draft-ietf-bess-evpn-proxy-arp-nd-04.txt   draft-ietf-bess-evpn-proxy-arp-nd-05.txt 
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G. Hankins G. Hankins
Nokia Nokia
T. King T. King
D. Melzer D. Melzer
DE-CIX DE-CIX
E. Nordmark E. Nordmark
Individual Individual
Expires: October 11, 2018 April 9, 2018 Expires: May 9, 2019 November 5, 2018
Operational Aspects of Proxy-ARP/ND in EVPN Networks Operational Aspects of Proxy-ARP/ND in EVPN Networks
draft-ietf-bess-evpn-proxy-arp-nd-04 draft-ietf-bess-evpn-proxy-arp-nd-05
Abstract Abstract
The MAC/IP Advertisement route specified in [RFC7432] can optionally The EVPN MAC/IP Advertisement route can optionally carry IPv4 and
carry IPv4 and IPv6 addresses associated with a MAC address. Remote IPv6 addresses associated with a MAC address. Remote PEs can use this
PEs can use this information to reply locally (act as proxy) to IPv4 information to reply locally (act as proxy) to IPv4 ARP requests and
ARP requests and IPv6 Neighbor Solicitation messages (or 'unicast- IPv6 Neighbor Solicitation messages (or 'unicast-forward' them to the
forward' them to the owner of the MAC) and reduce/suppress the owner of the MAC) and reduce/suppress the flooding produced by the
flooding produced by the Address Resolution procedure. This EVPN Address Resolution procedure. This EVPN capability is extremely
capability is extremely useful in Internet Exchange Points (IXPs) and useful in Internet Exchange Points (IXPs) and Data Centers (DCs) with
Data Centers (DCs) with large broadcast domains, where the amount of large broadcast domains, where the amount of ARP/ND flooded traffic
ARP/ND flooded traffic causes issues on routers and CEs, as explained causes issues on routers and CEs. This document describes how the
in [RFC6820]. This document describes how the [RFC7432] EVPN proxy- EVPN Proxy-ARP/ND function may be implemented to help IXPs and other
ARP/ND function may be implemented to help IXPs and other operators operators deal with the issues derived from Address Resolution in
deal with the issues derived from Address Resolution in large large broadcast domains.
broadcast domains.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." The list material or to cite them other than as "work in progress." The list
of current Internet-Drafts can be accessed at of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html http://www.ietf.org/shadow.html
This Internet-Draft will expire on October 11, 2018. This Internet-Draft will expire on May 9, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. The DC Use-Case . . . . . . . . . . . . . . . . . . . . . . 4 2.1. The DC Use-Case . . . . . . . . . . . . . . . . . . . . . . 5
2.2. The IXP Use-Case . . . . . . . . . . . . . . . . . . . . . 4 2.2. The IXP Use-Case . . . . . . . . . . . . . . . . . . . . . 5
3. Solution Requirements . . . . . . . . . . . . . . . . . . . . . 5 3. Solution Requirements . . . . . . . . . . . . . . . . . . . . . 6
4. Solution Description . . . . . . . . . . . . . . . . . . . . . 6 4. Solution Description . . . . . . . . . . . . . . . . . . . . . 7
4.1. Learning Sub-Function . . . . . . . . . . . . . . . . . . . 8 4.1. Learning Sub-Function . . . . . . . . . . . . . . . . . . . 9
4.1.1. Proxy-ND and the NA Flags . . . . . . . . . . . . . . . 10 4.1.1. Proxy-ND and the NA Flags . . . . . . . . . . . . . . . 10
4.2. Reply Sub-Function . . . . . . . . . . . . . . . . . . . . 11 4.2. Reply Sub-Function . . . . . . . . . . . . . . . . . . . . 11
4.3. Unicast-forward Sub-Function . . . . . . . . . . . . . . . 12 4.3. Unicast-forward Sub-Function . . . . . . . . . . . . . . . 12
4.4. Maintenance Sub-Function . . . . . . . . . . . . . . . . . 12 4.4. Maintenance Sub-Function . . . . . . . . . . . . . . . . . 13
4.5. Flooding (to Remote PEs) Reduction/Suppression . . . . . . 13 4.5. Flooding (to Remote PEs) Reduction/Suppression . . . . . . 14
4.6. Duplicate IP Detection . . . . . . . . . . . . . . . . . . 14 4.6. Duplicate IP Detection . . . . . . . . . . . . . . . . . . 14
5. Solution Benefits . . . . . . . . . . . . . . . . . . . . . . . 16 5. Solution Benefits . . . . . . . . . . . . . . . . . . . . . . . 16
6. Deployment Scenarios . . . . . . . . . . . . . . . . . . . . . 16 6. Deployment Scenarios . . . . . . . . . . . . . . . . . . . . . 17
6.1. All Dynamic Learning . . . . . . . . . . . . . . . . . . . 17 6.1. All Dynamic Learning . . . . . . . . . . . . . . . . . . . 17
6.2. Dynamic Learning with Proxy-ARP/ND . . . . . . . . . . . . 17 6.2. Dynamic Learning with Proxy-ARP/ND . . . . . . . . . . . . 17
6.3. Hybrid Dynamic Learning and Static Provisioning with 6.3. Hybrid Dynamic Learning and Static Provisioning with
Proxy-ARP/ND . . . . . . . . . . . . . . . . . . . . . . . 17 Proxy-ARP/ND . . . . . . . . . . . . . . . . . . . . . . . 18
6.4 All Static Provisioning with Proxy-ARP/ND . . . . . . . . . 18 6.4 All Static Provisioning with Proxy-ARP/ND . . . . . . . . . 18
6.5 Deployment Scenarios in IXPs . . . . . . . . . . . . . . . . 18 6.5 Deployment Scenarios in IXPs . . . . . . . . . . . . . . . . 18
6.6 Deployment Scenarios in DCs . . . . . . . . . . . . . . . . 19 6.6 Deployment Scenarios in DCs . . . . . . . . . . . . . . . . 19
7. Conventions Used in this Document . . . . . . . . . . . . . . . 19 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 20
8. Security Considerations . . . . . . . . . . . . . . . . . . . . 20 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 20
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 20 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20 9.1. Normative References . . . . . . . . . . . . . . . . . . . 20
10.1. Normative References . . . . . . . . . . . . . . . . . . . 20 9.2. Informative References . . . . . . . . . . . . . . . . . . 21
10.2. Informative References . . . . . . . . . . . . . . . . . . 21 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 22
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22
1. Terminology 1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
BUM: Broadcast, Unknown unicast and Multicast layer-2 traffic. BUM: Broadcast, Unknown unicast and Multicast layer-2 traffic.
ARP: Address Resolution Protocol. ARP: Address Resolution Protocol.
GARP: Gratuitous ARP message. GARP: Gratuitous ARP message.
ND: Neighbor Discovery Protocol. ND: Neighbor Discovery Protocol.
NS: Neighbor Solicitation message. NS: Neighbor Solicitation message.
