wdiff draft-ietf-l2vpn-evpn-00.txt draft-ietf-l2vpn-evpn-01.txt

Network Working Group R. Aggarwal A. Sajassi
INTERNET-DRAFT Arktan Cisco
Category: Standards Track
Expires: August 25, 2012 A. Sajassi
Cisco

J. Uttaro W. Henderickx
AT&T Alcatel-Lucent

A. Isaac
R. Aggarwal
N. Bitar
Bloomberg Arktan
Verizon
W. Henderickx
S. Boutros F. Balus R. Shekhar
K. Patel Alcatel-Lucent
S. Salam
Cisco Aldrin Isaac
Bloomberg
J. Drake
R. Shekhar J. Uttaro
Juniper Networks
S. Boutros
K. Patel
Cisco February 24, AT&T

Expires: January 14, 2012 July 14, 2012

BGP MPLS Based Ethernet VPN
draft-ietf-l2vpn-evpn-00
draft-ietf-l2vpn-evpn-01

Status of this Memo

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

Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as
Internet-Drafts.

Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."

The list of current Internet-Drafts can be accessed at
http://www.ietf.org/1id-abstracts.html

The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.

Abstract

This document describes procedures for BGP MPLS based Ethernet VPNs
(E-VPN).

Table of Contents

1. Specification of requirements . . . . . . . . . . . . . . . . . 4 5
2. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 4 5
3. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 5
4. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5
5. BGP MPLS Based E-VPN Overview . . . . . . . . . . . . . . . . . 4 6
6. Ethernet Segment Identifier . . . . . . . . . . . . . . . . . . 6 . . . . . 7
7. Ethernet Tag . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1 VLAN Based Service Interface . . . . . . . . . . . . . . . . 9
7.2 VLAN Bundle Service Interface . . . . . . . . . . . . . . . 9
7.2.1 Port Based Service Interface . . . . . . . . . . . . . . 9
7.3 VLAN Aware Bundle Service Interface . . . . . . . . . . . . 9
8. BGP E-VPN NLRI . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. 10
8.1. Ethernet Auto-Discovery Route . . . . . . . . . . . . . . . 8
7.2. 10
8.2. MAC Advertisement Route . . . . . . . . . . . . . . . . . 8
7.3. 11
8.3. Inclusive Multicast Ethernet Tag Route . . . . . . . . . . 9
8. 11
8.4 Ethernet Segment Route . . . . . . . . . . . . . . . . . . . 12
8.5 ESI MPLS Label Extended Community . . . . . . . . . . . . . 12
8.6 ES-Import Extended Community . . . . 9
9. Auto-Discovery . . . . . . . . . . . . 13
8.7 MAC Mobility Extended Community . . . . . . . . . . . . 9
10. Auto-Discovery of Ethernet Tags on . . 13
9. Multi-homing Functions . . . . . . . . . . . . . . . . . . . . 13
9.1 Multi-homed Ethernet Segments Segment Auto-Discovery . . . . . 10
10.1. . . . 13
9.1.1 Constructing the Ethernet A-D Segment Route . . . . . . . . 14
9.2 Fast Convergence . . . 10
10.1.1. . . . . . . . . . . . . . . . . . . . 14
9.2.1 Constructing the Ethernet A-D Route per E-VPN Ethernet
Segment . . . . . . . . . . . . . 11
10.1.1.1. . . . . . . . . . . . 15
9.2.1.1. Ethernet A-D Route Targets . . . . . . . . . . . . 12
10.1.2. Ethernet A-D Route per Ethernet Segment 15
9.3 Split Horizon . . . . . . . 12
10.1.2.1. Ethernet A-D Route Targets . . . . . . . . . . . . 13
10.2. Motivations for Ethernet A-D Route per Ethernet Segment . 13
10.2.1. Multi-Homing . . . 16
9.3.1 ESI MPLS Label Assignment . . . . . . . . . . . . . . . 16
9.3.1.1 Ingress Replication . . . 14
10.2.2. Optimizing Control Plane Convergence . . . . . . . . . 14
10.2.3. Reducing Number of Ethernet A-D Routes . . . . 16
9.3.1.2. P2MP MPLS LSPs . . . . . . . 14
11. Determining Reachability to Unicast MAC Addresses . . . . . . 14
11.1. Local Learning . . . . . 17
9.3.1.3. MP2MP LSPs . . . . . . . . . . . . . . . . . 15
11.2. Remote learning . . . 18

9.4 Aliasing . . . . . . . . . . . . . . . . . . . 15
11.2.1. Constructing the BGP E-VPN MAC Address Advertisement . 15
12. Optimizing ARP . . . . . . 18
9.4.1 Constructing the Ethernet A-D Route per EVI . . . . . . 18
9.4.1.1 Ethernet A-D Route Targets . . . . . . . . . . . . . 17
13. 19
9.5 Designated Forwarder Election . . . . . . . . . . . . . . . . 18
13.1. 20
9.5.1 Default DF Election Performed by All MESes Procedure . . . . . . . . . . . . 19
13.2. . 21
9.5.2 DF Election Performed Only on Multi-Homed MESes with Service Carving . . . . . . 20
14. Handling of Multi-Destination Traffic . . . . . . 21
10. Determining Reachability to Unicast MAC Addresses . . . . . . 22
10.1. Local Learning . 21
14.1. Construction of the Inclusive Multicast Ethernet Tag
Route . . . . . . . . . . . . . . . . . . . . . 23
10.2. Remote learning . . . . . 21
14.2. P-Tunnel Identification . . . . . . . . . . . . . . . . 23
10.2.1. Constructing the BGP E-VPN MAC Address Advertisement . 22
14.3. Ethernet Segment Identifier 23
11. ARP and Ethernet Tag ND . . . . . . . 22
15. Processing of Unknown Unicast Packets . . . . . . . . . . . . 23
15.1. Ingress Replication . . . . . . . 25
12. Handling of Multi-Destination Traffic . . . . . . . . . . . . 24
15.2. P2MP MPLS LSPs 26
12.1. Construction of the Inclusive Multicast Ethernet Tag
Route . . . . . . . . . . . . . . . . . . . . . . 24
16. Forwarding Unicast Packets . . . . 26
12.2. P-Tunnel Identification . . . . . . . . . . . . . . 24
16.1. Forwarding packets received from a CE . . . 27
13. Processing of Unknown Unicast Packets . . . . . . . 24
16.2. Forwarding packets received from a remote MES . . . . . 28
13.1. Ingress Replication . 25
16.2.1. Unknown Unicast Forwarding . . . . . . . . . . . . . . 25
16.2.2. Known Unicast Forwarding . . . . 28
13.2. P2MP MPLS LSPs . . . . . . . . . . . 26
17. Split Horizon . . . . . . . . . . . 29
14. Forwarding Unicast Packets . . . . . . . . . . . . . 26
17.1. ESI MPLS Label: Ingress Replication . . . . . 29
14.1. Forwarding packets received from a CE . . . . . . 26
17.2. ESI MPLS Label: P2MP MPLS LSPs . . . . 29
14.2. Forwarding packets received from a remote PE . . . . . . . 30
14.2.1. Unknown Unicast Forwarding . . . 27
17.3. ESI MPLS Label: MP2MP LSPs . . . . . . . . . . . 30
14.2.2. Known Unicast Forwarding . . . . . 28
18. . . . . . . . . . . 31
15. Load Balancing of Unicast Packets Frames . . . . . . . . . . . . . . 28
18.1. . 31
15.1. Load balancing of traffic from an MES PE to remote CEs . . . 28
18.2. . 31
15.1.1 Active-Standby Redundancy Mode . . . . . . . . . . . . 31
15.1.2 All-Active Redundancy Mode . . . . . . . . . . . . . . 32
15.2. Load balancing of traffic between an MES PE and a local CE . 30
18.2.1. . 33
15.2.1. Data plane learning . . . . . . . . . . . . . . . . . 31
18.2.2. 34
15.2.2. Control plane learning . . . . . . . . . . . . . . . . 31
19. 34
16. MAC Moves . Mobility . . . . . . . . . . . . . . . . . . . . . . . . . 31
20. 34
17. Multicast . . . . . . . . . . . . . . . . . . . . . . . . . . 32
20.1. 36
17.1. Ingress Replication . . . . . . . . . . . . . . . . . . . 32
20.2. 36
17.2. P2MP LSPs . . . . . . . . . . . . . . . . . . . . . . . . 32
20.3. 36
17.3. MP2MP LSPs . . . . . . . . . . . . . . . . . . . . . . . . 32
20.3.1. 36
17.3.1. Inclusive Trees . . . . . . . . . . . . . . . . . . . 33
20.3.2. 36
17.3.2. Selective Trees . . . . . . . . . . . . . . . . . . . 33
20.4. 37
17.4. Explicit Tracking . . . . . . . . . . . . . . . . . . . . 34
21. 38
18. Convergence . . . . . . . . . . . . . . . . . . . . . . . . . 34
21.1. 38
18.1. Transit Link and Node Failures between MESes PEs . . . . . . . 34
21.2. MES . 38
18.2. PE Failures . . . . . . . . . . . . . . . . . . . . . . . 34
21.2.1. 38
18.2.1. Local Repair . . . . . . . . . . . . . . . . . . . . . 35
21.3. MES 38
18.3. PE to CE Network Failures . . . . . . . . . . . . . . . . 35
22. 39
19. LACP State Synchronization . . . . . . . . . . . . . . . . . . 35
23. 39
20. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 36
24. 40
21. References . . . . . . . . . . . . . . . . . . . . . . . . . . 37
25. 40
21. Author's Address . . . . . . . . . . . . . . . . . . . . . . . 37 41

1. Specification of requirements

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].

2. Contributors

In addition to the authors listed above, the following individuals
also contributed to this document:

Quaizar Vohra
Kireeti Kompella
Apurva Mehta
Nadeem Mohammad
Juniper Networks

Samer Salam

Clarence Filsfils
Dennis Cai
Cisco

3. Introduction

This document describes procedures for BGP MPLS based Ethernet VPNs
(E-VPN). The procedures described here are intended to meet the
requirements specified in [E-VPN-REQ]. Please refer to [E-VPN-REQ]
for the detailed requirements and motivation.

