wdiff rfc7454.original rfc7454.txt

Internet Engineering Task Force (IETF) J. Durand
Internet-Draft CISCO
Request for Comments: 7454 Cisco Systems, Inc.
Intended status:
BCP: 194 I. Pepelnjak
Category: Best Current Practice I. Pepelnjak
Expires: June 2, 2015 NIL
ISSN: 2070-1721 G. Doering
SpaceNet
December 2, 2014
February 2015

BGP operations Operations and security
draft-ietf-opsec-bgp-security-07.txt Security

Abstract

BGP (Border

The Border Gateway Protocol) Protocol (BGP) is the protocol almost exclusively
used in the Internet to exchange routing information between network
domains. Due to this central nature, it is important to understand
the security measures that can and should be deployed to prevent
accidental or intentional routing disturbances.

This document describes measures to protect the BGP sessions itself
(like TTL, TCP-AO, control plane filtering)
such as Time to Live (TTL), the TCP Authentication Option (TCP-AO),
and control-plane filtering. It also describes measures to better
control the flow of routing information, using prefix filtering and
automatization
automation of prefix filters, max-prefix filtering, AS Autonomous System
(AS) path filtering, route flap dampening dampening, and BGP community
scrubbing.

Requirements Language

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 [1].

Status of This Memo

This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working memo documents an Internet Best Current Practice.

This document is a product of the Internet Engineering Task Force
(IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list It represents the consensus of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid the IETF community. It has
received public review and has been approved for a maximum publication by the
Internet Engineering Steering Group (IESG). Further information on
BCPs is available in Section 2 of RFC 5741.

Information about the current status of six months this document, any errata,
and how to provide feedback on it may be updated, replaced, or obsoleted by other documents obtained at any
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material or to cite them other than as "work in progress."

This Internet-Draft will expire on May 29, 2015.
http://www.rfc-editor.org/info/rfc7454.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Scope of the document Document . . . . . . . . . . . . . . . . . . . . 3
3. Definitions and Accronyms Acronyms . . . . . . . . . . . . . . . . . . 4 3
4. Protection of the BGP speaker Speaker . . . . . . . . . . . . . . . . 4
5. Protection of BGP sessions Sessions . . . . . . . . . . . . . . . . . 5
5.1. Protection of TCP sessions used Sessions Used by BGP . . . . . . . . . 5
5.2. BGP TTL security Security (GTSM) . . . . . . . . . . . . . . . . . 6 5
6. Prefix filtering Filtering . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Definition of prefix filters Prefix Filters . . . . . . . . . . . . . . 6
6.1.1. Special purpose prefixes Special-Purpose Prefixes . . . . . . . . . . . . . . 6
6.1.2. Unallocated Prefixes not allocated . . . . . . . . . . . . . . . . 7
6.1.3. Prefixes too specific . . . . . That Are Too Specific . . . . . . . . . . . 11 10
6.1.4. Filtering prefixes belonging Prefixes Belonging
to the local Local AS and
downstreams
Downstreams . . . . . . . . . . . . . . . . . . . . . 11
6.1.5. IXP LAN prefixes Prefixes . . . . . . . . . . . . . . . . . . 11
6.1.6. The default route Default Route . . . . . . . . . . . . . . . . . . 12
6.2. Prefix filtering recommendations Filtering Recommendations in full routing networks Full Routing Networks 13
6.2.1. Filters with Internet peers Peers . . . . . . . . . . . . . 13
6.2.2. Filters with customers Customers . . . . . . . . . . . . . . . 15 14
6.2.3. Filters with upstream providers Upstream Providers . . . . . . . . . . . 15
6.3. Prefix filtering recommendations Filtering Recommendations for leaf networks Leaf Networks . . . 16
6.3.1. Inbound filtering Filtering . . . . . . . . . . . . . . . . . . 16
6.3.2. Outbound filtering Filtering . . . . . . . . . . . . . . . . . 16
7. BGP route flap dampening Route Flap Dampening . . . . . . . . . . . . . . . . . . 17 16
8. Maximum prefixes Prefixes on a peering Peering . . . . . . . . . . . . . . . . 17
9. AS-path filtering AS Path Filtering . . . . . . . . . . . . . . . . . . . . . . 17
10. Next-Hop Filtering . . . . . . . . . . . . . . . . . . . . . 19
11. BGP community scrubbing Community Scrubbing . . . . . . . . . . . . . . . . . . . 20 19
12. Change logs . . . . . . . . . . . . . . . . . . . . . . . . . 20
12.1. Diffs between draft-jdurand-bgp-security-01 and draft-
jdurand-bgp-security-00 . . . . . . . . . . . . . . . . 20
12.2. Diffs between draft-jdurand-bgp-security-02 and draft-
jdurand-bgp-security-01 . . . . . . . . . . . . . . . . 21
12.3. Diffs between draft-ietf-opsec-bgp-security-00 and
draft-jdurand-bgp-security-02 . . . . . . . . . . . . . 22
12.4. Diffs between draft-ietf-opsec-bgp-security-01 and
draft-ietf-opsec-bgp-security-00 . . . . . . . . . . . . 22
12.5. Diffs between draft-ietf-opsec-bgp-security-02 and
draft-ietf-opsec-bgp-security-01 . . . . . . . . . . . . 23
12.6. Diffs between draft-ietf-opsec-bgp-security-03 and
draft-ietf-opsec-bgp-security-02 . . . . . . . . . . . . 24
12.7. Diffs between draft-ietf-opsec-bgp-security-04 and
draft-ietf-opsec-bgp-security-03 . . . . . . . . . . . . 25
12.8. Diffs between draft-ietf-opsec-bgp-security-05 and
draft-ietf-opsec-bgp-security-04 . . . . . . . . . . . . 25
12.9. Diffs between draft-ietf-opsec-bgp-security-06 and
draft-ietf-opsec-bgp-security-05 . . . . . . . . . . . . 25
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
15. Security Considerations . . . . . . . . . . . . . . . . . . . 26
16. 20
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
16.1. 20
13.1. Normative References . . . . . . . . . . . . . . . . . . 27
16.2. 20
13.2. Informative References . . . . . . . . . . . . . . . . . 27 21
Appendix A. IXP LAN prefix filtering Prefix Filtering - example . Example . . . . . . . . 29
Authors' Addresses . . 24
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . . . . 30 24

1. Introduction

BGP (Border

The Border Gateway Protocol - (BGP), specified in RFC 4271 [2]) [2], is the
protocol used in the Internet to exchange routing information between
network domains. BGP does not directly include mechanisms that
control that whether the routes exchanged conform to the various
guidelines defined by the Internet community. This document intends
to both summarize common existing guidelines and help network
administrators apply coherent BGP policies.

1.1. Requirements Language

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 [1].

2. Scope of the document Document

The guidelines defined in this document are intended for generic
Internet BGP peerings. The nature of the Internet is such that
Autonomous Systems can always agree on exceptions to a common
framework for relevant local needs, and therefore configure a BGP
session in a manner that may differ from the recommendations provided
in this document. While this is perfectly acceptable, every
configured exception might have an impact on the entire inter-domain
routing environment environment, and network administrators SHOULD carefully
appraise this impact before implementation.