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RT2: EVPN Route type 2 or MAC/IP Advertisement route, as per RT2: EVPN Route type 2 or MAC/IP Advertisement route, as per
[RFC7432]. [RFC7432].
MAC or IP DA: MAC or IP Destination Address. MAC or IP DA: MAC or IP Destination Address.
MAC or IP SA: MAC or IP Source Address. MAC or IP SA: MAC or IP Source Address.
AS-MAC: Anti-spoofing MAC. AS-MAC: Anti-spoofing MAC.
LAG: Link Aggregation Group.
BD: Broadcast Domain.
This document assumes familiarity with the terminology used in
[RFC7432].
2. Introduction 2. Introduction
As specified in [RFC7432] the IP Address field in the MAC/IP As specified in [RFC7432] the IP Address field in the MAC/IP
Advertisement route may optionally carry one of the IP addresses Advertisement route may optionally carry one of the IP addresses
associated with the MAC address. A PE may learn local IP->MAC pairs associated with the MAC address. A PE may learn local IP->MAC pairs
and advertise them in EVPN MAC/IP routes. The remote PEs may add and advertise them in EVPN MAC/IP routes. The remote PEs may add
those IP->MAC pairs to their Proxy-ARP/ND tables and reply to local those IP->MAC pairs to their Proxy-ARP/ND tables and reply to local
ARP requests or Neighbor Solicitations (or 'unicast-forward' those ARP requests or Neighbor Solicitations (or 'unicast-forward' those
packets to the owner MAC), reducing and even suppressing in some packets to the owner MAC), reducing and even suppressing in some
cases the flooding in the EVPN network. cases the flooding in the EVPN network.
EVPN and its associated Proxy-ARP/ND function are extremely useful in EVPN and its associated Proxy-ARP/ND function are extremely useful in
Data Centers (DCs) or Internet Exchange Points (IXPs) with large Data Centers (DCs) or Internet Exchange Points (IXPs) with large
broadcast domains, where the amount of ARP/ND flooded traffic causes broadcast domains, where the amount of ARP/ND flooded traffic causes
issues on routers and CEs. [RFC6820] describes the Address Resolution issues on routers and CEs. [RFC6820] describes the Address Resolution
problems in Large Data Center networks. problems in Large Data Center networks.
This document describes how the [RFC7432] proxy-ARP/ND function may This document describes how the [RFC7432] Proxy-ARP/ND function may
be implemented to help IXPs, DCs and other operators deal with the be implemented to help IXPs, DCs and other operators deal with the
issues derived from Address Resolution in large broadcast domains. issues derived from Address Resolution in large broadcast domains.
2.1. The DC Use-Case 2.1. The DC Use-Case
As described in [RFC6820] the IPv4 and IPv6 Address Resolution can As described in [RFC6820] the IPv4 and IPv6 Address Resolution can
create a lot of issues in large DCs. The amount of flooding that create a lot of issues in large DCs. In particular, the issues
Address Resolution creates, as well as other associated issues can be created by the IPv4 Address Resolution Protocol procedures may be
mitigated with the use of EVPN and its proxy-ARP/ND function. significant.
On one hand, ARP Requests use broadcast MAC addresses, therefore any
Tenant System in a large Broadcast Domain will see a large amount of
ARP traffic, which is not addressed to most of the receivers.
On the other hand, the flooding issue becomes even worse if some
Tenant Systems disappear from the broadcast domain, since some
implementations will persistently retry sending ARP Requests. As
[RFC6820] states, there are no clear requirements for retransmitting
ARP Requests in the absence of replies, hence an implementation may
choose to keep retrying endlessly even if there are no replies.
The amount of flooding that Address Resolution creates can be
mitigated with the use of EVPN and its Proxy-ARP/ND function.
2.2. The IXP Use-Case 2.2. The IXP Use-Case
The implementation described in this document is especially useful in The implementation described in this document is especially useful in
IXP networks. IXP networks.
A typical IXP provides access to a large layer-2 peering network, A typical IXP provides access to a large layer-2 peering network,
where (hundreds of) Internet routers are connected. Because of the where (hundreds of) Internet routers are connected. Because of the
requirement to connect all routers to a single layer-2 network the requirement to connect all routers to a single layer-2 network the
peering networks use IPv4 layer-3 addresses in length ranges from /21 peering networks use IPv4 layer-3 addresses in length ranges from /21
to /24, which can create very large broadcast domains. This peering to /24 (and even bigger for IPv6), which can create very large
network is transparent to the Customer Edge (CE) devices and broadcast domains. This peering network is transparent to the
therefore floods any ARP request or NS messages to all the CEs in the Customer Edge (CE) devices and therefore floods any ARP request or NS
network. Unsolicited GARP and NA messages are flooded to all the CEs messages to all the CEs in the network. Unsolicited GARP and NA
too. messages are flooded to all the CEs too.
In these IXP networks, most of the CEs are typically peering routers In these IXP networks, most of the CEs are typically peering routers
and roughly all the BUM traffic is originated by the ARP and ND and roughly all the BUM traffic is originated by the ARP and ND
address resolution procedures. This ARP/ND BUM traffic causes address resolution procedures. This ARP/ND BUM traffic causes
significant data volumes that reach every single router in the significant data volumes that reach every single router in the
peering network. Since the ARP/ND messages are processed in software peering network. Since the ARP/ND messages are processed in "slow
processors and they take high priority in the routers, heavy loads of path" software processors and they take high priority in the routers,
ARP/ND traffic can cause some routers to run out of resources. CEs heavy loads of ARP/ND traffic can cause some routers to run out of
disappearing from the network may cause Address Resolution explosions resources. CEs disappearing from the network may cause Address
that can make a router with limited processing power fail to keep BGP Resolution explosions that can make a router with limited processing
sessions running. power fail to keep BGP sessions running.
The issue may be better in IPv6 routers, since ND uses SN-multicast The issue may be better in IPv6 routers, since ND uses SN-multicast
address in NS messages, however ARP uses broadcast and has to be address in NS messages, however ARP uses broadcast and has to be
processed by all the routers in the network. Some routers may also be processed by all the routers in the network. Some routers may also be
configured to broadcast periodic GARPs [RFC5227]. The amount of configured to broadcast periodic GARPs [RFC5227]. The amount of
ARP/ND flooded traffic grows exponentially with the number of IXP ARP/ND flooded traffic grows exponentially with the number of IXP
participants, therefore the issue can only go worse as new CEs are participants, therefore the issue can only go worse as new CEs are
added. added.
In order to deal with this issue, IXPs have developed certain In order to deal with this issue, IXPs have developed certain
solutions over the past years. One example is the ARP-Sponge daemon solutions over the past years. One example is the ARP-Sponge daemon
[ARP-Sponge]. While these solutions may mitigate the issues of [ARP-Sponge], which can reduce significantly the amount of ARP
Address Resolution in large broadcasts domains, EVPN provides new messages sent to an absent router. While these solutions may mitigate
more efficient possibilities to IXPs. EVPN and its proxy-ARP/ND the issues of Address Resolution in large broadcasts domains, EVPN
function may help solve the issue in a distributed and scalable way, provides new more efficient possibilities to IXPs. EVPN and its
fully integrated with the PE network. Proxy-ARP/ND function may help solve the issue in a distributed and
scalable way, fully integrated with the PE network.