This document proposes an MPLS based technology, referred to as MPLS-
based E-VPN (E-VPN). E-VPN requires
extensions to existing IP/MPLS protocols as described in this
document. In addition to these extensions E-VPN uses several building
blocks from existing MPLS technologies.

4. Terminology

CE: Customer Edge device e.g., host or router or switch
MES: MPLS Edge Switch
EVI:

E-VPN Instance
ESI: (EVI): An E-VPN routing and forwarding instance on a
PE.

Ethernet segment identifier
LACP: (ESI): If a CE is multi-homed to two or
more PEs, the set of Ethernet links that attaches the CE to the PEs
is an 'Ethernet segment'. Ethernet segments MUST have a unique non-
zero identifier, the 'Ethernet Segment Identifier'.

Ethernet Tag: An Ethernet Tag identifies a particular broadcast
domain, e.g., a VLAN. An E-VPN instance consists of one or more
broadcast domains. Ethernet tag(s) are assigned to the broadcast
domains of a given E-VPN instance by the provider of that E-VPN, and
each PE in that E-VPN instance performs a mapping between broadcast
domain identifier(s) understood by each of its attached CEs and the
corresponding Ethernet tag.

Link Aggregation Control Protocol
MP2MP: (LACP):

Multipoint to Multipoint
P2MP: (MP2MP):

Point to Multipoint
P2P: (P2MP):

Point to Point (P2P):

5. BGP MPLS Based E-VPN Overview

This section provides an overview of E-VPN.

An E-VPN comprises CEs that are connected to PEs, or MPLS Edge
Switches (MES), PEs that form the edge
of the MPLS infrastructure. A CE may be a host, a router or a switch.
The MPLS Edge Switches PEs provide
layer 2 virtual bridge Layer 2 bridged connectivity between the CEs.
There may be multiple E-VPNs in the provider's network. An E-VPN routing and
forwarding instance on an MES is referred to as an E-VPN Instance
(EVI).

The MESes maybe PEs may be connected by an MPLS LSP infrastructure which provides
the benefits of MPLS LSP technology such as fast-reroute, resiliency,
etc. The MESes PEs may also be connected by an IP infrastructure in which
case IP/GRE tunneling is or other IP tunneling can be used between the
MESes.
PEs. The detailed procedures in this version of this document are
specified only for MPLS LSPs as the tunneling technology. However
these procedures are designed to be extensible to IP/GRE IP tunneling as the
PSN tunneling technology.

In an E-VPN, MAC learning between MESes PEs occurs not in the data plane
(as happens with traditional bridging) but in the control plane.
Control plane learning offers greater control over the MAC learning
process, such as restricting who learns what, and the ability to
apply policies. Furthermore, the control plane chosen for
advertising MAC reachability information is multi-protocol (MP) BGP
(very similar
(similar to IP VPNs (RFC 4364)), providing 4364)). This provides greater scale, scalability
and the ability to preserve the "virtualization" or isolation of
groups of interacting agents (hosts, servers, Virtual Machines) virtual machines) from
each other. In E-VPNs MESes E-VPN, PEs advertise the MAC addresses learned from
the CEs that are connected to them, along with an MPLS label, to
other
MESes PEs in the control plane using MP-BGP. Control plane learning
enables load balancing of traffic to and from CEs that are multi-
homed to multiple MESes. PEs. This is in addition to load balancing across
the MPLS core via multiple LSPs betwen between the same pair of MESes. PEs. In
other words it allows CEs to connect to multiple active points of
attachment. It also improves convergence times in the event of
certain network failures.

However, learning between MESes PEs and CEs is done by the method best
suited to the CE: data plane learning, IEEE 802.1x, LLDP, 802.1aq,
ARP, management plane or other protocols.

It is a local decision as to whether the Layer 2 forwarding table on
a MES
an PE is populated with all the MAC destinations destination addresses known to
the control
plane plane, or whether the MES PE implements a cache based scheme.
For instance the MAC forwarding table may be populated only with the
MAC destinations of the active flows transiting a specific MES. PE.

The policy attributes of an E-VPN are very similar to those of an IP
VPN. IP-VPN.
An E-VPN instance EVI requires a Route-Distinguisher (RD) and an E-
VPN requires one or more Route-Targets Route-
Targets (RTs). A CE attaches to an E-
VPN E-VPN instance (EVI) on an MES, PE, on
an Ethernet interface which may be configured for one or more
Ethernet Tags, e.g., VLANs. Some deployment scenarios guarantee
uniqueness of VLANs across E-VPNs: all points of attachment of a
given E-VPN EVI use the same VLAN, and no other
E-VPN EVI uses this VLAN. This
document refers to this case as a "Unique
Single VLAN E-VPN" and describes
simplified procedures to optimize for it.

6. Ethernet Segment Identifier

If a CE is multi-homed to two or more MESes, PEs, the set of Ethernet links
constitutes an "Ethernet segment". Segment". An Ethernet segment may appear to
the CE as a Link Aggregation Group (LAG). Ethernet segments have an
identifier, called the "Ethernet Segment Identifier" (ESI) which is
encoded as a ten octets integer. A single-homed CE is considered to
be attached to an Ethernet segment with ESI 0. Otherwise, an Ethernet
segment MUST have a unique non-zero ESI. The ESI can be assigned
using various mechanisms:
1. The ESI may be configured. For instance when E-VPNs are used to
provide a VPLS service the ESI is fairly analogous to the Multi-
homing site ID in [BGP-VPLS-MH].

2. If IEEE 802.1AX LACP is used, used between the MESes PEs and CEs, then
the ESI is determined from LACP by concatenating the following
parameters:

+ CE LACP System Identifier comprised of two bytes octets of System
Priority and six bytes octets of System MAC address, where the
System Priority is encoded in the most significant two bytes. octets.
The CE LACP identifier MUST be encoded in the high order eight bytes
octets of the ESI.

+ CE LACP two byte octets Port Key. The CE LACP port key MUST be
encoded in the low order two bytes octets of the ESI ESI.

As far as the CE is concerned concerned, it would treat the multiple MESes PEs
that it is connected to as the same switch. This allows the CE
to aggregate links that are attached to different MESes PEs in the
same bundle.

3. If LLDP is used, used between the MESes PEs and CEs that are hosts, then
the ESI is determined by LLDP. The ESI will be specified in a
following version.

4. In the case of indirectly connected hosts via a bridged LAN
between the CEs and the MESes, PEs, the ESI is determined based on the
Layer 2 bridge protocol as follows: If STP MST is used in the bridged
LAN then the value of the ESI is derived by listening to BPDUs on
the Ethernet segment. To achieve this the MES PE is not required to
run STP. MST. However the MES PE must learn the Switch ID, MSTP ID and Root Bridge ID MAC address
and Bridge Priority of the root of the Internal Spanning Tree
(IST) by listening to STP the BPDUs. The ESI is constructed as
follows:

{Switch ID (6 bits), MSTP ID (6 bits),

{Bridge Priority (16 bits) , Root Bridge ID MAC Address (48 bits)}

7. Ethernet Tag

An Ethernet Tag identifies a particular broadcast domain, e.g. a
VLAN, in an EVI. An EVI consists of one or more broadcast domains.
Ethernet Tags are assigned to the broadcast domains of a given EVI by
the provider of the E-VPN service. Each PE, in a given EVI, performs
a mapping between the Ethernet Tag and the corresponding broadcast
domain identifier(s) understood by each of its attached CEs (e.g. CE
VLAN Identifiers or CE-VIDs).

If the broadcast domain identifiers(s) are understood consistently by
all of the CEs in an EVI, the broadcast domain identifier(s) MAY be
used as the corresponding Ethernet Tag(s). In other words, the
Ethernet Tag ID assigned by the provider is numerically equal to the
broadcast domain identifier (e.g., CE-VID = Ethernet Tag).

Further, some deployment scenarios guarantee uniqueness of broadcast
domain identifiers across all EVIs; all points of attachment of a
given EVI use the same broadcast domain identifier(s) and no other
EVI uses these broadcast domain identifier(s). This allows the RT(s)
for each EVI to be derived automatically, as described in section
9.4.1.1.1 "Auto-Derivation from the Ethernet Tag ID".

The following subsections discuss the relationship between Ethernet
Tags, EVIs and broadcast domain identifiers as well as the setting of
the Ethernet Tag Identifier, in the various E-VPN BGP routes (defined
in section 8), for the different types of service interfaces
described in [EVPN-REQ].

7.1 VLAN Based Service Interface

With this service interface, there is a one-to-one mapping between
the broadcast domain identifier understood by a CE on a port (e.g.
CE-VID) and an EVI. Furthermore, there is a single bridge domain per
PE for the EVI. Different CEs connected to different PE ports MAY use
different broadcast domain identifiers (e.g. CE-VIDs) for the same
EVI. If said identifiers are different, the frames SHOULD remain
tagged with the originating CE's broadcast domain identifier (e.g.
CE-VID). When the CE broadcast domain identifiers are not consistent,
a tag translation function MUST be supported in the data path and
MUST be performed on the disposition PE. The Ethernet Tag Identifier
in all E-VPN routes MUST be set to 0.

7.2 VLAN Bundle Service Interface

With this service interface, there is a many-to-one mapping between
the broadcast domain identifier understood by a CE on a port (e.g.
CE-VID) and an EVI. Furthermore, there is a single bridge domain per
PE for the EVI. Different CEs connected to different PE ports MUST
use the same broadcast domain identifiers (e.g. CE-VIDs) for the same
EVI. The MPLS encapsulated frames MUST remain tagged with the
originating CE's broadcast domain identifier (e.g. CE-VID). Tag
translation is NOT permitted. The Ethernet Tag Identifier in all E-
VPN routes MUST be set to 0.

