Network Working Group S. Poretsky
Internet Draft Allot Communications
Expires: April 2009
Intended Status: Informational Brent Imhoff
Juniper Networks
October 15, 2008
Terminology for Benchmarking
Link-State IGP Data Plane Route Convergence
<draft-ietf-bmwg-igp-dataplane-conv-term-16.txt>
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ABSTRACT
This document describes the terminology for benchmarking Interior
Gateway Protocol (IGP) Route Convergence. The terminology is to
be used for benchmarking IGP convergence time through externally
observable (black box) data plane measurements. The terminology
can be applied to any link-state IGP, such as ISIS and OSPF.
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Table of Contents
1. Introduction .................................................2
2. Existing definitions .........................................3
3. Term definitions..............................................4
3.1 Convergence Event.........................................4
3.2 Route Convergence.........................................4
3.3 Full Convergence..........................................5
3.4 Network Convergence.......................................5
3.5 Route-Specific Convergence................................6
3.6 Packet Loss...............................................7
3.7 Convergence Packet Loss...................................7
3.8 Convergence Event Instant.................................8
3.9 Convergence Recovery Instant..............................8
3.10 First Route Convergence Instant..........................9
3.11 Convergence Event Transition.............................9
3.12 Convergence Recovery Transition..........................10
3.13 Rate-Derived Convergence Time............................10
3.14 Loss-Derived Convergence Time............................11
3.15 Route-Specific Convergence Time..........................12
3.16 Sustained Convergence Validation Time....................13
3.17 First Route Convergence Time.............................14
3.18 Reversion Convergence Time...............................15
3.19 Packet Sampling Interval.................................15
3.20 Local Interface..........................................16
3.21 Neighbor Interface.......................................16
3.22 Remote Interface.........................................17
3.23 Preferred Egress Interface...............................17
3.24 Next-Best Egress Interface...............................17
3.25 Stale Forwarding.........................................18
3.26 Nested Convergence Events................................18
4. IANA Considerations...........................................19
5. Security Considerations.......................................19
6. Acknowledgements..............................................19
7. References....................................................19
8. Author's Address..............................................20
1. Introduction
This draft describes the terminology for benchmarking Interior
Gateway Protocol (IGP) Route Convergence. The motivation and
applicability for this benchmarking is provided in [Po07a]. The
methodology to be used for this benchmarking is described in [Po07m].
The methodology and terminology to be used for benchmarking Route
Convergence can be applied to any link-state IGP such as ISIS [Ca90]
and OSPF [Mo98]. 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 [Po07m].
These terms apply to IPv4 and IPv6 traffic and IGPs.
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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 Offered Load to the ingress interface of
the DUT SHOULD equal the measured maximum Throughput [Ba99][Ma98]
of the DUT and the Forwarding Rate [Ma98] is measured at the egress
interfaces of the DUT. The components of the graph and the metrics
are defined in the Term Definitions section.
Full Convergence,
Convergence Convergence
Recovery Event
Instant Instant Time = 0sec
Forwarding Rate = ^ ^ ^ Offered Load =
Offered Load --> ------\ Packet /-------- <---Max Throughput
\ Loss /<----Convergence
Convergence------->\ / Event Transition
Recovery Transition \ /
\_____/<------Maximum Packet Loss
^
First Route
Convergence Instant
Y-axis = Forwarding Rate
X-axis = Time (increases right to left to match commercial test
equipment displays)
Figure 1. Convergence Graph
2. Existing definitions
This document uses existing terminology defined in other BMWG
work. Examples include, but are not limited to:
Latency [Ref.[Ba91], section 3.8]
Frame Loss Rate [Ref.[Ba91], section 3.6]
Throughput [Ref.[Ba91], section 3.17]
Device Under Test (DUT) [Ref.[Ma98], section 3.1.1]
System Under Test (SUT) [Ref.[Ma98], section 3.1.2]
Out-of-order Packet [Ref.[Po06], section 3.3.2]
Duplicate Packet [Ref.[Po06], section 3.3.3]
Packet Reordering [Ref.[Mo06], section 3.3]
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
[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.
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3. Term Definitions
3.1 Convergence Event
Definition:
The occurrence of a planned or unplanned event in the network
that results in a change in the egress interface of the Device
Under Test (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
3.2 Route Convergence
Definition:
The action to update all components of the router with the
most recent route change(s) including the Routing
Information Base (RIB) and Forwarding Information Base (FIB),
along with software and hardware tables, such that forwarding
is successful for one or more route entries.
