draft-ietf-bess-evpn-etree-09.txt   draft-ietf-bess-evpn-etree-10.txt 
BESS Workgroup A. Sajassi, Ed. BESS Workgroup A. Sajassi, Ed.
INTERNET-DRAFT S. Salam INTERNET-DRAFT S. Salam
Intended Status: Standards Track Cisco Intended Status: Standards Track Cisco
Updates: RFC7385 J. Drake Updates: 7385 J. Drake
Juniper 6514 Juniper
J. Uttaro J. Uttaro
ATT ATT
S. Boutros S. Boutros
VMware VMware
J. Rabadan J. Rabadan
Nokia Nokia
Expires: June 12, 2017 January 12, 2017 Expires: November 9, 2017 May 9, 2017
E-TREE Support in EVPN & PBB-EVPN E-TREE Support in EVPN & PBB-EVPN
draft-ietf-bess-evpn-etree-09 draft-ietf-bess-evpn-etree-10
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 proposed in
and RFC called "A Framework for E-Tree Service over MPLS Network". RFC7387 ("A Framework for Ethernet Tree (E-Tree) Service over a
This document discusses how those functional requirements can be Multiprotocol Label Switching (MPLS) Network"). This document
easily met with (PBB-)EVPN and how (PBB-)EVPN offers a more efficient discusses how those functional requirements can be easily met with
Ethernet VPN (EVPN) and how EVPN offers a more efficient
implementation of these functions. This document makes use of the implementation of these functions. This document makes use of the
most significant bit of the scope governed by the IANA registry most significant bit of the scope governed by the IANA registry
created by RFC7385, and hence updates that RFC accordingly. created by RFC7385, and hence updates RFC7385 accordingly.
Status of this Memo Status of this Memo
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provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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skipping to change at page 1, line 46 skipping to change at page 2, line 4
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Copyright and License Notice Copyright and License Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
2 E-Tree Scenarios and EVPN / PBB-EVPN Support . . . . . . . . . 4 2 E-Tree Scenarios . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Scenario 1: Leaf OR Root site(s) per PE . . . . . . . . . . 4 2.1 Scenario 1: Leaf OR Root site(s) per PE . . . . . . . . . . 4
2.2 Scenario 2: Leaf OR Root site(s) per AC . . . . . . . . . . 5 2.2 Scenario 2: Leaf OR Root site(s) per AC . . . . . . . . . . 5
2.3 Scenario 3: Leaf OR Root site(s) per MAC . . . . . . . . . . 7 2.3 Scenario 3: Leaf OR Root site(s) per MAC . . . . . . . . . . 7
3 Operation for EVPN . . . . . . . . . . . . . . . . . . . . . . . 7 3 Operation for EVPN . . . . . . . . . . . . . . . . . . . . . . . 7
3.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 7 3.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 8
3.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 9 3.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2.1 BUM traffic originated from a single-homed site on a 3.2.1 BUM traffic originated from a single-homed site on a
leaf AC . . . . . . . . . . . . . . . . . . . . . . . . 10 leaf AC . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2.2 BUM traffic originated from a single-homed site on a 3.2.2 BUM traffic originated from a single-homed site on a
root AC . . . . . . . . . . . . . . . . . . . . . . . . 10 root AC . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2.3 BUM traffic originated from a multi-homed site on a 3.2.3 BUM traffic originated from a multi-homed site on a
leaf AC . . . . . . . . . . . . . . . . . . . . . . . . 10 leaf AC . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2.4 BUM traffic originated from a multi-homed site on a 3.2.4 BUM traffic originated from a multi-homed site on a
root AC . . . . . . . . . . . . . . . . . . . . . . . . 10 root AC . . . . . . . . . . . . . . . . . . . . . . . . 10
3.3 E-TREE Traffic Flows for EVPN . . . . . . . . . . . . . . . 11 3.3 E-TREE Traffic Flows for EVPN . . . . . . . . . . . . . . . 10
3.3.1 E-Tree with MAC Learning . . . . . . . . . . . . . . . . 11 3.3.1 E-Tree with MAC Learning . . . . . . . . . . . . . . . . 11
3.3.2 E-Tree without MAC Learning . . . . . . . . . . . . . . 12 3.3.2 E-Tree without MAC Learning . . . . . . . . . . . . . . 12
4 Operation for PBB-EVPN . . . . . . . . . . . . . . . . . . . . . 12 4 Operation for PBB-EVPN . . . . . . . . . . . . . . . . . . . . . 12
4.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 13 4.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 13
