draft-ietf-grow-bgp-med-considerations-01.txt   draft-ietf-grow-bgp-med-considerations-02.txt 
INTERNET-DRAFT Danny McPherson INTERNET-DRAFT Danny McPherson
Arbor Networks, Inc. Arbor Networks, Inc.
Vijay Gill Vijay Gill
AOL AOL
Category Informational Category Informational
Expires: November 2004 May 2004 Expires: January 2005 July 2004
BGP MED Considerations BGP MED Considerations
<draft-ietf-grow-bgp-med-considerations-01.txt> <draft-ietf-grow-bgp-med-considerations-02.txt>
Status of this Document Status of this Document
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
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"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC 2119]. document are to be interpreted as described in RFC 2119 [RFC 2119].
This document is a product of an individual. Comments are solicited This document is a product of an individual. Comments are solicited
and should be addressed to the author(s). and should be addressed to the author(s).
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved. Copyright (C) The Internet Society (2004). All Rights Reserved.
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Abstract Abstract
The BGP MED attribute provides a mechanism for BGP speakers to convey The BGP MED attribute provides a mechanism for BGP speakers to convey
to an adjacent AS the optimal entry point into the local AS. While to an adjacent AS the optimal entry point into the local AS. While
BGP MEDs function correctly in many scenarios, there are a number of BGP MEDs function correctly in many scenarios, there are a number of
issues which may arise when utilizing MEDs in dynamic or complex issues which may arise when utilizing MEDs in dynamic or complex
topologies. topologies.
This document discusses implementation and deployment considerations This document discusses implementation and deployment considerations
regarding BGP MEDs and provides information which implementors and regarding BGP MEDs and provides information which implementors and
network operators should be familiar with. network operators should be familiar with.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. About the MULTI_EXIT_DISC (MED) Attribute . . . . . . . . . 4 1.1. About the MULTI_EXIT_DISC (MED) Attribute . . . . . . . . . 4
1.2. MEDs and Potatoes . . . . . . . . . . . . . . . . . . . . . 5 1.2. MEDs and Potatoes . . . . . . . . . . . . . . . . . . . . . 5
2. Implementation and Protocol Considerations . . . . . . . . . . 7 2. Implementation and Protocol Considerations . . . . . . . . . . 6
2.1. MULTI_EXIT_DISC is a Optional Non-Transitive 2.1. MULTI_EXIT_DISC is a Optional Non-Transitive
Attribute. . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Attribute. . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2. MED Values and Preferences. . . . . . . . . . . . . . . . . 7 2.2. MED Values and Preferences. . . . . . . . . . . . . . . . . 7
2.3. Comparing MEDs Between Different Autonomous 2.3. Comparing MEDs Between Different Autonomous
Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.4. MEDs, Route Reflection and AS Confederations 2.4. MEDs, Route Reflection and AS Confederations
for BGP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 for BGP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.5. Route Flap Damping and MED Churn. . . . . . . . . . . . . . 9 2.5. Route Flap Damping and MED Churn. . . . . . . . . . . . . . 9
2.6. Effects of MEDs on Update Packing Efficiency. . . . . . . . 10 2.6. Effects of MEDs on Update Packing Efficiency. . . . . . . . 9
2.7. Temporal Route Selection. . . . . . . . . . . . . . . . . . 10 2.7. Temporal Route Selection. . . . . . . . . . . . . . . . . . 10
3. Deployment Considerations. . . . . . . . . . . . . . . . . . . 11 3. Deployment Considerations. . . . . . . . . . . . . . . . . . . 10
3.1. Comparing MEDs Between Different Autonomous 3.1. Comparing MEDs Between Different Autonomous
Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.2. Effects of Aggregation on MEDs` . . . . . . . . . . . . . . 12 3.2. Effects of Aggregation on MEDs` . . . . . . . . . . . . . . 11
4. Security Considerations. . . . . . . . . . . . . . . . . . . . 12 4. Security Considerations. . . . . . . . . . . . . . . . . . . . 12
4.1. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 12 4.1. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 12
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 13 6. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 13
7. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 13 7. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 13
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1. Introduction 1. Introduction
The BGP MED attribute provides a mechanism for BGP speakers to convey The BGP MED attribute provides a mechanism for BGP speakers to convey
to an adjacent AS the optimal entry point into the local AS. While to an adjacent AS the optimal entry point into the local AS. While
BGP MEDs function correctly in many scenarios, there are a number of BGP MEDs function correctly in many scenarios, there are a number of
issues which may arise when utilizing MEDs in dynamic or complex issues which may arise when utilizing MEDs in dynamic or complex
topologies. topologies.
