Applicability of EVPN to NVO3 Networks
draft-ietf-nvo3-evpn-applicability-05
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 9469.
|
|
|---|---|---|---|
| Authors | Jorge Rabadan , Matthew Bocci , Sami Boutros , Ali Sajassi | ||
| Last updated | 2023-04-27 (Latest revision 2022-09-01) | ||
| Replaces | draft-rabadan-nvo3-evpn-applicability | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
GENART Last Call review
(of
-04)
by Reese Enghardt
Ready w/nits
|
||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Sam Aldrin | ||
| Shepherd write-up | Show Last changed 2019-10-07 | ||
| IESG | IESG state | Became RFC 9469 (Informational) | |
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | Andrew Alston | ||
| Send notices to | Sam Aldrin <aldrin.ietf@gmail.com> | ||
| IANA | IANA review state | IANA OK - No Actions Needed |
draft-ietf-nvo3-evpn-applicability-05
NVO3 Workgroup J. Rabadan, Ed.
Internet-Draft M. Bocci
Intended status: Informational Nokia
Expires: 5 March 2023 S. Boutros
Ciena
A. Sajassi
Cisco
1 September 2022
Applicability of EVPN to NVO3 Networks
draft-ietf-nvo3-evpn-applicability-05
Abstract
In Network Virtualization Over Layer-3 (NVO3) networks, Network
Virtualization Edge devices (NVEs) sit at the edge of the underlay
network and provide Layer-2 and Layer-3 connectivity among Tenant
Systems (TSes) of the same tenant. The NVEs need to build and
maintain mapping tables so that they can deliver encapsulated packets
to their intended destination NVE(s). While there are different
options to create and disseminate the mapping table entries, NVEs may
exchange that information directly among themselves via a control-
plane protocol, such as Ethernet Virtual Private Network (EVPN).
EVPN provides an efficient, flexible and unified control-plane option
that can be used for Layer-2 and Layer-3 Virtual Network (VN) service
connectivity. This document describes the applicability of EVPN to
NVO3 networks and how EVPN solves the challenges in those networks.
This document does not introduce any new procedures in EVPN.
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 documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 5 March 2023.
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Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. EVPN and NVO3 Terminology . . . . . . . . . . . . . . . . . . 3
3. Why is EVPN Needed in NVO3 Networks? . . . . . . . . . . . . 7
4. Applicability of EVPN to NVO3 Networks . . . . . . . . . . . 9
4.1. EVPN Route Types Used in NVO3 Networks . . . . . . . . . 9
4.2. EVPN Basic Applicability for Layer-2 Services . . . . . . 10
4.2.1. Auto-Discovery and Auto-Provisioning . . . . . . . . 12
4.2.2. Remote NVE Auto-Discovery . . . . . . . . . . . . . . 13
4.2.3. Distribution of Tenant MAC and IP Information . . . . 14
4.3. EVPN Basic Applicability for Layer-3 Services . . . . . . 14
4.4. EVPN as Control Plane for NVO3 Encapsulations and
GENEVE . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.5. EVPN OAM and Application to NVO3 . . . . . . . . . . . . 18
4.6. EVPN as the Control Plane for NVO3 Security . . . . . . . 18
4.7. Advanced EVPN Features for NVO3 Networks . . . . . . . . 18
4.7.1. Virtual Machine (VM) Mobility . . . . . . . . . . . . 18
4.7.2. MAC Protection, Duplication Detection and Loop
Protection . . . . . . . . . . . . . . . . . . . . . 19
4.7.3. Reduction/Optimization of BUM Traffic in Layer-2
Services . . . . . . . . . . . . . . . . . . . . . . 19
4.7.4. Ingress Replication (IR) Optimization for BUM
Traffic . . . . . . . . . . . . . . . . . . . . . . . 20
4.7.5. EVPN Multi-Homing . . . . . . . . . . . . . . . . . . 21
4.7.6. EVPN Recursive Resolution for Inter-Subnet Unicast
Forwarding . . . . . . . . . . . . . . . . . . . . . 22
4.7.7. EVPN Optimized Inter-Subnet Multicast Forwarding . . 23
4.7.8. Data Center Interconnect (DCI) . . . . . . . . . . . 24
5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 24
6. Conventions Used in this Document . . . . . . . . . . . . . . 24
7. Security Considerations . . . . . . . . . . . . . . . . . . . 25
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
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9.1. Normative References . . . . . . . . . . . . . . . . . . 25
9.2. Informative References . . . . . . . . . . . . . . . . . 25
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 29
Appendix B. Contributors . . . . . . . . . . . . . . . . . . . . 29
Appendix C. Authors' Addresses . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29
1. Introduction
In Network Virtualization Over Layer-3 (NVO3) networks, Network
Virtualization Edge devices (NVEs) sit at the edge of the underlay
network and provide Layer-2 and Layer-3 connectivity among Tenant
Systems (TSes) of the same tenant. The NVEs need to build and
maintain mapping tables so that they can deliver encapsulated packets
to their intended destination NVE(s). While there are different
options to create and disseminate the mapping table entries, NVEs may
exchange that information directly among themselves via a control-
plane protocol, such as EVPN. EVPN provides an efficient, flexible
and unified control-plane option that can be used for Layer-2 and
Layer-3 Virtual Network (VN) service connectivity. This document
does not introduce any new procedures in EVPN.
In this document, we assume that the EVPN control-plane module
resides in the NVEs. The NVEs can be virtual switches in
hypervisors, TOR/Leaf switches or Data Center Gateways. As described
in [RFC7365], Network Virtualization Authorities (NVAs) may be used
to provide the forwarding information to the NVEs, and in that case,
EVPN could be used to disseminate the information across multiple
federated NVAs. The applicability of EVPN would then be similar to
the one described in this document. However, for simplicity, the
description assumes control-plane communication among NVE(s).
2. EVPN and NVO3 Terminology
This document uses the terminology of [RFC7365], in addition to the
terms that follow.
* AC: Attachment Circuit or logical interface associated to a given
BT. To determine the AC on which a packet arrived, the NVE will
examine the physical/logical port and/or VLAN tags (where the VLAN
tags can be individual c-tags, s-tags or ranges of both).
* ARP and ND: Address Resolution Protocol (IPv4) and Neighbor
Discovery protocol (IPv6).
* BD: or Broadcast Domain, it corresponds to a tenant IP subnet. If
no suppression techniques are used, a BUM frame that is injected
in a Broadcast Domain will reach all the NVEs that are attached to
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that Broadcast Domain. An EVI may contain one or multiple
Broadcast Domains depending on the service model [RFC7432]. This
document will use the term Broadcast Domain to refer to a tenant
subnet.
* BT: a Bridge Table, as defined in [RFC7432]. A BT is the
instantiation of a Broadcast Domain in an NVE. When there is a
single Broadcast Domain on a given EVI, the MAC-VRF is equivalent
to the BT on that NVE. Although a Broadcast Domain spans multiple
NVEs, and a BT is really the instantiation of a Broadcast Domain
in an NVE, this document uses BT and Broadcast Domain
interchangeably.
* BUM: Broadcast, Unknown unicast and Multicast frames.
* CLOS: a multistage network topology described in [CLOS1953], where
all the edge switches (or Leafs) are connected to all the core
switches (or Spines). Typically used in Data Centers.
* DF and NDF: they refer to Designated Forwarder and Non-Designated
Forwarder, which are the roles that a given PE can have in a given
ES.
* ECMP: Equal Cost Multi-Path.
* EVPN: Ethernet Virtual Private Networks, as described in
[RFC7432].
* EVI: EVPN Instance.
* EVPN VLAN-based service model: one of the three service models
defined in [RFC7432]. It is characterized as a Broadcast Domain
that uses a single VLAN per physical access port to attach tenant
traffic to the Broadcast Domain. In this service model, there is
only one Broadcast Domain per EVI.