4.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 13 4.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 13
4.3 E-Tree without MAC Learning . . . . . . . . . . . . . . . . 14 4.3 E-Tree without MAC Learning . . . . . . . . . . . . . . . . 13
5 BGP Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5 BGP Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.1 E-TREE Extended Community . . . . . . . . . . . . . . . . . 14 5.1 E-TREE Extended Community . . . . . . . . . . . . . . . . . 14
5.2 PMSI Tunnel Attribute . . . . . . . . . . . . . . . . . . . 15 5.2 PMSI Tunnel Attribute . . . . . . . . . . . . . . . . . . . 15
6 Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . 16 6 Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . 16
7 Security Considerations . . . . . . . . . . . . . . . . . . . . 16 7 Security Considerations . . . . . . . . . . . . . . . . . . . . 16
8 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 16 8 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 16
8.1 Considerations for PMSI Tunnel Types . . . . . . . . . . . . 16 8.1 Considerations for PMSI Tunnel Types . . . . . . . . . . . . 16
9 References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 9 References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
9.1 Normative References . . . . . . . . . . . . . . . . . . . 17 9.1 Normative References . . . . . . . . . . . . . . . . . . . 17
9.2 Informative References . . . . . . . . . . . . . . . . . . 17 9.2 Informative References . . . . . . . . . . . . . . . . . . 17
Appendix-A . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
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). In an E-Tree Ethernet service known as Ethernet Tree (E-Tree) [MEF6.1]. In an E-
service, endpoints are labeled as either Root or Leaf sites. Root Tree service, Attachment Circuits (ACs) are labeled as either Root or
sites can communicate with all other sites. Leaf sites can Leaf ACs. Root ACs can communicate with all other ACs. Leaf ACs can
communicate with Root sites but not with other Leaf sites. communicate with Root ACs but not with other Leaf ACs.
[RFC7387] proposes the solution framework for supporting E-Tree [RFC7387] proposes the 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 the overall solution to emulate E-Tree services in
addition to Ethernet LAN (E-LAN) services on an existing MPLS addition to Ethernet LAN (E-LAN) services on an existing MPLS
network. network.
[RFC7432] is a solution for multipoint L2VPN services, with advanced [RFC7432] is a solution for multipoint L2VPN services, with advanced
multi-homing capabilities, using BGP for distributing customer/client multi-homing capabilities, using BGP for distributing customer/client
MAC address reach-ability information over the MPLS/IP network. MAC address reach-ability information over the MPLS/IP network.
[RFC7623] combines the functionality of EVPN with [802.1ah] Provider [RFC7623] combines the functionality of EVPN with [802.1ah] Provider
Backbone Bridging for MAC address scalability. 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 easily met with (PBB-)EVPN and how (PBB-)EVPN offers a service can be met with (PBB-)EVPN and how (PBB-)EVPN offers a more
more efficient implementation of these functions. efficient implementation of these functions. 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 Terminology
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].
2 E-Tree Scenarios and EVPN / PBB-EVPN Support 2 E-Tree Scenarios
In this section, we will categorize support for E-Tree into three This document categorizes E-Tree scenarios into the following three
different scenarios, depending on the nature of the site association scenarios, depending on the nature of the Root/Leaf site association:
(Root/Leaf) per PE or per Ethernet Segment:
- Leaf OR Root site(s) per PE - Leaf OR Root site(s) per PE
- Leaf OR Root site(s) per AC - Leaf OR Root site(s) per Attachment Circuit (AC)
- Leaf OR Root site(s) per MAC - Leaf OR Root site(s) per MAC
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 sites OR Leaf ACs for a given MAC-VRF/bridge table, but not both concurrently.
Leaf sites for a given MAC-VRF/bridge table, but not both In other words, a given EVI on a PE is either associated with root(s)
concurrently. In other words, a given EVI on a PE is either or leaf(s). The PE may have both Root and Leaf ACs albeit for
associated with root(s) or leaf(s). The PE may have both Root and different EVIs.
Leaf sites albeit for different EVIs.
