draft-ietf-bess-evpn-etree-12.txt   draft-ietf-bess-evpn-etree-13.txt 
skipping to change at page 1, line 15 skipping to change at page 1, line 15
Intended Status: Standards Track Cisco Intended Status: Standards Track Cisco
Updates: 7385 J. Drake Updates: 7385 J. Drake
Juniper Juniper
J. Uttaro J. Uttaro
ATT ATT
S. Boutros S. Boutros
VMware VMware
J. Rabadan J. Rabadan
Nokia Nokia
Expires: December 22, 2017 June 22, 2017 Expires: February 28, 2018 August 28, 2017
E-TREE Support in EVPN & PBB-EVPN E-TREE Support in EVPN & PBB-EVPN
draft-ietf-bess-evpn-etree-12 draft-ietf-bess-evpn-etree-13
Abstract Abstract
The Metro Ethernet Forum (MEF) has defined a rooted-multipoint The Metro Ethernet Forum (MEF) has defined a rooted-multipoint
Ethernet service known as Ethernet Tree (E-Tree). A solution Ethernet service known as Ethernet Tree (E-Tree). A solution
framework for supporting this service in MPLS networks is proposed in framework for supporting this service in MPLS networks is described
RFC7387 ("A Framework for Ethernet Tree (E-Tree) Service over a in RFC7387 ("A Framework for Ethernet-Tree (E-Tree) Service over a
Multiprotocol Label Switching (MPLS) Network"). This document Multiprotocol Label Switching (MPLS) Network"). This document
discusses how those functional requirements can be easily met with discusses how those functional requirements can be met with a
Ethernet VPN (EVPN) and how EVPN offers a more efficient solution based on RFC7432, BGP MPLS Based Ethernet VPN (EVPN), with
implementation of these functions. This document makes use of the some extensions and how such a solution can offer a more efficient
most significant bit of the scope governed by the IANA registry implementation of these functions than that of RFC7796, E-Tree
created by RFC7385, and hence updates RFC7385 accordingly. Support in Virtual Private LAN Service (VPLS). This document makes
use of the most significant bit of the "Tunnel Type" field (in PMSI
Tunnel Attribute) governed by the IANA registry created by RFC7385,
and hence updates RFC7385 accordingly.
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the This Internet-Draft is submitted to IETF 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 other groups may also distribute working documents as
Internet-Drafts. Internet-Drafts.
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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 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1 Specification of Requirements . . . . . . . . . . . . . . . 4
2 E-Tree Scenarios . . . . . . . . . . . . . . . . . . . . . . . 4 1.2 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Scenario 1: Leaf OR Root site(s) per PE . . . . . . . . . . 5 2 E-Tree Scenarios . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Scenario 2: Leaf OR Root site(s) per AC . . . . . . . . . . 5 2.1 Scenario 1: Leaf or Root Site(s) per PE . . . . . . . . . . 5
2.3 Scenario 3: Leaf OR Root site(s) per MAC . . . . . . . . . . 7 2.2 Scenario 2: Leaf or Root Site(s) per AC . . . . . . . . . . 6
3 Operation for EVPN . . . . . . . . . . . . . . . . . . . . . . . 7 2.3 Scenario 3: Leaf or Root Site(s) per MAC Address . . . . . . 8
3.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 8 3 Operation for EVPN . . . . . . . . . . . . . . . . . . . . . . . 9
3.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 9 3.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 9
3.2.1 BUM traffic originated from a single-homed site on a 3.2 Broadcast, Unkonwn, and Multicast (BUM) Traffic . . . . . . 10
leaf AC . . . . . . . . . . . . . . . . . . . . . . . . 9 3.2.1 BUM Traffic Originated from a Single-homed Site on a
3.2.2 BUM traffic originated from a single-homed site on a Leaf AC . . . . . . . . . . . . . . . . . . . . . . . . 11
root AC . . . . . . . . . . . . . . . . . . . . . . . . 10 3.2.2 BUM Traffic Originated from a Single-homed Site on a
3.2.3 BUM traffic originated from a multi-homed site on a Root AC . . . . . . . . . . . . . . . . . . . . . . . . 11
leaf AC . . . . . . . . . . . . . . . . . . . . . . . . 10 3.2.3 BUM Traffic Originated from a Multi-homed Site on a
3.2.4 BUM traffic originated from a multi-homed site on a Leaf AC . . . . . . . . . . . . . . . . . . . . . . . . 11
root AC . . . . . . . . . . . . . . . . . . . . . . . . 10 3.2.4 BUM Traffic Originated from a Multi-homed Site on a
3.3 E-TREE Traffic Flows for EVPN . . . . . . . . . . . . . . . 10 Root AC . . . . . . . . . . . . . . . . . . . . . . . . 11
3.3.1 E-Tree with MAC Learning . . . . . . . . . . . . . . . . 11 3.3 E-Tree Traffic Flows for EVPN . . . . . . . . . . . . . . . 12
3.3.2 E-Tree without MAC Learning . . . . . . . . . . . . . . 12 3.3.1 E-Tree with MAC Learning . . . . . . . . . . . . . . . . 12
4 Operation for PBB-EVPN . . . . . . . . . . . . . . . . . . . . . 12 3.3.2 E-Tree without MAC Learning . . . . . . . . . . . . . . 13
4.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 13 4 Operation for PBB-EVPN . . . . . . . . . . . . . . . . . . . . . 13
4.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 13 4.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 14
4.3 E-Tree without MAC Learning . . . . . . . . . . . . . . . . 13 4.2 Broadcast, Unkonwn, and Multicast (BUM) Traffic . . . . . . 14
5 BGP Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 14 4.3 E-Tree without MAC Learning . . . . . . . . . . . . . . . . 15
5.1 E-Tree Extended Community . . . . . . . . . . . . . . . . . 14 5 BGP Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.2 PMSI Tunnel Attribute . . . . . . . . . . . . . . . . . . . 15 5.1 E-Tree Extended Community . . . . . . . . . . . . . . . . . 15
6 Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . 16 5.2 PMSI Tunnel Attribute . . . . . . . . . . . . . . . . . . . 17
7 Security Considerations . . . . . . . . . . . . . . . . . . . . 16 6 Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . 18
8 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 16 7 Security Considerations . . . . . . . . . . . . . . . . . . . . 18
8.1 Considerations for PMSI Tunnel Types . . . . . . . . . . . . 17 8 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 18
9 References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 8.1 Considerations for PMSI Tunnel Types . . . . . . . . . . . . 18
9.1 Normative References . . . . . . . . . . . . . . . . . . . 17 9 References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
9.2 Informative References . . . . . . . . . . . . . . . . . . 18 9.1 Normative References . . . . . . . . . . . . . . . . . . . 19
Appendix-A . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 9.2 Informative References . . . . . . . . . . . . . . . . . . 20
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Appendix-A . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
1 Introduction 1 Introduction
The Metro Ethernet Forum (MEF) has defined a rooted-multipoint The Metro Ethernet Forum (MEF) has defined a rooted-multipoint
Ethernet service known as Ethernet Tree (E-Tree) [MEF6.1]. In an E- Ethernet service known as Ethernet Tree (E-Tree) [MEF6.1]. In an E-
Tree service, Attachment Circuits (ACs) are labeled as either Root or Tree service, a customer site that is typically represented by an
Leaf ACs. Root ACs can communicate with all other ACs. Leaf ACs can Attachment Circuits (AC) (e.g., an Ethernet tag but may also be
communicate with Root ACs but not with other Leaf ACs. represented by a MAC address) is labeled as either a Root or a Leaf
site. Root sites can communicate with all other customer sites (both
Root and Leaf sites). However, Leaf sites can communicate with Root
sites but not with other Leaf sits. In this document unless
explicitly mentioned otherwise, a site is always represented by an
AC.
[RFC7387] proposes the solution framework for supporting E-Tree [RFC7387] describes a solution framework for supporting E-Tree
service in MPLS networks. The document identifies the functional service in MPLS networks. The document identifies the functional
components of the overall solution to emulate E-Tree services in components of an overall solution to emulate E-Tree services in MPLS
addition to Ethernet LAN (E-LAN) services on an existing MPLS networks in addition to multipoint-to-multipoint Ethernet LAN (E-LAN)
network. services specified in [RFC7432] and [RFC7623].