* EVPN VLAN-bundle service model: similar to VLAN-based but uses a
bundle of VLANs per physical port to attach tenant traffic to the
Broadcast Domain. As in VLAN-based, in this model there is a
single Broadcast Domain per EVI.
* EVPN VLAN-aware bundle service model: similar to the VLAN-bundle
model but each individual VLAN value is mapped to a different
Broadcast Domain. In this model there are multiple Broadcast
Domains per EVI for a given tenant. Each Broadcast Domain is
identified by an "Ethernet Tag", that is a control-plane value
that identifies the routes for the Broadcast Domain within the
EVI.
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* ES: Ethernet Segment. When a Tenant System (TS) is connected to
one or more NVEs via a set of Ethernet links, then that set of
links is referred to as an 'Ethernet segment'. Each ES is
represented by a unique Ethernet Segment Identifier (ESI) in the
NVO3 network and the ESI is used in EVPN routes that are specific
to that ES.
* Ethernet Tag: Used to represent a Broadcast Domain that is
configured on a given ES for the purpose of Designated Forwarder
election. Note that any of the following may be used to represent
a Broadcast Domain: VIDs (including Q-in-Q tags), configured IDs,
VNIs (Virtual Extensible Local Area Network (VXLAN) Network
Identifiers), normalized VIDs, I-SIDs (Service Instance
Identifiers), etc., as long as the representation of the Broadcast
Domains is configured consistently across the multihomed PEs
attached to that ES. The Ethernet Tag value MUST be different
from zero.
* EVI: or EVPN Instance. It is a Layer-2 Virtual Network that uses
an EVPN control-plane to exchange reachability information among
the member NVEs. It corresponds to a set of MAC-VRFs of the same
tenant. See MAC-VRF in this section.
* GENEVE: Generic Network Virtualization Encapsulation, an NVO3
encapsulation defined in [RFC8926].
* IP-VRF: an IP Virtual Routing and Forwarding table, as defined in
[RFC4364]. It stores IP Prefixes that are part of the tenant's IP
space, and are distributed among NVEs of the same tenant by EVPN.
Route-Distinghisher (RD) and Route-Target(s) (RTs) are required
properties of an IP-VRF. An IP-VRF is instantiated in an NVE for
a given tenant, if the NVE is attached to multiple subnets of the
tenant and local inter-subnet-forwarding is required across those
subnets.
* IRB: Integrated Routing and Bridging interface. It refers to the
logical interface that connects a Broadcast Domain instance (or a
BT) to an IP- VRF and allows to forward packets with destination
in a different subnet.
* MAC-VRF: a MAC Virtual Routing and Forwarding table, as defined in
[RFC7432]. The instantiation of an EVI (EVPN Instance) in an NVE.
Route Distinghisher (RD) and Route Target(s) (RTs) are required
properties of a MAC-VRF and they are normally different than the
ones defined in the associated IP-VRF (if the MAC-VRF has an IRB
interface).
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* NVE: Network Virtualization Edge device, a network entity that
sits at the edge of an underlay network and implements Layer-2
and/or Layer-3 network virtualization functions. The network-
facing side of the NVE uses the underlying Layer-3 network to
tunnel tenant frames to and from other NVEs. The tenant-facing
side of the NVE sends and receives Ethernet frames to and from
individual Tenant Systems. In this document, an NVE could be
implemented as a virtual switch within a hypervisor, a switch or a
router, and runs EVPN in the control-plane.
* NVO3 tunnels: Network Virtualization Over Layer-3 tunnels. In
this document, NVO3 tunnels or simply Overlay tunnels will be used
interchangeably. Both terms refer to a way to encapsulate tenant
frames or packets into IP packets whose IP Source Addresses (SA)
or Destination Addresses (DA) belong to the underlay IP address
space, and identify NVEs connected to the same underlay network.
Examples of NVO3 tunnel encapsulations are VXLAN [RFC7348], GENEVE
[RFC8926] or MPLSoUDP [RFC7510].
* PE: Provider Edge router.
* PMSI: Provider Multicast Service Interface.
* PTA: Provider Multicast Service Interface Tunnel Attribute.
* RT and RD: Route Target and Route Distinguisher.
* RT-1, RT-2, RT-3, etc.: they refer to Route Type followed by the
type number as defined in the IANA registry for EVPN route types.
* SA and DA: Source Address and Destination Address. They are used
along with MAC or IP, e.g. IP SA or MAC DA.
* SBD: Supplementary Broadcast Domain. Defined in [RFC9136], it is
a Broadcast Domain that does not have any Attachment Circuits,
only IRB interfaces, and provides connectivity among all the IP-
VRFs of a tenant in the Interface-ful IP-VRF-to-IP-VRF models.
* TS: Tenant System. A physical or virtual system that can play the
role of a host or a forwarding element such as a router, switch,
firewall, etc. It belongs to a single tenant and connects to one
or more Broadcast Domains of that tenant.
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* VNI: Virtual Network Identifier. Irrespective of the NVO3
encapsulation, the tunnel header always includes a VNI that is
added at the ingress NVE (based on the mapping table lookup) and
identifies the BT at the egress NVE. This VNI is called VNI in
VXLAN or GENEVE, VSID in nvGRE or Label in MPLSoGRE or MPLSoUDP.
This document will refer to VNI as a generic Virtual Network
Identifier for any NVO3 encapsulation.
* VXLAN: Virtual eXtensible Local Area Network, an NVO3
encapsulation defined in [RFC7348].
3. Why is EVPN Needed in NVO3 Networks?
Data Centers have adopted NVO3 architectures mostly due to the issues
discussed in [RFC7364]. The architecture of a Data Center is
nowadays based on a CLOS design, where every Leaf is connected to a
layer of Spines, and there is a number of Equal Cost Multi-Paths
between any two leaf nodes. All the links between Leaf and Spine
nodes are routed links, forming what we also know as an underlay IP
Fabric. The underlay IP Fabric does not have issues with loops or
flooding (like old Spanning Tree Data Center designs did),
convergence is fast and Equal Cost Multi-Path provides a fairly
optimal bandwidth utilization on all the links.
On this architecture and as discussed by [RFC7364], multi-tenant
intra-subnet and inter-subnet connectivity services are provided by
NVO3 tunnels, being VXLAN [RFC7348] or GENEVE [RFC8926] two examples
of such tunnels.
Why is a control-plane protocol along with NVO3 tunnels required?
There are three main reasons:
a. Auto-discovery of the remote NVEs that are attached to the same
VPN instance (Layer-2 and/or Layer-3) as the ingress NVE is.
b. Dissemination of the MAC/IP host information so that mapping
tables can be populated on the remote NVEs.
c. Advanced features such as MAC Mobility, MAC Protection, BUM and
ARP/ND traffic reduction/suppression, Multi-homing, Prefix
Independent Convergence (PIC) like functionality, Fast
Convergence, etc.
A possible approach to achieve points (a) and (b) above for
multipoint Ethernet services, is "flood and learn". "Flood and
learn" refers to not using a specific control-plane on the NVEs, but
rather "flood" BUM traffic from the ingress NVE to all the egress
NVEs attached to the same Broadcast Domain. The egress NVEs may then
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use data path source MAC address "learning" on the frames received
over the NVO3 tunnels. When the destination host replies back and
the frames arrive at the NVE that initially flooded BUM frames, the
NVE will also "learn" the source MAC address of the frame
encapsulated on the NVO3 tunnel. This approach has the following
drawbacks:
* In order to flood a given BUM frame, the ingress NVE must know the
IP addresses of the remote NVEs attached to the same Broadcast
Domain. This may be done as follows:
- The remote tunnel IP addresses can be statically provisioned on
the ingress NVE. If the ingress NVE receives a BUM frame for
the Broadcast Domain on an ingress Attachment Circuit, it will
do ingress replication and will send the frame to all the
configured egress NVE destination IP addresss in the Broadcast
Domain.