3. Solution Requirements 3. Solution Requirements
The distributed EVPN proxy-ARP/ND function described in this document The distributed EVPN Proxy-ARP/ND function described in this document
SHOULD meet the following requirements: meets the following requirements:
o The solution SHOULD support the learning of the CE IP->MAC entries o The solution supports the learning of the CE IP->MAC entries on the
on the EVPN PEs via the management, control or data planes. An EVPN PEs via the management, control or data planes. An
implementation SHOULD allow to intentionally enable or disable implementation should allow to intentionally enable or disable
those possible learning mechanisms. those possible learning mechanisms.
o The solution MAY suppress completely the flooding of the ARP/ND o The solution may suppress completely the flooding of the ARP/ND
messages in the EVPN network, assuming that all the CE IP->MAC messages in the EVPN network, assuming that all the CE IP->MAC
addresses local to the PEs are known or provisioned on the PEs from addresses local to the PEs are known or provisioned on the PEs from
a management system. Note that in this case, the unknown unicast a management system. Note that in this case, the unknown unicast
traffic can also be suppressed, since all the expected unicast flooded traffic can also be suppressed, since all the expected
traffic will be destined to known MAC addresses in the PE MAC-VRFs. unicast traffic will be destined to known MAC addresses in the PE
BDs.
o The solution MAY reduce significantly the flooding of the ARP/ND o The solution reduces significantly the flooding of the ARP/ND
messages in the EVPN network, assuming that some or all the CE messages in the EVPN network, assuming that some or all the CE
IP->MAC addresses are learned on the data plane by snooping ARP/ND IP->MAC addresses are learned on the data plane by snooping ARP/ND
messages issued by the CEs. messages issued by the CEs.
o The solution MAY provide a way to refresh periodically the CE o The solution provides a way to refresh periodically the CE IP->MAC
IP->MAC entries learned through the data plane, so that the IP->MAC entries learned through the data plane, so that the IP->MAC entries
entries are not withdrawn by EVPN when they age out unless the CE are not withdrawn by EVPN when they age out unless the CE is not
is not active anymore. This option helps reducing the EVPN control active anymore. This option helps reducing the EVPN control plane
plane overhead in a network with active CEs that do not send overhead in a network with active CEs that do not send packets
packets frequently. frequently.
o The solution SHOULD provide a mechanism to detect duplicate IP o The solution provides a mechanism to detect duplicate IP addresses.
addresses. In case of duplication, the detecting PE should not In case of duplication, the detecting PE should not reply to
reply to requests for the duplicate IP. Instead, the PE should requests for the duplicate IP. Instead, the PE should alert the
alert the operator and may optionally prevent any other CE from operator and may optionally prevent any other CE from sending
sending traffic to the duplicate IP. traffic to the duplicate IP.
o The solution MUST NOT change any existing behavior in the CEs o The solution should not change any existing behavior in the CEs
connected to the EVPN PEs. connected to the EVPN PEs.
4. Solution Description 4. Solution Description
Figure 1 illustrates an example EVPN network where the Proxy-ARP/ND Figure 1 illustrates an example EVPN network where the Proxy-ARP/ND
function is enabled. function is enabled.
MAC-VRF1 BD1
Proxy-ARP/ND Proxy-ARP/ND
+------------+ +------------+
IP1/M1 +----------------------------+ |IP1->M1 EVPN| IP1/M1 +----------------------------+ |IP1->M1 EVPN|
GARP --->Proxy-ARP/ND | |IP2->M2 EVPN| GARP --->Proxy-ARP/ND | |IP2->M2 EVPN|
+---+ +----+---+ RT2(IP1/M1) | |IP3->M3 sta | +---+ +----+---+ RT2(IP1/M1) | |IP3->M3 sta |
|CE1+------+MAC-VRF1| ------> +------+---|IP4->M4 dyn | |CE1+------+ BD1 | ------> +------+---|IP4->M4 dyn |
+---+ +--------+ | +------------+ +---+ +--------+ | +------------+
PE1 | +--------+ Who has IP1? PE1 | +--------+ Who has IP1?
| EVPN | |MAC-VRF1| <----- +---+ | EVPN | | BD1 | <----- +---+
| EVI1 | | | | |CE3| | EVI1 | | | | |CE3|
IP2/M2 | | | | -----> +---+ IP2/M2 | | | | -----> +---+
GARP --->Proxy-ARP/ND | +--------+ | IP1->M1 GARP --->Proxy-ARP/ND | +--------+ | IP1->M1
+---+ +--------+ RT2(IP2/M2) | | +---+ +--------+ RT2(IP2/M2) | |
|CE2+----+MAC-VRF1| ------> +--------------+ |CE2+----+ BD1 | ------> +--------------+
+---+ +--------+ PE3| +---+ +---+ +--------+ PE3| +---+
PE2 | +----+CE4| PE2 | +----+CE4|
+----------------------------+ +---+ +----------------------------+ +---+
<---IP4/M4 GARP <---IP4/M4 GARP
Figure 1 Proxy-ARP/ND network example Figure 1 Proxy-ARP/ND network example
When the Proxy-ARP/ND function is enabled in the MAC-VRFs of the EVPN When the Proxy-ARP/ND function is enabled in a BD (Broadcast Domain)
PEs, each PE creates a Proxy table specific to that MAC-VRF that can of the EVPN PEs, each PE creates a Proxy table specific to that BD
contain three types of Proxy-ARP/ND entries: that can contain three types of Proxy-ARP/ND entries:
a) Dynamic entries: learned by snooping CE's ARP and ND messages. For a) Dynamic entries: learned by snooping CE's ARP and ND messages. For
instance, IP4->M4 in Figure 1. instance, IP4->M4 in Figure 1.
b) Static entries: provisioned on the PE by the management system. b) Static entries: provisioned on the PE by the management system.
For instance, IP3->M3 in Figure 1. For instance, IP3->M3 in Figure 1.
c) EVPN-learned entries: learned from the IP/MAC information encoded c) EVPN-learned entries: learned from the IP/MAC information encoded
in the received RT2's coming from remote PEs. For instance, IP1- in the received RT2's coming from remote PEs. For instance, IP1-
>M1 and IP2->M2 in Figure 1. >M1 and IP2->M2 in Figure 1.