7.2.1 Port Based Service Interface

This service interface is a special case of the VLAN Bundle service
interface, where all of the VLANs on the port are part of the same
service and map to the same bundle. The procedures are identical to
those described in section 7.2.

7.3 VLAN Aware Bundle Service Interface

With this service interface, there is a many-to-one mapping between
the broadcast domain identifier understood by a CE on a port (e.g.
CE-VID) and an EVI. Furthermore, there are multiple bridge domains
per PE for the EVI: one broadcast domain per CE broadcast domain
identifier. In the case where the CE broadcast domain identifiers are
not consistent for different CEs, a normalized Ethernet Tag MUST be
carried in the MPLS encapsulated frames and a tag translation
function MUST be supported in the data path. This translation MUST be
performed on both the imposition as well as the disposition PEs. The
Ethernet Tag Identifier in all E-VPN routes MUST be set to the
normalized Ethernet Tag assigned by the E-VPN provider.

8. BGP E-VPN NLRI

This document defines a new BGP NLRI, called the E-VPN NLRI.

Following is the format of the E-VPN NLRI:

+-----------------------------------+
| Route Type (1 octet) |
+-----------------------------------+
| Length (1 octet) |
+-----------------------------------+
| Route Type specific (variable) |
+-----------------------------------+

The Route Type field defines encoding of the rest of the E-VPN NLRI
(Route Type specific E-VPN NLRI).

The Length field indicates the length in octets of the Route Type
specific field of E-VPN NLRI.

This document defines the following Route Types:

+ 1 - Ethernet Auto-Discovery (A-D) route
+ 2 - MAC advertisement route
+ 3 - Inclusive Multicast Route
+ 5 - Selective Multicast Auto-Discovery (A-D) Route
+ 6 4 - Leaf Auto-Discovery (A-D) Ethernet Segment Route

The detailed encoding and procedures for these route types are
described in subsequent sections.

The E-VPN NLRI is carried in BGP [RFC4271] using BGP Multiprotocol
Extensions [RFC4760] with an AFI of TBD and an SAFI of E-VPN (To be
assigned by IANA). The NLRI field in the
MP_REACH_NLRI/MP_UNREACH_NLRI attribute contains the E-VPN NLRI
(encoded as specified above).

In order for two BGP speakers to exchange labeled E-VPN NLRI, they
must use BGP Capabilities Advertisement to ensure that they both are
capable of properly processing such NLRI. This is done as specified
in [RFC4760], by using capability code 1 (multiprotocol BGP) with an
AFI of TBD and an SAFI of E-VPN.

7.1.

8.1. Ethernet Auto-Discovery Route

A Ethernet A-D route type specific E-VPN NLRI consists of the
following:

For procedures and usage of this route please see the sections on
"Auto-Discovery of Ethernet Tags on Ethernet Segments", "Designated
Forwarder Election" section 9.2 "Fast
Convergence" and "Load Balancing".

7.2. section 9.4 "Aliasing".

8.2. MAC Advertisement Route

A MAC advertisement route type specific E-VPN NLRI consists of the
following:

+---------------------------------------+
| RD (8 octets) |
+---------------------------------------+
|Ethernet Segment Identifier (10 octets)|
+---------------------------------------+
| Ethernet Tag ID (4 octets) |
+---------------------------------------+
| MAC Address Length (1 octet) |
+---------------------------------------+
| MAC Address (6 octets) |
+---------------------------------------+
| IP Address Length (1 octet) |
+---------------------------------------+
| IP Address (4 or 16 octets) |
+---------------------------------------+
| MPLS Label (n * 3 octets) |
+---------------------------------------+

For procedures and usage of this route please see the sections on section 10
"Determining Reachability to Unicast MAC Addresses" and section 15
"Load Balancing of Unicast Packets".

7.3.

8.3. Inclusive Multicast Ethernet Tag Route

An Inclusive Multicast Ethernet Tag route type specific E-VPN NLRI
consists of the following:

For procedures and usage of this route please see the sections on section 12
"Handling of Multi-Destination Traffic", "Unknown section 13 "Processing of
Unknown Unicast Traffic" and section 17 "Multicast".

8.4 Ethernet Segment Route

The Ethernet Segment Route is encoded in the E-VPN NLRI using the
Route Type value of 4. The Route Type Specific field of the NLRI is
formatted as follows:

+---------------------------------------+
| RD (8 octets) |
+---------------------------------------+
|Ethernet Segment Identifier (10 octets)|
+---------------------------------------+

For procedures and usage of this route please see section 9.5
"Designated Forwarder Election".

8.5 ESI MPLS Label Extended Community

This extended community is a new transitive extended community. It
may be advertised along with Ethernet Auto-Discovery routes. When
used it carries properties associated with the ESI. Specifically routes and it
enables split horizon split-horizon procedures for multi-homed sites. The
procedures for using this Extended Community are sites as described
in
following sections. section 9.3 "Split Horizon".

Each ESI MPLS Label Extended Community is encoded as a 8-octet value
as follows:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x44 | Sub-Type | Flags (One Octet) |Reserved=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved = 0| ESI MPLS label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The low order bit of the flags octet is defined as the "Active-
Standby" bit and may be set to 1. The other bits must be set to 0.

9. Auto-Discovery

E-VPN requires

8.6 ES-Import Extended Community

This is a new transitive extended community carried with the following types of auto-discovery procedures:
+ E-VPN Auto-Discovery, which allows an MES Ethernet
Segment route. When used, it enables all the PEs connected to discover the other
MESes
same multi-homed site to import the Ethernet Segment routes. The
value is derived automatically from the ESI by encoding the 6-byte
MAC address portion of the ESI in the E-VPN. Each MES advertises one or more "Inclusive
Multicast Tag Routes". ES-Import Extended Community.
The format of this extended community is as follows:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x44 | Sub-Type | ES-Import |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ES-Import Cont'd |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

For procedures and usage of this attribute, please see section 9.1
"Redundancy Group Discovery".

8.7 MAC Mobility Extended Community

This extended community is a new transitive extended community. It
may be advertised along with MAC Advertisement routes. The procedures
for advertising these
routes using this Extended Community are described in the section on "Handling of Multi-
Destination Traffic".

+ 16 "MAC
Mobility".

The MAC Mobility Extended Community is encoded as a 8-octet value as
follows:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x44 | Sub-Type | Reserved=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

9. Multi-homing Functions

This section discusses the functions, procedures and associated BGP
routes used to support multi-homing in E-VPN. This covers both multi-
homed device (MHD) as well as multi-homed network (MHN) scenarios.

9.1 Multi-homed Ethernet Segment Auto-Discovery

PEs connected to the same Ethernet segment can automatically discover
each other with minimal to no configuration through the exchange of
the Ethernet Tags on Segment route.

9.1.1 Constructing the Ethernet Segments, in Segment Route

The Route-Distinguisher (RD) MUST be a
particular E-VPN. Type 1 RD [RFC4364]. The procedures are value
field comprises an IP address of the MES (typically, the loopback
address) followed by 0's.

The Ethernet Segment Identifier MUST be set to the ten octet ESI
identifier described in section
"Auto-Discovery of 6.

The BGP advertisement that advertises the Ethernet Tags on Segment route MUST
also carry an ES-Import extended community attribute, as defined in
section 8.6.

The Ethernet Segments".

+ Segment Route filtering MUST be done such that the
Ethernet Segment Auto-Discovery used for auto-discovery of MESes Route is imported only by the PEs that are multi-homed multi-
homed to the same Ethernet segment. Segment. To that end, each PE that is
connected to a particular Ethernet segment constructs an import
filtering rule to import a route that carries the ES-Import extended
community, constructed from the ESI.

Note that the new ES-Import extended community is not the same as the
Route Target Extended Community. The
procedures are described in section "Auto-Discovery of Ethernet
Tags Segment route carries
this new ES-Import extended community. The PEs apply filtering on
this new extended community. As a result the Ethernet Segments".

10. Auto-Discovery of Ethernet Tags on Segment route
is imported only by the PEs that are connected to the same Ethernet Segments

If a CE
segment.

9.2 Fast Convergence

In E-VPN, MAC address reachability is multi-homed learnt via the BGP control-
plane over the MPLS network. As such, in the absence of any fast
protection mechanism, the network convergence time is a function of
the number of MAC Advertisement routes that must be withdrawn by the
PE encountering a failure. For highly scaled environments, this
scheme yields slow convergence.

To alleviate this, E-VPN defines a mechanism to two or more MESes on efficiently and
quickly signal, to remote PE nodes, the need to update their
forwarding tables upon the occurrence of a particular failure in connectivity to
an Ethernet
segment, segment. This is done by having each MES MUST advertise, PE advertise an
Ethernet A-D Route per Ethernet segment for each locally attached
segment (refer to other MESes section 9.2.1 below for details on how this route
is constructed). Upon a failure in connectivity to the E-VPN, attached
segment, the
information about PE withdraws the corresponding Ethernet Tags A-D route. This
triggers all PEs that are receive the withdrawal to update their next-hop
adjacencies for all MAC addresses associated with that the Ethernet
segment in question. If no other PE had advertised an Ethernet A-D
route for the same segment, then the PE that received the withdrawal
simply invalidates the MAC entries for that segment. An Otherwise, the
PE updates the next-hop adjacencies to point to the backup PE(s).

9.2.1 Constructing the Ethernet Tag identifies A-D Route per Ethernet Segment

This section describes procedures to construct the Ethernet A-D route
when a particular broadcast
domain. An example single such route is advertised by an PE for a given Ethernet
Segment. This flavor of the Ethernet A-D route is used for fast
convergence (as discussed above) as well as for advertising the ESI
MPLS label used for split-horizon filtering (as discussed in section
9.2). Support of this route flavor is MANDATORY.

Route-Distinguisher (RD) MUST be a Type 1 RD [RFC4364]. The value
field comprises an IP address of the PE (typically, the loopback
address) followed by 0. The reason for such encoding is that the RD
cannot be that of a given EVI since the ESI can span across one or
more EVIs.