[RFC7432] is a solution for multipoint L2VPN services, with advanced [RFC7432] defines EVPN, a solution for multipoint L2VPN services with
multi-homing capabilities, using BGP for distributing customer/client advanced multi-homing capabilities, using BGP for distributing
MAC address reach-ability information over the MPLS/IP network. customer/client MAC address reach-ability information over the
[RFC7623] combines the functionality of EVPN with [802.1ah] Provider MPLS/IP network. [RFC7623] combines the functionality of EVPN with
Backbone Bridging (PBB) for MAC address scalability. [802.1ah] Provider Backbone Bridging (PBB) for MAC address
scalability.
This document discusses how the functional requirements for E-Tree This document discusses how the functional requirements for E-Tree
service can be met with (PBB-)EVPN and how (PBB-)EVPN offers a more service can be met with a solution based on (PBB-)EVPN (i.e.,
efficient implementation of these functions. This document makes use [RFC7432] and [RFC7623]) with some extensions and how such a solution
of the most significant bit of the scope governed by the IANA can offer a more efficient implementation of these functions than
registry created by RFC7385, and hence updates RFC7385 accordingly. that of RFC7796, E-Tree Support in Virtual Private LAN Service
Section 2 discusses E-TREE scenarios. Section 3 and 4 describe E-TREE (VPLS). Since this document specifies a solution based on [RFC7432],
solutions for EVPN and PBB-EVPN respectively, and section 5 covers it requires the readers to have the knowledge of [RFC7432] as
BGP encoding for E-TREE solutions. prerequisite. This document makes use of the most significant bit of
the "Tunnel Type" field (in PMSI Tunnel Attribute) governed by the
IANA registry created by RFC7385, and hence updates RFC7385
accordingly. Section 2 discusses E-Tree scenarios. Section 3 and 4
describe E-Tree solutions for EVPN and PBB-EVPN respectively, and
section 5 covers BGP encoding for E-Tree solutions.
1.1 Terminology 1.1 Specification of Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [KEYWORDS]. document are to be interpreted as described in RFC 2119 [KEYWORDS].
1.2 Terminology
Broadcast Domain: In a bridged network, the broadcast domain
corresponds to a Virtual LAN (VLAN), where a VLAN is typically
represented by a single VLAN ID (VID) but can be represented by
several VIDs where Shared VLAN Learning (SVL) is used per [802.1Q].
Bridge Table: An instantiation of a broadcast domain on a MAC-VRF.
CE: Customer Edge device, e.g., a host, router, or switch.
EVI: An EVPN instance spanning the Provider Edge (PE) devices
participating in that EVPN.
MAC-VRF: A Virtual Routing and Forwarding table for Media Access
Control (MAC) addresses on a PE.
Ethernet Segment (ES): When a customer site (device or network) is
connected to one or more PEs via a set of Ethernet links, then that
set of links is referred to as an 'Ethernet segment'.
Ethernet Segment Identifier (ESI): A unique non-zero identifier that
identifies an Ethernet segment is called an 'Ethernet Segment
Identifier'.
Ethernet Tag: An Ethernet tag identifies a particular broadcast
domain, e.g., a VLAN. An EVPN instance consists of one or more
broadcast domains.
P2MP: Point to Multipoint.
PE: Provider Edge device.
2 E-Tree Scenarios 2 E-Tree Scenarios
This document categorizes E-Tree scenarios into the following three This document categorizes E-Tree scenarios into the following three
scenarios, depending on the nature of the Root/Leaf site association: scenarios, depending on the nature of the Root/Leaf site association:
- Leaf OR Root site(s) per PE - Either Leaf or Root site(s) per PE
- Leaf OR Root site(s) per Attachment Circuit (AC) - Either Leaf or Root site(s) per Attachment Circuit (AC)
- Leaf OR Root site(s) per MAC - Either Leaf or Root site(s) per MAC address
2.1 Scenario 1: Leaf OR Root site(s) per PE 2.1 Scenario 1: Leaf or Root Site(s) per PE
In this scenario, a PE may receive traffic from either Root ACs OR In this scenario, a PE may receive traffic from either Root ACs or
Leaf ACs for a given MAC-VRF/bridge table, but not both concurrently. Leaf ACs for a given MAC-VRF/bridge table, but not both. In other
In other words, a given EVI on a PE is either associated with root(s) words, a given EVPN Instance (EVI) on a Provider Edge (PE) device is
or leaf(s). The PE may have both Root and Leaf ACs albeit for either associated with root(s) or leaf(s). The PE may have both Root
different EVIs. and Leaf ACs albeit for different EVIs.
+---------+ +---------+ +---------+ +---------+
| PE1 | | PE2 | | PE1 | | PE2 |
+---+ | +---+ | +------+ | +---+ | +---+ +---+ | +---+ | +------+ | +---+ | +---+
|CE1+---AC1----+--+ | | | MPLS | | | +--+----AC2-----+CE2| |CE1+---AC1----+--+ | | | MPLS | | | +--+----AC2-----+CE2|
+---+ (Root) | |MAC| | | /IP | | |MAC| | (Leaf) +---+ +---+ (Root) | |MAC| | | /IP | | |MAC| | (Leaf) +---+
| |VRF| | | | | |VRF| | | |VRF| | | | | |VRF| |
| | | | | | | | | | +---+ | | | | | | | | | | +---+
| | | | | | | | +--+----AC3-----+CE3| | | | | | | | | +--+----AC3-----+CE3|
| +---+ | +------+ | +---+ | (Leaf) +---+ | +---+ | +------+ | +---+ | (Leaf) +---+
+---------+ +---------+ +---------+ +---------+
Figure 1: Scenario 1 Figure 1: Scenario 1
In such scenario, using tailored BGP Route Target (RT) import/export In this scenario, tailored BGP Route Target (RT) import/export
policies among the PEs belonging to the same EVI, can be used to policies among the PEs belonging to the same EVI can be used to
restrict the communications among Leaf PEs. To restrict the prevent the communications among Leaf PEs. To prevent the
communications among Leaf ACs connected to the same PE and belonging communications among Leaf ACs connected to the same PE and belonging
to the same EVI, split-horizon filtering is used to block traffic to the same EVI, split-horizon filtering is used to block traffic
from one Leaf AC to another Leaf AC on a MAC-VRF for a given E-TREE from one Leaf AC to another Leaf AC on a MAC-VRF for a given E-Tree
EVI. The purpose of this topology constraint is to avoid having PEs EVI. The purpose of this topology constraint is to avoid having PEs
with only Leaf sites importing and processing BGP MAC routes from with only Leaf sites importing and processing BGP MAC routes from
each other. To support such topology constrain in EVPN, two BGP each other. To support such topology constrain in EVPN, two BGP
Route-Targets (RTs) are used for every EVPN Instance (EVI): one RT is Route-Targets (RTs) are used for every EVPN Instance (EVI): one RT is
associated with the Root sites (Root ACs) and the other is associated associated with the Root sites (Root ACs) and the other is associated
with the Leaf sites (Leaf ACs). On a per EVI basis, every PE exports with the Leaf sites (Leaf ACs). On a per EVI basis, every PE exports
the single RT associated with its type of site(s). Furthermore, a PE the single RT associated with its type of site(s). Furthermore, a PE
with Root site(s) imports both Root and Leaf RTs, whereas a PE with with Root site(s) imports both Root and Leaf RTs, whereas a PE with
Leaf site(s) only imports the Root RT. Leaf site(s) only imports the Root RT.
2.2 Scenario 2: Leaf OR Root site(s) per AC For this scenario, if it is desired to use only a single RT per EVI
(just like E-LAN services in [RFC7432]), then the approach B in
scenario 2 (described below) needs to be used.
2.2 Scenario 2: Leaf or Root Site(s) per AC
In this scenario, a PE can receive traffic from both Root ACs and In this scenario, a PE can receive traffic from both Root ACs and
Leaf ACs for a given EVI. In other words, a given EVI on a PE can be Leaf ACs for a given EVI. In other words, a given EVI on a PE can be
associated with both root(s) and leaf(s). associated with both root(s) and leaf(s).