As a high level example, the operation of the EVPN Proxy-ARP/ND As a high level example, the operation of the EVPN Proxy-ARP/ND
function in the network of Figure 1 is described below. In this function in the network of Figure 1 is described below. In this
example we assume IP1, IP2 and IP3 are IPv4 addresses: example we assume IP1, IP2 and IP3 are IPv4 addresses:
1. Proxy-ARP/ND is enabled in MAC-VRF1 of PE1, PE2 and PE3. 1. Proxy-ARP/ND is enabled in BD1 of PE1, PE2 and PE3.
2. The PEs start adding dynamic, static and EVPN-learned entries to 2. The PEs start adding dynamic, static and EVPN-learned entries to
their Proxy tables: their Proxy tables:
a. PE3 adds IP1->M1 and IP2->M2 based on the EVPN routes received a. PE3 adds IP1->M1 and IP2->M2 based on the EVPN routes received
from PE1 and PE2. Those entries were previously learned as from PE1 and PE2. Those entries were previously learned as
dynamic entries in PE1 and PE2 respectively, and advertised in dynamic entries in PE1 and PE2 respectively, and advertised in
BGP EVPN. BGP EVPN.
b. PE3 adds IP4->M4 as dynamic. This entry is learned by snooping b. PE3 adds IP4->M4 as dynamic. This entry is learned by snooping
the corresponding ARP messages sent by CE4. the corresponding ARP messages sent by CE4.
c. An operator also provisions the static entry IP3->M3. c. An operator also provisions the static entry IP3->M3.
3. When CE3 sends an ARP Request asking for IP1, PE3 will: 3. When CE3 sends an ARP Request asking for the MAC address of IP1,
PE3 will:
a. Intercept the ARP Request and perform a Proxy-ARP lookup for a. Intercept the ARP Request and perform a Proxy-ARP lookup for
IP1. IP1.
b. If the lookup is successful (as in Figure 1), PE3 will send an b. If the lookup is successful (as in Figure 1), PE3 will send an
ARP Reply with IP1->M1. The ARP Request will not be flooded to ARP Reply with IP1->M1. The ARP Request will not be flooded to
the EVPN network or any other local CEs. the EVPN network or any other local CEs.
c. If the lookup is not successful, PE3 will flood the ARP Request c. If the lookup is not successful, PE3 will flood the ARP Request
in the EVPN network and the other local CEs. in the EVPN network and the other local CEs.
As PE3 learns more and more host entries in the Proxy-ARP/ND table, As PE3 learns more and more host entries in the Proxy-ARP/ND table,
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EVPN-learned entries MUST be learned from received valid EVPN MAC/IP EVPN-learned entries MUST be learned from received valid EVPN MAC/IP
Advertisement routes containing a MAC and IP address. Advertisement routes containing a MAC and IP address.
Dynamic entries are learned in different ways depending on whether Dynamic entries are learned in different ways depending on whether
the entry contains an IPv4 or IPv6 address: the entry contains an IPv4 or IPv6 address:
a) Proxy-ARP dynamic entries: a) Proxy-ARP dynamic entries:
They SHOULD be learned by snooping any ARP packet (Ethertype They SHOULD be learned by snooping any ARP packet (Ethertype
0x0806) received from the CEs attached to the MAC-VRF. The 0x0806) received from the CEs attached to the BD. The Learning
Learning function will add the Sender MAC and Sender IP of the function will add the Sender MAC and Sender IP of the snooped ARP
snooped ARP packet to the Proxy-ARP table. Note that MAC and IPs packet to the Proxy-ARP table. Note that MAC and IPs with value 0
with value 0 SHOULD NOT be learned. SHOULD NOT be learned.
b) Proxy-ND dynamic entries: b) Proxy-ND dynamic entries:
They SHOULD be learned out of the Target Address and TLLA They SHOULD be learned out of the Target Address and TLLA
information in NA messages (Ethertype 0x86DD, ICMPv6 type 136) information in NA messages (Ethertype 0x86DD, ICMPv6 type 136)
received from the CEs attached to the MAC-VRF. A Proxy-ND received from the CEs attached to the BD. A Proxy-ND
implementation SHOULD NOT learn IP->MAC entries from NS messages, implementation SHOULD NOT learn IP->MAC entries from NS messages,
since they don't contain the R-bit Flag required by the Proxy-ND since they don't contain the R-bit Flag required by the Proxy-ND
reply function. See section 4.1.1 for more information about the reply function. See section 4.1.1 for more information about the
R-bit flag. R-bit flag.
Note that if the O-bit is zero in the received NA message, the Note that if the O-bit is zero in the received NA message, the
IP->MAC SHOULD only be learned in case IPv6 'anycast' is enabled IP->MAC SHOULD only be learned in case IPv6 'anycast' is enabled
in the EVI. in the EVI.
The following procedure associated to the Learning sub-function is The following procedure associated to the Learning sub-function is
skipping to change at page 11, line 6 skipping to change at page 11, line 23
from the ND Extended Community received from EVPN along with the from the ND Extended Community received from EVPN along with the
RT2 used to learn the IP->MAC itself. Please refer to [EVPN-NA- RT2 used to learn the IP->MAC itself. Please refer to [EVPN-NA-
FLAGS]. If no ND extended community is received, the PE will add FLAGS]. If no ND extended community is received, the PE will add
the default R-bit/O-bit to the entry. The default R-bit SHOULD be the default R-bit/O-bit to the entry. The default R-bit SHOULD be
an administrative choice. The default O-bit SHOULD be 1. an administrative choice. The default O-bit SHOULD be 1.
Note that the O-bit SHOULD only be learned if 'anycast' is enabled in Note that the O-bit SHOULD only be learned if 'anycast' is enabled in
the EVI. If so, Duplicate IP Detection must be disabled so that the the EVI. If so, Duplicate IP Detection must be disabled so that the
PE is able to learn the same IP mapped to different MACs in the same PE is able to learn the same IP mapped to different MACs in the same
Proxy-ND table. If 'anycast' is disabled, NA messages with O-bit = 0 Proxy-ND table. If 'anycast' is disabled, NA messages with O-bit = 0
will not create a proxy-ND entry, hence no EVPN advertisement with ND will not create a Proxy-ND entry, hence no EVPN advertisement with ND
extended community will be generated. extended community will be generated.
4.2. Reply Sub-Function 4.2. Reply Sub-Function
This sub-function will reply to Address Resolution This sub-function will reply to Address Resolution
requests/solicitations upon successful lookup in the Proxy-ARP/ND requests/solicitations upon successful lookup in the Proxy-ARP/ND
table for a given IP address. The following considerations should be table for a given IP address. The following considerations should be
taken into account: taken into account:
a) When replying to ARP Request or NS messages, the PE SHOULD use the a) When replying to ARP Request or NS messages, the PE SHOULD use the
Proxy-ARP/ND entry MAC address as MAC SA. This is recommended so Proxy-ARP/ND entry MAC address as MAC SA. This is recommended so
that the resolved MAC can be learned in the MAC FIB of potential that the resolved MAC can be learned in the MAC FIB of potential
Layer-2 switches seating between the PE and the CE requesting the layer-2 switches sitting between the PE and the CE requesting the
Address Resolution. Address Resolution.
