draft-ietf-idr-rfd-usable-04.txt   rfc7196.txt 
Network Working Group C. Pelsser Internet Engineering Task Force (IETF) C. Pelsser
Internet-Draft R. Bush Request for Comments: 7196 R. Bush
Intended status: Standards Track Internet Initiative Japan Category: Standards Track Internet Initiative Japan
Expires: April 14, 2014 K. Patel ISSN: 2070-1721 K. Patel
Cisco Systems Cisco Systems
P. Mohapatra P. Mohapatra
Cumulus Systems, Inc. Sproute Networks
O. Maennel O. Maennel
Loughborough University Loughborough University
October 11, 2013 May 2014
Making Route Flap Damping Usable Making Route Flap Damping Usable
draft-ietf-idr-rfd-usable-04
Abstract Abstract
Route Flap Damping (RFD) was first proposed to reduce BGP churn in Route Flap Damping (RFD) was first proposed to reduce BGP churn in
routers. Unfortunately, RFD was found to severely penalize sites for routers. Unfortunately, RFD was found to severely penalize sites for
being well-connected because topological richness amplifies the being well connected because topological richness amplifies the
number of update messages exchanged. Many operators have turned RFD number of update messages exchanged. Many operators have turned RFD
off. Based on experimental measurement, this document recommends off. Based on experimental measurement, this document recommends
adjusting a few RFD algorithmic constants and limits, to reduce the adjusting a few RFD algorithmic constants and limits in order to
high risks with RFD, with the result being damping a non-trivial reduce the high risks with RFD. The result is damping a non-trivial
amount of long term churn without penalizing well-behaved prefixes' amount of long-term churn without penalizing well-behaved prefixes'
normal convergence process. normal convergence process.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to
be interpreted as described in RFC 2119 [RFC2119] only when they
appear in all upper case. They may also appear in lower or mixed
case as English words, without normative meaning.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
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time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on April 14, 2014. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7196.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Suggested Reading . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Suggested Reading . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. RFD Parameters . . . . . . . . . . . . . . . . . . . . . . . 3 3. RFD Parameters . . . . . . . . . . . . . . . . . . . . . . . 3
4. Suppress Threshold Versus Churn . . . . . . . . . . . . . . . 4 4. Suppress Threshold versus Churn . . . . . . . . . . . . . . . 4
5. Maximum Penalty . . . . . . . . . . . . . . . . . . . . . . . 4 5. Maximum Penalty . . . . . . . . . . . . . . . . . . . . . . . 4
6. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 5 6. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5 7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 9.1. Normative References . . . . . . . . . . . . . . . . . . 6
10.1. Normative References . . . . . . . . . . . . . . . . . . 5 9.2. Informative References . . . . . . . . . . . . . . . . . 6
10.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Suggested Reading
It is assumed that the reader understands BGP, [RFC4271] and Route 1. Introduction
Flap Damping, [RFC2439]. This work is based on the measurements in
the paper [pelsser2011]. A survey of Japanese operators' use of RFD
and their desires is reported in
[I-D.shishio-grow-isp-rfd-implement-survey].
2. Introduction Route Flap Damping (RFD) was first proposed (see [RIPE178] and
Route Flap Damping (RFD) was first proposed (see [ripe178] and
[RFC2439]) and subsequently implemented to reduce BGP churn in [RFC2439]) and subsequently implemented to reduce BGP churn in
routers. Unfortunately, RFD was found to severely penalize sites for routers. Unfortunately, RFD was found to severely penalize sites for
being well-connected because topological richness amplifies the being well connected because topological richness amplifies the
number of update messages exchanged, see [mao2002]. Subsequently, number of update messages exchanged, see [MAO2002]. Subsequently,
many operators turned RFD off, see [ripe378]. Based on the many operators turned RFD off; see [RIPE378]. Based on the
measurements of [pelsser2011], [ripe580] now recommends that RFD is measurements of [PELSSER2011], [RIPE580] now recommends that RFD is
usable with some changes to the parameters. Based on the same usable with some changes to the parameters. Based on the same
measurements, this document recommends adjusting a few RFD measurements, this document recommends adjusting a few RFD
algorithmic constants and limits, with the result being damping of a algorithmic constants and limits. The result is damping of a non-
non-trivial amount of long term churn without penalizing well-behaved trivial amount of long-term churn without penalizing well-behaved
prefixes' normal convergence process. prefixes' normal convergence process.