This document discusses implementation and deployment considerations This document discusses implementation and deployment considerations
regarding BGP MEDs and provides information which implementors and regarding BGP MEDs and provides information which implementors and
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An implementation MAY also (based on local configuration) alter the An implementation MAY also (based on local configuration) alter the
value of the MULTI_EXIT_DISC attribute received over EBGP. This value of the MULTI_EXIT_DISC attribute received over EBGP. This
MAY be done prior to determining the degree of preference of the MAY be done prior to determining the degree of preference of the
route and performing route selection (decision process phases 1 and route and performing route selection (decision process phases 1 and
2). 2).
Section 9.1.2.2 (c) of [BGP4] defines the following route selection Section 9.1.2.2 (c) of [BGP4] defines the following route selection
criteria regarding MEDs: criteria regarding MEDs:
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Remove from consideration routes with less-preferred Remove from consideration routes with less-preferred
MULTI_EXIT_DISC attributes. MULTI_EXIT_DISC is only comparable MULTI_EXIT_DISC attributes. MULTI_EXIT_DISC is only comparable
between routes learned from the same neighboring AS (the between routes learned from the same neighboring AS (the
neighboring AS is determined from the AS_PATH attribute). Routes neighboring AS is determined from the AS_PATH attribute). Routes
which do not have the MULTI_EXIT_DISC attribute are considered to which do not have the MULTI_EXIT_DISC attribute are considered to
have the lowest possible MULTI_EXIT_DISC value. have the lowest possible MULTI_EXIT_DISC value.
This is also described in the following procedure: This is also described in the following procedure:
for m =3D all routes still under consideration for m = all routes still under consideration
for n =3D all routes still under consideration for n = all routes still under consideration
if (neighborAS(m) =3D=3D neighborAS(n)) and (MED(n) < MED(m)) if (neighborAS(m) == neighborAS(n)) and (MED(n) < MED(m))
remove route m from consideration remove route m from consideration
In the pseudo-code above, MED(n) is a function which returns the In the pseudo-code above, MED(n) is a function which returns the
value of route n's MULTI_EXIT_DISC attribute. If route n has no value of route n's MULTI_EXIT_DISC attribute. If route n has no
MULTI_EXIT_DISC attribute, the function returns the lowest possible MULTI_EXIT_DISC attribute, the function returns the lowest possible
MULTI_EXIT_DISC value, i.e. 0. MULTI_EXIT_DISC value, i.e. 0.
If a MULTI_EXIT_DISC attribute is removed before re- advertising a If a MULTI_EXIT_DISC attribute is removed before re- advertising a
route into IBGP, then comparison based on the received EBGP route into IBGP, then comparison based on the received EBGP
MULTI_EXIT_DISC attribute MAY still be performed. If an MULTI_EXIT_DISC attribute MAY still be performed. If an
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to cause route loops. to cause route loops.
Routes that have different MULTI_EXIT_DISC attribute SHALL NOT be Routes that have different MULTI_EXIT_DISC attribute SHALL NOT be
aggregated. aggregated.
1.2. MEDs and Potatoes 1.2. MEDs and Potatoes
In a situation where traffic flows between a pair of hosts, each In a situation where traffic flows between a pair of hosts, each
connected to different transit networks, which are themselves connected to different transit networks, which are themselves
interconnected at two or more locations, each transit network has the interconnected at two or more locations, each transit network has the
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choice of either sending traffic to the closest peering to the choice of either sending traffic to the closest peering to the
adjacent transit network or passing traffic to the interconnection adjacent transit network or passing traffic to the interconnection
location which advertises the least cost path to the destination location which advertises the least cost path to the destination
host. host.