+---------+ +---------+ +---------+ +---------+
| PE1 | | PE2 | | PE1 | | PE2 |
+---+ | +---+ | +------+ | +---+ | +---+ +---+ | +---+ | +------+ | +---+ | +---+
|CE1+-----AC1----+--+ | | | | | | +--+---AC2--+CE2| |CE1+-----AC1----+--+ | | | | | | +--+---AC2--+CE2|
+---+ (Leaf) | |MAC| | | MPLS | | |MAC| | (Leaf) +---+ +---+ (Leaf) | |MAC| | | MPLS | | |MAC| | (Leaf) +---+
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a Leaf or Root AC and thus support ingress filtering on the ingress a Leaf or Root AC and thus support ingress filtering on the ingress
PE with both Leaf and Root ACs, MAC addresses need to be colored with PE with both Leaf and Root ACs, MAC addresses need to be colored with
Root or Leaf indication before advertisements to other PEs. There are Root or Leaf indication before advertisements to other PEs. There are
two approaches for such coloring: two approaches for such coloring:
A) To always use two RTs (one to designate Leaf RT and another for A) To always use two RTs (one to designate Leaf RT and another for
Root RT) Root RT)
B) To allow for a single RT be used per EVI just like [RFC7432] and B) To allow for a single RT be used per EVI just like [RFC7432] and
thus color MAC addresses via a "color" flag in a new extended thus color MAC addresses via a "color" flag in a new extended
community as detailed in section 3.1. community as detailed in section 5.1.
Approach (A) would require the same data plane enhancements as Approach (A) would require the same data plane enhancements as
approach (B) if MAC-VRF and bridge tables used per VLAN, are to approach (B) if MAC-VRF/bridge tables used per broadcast domain
remain consistent with [RFC7432] (section 6). In order to avoid data- (e.g., VLAN) are to remain consistent with [RFC7432] (section 6). In
plane enhancements for approach (A), multiple bridge tables per VLAN order to avoid data-plane enhancements for approach (A), multiple
may be considered; however, this has major drawbacks as described in bridge tables per VLAN may be considered; however, this has major
appendix-A and thus is not recommended. drawbacks as described in appendix-A and thus is not recommended.
Given that both approaches (A) and (B) would require exact same data- Given that both approaches (A) and (B) would require exact same data-
plane enhancements, approach (B) is chosen here in order to allow for plane enhancements, approach (B) is chosen here in order to allow for
RT usage consistent with baseline EVPN [RFC7432] and for better RT usage consistent with baseline EVPN [RFC7432] and for better
generality. It should be noted that if one wants to use RT constrain generality. It should be noted that if one wants to use RT constrain
in order to avoid MAC advertisements associated with a Leaf AC to PEs in order to avoid MAC advertisements associated with a Leaf AC to PEs
with only Leaf ACs, then two RTs (one for Root and another for Leaf) with only Leaf ACs, then two RTs (one for Root and another for Leaf)
can still be used with approach (B); however, in such applications can still be used with approach (B); however, in such applications
Leaf/Root RTs will be used to constrain MAC advertisements and they Leaf/Root RTs will be used to constrain MAC advertisements and they
are not used to color the MAC routes for ingress filtering - i.e., in are not used to color the MAC routes for ingress filtering - i.e., in
approach (B), the coloring is always done via the new extended approach (B), the coloring is always done via the new extended
community. community.
For this scenario, if for a given EVI, significant number of PEs have For this scenario, if for a given EVI, significant number of PEs have
both Leaf and Root sites attached, even though they may start as both Leaf and Root sites attached, even though they may start as
Root-only or Leaf-only PEs, then a single RT per EVI should be used. Root-only or Leaf-only PEs, then a single RT per EVI should be used.
The reason for such recommendation is to alleviate the configuration The reason for such recommendation is to alleviate the configuration
overhead associated with using two RTs per EVI at the expense of overhead associated with using two RTs per EVI at the expense of
having some unwanted MAC addresses on the Leaf-only PEs. having some unwanted MAC addresses on the Leaf-only PEs.
2.3 Scenario 3: Leaf OR Root site(s) per MAC 2.3 Scenario 3: Leaf or Root Site(s) per MAC Address
In this scenario, a PE may receive traffic from both Root AND Leaf In this scenario, a customer Root or Leaf site is represented by a
MAC address and a PE may receive traffic from both Root AND Leaf
sites on a single Attachment Circuit (AC) of an EVI. This scenario is sites on a single Attachment Circuit (AC) of an EVI. This scenario is
not covered in both [RFC7387] and [MEF6.1]; however, it is covered in not covered in either [RFC7387] or [MEF6.1]; however, it is covered
this document for the sake of completeness. In this scenario, since in this document for the sake of completeness. In this scenario,
an AC carries traffic from both Root and Leaf sites, the granularity since an AC carries traffic from both Root and Leaf sites, the
at which Root or Leaf sites are identified is on a per MAC address. granularity at which Root or Leaf sites are identified is on a per
This scenario is considered in this document for EVPN service with MAC address. This scenario is considered in this document for EVPN
only known unicast traffic because the Designated Forwarding (DF) service with only known unicast traffic because the Designated
filtering per [RFC7432] would not be compatible with the required Forwarding (DF) filtering per [RFC7432] would not be compatible with
egress filtering - i.e., Broadcast, Unknown, and Multicast (BUM) the required egress filtering - i.e., Broadcast, Unknown, and
traffic is not supported in this scenario and it is dropped by the Multicast (BUM) traffic is not supported in this scenario and it is
ingress PE. dropped by the ingress PE.
For this scenario, the approach B in scenario 2 (described above) is
used in order to allow for single RT usage by service providers.
+---------+ +---------+ +---------+ +---------+
| PE1 | | PE2 | | PE1 | | PE2 |
+---+ | +---+ | +------+ | +---+ | +---+ +---+ | +---+ | +------+ | +---+ | +---+
|CE1+-----AC1----+--+ | | | | | | +--+-----AC2----+CE2| |CE1+-----AC1----+--+ | | | | | | +--+-----AC2----+CE2|
+---+ (Root) | | E | | | MPLS | | | E | | (Leaf/Root)+---+ +---+ (Root) | | E | | | MPLS | | | E | | (Leaf/Root)+---+
| | V | | | /IP | | | V | | | | V | | | /IP | | | V | |
| | I | | | | | | I | | +---+ | | I | | | | | | I | | +---+
| | | | | | | | +--+-----AC3----+CE3| | | | | | | | | +--+-----AC3----+CE3|
| +---+ | +------+ | +---+ | (Leaf) +---+ | +---+ | +------+ | +---+ | (Leaf) +---+
+---------+ +---------+ +---------+ +---------+
Figure 3: Scenario 3 Figure 3: Scenario 3
In conclusion, the approach B in scenario 2 is the recommended
approach across all the above three scenarios and the corresponding
solution is detailed in the following sections.
3 Operation for EVPN 3 Operation for EVPN
[RFC7432] defines the notion of Ethernet Segment Identifier (ESI) [RFC7432] defines the notion of Ethernet Segment Identifier (ESI)
MPLS label used for split-horizon filtering of BUM traffic at the MPLS label used for split-horizon filtering of BUM traffic at the
egress PE. Such egress filtering capabilities can be leveraged in egress PE. Such egress filtering capabilities can be leveraged in
provision of E-TREE services as seen shortly. In other words, provision of E-Tree services as it will be seen shortly for BUM
[RFC7432] has inherent capability to support E-TREE services without traffic. For know unicast traffic, additional extensions to [RFC7432]
defining any new BGP routes but by just defining a new BGP Extended is needed (i.e., a new BGP Extended Community for leaf indication
Community for leaf indication as shown later in this document described in section 5.1) in order to enable ingress filtering as
(section 5.1). described in detail in the following sections.
3.1 Known Unicast Traffic 3.1 Known Unicast Traffic
Since in EVPN, MAC learning is performed in control plane via Since in EVPN, MAC learning is performed in control plane via
advertisement of BGP routes, the filtering needed by E-TREE service advertisement of BGP routes, the filtering needed by E-Tree service
for known unicast traffic can be performed at the ingress PE, thus for known unicast traffic can be performed at the ingress PE, thus
providing very efficient filtering and avoiding sending known unicast providing very efficient filtering and avoiding sending known unicast
traffic over MPLS/IP core to be filtered at the egress PE as done in traffic over MPLS/IP core to be filtered at the egress PE as done in
traditional E-TREE solutions (e.g., E-TREE for VPLS [RFC7796]). traditional E-Tree solutions - i.e., E-Tree for VPLS [RFC7796].