Very few prefixes are responsible for a large amount of the BGP Very few prefixes are responsible for a large amount of the BGP
messages received by a router, see [huston2006] and [pelsser2011]. messages received by a router; see [HUSTON2006] and [PELSSER2011].
For example, the measurements in [pelsser2011] showed that only 3% of For example, the measurements in [PELSSER2011] showed that only 3% of
the prefixes were responsible for 36% percent of the BGP messages at the prefixes were responsible for 36% percent of the BGP messages at
a router with real feeds from a Tier-1 and an Internet Exchange Point a router with real feeds from a Tier-1 provider and an Internet
during a one week experiment. Only these very frequently flapping Exchange Point during a one-week experiment. Only these very
prefixes should be damped. The values recommended in Section 6 frequently flapping prefixes should be damped. The values
achieve this. Thus, RFD can be enabled, and some churn reduced. recommended in Section 6 achieve this. Thus, RFD can be enabled, and
some churn reduced.
The goal is to, with absolutely minimal change, ameliorate the danger The goal is to, with absolutely minimal change, ameliorate the danger
of current RFD implementations and use. It is not a panacea, nor is of current RFD implementations and use. It is not a panacea, nor is
it a deep and thorough approach to flap reduction. it a deep and thorough approach to flap reduction.
1.1. Suggested Reading
It is assumed that the reader understands BGP [RFC4271] and Route
Flap Damping [RFC2439]. This work is based on the measurements in
the paper [PELSSER2011]. A survey of Japanese operators' use of RFD
and their desires is reported in [RFD-SURVEY].
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to
be interpreted as described in RFC 2119 [RFC2119] only when they
appear in all upper case. They may also appear in lower or mixed
case as English words, without normative meaning.
3. RFD Parameters 3. RFD Parameters
The following RFD parameters are common to all implementations. Some The following RFD parameters are common to all implementations. Some
may be tuned by the operator, some not. There is currently no may be tuned by the operator, some not. There is currently no
consensus on a single set of default values. consensus on a single set of default values.
+-------------------------+----------+-------+---------+ +--------------------------+----------+-------+---------+
| Parameter | Tunable? | Cisco | Juniper | | Parameter | Tunable? | Cisco | Juniper |
+-------------------------+----------+-------+---------+ +--------------------------+----------+-------+---------+
| Withdrawal | No | 1000 | 1000 | | Withdrawal | No | 1,000 | 1,000 |
| Re-Advertisement | No | 0 | 1000 | | Re-Advertisement | No | 0 | 1,000 |
| Attribute Change | No | 500 | 500 | | Attribute Change | No | 500 | 500 |
| Suppress Threshold | Yes | 2000 | 3000 | | Suppress Threshold | Yes | 2,000 | 3,000 |
| Half-Life (min) | Yes | 15 | 15 | | Half-Life (min.) | Yes | 15 | 15 |
| Reuse Threshold | Yes | 750 | 750 | | Reuse Threshold | Yes | 750 | 750 |
| Max Suppress Time (min) | Yes | 60 | 60 | | Max Suppress Time (min.) | Yes | 60 | 60 |
+-------------------------+----------+-------+---------+ +--------------------------+----------+-------+---------+
Default RFD Paramaters of Juniper and Cisco Note: Values without units specified are dimensionless constants.
Table 1 Table 1: Default RFD Parameters of Juniper and Cisco
4. Suppress Threshold Versus Churn 4. Suppress Threshold versus Churn
By turning RFD back on with the values recommended in Section 6 churn By turning RFD back on with the values recommended in Section 6,
is reduced. Moreover, with these values, prefixes going through churn is reduced. Moreover, with these values, prefixes going
normal convergence are generally not damped. through normal convergence are generally not damped.