+---------+ +---------+ +---------+ +---------+
| PE1 | | PE2 | | PE1 | | PE2 |
+---+ | +---+ | +------+ | +---+ | +---+ +---+ | +---+ | +------+ | +---+ | +---+
|CE1+---ES1----+--+ | | | MPLS | | | +--+----ES2-----+CE2| |CE1+---AC1----+--+ | | | MPLS | | | +--+----AC2-----+CE2|
+---+ (Root) | |MAC| | | /IP | | |MAC| | (Leaf) +---+ +---+ (Root) | |MAC| | | /IP | | |MAC| | (Leaf) +---+
| |VRF| | | | | |VRF| | | |VRF| | | | | |VRF| |
| | | | | | | | | | +---+ | | | | | | | | | | +---+
| | | | | | | | +--+----ES3-----+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 such scenario, using 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 restrict the communications among Leaf PEs. To restrict the
communications among Leaf sites connected to the same PE and communications among Leaf ACs connected to the same PE and belonging
belonging to the same EVI, split-horizon filtering is used to block to the same EVI, split-horizon filtering is used to block traffic
traffic from one Leaf interface to another Leaf interface of a given from one Leaf AC to another Leaf AC on a MAC-VRF for a given E-TREE
E-TREE EVI. The purpose of this topology constraint is to avoid EVI. The purpose of this topology constraint is to avoid having PEs
having PEs with only Leaf sites importing and processing BGP MAC with only Leaf sites importing and processing BGP MAC routes from
routes from each other. To support such topology constrain in EVPN, each other. To support such topology constrain in EVPN, two BGP
two BGP Route-Targets (RTs) are used for every EVPN Instance (EVI): Route-Targets (RTs) are used for every EVPN Instance (EVI): one RT is
one RT is associated with the Root sites and the other is associated associated with the Root sites (Root ACs) and the other is associated
with the Leaf sites. On a per EVI basis, every PE exports the single with the Leaf sites (Leaf ACs). On a per EVI basis, every PE exports
RT associated with its type of site(s). Furthermore, a PE with Root the single RT associated with its type of site(s). Furthermore, a PE
site(s) imports both Root and Leaf RTs, whereas a PE with Leaf with Root site(s) imports both Root and Leaf RTs, whereas a PE with
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 2.2 Scenario 2: Leaf OR Root site(s) per AC
In this scenario, a PE receives traffic from either Root OR Leaf In this scenario, a PE can receive traffic from both Root ACs and
sites (but not both) on a given Attachment Circuit (AC) of an EVI. In Leaf ACs for a given EVI. In other words, a given EVI on a PE can be
other words, an AC (ES or ES/VLAN) is either a Root AC or a Leaf AC associated with both root(s) and leaf(s).
(but not both).
+---------+ +---------+ +---------+ +---------+
| PE1 | | PE2 | | PE1 | | PE2 |
+---+ | +---+ | +------+ | +---+ | +---+ +---+ | +---+ | +------+ | +---+ | +---+
|CE1+-----ES1----+--+ | | | | | | +--+---ES2/AC1--+CE2| |CE1+-----AC1----+--+ | | | | | | +--+---AC2--+CE2|
+---+ (Leaf) | |MAC| | | MPLS | | |MAC| | (Leaf) +---+ +---+ (Leaf) | |MAC| | | MPLS | | |MAC| | (Leaf) +---+
| |VRF| | | /IP | | |VRF| | | |VRF| | | /IP | | |VRF| |
| | | | | | | | | | +---+ | | | | | | | | | | +---+
| | | | | | | | +--+---ES2/AC2--+CE3| | | | | | | | | +--+---AC3--+CE3|
| +---+ | +------+ | +---+ | (Root) +---+ | +---+ | +------+ | +---+ | (Root) +---+
+---------+ +---------+ +---------+ +---------+
Figure 2: Scenario 2 Figure 2: Scenario 2
In this scenario, just like the previous scenario (in section 2.1), In this scenario, just like the previous scenario (in section 2.1),
two Route Targets (one for Root and another for Leaf) can be used. two Route Targets (one for Root and another for Leaf) can be used.
However, the difference is that on a PE with both Root and Leaf ACs, However, the difference is that on a PE with both Root and Leaf ACs,
all remote MAC routes are imported and thus there needs to be a way all remote MAC routes are imported and thus there needs to be a way
to differentiate remote MAC routes associated with Leaf ACs versus to differentiate remote MAC routes associated with Leaf ACs versus
the ones associated with Root ACs in order to apply the proper the ones associated with Root ACs in order to apply the proper
ingress filtering. ingress filtering.
In order to support such ingress filtering on the ingress PE with In order to recognize the association of a destination MAC address to
both Leaf and Root ACs, one the following two approaches can be used: 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
Root or Leaf indication before advertisements to other PEs. There are
two approaches for such coloring:
A) To use two MAC-VRFs (two bridge tables per VLANs if a given VLAN A) To always use two RTs (one to designate Leaf RT and another for
exists on the PE for both Leaf and Root ACs of an EVI) - one for Root Root RT)
ACs and another for Leaf ACs.
B) To color MAC addresses with Leaf or Root color before distributing B) To allow for a single RT be used per EVI just like [RFC7432] and
them in BGP to other PEs depending on whether they are learned on a thus color MAC addresses via a "color" flag in a new extended
Leaf AC or a Root AC. community as detailed in section 3.1.