The Ethernet Segment Identifier MUST be a ten octet entity as
described in section "Ethernet Segment". This document does not
specify the use of the Ethernet A-D route when the Segment Identifier
is set to 0.

The Ethernet Tag ID MUST be set to 0.

The MPLS label in the NLRI MUST be set to 0.

The "ESI MPLS Label Extended Community" MUST be included in the
route. If all-active multi-homing is desired, then the "Active-
Standby" bit in the flags of the ESI MPLS Label Extended Community
MUST be set to 0 and the MPLS label in that extended community MUST
be set to a VLAN ID. valid MPLS label value. The MES MAY
advertise each MPLS label in this Extended
Community is referred to as an "ESI label". This label MUST be a
downstream assigned MPLS label if the advertising PE is using ingress
replication for receiving multicast, broadcast or unknown unicast
traffic from other PEs. If the advertising PE is using P2MP MPLS LSPs
for sending multicast, broadcast or unknown unicast traffic, then
this label MUST be an upstream assigned MPLS label. The usage of this
label is described in section 9.2.

If the Ethernet Tag Segment is connected to more than one PE and active-
standby multi-homing is desired, then the "Active-Standby" bit in the
flags of the ESI MPLS Label Extended Community MUST be set to 1.

9.2.1.1. Ethernet A-D Route Targets
The Ethernet A-D route MUST carry one or more Route Target (RT)
attributes. These RTs MUST be the set of RTs associated with all the
EVIs to which the Ethernet Segment, or
it may advertise a wildcard corresponding to cover all the Ethernet Tags enabled on
the segment. If A-D
route, belongs.

9.3 Split Horizon

Consider a CE that is single-homed, multi-homed to two or more PEs on an Ethernet
segment ES1. If the CE sends a multicast, broadcast or unknown
unicast packet to a particular PE, say PE1, then PE1 will forward
that packet to all or subset of the MES other PEs in the EVI. In this
case the PEs, other than PE1, that it the CE is
attached multi-homed to MAY advertise MUST drop
the information about Ethernet Tags
(e.g.,VLANs) on packet and not forward back to the CE. This is referred to as
"split horizon" filtering in this document.

In order to achieve this split horizon function, every multicast,
broadcast or unknown unicast packet is encapsulated with an MPLS
label that identifies the Ethernet segment of origin (i.e. the
segment from which the frame entered the E-VPN network). This label
is referred to as the ESI MPLS label, and is distributed using the
"Ethernet A-D route per Ethernet Segment" as per the procedures in
section 9.1.1 above. This route is imported by the PEs connected to
the CE.

The information about Ethernet Segment and also by the PEs that have at least one EVI
in common with the Ethernet Segment in the route. As described in
section 9.1.1, the route MUST carry an ESI MPLS Label Extended
Community with a valid ESI MPLS label. The disposition PEs rely on
the value of the ESI MPLS label to determine whether or not a flooded
frame is allowed to egress a specific Ethernet Tag segment.

9.3.1 ESI MPLS Label Assignment

The following subsections describe the assignment procedures for the
ESI MPLS label, which differ depending on the type of tunnels being
used to deliver multi-destination packets in the E-VPN network.

9.3.1.1 Ingress Replication

An PE that is using ingress replication for sending broadcast,
multicast or unknown unicast traffic, distributes to other PEs, that
belong to the Ethernet segment, a particular downstream assigned "ESI MPLS
label" in the Ethernet A-D route. This label MUST be programmed in
the platform label space by the advertising PE. Further the
forwarding entry for this label must result in NOT forwarding packets
received with this label onto the Ethernet segment that the label was
distributed for.

Consider PE1 and PE2 that are multi-homed to CE1 on ES1. Further
consider that PE1 is advertised using P2P or MP2P LSPs to send packets to PE2.

Consider that PE1 receives a multicast, broadcast or unknown unicast
packet from CE1 on VLAN1 on ESI1. In this scenario, PE2 distributes
an "Ethernet Auto-Discovery Inclusive Multicast Ethernet Tag route
(Ethernet A-D route)". This for VLAN1 in the associated
EVI. So, when PE1 sends a multicast, broadcast or unknown unicast
packet, that it receives from CE1, it MUST first push onto the MPLS
label stack the ESI label that PE2 has distributed for ESI1. It MUST
then push on the MPLS label distributed by PE2 in the Inclusive
Multicast Ethernet Tag route for VLAN1. The resulting packet is
further encapsulated in the P2P or MP2P LSP label stack required to
transmit the packet to PE2. When PE2 receives this packet it
determines the set of ESIs to replicate the packet to from the top
MPLS label, after any P2P or MP2P LSP labels have been removed. If
the next label is the ESI label assigned by PE2 for ESI1, then PE2
MUST NOT forward the packet onto ESI1.

9.3.1.2. P2MP MPLS LSPs

An PE that is advertised using P2MP LSPs for sending broadcast, multicast or
unknown unicast traffic, distributes to other PEs, that belong to the
Ethernet segment or have an E-VPN NLRI.

The in common with the Ethernet Tag Auto-discovery information SHOULD
Segment, an upstream assigned "ESI MPLS label" in the Ethernet A-D
route. This label is upstream assigned by the PE that advertises the
route. This label MUST be used programmed by the other PEs, that are
connected to enable
active-active load-balancing among MESes as described the ESI advertised in section
"Load Balancing of Unicast Packets". In the case of a multi-homed CE route, in the context label
space for the advertising PE. Further the forwarding entry for this route
label must result in NOT forwarding packets received with this label
onto the Ethernet segment that the label was distributed for. This
label MUST also carry be programmed by the "ESI Label Extended Community" other PEs, that import the route
but are not connected to
enable split horizon as described the ESI advertised in section "Split Horizon". Also, the route can be used route, in the
context label space for Designated Forwarder (DF) election the advertising PE. Further the forwarding
entry for this label must be a POP with no other associated action.

Consider PE1 and PE2 that are multi-homed to CE1 on ES1. Also
consider PE3 that is in the same EVI as
described one of the EVIs to which ES1
belongs. Further, assume that PE1 is using P2MP MPLS LSPs to send
broadcast, multicast or uknown unicast packets. When PE1 sends a
multicast, broadcast or unknown unicast packet, that it receives from
CE1, it MUST first push onto the MPLS label stack the ESI label that
it has assigned for the ESI that the packet was received on. The
resulting packet is further encapsulated in section "Designated Forwarder Election". Further,it MAY the P2MP MPLS label stack
necessary to transmit the packet to the other PEs. Penultimate hop
popping MUST be disabled on the P2MP LSPs used in the MPLS transport
infrastructure for E-VPN. When PE2 receives this packet, it de-
capsulates the top MPLS label and forwards the packet using the
context label space determined by the top label. If the next label is
the ESI label assigned by PE1 to optimize ESI1, then PE2 MUST NOT forward the withdrawal
packet onto ESI1. When PE3 receives this packet, it de-capsulates the
top MPLS label and forwards the packet using the context label space
determined by the top label. If the next label is the ESI label
assigned by PE1 to ESI1 and PE3 is not connected to ESI1, then PE3
MUST pop the label and flood the packet over all local ESIs in the
EVI.

9.3.1.3. MP2MP LSPs

The procedures for ESI MPLS Label assignment and usage for MP2MP LSPs
will be described in a future version.

9.4 Aliasing

In the case where a CE is multi-homed to multiple PE nodes, using a
LAG with all-active redundancy, it is possible that only a single PE
learns a set of the MAC addresses upon failure as
described in section "Convergence". associated with traffic transmitted
by the CE. This section describes procedures leads to a situation where remote PE nodes receive
MAC advertisement routes, for advertising one or more
Ethernet A-D routes per these addresses, from a single PE even
though multiple PEs are connected to the multi-homed segment. As a
result, the remote PEs are not able to effectively load-balance
traffic among the PE nodes connected to the multi-homed Ethernet tag per E-VPN. We will call this as
"Ethernet A-D route per E-VPN".
segment. This section also describes
procedures to advertise could be the case, for e.g. when the PEs perform data-
path learning on the access, and withdraw the load-balancing function on the
CE hashes traffic from a given source MAC address to a single Ethernet A-D route per
Ethernet Segment. We PE.
Another scenario where this occurs is when the PEs rely on control
plane learning on the access (e.g. using ARP), since ARP traffic will call
be hashed to a single link in the LAG.

To alleviate this as "Ethernet issue, E-VPN introduces the concept of 'Aliasing'.
Aliasing refers to the ability of an PE to signal that it has
reachability to a given locally attached Ethernet segment, even when
it has learnt no MAC addresses from that segment. The Ethernet A-D
route per
Segment".

10.1. Constructing EVI is used to that end. Remote PEs which receive MAC
advertisement routes with non-zero ESI SHOULD consider the advertised
MAC address as reachable via all PEs which have advertised
reachability to the relevant Segment using Ethernet A-D Route
The format of routes with
the same ESI (and Ethernet A-D NLRI is specified in section "BGP E-
VPN NLRI".

10.1.1. Tag if applicable).

9.4.1 Constructing the Ethernet A-D Route per E-VPN EVI

This section describes procedures to construct the Ethernet A-D route
when one or more such routes are advertised by an MES PE for a given E-
VPN instance. EVI.
This flavor of the Ethernet A-D route is used for aliasing, and
support of this route flavor is OPTIONAL.

Route-Distinguisher (RD) MUST be set to the RD of the E-VPN instance EVI that is
advertising the NLRI. A An RD MUST be assigned for a given E-VPN
instance EVI on an MES.
PE. This RD MUST be unique across all E-VPN instances EVIs on an MES. PE. It is
RECOMMENDED to use the Type 1 RD [RFC4364]. The value field comprises
an IP address of the MES PE (typically, the loopback address) followed by
a number unique to the MES. PE. This number may be generated by the MES. PE.
Or in the Unique Single VLAN E-
VPN E-VPN case, the low order 12 bits may be the 12
bit VLAN ID, with the remaining high order 4 bits set to 0.