Discussion:
Route Convergence MUST occur after a Convergence Event.
Route Convergence can be observed externally by the rerouting
of data traffic to the Next-best Egress Interface. Also,
completion of Route Convergence may or may not be sustained
over time.
Measurement Units:
N/A
Issues:
None
See Also:
Network Convergence
Full Convergence
Convergence Event
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3.3 Full Convergence
Definition:
Route Convergence for an entire FIB in which complete recovery
from the Convergence Event is indicated by the DUT Throughput
equal to the offered load.
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. Completion of Full Convergence is externally
observable from the data plane when the Throughput of the data
plane traffic on the Next-Best Egress Interface equals the
offered load.
Full convergence MAY be measured using Rate-Derived Convergence
Time (3.13) or calculated using Loss-Derived Convergence Time
(3.14). When performing Route-Specific Convergence (3.5)
measurements, Full Convergence may be obtained by measuring the
maximum Route Specific Convergence Time (3.15). Full
Convergence may or may not be sustained over time. The
Sustained Convergence Validation Time (3.16) MUST be applied.
Measurement Units:
N/A
Issues:
None
See Also:
Network Convergence
Route Convergence
Convergence Event
3.4 Network Convergence
Definition:
The process of updating of all routing tables, including
distributed FIBs, in all routers throughout the network.
Discussion:
Network Convergence requires completion of all Route
Convergence operations for all routers in the network following
a Convergence Event. Completion of Network Convergence can be
observed by recovery of System Under Test (SUT) Throughput to
equal the offered load, with no Stale Forwarding, and no
Blenders [Ca01][Ci03].
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Measurement Units:
N/A
Issues:
None
See Also:
Route Convergence
Stale Forwarding
3.5 Route-Specific Convergence
Definition:
Route Convergence for one or more specific route entries in
the FIB in which recovery from the Convergence Event is
indicated by data-plane traffic for a flow [Po06] matching that
route entry(ies) being routed to the Next-Best Egress Interface.
Discussion:
When benchmarking convergence, it is sometimes useful to
measure the time to converge a single flow [Po06] or group of
flows to benchmark convergence time for one or a few route
entries in the FIB instead of the entire FIB. Route-Specific
Convergence of a flow is externally observable from the data
plane when the data plane traffic for that flow is routed to
the Next-Best Egress Interface.
Measurement Units:
N/A
Issues:
None
See Also:
Full Convergence
Route Convergence
Convergence Event
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3.6 Packet Loss
Definition:
The number of packets that should have been forwarded
by a DUT under a constant offered load that were
not forwarded due to lack of resources.
Discussion:
Packet Loss is a modified version of the term "Frame Loss Rate"
as defined in [Ba91]. The term "Frame Loss" is intended for
Ethernet Frames while "Packet Loss" is intended for IP packets.
Packet Loss can be measured as a reduction in forwarded traffic
from the Throughput [Ba91] of the DUT.
Measurement units:
Number of offered packets that are not forwarded.
Issues: None
See Also:
Convergence Packet Loss
3.7 Convergence Packet Loss
Definition:
The number of packets lost due to a Convergence Event
until Full Convergence completes.
Discussion:
Convergence Packet Loss includes packets that were lost and
packets that were delayed due to buffering. The Convergence
Packet Loss observed in a Packet Sampling Interval may or may
not be equal to the number of packets in the offered load
during the interval following a Convergence Event (see Figure
1).
Measurement Units:
number of packets
Issues: None
See Also:
Packet Loss
Route Convergence
Convergence Event
Packet Sampling Interval
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3.8 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:nnn:uuu,
where 'nnn' is milliseconds and 'uuu' is microseconds.
Issues:
None
See Also:
Convergence Event
Convergence Packet Loss
Convergence Recovery Instant
3.9 Convergence Recovery Instant
Definition:
The time instant that Full Convergence completion is
measured and then maintained for an interval of duration
equal to the Sustained Convergence Validation Time.
Discussion:
Convergence Recovery Instant is measurable from the data
plane as the precise time that the device under test
completes Full Convergence.
Measurement Units:
hh:mm:ss:nnn:uuu,
where 'nnn' is milliseconds and 'uuu' is microseconds.
Issues:
None
See Also:
Sustained Convergence Validation Time
Convergence Packet Loss
Convergence Event Instant
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3.10 First Route Convergence Instant
Definition:
The time instant a first route entry has converged
following a Convergence Event, as observed by receipt of
the first packet from the Next-Best Egress Interface.