- All the NVEs attached to the same Broadcast Domain can
subscribe to an underlay IP Multicast Group that is dedicated
to that Broadcast Domain. When an ingress NVE receives a BUM
frame on an ingress Attachment Circuit, it will send a single
copy of the frame encapsulated into an NVO3 tunnel, using the
multicast address as destination IP address of the tunnel.
This solution requires Protocol Independent Multicast (PIM) in
the underlay network and the association of individual
Broadcast Domains to underlay IP multicast groups.
* "Flood and learn" solves the issues of auto-discovery and learning
of the MAC to VNI/tunnel IP mapping on the NVEs for a given
Broadcast Domain. However, it does not provide a solution for
advanced features and it does not scale well (mostly due to the
need for constant flooding and the underlay PIM states that are
needed to maintain).
EVPN provides a unified control-plane that solves the NVE auto-
discovery, tenant MAP/IP dissemination and advanced features in a
scalable way and keeping the independence of the underlay IP Fabric,
i.e., there is no need to enable PIM in the underlay network and
maintain multicast states for tenant Broadcast Domains.
Section 4 describes how EVPN can be used to meet the control-plane
requirements in an NVO3 network.
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4. Applicability of EVPN to NVO3 Networks
This section discusses the applicability of EVPN to NVO3 networks.
The intent is not to provide a comprehensive explanation of the
protocol itself but give an introduction and point at the
corresponding reference document, so that the reader can easily find
more details if needed.
4.1. EVPN Route Types Used in NVO3 Networks
EVPN supports multiple Route Types and each type has a different
function. For convenience, Table 1 shows a summary of all the
existing EVPN route types and its usage. In this document we may
refer to these route types as RT-x routes, where x is the type number
included in the first column of Table 1.
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+======+=====================+======================================+
| Type | Description | Usage |
+======+=====================+======================================+
| 1 | Ethernet Auto- | Multi-homing: Per-ES: Mass |
| | Discovery | withdrawal, Per-EVI: aliasing/backup |
+------+---------------------+--------------------------------------+
| 2 | MAC/IP | Host MAC/IP dissemination, supports |
| | Advertisement | MAC mobility and protection |
+------+---------------------+--------------------------------------+
| 3 | Inclusive | NVE discovery and BUM flooding tree |
| | Multicast | setup |
| | Ethernet Tag | |
+------+---------------------+--------------------------------------+
| 4 | Ethernet | Multi-homing: ES auto-discovery and |
| | Segment | DF Election |
+------+---------------------+--------------------------------------+
| 5 | IP Prefix | IP Prefix dissemination |
+------+---------------------+--------------------------------------+
| 6 | Selective | Indicate interest for a multicast |
| | Multicast | S,G or *,G |
| | Ethernet Tag | |
+------+---------------------+--------------------------------------+
| 7 | Multicast Join | Multi-homing: S,G or *,G state synch |
| | Synch | |
+------+---------------------+--------------------------------------+
| 8 | Multicast | Multi-homing: S,G or *,G leave synch |
| | Leave Synch | |
+------+---------------------+--------------------------------------+
| 9 | Per-Region | BUM tree creation across regions |
| | I-PMSI A-D | |
+------+---------------------+--------------------------------------+
| 10 | S-PMSI A-D | Multicast tree for S,G or *,G states |
+------+---------------------+--------------------------------------+
| 11 | Leaf A-D | Used for responses to explicit |
| | | tracking |
+------+---------------------+--------------------------------------+
Table 1: EVPN route types
4.2. EVPN Basic Applicability for Layer-2 Services
Although the applicability of EVPN to NVO3 networks spans multiple
documents, EVPN's baseline specification is [RFC7432]. [RFC7432]
allows multipoint layer-2 VPNs to be operated as [RFC4364] IP-VPNs,
where MACs and the information to setup flooding trees are
distributed by MP-BGP [RFC4760]. Based on [RFC7432], [RFC8365]
describes how to use EVPN to deliver Layer-2 services specifically in
NVO3 Networks.
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Figure 1 represents a Layer-2 service deployed with an EVPN Broadcast
Domain in an NVO3 network.
+--TS2---+
* | Single-Active
* | ESI-1
+----+ +----+
|BD1 | |BD1 |
+-------------| |--| |-----------+
| +----+ +----+ |
| NVE2 NVE3 NVE4
| EVPN NVO3 Network +----+
NVE1(IP-A) | BD1|-----+
+-------------+ RT-2 | | |
| | +-------+ +----+ |
| +----+ | |MAC1 | NVE5 TS3
TS1--------|BD1 | | |IP1 | +----+ |
MAC1 | +----+ | |Label L|---> | BD1|-----+
IP1 | | |NH IP-A| | | All-Active
| Hypervisor | +-------+ +----+ ESI-2
+-------------+ |
+--------------------------------------+
Figure 1: EVPN for L2 in an NVO3 Network - example
In a simple NVO3 network, such as the example of Figure 1, these are
the basic constructs that EVPN uses for Layer-2 services (or Layer-2
Virtual Networks):
* BD1 is an EVPN Broadcast Domain for a given tenant and TS1, TS2
and TS3 are connected to it. The five represented NVEs are
attached to BD1 and are connected to the same underlay IP network.
That is, each NVE learns the remote NVEs' loopback addresses via
underlay routing protocol.
* NVE1 is deployed as a virtual switch in a Hypervisor with IP-A as
underlay loopback IP address. The rest of the NVEs in Figure 1
are physical switches and TS2/TS3 are multi-homed to them. TS1 is
a virtual machine, identified by MAC1 and IP1. TS2 and TS3 are
physically dual-connected to NVEs, hence they are normally not
considered virtual machines.
* The terms Single-Active and All-Active in Figure 1 refer to the
mode in which the TS2 and TS3 are multi-homed to the NVEs in BD1.
In All-Active mode, all the multi-homing links are active and can
send or receive traffic. In Single-Active mode, only one link (of
the set of links connected to the NVEs) is active.
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4.2.1. Auto-Discovery and Auto-Provisioning
Auto-discovery is one of the basic capabilities of EVPN. The
provisioning of EVPN components in NVEs is significantly automated,
simplifying the deployment of services and minimizing manual
operations that are prone to human error.
These are some of the Auto-Discovery and Auto-Provisioning
capabilities available in EVPN:
* Automation on Ethernet Segments (ES): an Ethernet Segment is
defined as a group of NVEs that are attached to the same Tenant
System or network. An Ethernet Segment is identified by an
Ethernet Segment Identifier (ESI) in the control plane, but
neither the ESI nor the NVEs that share the same Ethernet Segment
are required to be manually provisioned in the local NVE:
- If the multi-homed Tenant System or network are running
protocols such as LACP (Link Aggregation Control Protocol)
[IEEE.802.1AX_2014], MSTP (Multiple-instance Spanning Tree
Protocol), G.8032, etc. and all the NVEs in the Ethernet
Segment can listen to the protocol PDUs to uniquely identify
the multi-homed Tenant System/network, then the ESI can be
"auto-sensed" or "auto-provisioned" following the guidelines in
[RFC7432] section 5. The ESI can also be auto-derived out of
other parameters that are common to all NVEs attached to the
same Ethernet Segment.
- As described in [RFC7432], EVPN can also auto-derive the BGP
parameters required to advertise the presence of a local
Ethernet Segment in the control plane (RT and RD). Local
Ethernet Segments are advertised using Ethernet Segment routes
and the ESI-import Route-Target used by Ethernet Segment routes
can be auto-derived based on the procedures of [RFC7432],
section 7.6.
- By listening to other Ethernet Segment routes that match the
local ESI and import Route Target, an NVE can also auto-
discover the other NVEs participating in the multi-homing for
the Ethernet Segment.