DIAGRAM***
The former method is called "hot potato routing" (or closest-exit) The former method is called "hot potato routing" (or closest-exit)
because like a hot potato held in bare hands, whoever has it tries to because like a hot potato held in bare hands, whoever has it tries to
get rid of it quickly. Hot potato routing is accomplished by not get rid of it quickly. Hot potato routing is accomplished by not
passing the EGBP learned MED into IBGP. This minimizes transit passing the EGBP learned MED into IBGP. This minimizes transit
traffic for the provider routing the traffic. Far less common is traffic for the provider routing the traffic. Far less common is
"cold potato routing" (or best-exit) where the transit provider uses "cold potato routing" (or best-exit) where the transit provider uses
their own transit capacity to get the traffic to the point that their own transit capacity to get the traffic to the point that
adjacent transit provider advertised as being closest to the adjacent transit provider advertised as being closest to the
destination. Cold potato routing is accomplished by passing the EBGP destination. Cold potato routing is accomplished by passing the EBGP
learned MED into IBGP. learned MED into IBGP.
DIAGRAMS***
If one transit provider uses hot potato routing and another uses cold If one transit provider uses hot potato routing and another uses cold
potato, traffic between the two tends to be more symmetric. potato, traffic between the two tends to be more symmetric.
Depending on the business relationships, if one provider has more Depending on the business relationships, if one provider has more
capacity or a significantly less congested backbone network, then capacity or a significantly less congested backbone network, then
that provider may use cold potato routing. An example of widespread that provider may use cold potato routing. An example of widespread
use of cold potato routing was the NSF funded NSFNET backbone and NSF use of cold potato routing was the NSF funded NSFNET backbone and NSF
funded regional networks in the mid 1990s. funded regional networks in the mid 1990s.
In some cases a provider may use hot potato routing for some In some cases a provider may use hot potato routing for some
destinations for a given peer AS and cold potato routing for others. destinations for a given peer AS and cold potato routing for others.
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commercial networks exchange MEDs with customers but not bilateral commercial networks exchange MEDs with customers but not bilateral
peers. However, commercial use of MEDs varies widely, from peers. However, commercial use of MEDs varies widely, from
ubiquitous use of MEDs to no use of MEDs at all. ubiquitous use of MEDs to no use of MEDs at all.
In addition, many deployments of MEDs today are likely behaving In addition, many deployments of MEDs today are likely behaving
differently (e.g., resulting is sub-optimal routing) than the network differently (e.g., resulting is sub-optimal routing) than the network
operator intended, thereby resulting not in hot or cold potatoes, but operator intended, thereby resulting not in hot or cold potatoes, but
mashed potatoes! More information on unintended behavior resulting mashed potatoes! More information on unintended behavior resulting
from MEDs is provided throughout this document. from MEDs is provided throughout this document.
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2. Implementation and Protocol Considerations 2. Implementation and Protocol Considerations
There are a number of implementation and protocol peculiarities There are a number of implementation and protocol peculiarities
relating to MEDs that have been discovered that may affect network relating to MEDs that have been discovered that may affect network
behavior. The following sections provide information on these behavior. The following sections provide information on these
issues. issues.
2.1. MULTI_EXIT_DISC is a Optional Non-Transitive Attribute 2.1. MULTI_EXIT_DISC is a Optional Non-Transitive Attribute
MULTI_EXIT_DISC is a non-transitive optional attribute whose MULTI_EXIT_DISC is a non-transitive optional attribute whose
advertisement to both IBGP and EBGP peers is discretionary. As a advertisement to both IBGP and EBGP peers is discretionary. As a
result, some implementations enable sending of MEDs to IBGP peers by result, some implementations enable sending of MEDs to IBGP peers by
default, while others do not. This behavior may result in sub- default, while others do not. This behavior may result in sub-
optimal route selection within an AS. In addition, some optimal route selection within an AS. In addition, some
implementations send MEDs to EBGP peers by default, while others do implementations send MEDs to EBGP peers by default, while others do
not. This behavior may result in sub-optimal inter-domain route not. This behavior may result in sub-optimal inter-domain route
selection. selection.
