Network Working Group
INTERNET-DRAFT
Expires in: December 2003
Scott Poretsky
Avici Systems
June 2003
Benchmarking Applicability for
IGP Data Plane Route Convergence
<draft-ietf-bmwg-igp-dataplane-conv-app-00.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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ABSTRACT
This draft describes the applicability of IGP Route Convergence
benchmarking methodology [1] and IGP Route Convergence bechmarking
terminology [2]. The methodology and terminology is to be used
for benchmarking route convergence and can be applied to any
link-state IGP such as ISIS [3] and OSPF [4]. The data plane is
measured to obtain the convergence benchmarking metrics described
in [1].
Table of Contents
1. Introduction ...............................................2
2. Existing definitions .......................................2
3. Factors for IGP Route Convergence Time......................2
4. Network Events that Cause Route Convergence.................3
5. Use of Data Traffic for IGP Route Convergence Benchmarking..3
6. Security Considerations.....................................4
7. Acknowledgements............................................4
8. References..................................................4
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9. Author's Address............................................5
10. Full Copyright Statement...................................5
1. Introduction
IGP Convergence is a critical performance parameter. Customers
of Service Providers use packet loss due to IGP Convergence as a
key metric of their network service quality. Service Providers
use IGP Convergence time as a key metric of router design and
architecture. Fast network convergence can be optimally achieved
through deployment of fast converging routers. The fundamental
basis by which customers of service providers benchmark convergence
is packet loss, which is an externally observable event having
direct impact on their application performance. IGP Route
Convergence is a Direct Measure of Quality (DMOQ) when benchmarking
the data plane. For this reason it is important to develop a standard
router benchmarking methodology and terminology for measuring IGP
convergence that uses the data plane as described in [1] and [2].
This document describes all of the factors that influence a
convergence measurement and how a purely black box test can be
designed to account for all of these factors. This enables accurate
benchmarking and evaluation for route convergence time.
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. Factors for IGP Route Convergence Time
There are four major categories of factors for the measured Router
IGP Convergence Time, as described in [5], [6], [7], [8] and [9].
These are Event Detection, SPF Processing, IGP Advertisement, and
FIB Update. Each of these factors has numerous components to
influence the convergence time. These are listed as follow:
-Event Detection-
SONET failure indication time
PPP failure indication time
IGP Hello Dead Interval
-SPF Processing-
SPF Delay Time
SPF Hold time
SPF Execution time
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-IGP Advertisement-
LSA/LSP Flood Packet Pacing
LSA/LSP Retransmission Packet Pacing
LSA/LSP Generation time
-FIB Update-
Tree Build time
Hardware Update time
Each of the factors listed above will have a varying amount of
influence on the convergence result with each router vendors'
architecture and IGP implementation. It is necessary to design a
convergence test that considers not just one or a few of these
components, but instead all of these components. The additional
benefit of designing a test for all components is that it enables
black-box testing in which knowledge of the routers' internal
implementations is not required. It is then possible to make
valid use of the benchmarking metrics when comparing routers from
different vendors.
4. Network Events that Cause Convergence
There are different types of network events that can cause IGP
convergence. These network events are administrative link
removal, unplanned link removal, and route change such as
withdrawal, flap, next-hop change, and cost change. When
benchmarking a router it is important to measure the convergence
time for local and remote occurrence of these network events.
The convergence time measured will vary whether the network event
occurred locally or remotely due to varying combinations of
factors listed in the previous sections. This behavior makes it
possible to design purely black-box tests that isolate
measurements for each of the components of convergence time.
5. Use of Data Plane for IGP Route Convergence Benchmarking
Customers of service providers use packet loss as the metric for
convergence time. Packet loss is an externally observable event
having direct impact on customers' application performance.
For this reason it is important to develop a standard router
benchmarking methodology and terminology that is a Direct Measure
of Quality (DMOQ)for measuring IGP convergence. Such a
methodology uses the data plane as described in [1] and [2].
An additional benefit of using packet loss for calculation of
IGP Route Convergence time is that it enables black-box tests to
be designed. Data traffic can be offered at line-rate to the
device under test (DUT), an emulated network event can be forced
to occur, and packet loss can be externally
observed to measure the convergence time. Knowledge of the DUT
architecture and IGP implementation is not required. There is no
need to rely on the DUT to produce the test results. There is no
need to build intrusive test harnasses for the DUT.
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Use of data traffic and measurement of packet loss on the data
plane also enables Route Convergence methodology test cases that
consider the time for the Route Controller to update the FIB on
the forwarding engine of the hardware. A router is not fully
converged until all components are updated and traffic is
rerouted along the correct path. As long as there is packet
loss, routes have not converged. It is possible to send diverse
traffic flows to destinations matching every route in the FIB
so that the time it takes for the router to converge an entire
route table can be benchmarked.
6. 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.
7. Acknowledgements
Thanks to Curtis Villamizar for sharing so much of his
knowledge and experience through the years. Also, special
thanks to the many Network Engineers and Network Architects
at the Service Providers who are always eager to discuss
Route Convergence.
8. References
[1] Poretsky, S., "Benchmarking Methodology for IGP Data Plane
Route Convergence", draft-ietf-bmwg-igp-dataplane-conv-meth-00,
work in progress, June 2003.
[2] Poretsky, S., "Benchmarking Terminology for IGP Data Plane
Route Convergence", draft-ietf-bmwg-igp-dataplane-conv-term-00,
work in progress, June 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.
[5] Villamizar, C., "Convergence and Restoration Techniques for
ISP Interior Routing", NANOG 25, June 2002.
[6] Katz, D., "Why are we Scared of SPF? IGP Scaling and
Stability", NANOG 25, June 2002.
[7] Filsfils, C., "Deploying Tight-SLA Services on an Internet
Backbone: ISIS Fast Convergence and Differentiated Services
Design (tutorial)", NANOG 25, June 2002.
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[8] Alaettinoglu, C. and Casner, S., "ISIS Routing on the Qwest
Backbone: a Recipe for Subsecond ISIS Convergence", NANOG 24,
June 2002.
[9] Alaettinoglu, C., Jacobson, V., and Yu, H., "Towards
Millisecond IGP Convergence", NANOG 20, October 2000.
9. Author's Address
Scott Poretsky
Avici Systems, Inc.
101 Billerica Avenue
N. Billerica, MA 01862
USA
Phone: + 1 978 964 2287
EMail: sporetsky@avici.com
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