[pelsser2011] estimates that, with a suppress threshold of 6,000, the [PELSSER2011] estimates that, with a suppress threshold of 6,000, the
BGP update rate is reduced by 19% compared to a situation without RFD BGP update rate is reduced by 19% compared to a situation without RFD
enabled. With this 6,000 suppress threshold, 90% fewer prefixes are enabled. [PELSSER2011] studies the number of prefixes damped over a
damped compared to use of a 2,000 threshold. I.e. far fewer well- week between September 29, 2010 and October 6, 2010. With this 6,000
behaved prefixes are damped. suppress threshold, 90% fewer prefixes are damped compared to use of
a 2,000 threshold. That is, far fewer well-behaved prefixes are
damped.
Setting the suppress threshold to 12,000 leads to very few damped Setting the suppress threshold to 12,000 leads to very few damped
prefixes (1.7% of the prefixes damped with a threshold of 2,000, in prefixes (0.22% of the prefixes were damped with a threshold of
the experiments in [pelsser2011] yielding an average hourly update 12,000 in the experiments in [PELSSER2011], yielding an average
reduction of 11% compared to not using RFD. hourly update reduction of 11% compared to not using RFD).
+-----------------+-----------------+-------------+-----------------+ +---------------+-------------+--------------+----------------------+
| Suppress | Damped | % of Table | Update Rate | | Suppress | Damped | % of Table | Update Rate (one- |
| Threshold | Instances | Damped | (one hour bins) | | Threshold | Prefixes | Damped | hour bins) |
+-----------------+-----------------+-------------+-----------------+ +---------------+-------------+--------------+----------------------+
| 2,000 | 43342 | 13.16% | 53.11% | | 2,000 | 43,342 | 13.16% | 53.11% |
| 4,000 | 11253 | 3.42% | 74.16% | | 4,000 | 11,253 | 3.42% | 74.16% |
| 6,000 | 4352 | 1.32% | 81.03% | | 6,000 | 4,352 | 1.32% | 81.03% |
| 8,000 | 2104 | 0.64% | 84.85% | | 8,000 | 2,104 | 0.64% | 84.85% |
| 10,000 | 1286 | 0.39% | 87.12% | | 10,000 | 1,286 | 0.39% | 87.12% |
| 12,000 | 720 | 0.22% | 88.74% | | 12,000 | 720 | 0.22% | 88.74% |
| 14,000 | 504 | 0.15% | 89.97% | | 14,000 | 504 | 0.15% | 89.97% |
| 16,000 | 353 | 0.11% | 91.01% | | 16,000 | 353 | 0.11% | 91.01% |
| 18,000 | 311 | 0.09% | 91.88% | | 18,000 | 311 | 0.09% | 91.88% |
| 20,000 | 261 | 0.08% | 92.69% | | 20,000 | 261 | 0.08% | 92.69% |
+-----------------+-----------------+-------------+-----------------+ +---------------+-------------+--------------+----------------------+
Damped Prefixes vs. Churn, from [pelsser2011]. Note overly- Note: the current default Suppress Threshold (2,000) is overly
aggressive current default Suppress Threshold agressive.
Table 2 Table 2: Damped Prefixes vs. Churn, from [PELSSER2011]
5. Maximum Penalty 5. Maximum Penalty
It is important to understand that the parameters shown in Table 1, It is important to understand that the parameters shown in Table 1
and the implementation's sampling rate, impose an upper bound on the and the implementation's sampling rate impose an upper bound on the
penalty value, which we can call the 'computed maximum penalty'. penalty value, which we can call the 'computed maximum penalty'.
In addition, BGP implementations have an internal constant which we In addition, BGP implementations have an internal constant, which we
will call the 'maximum penalty' which the current computed penalty will call the 'maximum penalty', and the current computed penalty may
may not exceed. not exceed it.
6. Recommendations 6. Recommendations
Use of the following values is recommended: Use of the following values is recommended:
Router Maximum Penalty: The internal constant for the maximum Router Maximum Penalty: The internal constant for the maximum
penalty value MUST be raised to at least 50,000. penalty value MUST be raised to at least 50,000.