Maintaining two MAC-VRFs (two bridge tables) per VLAN (when both Leaf Approach (A) would require the same data plane enhancements as
and Root ACs exists for that VLAN) would either require two lookups approach (B) if MAC-VRF and bridge tables used per VLAN, are to
be performed per MAC address in each direction in case of a miss, or remain consistent with [RFC7432] (section 6). In order to avoid data-
duplicating many MAC addresses between the two bridge tables plane enhancements for approach (A), multiple bridge tables per VLAN
belonging to the same VLAN (same E-TREE instance). Unless two lookups may be considered; however, this has major drawbacks as described in
are made, duplication of MAC addresses would be needed for both appendix-A and thus is not recommended.
locally learned and remotely learned MAC addresses. Locally learned
MAC addresses from Leaf ACs need to be duplicated onto Root bridge
table and locally learned MAC addresses from Root ACs need to be
duplicated onto Leaf bridge table. Remotely learned MAC addresses
from Root ACs need to be copied onto both Root and Leaf bridge
tables. Because of potential inefficiencies associated with data-
plane implementation of additional MAC lookup or duplication of MAC
entries, option (A) is not believed to be implementable without
dataplane performance inefficiencies in some platforms and thus this
draft introduces the coloring option (B) as detailed in section 3.1.
For this scenario, if for a given EVI, the vast majority of PEs will Given that both approaches (A) and (B) would require exact same data-
have both Leaf and Root sites attached, even though they may start as plane enhancements, approach (B) is chosen here in order to allow for
Root-only or Leaf-only PEs, then a single RT per EVI MAY be used in RT usage consistent with baseline EVPN [RFC7432] and for better
order to alleviate the configuration overhead associated with using generality. It should be noted that if one wants to use RT constrain
two RTs per EVI at the expense of having unwanted MAC addresses on in order to avoid MAC advertisements associated with a Leaf AC to PEs
the Leaf-only PEs. 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
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
approach (B), the coloring is always done via the new extended
community.
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
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
overhead associated with using two RTs per EVI at the expense of
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
In this scenario, a PE may receive traffic from both Root AND Leaf In this scenario, a PE may receive traffic from both Root AND Leaf
sites on a single Attachment Circuit (AC) of an EVI. Since an sites on a single Attachment Circuit (AC) of an EVI. This scenario is
Attachment Circuit (ES or ES/VLAN) carries traffic from both Root and not covered in both [RFC7387] and [MEF6.1]; however, it is covered in
Leaf sites, the granularity at which Root or Leaf sites are this document for the sake of completeness. In this scenario, since
identified is on a per MAC address. This scenario is considered in an AC carries traffic from both Root and Leaf sites, the granularity
this draft for EVPN service with only known unicast traffic because at which Root or Leaf sites are identified is on a per MAC address.
the DF filtering per [RFC7432] would not be compatible with the This scenario is considered in this document for EVPN service with
required egress filtering - i.e., BUM traffic is not supported in only known unicast traffic because the Designated Forwarding (DF)
this scenario and it is dropped by the ingress PE. filtering per [RFC7432] would not be compatible with the required
egress filtering - i.e., Broadcast, Unknown, and Multicast (BUM)
traffic is not supported in this scenario and it is dropped by the
ingress PE.
+---------+ +---------+ +---------+ +---------+
| PE1 | | PE2 | | PE1 | | PE2 |
+---+ | +---+ | +------+ | +---+ | +---+ +---+ | +---+ | +------+ | +---+ | +---+
|CE1+-----ES1----+--+ | | | | | | +--+---ES2/AC1--+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 | | +---+
| | | | | | | | +--+---ES2/AC2--+CE3| | | | | | | | | +--+-----AC3----+CE3|
| +---+ | +------+ | +---+ | (Leaf) +---+ | +---+ | +------+ | +---+ | (Leaf) +---+
+---------+ +---------+ +---------+ +---------+
Figure 3: Scenario 3 Figure 3: Scenario 3
3 Operation for EVPN 3 Operation for EVPN
[RFC7432] defines the notion of ESI MPLS label used for split-horizon [RFC7432] defines the notion of Ethernet Segment Identifier (ESI)
filtering of BUM traffic at the egress PE. Such egress filtering MPLS label used for split-horizon filtering of BUM traffic at the
capabilities can be leveraged in provision of E-TREE services as seen egress PE. Such egress filtering capabilities can be leveraged in
shortly. In other words, [RFC7432] has inherent capability to support provision of E-TREE services as seen shortly. In other words,
E-TREE services without defining any new BGP routes but by just [RFC7432] has inherent capability to support E-TREE services without
defining a new BGP Extended Community for leaf indication as shown defining any new BGP routes but by just defining a new BGP Extended
later in this document. Community for leaf indication as shown later in this document
(section 5.1).
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). traditional E-TREE solutions (e.g., 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 by advertising a leaf indication flag
(via an Extended Community) along with each of its MAC/IP (via an Extended Community) along with each of its MAC/IP
Advertisement route. The lack of such flag indicates that the MAC Advertisement routes. The lack of such flag indicates that the MAC
address is associated with a root site. This scheme applies to all address is associated with a root site. This scheme applies to all
scenarios described in section 2. scenarios described in section 2.