To provide such ingress filtering for known unicast traffic, a PE To provide such ingress filtering for known unicast traffic, a PE
MUST indicate to other PEs what kind of sites (root or leaf) its MAC MUST indicate to other PEs what kind of sites (root or leaf) its MAC
addresses are associated with by advertising a leaf indication flag addresses are associated with. This is done by advertising a Leaf
(via an Extended Community) along with each of its MAC/IP indication flag (via an Extended Community) along with each of its
Advertisement routes. The lack of such flag indicates that the MAC MAC/IP Advertisement routes learned from a Leaf site. The lack of
address is associated with a root site. This scheme applies to all such flag indicates that the MAC address is associated with a root
scenarios described in section 2. site. This scheme applies to all scenarios described in section 2.
Tagging MAC addresses with a leaf indication enables remote PEs to Tagging MAC addresses with a Leaf indication enables remote PEs to
perform ingress filtering for known unicast traffic - i.e., on the perform ingress filtering for known unicast traffic - i.e., on the
ingress PE, the MAC destination address lookup yields, in addition to ingress PE, the MAC destination address lookup yields, in addition to
the forwarding adjacency, a flag which indicates whether the target the forwarding adjacency, a flag which indicates whether the target
MAC is associated with a Leaf site or not. The ingress PE cross- MAC is associated with a Leaf site or not. The ingress PE cross-
checks this flag with the status of the originating AC, and if both checks this flag with the status of the originating AC, and if both
are Leafs, then the packet is not forwarded. are leafs, then the packet is not forwarded.
In situation where MAC moves are allowed among Leaf and Root sites In situation where MAC moves are allowed among Leaf and Root sites
(e.g., non-static MAC), PEs can receive multiple MAC/IP (e.g., non-static MAC), PEs can receive multiple MAC/IP
advertisements routes for the same MAC address with different advertisements routes for the same MAC address with different
Leaf/Root indications (and possibly different ESIs for multi-homing Leaf/Root indications (and possibly different ESIs for multi-homing
scenarios). In such situations, MAC mobility procedures (section 15 scenarios). In such situations, MAC mobility procedures (section 15
of [RFC7432]) take precedence to first identify the location of the of [RFC7432]) take precedence to first identify the location of the
MAC before associating that MAC with a Root or a Leaf site. MAC before associating that MAC with a Root or a Leaf site.
To support the above ingress filtering functionality, a new E-TREE To support the above ingress filtering functionality, a new E-Tree
Extended Community with a Leaf indication flag is introduced [section Extended Community with a Leaf indication flag is introduced [section
5.2]. This new Extended Community MUST be advertised with MAC/IP 5.1]. This new Extended Community MUST be advertised with MAC/IP
Advertisement route. Besides MAC/IP Advertisement route, no other Advertisement route learned from a Leaf site. Besides MAC/IP
EVPN routes are required to carry this new extended community. Advertisement route, no other EVPN routes are required to carry this
new extended community.
3.2 BUM Traffic 3.2 Broadcast, Unkonwn, and Multicast (BUM) Traffic
This specification does not provide support for filtering BUM In this specification, the support for filtering BUM (Broadcast,
(Broadcast, Unknown, and Multicast) traffic on the ingress PE because Unknown, and Multicast) traffic does not include ingress filtering
it is not possible to perform filtering of BUM traffic on the ingress because it is not possible to do so, due to the multi-destination
PE, as is the case with known unicast described above, due to the nature of BUM traffic. As such, the solution relies on egress
multi-destination nature of BUM traffic. As such, the solution relies filtering. In order to apply the proper egress filtering, which
on egress filtering. In order to apply the proper egress filtering, varies based on whether a packet is sent from a Leaf AC or a root AC,
which varies based on whether a packet is sent from a Leaf AC or a the MPLS-encapsulated frames MUST be tagged with an indication when
root AC, the MPLS-encapsulated frames MUST be tagged with an they originated from a Leaf AC - i.e., to be tagged with a Leaf label
indication that they originated from a Leaf AC - i.e., to be tagged as specified in section 5.1. This Leaf label allows for disposition
with a Leaf label as specified in section 5.1. PE (e.g., egress PE) to perform the necessary egress filtering
function in data-plane similar to ESI label in [RFC7432]. The
allocation of the Leaf label is on a per PE basis (e.g., independent
of ESI and EVI) as descried in the following sections.
The Leaf label can be upstream assigned for P2MP LSP or downstream The Leaf label can be upstream assigned for P2MP LSP or downstream
assigned for ingress replication tunnels. The main difference between assigned for ingress replication tunnels. The main difference between
downstream and upstream assigned Leaf label is that in case of downstream and upstream assigned Leaf label is that in case of
downstream assigned not all egress PE devices need to receive the downstream assigned not all egress PE devices need to receive the
label just like ESI label for ingress replication procedures defined label in MPLS encapsulated BUM packets just like ESI label for
in [RFC7432]. ingress replication procedures defined in [RFC7432].
On the ingress PE, the PE needs to place all its Leaf ACs for a given On the ingress PE, the PE needs to place all its Leaf ACs for a given
bridge domain in a single split-horizon group in order to prevent bridge domain in a single split-horizon group in order to prevent
intra-PE forwarding among its Leaf ACs. This intra-PE split-horizon intra-PE forwarding among its Leaf ACs. This intra-PE split-horizon
filtering applies to BUM traffic as well as known-unicast traffic. filtering applies to BUM traffic as well as known-unicast traffic.
There are four scenarios to consider as follows. In all these There are four scenarios to consider as follows. In all these
scenarios, the ingress PE imposes the right MPLS label associated scenarios, the ingress PE imposes the right MPLS label associated
with the originated Ethernet Segment (ES) depending on whether the with the originated Ethernet Segment (ES) depending on whether the
Ethernet frame originated from a Root or a Leaf site on that Ethernet Ethernet frame originated from a Root or a Leaf site on that Ethernet
Segment (ESI label or Leaf label). The mechanism by which the PE Segment (ESI label or Leaf label). The mechanism by which the PE
identifies whether a given frame originated from a Root or a Leaf identifies whether a given frame originated from a Root or a Leaf
site on the segment is based on the AC identifier for that segment site on the segment is based on the AC identifier for that segment
(e.g., Ethernet Tag of the frame for 802.1Q frames). Other mechanisms (e.g., Ethernet Tag of the frame for 802.1Q frames). Other mechanisms
for identifying root or leaf (e.g., on a per MAC address basis) is for identifying root or Leaf sites such the use of source MAC address
beyond the scope of this document. of the receiving frame are optional. The scenarios below are
described in context of Root/Leaf AC; however, they can be extended
to Root/Leaf MAC address if needed.
3.2.1 BUM traffic originated from a single-homed site on a leaf AC 3.2.1 BUM Traffic Originated from a Single-homed Site on a Leaf AC
In this scenario, the ingress PE adds a Leaf label advertised using In this scenario, the ingress PE adds a Leaf label advertised using
the E-Tree Extended Community (Section 5.1) indicating a Leaf site. the E-Tree Extended Community (Section 5.1) indicating a Leaf site.
This Leaf label, used for single-homing scenarios, is not on a per ES This Leaf label, used for single-homing scenarios, is not on a per ES
basis but rather on a per PE basis - i.e., a single Leaf MPLS label basis but rather on a per PE basis - i.e., a single Leaf MPLS label
is used for all single-homed ES's on that PE. This Leaf label is is used for all single-homed ES's on that PE. This Leaf label is
advertised to other PE devices, using the E-TREE Extended Community advertised to other PE devices, using the E-Tree Extended Community
(section 5.1) along with an Ethernet A-D per ES route with ESI of (section 5.1) along with an Ethernet A-D per ES route with ESI of
zero and a set of Route Targets (RTs) corresponding to all EVIs on zero and a set of Route Targets (RTs) corresponding to all EVIs on
the PE with at least one leaf site per EVI. The set of Ethernet A-D the PE where each EVI has at least one Leaf site. Multiple Ethernet
per ES routes may be needed if the number of Route Targets (RTs) that A-D per ES routes will need to be advertised if the number of Route
need to be sent exceed the limit on a single route per [RFC7432]. The Targets (RTs) that need to be carried exceed the limit on a single
ESI for the Ethernet A-D per ES route is set to zero to indicate route per [RFC7432]. The ESI for the Ethernet A-D per ES route is set
single-homed sites. to zero to indicate single-homed sites.
When a PE receives this special Leaf label in the data path, it When a PE receives this special Leaf label in the data path, it
blocks the packet if the destination AC is of type Leaf; otherwise, blocks the packet if the destination AC is of type Leaf; otherwise,
it forwards the packet. it forwards the packet.