3. Definitions and Accronyms Acronyms

o ACL: Access Control List

o ASN: Autonomous System Number

o IRR: Internet Routing Registry

o IXP: Internet eXchange Exchange Point

o LIR: Local Internet Registry

o pMTUd: PMTUD: Path MTU Discovery

o RIR: Regional Internet Registry

o Tier 1 transit provider: an IP transit provider which that can reach any
network on the Internet without purchasing transit services services.

o uRPF: Unicast Reverse Path Forwarding
In addition to the list above, the following terms are used with a
specific meaning.

o Downstream: any network that is downstream; it can be a provider
or a customer network.

o Upstream: any network that is upstream.

4. Protection of the BGP speaker Speaker

The BGP speaker needs to be protected from attempts to subvert the
BGP session. This protection SHOULD be achieved by an Access Control
List (ACL) which that would discard all packets directed to TCP port 179 on
the local device and sourced from an address not known or permitted
to become a BGP neighbor. Experience has shown that the natural
protection TCP should offer is not always sufficient sufficient, as it is
sometimes run in control-plane software: in software. In the absence of ACLs ACLs, it
is possible to attack a BGP speaker by simply sending a high volume
of connection requests to it.

If supported, an ACL specific to the control-plane control plane of the router
SHOULD be used (receive-ACL, control-plane policing, etc.), to avoid
configuration of data-plane filters for packets transiting through
the router (and therefore not reaching the control plane). If the
hardware can not cannot do that, interface ACLs can be used to block packets
addressed to the local router.

Some routers automatically program such an ACL upon BGP
configuration. On other devices devices, this ACL should be configured and
maintained manually or using scripts.

In addition to strict filtering, rate-limiting MAY be configured for
accepted BGP traffic. Rate-limiting BGP traffic consists in
permitting only a certain quantity of bits per second (or packets per
second) of BGP traffic to the control plane. This protects the BGP
router control plane in case the amount of BGP traffic overcomes surpasses
platform capabilities.

Filtering and rate-limiting of control-plane traffic is a wider topic
than "just for BGP" (if BGP". (If a network administrator brings down a
router by overloading one of the other protocols from remote, remotely, BGP is
harmed as
well). well.) For a more detailed recommendation on how to
protect the router's control plane, see RFC 6192 [11].

5. Protection of BGP sessions Sessions

Current security issues of TCP-based protocols (therefore including
BGP) have been documented in RFC 6952 [14]. The following sub-
sections
subsections list the major points raised in this RFC and give the
best practices related to TCP session protection for BGP operation.

5.1. Protection of TCP sessions used Sessions Used by BGP

Attacks on TCP sessions used by BGP (aka BGP sessions), for example example,
sending spoofed TCP RST packets, could bring down a BGP peering.
Following a successful ARP spoofing attack (or other similar Man-in-
the-Middle man-in-
the-middle attack), the attacker might even be able to inject packets
into the TCP stream (routing attacks).

BGP sessions can be secured with a variety of mechanisms. MD5
protection of the TCP session header, described in RFC 2385 [7], was
the first such mechanism. It is now deprecated has been obsoleted by the TCP
Authentication Option (TCP-AO, (TCP-AO; RFC 5925 [4]) [4]), which offers stronger
protection. While MD5 is still the most used mechanism due to its
availability in
vendor's vendors' equipment, TCP-AO SHOULD be preferred when
implemented.

IPsec could also be used for session protection. At the time this
document is published, of
publication, there is not enough experience on impacts of the use impact of using
IPsec for BGP peerings peerings, and further analysis is required to define
guidelines.

The drawback of TCP session protection is additional configuration
and management overhead for the maintenance of authentication
information (ex: (for example, MD5
password) maintenance. passwords). Protection of TCP sessions
used by BGP is thus NOT REQUIRED even when peerings are established
over shared networks where spoofing can be done (like IXPs), but
operators are RECOMMENDED to consider the trade-offs and to apply TCP
session protection where appropriate.

Network

Furthermore, network administrators SHOULD block spoofed packets
(packets with a source IP address belonging to their IP address
space) at all edges of their network (see RFC 2827 [8] and RFC 3704
[9]). This protects the TCP session used by iBGP Internal BGP (IBGP) from
attackers outside the Autonomous System.

5.2. BGP TTL security Security (GTSM)

BGP sessions can be made harder to spoof with the Generalized TTL
Security Mechanisms (GTSM, (GTSM aka TTL security), defined in RFC 5082 [3].
Instead of sending TCP packets with TTL value of 1, the BGP speakers
send the TCP packets with TTL value of 255 255, and the receiver checks
that the TTL value equals 255. Since it's impossible to send an IP
packet with TTL of 255 to a non-directly-connected an IP host, host that is not directly connected,
BGP TTL security effectively prevents all spoofing attacks coming
from third parties not directly connected to the same subnet as the BGP-
speaking
BGP-speaking routers. Network administrators SHOULD implement TTL
security on directly connected BGP peerings.

GTSM could also be applied to multi-hop BGP peering as well. To
achieve this this, TTL needs to be configured with a proper value
depending on the distance between BGP speakers (using the principle
described above). Nevertheless Nevertheless, it is not as effective as because
anyone inside the TTL diameter could spoof the TTL.

Like MD5 protection, TTL security has to be configured on both ends
of a BGP session.

6. Prefix filtering Filtering

The main aspect of securing BGP resides in controlling the prefixes
that are received/advertised received and advertised on the BGP peerings. Prefixes
exchanged between BGP peers are controlled with inbound and outbound
filters that can match on IP prefixes (prefix filters, Section 6), (as described in this section),
AS paths
(as-path filters, (as described in Section 9) or any other attributes of a BGP
prefix (for example, BGP communities, as described in Section 11).

6.1. Definition of prefix filters Prefix Filters

This section list lists the most commonly used prefix filters. Following The
following sections will clarify where these filters should be
applied.

6.1.1. Special purpose prefixes Special-Purpose Prefixes

6.1.1.1. IPv4 special purpose prefixes Special-Purpose Prefixes

The IANA IPv4 Special-Purpose Address Registry [22] [23] maintains the
list of IPv4 special purpose special-purpose prefixes and their routing scope, and it
SHOULD be used for prefix filters prefix-filter configuration. Prefixes with value
"False" in column "Global" SHOULD be discarded on Internet BGP
peerings.

6.1.1.2. IPv6 special purpose prefixes Special-Purpose Prefixes

The IANA IPv6 Special-Purpose Address Registry [23] [24] maintains the
list of IPv6 special purpose special-purpose prefixes and their routing scope, and it
SHOULD be used for prefix filters prefix-filter configuration. Only prefixes with
value "False" in column "Global" SHOULD be discarded on Internet BGP
peerings.

6.1.2. Unallocated Prefixes not allocated

IANA allocates prefixes to RIRs which that in turn allocate prefixes to
LIRs (Local Internet Registries). It is wise not to accept routing
table prefixes that are not allocated by IANA and/or RIRs. This
section details the options for building a list of allocated prefixes
at every level. It is important to understand that filtering
unallocated prefixes not allocated requires constant updates updates, as prefixes are
continually allocated. Therefore Therefore, automation of such prefix filters
is key for the success of this approach. Network administrators
SHOULD NOT consider solutions described in this section if they are
not capable of maintaining updated prefix filters: the damage would
probably be worse than the intended security policy.