Discussion:
The First Route Convergence Instant is an indication that the
process to achieve Full Convergence has begun. Any route may
be the first to converge for First Route Convergence Instant.
Measurement on the data-plane enables the First Route
Convergence Instant to be observed without any white-box
information from the DUT.
Measurement Units: N/A
Issues:
None
See Also:
Route Convergence
Full Convergence
Stale Forwarding
3.11 Convergence Event Transition
Definition:
A time interval observed following a Convergence Event in which
Throughput gradually reduces to a minimum value.
Discussion:
The Convergence Event Transition is best observed for Full
Convergence. The egress packet rate observed during a
Convergence Event Transition may not decrease linearly and may
not decrease to zero. Both the offered load and the Packet
Sampling Interval influence the observations of the Convergence
Event Transition. For example, even if the Convergence Event
were to cause the Throughput [Ba91] to drop to zero there would
be some number of packets observed, unless the Packet Sampling
Interval is exactly aligned with the Convergence Event. This
is further discussed with the term "Packet Sampling Interval".
Measurement Units:
seconds
Issues:
None
See Also:
Convergence Event
Full Convergence
Packet Sampling Interval
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3.12 Convergence Recovery Transition
Definition:
The characteristic of the DUT in which Throughput gradually
increases to equal the offered load.
Discussion:
The Convergence Recovery Transition is best observed for
Full Convergence. The egress packet rate observed during
a Convergence Recovery Transition may not increase linearly.
Both the offered load and the Packet Sampling Interval
influence the observations of the Convergence Recovery
Transition. This is further discussed with the term
"Packet Sampling Interval".
Measurement Units:
seconds
Issues: None
See Also:
Full Convergence
Packet Sampling Interval
3.13 Rate-Derived Convergence Time
Definition:
The amount of time for Convergence Packet Loss to persist upon
occurrence of a Convergence Event until Full Convergence has
completed.
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.
(Equation 1)
Rate-Derived Convergence Time =
Convergence Recovery Instant - Convergence Event Instant.
Discussion:
Rate-Derived Convergence Time SHOULD be measured at the maximum
Throughput of the DUT. At least one packet per route in the FIB
for all routes in the FIB MUST be offered to the DUT within the
Packet Sampling Interval.
Failure to achieve Full Convergence results in a Rate-Derived
Convergence Time benchmark of infinity. It is RECOMMENDED that
the Rate-Derived Convergence Time be measured when benchmarking
Full Convergence.
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Measurement Units:
seconds
Issues: None
See Also:
Convergence Packet Loss
Convergence Recovery Instant
Convergence Event Instant
Full Convergence
3.14 Loss-Derived Convergence Time
Definition:
The amount of time it takes for Full Convergence to be
completed as calculated from the amount of Convergence
Packet Loss. Loss-Derived Convergence Time can be
calculated from Convergence Packet Loss as shown with
Equation 2.
Equation 2 -
Loss-Derived Convergence Time =
Convergence Packets Loss / Offered Load
where units are packets / packets/second = seconds
Discussion:
Optimally, 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.
Loss-Derived Convergence Time gives a better than
actual result when converging many routes simultaneously
because it ignores the Convergence Recovery Transition.
Rate-Derived Convergence Time takes the Convergence Recovery
Transition into account. Equation 2 calculates the average
convergence time over all routes to which packets have been
sent. Since this average convergence time is in general
smaller than the maximum convergence time over all routes,
Loss-Derived Convergence Time is not the preferred metric to
indicate Full Convergence completion. For this reason the
RECOMMENDED benchmark metric for Full Convergence is the
Rate-Derived Convergence Time.
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Guidelines for reporting Loss-Derived Convergence Time are
provided in [Po07m].
Measurement Units:
seconds
Issues:
None
See Also:
Convergence Event
Convergence Packet Loss
Rate-Derived Convergence Time
Route-Specific Convergence
Convergence Event Transition
Convergence Recovery Transition
3.15 Route-Specific Convergence Time
Definition:
The amount of time it takes for Route-Specific Convergence to
be completed as calculated from the amount of Convergence
Packet Loss per flow.
Route-Specific Convergence Time can be calculated from
Convergence Packet Loss as shown with Equation 3.