b) A PE SHOULD NOT reply to a request/solicitation received on the b) A PE SHOULD NOT reply to a request/solicitation received on the
same attachment circuit over which the IP->MAC is learned. In this same attachment circuit over which the IP->MAC is learned. In this
case the requester and the requested IP are assumed to be case the requester and the requested IP are assumed to be
connected to the same layer-2 switch/access network linked to the connected to the same layer-2 switch/access network linked to the
PE's attachment circuit, and therefore the requested IP owner will PE's attachment circuit, and therefore the requested IP owner will
receive the request directly. receive the request directly.
c) A PE SHOULD reply to broadcast/multicast Address Resolution c) A PE SHOULD reply to broadcast/multicast Address Resolution
messages, that is, ARP-Request, NS messages as well as DAD NS messages, that is, ARP-Request, NS messages as well as DAD NS
messages. A PE SHOULD NOT reply to unicast Address Resolution messages. A PE SHOULD NOT reply to unicast Address Resolution
requests (for instance, NUD NS messages). requests (for instance, NUD NS messages).
d) A PE SHOULD include the R-bit learned for the IP->MAC entry in the d) A PE SHOULD include the R-bit learned for the IP->MAC entry in the
NA messages (see section 4.1.1). The S-bit will be set/unset as NA messages (see section 4.1.1). The S-bit will be set/unset as
per [RFC4861]. The O-bit will be included if IPv6 'anycast' is per [RFC4861]. The O-bit will be included if IPv6 'anycast' is
enabled in the EVI and it is learned for the IP->MAC entry. If enabled in the EVI and it is learned for the IP->MAC entry. If
'anycast' is enabled and there are more than one MAC for a given 'anycast' is enabled and there are more than one MAC for a given
IP, the PE will reply to NS messages with as many NA responses as IP, the PE will reply to NS messages with as many NA responses as
'anycast' entries are in the proxy-ND table. 'anycast' entries are in the Proxy-ND table.
e) A PE SHOULD NOT reply to ARP probes received from the CEs. An ARP e) A PE SHOULD NOT reply to ARP probes received from the CEs. An ARP
probe is an ARP request constructed with an all-zero sender IP probe is an ARP request constructed with an all-zero sender IP
address that may be used by hosts for IPv4 Address Conflict address that may be used by hosts for IPv4 Address Conflict
Detection [RFC5227]. Detection [RFC5227].
f) A PE SHOULD only reply to ARP-Request and NS messages with the f) A PE SHOULD only reply to ARP-Request and NS messages with the
format specified in [RFC0826] and [RFC4861] respectively. Received format specified in [RFC0826] and [RFC4861] respectively. Received
ARP-Requests and NS messages with unknown options SHOULD be either ARP-Requests and NS messages with unknown options SHOULD be either
forwarded (as unicast packets) to the owner of the requested IP forwarded (as unicast packets) to the owner of the requested IP
(assuming the MAC is known in the proxy-ARP/ND table and MAC-VRF) (assuming the MAC is known in the Proxy-ARP/ND table and BD) or
or discarded. An administrative option to control this behavior discarded. An administrative option to control this behavior
('unicast-forward' or 'discard') SHOULD be supported. The ('unicast-forward' or 'discard') SHOULD be supported. The
'unicast-forward' option is described in section 4.3. 'unicast-forward' option is described in section 4.3.
4.3. Unicast-forward Sub-Function 4.3. Unicast-forward Sub-Function
As discussed in section 4.2. in some cases the operator may want to As discussed in section 4.2. in some cases the operator may want to
'unicast-forward' certain ARP-Request and NS messages as opposed to 'unicast-forward' certain ARP-Request and NS messages as opposed to
reply to them. The operator SHOULD be able to activate this option reply to them. The operator SHOULD be able to activate this option
with one of the following parameters: with one of the following parameters:
a) unicast-forward always a) unicast-forward always
b) unicast-forward unknown-options b) unicast-forward unknown-options
If 'unicast-forward always' is enabled, the PE will perform a proxy- If 'unicast-forward always' is enabled, the PE will perform a Proxy-
ARP/ND table lookup and in case of a hit, the PE will forward the ARP/ND table lookup and in case of a hit, the PE will forward the
packet to the owner of the MAC found in the proxy-ARP/ND table. This packet to the owner of the MAC found in the Proxy-ARP/ND table. This
is irrespective of the options carried in the ARP/ND packet. This is irrespective of the options carried in the ARP/ND packet. This
option provides total transparency in the EVI and yet reduces the option provides total transparency in the EVI and yet reduces the
amount of flooding significantly. amount of flooding significantly.
If 'unicast-forward unknown-options' is enabled, upon a successful If 'unicast-forward unknown-options' is enabled, upon a successful
proxy-ARP/ND lookup, the PE will perform a 'unicast-forward' action Proxy-ARP/ND lookup, the PE will perform a 'unicast-forward' action
only if the ARP-Request or NS messages carry unknown options, as only if the ARP-Request or NS messages carry unknown options, as
explained in section 4.2. As an example, this would allow to enable explained in section 4.2. As an example, this would allow to enable
proxy-ND and Secure ND [RFC3971] in the same EVI. The 'unicast- Proxy-ND and Secure ND [RFC3971] in the same EVI. The 'unicast-
forward unknown-options' configuration allows the support of new forward unknown-options' configuration allows the support of new
applications using ARP/ND in the EVI while still reducing the applications using ARP/ND in the EVI while still reducing the
flooding at the same time. flooding at the same time.
4.4. Maintenance Sub-Function 4.4. Maintenance Sub-Function
The Proxy-ARP/ND tables SHOULD follow a number of maintenance The Proxy-ARP/ND tables SHOULD follow a number of maintenance
procedures so that the dynamic IP->MAC entries are kept if the owner procedures so that the dynamic IP->MAC entries are kept if the owner
is active and flushed if the owner is no longer in the network. The is active and flushed if the owner is no longer in the network. The
following procedures are recommended: following procedures are recommended:
a) Age-time a) Age-time
A dynamic Proxy-ARP/ND entry SHOULD be flushed out of the table if A dynamic Proxy-ARP/ND entry MUST be flushed out of the table if
the IP->MAC has not been refreshed within a given age-time. The the IP->MAC has not been refreshed within a given age-time. The
entry is refreshed if an ARP or NA message is received for the entry is refreshed if an ARP or NA message is received for the
same IP->MAC entry. The age-time is an administrative option and same IP->MAC entry. The age-time is an administrative option and
its value should be carefully chosen depending on the specific its value should be carefully chosen depending on the specific
use-case: in IXP networks (where the CE routers are fairly static) use-case: in IXP networks (where the CE routers are fairly static)
the age-time may normally be longer than in DC networks (where the age-time may normally be longer than in DC networks (where
mobility is required). mobility is required).
b) Send-refresh option b) Send-refresh option
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MAC. MAC.
The refresh request messages should be sent only for dynamic The refresh request messages should be sent only for dynamic
entries and not for static or EVPN-learned entries. Even though entries and not for static or EVPN-learned entries. Even though
the refresh request messages are broadcast or multicast, the PE the refresh request messages are broadcast or multicast, the PE
SHOULD only send the message to the attachment circuit associated SHOULD only send the message to the attachment circuit associated
to the MAC in the IP->MAC entry. to the MAC in the IP->MAC entry.