6.1.2.1. IANA allocated prefix filters IANA-Allocated Prefix Filters

IANA has allocated all the IPv4 available space. Therefore Therefore, there is
no reason why network administrators would keep checking that
prefixes they receive from BGP peers are in the IANA allocated IANA-allocated IPv4
address space [24]. [25]. No specific filters need to be put in place by
administrators who want to make sure that IPv4 prefixes they receive
in BGP updates have been allocated by IANA.

For IPv6, given the size of the address space, it can be seen as wise
accepting
to accept only prefixes derived from those allocated by IANA.
Administrators can dynamically build this list from the IANA IANA-
allocated IPv6 space [25]. [26]. As IANA keeps allocating prefixes to
RIRs, the aforementioned list should be checked regularly against
changes
changes, and if they occur, prefix filters should be computed and
pushed on network devices. The list could also be pulled directly by
routers when they implement such mechanisms. As there is delay
between the time a RIR receives a new prefix and the moment it starts
allocating portions of it to its LIRs, there is no need for doing
this step quickly and frequently. However, network administrators
SHOULD ensure that all IPv6 prefix filters are updated within a
maximum of one month after any change in the list of IPv6 prefix prefixes
allocated by IANA.

If the process in place (manual (whether manual or automatic) cannot
guarantee that the list is updated regularly regularly, then it's better not to
configure any filters based on allocated networks. The IPv4
experience has shown that many network operators implemented filters
for prefixes not allocated by IANA but did not update them on a
regular basis. This created problems for the latest allocations allocations, and
required a extra work for RIRs that had to "de-bogonize" the newly
allocated prefixes. (See [18] for information on de-bogonizing.)

6.1.2.2. RIR allocated prefix filters RIR-Allocated Prefix Filters

A more precise check can be performed when one would like to make
sure that prefixes they receive are being originated or transited by
autonomous systems
Autonomous Systems (ASes) entitled to do so. It has been observed in
the past that an AS (Autonomous System) could easily advertise someone else's prefix (or
more specific prefixes) and create black holes or security threats.
To partially mitigate this risk, administrators would need to make
sure BGP advertisements correspond to information located in the
existing registries. At this stage 2 stage, two options can be
considered (short considered:
short- and long term options). long-term options. They are described in the following
subsections.

6.1.2.2.1. Prefix filters creation Filters Created from Internet Routing Registries
(IRR)
(IRRs)

An Internet Routing Registry (IRR) is a database containing Internet
routing information, described using Routing Policy Specification
Language objects - RFC as described in RFC 4012 [10]. Network
administrators are given privileges to describe routing policies of
their own networks in the
IRR IRR, and that information is published,
usually publicly. A majority of Regional Internet Registries do also
operate an IRR and can control
that whether registered routes conform to
the prefixes that are allocated or directly
assigned.However, assigned. However, it
should be noted that the list of such prefixes is not necessarily a
complete list, and as such the list of routes in an IRR is not the
same as the set of RIR allocated RIR-allocated prefixes.

It is possible to use the IRR information to build, for a given
neighbor autonomous system, AS, a list of prefixes originated or transited which prefixes that one may
accept. This can be done relatively easily using scripts and
existing tools capable of retrieving this information in from the
registries. This approach is exactly the same for both IPv4 and
IPv6.

The macro-algorithm for the script is described as follows. For the peer that
is considered, the distant network administrator has provided the autonomous system AS
and may be able to provide an AS-SET object (aka AS-MACRO). An
AS-SET is an object which that contains AS numbers or other AS-SETs. An
operator may create an AS-SET defining all the AS numbers of its
customers. A tier Tier 1 transit provider might create an AS-SET
describing the AS-SET of connected operators, which in turn describe
the AS numbers of their customers. Using recursion, it is possible
to retrieve from an AS-SET the complete list of AS numbers that the
peer is likely to announce. For each of these AS numbers, it is also
easy to check look in the corresponding IRR for all associated prefixes.
With these two mechanisms mechanisms, a script can build build, for a given peer peer, the
list of allowed prefixes and the AS number from which they should be
originated. One could decide not use the origin information and only
build monolithic prefix filters from fetched data.

As prefixes, AS numbers numbers, and AS-SETs may not all be under the same
RIR authority, a difficulty resides choosing it is difficult to choose for each object the
appropriate IRR to poll. Some IRRs have been created and are not
restricted to a given region or authoritative RIR. They allow RIRs
to publish information contained in their IRR in a common place.
They also make it possible for any subscriber (probably under
contract) to publish information too. When doing requests inside
such an IRR, it is possible to specify the source of information in
order to have the most reliable data. One could check a popular IRR
containing many sources (such as RADB [26], RADb [27], the Routing Assets
Database) and only select as sources some desired RIRs and trusted
major ISPs (Internet Service Providers).

As objects in IRRs may frequently vary over time, it is important
that prefix filters computed using this mechanism are refreshed
regularly. A Refreshing the filters on a daily basis could even SHOULD be
considered as some because routing changes must sometimes be done sometimes in a certain an
emergency and registries may be updated at the very last moment. It has to be noted
Note that this approach significantly increases the complexity of the
router
configurations configurations, as it can quickly add tens of thousands of
configuration lines for some important peers. To manage this
complexity, network
adminstrators administrators could use, for example use example, IRRToolSet [29],
[30], a set of tools making it possible to simplify the creation of
automated filters filter configuration from policies stored in an IRR.

Last but not least, network administrators SHOULD publish and
maintain their resources properly in the IRR database maintained by
their RIR, when available.

6.1.2.2.2. SIDR - Secure Inter Domain Inter-Domain Routing

An infrastructure called SIDR (Secure Inter-Domain Routing),
described in RFC 6480 [12] [12], has been designed to secure Internet
advertisements. At the time of writing this document is written, document, many documents
have been published and a framework with a complete set of protocols
is proposed so that advertisements can be checked against signed
routing objects in RIR routing registries. RIRs. There are basically two services that SIDR
offers:

o Origin validation, described in RFC 6811 [5], seeks at making to make sure
that attributes associated with a routes are correct (the correct. (The major
point being is the validation of the AS number originating this
route). a given
route.) Origin validation is now operational (Internet
registries, protocols, implementations on some routers...) routers), and in
theory it can be implemented knowing that the proportion number of signed
resources is still low at the time of writing this document is written. document.

o Path validation provided by BGPsec [27] [29] seeks at making to make sure that no ones announce
one announces fake/wrong BGP paths that would attract trafic traffic for
a given destination, destination; see RFC 7132 [16]. BGPsec is still an
on-going
ongoing work item at the time of writing this document is written and
therefore cannot be implemented.

Implementing SIDR mechanisms is expected to solve many of the BGP
routing security problems in the long term term, but it may take time for
deployments to be made and objects to become signed. It also has to
be pointed Also, note that
the SIDR infrastructure is complementing (not replacing) the security
best practices listed in this document. Network Therefore, network
administrators SHOULD therefore implement any SIDR proposed mechanism
(example: (for
example, route origin validation) on top of the other existing
mechanisms even if they could sometimes appear to be targeting the
same goal.

If route origin validation is implemented, the reader SHOULD refer to
the rules described in RFC 7115 [15]. In short, each external route
received on a router SHOULD be checked against the RPKI Resource Public
Key Infrastructure (RPKI) data set:

o If a corresponding ROA (Route Origin Authorization) is found and
is valid valid, then the prefix SHOULD be accepted.

o It If the ROA is found and is INVALID INVALID, then the prefix SHOULD be
discarded.

o If an a ROA is not found found, then the prefix SHOULD be accepted accepted, but the
corresponding route SHOULD be given a low preference.