Equation 3 -
Route-Specific Convergence Time =
Convergence Packets Loss / Offered Load
where units are packets / packets/second = seconds
Discussion:
It is possible to provide an offered load that has flows
matching every route entry in the FIB and benchmarking
Route-Specific Convergence Time for all route entries. The
number of flows that can be measured is dependent upon the flow
measurement capabilities of the Tester. When benchmarking
Route-Specific Convergence, Convergence Packet Loss is measured
for specific flow(s) and Equation 3 is applied for each flow.
Each flow has a single destination address matching a different
route entry. The fastest measurable convergence time is equal
to the time between two consecutive packets of a flow offered
by the Tester.
The Route-Specific Convergence Time benchmarks enable minimum,
maximum, average, and median convergence time measurements to be
reported by comparing the results for the different route
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entries. It also enables benchmarking of convergence time when
configuring a priority value for route entry(ies). Since
multiple Route-Specific Convergence Times can be measured it is
possible to have an array of results. The format for reporting
Route-Specific Convergence Time is provided in [Po07m].
The Route-Specific Convergence Time MAY be used to benchmark
Full Convergence when used in combination with many flows
matching every FIB entry. In this case
Full Convergence = max(Route-Specific Convergence Time).
Measurement Units:
seconds
Issues:
None
See Also:
Convergence Event
Convergence Packet Loss
Route-Specific Convergence
3.16 Sustained Convergence Validation Time
Definition:
The amount of time for which the completion of Full
Convergence is maintained without additional packet loss.
Discussion:
The purpose of the Sustained Convergence Validation Time is to
produce Convergence benchmarks protected against fluctuation
in Throughput after the completion of Full Convergence is
observed. The RECOMMENDED Sustained Convergence Validation
Time to be used is 5 seconds. The BMWG selected 5 seconds
based upon RFC 2544 [Ba99] which recommends waiting 2 seconds
for residual frames to arrive and 5 seconds for DUT
restabilization.
Measurement Units:
seconds
Issues: None
See Also:
Full Convergence
Convergence Recovery Instant
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3.17 First Route Convergence Time
Definition:
The amount of time for Convergence Packet Loss until the
convergence of a first route entry on the Next-Best Egress
Interface, as indicated by the First Route Convergence
Instant.
Discussion:
The First Route Convergence Time benchmarking metric can be
measured when benchmarking either Full Convergence or
Route-Specific Convergence. When benchmarking Full Convergence,
First Route Convergence Time can be measured as the time
difference from the Convergence Event Instant and the First
Route Convergence Instant, as shown with Equation 4a.
(Equation 4a)
First Route Convergence Time =
First Route Convergence Instant - Convergence Event Instant
When benchmarking Route-Specific Convergence, First Route
Convergence Time can be measured as the minimum Route-Specific
Convergence Time, as shown with Equation 4b.
(Equation 4b)
First Route Convergence Time =
min(Route-Specific Convergence Time)
First Route Convergence Time should be measured at the maximum
Throughput of the DUT. At least one packet per route in the FIB
for all routes in the FIB MUST be offered to the DUT within the
Packet Sampling Interval. Failure to achieve the First Route
Convergence Instant results in a First Route Convergence Time
benchmark of infinity.
Measurement Units:
seconds
Issues: None
See Also:
Convergence Packet Loss
First Route Convergence Instant
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3.18 Reversion Convergence Time
Definition:
The amount of time for the DUT to complete Full Convergence
to the Preferred Egress Interface, instead of the Next-Best
Egress Interface, upon recovery from a Convergence Event.
Discussion:
Reversion Convergence Time is the amount of time for Full
Convergence to the original egress interface. This is
achieved by recovering from the Convergence Event, such as
restoring the failed link. Reversion Convergence Time is
measured using the Rate-Derived Convergence Time calculation
technique, as provided in Equation 1. It is possible to have
the Reversion Convergence Time differ from the Rate-Derived
Convergence Time.
Measurement Units: seconds
Issues: None
See Also:
Preferred Egress Interface
Convergence Event
Rate-Derived Convergence Time
3.19 Packet Sampling Interval
Definition:
The interval at which the tester (test equipment) polls to make
measurements for arriving packet flows.
Discussion:
At least one packet per route in the FIB for all routes in the
FIB MUST be offered to the DUT within the Packet Sampling
Interval. Metrics measured at the Packet Sampling Interval
MUST include Forwarding Rate and Convergence Packet Loss.
Packet Sampling Interval can influence the Convergence Graph.
This is particularly true when implementations complete Full
Convergence in less than the Packet Sampling Interval. 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 [Po07m].