Furthermore, for multi-homing scenario of section 2.2, where an AC is
either root or leaf (but not both), the PE MAY advertise leaf
indication along with the Ethernet A-D per EVI route. This
advertisement is used for sanity checking in control-plane to ensure
that there is no discrepancy in configuration among different PEs of
the same redundancy group. For example, if a leaf site is multi-homed
to PE1 an PE2, and PE1 advertises the Ethernet A-D per EVI
corresponding to this leaf site with the leaf-indication flag but PE2
does not, then the receiving PE notifies the operator of such
discrepancy and ignore the leaf-indication flag on PE1. In other
words, in case of discrepancy, the multi-homing for that pair of PEs
is assumed to be in default "root" mode for that <ESI, EVI> or <ESI,
EVI/VLAN>. The leaf indication flag on Ethernet A-D per EVI route
tells the receiving PEs that all MAC addresses associated with this
<ESI, EVI> or <ESI, EVI/VLAN> are from a leaf site. Therefore, if a
PE receives a leaf indication for an AC via the Ethernet A-D per EVI
route but doesn't receive a leaf indication in the corresponding
MAC/IP Advertisement route, then it notifies the operator and ignore
the leaf indication on the Ethernet A-D per EVI route.
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 take scenarios). In such situations, MAC mobility procedures (section 15
precedence to first identify the location of the MAC before of [RFC7432]) take precedence to first identify the location of the
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 5.2]. This new Extended Community MUST be advertised with MAC/IP
Advertisement route and MAY be advertised with an Ethernet A-D per Advertisement route. Besides MAC/IP Advertisement route, no other
EVI route as described above. EVPN routes are required to carry this new extended community.
3.2 BUM Traffic 3.2 BUM Traffic
This specification does not provide support for filtering BUM traffic This specification does not provide support for filtering BUM
on the ingress PE because it is not possible to perform filtering of (Broadcast, Unknown, and Multicast) traffic on the ingress PE because
BUM traffic on the ingress PE, as is the case with known unicast it is not possible to perform filtering of BUM traffic on the ingress
described above, due to the multi-destination nature of BUM traffic. PE, as is the case with known unicast described above, due to the
As such, the solution relies on egress filtering. In order to apply multi-destination nature of BUM traffic. As such, the solution relies
the proper egress filtering, which varies based on whether a packet on egress filtering. In order to apply the proper egress filtering,
is sent from a Leaf AC or a root AC, the MPLS-encapsulated frames which varies based on whether a packet is sent from a Leaf AC or a
MUST be tagged with an indication when they originated from a Leaf root AC, the MPLS-encapsulated frames MUST be tagged with an
AC. In other words, leaf indication for BUM traffic is done at the indication that they originated from a Leaf AC - i.e., to be tagged
granularity of AC. This can be achieved in EVPN through the use of a with a Leaf label as specified in section 5.1.
MPLS label where it can be used to either identify the Ethernet
segment of origin per [RFC7432] (i.e., ESI label) or it can be used
to indicate that the packet is originated from a leaf site (Leaf
label).
BUM traffic sent over a P2MP LSP or ingress replication, may need to
carry an upstream assigned or downstream assigned MPLS label
(respectively) for the purpose of egress filtering to indicate to the
egress PEs whether this packet is originated from a leaf AC.
The main difference between downstream and upstream assigned MPLS The Leaf label can be upstream assigned for P2MP LSP or downstream
label is that in case of downstream assigned not all egress PE assigned for ingress replication tunnels. The main difference between
devices need to receive the label just like ingress replication downstream and upstream assigned Leaf label is that in case of
procedures defined in [RFC7432]. downstream assigned not all egress PE devices need to receive the
label just like ESI label for ingress replication procedures defined
in [RFC7432].
The PE places all Leaf Ethernet Segments of a given bridge domain in On the ingress PE, the PE needs to place all its Leaf ACs for a given
a single split-horizon group in order to prevent intra-PE forwarding bridge domain in a single split-horizon group in order to prevent
among Leaf segments. This split-horizon function applies to BUM intra-PE forwarding among its Leaf ACs. This intra-PE split-horizon
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 (e.g., on a per MAC address basis) is
beyond the scope of this document. beyond the scope of this document.
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 special MPLS label indicating In this scenario, the ingress PE adds a Leaf label advertised using
a Leaf site. This special Leaf MPLS label, used for single-homing the E-Tree Extended Community (Section 5.1) indicating a Leaf site.
