INTERNET-DRAFT =20
Expires in: September 2006 =20
Scott Poretsky
Reef Point Systems
Brent Imhoff
Juniper Networks
March 2006
Terminology for Benchmarking=20
IGP Data Plane Route Convergence
Intellectual Property Rights (IPR) statement:
By submitting this Internet-Draft, each author represents that any=20
applicable patent or other IPR claims of which he or she is aware=20
have been or will be disclosed, and any of which he or she becomes=20
aware will be disclosed, in accordance with Section 6 of BCP 79.
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Copyright Notice
Copyright (C) The Internet Society (2006). =20
ABSTRACT
This document describes the terminology for benchmarking IGP=20
Route Convergence as described in Applicability document [1] and=20
Methodology document [2]. The methodology and terminology are to=20
be used for benchmarking Convergence Time and can be applied to=20
any link-state IGP such as ISIS [3] and OSPF [4]. The data plane=20
is measured to obtain the convergence benchmarking metrics=20
described in [2].
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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 =
=20
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. IANA =
Considerations...........................................13
5. Security =
Considerations.......................................14
6. =
Acknowledgements..............................................14
7. Normative =
References..........................................14
8. Author's =
Address..............................................14
1. Introduction
This draft describes the terminology for benchmarking IGP Route=20
Convergence. The motivation and applicability for this=20
benchmarking is provided in [1]. The methodology to be used for=20
this benchmarking is described in [2]. The methodology and=20
terminology to be used for benchmarking Route Convergence can be=20
applied to any link-state IGP such as ISIS [3] and OSPF [4]. The=20
data plane is measured to obtain black-box (externally observable)
convergence benchmarking metrics. The purpose of this document is=20
to introduce new terms required to complete execution of the IGP=20
Route Convergence Methodology [2]. These terms apply to IPv4 and=20
IPv6 traffic as well as IPv4 and IPv6 IGPs.
An example of Route Convergence as observed and measured from the=20
data plane is shown in Figure 1. The graph in Figure 1 shows=20
Throughput versus Time. Time 0 on the X-axis is on the far=20
right of the graph. The components of the graph and metrics are=20
defined in the Term Definitions section. =20
=20
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IGP Data Plane Route Convergence
Convergence Convergence=20
Recovery Event =20
Instant Instant Time = 0sec =
=20
Maximum ^ ^ ^
Throughput--> ------\ Packet /---------------
\ Loss /<----Convergence
Convergence------->\ / Event Transition =
=20
Recovery Transition \ /
\_____/<------Maximum Packet Loss =
=20
=
=20
X-axis = Time
Y-axis = Throughput =20
Figure 1. Convergence Graph
2. Existing definitions
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 BCP 14, RFC 2119. =20
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. The term Throughput is defined in RFC 2544.
3. Term Definitions
3.1 Convergence Event
=20
Definition:
The occurrence of a planned or unplanned action in the network=20
that results in a change in the egress interface of the Device
Under Test (DUT) for=20
routed packets.
Discussion:
Convergence Events include link loss, routing protocol session=20
loss, router failure, configuration change, and better next-hop
learned via a routing protocol.
Measurement Units:
N/A
Issues: =20
None
See Also:
Convergence Packet Loss
Convergence Event Instant
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IGP Data Plane Route Convergence
3.2 Route Convergence
Definition:
Recovery from a Convergence Event indicated by the DUT=20
Throughput 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=20
Routing Information Base (RIB) and Forwaridng Information Base=20
(FIB), along with software and hardware tables. Route=20
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 =20
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=20
for all routers in the network. Network Convergence can be=20
determined by recovery of the Throughput to equal the=20
offered load, with no Stale Forwarding, and no blenders[5][6].
Measurement Units:
N/A
Issues:
None
See Also:
Route Convergence
Stale Forwarding
=20
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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=20
5000 routes so that the time to converge routes 1 through=20
5000 is measured. Full Convergence is externally observable=20
from the data plane when the Throughput of the data=20
plane traffic on the Next-Best Egress Interface equals the=20
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 Throughput. Convergence Packet Loss=20
includes packets that were lost and packets that were delayed=20
due to buffering. The maximum Convergence Packet Loss observed
in a Packet Sampling Interval may or may not reach 100% during=20
Route Convergence (see Figure 1).