3.2.2 BUM traffic originated from a single-homed site on a root AC 3.2.2 BUM Traffic Originated from a Single-homed Site on a Root AC
In this scenario, the ingress PE does not add any ESI label or Leaf In this scenario, the ingress PE does not add any ESI label or Leaf
label and it operates per [RFC7432] procedures. label and it operates per [RFC7432] procedures.
3.2.3 BUM traffic originated from a multi-homed site on a leaf AC 3.2.3 BUM Traffic Originated from a Multi-homed Site on a Leaf AC
In this scenario, it is assumed that while different ACs (VLANs) on In this scenario, it is assumed that while different ACs (VLANs) on
the same ES could have different root/leaf designation (some being the same ES could have different Root/Leaf designation (some being
roots and some being leafs), the same VLAN does have the same roots and some being leafs), the same VLAN does have the same
root/leaf designation on all PEs on the same ES. Furthermore, it is Root/Leaf designation on all PEs on the same ES. Furthermore, it is
assumed that there is no forwarding among subnets - ie, the service assumed that there is no forwarding among subnets - ie, the service
is EVPN L2 and not EVPN IRB [EVPN-IRB]. IRB use cases described in is EVPN L2 and not EVPN IRB [EVPN-IRB]. IRB use cases described in
[EVPN-IRB] are outside the scope of this document. [EVPN-IRB] are outside the scope of this document.
In such scenarios, If a multicast or broadcast packet is originated In this scenario, If a multicast or broadcast packet is originated
from a leaf AC, then it only needs to carry Leaf label described in from a Leaf AC, then it only needs to carry Leaf label described in
section 3.2.1. This label is sufficient in providing the necessary section 3.2.1. This label is sufficient in providing the necessary
egress filtering of BUM traffic from getting sent to leaf ACs egress filtering of BUM traffic from getting sent to Leaf ACs
including the leaf AC on the same Ethernet Segment. including the Leaf AC on the same Ethernet Segment.
3.2.4 BUM traffic originated from a multi-homed site on a root AC 3.2.4 BUM Traffic Originated from a Multi-homed Site on a Root AC
In this scenario, both the ingress and egress PE devices follows the In this scenario, both the ingress and egress PE devices follows the
procedure defined in [RFC7432] for adding and/or processing an ESI procedure defined in [RFC7432] for adding and/or processing an ESI
MPLS label. MPLS label - i.e., existing procedures for BUM traffic in [RFC7432]
are sufficient and there is no need to add a Leaf label.
3.3 E-TREE Traffic Flows for EVPN 3.3 E-Tree Traffic Flows for EVPN
Per [RFC7387], a generic E-Tree service supports all of the following Per [RFC7387], a generic E-Tree service supports all of the following
traffic flows: traffic flows:
- Ethernet known unicast from Root to Roots & Leaf - Known unicast traffic from Root to Roots & Leaf
- Ethernet known unicast from Leaf to Root - Known unicast traffic from Leaf to Root
- Ethernet BUM traffic from Root to Roots & Leafs - BUM traffic from Root to Roots & Leafs
- Ethernet BUM traffic from Leaf to Roots - BUM traffic from Leaf to Roots
A particular E-Tree service may need to support all of the above A particular E-Tree service may need to support all of the above
types of flows or only a select subset, depending on the target types of flows or only a select subset, depending on the target
application. In the case where unicast flows need not be supported, application. In the case where only multicast and broadcast flows
the L2VPN PEs can avoid performing any MAC learning function. need to be supported, the L2VPN PEs can avoid performing any MAC
learning function.
The following subsections will describe the operation of EVPN to The following subsections will describe the operation of EVPN to
support E-Tree service with and without MAC learning. support E-Tree service with and without MAC learning.
3.3.1 E-Tree with MAC Learning 3.3.1 E-Tree with MAC Learning
The PEs implementing an E-Tree service must perform MAC learning when The PEs implementing an E-Tree service must perform MAC learning when
unicast traffic flows must be supported among Root and Leaf sites. In unicast traffic flows must be supported among Root and Leaf sites. In
this case, the PE(s) with Root sites performs MAC learning in the this case, the PE(s) with Root sites performs MAC learning in the
data-path over the Ethernet Segments, and advertises reachability in data-path over the Ethernet Segments, and advertises reachability in
EVPN MAC/IP Advertisement Routes. These routes will be imported by EVPN MAC/IP Advertisement Routes. These routes will be imported by
all PEs for that EVI (i.e., PEs that have Leaf sites as well as PEs all PEs for that EVI (i.e., PEs that have Leaf sites as well as PEs
that have Root sites). Similarly, the PEs with Leaf sites perform MAC that have Root sites). Similarly, the PEs with Leaf sites perform MAC
learning in the data-path over their Ethernet Segments, and advertise learning in the data-path over their Ethernet Segments, and advertise
reachability in EVPN MAC/IP Advertisement Routes. For the scenario reachability in EVPN MAC/IP Advertisement Routes. For scenarios where
described in section 2.1 (or possibly section 2.2), these routes are two different RTs are used per EVI (one to designate Root site and
another to designate Leaf site), the MAC/IP Advertisement routes are
imported only by PEs with at least one Root site in the EVI - i.e., a imported only by PEs with at least one Root site in the EVI - i.e., a
PE with only Leaf sites will not import these routes. PEs with Root PE with only Leaf sites will not import these routes. PEs with Root
and/or Leaf sites may use the Ethernet A-D routes for aliasing (in and/or Leaf sites may use the Ethernet A-D routes for aliasing (in
the case of multi-homed segments) and for mass MAC withdrawal per the case of multi-homed segments) and for mass MAC withdrawal per
[RFC7432]. [RFC7432].
To support multicast/broadcast from Root to Leaf sites, either a P2MP To support multicast/broadcast from Root to Leaf sites, either a P2MP
tree rooted at the PE(s) with the Root site(s) or ingress replication tree rooted at the PE(s) with the Root site(s) (e.g., Root PEs) or
can be used (section 16 of [RFC7432]). The multicast tunnels are set ingress replication can be used (section 16 of [RFC7432]). The
up through the exchange of the EVPN Inclusive Multicast route, as multicast tunnels are set up through the exchange of the EVPN
defined in [RFC7432]. Inclusive Multicast route, as defined in [RFC7432].
To support multicast/broadcast from Leaf to Root sites, ingress To support multicast/broadcast from Leaf to Root sites, either
replication should be sufficient for most scenarios where there are ingress replication tunnels from each Leaf PE or a P2MP tree rooted
only a few Roots (typically two). Therefore, in a typical scenario, a at each Leaf PE can be used. The following two paragraphs describes
root PE needs to support both a P2MP tunnel in transmit direction when each of these tunneling schemes can be used and how to signal
from itself to leaf PEs and at the same time it needs to support them.
ingress-replication tunnels in receive direction from leaf PEs to
itself. In order to signal this efficiently from the root PE, a new
composite tunnel type is defined per section 5.2. This new composite
tunnel type is advertised by the root PE to simultaneously indicate a
P2MP tunnel in transmit direction and an ingress-replication tunnel
in the receive direction for the BUM traffic.
If the number of Roots is large, P2MP tunnels originated at the PEs When there are only a few Root PEs with small amount of
with Leaf sites may be used and thus there will be no need to use the multicast/broadcast traffic from Leaf PEs toward Root PEs, then
modified PMSI tunnel attribute in section 5.2 for composite tunnel ingress replication tunnels from Leaf PEs toward Root PEs should be
type. sufficient. Therefore, if a root PE needs to support a P2MP tunnel in
transmit direction from itself to Leaf PEs and at the same time it
wants to support ingress-replication tunnels in receive direction,
the Root PE can signal it efficiently by using a new composite tunnel
type defined in section 5.2. This new composite tunnel type is
advertised by the root PE to simultaneously indicate a P2MP tunnel in
transmit direction and an ingress-replication tunnel in the receive
direction for the BUM traffic.
If the number of Root PEs is large, P2MP tunnels (e.g., mLDP or RSVP-
TE) originated at the Leaf PEs may be used and thus there will be no
need to use the modified PMSI tunnel attribute and the composite
tunnel type values defined in section 5.2.