Ethernet Segment Identifier MAY be set to 0. When it is not zero the

The Ethernet Segment Identifier MUST be a ten octet entity as
described in section "Ethernet Segment Identifier". This document
does not specify the use of the Ethernet A-D route when the Segment
Identifier is set to 0.

The Ethernet Tag ID is the identifier of an Ethernet Tag on the
Ethernet segment. This value may be a 12 bit VLAN ID, in which case
the low order 12 bits are set to the VLAN ID and the high order 20
bits are set to 0. Or it may be another Ethernet Tag used by the E-
VPN. It MAY be set to the default Ethernet Tag on the Ethernet
segment or to the value 0.

Note that the above allows the Ethernet A-D route to be advertised
with one of the following granularities:

+ One Ethernet A-D route for a given <ESI, Ethernet Tag ID> tuple
per E-VPN

+ One Ethernet A-D route for a given <Ethernet Tag ID> in a given
E-VPN, for all associated Ethernet segments, where the ESI EVI. This is
set to 0. applicable when the PE uses MPLS-based
disposition.

+ One Ethernet A-D route for per <ESI, EVI> (where the E-VPN where both ESI and Ethernet
Tag ID are set to 0.

E-VPN supports both the non-qualified and qualified learning models.
When non-qualified learning is used, the Ethernet Tag Identifier
specified in this section and in other places in this document MUST
be set to the default Ethernet Tag, e.g., VLAN ID. When qualified
learning 0). This is used, and the Ethernet Tags between MESes and CEs in the
E-VPN are consistently assigned for a given broadcast domain, applicable when the
Ethernet Tag Identifier MUST be set to PE uses
MAC-based disposition, or when the Ethernet Tag, e.g., PE uses MPLS-based
disposition when no VLAN
ID for the concerned broadcast domain between the advertising MES and
the CE. When qualified learning translation is used, and the Ethernet Tags,
e.g., VLAN IDs between MESes and CEs in the E-VPN are not
consistently assigned for a given broadcast domain, the Ethernet Tag
Identifier, e.g., VLAN ID MUST be set to a common E-VPN provider
assigned tag that maps locally on the advertising MES to an Ethernet
broadcast domain identifier such as a VLAN ID. required.

The usage of the MPLS label is described in the section on "Load
Balancing of Unicast Packets".

The Next Hop field of the MP_REACH_NLRI attribute of the route MUST
be set to the IPv4 or IPv6 address of the advertising MES.

10.1.1.1. PE.

9.4.1.1 Ethernet A-D Route Targets

The Ethernet A-D route MUST carry one or more Route Target (RT)
attributes. RTs may be configured (as in IP VPNs), or may be derived
automatically.

If an MES PE uses Route Target Constrain [RT-CONSTRAIN], the MES PE SHOULD
advertise all such RTs using Route Target Constrains. The use of RT
Constrains allows each Ethernet A-D route to reach only those MESes PEs
that are configured to import at least one RT from the set of RTs
carried in the Ethernet A-D route.

10.1.1.1.1.

9.4.1.1.1 Auto-Derivation from the Ethernet Tag ID
The following is the procedure for deriving the RT attribute
automatically from the Ethernet Tag ID associated with the
advertisement:

+ The Global Administrator field of the RT MUST
be set to the Autonomous System (AS) number that the MES PE
belongs to.

+ The Local Administrator field of the RT contains a 4
octets long number that encodes the Ethernet Tag-ID. If the
Ethernet Tag-ID is a two octet VLAN ID then it MUST be
encoded in the lower two octets of the Local Administrator
field and the higher two octets MUST be set to zero.

For the "Unique Single VLAN E-VPN" this results in auto-deriving the RT from
the Ethernet Tag, e.g., VLAN ID for that E-VPN.

10.1.2.

9.5 Designated Forwarder Election

Consider a CE that is a host or a router that is multi-homed directly
to more than one PE in an E-VPN on a given Ethernet A-D Route per segment. One or
more Ethernet Segment

This section describes procedures to construct Tags may be configured on the Ethernet A-D route
when a single such route segment. In this
scenario only one of the PEs, referred to as the Designated Forwarder
(DF), is advertised by an MES responsible for certain actions:

- Sending multicast and broadcast traffic, on a given Ethernet
Segment.

Route-Distinguisher (RD) MUST be
Tag on a Type 1 RD [RFC4364]. The value
field comprises particular Ethernet segment, to the CE.

- Flooding unknown unicast traffic (i.e. traffic for
which an IP address of PE does not know the MES (typically, destination MAC address),
on a given Ethernet Tag on a particular Ethernet segment
to the loopback
address) followed by 0. The reason CE, if the environment requires flooding of
unknown unicast traffic.
Note that this behavior, which allows selecting a DF at the
granularity of <ESI, EVI> for such encoding multicast, broadcast and unknown
unicast traffic, is that the RD
cannot default behavior in this specification.
Optional mechanisms, which will be that of specified in the future, will
allow selecting a given E-VPN since DF at the ESI can span across one or
more E-VPNs.

Ethernet Segment Identifier MUST be granularity of <ESI, EVI, S, G>.

Note that a non-zero ten octet entity as
described in section "Ethernet Segment Identifier".

The Ethernet Tag ID MUST be set CE always sends packets belonging to 0.

If a specific flow
using a single link towards an PE. For instance, if the Ethernet Segment CE is connected a host
then, as mentioned earlier, the host treats the multiple links that
it uses to more than one MES then reach the
"ESI MPLS Label Extended Community" MUST be included PEs as a Link Aggregation Group (LAG). The CE
employs a local hashing function to map traffic flows onto links in
the route. LAG.

If
the Ethernet Segment a bridged network is connected multi-homed to more than one MES and active-
active multi-homing is desired PE in an E-VPN
via switches, then the MPLS label support of all-active points of attachments,
as described in this specification, requires the ESI MPLS
Label Extended Community MUST bridge network to be set
connected to two or more PEs using a valid MPLS label value. The
MPLS label in LAG. In this Extended Community is referred to case the reasons
for doing DF election are the same as an "ESI
label". This label MUST be those described above when a downstream assigned MPLS label if the
advertising MES CE
is using ingress replication for receiving multicast,
broadcast a host or unknown unicast traffic, from other MESes. a router.

If a bridged network does not connect to the
advertising MES is PEs using P2MP MPLS LSPs for sending multicast,
broadcast or unknown unicast traffic, LAG, then this label MUST be an
upstream assigned MPLS label. The usage only
one of the links between the switched bridged network and the PEs
must be the active link for a given Ethernet Tag. In this label is described in
section "Split Horizon".

If case, the
Ethernet Segment is connected to more than one MES and active-
standby multi-homing is desired then A-D route per Ethernet segment MUST be advertised with the
"Active-Standby" bit in flag set to one. Procedures for supporting all-
active points of attachments, when a bridge network connects to the
flags
PEs using LAG, are for further study.

The granularity of the ESI MPLS Label Extended Community DF election MUST be set at least the Ethernet
segment via which the CE is multi-homed to 1. the PEs. If the per Ethernet Segment Ethernet A-D route DF
election is used in conjunction
with done at the per {ESI, VLAN} Ethernet A-D route, for reasons described
below, segment granularity then the MPLS label in the NLRI a single PE
MUST be set to 0.

10.1.2.1. Ethernet A-D Route Targets

The elected as the DF on the Ethernet A-D route MUST carry segment.

If there are one or more Route Target (RT)
attributes. These RTs MUST be EVIs enabled on the set Ethernet segment, then
the granularity of RTs associated with all the
E-VPN instances to which DF election SHOULD be the combination of the
Ethernet Segment, corresponding to segment and EVI on that Ethernet segment. In this case a
single PE MUST be elected as the DF for a particular EVI on that
Ethernet A-D route, belongs.

10.2. Motivations segment.

The detailed procedures for DF election are described next.

9.5.1 Default DF Election Procedure

As a PE discovers the other PEs that are connected to the same
Ethernet A-D Route per Segment, using the Ethernet Segment

This section describes various scenarios in which routes, it starts
building an ordered list based on the Ethernet A-D
route should be advertised per Ethernet Segment.

10.2.1. Multi-Homing

The originating PE IP addresses.
This list is used to select a DF and a backup DF (BDF) on a per
Ethernet Segment Ethernet A-D route MUST be advertised when basis. By default, the PE with the numerically
highest IP address is considered the DF for that Ethernet Segment and
the next PE in the list is multi-homed. This allows Multi-Homed considered the BDF.

If the Ethernet Segment Auto-Discovery. It allows is a multi-homed device, then the set of MESes connected to elected DF
is the
same customer site i.e., CE, to discover each other automatically
with minimal to no configuration. It also allows other MESes only PE that
have at least one E-VPN in common with must forward flooded multi-destination packets
towards the multi-homed Ethernet
Segment segment. All other PE nodes must not permit multi-
destination packets to egress to discover the properties of segment. In the multi-homed case where the
DF fails, the BDF takes over its functionality.

This procedure enables the election of a single DF per Ethernet
Segment.

For active-active multi-homing this route is required
Segment, for split
horizon procedures all EVIs enabled on the segment. It is possible to
achieve more granular load-balancing of traffic among the PE nodes by
employing Service Carving, as described discussed in section "Split Horizon" and MUST
carry the ESI MPLS Label Extended Community next section.

9.5.2 DF Election with a valid ESI MPLS
label. For active-standby multi-homing this route Service Carving
With service carving, it is required possible to
indicate that active-standby multi-homing and not active-active
multi-homing is desired.

This route will be enhanced elect multiple DFs per
Ethernet Segment (one per EVI) in order to carry LAG specific information perform load-balancing of
multi-destination traffic destined to a given Segment. The load-
balancing procedures carve up the EVI space among the PE nodes
evenly, in such a way that every PE is the DF for a disjoint set of
EVIs. The procedure for service carving is as
LACP parameters, which will be encoded as new BGP attributes or
communities, in follows:

1. When a PE discovers the future. Note that this information will be
propagated ESI of the attached Ethernet Segment, it
advertises an Ethernet Segment route with the associated ES-Import
extended community attribute.