The age-time and send-refresh options are used in EVPN networks to The age-time and send-refresh options are used in EVPN networks to
avoid unnecessary EVPN RT2 withdrawals: if refresh messages are sent avoid unnecessary EVPN RT2 withdrawals: if refresh messages are sent
before the corresponding MAC-VRF FIB and Proxy-ARP/ND age-time for a before the corresponding BD FIB and Proxy-ARP/ND age-time for a given
given entry expires, inactive but existing hosts will reply, entry expires, inactive but existing hosts will reply, refreshing the
refreshing the entry and therefore avoiding unnecessary MAC and MAC- entry and therefore avoiding unnecessary MAC and MAC-IP withdrawals
IP withdrawals in EVPN. Both entries (MAC in the MAC-VRF and IP->MAC in EVPN. Both entries (MAC in the BD and IP->MAC in Proxy-ARP/ND) are
in Proxy-ARP/ND) are reset when the owner replies to the ARP/ND reset when the owner replies to the ARP/ND probe. If there is no
probe. If there is no response to the ARP/ND probe, the MAC and response to the ARP/ND probe, the MAC and IP->MAC entries will be
IP->MAC entries will be legitimately flushed and the RT2s withdrawn. legitimately flushed and the RT2s withdrawn.
4.5. Flooding (to Remote PEs) Reduction/Suppression 4.5. Flooding (to Remote PEs) Reduction/Suppression
The Proxy-ARP/ND function implicitly helps reducing the flooding of The Proxy-ARP/ND function implicitly helps reducing the flooding of
ARP Request and NS messages to remote PEs in an EVPN network. ARP Request and NS messages to remote PEs in an EVPN network.
However, in certain use-cases, the flooding of ARP/NS/NA messages However, in certain use-cases, the flooding of ARP/NS/NA messages
(and even the unknown unicast flooding) to remote PEs can be (and even the unknown unicast flooding) to remote PEs can be
suppressed completely in an EVPN network. suppressed completely in an EVPN network.
For instance, in an IXP network, since all the participant CEs are For instance, in an IXP network, since all the participant CEs are
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The Proxy-ARP/ND function SHOULD support duplicate IP detection so The Proxy-ARP/ND function SHOULD support duplicate IP detection so
that ARP/ND-spoofing attacks or duplicate IPs due to human errors can that ARP/ND-spoofing attacks or duplicate IPs due to human errors can
be detected. be detected.
ARP/ND spoofing is a technique whereby an attacker sends "fake" ARP/ND spoofing is a technique whereby an attacker sends "fake"
ARP/ND messages onto a broadcast domain. Generally the aim is to ARP/ND messages onto a broadcast domain. Generally the aim is to
associate the attacker's MAC address with the IP address of another associate the attacker's MAC address with the IP address of another
host causing any traffic meant for that IP address to be sent to the host causing any traffic meant for that IP address to be sent to the
attacker instead. attacker instead.
The distributed nature of EVPN and proxy-ARP/ND allows the easy The distributed nature of EVPN and Proxy-ARP/ND allows the easy
detection of duplicated IPs in the network, in a similar way to the detection of duplicated IPs in the network, in a similar way to the
MAC duplication function supported by [RFC7432] for MAC addresses. MAC duplication function supported by [RFC7432] for MAC addresses.
Duplicate IP detection monitors "IP-moves" in the Proxy-ARP/ND table Duplicate IP detection monitors "IP-moves" in the Proxy-ARP/ND table
in the following way: in the following way:
o When an existing active IP1->MAC1 entry is modified, a PE starts an o When an existing active IP1->MAC1 entry is modified, a PE starts an
M-second timer (default value of M=180), and if it detects N IP M-second timer (default value of M=180), and if it detects N IP
moves before the timer expires (default value of N=5), it concludes moves before the timer expires (default value of N=5), it concludes
that a duplicate IP situation has occurred. An IP move is that a duplicate IP situation has occurred. An IP move is
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IP within the M timer: IP within the M timer:
- If the IP1->MAC1 pair was previously owned by the spoofer and the - If the IP1->MAC1 pair was previously owned by the spoofer and the
new IP1->MAC2 was from a valid CE, then the issued CONFIRM new IP1->MAC2 was from a valid CE, then the issued CONFIRM
message would trigger a response from the spoofer. message would trigger a response from the spoofer.
- If it were the other way around, that is, IP1->MAC1 was - If it were the other way around, that is, IP1->MAC1 was
previously owned by a valid CE, the CONFIRM message would trigger previously owned by a valid CE, the CONFIRM message would trigger
a response from the CE. a response from the CE.
Either way, if this process continues, then duplicate detection Either way, if this process continues, then duplicate detection
will kick in. will kick in.
o Upon detecting a duplicate IP situation: o Upon detecting a duplicate IP situation:
a) The entry in duplicate detected state cannot be updated with new a) The entry in duplicate detected state cannot be updated with new
dynamic or EVPN-learned entries for the same IP. The operator dynamic or EVPN-learned entries for the same IP. The operator
MAY override the entry though with a static IP->MAC. MAY override the entry though with a static IP->MAC.
b) The PE SHOULD alert the operator and stop responding ARP/NS for b) The PE SHOULD alert the operator and stop responding ARP/NS for
the duplicate IP until a corrective action is taken. the duplicate IP until a corrective action is taken.
c) Optionally the PE MAY associate an "anti-spoofing-mac" (AS-MAC) c) Optionally the PE MAY associate an "anti-spoofing-mac" (AS-MAC)
to the duplicate IP. The PE will send a GARP/unsolicited-NA to the duplicate IP. The PE will send a GARP/unsolicited-NA
message with IP1->AS-MAC to the local CEs as well as an RT2 message with IP1->AS-MAC to the local CEs as well as an RT2
(with IP1->AS-MAC) to the remote PEs. This will force all the (with IP1->AS-MAC) to the remote PEs. This will force all the
CEs in the EVI to use the AS-MAC as MAC DA for IP1, and prevent CEs in the EVI to use the AS-MAC as MAC DA for IP1, and prevent
the spoofer from attracting any traffic for IP1. Since the AS- the spoofer from attracting any traffic for IP1. Since the AS-
MAC is a managed MAC address known by all the PEs in the EVI, MAC is a managed MAC address known by all the PEs in the EVI,
all the PEs MAY apply filters to drop and/or log any frame with all the PEs MAY apply filters to drop and/or log any frame with
MAC DA= AS-MAC. The advertisement of the AS-MAC as a "black-hole MAC DA= AS-MAC. The advertisement of the AS-MAC as a "black-hole
MAC" that can be used directly in the MAC-VRF to drop frames is MAC" that can be used directly in the BD to drop frames is for
for further study. further study.
o The duplicate IP situation will be cleared when a corrective action o The duplicate IP situation will be cleared when a corrective action
is taken by the operator, or alternatively after a HOLD-DOWN timer is taken by the operator, or alternatively after a HOLD-DOWN timer
(default value of 540 seconds). (default value of 540 seconds).