3.3.2 E-Tree without MAC Learning 3.3.2 E-Tree without MAC Learning
The PEs implementing an E-Tree service need not perform MAC learning The PEs implementing an E-Tree service need not perform MAC learning
when the traffic flows between Root and Leaf sites are mainly when the traffic flows between Root and Leaf sites are mainly
multicast or broadcast. In this case, the PEs do not exchange EVPN multicast or broadcast. In this case, the PEs do not exchange EVPN
MAC/IP Advertisement Routes. Instead, the Inclusive Multicast MAC/IP Advertisement Routes. Instead, the Inclusive Multicast
Ethernet Tag route is used to support BUM traffic. Ethernet Tag route is used to support BUM traffic.
The fields of this route are populated per the procedures defined in The fields of this route are populated per the procedures defined in
[RFC7432], and the multicast tunnel setup criteria are as described [RFC7432], and the multicast tunnel setup criteria are as described
in the previous section. in the previous section.
Just as in the previous section, if the number of PEs with root sites Just as in the previous section, if the number of Root PEs are only a
are only a few and thus ingress replication is desired from leaf PEs few and thus ingress replication is desired from Leaf PEs to these
to these root PEs, then the modified PMSI attribute as defined in root PEs, then the modified PMSI attribute and the composite tunnel
section 5.2 should be used. type values defined in section 5.2 should be used.
4 Operation for PBB-EVPN 4 Operation for PBB-EVPN
In PBB-EVPN, the PE advertises a Root/Leaf indication along with each In PBB-EVPN, the PE advertises a Root/Leaf indication along with each
B-MAC Advertisement route, to indicate whether the associated B-MAC B-MAC Advertisement route, to indicate whether the associated B-MAC
address corresponds to a Root or a Leaf site. Just like the EVPN address corresponds to a Root or a Leaf site. Just like the EVPN
case, the new E-TREE Extended Community defined in section [5.1] is case, the new E-Tree Extended Community defined in section [5.1] is
advertised with each MAC Advertisement route. advertised with each EVPN MAC/IP Advertisement route.
In the case where a multi-homed Ethernet Segment has both Root and In the case where a multi-homed Ethernet Segment has both Root and
Leaf sites attached, two B-MAC addresses are advertised: one B-MAC Leaf sites attached, two B-MAC addresses are advertised: one B-MAC
address is per ES as specified in [RFC7623] and implicitly denoting address is per ES as specified in [RFC7623] and implicitly denoting
Root, and the other B-MAC address is per PE and explicitly denoting Root, and the other B-MAC address is per PE and explicitly denoting
Leaf. The former B-MAC address is not advertised with the E-TREE Leaf. The former B-MAC address is not advertised with the E-Tree
extended community but the latter B-MAC denoting Leaf is advertised extended community but the latter B-MAC denoting Leaf is advertised
with the new E-TREE extended community where "Leaf-indication" flag with the new E-Tree extended community where "Leaf-indication" flag
is set. In such multi-homing scenarios where an Ethernet Segment has is set. In such multi-homing scenarios where an Ethernet Segment has
both Root and Leaf ACs, it is assumed that While different ACs both Root and Leaf ACs, it is assumed that While different ACs
(VLANs) on the same ES could have different root/leaf designation (VLANs) on the same ES could have different Root/Leaf designation
(some being roots and some being leafs), the same VLAN does have the (some being Roots and some being Leafs), the same VLAN does have the
same root/leaf designation on all PEs on the same ES. Furthermore, it same Root/Leaf designation on all PEs on the same ES. Furthermore, it
is assumed that there is no forwarding among subnets - ie, the is assumed that there is no forwarding among subnets - ie, the
service is L2 and not IRB. IRB use case is outside the scope of this service is L2 and not IRB. IRB use case is outside the scope of this
document. document.
The ingress PE uses the right B-MAC source address depending on The ingress PE uses the right B-MAC source address depending on
whether the Ethernet frame originated from the Root or Leaf AC on whether the Ethernet frame originated from the Root or Leaf AC on
that Ethernet Segment. The mechanism by which the PE identifies that Ethernet Segment. The mechanism by which the PE identifies
whether a given frame originated from a Root or Leaf site on the whether a given frame originated from a Root or Leaf site on the
segment is based on the Ethernet Tag associated with the frame. Other segment is based on the Ethernet Tag associated with the frame. Other
mechanisms of identification, beyond the Ethernet Tag, are outside mechanisms of identification, beyond the Ethernet Tag, are outside
skipping to change at page 13, line 18 skipping to change at page 14, line 39
addresses for traffic originating from single-homed segments. The B- addresses for traffic originating from single-homed segments. The B-
MAC address used for indicating Leaf sites can be the same for both MAC address used for indicating Leaf sites can be the same for both
single-homed and multi-homed segments. single-homed and multi-homed segments.
4.1 Known Unicast Traffic 4.1 Known Unicast Traffic
For known unicast traffic, the PEs perform ingress filtering: On the For known unicast traffic, the PEs perform ingress filtering: On the
ingress PE, the C-MAC destination address lookup yields, in addition ingress PE, the C-MAC destination address lookup yields, in addition
to the target B-MAC address and forwarding adjacency, a flag which to the target B-MAC address and forwarding adjacency, a flag which
indicates whether the target B-MAC is associated with a Root or a indicates whether the target B-MAC is associated with a Root or a
Leaf site. The ingress PE cross-checks this flag with the status of Leaf site. The ingress PE also checks the status of the originating
the originating site, and if both are a Leaf, then the packet is not site, and if both are a Leaf, then the packet is not forwarded.
forwarded.
4.2 BUM Traffic 4.2 Broadcast, Unkonwn, and Multicast (BUM) Traffic
For BUM traffic, the PEs must perform egress filtering. When a PE For BUM traffic, the PEs must perform egress filtering. When a PE
receives a MAC advertisement route (which will be used as a source B- receives an EVPN MAC/IP advertisement route (which will be used as a
MAC for BUM traffic), it updates its egress filtering (based on the source B-MAC for BUM traffic), it updates its egress filtering (based
source B-MAC address), as follows: on the source B-MAC address), as follows:
- If the MAC Advertisement route indicates that the advertised B-MAC - If the EVPN MAC/IP Advertisement route indicates that the
is a Leaf, and the local Ethernet Segment is a Leaf as well, then the advertised B-MAC is a Leaf, and the local Ethernet Segment is a Leaf
source B-MAC address is added to its B-MAC list used for egress as well, then the source B-MAC address is added to its B-MAC list
filtering - i.e., to block traffic from that B-MAC address. used for egress filtering - i.e., to block traffic from that B-MAC
address.
- Otherwise, the B-MAC filtering list is not updated. - Otherwise, the B-MAC filtering list is not updated.
- If the EVPN MAC/IP Advertisement route indicates that the
advertised B-MAC has changed its designation from a Leaf to a Root
and the local Ethernet Segment is a Leaf, then the source B-MAC
address is removed from the B-MAC list corresponding to the local
Ethernet Segment used for egress filtering - i.e., to unblock traffic
from that B-MAC address.
When the egress PE receives the packet, it examines the B-MAC source When the egress PE receives the packet, it examines the B-MAC source
address to check whether it should filter or forward the frame. Note address to check whether it should filter or forward the frame. Note
that this uses the same filtering logic as baseline [RFC7623] and that this uses the same filtering logic as baseline [RFC7623] for an
does not require any additional flags in the data-plane. ESI and does not require any additional flags in the data-plane.
Just as in section 3.2, the PE places all Leaf Ethernet Segments of a Just as in section 3.2, the PE places all Leaf Ethernet Segments of a
given bridge domain in a single split-horizon group in order to given bridge domain in a single split-horizon group in order to
prevent intra-PE forwarding among Leaf segments. This split-horizon prevent intra-PE forwarding among Leaf segments. This split-horizon
function applies to BUM traffic as well as known-unicast traffic. function applies to BUM traffic as well as known-unicast traffic.
4.3 E-Tree without MAC Learning 4.3 E-Tree without MAC Learning
In scenarios where the traffic of interest is only Multicast and/or In scenarios where the traffic of interest is only Multicast and/or
broadcast, the PEs implementing an E-Tree service do not need to do broadcast, the PEs implementing an E-Tree service do not need to do
any MAC learning. In such scenarios the filtering must be performed any MAC learning. In such scenarios the filtering must be performed
on egress PEs. For PBB-EVPN, the handling of such traffic is per on egress PEs. For PBB-EVPN, the handling of such traffic is per
section 4.2 without C-MAC learning part of it at both ingress and section 4.2 without the need for C-MAC learning (in data-plane) in I-
egress PEs. component (C-bridge table) of PBB-EVPN PEs (at both ingress and
egress PEs).