DIAGRAM and MORE TEXT***
2.2. MED Values and Preferences 2.2. MED Values and Preferences
Some implementations consider an MED value of zero as less preferable Some implementations consider an MED value of zero as less preferable
than no MED value. This behavior resulted in path selection than no MED value. This behavior resulted in path selection
inconsistencies within an AS. The current draft version of the BGP inconsistencies within an AS. The current draft version of the BGP
specification [BGP4] removes ambiguities that existed in [RFC 1771] specification [BGP4] removes ambiguities that existed in [RFC 1771]
by stating that if route n has no MULTI_EXIT_DISC attribute, the by stating that if route n has no MULTI_EXIT_DISC attribute, the
lowest possible MULTI_EXIT_DISC value (i.e. 0) should be assigned to lowest possible MULTI_EXIT_DISC value (i.e. 0) should be assigned to
the attribute. the attribute.
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of the BGP draft specification have been all over the map with of the BGP draft specification have been all over the map with
interpretation of missing-MED. For example, earlier versions of the interpretation of missing-MED. For example, earlier versions of the
specification called for a missing MED to be assigned the highest specification called for a missing MED to be assigned the highest
possible MED value (i.e., 2^32-1). possible MED value (i.e., 2^32-1).
In addition, some implementations have been shown to internally In addition, some implementations have been shown to internally
employ a maximum possible MED value (2^32-1) as an "infinity" metric employ a maximum possible MED value (2^32-1) as an "infinity" metric
(i.e., the MED value is used to tag routes as unfeasible), and would (i.e., the MED value is used to tag routes as unfeasible), and would
upon on receiving an update with an MED value of 2^32-1 rewrite the upon on receiving an update with an MED value of 2^32-1 rewrite the
value to 2^32-2. Subsequently, the new MED value would be propagated value to 2^32-2. Subsequently, the new MED value would be propagated
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and could result in routing inconsistencies or unintended path and could result in routing inconsistencies or unintended path
selections. selections.
As a result of implementation inconsistencies and protocol revision As a result of implementation inconsistencies and protocol revision
variances, many network operators today explicitly reset all MED variances, many network operators today explicitly reset all MED
values on ingress to conform to their internal routing policies values on ingress to conform to their internal routing policies
(i.e., to include policy that requires that MED values of 0 and (i.e., to include policy that requires that MED values of 0 and
2^32-1 NOT be used in configurations, whether the MEDs are directly 2^32-1 NOT be used in configurations, whether the MEDs are directly
computed or configured), so as to not have to rely on all their computed or configured), so as to not have to rely on all their
routers having the same missing-MED behavior. routers having the same missing-MED behavior.
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introduce persistent BGP route oscillation [RFC 3345]. The problem introduce persistent BGP route oscillation [RFC 3345]. The problem
is inherent in the way BGP works: a conflict exists between is inherent in the way BGP works: a conflict exists between
information hiding/hierarchy and the non-hierarchical selection information hiding/hierarchy and the non-hierarchical selection
process imposed by lack of total ordering caused by the MED rules. process imposed by lack of total ordering caused by the MED rules.
Given current practices, we see the problem most frequently manifest Given current practices, we see the problem most frequently manifest
itself in the context of MED + route reflectors or confederations. itself in the context of MED + route reflectors or confederations.
One potential way to avoid this is by configuring inter-Member-AS or One potential way to avoid this is by configuring inter-Member-AS or
inter-cluster IGP metrics higher than intra-Member-AS IGP metrics inter-cluster IGP metrics higher than intra-Member-AS IGP metrics
and/or using other tie breaking policies to avoid BGP route selection and/or using other tie breaking policies to avoid BGP route selection
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based on incomparable MEDs. Of course, IGP metric constraints may be based on incomparable MEDs. Of course, IGP metric constraints may be
unreasonably onerous for some applications. unreasonably onerous for some applications.
Comparing MEDs between differing adjacent autonomous systems (which Comparing MEDs between differing adjacent autonomous systems (which
will be discussed in later sections), or not utilizing MEDs at all, will be discussed in later sections), or not utilizing MEDs at all,
significantly decreases the probability of introducing potential significantly decreases the probability of introducing potential
route oscillation conditions into the network. route oscillation conditions into the network.