Measurement Units: seconds
Issues: None
See Also:
Convergence Packet Loss
Convergence Event Transition
Convergence Recovery Transition
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3.20 Local Interface
Definition:
An interface on the DUT.
Discussion:
A failure of the Local Interface indicates that the failure
occurred directly on the DUT.
Measurement Units:
N/A
Issues:
None
See Also:
Neighbor Interface
Remote Interface
3.21 Neighbor Interface
Definition:
The interface on the neighbor router or tester that is
directly linked to the DUT's Local Interface.
Discussion:
A failure of a Neighbor Interface indicates that a
failure occurred on a neighbor router's interface that
directly links the neighbor router to the DUT.
Measurement Units:
N/A
Issues:
None
See Also:
Local Interface
Remote Interface
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3.22 Remote Interface
Definition:
An interface on a neighboring router that is not directly
connected to any interface on the DUT.
Discussion:
A failure of a Remote Interface indicates that the failure
occurred on a neighbor router's interface that is not
directly connected to the DUT.
Measurement Units:
N/A
Issues:
None
See Also:
Local Interface
Neighbor Interface
3.23 Preferred Egress Interface
Definition:
The outbound interface from the DUT for traffic routed to the
preferred next-hop.
Discussion:
The Preferred Egress Interface is the egress interface prior
to a Convergence Event.
Measurement Units:
N/A
Issues:
None
See Also:
Next-Best Egress Interface
3.24 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:
The Next-Best Egress Interface becomes the egress interface
after a Convergence Event.
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Measurement Units:
N/A
Issues: None
See Also:
Preferred Egress Interface
3.25 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 can
manifest as a "black-hole" or microloop that produces packet
loss. Stale Forwarding can exist until Network Convergence is
completed. Stale Forwarding cannot be observed with a single
DUT.
Measurement Units:
N/A
Issues: None
See Also:
Network Convergence
3.26 Nested Convergence Events
Definition:
The occurrence of a Convergence Event while the route
table is converging from a prior Convergence Event.
Discussion:
The Convergence Events for a Nested Convergence Event
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
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4. IANA Considerations
This document requires no IANA considerations.
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, Ron Bonica, David Ward,
Kris Michielsen and the BMWG for their contributions to this work.
7. References
7.1 Normative References
[Ba91] Bradner, S. "Benchmarking Terminology for Network
Interconnection Devices", RFC1242, July 1991.
[Ba99] Bradner, S. and McQuaid, J., "Benchmarking
Methodology for Network Interconnect Devices",
RFC 2544, March 1999.
[Br97] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997
[Ca90] Callon, R., "Use of OSI IS-IS for Routing in TCP/IP and Dual
Environments", RFC 1195, December 1990.
[Ma98] Mandeville, R., "Benchmarking Terminology for LAN
Switching Devices", RFC 2285, February 1998.
[Mo98] Moy, J., "OSPF Version 2", RFC 2328, IETF, April 1998.
[Mo06] Morton, A., et al, "Packet Reordering Metrics", RFC 4737,
November 2006.
[Po06] Poretsky, S., et al., "Terminology for Benchmarking
Network-layer Traffic Control Mechanisms", RFC 4689,
November 2006.
[Po07a] Poretsky, S., "Benchmarking Applicability for Link-State
IGP Data Plane Route Convergence",
draft-ietf-bmwg-igp-dataplane-conv-app-16, work in progress,
October 2008.
[Po07m] Poretsky, S. and Imhoff, B., "Benchmarking Methodology for
Link-State IGP Data Plane Route Convergence",
draft-ietf-bmwg-igp-dataplane-conv-meth-16, work in progress,
October 2008.
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7.2 Informative References
[Ca01] S. Casner, C. Alaettinoglu, and C. Kuan, "A Fine-Grained View
of High Performance Networking", NANOG 22, June 2001.
[Ci03] L. Ciavattone, A. Morton, and G. Ramachandran, "Standardized
Active Measurements on a Tier 1 IP Backbone", IEEE
Communications Magazine, pp90-97, May 2003.
8. Author's Address
Scott Poretsky
Allot Communications
67 South Bedford Street, Suite 400
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Email: sporetsky@allot.com
Brent Imhoff
Juniper Networks
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Sunnyvale, CA 94089
USA
Phone: + 1 314 378 2571
EMail: bimhoff@planetspork.com
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Poretsky, Imhoff [Page 20]
INTERNET-DRAFT Benchmarking Terminology for October 2008
Link-State IGP Data Plane Route Convergence
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Poretsky, Imhoff [Page 21]