In addition to this, network administrators SHOULD sign their routing
objects so their routes can be validated by other networks running
origin validation.

One should understand that the RPKI model brings new new, interesting
challenges. The paper On "On the Risk of Misbehaving RPKI Authorities
[30] Authorities"
[31] explains how the RPKI model can impact the Internet if
authorities don't behave as they are supposed to do. to. Further analysis
is certainly required on RPKI, which carries part of BGP security.

6.1.3. Prefixes too specific That Are Too Specific

Most ISPs will not accept advertisements beyond a certain level of
specificity (and in return return, they do not announce prefixes they
consider as to be too specific). That acceptable specificity is decided
for each peering between the 2 two BGP peers. Some ISP communities
have tried to document acceptable specificity. This document does
not make any judgement on what the best approach is, it just recalls notes
that there are existing practices on the Internet and recommends that
the reader to refer to what those are. them. As an example example, the RIPE community has
documented that as of that, at the time of writing of this document, IPv4
prefixes longer than /24 and IPv6 prefixes longer than /48 are
generally not announced/accepted neither announced nor accepted in the Internet [19] [20]. [20] [21].
These values may change in the future.

6.1.4. Filtering prefixes belonging Prefixes Belonging to the local Local AS and downstreams Downstreams

A network SHOULD filter its own prefixes on peerings with all its
peers (inbound direction). This prevents local traffic (from a local
source to a local destination) from leaking over an external peering peering,
in case someone else is announcing the prefix over the Internet.
This also protects the infrastructure which that may directly suffer in
case if the
backbone's prefix is suddenly preferred over the Internet.

In some cases, for example in multi-homing example, multihoming scenarios, such filters
SHOULD NOT be applied applied, as this would break the desired redundancy.

To an extent, such filters can also be configured on a network for
the prefixes of its downstreams in order to protect them them, too. Such
filters must be defined with caution as they can break existing
redundancy mechanisms. For example in case example, when an operator has a
multihomed customer, it should keep accepting the customer prefix
from its peers and upstreams. This will make it possible for the
customer to keep accessing its operator network (and other customers)
via the Internet in case even if the BGP peering between the customer and the
operator is down.

6.1.5. IXP LAN prefixes Prefixes

6.1.5.1. Network security Security

When a network is present on an IXP and peers with other IXP members
over a common subnet (IXP LAN prefix), it SHOULD NOT accept more more-
specific prefixes for the IXP LAN prefix from any of its external BGP
peers. Accepting these routes may create a black hole for
connectivity to the IXP LAN.

If the IXP LAN prefix is accepted as an "exact match", care needs to
be taken to avoid prevent other routers in the network from sending IXP
traffic towards the externally-learned externally learned IXP LAN prefix (recursive
route lookup pointing into the wrong direction). This can be
achieved by preferring IGP routes before eBGP, over External BGP (EBGP), or by
using "BGP next-hop-self" on all routes learned on that IXP.

If the IXP LAN prefix is accepted at all, it SHOULD only be accepted
from the ASes that the IXP authorizes to announce it - which -- this will
usually be automatically achieved by filtering announcements by using
the IRR
DB. database.

6.1.5.2. pMTUd PMTUD and the loose Loose uRPF problem Problem

In order to have pMTUd PMTUD working in the presence of loose uRPF, it is
necessary that all the networks that may source traffic that could
flow through the IXP (ie. (i.e., IXP members and their downstreams) have a
route for the IXP LAN prefix. This is necessary as "packet too big"
ICMP messages sent by IXP members' routers may be sourced using an
address of the IXP LAN prefix. In the presence of loose uRPF, this
ICMP packet is dropped if there is no route for the IXP LAN prefix or
a less specific route covering IXP LAN prefix.

In that case, any IXP member SHOULD make sure it has a route for the
IXP LAN prefix or a less specific prefix on all its routers and that
it announces the IXP LAN prefix or the less specific route (up to a
default route) to its downstreams. The announcements done for this
purpose SHOULD pass IRR-generated filters described in
Section 6.1.2.2.1 as well as "prefixes that are too specific" filters
described in Section 6.1.3. The easiest way to implement this is that for
the IXP itself takes to take care of the origination of its prefix and advertises
advertise it to all IXP members through a BGP peering. Most likely likely,
the BGP route servers would be used for this. The this, and the IXP would most likely send
its entire prefix prefix, which would be equal to or less specific than the
IXP LAN prefix.

Appendix Appendix A gives an example of guidelines regarding IXP LAN prefix.

6.1.6. The default route Default Route

6.1.6.1. IPv4

The

Typically, the 0.0.0.0/0 prefix is likely not intended to be accepted nor or
advertised other than except in specific customer / provider configurations, customer/provider configurations;
general filtering outside of these is RECOMMENDED.

6.1.6.2. IPv6

The

Typically, the ::/0 prefix is likely not intended to be accepted nor or
advertised
other than except in specific customer / provider configurations, customer/provider configurations;
general filtering outside of these is RECOMMENDED.

6.2. Prefix filtering recommendations Filtering Recommendations in full routing networks Full Routing Networks

For networks that have the full Internet BGP table, some policies
should be applied on each BGP peer for received and advertised
routes. It is RECOMMENDED that each autonomous system Autonomous System configures
rules for advertised and received routes at all its borders borders, as this
will protect the network and its peer even in case of
misconfiguration. The most commonly used filtering policy is
proposed in this section and uses prefix filters defined in previous
section
Section 6.1.

6.2.1. Filters with Internet peers Peers

6.2.1.1. Inbound filtering Filtering

There are basically 2 options, two options -- the loose one where no check will
be done against RIR allocations and the strict one where it will be
verified that announcements strictly conform to what is declared in
routing registries.

6.2.1.1.1. Inbound filtering loose option Filtering Loose Option

In this case, the following prefixes received from a BGP peer will be
filtered:

o Prefixes prefixes that are not globally routable (Section 6.1.1)

o Prefixes prefixes not allocated by IANA (IPv6 only) (Section 6.1.2.1)

o Routes routes that are too specific (Section 6.1.3)

o Prefixes prefixes belonging to the local AS (Section 6.1.4)

o IXP LAN prefixes (Section 6.1.5)

o The the default route (Section 6.1.6)

6.2.1.1.2. Inbound filtering strict option Filtering Strict Option

In this case, filters are applied to make sure advertisements
strictly conform to what is declared in routing registries
(Section 6.1.2.2). Warning is given as registries are not always
accurate (prefixes missing, wrong information...) information, etc.). This varies
across the registries and regions of the Internet. Before applying a
strict
policy policy, the reader SHOULD check the impact on the filter and
make sure the solution is not worse than the problem.

Also

Also, in case of script failure failure, each administrator may decide if all
routes are accepted or rejected depending on routing policy. While
accepting the routes during that time frame could break the BGP
routing security, rejecting them might re-route too much traffic on
transit peers, and could cause more harm than what a loose policy
would have done.