Although perhaps "legal" as far as current specifications are Although perhaps "legal" as far as current specifications are
concerned, modifying MED attributes received on any type of IBGP concerned, modifying MED attributes received on any type of IBGP
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dampening behavior because it many cause routes to be re- advertised dampening behavior because it many cause routes to be re- advertised
solely to reflect an internal topology change. solely to reflect an internal topology change.
Many implementations don't have a practical problem with IGP Many implementations don't have a practical problem with IGP
flapping, they either latch their IGP metric upon first advertisement flapping, they either latch their IGP metric upon first advertisement
or they employ some internal suppression mechanism. Some or they employ some internal suppression mechanism. Some
implementations regard BGP attribute changes as less significant than implementations regard BGP attribute changes as less significant than
route withdrawals and announcements to attempt to mitigate the impact route withdrawals and announcements to attempt to mitigate the impact
of this type of event. of this type of event.
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2.6. Effects of MEDs on Update Packing Efficiency 2.6. Effects of MEDs on Update Packing Efficiency
Multiple unfeasible routes can be advertised in a single BGP Update Multiple unfeasible routes can be advertised in a single BGP Update
message. In addition, one or more feasible routes can be advertised message. In addition, one or more feasible routes can be advertised
in a single Update message so long as all prefixes share a common in a single Update message so long as all prefixes share a common
attribute set. attribute set.
The BGP4 protocol permits advertisement of multiple prefixes with a The BGP4 protocol permits advertisement of multiple prefixes with a
common set of path attributes to be advertised in a single update common set of path attributes to be advertised in a single update
message, this is commonly referred to as "update packing". When message, this is commonly referred to as "update packing". When
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MED-based best path selection. These usually involved methods used MED-based best path selection. These usually involved methods used
to store the oldest route along with ordering routes for MED in to store the oldest route along with ordering routes for MED in
earlier implementations that cause non-deterministic behavior on earlier implementations that cause non-deterministic behavior on
whether the oldest route would truly be selected or not. whether the oldest route would truly be selected or not.
The reasoning for this is that "older" paths are presumably more The reasoning for this is that "older" paths are presumably more
stable, and thus more preferable. However, temporal behavior in stable, and thus more preferable. However, temporal behavior in
route selection results in non-deterministic behavior, and as such, route selection results in non-deterministic behavior, and as such,
is often undesirable. is often undesirable.
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3. Deployment Considerations 3. Deployment Considerations
Empirical data [MFN/Ixia Monitoring Project] has shown that accepting Empirical data [MFN/Ixia Monitoring Project] has shown that accepting
MEDs from other autonomous systems have the potential to cause MEDs from other autonomous systems have the potential to cause
traffic flow churns in the network. Some implementations only traffic flow churns in the network. Some implementations only
ratchet down the MED and never move it back up to prevent excessive ratchet down the MED and never move it back up to prevent excessive
churn. churn.
However, if that session is reset, the MEDs being advertised have the However, if that session is reset, the MEDs being advertised have the
potential of changing. If an network is relying on received MEDs to potential of changing. If an network is relying on received MEDs to
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This allows MEDs to reasonably reflect IGP topologies when This allows MEDs to reasonably reflect IGP topologies when
advertising routes to peers. While this is fine when comparing MEDs advertising routes to peers. While this is fine when comparing MEDs
between multiple paths learned from a single AS, it can result in between multiple paths learned from a single AS, it can result in
potentially "weighted" decisions when comparing MEDs between potentially "weighted" decisions when comparing MEDs between
different autonomous systems. This is most typically the case when different autonomous systems. This is most typically the case when
the autonomous systems use different mechanisms to derive IGP the autonomous systems use different mechanisms to derive IGP
metrics, BGP MEDs, or perhaps even use different IGP protocols with metrics, BGP MEDs, or perhaps even use different IGP protocols with
vastly contrasting metric spaces (e.g., OSPF v. traditional metric vastly contrasting metric spaces (e.g., OSPF v. traditional metric
space in IS-IS). space in IS-IS).
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3.2. Effects of Aggregation on MEDs` 3.2. Effects of Aggregation on MEDs`
Another MED deployment consideration involves the impact that Another MED deployment consideration involves the impact that
aggregation of BGP routing information has on MEDs. Aggregates are aggregation of BGP routing information has on MEDs. Aggregates are
often generated from multiple locations in an AS in order to often generated from multiple locations in an AS in order to
accommodate stability, redundancy and other network design goals. accommodate stability, redundancy and other network design goals.