2. The PE then starts a timer to all MESes that have one or more sites in allow the VLANs reception of Ethernet
Segment routes from other PE nodes connected to the same Ethernet
Segment. All

3. When the MESes other than timer expires, each PE builds an ordered list of the ones
that are IP
addresses of all the PE nodes connected to the MESes will discard this information.

10.2.2. Optimizing Control Plane Convergence

Ethernet A-D route per Ethernet Segment should be advertised when it
(including itself), in increasing numeric value. Every PE is desired then
given an ordinal indicating its position in the ordered list,
starting with 0 as the ordinal for the PE with the numerically lowest
IP address. The ordinals are used to optimize determine which PE node will be
the control plane convergence of DF for a given EVI on the
withdrawal Ethernet Segment using the following
rule: Assuming a redundancy group of N PE nodes, the Ethernet A-D routes. If this PE with ordinal
i is done then the DF for EVI V when an
Ethernet segment fails, (V mod N) = i.

The above procedure results in the single Ethernet A-D route corresponding
to entire EVI range being divided up
among the segment can be withdrawn first. This allows all MESes that
receive this withdrawal to invalidate PEs in the MAC routes learned from RG, regardless of whether a given EVI is
configured/enabled on the associated Ethernet segment. Segment or not.

4. The PE that is elected as a DF for a given EVI will unblock
traffic for that EVI only if the EVI is configured/enabled on the
Segment. Note that the Ethernet A-D route per Ethernet Segment, when used to
optimize control plane convergence, MAY be advertised DF PE unblocks multi-destination traffic in addition
the egress direction towards the Segment. All non-DF PEs continue to
drop multi-destination traffic (for the Ethernet Tag A-D routes per E-VPN or MAY be advertised on its
own.

10.2.3. Reducing Number of Ethernet A-D Routes

In certain scenarios advertising Ethernet A-D routes per Ethernet
segment, instead of per E-VPN, may reduce associated EVIs) in the number
egress direction towards the Segment.

In the case of link or port failure, the affected PE withdraws its
Ethernet A-D
routes Segment route. This will re-trigger the service carving
procedures on all the PEs in the network. In these scenarios RG. For PE node failure, or upon PE
commissioning or decommissioning, the PEs re-trigger the service
carving. When a service moves from one PE in the RG to another PE as
a result of re-carving, the PE, which ends up being the elected DF
for the service, must trigger a MAC address flush notification
towards the associated Ethernet A-D routes may Segment. This can be
advertised per Ethernet segment instead of per E-VPN.

11. done, for e.g.
using IEEE 802.1ak MVRP 'new' declaration.

10. Determining Reachability to Unicast MAC Addresses
MESes
PEs forward packets that they receive based on the destination MAC
address. This implies that MESes PEs must be able to learn how to reach a
given destination unicast MAC address.

There are two components to MAC address learning, "local learning"
and "remote learning":

11.1.

10.1. Local Learning

A particular MES PE must be able to learn the MAC addresses from the CEs
that are connected to it. This is referred to as local learning.

The MESes PEs in a particular E-VPN MUST support local data plane learning
using standard IEEE Ethernet learning procedures. An MES PE must be
capable of learning MAC addresses in the data plane when it receives
packets such as the following from the CE network:

- DHCP requests

- gratuitous ARP request for its own MAC.

- ARP request for a peer.

Alternatively MESes PEs MAY learn the MAC addresses of the CEs in the
control plane or via management plane integration between the MESes PEs and
the CEs.

There are applications where a MAC address that is reachable via a
given MES PE on a locally attached Segment (e.g. with ESI X) may move
such that it becomes reachable via the same MES PE or another MES PE on
another Segment (e.g. with ESI Y). This is referred to as a "MAC
Move".
Mobility". Procedures to support this are described in section "MAC
Moves".

11.2.
Mobility".

10.2. Remote learning

A particular MES PE must be able to determine how to send traffic to MAC
addresses that belong to or are behind CEs connected to other MESes PEs
i.e. to remote CEs or hosts behind remote CEs. We call such MAC
addresses as "remote" MAC addresses.

This document requires an MES PE to learn remote MAC addresses in the
control plane. In order to achieve this this, each MES PE advertises the MAC
addresses it learns from its locally attached CEs in the control
plane, to all the other MESes PEs in the E-VPN, EVI, using MP-BGP and specifically
the MAC
address advertisement Advertisement route.

11.2.1.

10.2.1. Constructing the BGP E-VPN MAC Address Advertisement
BGP is extended to advertise these MAC addresses using the MAC
advertisement
Advertisement route type in the E-VPN-NLRI. E-VPN NLRI.

The RD MUST be the RD of the E-VPN instance EVI that is advertising the NLRI. The
procedures for setting the RD for a given E-VPN EVI are described in
section "Ethernet A-D Route per E-VPN". 9.4.1.

The Ethernet Segment Identifier is set to the ten octet ESI
identifier described
in section "Ethernet Segment Identifier". Segment".

The Ethernet Tag ID may be zero or may represent a valid Ethernet Tag
ID. This field may be non-zero when there are multiple bridge
domains in the E-VPN instance EVI (e.g., the MES PE needs to perform qualified learning
for the VLANs in that EVPN instance). EVI).

When the the Ethernet Tag ID in the NLRI is set to a non-zero value,
for a particular bridge domain, then this Ethernet Tag may either be
the Ethernet tag value associated with the CE, e.g., VLAN ID, or it
may be the Ethernet Tag Identifier, e.g., VLAN ID assigned by the E-
VPN provider and mapped to the CE's Ethernet tag. The latter would be
the case if the CE Ethernet tags, e.g., VLAN ID, for a particular
bridge domain are different on different CEs.

The MAC address length field is typically set to 48. However this
specification enables specifying the MAC address as a prefix prefix; in
which
case case, the MAC address length field is set to the length of the
prefix. This provides the ability to aggregate MAC addresses if the
deployment environment supports that. The encoding of a MAC address
MUST be the 6-octet MAC address specified by IEEE 802 documents [802.1D-ORIG] [802.1D-REV]. [802.1D-
REV]. If the MAC address is advertised as a prefix then the trailing
bits of the prefix MUST be set to 0 to ensure that the entire prefix
is encoded as 6 octets.

The MPLS Label IP Address Length field value is set to the number of octets in
the MPLS Label IP Address field.

The IP Address field is optional. By default, the IP Address Length
field is set to 0 and the IP address field is omitted from the route.
When a valid IP address is included, it is encoded as specified in
section 12.

The MPLS label field carries one or more labels (that corresponds to
the stack of labels [MPLS-ENCAPS]). Each label is encoded as 3
octets, where the high-order 20 bits contain the label value, and the
low order bit contains "Bottom of Stack" (as defined in [MPLS-ENCAPS]). [MPLS-
ENCAPS]). The MPLS label stack MUST be the downstream assigned E-VPN
MPLS label stack that is used by the MES PE to forward MPLS encapsulated MPLS-encapsulated
Ethernet
packets frames received from remote MESes, PEs, where the destination MAC
address in the Ethernet packet frame is the MAC address advertised in the
above NLRI. The forwarding procedures are specified in section
"Forwarding Unicast Packets" and "Load Balancing of Unicast Packets".

An MES PE may advertise the same single E-VPN label for all MAC addresses
in a given E-VPN instance. EVI. This label assignment methodology is referred to as a
per EVI label assigment.
Alternatively assignment. Alternatively, an MES PE may advertise a unique
E-VPN label per <ESI, Ethernet Tag> combination. This label
assignment methodology is referred to as a per <ESI, Ethernet Tag>
label assignment. Or As a third option, an MES PE may advertise a unique E-VPN E-
VPN label per MAC address. All of these methodologies have their
tradeoffs.

Per EVI label assignment requires the least number of E-VPN labels,
but requires a MAC lookup in addition to an MPLS lookup on an egress
MES
PE for forwarding. On the other hand hand, a unique label per <ESI,
Ethernet Tag> or a unique label per MAC allows an egress MES PE to
forward a packet that it receives from another MES, PE, to the connected
CE, after looking up only the MPLS labels and not without having to do perform a
MAC lookup.

As well as to insert This includes the capability to perform appropriate VLAN
ID translation on egress to the CE A
MES may also advertise more than one label for a given MAC address.
For instance an MES may advertise two labels, one of which is for the
ESI corresponding to the MAC address and the second is for the
Ethernet Tag on the ESI that the MAC address is learnt on.

The IP Address field is optional. By default the IP Address length is
set to 0 and the IP address is excluded. When a valid IP address is
included it is encoded as specified in the section "Optimizing ARP". CE.

The Next Hop field of the MP_REACH_NLRI attribute of the route MUST
be set to the IPv4 or IPv6 address of the advertising MES. PE.

The BGP advertisement that advertises for the MAC advertisement route MUST also carry
one or more Route Target (RT) attributes. RTs may be configured (as
in IP VPNs), or may be derived automatically from the Ethernet Tag
ID, in the Unique Single VLAN case case, as described in section "Ethernet A-D
Route per E-VPN".

It is to be noted that this document does not require MESes PEs to create
forwarding state for remote MACs when they are learnt in the control
plane. When this forwarding state is actually created is a local
implementation matter.

12. Optimizing

11. ARP and ND

The IP address field in the MAC advertisement route may optionally
carry one of the IP addresses associated with the MAC address. This
provides an option which can be used to minimize the flooding of ARP
or Neighbor Discovery (ND) messages to MAC VPN CEs over the MPLS network and to MESes.
remote CEs. This option also minimizes ARP (or ND) message processing
on MAC VPN CEs. A MES end-stations/hosts connected to the E-VPN network. An PE may learn
the IP address associated with a MAC address in the control or
management plane between the CE and the MES. Or PE. Or, it may learn this
binding by snooping certain messages to or from a CE. When a MES an PE
learns the IP address associated with a MAC address, of a locally
connected CE, it may advertise it this address to other MESes PEs by including
it in the MAC route
advertisement. Advertisement route. The IP Address may be an IPv4, IPv4
address encoded using four
octets octets, or an IPv6 address encoded using
sixteen octets. The IP Address length field MUST be set to 32 for an
IPv4 address and or to 128 for an IPv6 address.