- Once the NVE has auto-discovered all the NVEs attached to the
same Ethernet Segment, the NVE can automatically perform the
Designated Forwarder Election algorithm (which determines the
NVE that will forward traffic to the multi-homed Tenant System/
network). EVPN guarantees that all the NVEs in the Ethernet
Segment have a consistent Designated Forwarder Election.
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* Auto-provisioning of services: when deploying a Layer-2 Service
for a tenant in an NVO3 network, all the NVEs attached to the same
subnet must be configured with a MAC-VRF and the Broadcast Domain
for the subnet, as well as certain parameters for them. Note
that, if the EVPN service model is VLAN-based or VLAN-bundle,
implementations do not normally have a specific provisioning for
the Broadcast Domain (since it is in that case the same construct
as the MAC-VRF). EVPN allows auto-deriving as many MAC-VRF
parameters as possible. As an example, the MAC-VRF's Route Target
and Route Distinguisher for the EVPN routes may be auto-derived.
Section 5.1.2.1 in [RFC8365] specifies how to auto-derive a MAC-
VRF's Route Target as long as VLAN-based service model is
implemented. [RFC7432] specifies how to auto-derive the Route
Distinguisher.
4.2.2. Remote NVE Auto-Discovery
Auto-discovery via MP-BGP [RFC4760] is used to discover the remote
NVEs attached to a given Broadcast Domain, the NVEs participating in
a given redundancy group, the tunnel encapsulation types supported by
an NVE, etc.
In particular, when a new MAC-VRF and Broadcast Domain are enabled,
the NVE will advertise a new Inclusive Multicast Ethernet Tag route.
Besides other fields, the Inclusive Multicast Ethernet Tag route will
encode the IP address of the advertising NVE, the Ethernet Tag (which
is zero in case of VLAN-based and VLAN-bundle models) and also a PMSI
Tunnel Attribute (PTA) that indicates the information about the
intended way to deliver BUM traffic for the Broadcast Domain.
In the example of Figure 1, when BD1 is enabled, NVE1 will send an
Inclusive Multicast Ethernet Tag route including its own IP address,
Ethernet-Tag for BD1 and the PMSI Tunnel Attribute to the remote
NVEs. Assuming Ingress Replication (IR) is used, the Inclusive
Multicast Ethernet Tag route will include an identification for
Ingress Replication in the PMSI Tunnel Attribute and the Virtual
Network Identifier that the other NVEs in the Broadcast Domain must
use to send BUM traffic to the advertising NVE. The other NVEs in
the Broadcast Domain will import the Inclusive Multicast Ethernet Tag
route and will add NVE1's IP address to the flooding list for BD1.
Note that the Inclusive Multicast Ethernet Tag route is also sent
with a BGP encapsulation attribute [RFC9012] that indicates what NVO3
encapsulation the remote NVEs should use when sending BUM traffic to
NVE1.
Refer to [RFC7432] for more information about the Inclusive Multicast
Ethernet Tag route and forwarding of BUM traffic, and to [RFC8365]
for its considerations on NVO3 networks.
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4.2.3. Distribution of Tenant MAC and IP Information
Tenant MAC/IP information is advertised to remote NVEs using MAC/IP
Advertisement routes. Following the example of Figure 1:
* In a given EVPN Broadcast Domain, Tenant Systems' MAC addresses
are first learned at the NVE they are attached to, via data path
or management plane learning. In Figure 1 we assume NVE1 learns
MAC1/IP1 in the management plane (for instance, via Cloud
Management System) since the NVE is a virtual switch. NVE2, NVE3,
NVE4 and NVE5 are TOR/Leaf switches and they normally learn MAC
addresses via data path.
* Once NVE1's BD1 learns MAC1/IP1, NVE1 advertises that information
along with a Virtual Network Identifier and Next Hop IP-A in an
MAC/IP Advertisement route. The EVPN routes are advertised using
the Route Distinguisher/Route Targets of the MAC-VRF where the
Broadcast Domain belongs. All the NVEs in BD1 learn local MAC/IP
addresses and advertise them in MAC/IP Advertisement routes in a
similar way.
* The remote NVEs can then add MAC1 to their mapping table for BD1
(BT). For instance, when TS3 sends frames to NVE4 with
destination MAC address = MAC1, NVE4 does a MAC lookup on the
Bridge Table that yields IP-A and Label L. NVE4 can then
encapsulate the frame into an NVO3 tunnel with IP-A as the tunnel
destination IP address and L as the Virtual Network Identifier.
Note that the MAC/IP Advertisement route may also contain the
host's IP address (as in the example of Figure 1). While the MAC
of the received MAC/IP Advertisement route is installed in the
Bridge Table, the IP address may be installed in the Proxy-ARP/ND
table (if enabled) or in the ARP/IP-VRF tables if the Broadcast
Domain has an IRB. See Section 4.7.3 to see more information
about Proxy-ARP/ND and Section 4.3. for more details about IRB and
Layer-3 services.
Refer to [RFC7432] and [RFC8365] for more information about the MAC/
IP Advertisement route and forwarding of known unicast traffic.
4.3. EVPN Basic Applicability for Layer-3 Services
[RFC9136] and [RFC9135] are the reference documents that describe how
EVPN can be used for Layer-3 services. Inter Subnet Forwarding in
EVPN networks is implemented via IRB interfaces between Broadcast
Domains and IP-VRFs. An EVPN Broadcast Domain corresponds to an IP
subnet. When IP packets generated in a Broadcast Domain are destined
to a different subnet (different Broadcast Domain) of the same
tenant, the packets are sent to the IRB attached to the local
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Broadcast Domain in the source NVE. As discussed in [RFC9135],
depending on how the IP packets are forwarded between the ingress NVE
and the egress NVE, there are two forwarding models: Asymmetric and
Symmetric model.
The Asymmetric model is illustrated in the example of Figure 2 and it
requires the configuration of all the Broadcast Domains of the tenant
in all the NVEs attached to the same tenant. In that way, there is
no need to advertise IP Prefixes between NVEs since all the NVEs are
attached to all the subnets. It is called Asymmetric because the
ingress and egress NVEs do not perform the same number of lookups in
the data plane. In Figure 2, if TS1 and TS2 are in different
subnets, and TS1 sends IP packets to TS2, the following lookups are
required in the data path: a MAC lookup (on BD1's table), an IP
lookup (on the IP-VRF) and a MAC lookup (on BD2's table) at the
ingress NVE1 and then only a MAC lookup at the egress NVE. The two
IP-VRFs in Figure 2 are not connected by tunnels and all the
connectivity between the NVEs is done based on tunnels between the
Broadcast Domains.
+-------------------------------------+
| EVPN NVO3 |
| |
NVE1 NVE2
+--------------------+ +--------------------+
| +---+IRB +------+ | | +------+IRB +---+ |
TS1-----|BD1|----|IP-VRF| | | |IP-VRF|----|BD1| |
| +---+ | | | | | | +---+ |
| +---+ | | | | | | +---+ |
| |BD2|----| | | | | |----|BD2|----TS2
| +---+IRB +------+ | | +------+IRB +---+ |
+--------------------+ +--------------------+
| |
+-------------------------------------+
Figure 2: EVPN for L3 in an NVO3 Network - Asymmetric model
In the Symmetric model, depicted in Figure 3, the same number of data
path lookups is needed at the ingress and egress NVEs. For example,
if TS1 sends IP packets to TS3, the following data path lookups are
required: a MAC lookup at NVE1's BD1 table, an IP lookup at NVE1's
IP-VRF and then IP lookup and MAC lookup at NVE2's IP-VRF and BD3
respectively. In the Symmetric model, the Inter Subnet connectivity
between NVEs is done based on tunnels between the IP-VRFs.