When MEDs are derived from IGP metrics associated with said When MEDs are derived from IGP metrics associated with said
aggregates the MED value advertised to peers can result in very aggregates the MED value advertised to peers can result in very
suboptimal routing. suboptimal routing.
DIAGRAM AND EXPAND***
4. Security Considerations 4. Security Considerations
The MED was purposely designed to be a "weak" metric that would only The MED was purposely designed to be a "weak" metric that would only
be used late in the best-path decision process. The BGP working be used late in the best-path decision process. The BGP working
group was concerned that any metric specified by a remote operator group was concerned that any metric specified by a remote operator
would only affect routing in a local AS IF no other preference was would only affect routing in a local AS IF no other preference was
specified. A paramount goal of the design of the MED was to ensure specified. A paramount goal of the design of the MED was to ensure
that peers could not "shed" or "absorb" traffic for networks that that peers could not "shed" or "absorb" traffic for networks that
they advertise. As such, accepting MEDs from peers may in some sense they advertise. As such, accepting MEDs from peers may in some sense
increase a network's susceptibility to exploitation by peers. increase a network's susceptibility to exploitation by peers.
4.1. Acknowledgments 4.1. Acknowledgments
Thanks to John Scudder for applying his usual keen eye and Thanks to John Scudder for applying his usual keen eye and
constructive insight. Also, thanks to Curtis Villamizar and JR constructive insight. Also, thanks to Curtis Villamizar and JR
Mitchell. Mitchell.
Others to be supplied. Others to be supplied.
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5. References 5. References
[RFC 1519] Fuller, V., Li. T., Yu J., and K. Varadhan, "Classless [RFC 1519] Fuller, V., Li. T., Yu J., and K. Varadhan, "Classless
Inter-Domain Routing (CIDR): an Address Assignment and Inter-Domain Routing (CIDR): an Address Assignment and
Aggregation Strategy", RFC 1519, September 1993. Aggregation Strategy", RFC 1519, September 1993.
[RFC 1771] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4 [RFC 1771] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4
(BGP-4)", RFC 1771, March 1995. (BGP-4)", RFC 1771, March 1995.
[RFC 2439] Villamizar, C. and Chandra, R., "BGP Route Flap Damping", [RFC 2439] Villamizar, C. and Chandra, R., "BGP Route Flap Damping",
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[RFC 3065] Traina, P., McPherson, D., Scudder, J.. "Autonomous System [RFC 3065] Traina, P., McPherson, D., Scudder, J.. "Autonomous System
Confederations for BGP", RFC 3065, February 2001. Confederations for BGP", RFC 3065, February 2001.
[RFC 3345] McPherson, D., Gill, V., Walton, D., and Retana, A, "BGP [RFC 3345] McPherson, D., Gill, V., Walton, D., and Retana, A, "BGP
Persistent Route Oscillation Condition", RFC 3345, Persistent Route Oscillation Condition", RFC 3345,
August 2002. August 2002.
[BGP4] Rekhter, Y., T. Li., and Hares. S, Editors, "A Border [BGP4] Rekhter, Y., T. Li., and Hares. S, Editors, "A Border
Gateway Protocol 4 (BGP-4)", BGP Draft, Work in Progress. Gateway Protocol 4 (BGP-4)", BGP Draft, Work in Progress.
[MFN/Ixia Monitoring Project] Vijay to Provide. [MFN/Ixia Monitoring Project] Vijay to Provide Pointer.
6. Authors' Addresses 6. Authors' Addresses
Danny McPherson Danny McPherson
Arbor Networks Arbor Networks
Email: danny@arbor.net Email: danny@arbor.net
Vijay Gill Vijay Gill
AOL AOL
Email: VijayGill9@aol.com Email: VijayGill9@aol.com
7. Full Copyright Statement 7. Full Copyright Statement
Copyright (C) The Internet Society (2004). All Rights Reserved. Copyright (C) The Internet Society (2004). All Rights Reserved.
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This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for developing Internet standards in which case the procedures for
 End of changes. 

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