Measurement Units:
number of packets
Issues: None
See Also:
Route Convergence
Convergence Event
Rate-Derived Convergence Time
Loss-Derived Convergence Time
Packet Sampling Interval
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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=20
plane as the precise time that the device under test begins=20
to exhibit packet loss. =20
Measurement Units:
hh:mm:ss:nnn, where 'nnn' is milliseconds
Issues: =20
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=20
the Sustained Forwarding Convergence Time
Discussion:
Convergence Recovery Instant is measurable from the data=20
plane as the precise time that the device under test=20
achieves Full Convergence. =20
Measurement Units:
hh:mm:ss:uuu
Issues: =20
None
See Also:
Sustained Forwarding Convergence Time
Convergence Packet Loss
Convergence Event Instant
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3.8 Rate-Derived Convergence Time
Definition:
The amount of time for Convergence Packet Loss to persist upon=20
occurrence of a Convergence Event until occurrence of Route=20
Convergence. =20
Rate-Derived Convergence Time can be measured as the time=20
difference from the Convergence Event Instant to the=20
Convergence Recovery Instant, as shown with Equation 1.
=20
(eq 1) Rate-Derived Convergence Time ==20
Convergence Recovery Instant - Convergence Event Instant. =
=20
Discussion:
Rate-Derived Convergence Time should be measured at the maximum
Throughput. Failure to achieve Full Convergence results in=20
a Rate-Derived Convergence Time benchmark of infinity.
Measurement Units:
seconds/milliseconds
Issues: =20
None
See Also:
Convergence Packet Loss
Convergence Recovery Instant
Convergence Event Instant
Full Convergence =20
3.9 Convergence Event Transition
Definition:
The characteristic of a router in which Throughput
gradually reduces to zero after a Convergence Event.
Discussion:
The Convergence Event Transition is best observed for=20
Full Convergence. The Convergence Event Transition may
not be linear.
Measurement Units:
seconds/milliseconds
Issues:
None
See Also:
Convergence Event
Rate-Derived Convergence Time
Convergence Packet Loss
Convergence Recovery Transition
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3.10 Convergence Recovery Transition
Definition:
The characteristic of a router in which Throughput
gradually increases to equal the offered load.
Discussion:
The Convergence Recovery Transition is best observed for=20
Full Convergence. The Convergence Event Transition may
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=20
to be achieved as calculated from the Convergence Packet=20
Loss. Loss-Derived Convergence Time can be calculated=20
from Convergence Packet Loss that occurs due to a=20
Convergence Event and Route Convergence as shown with=20
Equation 2. =20
(eq 2) Loss-Derived Convergence Time =
Convergence Packets Loss / Offered Load
NOTE: Units for this measurement are=20
packets / packets/second = seconds
Discussion:
Loss-Derived Convergence Time gives a better than=20
actual result when converging many routes simultaneously. =20
Rate-Derived Convergence Time takes the Convergence Recovery=20
Transition into account, but Loss-Derived Convergence Time=20
ignores the Route Convergence Recovery Transition because=20
it is obtained from the measured Convergence Packet Loss. =20
=20
Ideally, the Convergence Event Transition and Convergence=20
Recovery Transition are instantaneous so that the=20
Rate-Derived Convergence Time = Loss-Derived Convergence =
Time.
However, router implementations are less than ideal.
For these reasons the preferred reporting benchmark for IGP=20
Route Convergence is the Rate-Derived Convergence Time. =
=20
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Guidelines for reporting Loss-Derived Convergence Time are=20
provided in [2].
=20
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=20
without additional packet loss. =20
Discussion:
The purpose of the Sustained Forwarding Convergence Time is to=20
produce Convergence benchmarks protected against fluctuation=20
in Throughput after Full Convergence is observed. The=20
Sustained Forwarding Convergence Time to be used is calculated =
as shown in Equation 3.
=20
(eq 3)
Sustained Forwarding Convergence Time = 5 packets/Offered =
Load =20
units are packets/pps = sec
=20
for which at least one packet per route in the FIB for all=20
routes in the FIB MUST be offered to the DUT per second.
=20
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=20
a Convergence Event.
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Discussion:
Restoration Convergence Time is the amount of time for routes=20
to converge to the original outbound port. This is achieved=20
by recovering from the Convergence Event, such as restoring=20
the failed link. Restoration Convergence Time is measured=20
using the Rate-Derived Convergence Time calculation technique,=20
as provided in Equation 1. It is possible to have the=20
Restoration Convergence Time differ from the Rate-Derived=20
Convergence Time.