The values of M, N and HOLD-DOWN timer SHOULD be a configurable The values of M, N and HOLD-DOWN timer SHOULD be a configurable
administrative option to allow for the required flexibility in administrative option to allow for the required flexibility in
different scenarios. different scenarios.
For Proxy-ND, Duplicate IP Detection SHOULD only monitor IP moves for For Proxy-ND, Duplicate IP Detection SHOULD only monitor IP moves for
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d) The solution provides a mechanism to detect duplicate IP addresses d) The solution provides a mechanism to detect duplicate IP addresses
and avoid ARP/ND-spoof attacks or the effects of duplicate and avoid ARP/ND-spoof attacks or the effects of duplicate
addresses due to human errors. addresses due to human errors.
6. Deployment Scenarios 6. Deployment Scenarios
Four deployment scenarios with different levels of ARP/ND control are Four deployment scenarios with different levels of ARP/ND control are
available to operators using this solution, depending on their available to operators using this solution, depending on their
requirements to manage ARP/ND: all dynamic learning, all dynamic requirements to manage ARP/ND: all dynamic learning, all dynamic
learning with proxy-ARP/ND, hybrid dynamic learning and static learning with Proxy-ARP/ND, hybrid dynamic learning and static
provisioning with proxy-ARP/ND, and all static provisioning with provisioning with Proxy-ARP/ND, and all static provisioning with
proxy-ARP/ND. Proxy-ARP/ND.
6.1. All Dynamic Learning 6.1. All Dynamic Learning
In this scenario for minimum security and mitigation, EVPN is In this scenario for minimum security and mitigation, EVPN is
deployed in the peering network with the proxy-ARP/ND function deployed in the peering network with the Proxy-ARP/ND function
shutdown. PEs do not intercept ARP/ND requests and flood all shutdown. PEs do not intercept ARP/ND requests and flood all
requests, as in a conventional layer-2 network. While no ARP/ND requests, as in a conventional layer-2 network. While no ARP/ND
mitigation is used in this scenario, the IXP can still take advantage mitigation is used in this scenario, the IXP can still take advantage
of EVPN features such as control plane learning and all-active of EVPN features such as control plane learning and all-active
multihoming in the peering network. Existing mitigation solutions, multihoming in the peering network. Existing mitigation solutions,
such as the ARP-Sponge daemon [ARP-Sponge] MAY also be used in this such as the ARP-Sponge daemon [ARP-Sponge] MAY also be used in this
scenario. scenario.
Although this option does not require any of the procedures described Although this option does not require any of the procedures described
in this document, it is added as baseline/default option for in this document, it is added as baseline/default option for
completeness. This option is equivalent to VPLS as far as ARP/ND is completeness. This option is equivalent to VPLS as far as ARP/ND is
concerned. The options described in 6.2, 6.3 and 6.4 are only concerned. The options described in 6.2, 6.3 and 6.4 are only
possible in EVPN networks in combination with their Proxy-ARP/ND possible in EVPN networks in combination with their Proxy-ARP/ND
capabilities. capabilities.
6.2. Dynamic Learning with Proxy-ARP/ND 6.2. Dynamic Learning with Proxy-ARP/ND
This scenario minimizes flooding while enabling dynamic learning of This scenario minimizes flooding while enabling dynamic learning of
IP->MAC entries. The Proxy-ARP/ND function is enabled in the MAC-VRFs IP->MAC entries. The Proxy-ARP/ND function is enabled in the BDs of
of the EVPN PEs, so that the PEs intercept and respond to CE the EVPN PEs, so that the PEs intercept and respond to CE requests.
requests.
The solution MAY further reduce the flooding of the ARP/ND messages The solution MAY further reduce the flooding of the ARP/ND messages
in the EVPN network by snooping ARP/ND messages issued by the CEs. in the EVPN network by snooping ARP/ND messages issued by the CEs.
PEs will flood requests if the entry is not in their Proxy table. Any PEs will flood requests if the entry is not in their Proxy table. Any
unknown source MAC->IP entries will be learnt and advertised in EVPN, unknown source MAC->IP entries will be learnt and advertised in EVPN,
and traffic to unknown entries is discarded at the ingress PE. and traffic to unknown entries is discarded at the ingress PE.
6.3. Hybrid Dynamic Learning and Static Provisioning with Proxy-ARP/ND 6.3. Hybrid Dynamic Learning and Static Provisioning with Proxy-ARP/ND
skipping to change at page 18, line 11 skipping to change at page 18, line 25
In this scenario, static entries are provisioned from the management In this scenario, static entries are provisioned from the management
plane for protected MAC->IP addresses, and dynamic learning with plane for protected MAC->IP addresses, and dynamic learning with
Proxy-ARP/ND is enabled as described in section 6.2 on the peering Proxy-ARP/ND is enabled as described in section 6.2 on the peering
network. network.
6.4 All Static Provisioning with Proxy-ARP/ND 6.4 All Static Provisioning with Proxy-ARP/ND
For a solution that maximizes security and eliminates flooding and For a solution that maximizes security and eliminates flooding and
unknown unicast in the peering network, all MAC-IP entries are unknown unicast in the peering network, all MAC-IP entries are
provisioned from the management plane. The Proxy-ARP/ND function is provisioned from the management plane. The Proxy-ARP/ND function is
enabled in the MAC-VRFs of the EVPN PEs, so that the PEs intercept enabled in the BDs of the EVPN PEs, so that the PEs intercept and
and respond to CE requests. Dynamic learning and ARP/ND snooping is respond to CE requests. Dynamic learning and ARP/ND snooping is
disabled so that traffic to unknown entries is discarded at the disabled so that traffic to unknown entries is discarded at the
ingress PE. This scenario provides and IXP the most control over ingress PE. This scenario provides an IXP the most control over
MAC->IP entries and allows an IXP to manage all entries from a MAC->IP entries and allows an IXP to manage all entries from a
management system. management system.