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+-------------------------------------+
| EVPN NVO3 |
| |
NVE1 NVE2
+--------------------+ +--------------------+
| +---+IRB +------+ | | +------+IRB +---+ |
TS1-----|BD1|----|IP-VRF| | | |IP-VRF|----|BD3|-----TS3
| +---+ | | | | | | +---+ |
| +---+IRB | | | | +------+ |
TS2-----|BD2|----| | | +--------------------+
| +---+ +------+ | |
+--------------------+ |
| |
+-------------------------------------+
Figure 3: EVPN for L3 in an NVO3 Network - Symmetric model
The Symmetric model scales better than the Asymmetric model because
it does not require the NVEs to be attached to all the tenant's
subnets. However, it requires the use of NVO3 tunnels on the IP-VRFs
and the exchange of IP Prefixes between the NVEs in the control
plane. EVPN uses MAC/IP Advertisement and IP Prefix routes for the
exchange of host IP routes (in the case of the MAC/IP Advertisement
and the IP Prefix routes) and IP Prefixes (IP Prefix routes) of any
length. As an example, in Figure 3, NVE2 needs to advertise TS3's
host route and/or TS3's subnet, so that the IP lookup on NVE1's IP-
VRF succeeds.
[RFC9135] specifies the use of MAC/IP Advertisement routes for the
advertisement of host routes. Section 4.4.1 in [RFC9136] specifies
the use of IP Prefix routes for the advertisement of IP Prefixes in
an "Interface-less IP-VRF-to-IP-VRF Model". The Symmetric model for
host routes can be implemented following either approach:
a. [RFC9135] uses MAC/IP Advertisement routes to convey the
information to populate Layer-2, ARP/ND and Layer-3 Forwarding
Information Base tables in the remote NVE. For instance, in
Figure 3, NVE2 would advertise a MAC/IP Advertisement route with
TS3's IP and MAC addresses, and including two labels/Virtual
Network Identifiers: a label-3/VNI-3 that identifies BD3 for MAC
lookup (that would be used for Layer-2 traffic in case NVE1 was
attached to BD3 too) and a label-1/VNI-1 that identifies the IP-
VRF for IP lookup (and will be used for Layer-3 traffic). NVE1
imports the MAC/IP Advertisement route and installs TS3's IP in
the IP-VRF route table with label-1/VNI-1. Traffic from e.g.,
TS2 to TS3, will be encapsulated with label-1/VNI-1 and forwarded
to NVE2.
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b. [RFC9136] uses MAC/IP Advertisement routes to convey the
information to populate the Layer-2 Forwarding Information Base
and ARP/ND tables, and IP Prefix routes to populate the IP-VRF
Layer-3 Forwarding Information Base table. For instance, in
Figure 3, NVE2 would advertise a MAC/IP Advertisement route
including TS3's MAC and IP addresses with a single label-3/VNI-3.
In this example, this MAC/IP Advertisement route wouldn't be
imported by NVE1 because NVE1 is not attached to BD3. In
addition, NVE2 would advertise a IP Prefix route with TS3's IP
address and label-1/VNI-1. This IP Prefix route would be
imported by NVE1's IP-VRF and the host route installed in the
Layer-3 Forwarding Information Base associated to label-1/VNI-1.
Traffic from TS2 to TS3 would be encapsulated with label-1/VNI-1.
4.4. EVPN as Control Plane for NVO3 Encapsulations and GENEVE
[RFC8365] describes how to use EVPN for NVO3 encapsulations, such us
VXLAN, nvGRE or MPLSoGRE. The procedures can be easily applicable to
any other NVO3 encapsulation, in particular GENEVE.
The Generic Network Virtualization Encapsulation [RFC8926] has been
recommended to be the proposed standard for NVO3 Encapsulation. The
EVPN control plane can signal the GENEVE encapsulation type in the
BGP Tunnel Encapsulation Extended Community (see [RFC9012]).
The NVO3 encapsulation design team has made a recommendation in
[I-D.ietf-nvo3-encap] for a control plane to:
1. Negotiate a subset of GENEVE option TLVs that can be carried on a
GENEVE tunnel
2. Enforce an order for GENEVE option TLVs and
3. Limit the total number of options that could be carried on a
GENEVE tunnel.
The EVPN control plane can easily extend the BGP Tunnel Encapsulation
Attribute sub-TLV [RFC9012] to specify the GENEVE tunnel options that
can be received or transmitted over a GENEVE tunnels by a given NVE.
[I-D.ietf-bess-evpn-geneve] describes the EVPN control plane
extensions to support GENEVE.
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4.5. EVPN OAM and Application to NVO3
EVPN OAM (as in [I-D.ietf-bess-evpn-lsp-ping]) defines mechanisms to
detect data plane failures in an EVPN deployment over an MPLS
network. These mechanisms detect failures related to P2P and P2MP
connectivity, for multi-tenant unicast and multicast Layer-2 traffic,
between multi-tenant access nodes connected to EVPN PE(s), and in a
single-homed, single-active or all-active redundancy model.
In general, EVPN OAM mechanisms defined for EVPN deployed in MPLS
networks are equally applicable for EVPN in NVO3 networks.
4.6. EVPN as the Control Plane for NVO3 Security
EVPN can be used to signal the security protection capabilities of a
sender NVE, as well as what portion of an NVO3 packet (taking a
GENEVE packet as an example) can be protected by the sender NVE, to
ensure the privacy and integrity of tenant traffic carried over the
NVO3 tunnels [I-D.sajassi-bess-secure-evpn].
4.7. Advanced EVPN Features for NVO3 Networks
This section describes how EVPN can be used to deliver advanced
capabilities in NVO3 networks.
4.7.1. Virtual Machine (VM) Mobility
[RFC7432] replaces the traditional Ethernet Flood-and-Learn behavior
among NVEs with BGP-based MAC learning, which in return provides more
control over the location of MAC addresses in the Broadcast Domain
and consequently advanced features, such as MAC Mobility. If we
assume that VM Mobility means the VM's MAC and IP addresses move with
the VM, EVPN's MAC Mobility is the required procedure that
facilitates VM Mobility. According to [RFC7432] section 15, when a
MAC is advertised for the first time in a Broadcast Domain, all the
NVEs attached to the Broadcast Domain will store Sequence Number zero
for that MAC. When the MAC "moves" within the same Broadcast Domain
but to a remote NVE, the NVE that just learned locally the MAC,
increases the Sequence Number in the MAC/IP Advertisement route's MAC
Mobility extended community to indicate that it owns the MAC now.
That makes all the NVE in the Broadcast Domain change their tables
immediately with no need to wait for any aging timer. EVPN
guarantees a fast MAC Mobility without flooding or black-holes in the
Broadcast Domain.
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4.7.2. MAC Protection, Duplication Detection and Loop Protection
The advertisement of MACs in the control plane, allows advanced
features such as MAC protection, Duplication Detection and Loop
Protection.
[RFC7432] MAC Protection refers to EVPN's ability to indicate - in a
MAC/IP Advertisement route - that a MAC must be protected by the NVE
receiving the route. The Protection is indicated in the "Sticky bit"
of the MAC Mobility extended community sent along the MAC/IP
Advertisement route for a MAC. NVEs' Attachment Circuits that are
connected to subject-to-be-protected servers or VMs, may set the
Sticky bit on the MAC/IP Advertisement routes sent for the MACs
associated to the Attachment Circuits. Also, statically configured
MAC addresses should be advertised as Protected MAC addresses, since
they are not subject to MAC Mobility procedures.
[RFC7432] MAC Duplication Detection refers to EVPN's ability to
detect duplicate MAC addresses. A "MAC move" is a relearn event that
happens at an access Attachment Circuit or through a MAC/IP
Advertisement route with a Sequence Number that is higher than the
stored one for the MAC. When a MAC moves a number of times N within
an M-second window between two NVEs, the MAC is declared as Duplicate
and the detecting NVE does not re-advertise the MAC anymore.
