Network Working Group
INTERNET-DRAFT
Expires in: April 2004
Scott Poretsky
Quarry Technologies
Brent Imhoff
Wiltel Communications
October 2003
Terminology for Benchmarking
IGP Data Plane Route Convergence
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
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Table of Contents
1. Introduction ...............................................2
2. Existing definitions .......................................2
3. Term definitions............................................3
3.1 Network Convergence.......................................3
3.2 Protocol Convergence......................................3
3.3 Route Convergence.........................................4
3.4 Convergence Event.........................................4
3.5 Full Convergence..........................................4
3.6 Convergence Packet Loss...................................5
3.7 Convergence Event Instant.................................5
3.8 Convergence Recovery Transition...........................6
3.9 Rate-Derived Convergence Time.............................6
3.10 Convergence Recovery Instant.............................7
3.11 Convergence Event Transition.............................7
3.12 Loss-Derived Convergence Time............................8
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3.13 Route Convergence Time...................................9
3.14 Restoration Convergence Time.............................9
3.15 Packet Sampling Interval.................................10
3.16 Local Interface..........................................10
3.17 Neighbor Interface.......................................10
3.18 Remote Interface.........................................11
3.19 Preferred Egress Interface...............................11
3.20 Next-Best Egress Interface...............................12
4. Security Considerations.....................................12
5. References..................................................12
6. Author's Address............................................12
7. Full Copyright Statement....................................13
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].
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 of this document.
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. Convergence Graph
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.
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3. Term Definitions
3.1 Network Convergence
Definition:
The completion of updating of all routing tables, including the
FIB, in all routers throughout the network.
Discussion:
Network Convergence can be approximated to the sum of Route
Convergence for all routers in the network. Network Convergence
can only be determined by the occurrence of packet loss or stale
forwarding due to an out-of-date FIB.
Measurement Units:
N/A
Issues:
None
See Also:
Protocol Convergence
Route Convergence
3.2 Protocol Convergence
Definition:
The completion of updating a router's RIB and the forwarding of
an route update message (LSA for OSPF/LSP for ISIS) to a
neighboring peer.
Discussion:
Protocol Convergence considers only the Control Plane. IGP
messaging is used to verify and measure convergence. Updating
of the FIB, hardware updating, rerouting of traffic, and packet
loss are not considered.
Measurement Units:
N/A
Issues:
Protocol Convergence does not consider updating of the FIB,
hardware updating, rerouting of traffic, and resulting packet
loss. Protocol Convergence is only a partial measurement of
Route Convergence.
See Also:
Network Convergence
Route Convergence
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3.3 Route Convergence
Definition:
The completion of the router's FIB becoming fully converged.
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
Protocol Convergence
Full Convergence
Convergence Event
3.4 Convergence Event
Definition:
The occurrence of a planned or unplanned action in the network
that results in a change to an entry in the route table.
Discussion:
Convergence Events include link loss, routing protocol session
loss, router failure, and better next-hop.
Measurement Units:
N/A
Issues:
None
See Also:
Convergence Packet Loss
Convergence Event Instant
3.5 Full Convergence
Definition:
Route Convergence for an entire route table.
Discussion:
When benchmarking convergence it is useful to measure
The time to convergence an entire route table. For example,
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A Convergence Event can produced for an OSPF table of 5000
routes so that the time to converge routes 1 through 5000
is measured.
Measurement Units:
N/A
Issues:
None
See Also:
Network Convergence
Protocol Convergence
Route Convergence
Convergence Event
3.6 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.
Measurement Units:
number of packets
Issues:
None
See Also:
Route Convergence
Convergence Event
Rate-Derived Convergence Time
Loss-Derived Convergence Time
3.7 Convergence Event Instant
Definition:
The time instant that a Convergence Event occurs.
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
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Issues:
None
See Also:
Route Convergence
Convergence Event
Convergence Packet Loss
Convergence Recovery Instant
3.8 Convergence Recovery Instant
Definition:
The time instant that Route Convergence occurs.
Discussion:
Convergence Recovery Instant is observable from the data
plane as the precise time that the device under test no
longer exhibits packet loss.
Measurement Units:
hh:mm:ss:uuu
Issues:
None
See Also:
Route Convergence
Convergence Packet Loss
Convergence Event Instant
3.9 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.
Discussion:
Rate-Derived Convergence Time can be measured as the time
difference from the Convergence Event Instant to the
Convergence Reovery Instant, as shown with Equation 1.
(eq 1) Rate-Derived Convergence Time =
Convergence Recovery Instant - Convergence Event Instant.
Rate-Derived Convergence Time can be measured at the maximum
forwarding rate.
Measurement Units:
seconds/milliseconds
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Issues:
None
See Also:
Route Convergence
Convergence Packet Loss
Loss-Derived Convergence Time
3.10 Loss-Derived Convergence Time
Definition:
The amount of time it takes for Route Convergence to
complete as calculated from the amount of packet loss
and known forwarding rate.
Discussion:
It can be calculated from 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 / Forwarding Rate
NOTE: Units for this measurement are
packets / packets/second = seconds
Measurement Units:
seconds/milliseconds
Issues:
Loss-Derived Convergence time gives a better than
actual result when converging many routes simultaneously.