In addition to this, network administrators could apply the following
filters beforehand in case the routing registry that's used as the
source of information by the script is not fully trusted:

o Prefixes prefixes that are not globally routable (Section 6.1.1)

o Routes routes that are too specific (Section 6.1.3)

o Prefixes prefixes belonging to the local AS (Section 6.1.4)

o IXP LAN prefixes (Section 6.1.5)

o The the default route (Section 6.1.6)

6.2.1.2. Outbound filtering

Configuration Filtering

The configuration should be put in place to make sure ensure that only appropriate prefixes are
sent. These can be, for example, prefixes belonging to both the
network in question and its downstreams. This can be achieved by
using a combination of BGP communities, AS-paths AS paths, or both. It can also Also, it may be desirable that
to add the following filters are
positioned before any policy to avoid unwanted
route announcement announcements due to bad configuration:

o Prefixes that are not globally routable (Section 6.1.1)

o Routes that are too specific (Section 6.1.3)

o IXP LAN prefixes (Section 6.1.5)

o The default route (Section 6.1.6)

In case

If it is possible to list the prefixes to be advertised, then just
configuring the list of allowed prefixes and denying the rest is
sufficient.

6.2.2. Filters with customers Customers

6.2.2.1. Inbound filtering Filtering

The inbound policy with end customers is pretty straightforward: only
customers
customer prefixes SHOULD be accepted, all others SHOULD be discarded.
The list of accepted prefixes can be manually specified, after having
verified that they are valid. This validation can be done with the
appropriate IP address management authorities.

The same rules apply in case when the customer is also a network connecting other
customers (for example example, a tier Tier 1 transit provider connecting service
providers). An exception can be envisaged in case
it is known that when the customer network applies strict
inbound/outbound prefix filtering, and the number of there are too many prefixes
announced by that network is too large to list them in the router configuration.
In that case case, filters as in Section 6.2.1.1 can be applied.

6.2.2.2. Outbound filtering Filtering

The outbound policy with customers may vary according to the routes
the customer wants to receive. In the simplest possible scenario,
the customer may only want to receive only the default route, which route; this can be
done easily by applying a filter with the default route only.

In case the customer wants to receive the full routing (in case (if it is
multihomed or if it wants to have a view of the Internet table), the
following filters can be simply applied on the BGP peering:

o Prefixes prefixes that are not globally routable (Section 6.1.1)

o Routes routes that are too specific (Section 6.1.3)

o The the default route (Section 6.1.6)

There can be a difference for

In some cases, the default route that can be announced customer may desire to receive the customer default route
in addition to the full BGP table. This can be done by the provider
simply by removing the filter for the default route. As the default
route may not be present in the routing table, network administrators
may decide to originate it only for peerings where it has to be
advertised.

6.2.3. Filters with upstream providers Upstream Providers

6.2.3.1. Inbound filtering

In case Filtering

If the full routing table is desired from the upstream, the prefix
filtering to apply is the same as the one for peers Section 6.2.1.1
with the exception of the default route. The Sometimes, the default
route (in addition to the full BGP table) can be desired from an
upstream provider in addition to the
full BGP table. In case provider. If the upstream provider is supposed to announce
only the default route, a simple filter will be applied to accept
only the default prefix and nothing else.

6.2.3.2. Outbound filtering Filtering

The filters to be applied would most likely not differ much from the
ones applied for Internet peers (Section 6.2.1.2). But However,
different policies could be applied in case it is desired that if a particular upstream does should
not provide transit to all the prefixes.

6.3. Prefix filtering recommendations Filtering Recommendations for leaf networks Leaf Networks

6.3.1. Inbound filtering Filtering

The leaf network will deploy the filters corresponding to the routes
it is requesting from its upstream. In case If a default route is requested,
a simple inbound filter can be applied to accept only the default
route (Section 6.1.6). In case If the leaf network is not capable of listing
the prefixes because the amount is there are too large many (for
example example, if it requires
the full Internet routing table) table), then it should configure the
following filters to avoid receiving bad announcements from its
upstream:

o Prefixes prefixes not routable (Section 6.1.1)

o Routes too routes that are too specific (Section 6.1.3)

o Prefixes prefixes belonging to local AS (Section 6.1.4)

o The the default route (Section 6.1.6) depending if on whether or not the
route is requested or not

6.3.2. Outbound filtering Filtering

A leaf network will most likely have a very straightforward policy:
it will only announce its local routes. It can also configure the
following prefixes
prefix filters described in Section 6.2.1.2 to avoid announcing
invalid routes to its upstream provider.

7. BGP route flap dampening Route Flap Dampening

The BGP route flap dampening mechanism makes it possible to give
penalties to routes each time they change in the BGP routing table.
Initially
Initially, this mechanism was created to protect the entire Internet
from multiple events impacting that impact a single network. Studies have
shown that implementations of BGP route flap dampening could cause
more harm than they solve problems and therefore benefit; therefore, in the past, the RIPE community
has in the
past recommended not against using BGP route flap dampening [18]. Studies
have then been [19]. Later,
studies were conducted to propose new route flap dampening thresholds
in order to make the solution "usable", "usable"; see RFC 7196 [6] and [22] (in
which RIPE has reviewed its recommendations in [21]. recommendations). This document RECOMMENDS
following IETF and RIPE recommendations and only use using BGP route flap
dampening with the adjusted configured thresholds.

8. Maximum prefixes Prefixes on a peering Peering

It is RECOMMENDED to configure a limit on the number of routes to be
accepted from a peer. Following The following rules are generally RECOMMENDED:

o From peers, it is RECOMMENDED to have a limit lower than the
number of routes in the Internet. This will shut down the BGP
peering if the peer suddenly advertises the full table. Network
admistrators
administrators can also configure different limits for each peer,
according to the number of routes they are supposed to advertise advertise,
plus some headroom to permit growth.

o From upstreams which that provide full routing, it is RECOMMENDED to
have a limit higher than the number of routes in the Internet. A
limit is still useful in order to protect the network (and in
particular
particular, the routers' memory) if too many routes are sent by
the upstream. The limit should be chosen according to the number
of routes that can actually be handled by routers.

It is important to regularly review the limits that are configured as
the Internet can quickly change over time. Some vendors propose
mechanisms to have two thresholds: while the higher number specified
will shutdown shut down the peering, the first threshold will only trigger a
log and can be used to passively adjust limits based on observations
made on the network.

9. AS-path filtering AS Path Filtering

This section lists the RECOMMENDED practices when processing BGP AS-
paths: AS
paths.

o Network administrators SHOULD accept from customers only AS(4)-
Paths 2-byte or
4-byte AS paths containing ASNs belonging to (or authorized to
transit through) the customer. If network administrators can not cannot
build and generate filtering expressions to implement this, they
SHOULD consider accepting only path lengths relevant to the type
of customer they have (as in, if these customers are a leaf or
have customers of their own), own) and SHOULD try to discourage
excessive prepending in such paths. This loose policy could be
combined with filters for specific AS(4)-Paths 2-byte or 4-byte AS paths that
must not be accepted if advertised by the customer, such as
upstream transit provider providers or peer ASNs.

o Network administrators SHOULD NOT accept prefixes with private AS
numbers in the AS-path except AS path unless the prefixes are from customers. Exception: An
exception could occur when an upstream is offering some particular
service like black-hole origination based on a private AS number. number:
in that case, prefixes SHOULD be accepted. Customers should be
informed by their upstream in order to put in place ad-hoc ad hoc policy
to use such services.