Measurement Units:
seconds or milliseconds
=20
Issues: =20
None =20
See Also:
Convergence Event
Rate-Derived Convergence Time
3.14 Packet Sampling Interval
Definition: =20
The interval at which the tester (test equipment) polls to make =
measurements for arriving packet flows.
Discussion:=20
Metrics measured at the Packet Sampling Interval may include
Throughput and Convergence Packet Loss.
Measurement Units:
seconds or milliseconds
Issues: =20
Packet Sampling Interval can influence the Convergence Graph.
This is particularly true when implementations achieve Full=20
Convergence in less than 1 second. The Convergence Event=20
Transition and Convergence Recovery Transition can become=20
exaggerated when the Packet Sampling Interval is too long. =20
This will produce a larger than actual Rate-Derived=20
Convergence Time. The recommended value for configuration=20
of the Packet Sampling Interval is provided in [2].
=20
See Also:
Convergence Packet Loss
Convergence Event Transition
Convergence Recovery Transition
=20
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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=20
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=20
connected to any interface on the DUT.
Discussion:
None
Measurement Units:
N/A
Issues:
None
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See Also:
Local Interface
Neighbor Interface
3.18 Preferred Egress Interface
Definition:
The outbound interface from the DUT for traffic routed to the=20
preferred next-hop.
Discussion:
The Preferred Egress Interface is the egress interface prior=20
to a Convergence Event.=20
Measurement Units:
N/A
Issues:
None
See Also:
Next-Best Egress Interface=20
3.19 Next-Best Egress Interface
Definition:
The outbound interface from the DUT for traffic routed to the=20
second-best next-hop. It is the same media type and link speed
as the Preferred Egress Interface
Discussion:
The Next-Best Egress Interface becomes the egress interface=20
after a Convergence Event.
Measurement Units:
N/A
Issues: =20
None
See Also:
Preferred Egress Interface=20
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3.20 Stale Forwarding
Definition:
Forwarding of traffic to route entries that no longer exist=20
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 produce packet loss.
Stale Forwarding exists until Network Convergence is achieved.
=20
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=20
is converging from a prior Convergence Event. =20
Discussion:
The Convergence Events for a Nested Convergence Events
MUST occur with different neighbors. A common=20
observation from a Nested Convergence Event will be=20
the withdrawal of routes from one neighbor while the=20
routes of another neighbor are being installed.
=20
Measurement Units:
N/A
Issues:
None
See Also:
Convergence Event
4. IANA Considerations
This document requires no IANA considerations.
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5. 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 production
networks.
6. Acknowledgements
Thanks to Sue Hares, Al Morton, Kevin Dubray, and participants of=20
the BMWG for their contributions to this work.=20
7. References
7.1 Normative References
[1] Poretsky, S., "Benchmarking Applicability for IGP Data Plane=20
Route Convergence", draft-ietf-bmwg-igp-dataplane-conv-app-10, =
work in progress, March 2006.
[2] Poretsky, S., "Benchmarking Methodology for IGP Data Plane=20
Route Convergence", =
draft-ietf-bmwg-igp-dataplane-conv-meth-10,=20
work in progress, March 2006.
[3] Callon, R., "Use of OSI IS-IS for Routing in TCP/IP and Dual=20
Environments", RFC 1195, December 1990.
[4] Moy, J., "OSPF Version 2", RFC 2328, IETF, April 1998.
7.2 Informative References
[5] S. Casner, C. Alaettinoglu, and C. Kuan, "A Fine-Grained View=20
of High Performance Networking", NANOG 22, June 2001.
[6] L. Ciavattone, A. Morton, and G. Ramachandran, "Standardized=20
Active Measurements on a Tier 1 IP Backbone", IEEE=20
Communications Magazine, pp90-97, May 2003.=20
8. Author's Address
Scott Poretsky
Reef Point Systems
8 New England Executive Park
Burlington, MA 01803=20
USA
Phone: + 1 508 439 9008
EMail: sporetsky@reefpoint.com
Poretsky, Imhoff [Page =
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INTERNET-DRAFT Benchmarking Terminology for March 2006
IGP Data Plane Route Convergence
Brent Imhoff
Juniper Networks
1194 North Mathilda Ave
Sunnyvale, CA 94089
USA
Phone: + 1 314 378 2571=20
EMail: bimhoff@planetspork.com
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