[RFC7432] provides MAC Duplication Detection, and with an extension
it can protect the Broadcast Domain against loops created by backdoor
links between NVEs. The same principle (based on the Sequence
Number) may be extended to protect the Broadcast Domain against
loops. When a MAC is detected as duplicate, the NVE may install it
as a black-hole MAC and drop received frames with source MAC address
and destination MAC address matching that duplicate MAC. The MAC
Duplication extension to support Loop Protection is described in
[I-D.ietf-bess-rfc7432bis].
4.7.3. Reduction/Optimization of BUM Traffic in Layer-2 Services
In Broadcast Domains with a significant amount of flooding due to
Unknown unicast and Broadcast frames, EVPN may help reduce and
sometimes even suppress the flooding.
In Broadcast Domains where most of the Broadcast traffic is caused by
ARP (Address Resolution Protocol) and ND (Neighbor Discovery)
protocols on the Tenant Systems, EVPN's Proxy-ARP and Proxy-ND
capabilities may reduce the flooding drastically. The use of Proxy-
ARP/ND is specified in [RFC9161].
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Proxy-ARP/ND procedures along with the assumption that Tenant Systems
always issue a GARP (Gratuitous ARP) or an unsolicited Neighbor
Advertisement message when they come up in the Broadcast Domain, may
drastically reduce the unknown unicast flooding in the Broadcast
Domain.
The flooding caused by Tenant Systems' IGMP/MLD or PIM messages in
the Broadcast Domain may also be suppressed by the use of IGMP/MLD
and PIM Proxy functions, as specified in [RFC9251] and
[I-D.skr-bess-evpn-pim-proxy]. These two documents also specify how
to forward IP multicast traffic efficiently within the same Broadcast
Domain, translate soft state IGMP/MLD/PIM messages into hard state
BGP routes and provide fast-convergence redundancy for IP Multicast
on multi-homed Ethernet Segments (ESes).
4.7.4. Ingress Replication (IR) Optimization for BUM Traffic
When an NVE attached to a given Broadcast Domain needs to send BUM
traffic for the Broadcast Domain to the remote NVEs attached to the
same Broadcast Domain, Ingress Replication is a very common option in
NVO3 networks, since it is completely independent of the multicast
capabilities of the underlay network. Also, if the optimization
procedures to reduce/suppress the flooding in the Broadcast Domain
are enabled (Section 4.7.3), in spite of creating multiple copies of
the same frame at the ingress NVE, Ingress Replication may be good
enough. However, in Broadcast Domains where Multicast (or Broadcast)
traffic is significant, Ingress Replication may be very inefficient
and cause performance issues on virtual-switch-based NVEs.
[I-D.ietf-bess-evpn-optimized-ir] specifies the use of AR (Assisted
Replication) NVO3 tunnels in EVPN Broadcast Domains. AR retains the
independence of the underlay network while providing a way to forward
Broadcast and Multicast traffic efficiently. AR uses AR-REPLICATORs
that can replicate the Broadcast/Multicast traffic on behalf of the
AR-LEAF NVEs. The AR-LEAF NVEs are typically virtual-switches or
NVEs with limited replication capabilities. AR can work in a single-
stage replication mode (Non-Selective Mode) or in a dual-stage
replication mode (Selective Mode). Both modes are detailed in
[I-D.ietf-bess-evpn-optimized-ir].
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In addition, [I-D.ietf-bess-evpn-optimized-ir] also describes a
procedure to avoid sending Broadcast, Multicast or Unknown unicast to
certain NVEs that do not need that type of traffic. This is done by
enabling PFL (Pruned Flood Lists) on a given Broadcast Domain. For
instance, an virtual-switch NVE that learns all its local MAC
addresses for a Broadcast Domain via Cloud Management System, does
not need to receive the Broadcast Domain's Unknown unicast traffic.
Pruned Flood Lists help optimize the BUM flooding in the Broadcast
Domain.
4.7.5. EVPN Multi-Homing
Another fundamental concept in EVPN is multi-homing. A given Tenant
System can be multi-homed to two or more NVEs for a given Broadcast
Domain, and the set of links connected to the same Tenant System is
defined as Ethernet Segment (ES). EVPN supports single-active and
all-active multi-homing. In single-active multi-homing only one link
in the Ethernet Segment is active. In all-active multi-homing all
the links in the Ethernet Segment are active for unicast traffic.
Both modes support load-balancing:
* Single-active multi-homing means per-service load-balancing to/
from the Tenant System. For example, in Figure 1, for BD1, only
one of the NVEs can forward traffic from/to TS2. For a different
Broadcast Domain, the other NVE may forward traffic.
* All-active multi-homing means per-flow load-balanding for unicast
frames to/from the Tenant System. That is, in Figure 1 and for
BD1, both NVE4 and NVE5 can forward known unicast traffic to/from
TS3. For BUM traffic only one of the two NVEs can forward traffic
to TS3, and both can forward traffic from TS3.
There are two key aspects in the EVPN multi-homing procedures:
* DF (Designated Forwarder) election: the Designated Forwarder is
the NVE that forwards the traffic to the Ethernet Segment in
single-active mode. In case of all-active, the Designated
Forwarder is the NVE that forwards the BUM traffic to the Ethernet
Segment.
* Split-horizon function: prevents the Tenant System from receiving
echoed BUM frames that the Tenant System itself sent to the
Ethernet Segment. This is especially relevant in all-active
Ethernet Segments, where the Tenant System may forward BUM frames
to a non-Designated Forwarder NVE that can flood the BUM frames
back to the Designated Forwarder NVE and then the Tenant System.
As an example, in Figure 1, assuming NVE4 is the Designated
Forwarder for ES-2 in BD1, BUM frames sent from TS3 to NVE5 will
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be received at NVE4 and, since NVE4 is the Designated Forwarder
for DB1, it will forward them back to TS3. Split-horizon allows
NVE4 (and any multi-homed NVE for that matter) to identify if an
EVPN BUM frame is coming from the same Ethernet Segment or
different, and if the frame belongs to the same ES2, NVE4 will not
forward the BUM frame to TS3, in spite of being the Designated
Forwarder.
While [RFC7432] describes the default algorithm for the Designated
Forwarder Election, [RFC8584] and [I-D.ietf-bess-evpn-pref-df]
specify other algorithms and procedures that optimize the Designated
Forwarder Election.
The Split-horizon function is specified in [RFC7432] and it is
carried out by using a special ESI-label that it identifies in the
data path, all the BUM frames being originated from a given NVE and
Ethernet Segment. Since the ESI-label is an MPLS label, it cannot be
used in all the non-MPLS NVO3 encapsulations, therefore [RFC8365]
defines a modified Split-horizon procedure that is based on the
source IP address of the NVO3 tunnel, and it is known as "Local-
Bias". It is worth noting that Local-Bias only works for all-active
multi-homing, and not for single-active multi-homing.
4.7.6. EVPN Recursive Resolution for Inter-Subnet Unicast Forwarding
Section 4.3 describes how EVPN can be used for Inter Subnet
Forwarding among subnets of the same tenant. MAC/IP Advertisement
routes and IP Prefix routes allow the advertisement of host routes
and IP Prefixes (IP Prefix route) of any length. The procedures
outlined by Section 4.3 are similar to the ones in [RFC4364], only
for NVO3 tunnels. However, [RFC9136] also defines advanced Inter
Subnet Forwarding procedures that allow the resolution of IP Prefix
routes to not only BGP next-hops but also "overlay indexes" that can
be a MAC, a GW IP or an ESI, all of them in the tenant space.