o Network administrators SHOULD NOT accept prefixes when the first
AS number in the AS-path AS path is not the one of the peer peer's unless the
peering is done toward a BGP route-server route server [17] (for example example, on an
IXP) with transparent AS path handling. In that case case, this
verification needs to be de-activated deactivated, as the first AS number will
be the one of an IXP member member, whereas the peer AS number will be
the one of the BGP route-server. route server.

o Network administrators SHOULD NOT advertise prefixes with non-
empty AS-path a
nonempty AS path unless they intend to be provide transit for these
prefixes.

o Network administrators SHOULD NOT advertise prefixes with upstream
AS numbers in the AS-path AS path to their peering AS unless they intend
to be provide transit for these prefixes.

o Private AS numbers are conventionally used in contexts that are
"private" and SHOULD NOT be used in advertisements to BGP peers
that are not party to such private arrangements, and should they SHOULD
be stripped when received from BGP peers that are not party to
such private arrangements.

o Network administrators SHOULD NOT override BGP's default behavior
accepting behavior,
i.e., they should not accept their own AS number in the AS-path. In case AS path.
When considering an
exception to this is required, impacts should exception, the impact (which may be studied carefully
as this can create severe impact on routing.

AS-path
routing) should be studied carefully.

AS path filtering should be further analyzed when ASN renumbering is
done. Such an operation is common common, and mechanisms exist to allow
smooth ASN migration [28]. The usual migration technique, local to a
router, consists in modifying the AS-path AS path so it is presented to a
peer with the previous ASN, as if no renumbering was done. This
makes it possible to change the ASN of a router without reconfiguring
all
eBGP EBGP peers at the same time (as this that operation would require
synchronization with all peers attached to that router). During this
renumbering operation, the rules described above may be adjusted.

10. Next-Hop Filtering

If peering on a shared network, like an IXP, BGP can advertise
prefixes with a 3rd-party next-hop, third-party next hop, thus directing packets not to
the peer announcing the prefix but somewhere else.

This is a desirable property for BGP route-server setups [17], where
the route-server route server will relay routing information, information but has neither the
capacity nor the desire to receive the actual data packets. So So, the
BGP
route-server route server will announce prefixes with a next-hop setting
pointing to the router that originally announced the prefix to the route-
route server.

In direct peerings between ISPs, this is undesirable, as one of the
peers could trick the other one to send into sending packets into a black
hole (unreachable next-hop) next hop) or to an unsuspecting 3rd third party who
would then have to carry the traffic. Especially for black-holing,
the root cause of the problem is hard to see without inspecting BGP
prefixes at the receiving router at of the IXP.

Therefore, an inbound route policy SHOULD be applied on IXP peerings
in order to set the next-hop next hop for accepted prefixes to the BGP peer IP
address (belonging to the IXP LAN) that sent the prefix (which is
what "next-hop-self" would enforce on the sending side).

This policy SHOULD NOT be used on route-server peerings, peerings or on
peerings where network administrators intentionally permit the other
side to send 3rd-party next-hops. third-party next hops.

This policy also SHOULD be adjusted if the best practice of Remote
Triggered Black Holing
best practice (aka RTBH - as described in RFC 6666 [13]) is
implemented. In that
case case, network administrators would apply a
well-known BGP next-hop next hop for routes they want to filter (if an
Internet threat is observed from/to this route route, for example). This well known next-hop
well-known next hop will be statically routed to a null interface.
In combination with a unicast RPF check, this will discard traffic
from and toward this prefix. Peers can exchange information about black-holes using
black holes using, for example example, particular BGP communities. Network
administrators could propagate black-holes black-hole information to their peers
using agreed an agreed-upon BGP community: when receiving a route with that community
community, a configured policy could change the
next-hop next hop in order to
create the black hole.

11. BGP community scrubbing

Optionally Community Scrubbing

Optionally, we can consider the following rules on BGP AS-paths: AS paths:

o Network administrators SHOULD scrub inbound communities with their
number in the high-order bits, and allow only those communities
that customers/peers can use as a signaling mechanism

o Networks administrators SHOULD NOT remove other communities
applied on received routes (communities not removed after
application of the previous statement). In particular they SHOULD
keep original communities when particular, they apply a community. Customers
might need them to communicate with upstream providers. In
particular network administrators
SHOULD NOT (generally) remove
the no-export community as it is usually announced by their peer
for a certain purpose.

12. Change logs

!!! NOTE TO THE RFC EDITOR: THIS SECTION WAS ADDED TO TRACK CHANGES
AND FACILITATE WORKING GROUP COLLABORATION. IT MUST BE DELETED
BEFORE PUBLICATION !!!

12.1. Diffs between draft-jdurand-bgp-security-01 and draft-jdurand-
bgp-security-00

Following changes have been made since previous document draft-
jdurand-bgp-security-00:

o "This documents" typo corrected in the former abstract

o Add normative reference for RFC5082 in former section 3.2

o "Non routable" changed in title of former section 4.1.1

o Correction of typo for IPv4 loopback prefix in former section
4.1.1.1

o Added shared transition space 100.64.0.0/10 in former section
4.1.1.1

o Clarification that 2002::/16 6to4 prefix can cross network
boundaries in former section 4.1.1.2

o Rationale of 2000::/3 explained in former section 4.1.1.2
o Added 3FFE::/16 prefix forgotten initially in the simplified list
of prefixes that must not be routed by definition in former
section 4.1.1.2

o Warn that filters for prefixes not allocated by IANA MUST only be
done if regular refresh is guaranteed, with some words about the
IPv4 experience, in former section 4.1.2.1

o Replace RIR database with IRR. A definition of IRR is added in
former section 4.1.2.2

o Remove any reference to anti-spoofing in former section 4.1.4

o Clarification for IXP LAN prefix and pMTUd problem in former
section 4.1.5

o "Autonomous filters" typo (instead of Autonomous systems)
corrected in the former section 4.2

o Removal of an example for manual address validation in former
section 4.2.2.1

o RFC5735 obsoletes RFC3300

o Ingress/Egress replaced by Inbound/Outbound in all the document

12.2. Diffs between draft-jdurand-bgp-security-02 and draft-jdurand-
bgp-security-01

Following changes have been made since previous document draft-
jdurand-bgp-security-01:

o 2 documentation prefixes were forgotten due to errata in RFC5735.
But all prefixes were removed from that document which now point
to other references for sake of not creating a new "registry" that
would become outdated sooner or later

o Change MD5 section with global TCP security session and
introducing TCP-AO in former section 3.1. Added reference to
BCP38

o Added new section 3 about BGP router protection with forwarding
plane ACL

o Change text about prefix acceptable specificity in former section
4.1.3 to explain this doc does not try to make recommendations
o Refer as much as possible to existing registries to avoid creating
a new one in former section 4.1.1.1 and 4.1.1.2

o Abstract reworded

o 6to4 exception described (only more specifics MUST be filtered)

o More specific -> more specifics

o should -> MUST for the prefixes an ISP needs to filter from its
customers in former section 4.2.2.1

o Added "plus some headroom to permit growth" in former section 7

o Added new section on Next-Hop filtering

12.3. Diffs between draft-ietf-opsec-bgp-security-00 and draft-jdurand-
bgp-security-02

Following changes have been made since previous document draft-
jdurand-bgp-security-02:

o Added a subsection for RTBH in next-hop section with reference to
RFC6666

o Changed last sentence of introduction

o Many edits throughout the document

o Added definition of tier 1 transit provider

o Removed definition of a BGP peering

o Removed description of routing policies for IPv6 prefixes in IANA
special registry as this now contains a routing scope field

o Added reference to RFC6598 and changed the IPv4 prefixes to be
filtered by definition section

o IXP added in accronym/definition section and only term used
throughout the doc now