scenarios, is not on a per ES basis but rather on a per PE basis - This Leaf label, used for single-homing scenarios, is not on a per ES
i.e., a single Leaf MPLS label is used for all single-homed ES's on basis but rather on a per PE basis - i.e., a single Leaf MPLS label
that PE. This Leaf label is advertised to other PE devices, using a is used for all single-homed ES's on that PE. This Leaf label is
new EVPN Extended Community called E-TREE Extended Community (section advertised to other PE devices, using the E-TREE Extended Community
5.1) along with an Ethernet A-D per ES route with ESI of zero and a (section 5.1) along with an Ethernet A-D per ES route with ESI of
set of Route Targets (RTs) corresponding to all EVIs on the PE with zero and a set of Route Targets (RTs) corresponding to all EVIs on
at least one leaf site per EVI. The set of Ethernet A-D per ES routes the PE with at least one leaf site per EVI. The set of Ethernet A-D
may be needed if the number of Route Targets (RTs) that need to be per ES routes may be needed if the number of Route Targets (RTs) that
sent exceed the limit on a single route per [RFC7432]. The ESI for need to be sent exceed the limit on a single route per [RFC7432]. The
the Ethernet A-D per ES route is set to zero to indicate single-homed ESI for the Ethernet A-D per ES route is set to zero to indicate
sites. 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 AC (e.g., VLAN) does have the roots and some being leafs), the same VLAN does have the same
same root/leaf designation on all PEs on the same ES. Furthermore, it root/leaf designation on all PEs on the same ES. Furthermore, it is
is assumed that there is no forwarding among subnets - ie, the assumed that there is no forwarding among subnets - ie, the service
service is EVPN L2 and not EVPN IRB. IRB use case is outside the is EVPN L2 and not EVPN IRB [EVPN-IRB]. IRB use cases described in
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 such scenarios, 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.
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 Unicast from Root to Roots & Leaf - Ethernet known unicast from Root to Roots & Leaf
- Ethernet Unicast from Leaf to Root - Ethernet known unicast from Leaf to Root
- Ethernet Broadcast/Multicast from Root to Roots & Leafs - Ethernet BUM traffic from Root to Roots & Leafs
- Ethernet Broadcast/Multicast from Leaf to Roots - Ethernet 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 unicast flows need not be supported,
the L2VPN PEs can avoid performing any MAC learning function. the L2VPN PEs can avoid performing any MAC learning function.
In the subsections that follow, we will describe the operation of The following subsections will describe the operation of EVPN to
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 Advertisement routes. These routes will be imported by all EVPN MAC/IP Advertisement Routes. These routes will be imported by
PEs for that EVI (i.e., PEs that have Leaf sites as well as PEs that all PEs for that EVI (i.e., PEs that have Leaf sites as well as PEs
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 Advertisement routes. For the scenario reachability in EVPN MAC/IP Advertisement Routes. For the scenario
described in section 2.1 (or possibly section 2.2), these routes are described in section 2.1 (or possibly section 2.2), these 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) or ingress replication
can be used. The multicast tunnels are set up through the exchange of can be used (section 16 of [RFC7432]). The multicast tunnels are set
the EVPN Inclusive Multicast route, as defined in [RFC7432]. up through the exchange of the EVPN 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, ingress
replication should be sufficient for most scenarios where there are replication should be sufficient for most scenarios where there are
only a few Roots (typically two). Therefore, in a typical scenario, a only a few Roots (typically two). Therefore, in a typical scenario, a
root PE needs to support both a P2MP tunnel in transmit direction root PE needs to support both a P2MP tunnel in transmit direction
from itself to leaf PEs and at the same time it needs to support from itself to leaf PEs and at the same time it needs to support
ingress-replication tunnels in receive direction from leaf PEs to ingress-replication tunnels in receive direction from leaf PEs to
itself. In order to signal this efficiently from the root PE, a new itself. In order to signal this efficiently from the root PE, a new
composite tunnel type is defined per section 5.3. This new composite composite tunnel type is defined per section 5.2. This new composite
tunnel type is advertised by the root PE to simultaneously indicate a tunnel type is advertised by the root PE to simultaneously indicate a
P2MP tunnel in transmit direction and an ingress-replication tunnel P2MP tunnel in transmit direction and an ingress-replication tunnel
in the receive direction for the BUM traffic. in the receive direction for the BUM traffic.
If the number of Roots is large, P2MP tunnels originated at the PEs If the number of Roots is large, P2MP tunnels originated at the PEs
with Leaf sites may be used and thus there will be no need to use the with Leaf sites may be used and thus there will be no need to use the
modified PMSI tunnel attribute in section 5.2 for composite tunnel modified PMSI tunnel attribute in section 5.2 for composite tunnel
type. type.
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 only multicast when the traffic flows between Root and Leaf sites are mainly
or broadcast. In this case, the PEs do not exchange EVPN MAC multicast or broadcast. In this case, the PEs do not exchange EVPN
Advertisement routes. Instead, the Inclusive Multicast Ethernet Tag MAC/IP Advertisement Routes. Instead, the Inclusive Multicast
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 PEs with root sites
are only a few and thus ingress replication is desired from leaf PEs are only a few and thus ingress replication is desired from leaf PEs
to these root PEs, then the modified PMSI attribute as defined in to these root PEs, then the modified PMSI attribute as defined in
section 5.3 should be used. 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 MAC 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 and 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
skipping to change at page 14, line 26 skipping to change at page 14, line 9
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 C-MAC learning part of it at both ingress and
egress PEs. egress PEs.