Because of this the preferred reporting metric in most
Cases is Rate-Derived Convergence Time.
See Also:
Route Convergence
Convergence Packet Loss
Rate-Derived Convergence Time
Convergence Event Transition
Convergence Recovery Transition
3.11 Convergence Event Transition
Definition:
The characteristic of A router in which forwarding rate
gradually reaches zero as output queues drain after a
network event.
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Discussion:
Rate-Derived Convergence Time ignores the Convergence Event
Transition. Loss-Derived Convergence Time based upon the amount
of packet loss takes the Convergence Event Transition into
account. The Convergence Event Transition is best observed for
Full Convergence.
Measurement Units:
seconds/milliseconds
Issues:
None
See Also:
Route Convergence
Convergence Event
Rate-Derived Convergence Time
Loss-Derived Convergence Time
Convergence Packet Loss
Convergence Recovery Transition
3.12 Convergence Recovery Transition
Definition:
The characteristic of a router in which forwarding rate
gradually rises to the maximum value as many routes
converge to recover from a network event.
Discussion:
Rate-Derived Convergence Time ignores the Route
Convergence Recovery Transition. Loss-Derived Convergence
Time based upon the amount of packet loss takes the
Convergence Recovery Transition into account. The
Convergence Recovery Transition is best observed for Full
Convergence.
Measurement Units:
seconds/milliseconds
Issues:
None
See Also:
Route Convergence
Rate-Derived Convergence Time
Loss-Derived Convergence Time
Convergence Packet Loss
Convergence Event Transition
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3.13 Route Convergence Time
Definition:
The amount of time it takes for Route Convergence to
complete as observed from rerouting traffic to a
new egress interface due to a change in next-hop without
packet loss.
Discussion:
Route Convergence Time is the IGP Route Convergence
benchmark to be used for network events that produce
a change in next-hop without packet loss.
Measurement Units:
seconds/milliseconds
Issues:
None
See Also:
Route Convergence
Rate-Derived Convergence Time
Loss-Derived Convergence Time
3.14 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.
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 Convegence Time
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3.15 Packet Sampling Interval
Definition:
The rate at which the tester (test equipment) polls to make
measurements for arriving packet flows.
Discussion:
Metrics measured at the Packet Sampling Interval include
packets received and Convergence Packet Loss.
Measurement Units:
seconds or milliseconds
Issues:
Packet Sampling Interval can influence the Convergence Graph.
This is particularly true as Full Convergence less than 1 second
is achieved. 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. Guidelines for use of
the Packet Sampling Interval are provided in [2].
See Also:
Convergence Packet Loss
Convergence Event Transition
Convergence Recovery Transition
3.16 Local Interface
Definition:
An interface on the DUT.
Discussion:
None
Measurement Units:
N/A
Issues:
None
See Also:
Neighbor Interface
Remote interface
3.17 Neighbor Interface
Definition:
The interface on the neighbor router or tester that is
directly linked to the DUT's Local Interface.
Discussion:
None
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Measurement Units:
N/A
Issues:
None
See Also:
Local Interface
Remote interface
3.18 Remote Interface
Definition:
An interface on a neighboring router that is not directly
linked to any interface on the DUT.
Discussion:
None
Measurement Units:
N/A
Issues:
None
See Also:
Local interface
Neighbor Interface
3.19 Preferred Egress Interface
Definition:
The outbound interface on DUT 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
Convergence Event
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3.20 Next-Best Egress Interface
Definition:
The outbound interface on DUT to the second-best next-hop.
Discussion:
Next-Best Egress Interface is the egress interface after to
a Convergence Event
Measurement Units:
N/A
Issues:
None
See Also:
Preferred Egress Interface
Convergence Event
4. Security Considerations
Documents of this type do not directly effect the security of
the Internet or of corporate networks as long as benchmarking
is not performed on devices or systems connected to operating
networks.
5. References
[1] Poretsky, S., "Benchmarking Applicability for IGP Data Plane
Route Convergence", draft-ietf-bmwg-igp-dataplane-conv-app-01,
work in progress, October 2003.
[2] Poretsky, S., "Benchmarking Methodology for IGP Data Plane
Route Convergence", draft-ietf-bmwg-igp-dataplane-conv-meth-01,
work in progress, 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.
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
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Brent Imhoff
WilTel Communications
3180 Rider Trail South
Bridgeton, MO 63045 USA
Phone: +1 314 595 6853
EMail: brent.imhoff@wcg.com
7. Full Copyright Statement
Copyright (C) The Internet Society (1998). All Rights
Reserved.
This document and translations of it may be copied and
furnished to others, and derivative works that comment on or
otherwise explain it or assist in its implementation may be
prepared, copied, published and distributed, in whole or in
part, without restriction of any kind, provided that the above
copyright notice and this paragraph are included on all such
copies and derivative works. However, this document itself may
not be modified in any way, such as by removing the copyright
notice or references to the Internet Society or other Internet
organizations, except as needed for the purpose of developing
Internet standards in which case the procedures for copyrights
defined in the Internet Standards process must be followed, or
as required to translate it into languages other than English.
The limited permissions granted above are perpetual and will
not be revoked by the Internet Society or its successors or
assigns. This document and the information contained herein is
provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE
INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY
THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY
RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR PURPOSE.
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