Figure 4 illustrates an example that uses Recursive Resolution to a
GW-IP as per [RFC9136] section 4.4.2. In this example, IP-VRFs in
NVE1 and NVE2 are connected by a SBD (Supplementary Broadcast
Domain). An SBD is a Broadcast Domain that connects all the IP-VRFs
of the same tenant, via IRB, and has no Attachment Circuits. NVE1
advertises the host route TS2-IP/L (IP address and Prefix Length of
TS2) in an IP Prefix route with overlay index GWIP=IP1. Also, IP1 is
advertised in an MAC/IP Advertisement route associated to M1, VNI-S
and BGP next-hop NVE1. Upon importing the two routes, NVE2 installs
TS2-IP/L in the IP-VRF with a next-hop that is the GWIP IP1. NVE2
also installs M1 in the Supplementary Broadcast Domain, with VNI-S
and NVE1 as next-hop. If TS3 sends a packet with IP DA=TS2, NVE2
will perform a Recursive Resolution of the IP Prefix route prefix
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information to the forwarding information of the correlated MAC/IP
Advertisement route. The IP Prefix route's Recursive Resolution has
several advantages such as better convergence in scaled networks
(since multiple IP Prefix routes can be invalidated with a single
withdrawal of the overlay index route) or the ability to advertise
multiple IP Prefix routes from an overlay index that can move or
change dynamically. [RFC9136] describes a few use-cases.
+-------------------------------------+
| EVPN NVO3 |
| +
NVE1 NVE2
+--------------------+ +--------------------+
| +---+IRB +------+ | | +------+IRB +---+ |
TS1-----|BD1|----|IP-VRF| | | |IP-VRF|----|BD3|-----TS3
| +---+ | |-(SBD)------(SBD)-| | +---+ |
| +---+IRB | |IRB(IP1/M1) IRB+------+ |
TS2-----|BD2|----| | | +-----------+--------+
| +---+ +------+ | |
+--------------------+ |
| RT-2(M1,IP1,VNI-S,NVE1)--> |
| RT-5(TS2-IP/L,GWIP=IP1)--> |
+-------------------------------------+
Figure 4: EVPN for L3 - Recursive Resolution example
4.7.7. EVPN Optimized Inter-Subnet Multicast Forwarding
The concept of the Supplementary Broadcast Domain described in
Section 4.7.6 is also used in [I-D.ietf-bess-evpn-irb-mcast] for the
procedures related to Inter Subnet Multicast Forwarding across
Broadcast Domains of the same tenant. For instance,
[I-D.ietf-bess-evpn-irb-mcast] allows the efficient forwarding of IP
multicast traffic from any Broadcast Domain to any other Broadcast
Domain (or even to the same Broadcast Domain where the Source
resides). The [I-D.ietf-bess-evpn-irb-mcast] procedures are
supported along with EVPN multi-homing, and for any tree allowed on
NVO3 networks, including IR or AR. [I-D.ietf-bess-evpn-irb-mcast]
also describes the interoperability between EVPN and other multicast
technologies such as MVPN (Multicast VPN) and PIM for inter-subnet
multicast.
[I-D.ietf-bess-evpn-mvpn-seamless-interop] describes another
potential solution to support EVPN to MVPN interoperability.
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4.7.8. Data Center Interconnect (DCI)
Tenant Layer-2 and Layer-3 services deployed on NVO3 networks must be
extended to remote NVO3 networks that are connected via non-NOV3 Wide
Area Networks (mostly MPLS based Wide Area Networks). [RFC9014]
defines some architectural models that can be used to interconnect
NVO3 networks via MPLS Wide Area Networks.
When NVO3 networks are connected by MPLS Wide Area Networks,
[RFC9014] specifies how EVPN can be used end-to-end, in spite of
using a different encapsulation in the Wide Area Network. [RFC9014]
also supports the use of NVO3 or Segment Routing (encoding 32-bit or
128-bit Segment Identifiers into labels or IPv6 addresses
respectively) transport tunnels in the Wide Area Network.
Even if EVPN can also be used in the Wide Area Network for Layer-2
and Layer-3 services, there may be a need to provide a Gateway
function between EVPN for NVO3 encapsulations and IPVPN for MPLS
tunnels, if the operator uses IPVPN in the Wide Area Network.
[I-D.ietf-bess-evpn-ipvpn-interworking] specifies the interworking
function between EVPN and IPVPN for unicast Inter Subnet Forwarding.
If Inter Subnet Multicast Forwarding is also needed across an IPVPN
Wide Area Network, [I-D.ietf-bess-evpn-irb-mcast] describes the
required interworking between EVPN and MVPN (Multicast Virtual
Private Networks).
5. Conclusion
EVPN provides a unified control-plane that solves the NVE auto-
discovery, tenant MAP/IP dissemination and advanced features required
by NVO3 networks, in a scalable way and keeping the independence of
the underlay IP Fabric, i.e. there is no need to enable PIM in the
underlay network and maintain multicast states for tenant Broadcast
Domains.
This document justifies the use of EVPN for NVO3 networks, discusses
its applicability to basic Layer-2 and Layer-3 connectivity
requirements, as well as advanced features such as MAC-mobility, MAC
Protection and Loop Protection, multi-homing, DCI and much more.
6. Conventions Used in this Document
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 BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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7. Security Considerations
This document does not introduce any new procedure or additional
signaling in EVPN, and relies on the security considerations of the
individual specifications used as a reference throughout the
document. In particular, and as mentioned in [RFC7432], control
plane and forwarding path protection are aspects to secure in any
EVPN domain, when applied to NVO3 networks.
[RFC7432] mentions security techniques such as those discussed in
[RFC5925] to authenticate BGP messages, and those included in
[RFC4271], [RFC4272] and [RFC6952] to secure BGP are relevant for
EVPN in NVO3 networks as well.
8. IANA Considerations
None.
9. References
9.1. Normative References
[RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
2015, <https://www.rfc-editor.org/info/rfc7432>.
[RFC7365] Lasserre, M., Balus, F., Morin, T., Bitar, N., and Y.
Rekhter, "Framework for Data Center (DC) Network
Virtualization", RFC 7365, DOI 10.17487/RFC7365, October
2014, <https://www.rfc-editor.org/info/rfc7365>.
[RFC7364] Narten, T., Ed., Gray, E., Ed., Black, D., Fang, L.,
Kreeger, L., and M. Napierala, "Problem Statement:
Overlays for Network Virtualization", RFC 7364,
DOI 10.17487/RFC7364, October 2014,
<https://www.rfc-editor.org/info/rfc7364>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
9.2. Informative References
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[RFC9136] Rabadan, J., Ed., Henderickx, W., Drake, J., Lin, W., and
A. Sajassi, "IP Prefix Advertisement in Ethernet VPN
(EVPN)", RFC 9136, DOI 10.17487/RFC9136, October 2021,
<https://www.rfc-editor.org/info/rfc9136>.
[RFC9135] Sajassi, A., Salam, S., Thoria, S., Drake, J., and J.
Rabadan, "Integrated Routing and Bridging in Ethernet VPN
(EVPN)", RFC 9135, DOI 10.17487/RFC9135, October 2021,
<https://www.rfc-editor.org/info/rfc9135>.
[RFC8365] Sajassi, A., Ed., Drake, J., Ed., Bitar, N., Shekhar, R.,
Uttaro, J., and W. Henderickx, "A Network Virtualization
Overlay Solution Using Ethernet VPN (EVPN)", RFC 8365,
DOI 10.17487/RFC8365, March 2018,
<https://www.rfc-editor.org/info/rfc8365>.
[RFC8926] Gross, J., Ed., Ganga, I., Ed., and T. Sridhar, Ed.,
"Geneve: Generic Network Virtualization Encapsulation",
RFC 8926, DOI 10.17487/RFC8926, November 2020,
<https://www.rfc-editor.org/info/rfc8926>.
[I-D.ietf-nvo3-encap]
Boutros, S. and D. E. Eastlake, "Network Virtualization
Overlays (NVO3) Encapsulation Considerations", Work in
Progress, Internet-Draft, draft-ietf-nvo3-encap-08, 30
April 2022, <https://www.ietf.org/archive/id/draft-ietf-
nvo3-encap-08.txt>.
[RFC9012] Patel, K., Van de Velde, G., Sangli, S., and J. Scudder,
"The BGP Tunnel Encapsulation Attribute", RFC 9012,
DOI 10.17487/RFC9012, April 2021,
<https://www.rfc-editor.org/info/rfc9012>.