If there are multiple IP addresses associated with a MAC address address,
then multiple MAC advertisement routes MUST be generated, one for
each IP address. For instance instance, this may be the case when there is are
both an IPv4 and an IPv6 address associated with the MAC address.
When the IP address is dis-associated dissociated with the MAC address address, then the MAC
advertisement route with that particular IP address MUST be
withdrawn.

When an MES PE receives an ARP request for an IP address from a CE, and
if the MES PE has the MAC address binding for that IP address, the MES
should PE
SHOULD perform ARP proxy and respond to the ARP request.

Further detailed procedures will be specified in a later version.

13. Designated Forwarder Election

Consider a CE that is a host or a router that is multi-homed directly
to more than one MES in an E-VPN on a given Ethernet segment. One or
more Ethernet Tags may be configured on the Ethernet segment. In this
scenario only one of the MESes, referred to as the Designated
Forwarder (DF), is responsible for certain actions:

- Sending multicast and broadcast traffic, on a given Ethernet
Tag on a particular Ethernet segment, to the CE. Note that
this behavior, which allows selecting a DF at the
granularity of <ESI, Ethernet Tag> for multicast and
broadcast traffic is the default behavior in this
specification. Optional mechanisms, which will be
specified in the future, will allow selecting a DF
at the granularity of <ESI, Ethernet Tag, S, G>.

- Flooding unknown unicast traffic (i.e. traffic for
which an MES does not know the destination MAC address),
on a given Ethernet Tag on a particular Ethernet segment
to the CE, if the environment requires flooding of
unknown unicast traffic.

Note that a CE always sends packets belonging to a specific flow
using a single link towards an MES. For instance, if the CE is a host
then, as mentioned earlier, the host treats the multiple links that
it uses to reach the MESes as a Link Aggregation Group (LAG). The CE
employs a local hashing function to map traffic flows onto links in
the LAG.

If a bridge network is multi-homed to more than one MES in an E-VPN
via switches, then the support of active-active points of attachments
as described in this specification requires the bridge network to be
connected to two or more MESes using a LAG. In this case the reasons
for doing DF election are the same as those described above when a CE
is a host or a router.

If a bridge network does not connect to the MESes using LAG, then
only one of the links between the switched bridged network and the
MESes must be the active link. In this case the per Ethernet Segment
Ethernet Tag routes MUST be advertised with the "Active-Standby" flag
set to one. Procedures for supporting active-active points of
attachments, when a bridge network does not connect to the MESes
using LAG, are for further study.

The granularity of the DF election MUST be at least the Ethernet
segment via which the CE is multi-homed to the MESes. If the DF
election is done at the Ethernet segment granularity then a single
MES MUST be elected as the DF on the Ethernet segment.

If there are one or more Ethernet Tags (e.g., VLANs) on the Ethernet
segment then the granularity of the DF election SHOULD be the
combination of the Ethernet segment and Ethernet Tag on that Ethernet
segment. In this case a single MES MUST be elected as the DF for a
particular Ethernet Tag on that Ethernet segment.

There are two specified mechanisms for performing DF election.

13.1. DF Election Performed by All MESes

The MESes perform a designated forwarder (DF) election, for an
Ethernet segment, or <ESI, Ethernet Tag> combination using the
Ethernet Tag A-D BGP route described in section "Auto-Discovery of
Ethernet Tags on Ethernet Segments".

The DF election for a particular ESI or a particular <ESI, Ethernet
Tag> combination proceeds as follows. First an MES constructs a
candidate list of MESes. This comprises all the Ethernet A-D routes
with that particular ESI or <ESI, Ethernet Tag> tuple that an MES
imports in an E-VPN instance, including the Ethernet A-D route(s)
generated by the MES itself, if any. The DF MES is chosen from this
candidate list. Note that DF election is carried out by all the MESes
that import the DF route.

The default procedure for choosing the DF is the MES with the highest
IP address, of all the MESes in the candidate list. This procedure
MUST be implemented. It ensures that, except during routing
transients each MES chooses the same DF MES for a given ESI and
Ethernet Tag combination.

Other alternative procedures for performing DF election are possible
and will be described in the future.

13.2. DF Election Performed Only on Multi-Homed MESes

As an MES discovers other MESs that are members of the same multi-
homed segment, using per Ethernet Segment Ethernet A-D Routes, it
starts building an ordered list based on the originating MES IP
addresses. This list is used to select a DF and a backup DF (BDF) on
a per group of Ethernet Tag basis. For example, the MES with the
numerically highest IP address is considered the DF for a given group
of VLANs for that Ethernet segment and the next MES in the list is
considered the BDF. To that end, the range of Ethernet Tags
associated with the CE must be partitioned into disjoint sets. The
size of each set is a function of the total number of CE Ethernet
Tags and the total number of MESs that the Ethernet segment is multi-
homed to. The DF can employ any distribution function that achieves
an even distribution of Ethernet Tags across the MESes that are
multi-homed to the Ethernet segment. The DF takes over the Ethernet
Tag set of any MES encountering either a node failure or a
link/Ethernet segment failure causing that MES to be isolated from
the multi-homed segment. In case of a failure that is affecting the
DF, then the BDF takes over the DF VLAN set.

It should be noted that once all the MESs participating in an
Ethernet segment have the same ordered list for that site, then
Ethernet Tag groups can be assigned to each member of that list
deterministically without any need to explicitly distribute Ethernet
Tags among the member MESs of that list. In other words, the DF
election for a group of Ethernet Tags is a local matter and can be
done deterministically. As an example, consider, that the ordered
list consists of m MESes: (MES1, MES2,., MESm), and there are n
Ethernet Tags for that site (V0, V1, V2, ., Vn-1). Then MES1 and MES2
can be the DF and the BDF respectively for all the Ethernet Tags
corresponding to (i mod m) for i:0 to n-1. MES2 and MES3 can be the
DF and the BDF respectively for all the Ethernet Tags corresponding
to (i mod m) + 1 and so on till the last MES in the order list is
reached. As a result MESm and MES1 is the DF and the BDF respectively
for the all the VLANs corresponding to (i mod m) + m-1.

14.

12. Handling of Multi-Destination Traffic

Procedures are required for a given MES PE to send broadcast or multicast
traffic, received from a CE encapsulated in a given Ethernet Tag in
an E-VPN, EVI, to all the other MESes PEs that span that Ethernet Tag in the E-VPN. EVI.
In certain scenarios, described in section "Processing of Unknown
Unicast Packets", a given MES PE may also need to flood unknown unicast
traffic to other MESes. PEs.

The MESes PEs in a particular E-VPN may use ingress replication or replication, P2MP LSPs
or MP2MP LSPs to send unknown unicast, broadcast or multicast traffic
to other MESes. PEs.

Each MES PE MUST advertise an "Inclusive Multicast Ethernet Tag Route" to
enable the above. Next section The following subsection provides the procedures to
construct the Inclusive Multicast Ethernet Tag route. Subsequent sections
subsections describe in further detail its usage.

14.1.

12.1. Construction of the Inclusive Multicast Ethernet Tag Route

The RD MUST be the RD of the E-VPN instance EVI that is advertising the NLRI. The
procedures for setting the RD for a given E-VPN are described in
section "Ethernet A-D Route per E-VPN".

The Ethernet Segment Identifier MAY be set to the ten octet ESI
identifier described in section "Ethernet Segment Identifier". Or it
MAY be set to 0. It MUST be set to 0 if the Ethernet Tag is set to
0. 9.4.1.

The Ethernet Tag ID is the identifier of the Ethernet Tag. It MAY be
set to 0 in which case an egress MES MUST perform a MAC lookup or to
forward the packet. a valid Ethernet Tag value.

The Originating Router's IP address MUST be set to an IP address of
the PE. This address SHOULD be common for all the EVIs on the PE
(e.,g., this address may be PE's loopback address).

The Next Hop field of the MP_REACH_NLRI attribute of the route MUST
be set to the same IP address as the one carried in the Originating
Router's IP Address field.

The BGP advertisement that advertises for the Inclusive Multicast Ethernet Tag route
MUST also carry one or more Route Target (RT) attributes. The
assignment of RTs described in the section on "Constructing the BGP
E-VPN MAC Address Advertisement" MUST be followed.

14.2.

12.2. P-Tunnel Identification

In order to identify the P-Tunnel used for sending broadcast, unknown
unicast or multicast traffic, the Inclusive Multicast Ethernet Tag
route MUST carry a "PMSI Tunnel Attribute" as specified in [BGP
MVPN].

Depending on the technology used for the P-tunnel for the E-VPN on
the PE, the PMSI Tunnel attribute of the Inclusive Multicast Ethernet
Tag route is constructed as follows.

+ If the PE that originates the advertisement uses a
P-Multicast tree for the P-tunnel for the E-VPN, the PMSI
Tunnel attribute MUST contain the identity of the tree
(note that the PE could create the identity of the
tree prior to the actual instantiation of the tree).

+ A An PE that uses a P-Multicast tree for the P-tunnel MAY
aggregate two or more Ethernet Tags in the same or different
E-VPNs
EVIs present on the PE onto the same tree. In this case case, in
addition to carrying the identity of the tree, the PMSI Tunnel
attribute MUST carry an MPLS upstream assigned label which
the PE has bound uniquely to the <ESI, Ethernet Tag> Tag for
E-VPN the EVI
associated with this update (as determined by its RTs).

If the PE has already advertised Inclusive Multicast
Ethernet Tag routes for two or more Ethernet Tags that it
now desires to aggregate, then the PE MUST re-advertise
those routes. The re-advertised routes MUST be the same
as the original ones, except for the PMSI Tunnel attribute
and the label carried in that attribute.