Default Configurable Parameters: In order not to break existing Default Configurable Parameters: In order not to break existing
operational configurations, existing BGP implementations operational configurations, existing BGP implementations,
including, the examples in Table 1, SHOULD NOT change their including the examples in Table 1, SHOULD NOT change their default
default values. values.
Minimum Suppress Threshold: Operators wishing damping which is much Minimum Suppress Threshold: Operators that want damping that is much
less destructive than current, but still somewhat aggressive less destructive than the current damping, but still somewhat
SHOULD configure the Suppress Threshold to no less than 6,000. aggressive, SHOULD configure the Suppress Threshold to no less
than 6,000.
Conservative Suppress Threshold: Conservative operators SHOULD Conservative Suppress Threshold: Conservative operators SHOULD
configure the Suppress Threshold to no less than 12,000. configure the Suppress Threshold to no less than 12,000.
Calculate But Do Not Damp: Implementations MAY have a test mode Calculate But Do Not Damp: Implementations MAY have a test mode
where the operator could see the results of a particular where the operator can see the results of a particular
configuration without actually damping any prefixes. This will configuration without actually damping any prefixes. This will
allow for fine tuning of parameters without losing reachability. allow for fine-tuning of parameters without losing reachability.
7. Security Considerations 7. Security Considerations
It is well known that an attacker can generate false flapping to It is well known that an attacker can generate false flapping to
cause a victim's prefix(es) to be damped. cause a victim's prefix(es) to be damped.
As the recommendations merely change parameters to more conservative As the recommendations merely change parameters to more conservative
values, there should be no increase in risk. values, there should be no increase in risk. In fact, the parameter
change to more conservative values should slightly mitigate the
In fact, the parameter change to more conservative values should false-flap attack.
slightly mitigate the false flap attack.
8. IANA Considerations
This document has no IANA Considerations.
9. Acknowledgments 8. Acknowledgments
Nate Kushman initiated this work some years ago. Ron Bonica, Seiichi Nate Kushman initiated this work some years ago. Ron Bonica, Seiichi
Kawamura, and Erik Muller contributed useful suggestions. Kawamura, and Erik Muller contributed useful suggestions.
10. References 9. References
10.1. Normative References 9.1. Normative References
[MAO2002] Mao, Z., Govidan, R., Varghese, G., and R. Katz, "Route
Flap Damping Exacerbates Internet Routing Convergence", In
Proceedings of SIGCOMM, August 2002,
<http://conferences.sigcomm.org/sigcomm/2002/papers/
routedampening.pdf>.
[PELSSER2011]
Pelsser, C., Maennel, O., Mohapatra, P., Bush, R., and K.
Patel, "Route Flap Damping Made Usable", PAM 2011: Passive
and Active Measurement Conference, March 2011,
<http://pam2011.gatech.edu/papers/pam2011--Pelsser.pdf>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2439] Villamizar, C., Chandra, R., and R. Govindan, "BGP Route [RFC2439] Villamizar, C., Chandra, R., and R. Govindan, "BGP Route
Flap Damping", RFC 2439, November 1998. Flap Damping", RFC 2439, November 1998.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006. Protocol 4 (BGP-4)", RFC 4271, January 2006.
[mao2002] Mao, Z. M., Govidan, R., Varghese, G., Katz, R., "Route [RIPE378] Smith, P. and P. Panigl, "RIPE Routing Working Group
Flap Damping Excacerbates Internet Routing Convergence", Recommendations On Route-flap Damping", RIPE 378, May
In Proceedings of SIGCOMM , August 2002, <http:// 2006, <http://www.ripe.net/ripe/docs/ripe-378>.
conferences.sigcomm.org/sigcomm/2002/papers/
routedampening.pdf>.
[pelsser2011]
Pelsser, C., Maennel, O., Mohapatra, P., Bush, R., Patel,
K., "Route Flap Damping Made Usable", Passive and Active
Measurement (PAM), March 2011,
<http://pam2011.gatech.edu/papers/pam2011--Pelsser.pdf>.