5 BGP Encoding 5 BGP Encoding
This document defines two 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 having This Extended Community is a new transitive Extended Community
a Type field value of 0x06 (EVPN) and the Sub-Type 0x05. It is used [RFC4360] having a Type field value of 0x06 (EVPN) and the Sub-Type
for leaf indication of known unicast and BUM traffic. For BUM 0x05. It is used for leaf indication of known unicast and BUM
traffic, the Leaf Label field is set to a valid MPLS label and this traffic.
EC is advertised along with Ethernet A-D per ES route with an ESI of
zero to enable egress filtering on disposition PEs per section 3.2.1
and 3.2.3. There is no need to send ESI Label Extended Community when
sending Ethernet A-D per ES route with an ESI of zero. For known
unicast traffic, the Leaf flag bit is set to one and this EC is
advertised along with MAC/IP Advertisement route per section 3.1.
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
The low-order bit of the Flags octet is defined as the "Leaf- The low-order bit of the Flags octet is defined as the "Leaf-
Indication" bit. A value of one indicates a Leaf AC/Site. Indication" bit. A value of one indicates a Leaf AC/Site. The rest of
flag bits should be set to zero.
When this EC is advertised along with MAC/IP Advertisement route (for When this Extended Community (EC) is advertised along with MAC/IP
known unicast traffic), the Leaf-Indication flag MUST be set to one Advertisement route (for known unicast traffic) per section 3.1, the
and Leaf Label is set to zero. The received PE should ignore Leaf Leaf-Indication flag MUST be set to one and Leaf Label SHOULD be set
Label and only processes Leaf-Indication flag. A value of zero for to zero. The label value is encoded in the high-order 20 bits of the
Leaf-Indication flag is invalid when sent along with MAC/IP Leaf Label field. The received PE SHOULD ignore Leaf Label and only
advertisement route and an error should be logged. processes Leaf-Indication flag. A value of zero for Leaf-Indication
flag is invalid when sent along with MAC/IP 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, the Leaf Label MUST be set to a valid ESI of zero) for BUM traffic to enable egress filtering on
MPLS label and the Leaf-Indication flag should be set to zero. The disposition PEs per sections 3.2.1 and 3.2.3, the Leaf Label MUST be
received PE should ignore the Leaf-Indication flag. A non-valid MPLS 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
received 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
logged as an error. ignored and logged as an error.
The reserved bits should be set to zero by the transmitter and should
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 octets) |
+---------------------------------+ +---------------------------------+
| MPLS Label (3 octets) | | MPLS Label (3 octets) |
+---------------------------------+ +---------------------------------+
| Tunnel Identifier (variable) | | Tunnel Identifier (variable) |
+---------------------------------+ +---------------------------------+
This draft uses all the fields per existing definition except for the Figure 5: PMSI Tunnel Attribute
following modifications to the Tunnel Type and Tunnel Identifier:
This document defines a new Composite tunnel type by introducing a
new 'Composite Tunnel' bit in the Tunnel Type field and adding a MPLS
label to the Tunnel Identifier field of PMSI Tunnel attribute as
detailed below. This document uses all other remaining fields per
existing definition. 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.
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 (C bit - Composite tunnel bit) is set while of the tunnel type field (Composite Tunnel bit) is set while the
the remaining low-order seven bits indicate the tunnel type as remaining low-order seven bits indicate the tunnel type as before.
before. When this C bit is set, the "tunnel identifier" field would When this Composite Tunnel bit is set, the "tunnel identifier" field
begin with a three-octet label, followed by the actual tunnel would begin with a three-octet label, followed by the actual tunnel
identifier for the transmit tunnel. PEs that don't understand the identifier for the transmit tunnel. PEs that don't understand the
new meaning of the high-order bit would treat the tunnel type as an new meaning of the high-order bit would treat the tunnel type as an
invalid tunnel type. For the PEs that do understand the new meaning undefined tunnel type and would treat the PMSI tunnel attribute as a
of the high-order, if ingress replication is desired when sending BUM malformed attribute [RFC6514]. For the PEs that do understand the new
traffic, the PE will use the the label in the Tunnel Identifier field meaning of the high-order, if ingress replication is desired when
when sending its BUM traffic. sending BUM traffic, the PE will use the the label in the Tunnel
Identifier field when sending its BUM traffic.
Using the Composite flag for Tunnel Types 0x00 'no tunnel information Using the Composite Tunnel bit for Tunnel Types 0x00 'no tunnel
present' and 0x06 'Ingress Replication' is invalid, and should be information present' and 0x06 'Ingress Replication' is invalid, and a
treated as an invalid tunnel type on reception. PE that receives a PMSI Tunnel attribute with such information,
considers it as malformed and it SHOULD treat this Update as though
all the routes contained in this Update had been withdrawn per
section 5 of [RFC6514].