12.4. Diffs between draft-ietf-opsec-bgp-security-01 and draft-ietf-
opsec-bgp-security-00

Following changes have been made since previous document draft-ietf-
opsec-bgp-security-00:

o Obsolete RFC2385 moved from normative to informative reference

o Clarification of preference of TCP-AO over MD5 in former section
4.1

o Mentioning KARP efforts in TCP session protection section in
former section 4 and adding 3 RFC as informative references: 6518,
6862 and 6952

o Removing reference to SIDR working-group

o Better dissociating origin validation and path validation to
clarify what's potentially available for deployment

o Adding that SIDR mechanisms should be implemented in addition to
the other ones mentioned throughout this document

o Added a paragraph in former section 8 about ASN renumbering

o Change of security considerations section

o Added the newly created IANA IPv4 Special Purpose Address Registry
instead of references to RFCs listing these addresses

12.5. Diffs between draft-ietf-opsec-bgp-security-02 and draft-ietf-
opsec-bgp-security-01

Following changes have been made since previous document draft-ietf-
opsec-bgp-security-01:

o Added a reference to draft-ietf-sidr-origin-ops

o Added a reference to RFC6811 and RFC6907

o Changes "Most of RIR's" to "A majority of RIR's" on IRR
availability

o Various edits

o Added NIST BGP security recommendations document

o Added that it's possible to get info from ISPs from RADB

o Correction of the url for IPv4 special use prefixes repository

o Clarification of the fact only prefixes with Global Scope set to
False MUST be discarded
o IANA list could be pulled directly by routers (not just pushed on
routers).

o Warning added when prefixes are checked against IRR

o Recommend network operators to sign their routing objects

o Recommend network operators to publish their routing objects in
IRR of their IRR when available

o Dissociate rules for local AS and downstreams in former section
5.1.4

12.6. Diffs between draft-ietf-opsec-bgp-security-03 and draft-ietf-
opsec-bgp-security-02

Following changes have been made since previous document draft-ietf-
opsec-bgp-security-02:

o Added a note on TCP-AO to be preferred over MD5

o Mention that loose AS filtering with customers can be combined
with precise filters for important ASNs (example those of
transits) that are must not be received on theses peers in former
section 8.

o MD5 removed from abstract

o recommended -> RECOMMENDED where appropriate

o Reference to BCP38 and BCP84 in former section 4.1

o Added a note to RFC Editor to remove change section before
publication

o Removal of "future work" section

o Added rate-limiting in addition to filtering in former section 3

o Reference to IRRToolSet in former section 5.1.2.3

o Removed "foreword" section

12.7. Diffs between draft-ietf-opsec-bgp-security-04 and draft-ietf-
opsec-bgp-security-03

Following changes have been made since previous document draft-ietf-
opsec-bgp-security-03:

o RFC6890 updates RFC5735

o RFC6890 updates RFC5156

o Removed reference RFC2234 and RFC 4234

o Moved route-server draft into informative reference section

12.8. Diffs between draft-ietf-opsec-bgp-security-05 and draft-ietf-
opsec-bgp-security-04

Following changes have been made since previous document draft-ietf-
opsec-bgp-security-04:

o RFC7196 updates draft-ietf-idr-rfd-usable

o RFC7115 updates draft-ietf-sidr-origin-ops

o draft-ietf-idr-ix-bgp-route-server-05 updates ietf-idr-ix-bgp-
route-server-00

12.9. Diffs between draft-ietf-opsec-bgp-security-06 and draft-ietf-
opsec-bgp-security-05

Following changes have been made since previous document draft-ietf-
opsec-bgp-security-05:

o Wording improvements

o Introduction improved

o References are expanded (not just reference numbers are displayed
but also the title of the document

o First occurence of accronyms expanded

o GTSM for multi-hop peerings

o Remove eBGP as protected by BCP38

o Add a caveat for IPsec for session protection
o Changed MUST for SHOULD everywhere

o Small changes in communities section

o Removed simplified IPv6 prefix list

o Removed note in section 9 about 32 bits ASN

o IXP LAN prefix example in appendix

o Make sure all references are in the text. Most of them were
removed as they were initially here for previous version when IANA
registries with routing scopes did not exist

13. Acknowledgements

The authors would like to thank the following people for their
comments and support: Marc Blanchet, Ron Bonica, Randy Bush, David
Freedman, Wesley George, Daniel Ginsburg, David Groves, Mike Hugues,
Joel Jaeggli, Tim Kleefass, Warren Kumari, Jacques Latour, Lionel
Morand, Jerome Nicolle, Hagen Paul Pfeifer, Thomas Pinaud, Carlos
Pignataro, Jean Rebiffe, Donald Smith, Kotikalapudi Sriram, Matjaz
Straus, Tony Tauber, Gunter Van de Velde, Sebastian Wiesinger,
Matsuzaki Yoshinobu.

Authors would like to thank once again Gunter Van de Velde for
presenting the draft at several IETF meetings in various working
groups, indeed helping dissemination of this document and gathering
of precious feedback.

14. IANA Considerations

This memo includes no request keep original communities when they apply a community.
Customers might need them to IANA.

15. communicate with upstream providers.
In particular, network administrators SHOULD NOT (generally)
remove the no-export community, as it is usually announced by
their peer for a certain purpose.

12. Security Considerations

This document is entirely about BGP operational security. It depicts
best practices that one should adopt to secure its BGP infrastructure:
protecting BGP router and BGP sessions, adopting consistent BGP
prefix and AS-path filters AS path filters, and configure configuring other options to secure
the BGP network.

On the other hand this

This document doesn't does not aim at depicting to describe existing BGP
implementations and implementations,
their potential vulnerabilities and vulnerabilities, or ways they handle errors. It does
not detail how protection could be enforced against attack techniques
using crafted packets.

16.

13. References

16.1.

13.1. Normative References

[1] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997,
<http://xml.resource.org/public/rfc/html/rfc2119.html>.
<http://www.rfc-editor.org/info/rfc2119>.

[2] Rekhter, Rekhter,, Y., Li, Li,, T., and S. Hares, Hares,, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006. 2006,
<http://www.rfc-editor.org/info/rfc4271>.

[3] Gill, V., Heasley, J., Meyer, D., Savola, Savola,, P., and C.
Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, October 2007. 2007,
<http://www.rfc-editor.org/info/rfc5082>.

[4] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, June 2010. 2010,
<http://www.rfc-editor.org/info/rfc5925>.

[5] Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R.
Austein, "BGP Prefix Origin Validation", RFC 6811, January
2013.
2013, <http://www.rfc-editor.org/info/rfc6811>.

[6] Pelsser, C., Bush, R., Patel, K., Mohapatra, P., and O.
Maennel, "Making Route Flap Damping Usable", RFC 7196, May
2014.

16.2.
2014, <http://www.rfc-editor.org/info/rfc7196>.