[ripe378] Panigl, P. Smith, P., "RIPE Routing Working Group 9.2. Informative References
Recommendations On Route-flap Damping", 2006,
<http://www.ripe.net/ripe/docs/ripe-378>.
10.2. Informative References [HUSTON2006]
Huston, G., "2005 - A BGP Year in Review", RIPE 52, 2006,
<http://meetings.ripe.net/ripe-52/presentations/
ripe52-plenary-bgp-review.pdf>.
[I-D.shishio-grow-isp-rfd-implement-survey] [RFD-SURVEY]
Tsuchiya, S., Kawamura, S., Bush, R., and C. Pelsser, Tsuchiya, S., Kawamura, S., Bush, R., and C. Pelsser,
"Route Flap Damping Deployment Status Survey", draft- "Route Flap Damping Deployment Status Survey", Work in
shishio-grow-isp-rfd-implement-survey-05 (work in Progress, June 2012.
progress), June 2012.
[huston2006]
Huston, G., "BGP Extreme Routing Noise", RIPE 52 , 2006,
<http://meetings.ripe.net/ripe-52/presentations/ripe52
-plenary-bgp-review.pdf>.
[ripe178] Barber, T., Doran, S., Karrenberg, D., Panigl, C., [RIPE178] Barber, T., Doran, S., Karrenberg, D., Panigl, C., and J.
Schmitz, J., "RIPE Routing-WG Recommendation for Schmitz, "RIPE Routing-WG Recommendation for Coordinated
Coordinated Route-flap Damping Parameters", 2001, Route-flap Damping Parameters", RIPE 178, February 1998,
<http://www.ripe.net/ripe/docs/ripe-178>. <http://www.ripe.net/ripe/docs/ripe-178>.
[ripe580] Pelsser, C., Bush, R., Maennel, O., Patel, K., Mohapatra, [RIPE580] Bush, R., Pelsser, C., Kuhne, M., Maennel, O., Mohapatra,
P., Kuhne, M., Evans, R., "RIPE Routing-WG Recommendation P., Patel, K., and R. Evans, "RIPE Routing Working Group
for Route-flap Damping", 2013, Recommendation for Route Flap Damping", RIPE 580, January
<http://www.ripe.net/ripe/docs/ripe-580>. 2013, <http://www.ripe.net/ripe/docs/ripe-580>.
Authors' Addresses Authors' Addresses
Cristel Pelsser Cristel Pelsser
Internet Initiative Japan Internet Initiative Japan
Jinbocho Mitsui Buiding, 1-105 Jinbocho Mitsui Buiding, 1-105
Kanda-Jinbocho, Chiyoda-ku, Tokyo 101-0051 Kanda-Jinbocho, Chiyoda-ku, Tokyo 101-0051
JP JP
Phone: +81 3 5205 6464 Phone: +81 3 5205 6464
Email: cristel@iij.ad.jp EMail: cristel@iij.ad.jp
Randy Bush Randy Bush
Internet Initiative Japan Internet Initiative Japan
5147 Crystal Springs 5147 Crystal Springs
Bainbridge Island, Washington 98110 Bainbridge Island, Washington 98110
US US
Email: randy@psg.com EMail: randy@psg.com
Keyur Patel Keyur Patel
Cisco Systems Cisco Systems
170 W. Tasman Drive 170 W. Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
US US
Email: keyupate@cisco.com EMail: keyupate@cisco.com
Pradosh Mohapatra Pradosh Mohapatra
Cumulus Systems, Inc. Sproute Networks
2672 Bayshore Parkway, Suite 515 41529 Higgins Way
Mountain View, CA 94043 Fremont, CA 94539
US US
Email: pmohapat@cumulusnetworks.com EMail: mpradosh@yahoo.com
Olaf Maennel Olaf Maennel
Loughborough University Loughborough University
Department of Computer Science - N.2.03 Department of Computer Science - N.2.03
Loughborough Loughborough
UK UK
Phone: +44 115 714 0042 Phone: +44 115 714 0042
Email: o@maennel.net EMail: o@maennel.net
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