6 Acknowledgement 6 Acknowledgement
We would like to thank Dennis Cai, Antoni Przygienda, and Jeffrey We would like to thank Dennis Cai, Antoni Przygienda, and Jeffrey
Zhang for their valuable comments. The authors would also like to Zhang for their valuable comments. The authors would also like to
thank Thomas Morin for shepherding this document and providing thank Thomas Morin for shepherding this document and providing
valuable comments. valuable comments.
7 Security Considerations 7 Security Considerations
Since this draft uses the EVPN constructs of [RFC7432] and [RFC7623], Since this document uses the EVPN constructs of [RFC7432] and
the same security considerations in these drafts are also applicable [RFC7623], the same security considerations in these documents are
here. Furthermore, this draft provides additional security check by also applicable here. Furthermore, this document provides additional
allowing sites (or ACs) of an EVPN instance to be designated as security check by allowing sites (or ACs) of an EVPN instance to be
"Root" or "Leaf" and preventing any traffic exchange among "Leaf" designated as "Root" or "Leaf" and preventing any traffic exchange
sites of that VPN through ingress filtering for known unicast traffic among "Leaf" sites of that VPN through ingress filtering for known
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
skipping to change at page 17, line 4 skipping to change at page 16, line 39
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
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 to needs to be updated to reflect the use of the most significant bit as
advertise the use of "composite tunnels" (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:
- 0x7B-0x7E Reserved for Experimental Use [this document] Value Meaning Reference
- 0x7F Reserved [this document] 0x0B-0x7A Unassigned
- 0x80-0xFF Not Allocatable, corresponds to Composite tunnel types 0x7B-0x7E Reserved for Experimental Use this document
[this document] 0x7F Reserved this document
0x80-0xFF Reserved for Composite Tunnels this document
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 [RFC5226]. 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 [RFC5226].
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.
[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 [RFC7385] Andersson et al., "IANA Registry for P-Multicast Service
Service Interface (PMSI) Tunnel Type Code Points", Interface (PMSI) Tunnel Type Code Points", October, 2014.
October, 2014.
[RFC7153] Rosen et al., "IANA Registries for BGP Extended [RFC7153] Rosen et al., "IANA Registries for BGP Extended
Communities", March, 2014. Communities", March, 2014.
[RFC6514] Aggarwal et al., "BGP Encodings and Procedures [RFC6514] Aggarwal et al., "BGP Encodings and Procedures for
for Multicast in MPLS/BGP IP VPNs", February, 2012. Multicast in MPLS/BGP IP VPNs", February, 2012.
[RFC4360] Sangli et al., "BGP Extended Communities Attribute",
February, 2006.
9.2 Informative References 9.2 Informative References
[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
2", MEF 6.1, April 2008.
[RFC4360] S. Sangli et al, "BGP Extended Communities Attribute", [RFC4360] S. Sangli et al, "BGP Extended Communities Attribute",
February, 2006. February, 2006.
[RFC3032] E. Rosen et al, "MPLS Label Stack Encoding", January 2001.
[RFC7796] Y. Jiang et al, "Ethernet-Tree (E-Tree) Support in Virtual
Private LAN Service (VPLS)", March 2016.
[EVPN-IRB] A. Sajassi et al, "Integrated Routing and Bridging in
EVPN", draft-ietf-bess-evpn-inter-subnet-forwarding-03, February 8,
2017.
[RFC5226] T. Narten et al, "Guidelines for Writing an IANA
Considerations Section in RFCs", May, 2008.
Appendix-A
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
PE, then the following complications in data-plane path can result.
Maintaining two MAC-VRFs (two bridge tables) per VLAN (when both Leaf
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
duplicating many MAC addresses between the two bridge tables
belonging to the same VLAN (same E-TREE instance). Unless two lookups
are made, duplication of MAC addresses would be needed for both
locally learned and remotely learned MAC addresses. Locally learned
MAC addresses from Leaf ACs need to be duplicated onto Root bridge
table and locally learned MAC addresses from Root ACs need to be
duplicated onto Leaf bridge table. Remotely learned MAC addresses
from Root ACs need to be copied onto both Root and Leaf bridge
tables. Because of potential inefficiencies associated with data-
plane implementation of additional MAC lookup or duplication of MAC
entries, this option is not believed to be implementable without
dataplane performance inefficiencies in some platforms and thus this
document introduces the coloring as described in section 2.2 and
detailed in section 3.1.
Contributors Contributors
In addition to the authors listed on the front page, the following In addition to the authors listed on the front page, the following
co-authors have also contributed to this document: co-authors have also contributed to this document:
Wim Henderickx Wim Henderickx
Nokia Nokia
Aldrin Isaac Aldrin Isaac
Wen Lin Wen Lin
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