Backup Next-Best Egress Path. Interface
	   [2] using the topology shown in Figure 1.  Set the cost of
	   the routes so that the IGP routes along the Preferred Egress Path Interface is the
   preferred next-hop.
	3.
	2. Send traffic at maximum forwarding rate to destinations
	   matching all IGP routes from Tester to DUT on Ingress
	   Traffic Path.

           	      IGP Data Plane Route Convergence

	4.
	   Interface [2].
	3. Verify traffic routed over Preferred Egress Path.
	5. Interface.
	4. Tester increases cost for all IGP routes at DUT's Local
	   Interface on Preferred
	   Egress Path Interface so that Backup the Next-Best Egress
	   Path have Inerface
	   has lower cost and becomes preferred path.
	6.
	5. Measure Reroute Rate-Derived Convergence Time [2] and Loss-Derived
	   Convergence Time [2] as DUT detects the cost change event
	   and converges all IGP routes and traffic over the Backup Next-Best
	   Egress Path.

	Results
	The measured Interface.
	6. Re-advertise IGP routes to DUT's Preferred Egress Interface
	   with original lower cost metric.
	7. Measure Restoration Convergence time is the SPF Processing and FIB
	Update time Time [2] as influenced by the SPF delay, SPF Holdtime,
	SPF Execution Time, Tree Build Time, DUT converges all
	   IGP routes and Hardware Update Time. traffic over the Preferred Egress Interface.

	Results
	There should be no measured packet loss for this case.

   4.2 Remote Events

   The test cases in this section use the test topology shown in
   Figure 2.

   4.2.1

    4.6 Convergence Due to Remote SONET Link ECMP Member Interface Failure

	Objective
	To obtain the IGP Route Convergence due to a Remote
	SONET Link local link
	failure event. event of an ECMP Member.

           	      IGP Data Plane Route Convergence

	Procedure
	1. Advertise IGP routes from Tester to DUT on Ingress Traffic
         Path. Configure ECMP Set as shown in Figure 3.
	2. Advertise matching IGP routes from Tester to DUT on
         Preferred Egress Path and Backup Egress Path.  Set the cost
         of the routes so that the IGP routes along the Preferred
         Egress Path is the preferred next-hop.
           each ECMP member.
	3. Send traffic at maximum forwarding rate to destinations
           matching all IGP routes from Tester to DUT on Ingress
	   Traffic Path.
	   Interface [2].
	4. Verify traffic routed over Preferred Egress Path. all members of ECMP Set.
	5. Remove SONET on Tester's Neighbor Interface [2] connected to
	   Preferred Egress Path.
   	   one of the DUT's ECMP member interfaces.
	6. Measure Peak-to-Peak Rate-Derived Convergence time Time [2] and Loss-Derived
	   Convergence Time [2] as DUT detects the link down event and
	   converges all IGP routes and traffic over the Backup Egress Path. other ECMP
	   members.
	7. Restore SONET on Tester's Neighbor Interface connected to
   	   DUT's ECMP member interface.
	8. Measure Restoration Convergence Time [2] as DUT detects the
	   link up event and converges IGP routes and some distribution
	   of traffic over the restored ECMP member.

	Results
	The measured IGP Convergence time is influenced by the Local
	SONET failure indication, LSA/LSP Flood Packet Pacing,
	LSA/LSP Retransmission Packet Pacing, LSA/LSP Generation
	time, SPF delay, SPF Holdtime, SPF Execution Time, Tree Build Time, and Hardware Update Time.

           	      IGP Data Plane Route Convergence

   5. Measuring Convergence Times
   5.1 Measuring Full Convergence Time

	Figure 3 shows a graph model of

   4.7 Convergence Time as measured
	from the data plane.  Refer Due to [2] for definitions of Parallel Link Interface Failure
	Objective
	To obtain the terms
	used. IGP Route Convergence Time is the amount of time for the
	Forwarding Rate due to begin its downward slope upon occurrence of a network local link
	failure event and then fully recover to the Maximum
	Forwarding Rate.

			Forwarding Rate versus Time

		   Time=Recovery    Time=Network Event	Time = 0sec
	Maximum		      ^		     ^		^
	Forwarding Rate--> ----\             /-----------
				\           /<----Route Convergence
	Route Convergence------->\	   /  	  Event Slope
	Recovery Slope		  \_______/<------100% Packet Loss

	X-axis = Time
	Y-axis = Forwarding Rate

			Figure 3. Convergence Graph

	Maximum forwarding rate at a fixed packet size without packet
	loss is required for accurate measurement.  The test duration
	must be greater than the convergence time. Full Convergence
	Time is obtained directly a Member of a Parallel Link.