6.5 Deployment Scenarios in IXPs 6.5 Deployment Scenarios in IXPs
Nowadays, almost all IXPs installed some security rules in order to Nowadays, almost all IXPs installed some security rules in order to
protect the IXP-LAN. These rules are often called port security. Port protect the IXP-LAN. These rules are often called port security. Port
security summarizes different operational steps that limit the access security summarizes different operational steps that limit the access
to the IXP-LAN, to the customer router and controls the kind of to the IXP-LAN, to the customer router and controls the kind of
traffic that the routers are allowed to be exchange (e.g., Ethernet, traffic that the routers are allowed to be exchange (e.g., Ethernet,
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DCs normally have different requirements than IXPs in terms of Proxy- DCs normally have different requirements than IXPs in terms of Proxy-
ARP/ND. Some differences are listed below: ARP/ND. Some differences are listed below:
a) The required mobility in virtualized DCs makes the "Dynamic a) The required mobility in virtualized DCs makes the "Dynamic
Learning" or "Hybrid Dynamic and Static Provisioning" models more Learning" or "Hybrid Dynamic and Static Provisioning" models more
appropriate than the "All Static Provisioning" model. appropriate than the "All Static Provisioning" model.
b) IPv6 'anycast' may be required in DCs, while it is not a b) IPv6 'anycast' may be required in DCs, while it is not a
requirement in IXP networks. Therefore if the DC needs IPv6 requirement in IXP networks. Therefore if the DC needs IPv6
'anycast' it will be explicitly enabled in the proxy-ND function, 'anycast' it will be explicitly enabled in the Proxy-ND function,
hence the proxy-ND sub-functions modified accordingly. For hence the Proxy-ND sub-functions modified accordingly. For
instance, if IPv6 'anycast' is enabled in the proxy-ND function, instance, if IPv6 'anycast' is enabled in the Proxy-ND function,
Duplicate IP Detection must be disabled. Duplicate IP Detection must be disabled.
c) DCs may require special options on ARP/ND as opposed to the c) DCs may require special options on ARP/ND as opposed to the
Address Resolution function, which is the only one typically Address Resolution function, which is the only one typically
required in IXPs. Based on that, the Reply Sub-function may be required in IXPs. Based on that, the Reply Sub-function may be
modified to forward or discard unknown options. modified to forward or discard unknown options.
7. Conventions Used in this Document 7. Security Considerations
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 [RFC2119].
In this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to be
interpreted as carrying RFC-2119 significance.
In this document, the characters ">>" preceding an indented line(s) The procedures in this document reduce the amount of ARP/ND message
indicates a compliance requirement statement using the key words flooding, which in itself provides a protection to "slow path"
listed above. This convention aids reviewers in quickly identifying software processors of routers and Tenant Systems in large BDs. The
or finding the explicit compliance requirements of this RFC. ARP/ND requests that are replied by the Proxy-ARP/ND function (hence
not flooded) are normally targeted to existing hosts in the BD.
ARP/ND requests targeted to absent hosts are still normally flooded,
however the suppression of Unknown ARP-Requests and NS messages
described in Section 4.5. can provide an additional level of security
against ARP-Requests/NS messages issued to non-existing hosts.
8. Security Considerations The solution also provides protection against Denial Of Service
attacks that use ARP/ND-spoofing as a first step. The Duplicate IP
Detection and the use of an AS-MAC as explained in Section 4.6. will
definitely protect the BD against ARP/ND spoofing.
When EVPN and its associated Proxy-ARP/ND function are used in IXP When EVPN and its associated Proxy-ARP/ND function are used in IXP
networks, they only provide ARP/ND security and mitigation. IXPs MUST networks, they provide ARP/ND security and mitigation. IXPs MUST
still employ security mechanisms that protect the peering network and still employ additional security mechanisms that protect the peering
SHOULD follow established BCPs such as the ones described in [Euro-IX network and SHOULD follow established BCPs such as the ones described
BCP]. in [Euro-IX BCP].
For example, IXPs should disable all unneeded control protocols, and For example, IXPs should disable all unneeded control protocols, and
block unwanted protocols from CEs so that only IPv4, ARP and IPv6 block unwanted protocols from CEs so that only IPv4, ARP and IPv6
Ethertypes are permitted on the peering network. In addition, port Ethertypes are permitted on the peering network. In addition, port
security features and ACLs can provide an additional level of security features and ACLs can provide an additional level of
security. security.
9. IANA Considerations 8. IANA Considerations
No IANA considerations. No IANA considerations.
10. References 9. References
10.1. Normative References 9.1. Normative References
[RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based Ethernet Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based Ethernet
VPN", RFC 7432, DOI 10.17487/RFC7432, February 2015, VPN", RFC 7432, DOI 10.17487/RFC7432, February 2015,
<https://www.rfc-editor.org/info/rfc7432>. <https://www.rfc-editor.org/info/rfc7432>.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, DOI "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, DOI
10.17487/RFC4861, September 2007, <https://www.rfc- 10.17487/RFC4861, September 2007, <https://www.rfc-
editor.org/info/rfc4861>. editor.org/info/rfc4861>.
skipping to change at page 21, line 31 skipping to change at page 21, line 42
[RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based Ethernet Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based Ethernet
VPN", RFC 7432, DOI 10.17487/RFC7432, February 2015, VPN", RFC 7432, DOI 10.17487/RFC7432, February 2015,
<https://www.rfc-editor.org/info/rfc7432>. <https://www.rfc-editor.org/info/rfc7432>.
[RFC5227] Cheshire, S., "IPv4 Address Conflict Detection", RFC 5227, [RFC5227] Cheshire, S., "IPv4 Address Conflict Detection", RFC 5227,
DOI 10.17487/RFC5227, July 2008, <https://www.rfc- DOI 10.17487/RFC5227, July 2008, <https://www.rfc-
editor.org/info/rfc5227>. editor.org/info/rfc5227>.
10.2. Informative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March
1997, <http://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC2119
Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017,
<http://www.rfc-editor.org/info/rfc8174>.
9.2. Informative References
[ARP-Sponge] Wessel M. and Sijm N., Universiteit van Amsterdam, [ARP-Sponge] Wessel M. and Sijm N., Universiteit van Amsterdam,
"Effects of IPv4 and IPv6 address resolution on AMS-IX and the ARP "Effects of IPv4 and IPv6 address resolution on AMS-IX and the ARP
Sponge", July 2009. Sponge", July 2009.
[EVPN-ND-FLAGS] Sathappan S., Nagaraj K. and Rabadan J., "Propagation [EVPN-ND-FLAGS] Sathappan S., Nagaraj K. and Rabadan J., "Propagation
of IPv6 Neighbor Advertisement Flags in EVPN", draft-ietf-bess-evpn- of IPv6 Neighbor Advertisement Flags in EVPN", draft-ietf-bess-evpn-
na-flags-00, Work in Progress, October 2017. na-flags-02, Work in Progress, October 2018.
[Euro-IX BCP] https://www.euro-ix.net/pages/28/1/bcp_ixp.html [Euro-IX BCP] https://www.euro-ix.net/pages/28/1/bcp_ixp.html
11. Acknowledgments 10. Acknowledgments
The authors want to thank Ranganathan Boovaraghavan, Sriram The authors want to thank Ranganathan Boovaraghavan, Sriram
Venkateswaran, Manish Krishnan, Seshagiri Venugopal, Tony Przygienda, Venkateswaran, Manish Krishnan, Seshagiri Venugopal, Tony Przygienda,
Robert Raszuk and Iftekhar Hussain for their review and Robert Raszuk and Iftekhar Hussain for their review and
contributions. Thank you to Oliver Knapp as well, for his detailed contributions. Thank you to Oliver Knapp as well, for his detailed
review. review.
Authors' Addresses Authors' Addresses
Jorge Rabadan (Editor) Jorge Rabadan (Editor)
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