5 BGP Encoding 5 BGP Encoding
This document defines a new BGP Extended Community for EVPN. This document defines a new BGP Extended Community for EVPN.
5.1 E-Tree Extended Community 5.1 E-Tree Extended Community
This Extended Community is a new transitive Extended Community This Extended Community is a new transitive Extended Community
[RFC4360] having a Type field value of 0x06 (EVPN) and the Sub-Type [RFC4360] having a Type field value of 0x06 (EVPN) and the Sub-Type
0x05. It is used for leaf indication of known unicast and BUM 0x05. It is used for Leaf indication of known unicast and BUM
traffic. traffic. It indicates that the frame is originated from a Leaf site.
The E-TREE Extended Community is encoded as an 8-octet value as The E-Tree Extended Community is encoded as an 8-octet value as
follows: follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=0x06 | Sub-Type=0x05 | Flags(1 Octet)| Reserved=0 | | Type=0x06 | Sub-Type=0x05 | Flags(1 Octet)| Reserved=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved=0 | Leaf Label | | Reserved=0 | Leaf Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: E-TREE Extended Community Figure 4: E-Tree Extended Community
The Flags field has the following format: The Flags field has the following format:
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
| reserved |L| | MBZ |L| (MBZ = Must Be Zero)
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
This document defines the following flags: This document defines the following flags:
+ Leaf-Indication (L) + Leaf-Indication (L)
A value of one indicates a Leaf AC/Site. The rest of flag bits are A value of one indicates a Leaf AC/Site. The rest of flag bits are
reserved and should be set to zero. reserved and should be set to zero.
When this Extended Community (EC) is advertised along with MAC/IP When this Extended Community (EC) is advertised along with MAC/IP
Advertisement route (for known unicast traffic) per section 3.1, the Advertisement route (for known unicast traffic) per section 3.1, the
Leaf-Indication flag MUST be set to one and Leaf Label SHOULD be set Leaf-Indication flag MUST be set to one and Leaf Label SHOULD be set
to zero. The label value is encoded in the high-order 20 bits of the to zero. The value of the 20-bit MPLS label is encoded in the high-
Leaf Label field. The received PE SHOULD ignore Leaf Label and only order 20 bits of the Leaf Label field. The receiving PE SHOULD ignore
processes Leaf-Indication flag. A value of zero for Leaf-Indication Leaf Label and only processes Leaf-Indication flag. A value of zero
flag is invalid when sent along with MAC/IP advertisement route and for Leaf-Indication flag is invalid when sent along with MAC/IP
an error should be logged. advertisement route and an error should be logged.
When this EC is advertised along with Ethernet A-D per ES route (with When this EC is advertised along with Ethernet A-D per ES route (with
ESI of zero) for BUM traffic to enable egress filtering on ESI of zero) for BUM traffic to enable egress filtering on
disposition PEs per sections 3.2.1 and 3.2.3, the Leaf Label MUST be disposition PEs per sections 3.2.1 and 3.2.3, the Leaf Label MUST be
set to a valid MPLS label (i.e., non-reserved assigned MPLS label set to a valid MPLS label (i.e., non-reserved assigned MPLS label
[RFC3032]) and the Leaf-Indication flag SHOULD be set to zero. The [RFC3032]) and the Leaf-Indication flag SHOULD be set to zero. The
received PE SHOULD ignore the Leaf-Indication flag. A non-valid MPLS receiving PE SHOULD ignore the Leaf-Indication flag. A non-valid MPLS
label when sent along with the Ethernet A-D per ES route, should be label when sent along with the Ethernet A-D per ES route, should be
ignored and logged as an error. ignored and logged as an error.
The reserved bits should be set to zero by the transmitter and should The reserved bits SHOULD be set to zero by the transmitter and SHOULD
be ignored by the receiver. be ignored by the receiver.
5.2 PMSI Tunnel Attribute 5.2 PMSI Tunnel Attribute
[RFC6514] defines PMSI Tunnel attribute which is an optional [RFC6514] defines PMSI Tunnel attribute which is an optional
transitive attribute with the following format: transitive attribute with the following format:
+---------------------------------+ +---------------------------------+
| Flags (1 octet) | | Flags (1 octet) |
+---------------------------------+ +---------------------------------+
| Tunnel Type (1 octets) | | Tunnel Type (1 octet) |
+---------------------------------+ +---------------------------------+
| MPLS Label (3 octets) | | Ingress Replication MPLS Label |
| (3 octets) |
+---------------------------------+ +---------------------------------+
| Tunnel Identifier (variable) | | Tunnel Identifier (variable) |
+---------------------------------+ +---------------------------------+
Figure 5: PMSI Tunnel Attribute Figure 5: PMSI Tunnel Attribute
This document defines a new Composite tunnel type by introducing a This document defines a new Composite tunnel type by introducing a
new 'Composite Tunnel' bit in the Tunnel Type field and adding a MPLS new 'Composite Tunnel' bit in the Tunnel Type field and adding a MPLS
label to the Tunnel Identifier field of PMSI Tunnel attribute as label to the Tunnel Identifier field of PMSI Tunnel attribute as
detailed below. This document uses all other remaining fields per detailed below. This document uses all other remaining fields per
existing definition. Composite tunnel type is advertised by the root existing definition. Composite tunnel type is advertised by the root
PE to simultaneously indicate a non-ingress replication tunnel (e.g., PE to simultaneously indicate a non-(ingress replication) tunnel
P2MP tunnel) in transmit direction and an ingress-replication tunnel (e.g., P2MP tunnel) in transmit direction and an ingress-replication
in the receive direction for the BUM traffic. tunnel in the receive direction for the BUM traffic.
When receiver ingress-replication label is needed, the high-order bit When receiver ingress-replication label is needed, the high-order bit
of the tunnel type field (Composite Tunnel bit) is set while the of the tunnel type field (Composite Tunnel bit) is set while the
remaining low-order seven bits indicate the tunnel type as before. remaining low-order seven bits indicate the tunnel type as before
(for the existing tunnel types). When this Composite Tunnel bit is
When this Composite Tunnel bit is set, the "tunnel identifier" field set, the "tunnel identifier" field begins with a three-octet label,
would begin with a three-octet label, followed by the actual tunnel followed by the actual tunnel identifier for the transmit tunnel.
identifier for the transmit tunnel. PEs that don't understand the PEs that don't understand the new meaning of the high-order bit would
new meaning of the high-order bit would treat the tunnel type as an treat the tunnel type as an undefined tunnel type and would treat the
undefined tunnel type and would treat the PMSI tunnel attribute as a PMSI tunnel attribute as a malformed attribute [RFC6514]. That is why
malformed attribute [RFC6514]. For the PEs that do understand the new the composite tunnel bit is allocated in the Tunnel Type field rather
meaning of the high-order, if ingress replication is desired when than the Flags field. For the PEs that do understand the new meaning
sending BUM traffic, the PE will use the the label in the Tunnel of the high-order, if ingress replication is desired when sending BUM
Identifier field when sending its BUM traffic. traffic, the PE will use the the label in the Tunnel Identifier field
when sending its BUM traffic.
Using the Composite Tunnel bit for Tunnel Types 0x00 'no tunnel Using the Composite Tunnel bit for Tunnel Types 0x00 'no tunnel
information present' and 0x06 'Ingress Replication' is invalid, and a information present' and 0x06 'Ingress Replication' is invalid, and a
PE that receives a PMSI Tunnel attribute with such information, PE that receives a PMSI Tunnel attribute with such information,
considers it as malformed and it SHOULD treat this Update as though considers it as malformed and it SHOULD treat this Update as though
all the routes contained in this Update had been withdrawn per all the routes contained in this Update had been withdrawn per
section 5 of [RFC6514]. section 5 of [RFC6514].
6 Acknowledgement 6 Acknowledgement
We would like to thank Dennis Cai, Antoni Przygienda, and Jeffrey We would like to thank Eric Rosen, Jeffrey Zhang, Dennis Cai, and
Zhang for their valuable comments. The authors would also like to Antoni Przygienda for their valuable comments. The authors would also
thank Thomas Morin for shepherding this document and providing like to thank Thomas Morin for shepherding this document and
valuable comments. providing valuable comments.