13.2. Informative References

[7] Heffernan, A., "Protection of BGP Sessions via the TCP MD5
Signature Option", RFC 2385, August 1998. 1998,
<http://www.rfc-editor.org/info/rfc2385>.

[8] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source
Address Spoofing", BCP 38, RFC 2827, May 2000. 2000,
<http://www.rfc-editor.org/info/rfc2827>.

[9] Baker, F. and P. Savola, "Ingress Filtering for Multihomed
Networks", BCP 84, RFC 3704, March 2004. 2004,
<http://www.rfc-editor.org/info/rfc3704>.

[10] Blunk, L., Damas, J., Parent, F., and A. Robachevsky,
"Routing Policy Specification Language next generation
(RPSLng)", RFC 4012, March 2005. 2005,
<http://www.rfc-editor.org/info/rfc4012>.

[11] Dugal, D., Pignataro, C., and R. Dunn, "Protecting the
Router Control Plane", RFC 6192, March 2011. 2011,
<http://www.rfc-editor.org/info/rfc6192>.

[12] Lepinski, M. and S. Kent, "An Infrastructure to Support
Secure Internet Routing", RFC 6480, February 2012. 2012,
<http://www.rfc-editor.org/info/rfc6480>.

[13] Hilliard, N. and D. Freedman, "A Discard Prefix for IPv6",
RFC 6666, August 2012. 2012,
<http://www.rfc-editor.org/info/rfc6666>.

[14] Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
BGP, LDP, PCEP, and MSDP Issues According to the Keying
and Authentication for Routing Protocols (KARP) Design
Guide", RFC 6952, May 2013. 2013,
<http://www.rfc-editor.org/info/rfc6952>.

[15] Bush, R., "Origin Validation Operation Based on the
Resource Public Key Infrastructure (RPKI)", BCP 185, RFC 7115,
January 2014. 2014, <http://www.rfc-editor.org/info/rfc7115>.

[16] Kent, S. and A. Chi, "Threat Model for BGP Path Security",
RFC 7132, February 2014. 2014,
<http://www.rfc-editor.org/info/rfc7132>.

[17] Jasinska, E., Hilliard, N., Raszuk, R., and N. Bakker,
"Internet Exchange Route Server",
<http://tools.ietf.org/id/
draft-ietf-idr-ix-bgp-route-server-05.txt>. Work in Progress draft-
ietf-idr-ix-bgp-route-server-06, December 2014.

[18] Karrenberg, D., "RIPE-351 - De-Bogonising New Address
Blocks", October 2005.

[19] Smith, P. and C. Panigl, "RIPE-378 - RIPE Routing Working
Group Recommendations On Route-flap Damping", May 2006.

[19]

[20] Smith, P., Evans, R., and M. Hughes, "RIPE-399 - RIPE
Routing Working Group Recommendations on Route
Aggregation", December 2006.

[20]

[21] Smith, P. and R. Evans, "RIPE-532 - RIPE Routing Working
Group Recommendations on IPv6 Route Aggregation", November
2011.

[21]

[22] Smith, P., Bush, R., Kuhne, M., Pelsser, C., Maennel, O.,
Patel, K., Mohapatra, P., and R. Evans, "RIPE-580 - RIPE
Routing Working Group Recommendations On Route-flap
Damping", January 2013.

[22] "IANA IPv4 Special Purpose Address Registry",
<http://www.iana.org/assignments/iana-ipv4-special-
registry/iana-ipv4-special-registry.xhtml>.

[23] IANA, "IANA IPv6 Special Purpose IPv4 Special-Purpose Address Registry",
<http://www.iana.org/assignments/iana-ipv6-special-
registry/iana-ipv6-special-registry.xml>.
<http://www.iana.org/assignments/
iana-ipv4-special-registry>.

[24] IANA, "IANA IPv4 IPv6 Special-Purpose Address Space Registry",
<http://www.iana.org/assignments/ipv4-address-space/
ipv4-address-space.xml>.
<http://www.iana.org/assignments/
iana-ipv6-special-registry>.

[25] IANA, "IANA IPv6 IPv4 Address Space Registry",
<http://www.iana.org/assignments/ipv6-unicast-address-
assignments/ipv6-unicast-address-assignments.xml>.
<http://www.iana.org/assignments/ipv4-address-space>.

[26] "Routing Assets Database", <http://www.radb.net>. IANA, "Internet Protocol Version 6 Address Space",
<http://www.iana.org/assignments/ipv6-address-space>.

[27] "Security Requirements for BGP Path Validation",
<http://datatracker.ietf.org/doc/
draft-ietf-sidr-bgpsec-reqs/>. Merit Network Inc., "Merit RADb", <http://www.radb.net>.

[28] George, W. and S. Amante, "Autonomous System (AS)
Migration Features and Their Effects on the BGP AS_PATH
Attribute",
<http://datatracker.ietf.org/doc/
draft-ga-idr-as-migration/>. Work in Progress, draft-ga-idr-as-migration-
03, January 2014.

[29] Bellovin, S., Bush, R., and D. Ward, "Security
Requirements for BGP Path Validation", RFC 7353, August
2014, <http://www.rfc-editor.org/info/rfc7353>.

[30] "IRRToolSet project page", <http://irrtoolset.isc.org>.

[30]

[31] Cooper, D., Heilman, E., Brogle, K., Reyzin, L., and S.
Goldberg, "On the Risk of Misbehaving RPKI Authorities",
<http://www.cs.bu.edu/~goldbe/papers/hotRPKI.pdf>.

Appendix A. IXP LAN prefix filtering Prefix Filtering - example Example

An IXP in the RIPE region is allocated an IPv4 /22 prefix by RIPE NCC
(X.Y.0.0/22 in this example) and uses a /23 of this /22 for the IXP
LAN (let say X.Y.0.0/23). This IXP LAN prefix is the one used by IXP
members to configure eBGP EBGP peerings. The IXP could also be allocated
an AS number (AS64496 in our example).

Any IXP member SHOULD make sure it filters prefixes more specific
than X.Y.0.0/23 from all its eBGP EBGP peers. If it received X.Y.0.0/24
or X.Y.1.0/24 this could seriously impact its routing.

The IXP SHOULD originate X.Y.0.0/22 and advertise it to its members
through an eBGP EBGP peering (most likely from its BGP route servers,
configured with AS64496).

The IXP members SHOULD accept the IXP prefix only if it passes the
IRR generated filters (see Section 6.1.2.2.1)

IXP members SHOULD then advertise X.Y.0.0/22 prefix to their
downstreams. This announce would pass IRR based filters as it is
originated by the IXP.

Appendix B. Acknowledgements

The authors would like to thank once again Gunter Van de Velde for
presenting the document at several IETF meetings in various working
groups, indeed helping dissemination of this document and gathering
of precious feedback.

Authors' Addresses

Jerome Durand
CISCO
Cisco Systems, Inc.
11 rue Camille Desmoulins
Issy-les-Moulineaux 92782 CEDEX
FR

Email:
France

EMail: jerduran@cisco.com
Ivan Pepelnjak
NIL Data Communications
Tivolska 48
Ljubljana 1000
Slovenia

Email:

EMail: ip@ipspace.net

Gert Doering
SpaceNet AG
Joseph-Dollinger-Bogen 14
Muenchen D-80807
Germany

Email:

EMail: gert@space.net