[I-D.ietf-bess-evpn-lsp-ping]
Jain, P., Sajassi, A., Salam, S., Boutros, S., and G.
Mirsky, "LSP-Ping Mechanisms for EVPN and PBB-EVPN", Work
in Progress, Internet-Draft, draft-ietf-bess-evpn-lsp-
ping-08, 8 July 2022, <https://www.ietf.org/archive/id/
draft-ietf-bess-evpn-lsp-ping-08.txt>.
[RFC9161] Rabadan, J., Ed., Sathappan, S., Nagaraj, K., Hankins, G.,
and T. King, "Operational Aspects of Proxy ARP/ND in
Ethernet Virtual Private Networks", RFC 9161,
DOI 10.17487/RFC9161, January 2022,
<https://www.rfc-editor.org/info/rfc9161>.
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[RFC9251] Sajassi, A., Thoria, S., Mishra, M., Patel, K., Drake, J.,
and W. Lin, "Internet Group Management Protocol (IGMP) and
Multicast Listener Discovery (MLD) Proxies for Ethernet
VPN (EVPN)", RFC 9251, DOI 10.17487/RFC9251, June 2022,
<https://www.rfc-editor.org/info/rfc9251>.
[I-D.skr-bess-evpn-pim-proxy]
Rabadan, J., Kotalwar, J., Sathappan, S., Zhang, Z., and
A. Sajassi, "PIM Proxy in EVPN Networks", Work in
Progress, Internet-Draft, draft-skr-bess-evpn-pim-proxy-
01, 30 October 2017, <https://www.ietf.org/archive/id/
draft-skr-bess-evpn-pim-proxy-01.txt>.
[I-D.ietf-bess-evpn-optimized-ir]
Rabadan, J., Sathappan, S., Lin, W., Katiyar, M., and A.
Sajassi, "Optimized Ingress Replication Solution for
Ethernet VPN (EVPN)", Work in Progress, Internet-Draft,
draft-ietf-bess-evpn-optimized-ir-12, 25 January 2022,
<https://www.ietf.org/archive/id/draft-ietf-bess-evpn-
optimized-ir-12.txt>.
[RFC8584] Rabadan, J., Ed., Mohanty, S., Ed., Sajassi, A., Drake,
J., Nagaraj, K., and S. Sathappan, "Framework for Ethernet
VPN Designated Forwarder Election Extensibility",
RFC 8584, DOI 10.17487/RFC8584, April 2019,
<https://www.rfc-editor.org/info/rfc8584>.
[I-D.ietf-bess-evpn-pref-df]
Rabadan, J., Sathappan, S., Przygienda, T., Lin, W.,
Drake, J., Sajassi, A., and S. Mohanty, "Preference-based
EVPN DF Election", Work in Progress, Internet-Draft,
draft-ietf-bess-evpn-pref-df-09, 6 July 2022,
<https://www.ietf.org/archive/id/draft-ietf-bess-evpn-
pref-df-09.txt>.
[I-D.ietf-bess-evpn-irb-mcast]
Lin, W., Zhang, Z., Drake, J., Rosen, E. C., Rabadan, J.,
and A. Sajassi, "EVPN Optimized Inter-Subnet Multicast
(OISM) Forwarding", Work in Progress, Internet-Draft,
draft-ietf-bess-evpn-irb-mcast-07, 23 June 2022,
<https://www.ietf.org/archive/id/draft-ietf-bess-evpn-irb-
mcast-07.txt>.
[RFC9014] Rabadan, J., Ed., Sathappan, S., Henderickx, W., Sajassi,
A., and J. Drake, "Interconnect Solution for Ethernet VPN
(EVPN) Overlay Networks", RFC 9014, DOI 10.17487/RFC9014,
May 2021, <https://www.rfc-editor.org/info/rfc9014>.
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[I-D.ietf-bess-evpn-ipvpn-interworking]
Rabadan, J., Sajassi, A., Rosen, E., Drake, J., Lin, W.,
Uttaro, J., and A. Simpson, "EVPN Interworking with
IPVPN", Work in Progress, Internet-Draft, draft-ietf-bess-
evpn-ipvpn-interworking-07, 6 July 2022,
<https://www.ietf.org/archive/id/draft-ietf-bess-evpn-
ipvpn-interworking-07.txt>.
[RFC7348] Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
eXtensible Local Area Network (VXLAN): A Framework for
Overlaying Virtualized Layer 2 Networks over Layer 3
Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,
<https://www.rfc-editor.org/info/rfc7348>.
[RFC7510] Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black,
"Encapsulating MPLS in UDP", RFC 7510,
DOI 10.17487/RFC7510, April 2015,
<https://www.rfc-editor.org/info/rfc7510>.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
2006, <https://www.rfc-editor.org/info/rfc4364>.
[CLOS1953] Clos, C., "A Study of Non-Blocking Switching Networks",
March 1953.
[I-D.ietf-bess-evpn-geneve]
Boutros, S., Sajassi, A., Drake, J., Rabadan, J., and S.
Aldrin, "EVPN control plane for Geneve", Work in Progress,
Internet-Draft, draft-ietf-bess-evpn-geneve-04, 23 May
2022, <https://www.ietf.org/archive/id/draft-ietf-bess-
evpn-geneve-04.txt>.
[I-D.ietf-bess-evpn-mvpn-seamless-interop]
Sajassi, A., Thiruvenkatasamy, K., Thoria, S., Gupta, A.,
and L. Jalil, "Seamless Multicast Interoperability between
EVPN and MVPN PEs", Work in Progress, Internet-Draft,
draft-ietf-bess-evpn-mvpn-seamless-interop-04, 28 June
2022, <https://www.ietf.org/archive/id/draft-ietf-bess-
evpn-mvpn-seamless-interop-04.txt>.
[I-D.sajassi-bess-secure-evpn]
Sajassi, A., Banerjee, A., Thoria, S., Carrel, D., Weis,
B., and J. Drake, "Secure EVPN", Work in Progress,
Internet-Draft, draft-sajassi-bess-secure-evpn-05, 25
October 2021, <https://www.ietf.org/archive/id/draft-
sajassi-bess-secure-evpn-05.txt>.
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[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
June 2010, <https://www.rfc-editor.org/info/rfc5925>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>.
[RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis",
RFC 4272, DOI 10.17487/RFC4272, January 2006,
<https://www.rfc-editor.org/info/rfc4272>.
[RFC6952] 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, DOI 10.17487/RFC6952, May 2013,
<https://www.rfc-editor.org/info/rfc6952>.
[RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760,
DOI 10.17487/RFC4760, January 2007,
<https://www.rfc-editor.org/info/rfc4760>.
[I-D.ietf-bess-rfc7432bis]
Sajassi, A., Burdet, L. A., Drake, J., and J. Rabadan,
"BGP MPLS-Based Ethernet VPN", Work in Progress, Internet-
Draft, draft-ietf-bess-rfc7432bis-04, 7 March 2022,
<https://www.ietf.org/archive/id/draft-ietf-bess-
rfc7432bis-04.txt>.
[IEEE.802.1AX_2014]
IEEE, "IEEE Standard for Local and metropolitan area
networks -- Link Aggregation", 24 December 2014.
Appendix A. Acknowledgments
The authors want to thank Aldrin Isaac for his comments.
Appendix B. Contributors
Appendix C. Authors' Addresses
Authors' Addresses
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Jorge Rabadan (editor)
Nokia
520 Almanor Ave
Sunnyvale, CA 94085
United States of America
Email: jorge.rabadan@nokia.com
Matthew Bocci
Nokia
Email: matthew.bocci@nokia.com
Sami Boutros
Ciena
Email: sboutros@ciena.com
Ali Sajassi
Cisco Systems, Inc.
Email: sajassi@cisco.com
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