7 Security Considerations 7 Security Considerations
Since this document uses the EVPN constructs of [RFC7432] and Since this document uses the EVPN constructs of [RFC7432] and
[RFC7623], the same security considerations in these documents are [RFC7623], the same security considerations in these documents are
also applicable here. Furthermore, this document provides additional also applicable here. Furthermore, this document provides additional
security check by allowing sites (or ACs) of an EVPN instance to be security check by allowing sites (or ACs) of an EVPN instance to be
designated as "Root" or "Leaf" and preventing any traffic exchange designated as "Root" or "Leaf" and preventing any traffic exchange
among "Leaf" sites of that VPN through ingress filtering for known among "Leaf" sites of that VPN through ingress filtering for known
unicast traffic and egress filtering for BUM traffic. unicast traffic and egress filtering for BUM traffic.
8 IANA Considerations 8 IANA Considerations
IANA has allocated value 5 in the "EVPN Extended Community Sub-Types" IANA has allocated value 5 in the "EVPN Extended Community Sub-Types"
registry defined in [RFC7153] as follow: registry defined in [RFC7153] as follow:
SUB-TYPE VALUE NAME Reference SUB-TYPE VALUE NAME Reference
0x05 E-TREE Extended Community This document 0x05 E-Tree Extended Community This document
This document creates a one-octet registry called "E-Tree Flags". This document creates a one-octet registry called "E-Tree Flags".
New registrations will be made through the "RFC Required" procedure New registrations will be made through the "RFC Required" procedure
defined in [RFC5226]. Initial registrations are as follows: defined in [RFC8126]. Initial registrations are as follows:
bit Name Reference bit Name Reference
0-6 Reserved This document 0-6 Unassigned
7 Leaf-Indication This document 7 Leaf-Indication This document
8.1 Considerations for PMSI Tunnel Types 8.1 Considerations for PMSI Tunnel Types
The "P-Multicast Service Interface Tunnel (PMSI Tunnel) Tunnel Types" The "P-Multicast Service Interface Tunnel (PMSI Tunnel) Tunnel Types"
registry in the "Border Gateway Protocol (BGP) Parameters" registry registry in the "Border Gateway Protocol (BGP) Parameters" registry
needs to be updated to reflect the use of the most significant bit as needs to be updated to reflect the use of the most significant bit as
"Composite Tunnel" bit (section 5.2). "Composite Tunnel" bit (section 5.2).
For this purpose, this document updates [RFC7385]. For this purpose, this document updates [RFC7385].
The registry is to be updated, by removing the entries for 0xFB-0xFE The registry is to be updated, by removing the entries for 0xFB-0xFE
and 0x0F, and replacing them by: and 0x0F, and replacing them by:
Value Meaning Reference Value Meaning Reference
0x0B-0x7A Unassigned 0x0C-0x7A Unassigned
0x7B-0x7E Reserved for Experimental Use this document 0x7B-0x7E Experimental this document
0x7F Reserved this document 0x7F Reserved this document
0x80-0xFF Reserved for Composite Tunnels this document 0x80-0xFA Reserved for Composite tunnel this document
0xFB-0xFE Experimental [RFC7385]
0xFF Reserved [RFC7385]
The allocation policy for values 0x00 to 0x7A is IETF Review The allocation policy for values 0x00 to 0x7A is IETF Review
[RFC5226]. The range for experimental use is now 0x7B-0x7E, and value [RFC8126]. The range for experimental use is now 0x7B-0x7E, and value
in this range are not to be assigned. The status of 0x7F may only be in this range are not to be assigned. The status of 0x7F may only be
changed through Standards Action [RFC5226]. changed through Standards Action [RFC8126].
9 References 9 References
9.1 Normative References 9.1 Normative References
[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5226] T. Narten et al, "Guidelines for Writing an IANA [RFC8126] Cotton et al, "Guidelines for Writing an IANA
Considerations Section in RFCs", May, 2008. Considerations Section in RFCs", June, 2017.
[RFC7387] Key et al., "A Framework for E-Tree Service over MPLS [RFC7387] Key et al., "A Framework for E-Tree Service over MPLS
Network", October 2014. Network", October 2014.
[MEF6.1] Metro Ethernet Forum, "Ethernet Services Definitions - Phase [MEF6.1] Metro Ethernet Forum, "Ethernet Services Definitions - Phase
2", MEF 6.1, April 2008. 2", MEF 6.1, April 2008, https://mef.net/PDF_Documents/technical-
specifications/MEF6-1.pdf
[RFC7432] Sajassi et al., "BGP MPLS Based Ethernet VPN", February, [RFC7432] Sajassi et al., "BGP MPLS Based Ethernet VPN", February,
2015. 2015.
[RFC7623] Sajassi et al., "Provider Backbone Bridging Combined with [RFC7623] Sajassi et al., "Provider Backbone Bridging Combined with
Ethernet VPN (PBB-EVPN)", September, 2015. Ethernet VPN (PBB-EVPN)", September, 2015.
[RFC7385] Andersson et al., "IANA Registry for P-Multicast Service [RFC7385] Andersson et al., "IANA Registry for P-Multicast Service
Interface (PMSI) Tunnel Type Code Points", October, 2014. Interface (PMSI) Tunnel Type Code Points", October, 2014.
skipping to change at page 18, line 38 skipping to change at page 20, line 28
[RFC3032] E. Rosen et al, "MPLS Label Stack Encoding", January 2001. [RFC3032] E. Rosen et al, "MPLS Label Stack Encoding", January 2001.
[RFC7796] Y. Jiang et al, "Ethernet-Tree (E-Tree) Support in Virtual [RFC7796] Y. Jiang et al, "Ethernet-Tree (E-Tree) Support in Virtual
Private LAN Service (VPLS)", March 2016. Private LAN Service (VPLS)", March 2016.
[EVPN-IRB] A. Sajassi et al, "Integrated Routing and Bridging in [EVPN-IRB] A. Sajassi et al, "Integrated Routing and Bridging in
EVPN", draft-ietf-bess-evpn-inter-subnet-forwarding-03, February 8, EVPN", draft-ietf-bess-evpn-inter-subnet-forwarding-03, February 8,
2017. 2017.
[802.1ah] IEEE, "IEEE Standard for Local and metropolitan area
networks - Media Access Control (MAC) Bridges and Virtual Bridged
Local Area Networks", Clauses 25 and 26, IEEE Std 802.1Q, DOI
10.1109/IEEESTD.2011.6009146.
Appendix-A Appendix-A
When two MAC-VRFs (two bridge tables per VLANs) are used for an E- When two MAC-VRFs (two bridge tables per VLANs) are used for an E-
TREE service (one for root ACs and another for Leaf ACs) on a given Tree service (one for root ACs and another for Leaf ACs) on a given
PE, then the following complications in data-plane path can result. PE, then the following complications in data-plane path can result.
Maintaining two MAC-VRFs (two bridge tables) per VLAN (when both Leaf Maintaining two MAC-VRFs (two bridge tables) per VLAN (when both Leaf
and Root ACs exists for that VLAN) would either require two lookups and Root ACs exists for that VLAN) would either require two lookups
be performed per MAC address in each direction in case of a miss, or be performed per MAC address in each direction in case of a miss, or
duplicating many MAC addresses between the two bridge tables duplicating many MAC addresses between the two bridge tables
belonging to the same VLAN (same E-TREE instance). Unless two lookups belonging to the same VLAN (same E-Tree instance). Unless two lookups
are made, duplication of MAC addresses would be needed for both are made, duplication of MAC addresses would be needed for both
locally learned and remotely learned MAC addresses. Locally learned locally learned and remotely learned MAC addresses. Locally learned
MAC addresses from Leaf ACs need to be duplicated onto Root bridge MAC addresses from Leaf ACs need to be duplicated onto Root bridge
table and locally learned MAC addresses from Root ACs need to be table and locally learned MAC addresses from Root ACs need to be
duplicated onto Leaf bridge table. Remotely learned MAC addresses duplicated onto Leaf bridge table. Remotely learned MAC addresses
from Root ACs need to be copied onto both Root and Leaf bridge from Root ACs need to be copied onto both Root and Leaf bridge
tables. Because of potential inefficiencies associated with data- tables. Because of potential inefficiencies associated with data-
plane implementation of additional MAC lookup or duplication of MAC plane implementation of additional MAC lookup or duplication of MAC
entries, this option is not believed to be implementable without entries, this option is not believed to be implementable without
dataplane performance inefficiencies in some platforms and thus this dataplane performance inefficiencies in some platforms and thus this
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