	Procedure
	1. Configure Parallel Link as shown in Figure 4.
	2. Advertise matching IGP routes from the graph in Figure 3 using
	equation 1.

	(eq 1) Convergence Time(Full)=Time(Recovery)-Time(Network Event).

	Given a known constant Tester to DUT on
         each Parallel Link member.
	3. Send traffic at maximum forwarding rate to destinations
         matching all IGP routes from Tester to DUT on Ingress
	   Interface [2].
	4. Verify traffic routed over all members of Parallel Link.
	5. Remove SONET on Tester's Neighbor Interface [2] connected to
   	   one of offered load in units packet per
	second (pps), the Average Convergence Time can be obtained
	using equation 2 or equation 3.

      (eq 2) Convergence Time(Average)=Number Packets Lost/pps(Offered)

	(eq 3) Convergence Time(Average)= (Number Packets Offered -
		Number of Packets Received)/pps(Offered)

	As discussed in [1], Full DUT's Parallel Link member interfaces.
	6. Measure Rate-Derived Convergence Time is the more accurate
	measurement.  Average [2] and Loss-Derived
	   Convergence Time does not account for [2] as DUT detects the
	angle of link down event and
	   converges all IGP routes and traffic over the Route Convergence Recovery Slope, so Full other
	   Parallel Link members.
	7. Restore SONET on Tester's Neighbor Interface connected to
   	   DUT's Parallel Link member interface.
	8. Measure Restoration Convergence Time > Average Convergence Time.  Ideally, [2] as DUT detects the Recovery Slope has
	no angle so that it is vertical
	   link up event and Average Convergence Time =
	Full Convergence Time.

   5.2 Measuring Impact converges IGP routes and some distribution
	   of Components for Convergence traffic over the restored Parallel Link member.

	Results
	The factors for measured IGP Route Convergence Time are provided in [1].
	The results of the test cases in section 4 above can be used to
	calculate the impact each factor has on time is influenced by the Convergence Local
	SONET indication, Tree Build Time, and Hardware Update Time.

           	      IGP Data Plane Route Convergence

	results, as follow:

	SPF Processing and FIB Update time = Result (4.1.4)

	SONET failure indication time = Result(4.1.1) - Result(4.1.4)

	PPP failure indication time = Result(4.1.2) - Result(4.1.4)

	IGP failure indication time = Result(4.1.3) - Result(4.1.4)

	IGP Advertisement time = Result(4.1.1) - Result(4.2.1)

   6.

  5. Security Considerations

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

   7. Acknowledgements
	Thanks to Jayant Kulkarni for doing as most Test Engineers
	do - working beyond the call of duty to help advance
	technology.  Especially thanks to the many Network Engineers
	and Network Architects at the Service Providers who are always
	eager to discuss Route Convergence.

   8.

   6. References

      [1] Poretsky, S., "Benchmarking Applicability for IGP
	    Convergence", draft-ietf-bmwg-igp-dataplane-conv-app-00, draft-ietf-bmwg-igp-dataplane-conv-app-01, work
	    in progress, June October 2003.

	[2] Poretsky, S., Imhoff, B., "Benchmarking Terminology for IGP         	    Convergence",
	    draft-ietf-bmwg-igp-dataplane-conv-term-00, draft-ietf-bmwg-igp-dataplane-conv-term-01, work
	    in progress,
	    June October 2003.

      [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.

   9.

   7. Author's Address

     	Scott Poretsky
   	Avici Systems, Inc.
  	101 Billerica Avenue
   	N. Billerica,
   	Quarry Technologies
  	8 New England Executive Park
   	Burlington, MA 01862 01803
    	USA

    	Phone: + 1 978 964 2287 781 395 5090
   	EMail: sporetsky@avici.com
           	      IGP Data Plane Route Convergence sporetsky@quarrytech.com

	Brent Imhoff
	WilTel Communications
	3180 Rider Trail South
	Bridgeton, MO 63045
	USA

	Phone: +1 314 595 6853
	EMail: brent.imhoff@wcg.com

   10.

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           	      IGP Data Plane Route Convergence

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