+ If the PE that originates the advertisement uses ingress
replication for the P-tunnel for the E-VPN, the route MUST
include the PMSI Tunnel attribute with the Tunnel Type set to
Ingress Replication and Tunnel Identifier set to a routable
address of the PE. The PMSI Tunnel attribute MUST carry a
downstream assigned MPLS label. This label is used to
demultiplex the broadcast, multicast or unknown unicast E-VPN
traffic received over a unicast MP2P tunnel by the PE.

+ The Leaf Information Required flag of the PMSI Tunnel
attribute MUST be set to zero, and MUST be ignored on receipt.

14.3. Ethernet Segment Identifier and Ethernet Tag

As described above the encoding rules allow setting the Ethernet
Segment Identifier and Ethernet Tag to either non-zero valid values
or to 0. If the Ethernet Tag is set to a non-zero valid value, then
an egress MES can forward the packet to the set of egress ESIs in the
Ethernet Tag, in the E-VPN, by performing an MPLS lookup only.
Further if the ESI is also set to non zero then the egress MES does
not need to replicate the packet as it is destined for a given
Ethernet segment. If both Ethernet Tag and ESI are set to 0 then an
egress MES MUST perform a MAC lookup in the EVI determined by the
MPLS label, after the MPLS lookup, to forward the packet.

If an MES advertises multiple Inclusive Ethernet Tag routes for a
given E-VPN then the PMSI Tunnel Attributes for these routes MUST be
distinct.

15.

13. Processing of Unknown Unicast Packets

The procedures in this document do not require MESes the PEs to flood
unknown unicast traffic to other MESes. PEs. If MESes PEs learn CE MAC addresses
via a control plane, plane protocol, the MESes PEs can then distribute MAC
addresses via BGP, and all unicast MAC addresses will be learnt prior
to traffic to those destinations.

However, if a destination MAC address of a received packet is not
known by the MES, PE, the MES PE may have to flood the packet. Flooding must
take into account "split horizon forwarding" as follows. follows: The
principles behind the following procedures are borrowed from the
split horizon forwarding rules in VPLS solutions [RFC 4761, RFC
4762]. When an MES PE capable of flooding (say MESx) PEx) receives a broadcast
or multicast Ethernet frame, or one with an unknown destination MAC
address, it must flood the frame. If the frame arrived from an
attached CE, MESx PEx must send a copy of the frame to every other
attached CE, CE participating in the EVI, on a different ESI than the one
it received the frame on, as well long as the PE is the DF for the egress
ESI. In addition, the PE must flood the frame to all other MESs PEs
participating in the E-VPN. EVI. If, on the other hand, the frame arrived
from another MES PE (say MESy), MESx PEy), PEx must send a copy of the packet only to
attached CEs. MESx CEs as long as it is the DF for the egress ESI. PEx MUST NOT
send the frame to other MESs, PEs, since MESy PEy would have already done so.
Split horizon forwarding rules apply to broadcast and multicast
packets, as well as packets to an unknown MAC address.

Whether or not to flood packets to unknown destination MAC addresses
should be an administrative choice, depending on how learning happens
between CEs and MESes. PEs.

The MESes PEs in a particular E-VPN may use ingress replication using
RSVP-TE RSVP-
TE P2P LSPs or LDP MP2P LSPs for sending broadcast, multicast and
unknown unicast traffic to other MESes. PEs. Or they may use RSVP-TE P2MP or
LDP P2MP or LDP MP2MP LSPs for sending such traffic to other
MESes.

15.1. PEs.

13.1. Ingress Replication

If ingress replication is in use, the P-Tunnel attribute, carried in
the Inclusive Multicast Ethernet Tag routes for the E-VPN, EVI, specifies
the downstream label that the other MESes PEs can use to send unknown
unicast, multicast or broadcast traffic for the E-VPN EVI to this
particular MES. PE.

The MES PE that receives a packet with this particular MPLS label MUST
treat the packet as a broadcast, multicast or unknown unicast packet.
Further if the MAC address is a unicast MAC address, the MES PE MUST
treat the packet as an unknown unicast packet.

15.2.

13.2. P2MP MPLS LSPs

The procedures for using P2MP LSPs are very similar to VPLS
procedures [VPLS-MCAST]. The P-Tunnel attribute used by an MES PE for
sending unknown unicast, broadcast or multicast traffic for a
particular Ethernet segment, EVI is advertised in the Inclusive Ethernet Tag Multicast
route as described in section "Handling of Multi-
Destination Multi-Destination
Traffic".

The P-Tunnel attribute specifies the P2MP LSP identifier. This is the
equivalent of an Inclusive tree in [VPLS-MCAST]. Note that multiple
Ethernet Tags, which may be in different E-VPNs, EVIs, may use the same P2MP
LSP, using upstream labels [VPLS-MCAST]. This is the equivalent of an
Aggregate Inclusive tree in [VPLS-MCAST]. When P2MP LSPs are used for
flooding unknown unicast traffic, packet re-ordering is possible.

The MES PE that receives a packet on the P2MP LSP specified in the PMSI
Tunnel Attribute MUST treat the packet as a broadcast, multicast or
unknown unicast packet. Further if the MAC address is a unicast MAC
address, the MES PE MUST treat the packet as an unknown unicast packet.

16.

14. Forwarding Unicast Packets

16.1.

14.1. Forwarding packets received from a CE

When an MES PE receives a packet from a CE, on a given Ethernet Tag, it
must first look up the source MAC address of the packet. In certain
environments the source MAC address MAY be used to authenticate the
CE and determine that traffic from the host can be allowed into the
network. Source MAC lookup MAY also be used for local MAC address
learning.

If the MES PE decides to forward the packet packet, the destination MAC address
of the packet must be looked up. If the MES PE has received MAC address
advertisements for this destination MAC address from one or more
other MESes PEs or learned it from locally connected CEs, it is considered
as a known MAC address. Else Otherwise, the MAC address is considered as
an unknown MAC address.

For known MAC addresses the MES PE forwards this packet to one of the
remote MESes PEs or to a locally attached CEs. CE. When forwarding to a remote
MESes,
PE, the packet is encapsulated in the E-VPN MPLS label advertised by
the remote MES, PE, for that MAC address, and in the MPLS LSP label stack
to reach the remote MES. PE.

If the MAC address is unknown then, and if the administrative policy on the MES
PE requires flooding of unknown unicast traffic: traffic then:

- The MES PE MUST flood the packet to other MESes. If the ESI
over which the MES receives the packet is multi-homed, then
the MES PEs. The
PE MUST first encapsulate the packet in the ESI MPLS
label as described in section "Split Horizon". 9.3.
If ingress replication is used used, the packet MUST be replicated
one or more times to each remote MES PE with the bottom outermost
label
of the stack being an MPLS label determined as follows. follows: This
is the MPLS label advertised by the remote MES PE in a PMSI
Tunnel Attribute in the Inclusive Multicast Ethernet Tag
route for an <ESI, <EVI, Ethernet Tag> combination. The Ethernet
Tag in the route must be the same as the Ethernet Tag
advertised by the ingress MES in its Ethernet Tag A-D route
associated with the interface on which the ingress MES PE
receives the packet. If P2MP LSPs are being used the packet
MUST be sent on the P2MP LSP that the MES PE is the root of for
the Ethernet Tag in the E-VPN. EVI. If the same P2MP LSP is used
for all Ethernet Tags Tags, then all the MESes PEs in the E-VPN EVI MUST
be the leaves of the P2MP LSP. If a distinct P2MP LSP is
used for a given Ethernet Tag in the E-VPN EVI, then only the
MESes
PEs in the Ethernet Tag MUST be the leaves of the P2MP
LSP. The packet MUST be encapsulated in the P2MP LSP label
stack.

If the MAC address is unknown then, if the admnistrative administrative policy on
the MES PE does not allow flooding of unknown unicast traffic:

- The MES PE MUST drop the packet.

16.2.

14.2. Forwarding packets received from a remote MES
16.2.1. PE
14.2.1. Unknown Unicast Forwarding

When an MES PE receives an MPLS packet from a remote MES PE then, after
processing the MPLS label stack, if the top MPLS label ends up being
a P2MP LSP label associated with an E-VPN EVI or the downstream label
advertised in the P-Tunnel attribute attribute, and after performing the split
horizon procedures described in section "Split Horizon":

- If the MES PE is the designated forwarder of unknown unicast, broadcast
or multicast traffic, on a particular set of ESIs for the Ethernet
Tag, the default behavior is for the MES PE to flood the packet on the these
ESIs. In other words words, the default behavior is for the MES PE to assume
that the destination MAC address is unknown unicast, broadcast or
multicast and it is not required to do perform a destination MAC address
lookup, as long as the granularity of the MPLS label included the
Ethernet Tag.
lookup. As an option option, the MES PE may do perform a destination MAC lookup to
flood the packet to only a subset of the CE interfaces in the
Ethernet Tag. For instance the MES PE may decide to not flood an unknown
unicast packet on certain Ethernet segments even if it is the DF on
the Ethernet segment, based on administrative policy.

- If the MES PE is not the designated forwarder on any of the ESIs for
the Ethernet Tag, the default behavior is for it to drop the packet.

16.2.2.

14.2.2. Known Unicast Forwarding

If the top MPLS label ends up being an E-VPN label that was
advertised in the unicast MAC advertisements, then the MES PE either
forwards the packet based on CE next-hop forwarding information
associated with the label or does a destination MAC address lookup to
forward the packet to a CE.

17. Split Horizon

Consider a CE that is multi-homed to two or more MESes on an Ethernet
segment ES1. If the CE sends a multicast, broadcast or unknown
unicast packet to a particular MES, say MES1, then MES1 will forward
that packet to all or subset of the other MESes in the E-VPN. In this
case the MESes, other than MES1, that the CE is multi-homed to MUST
drop the packet and not forward back to the CE. This is referred to
as "split horizon" in this document.

In order to accomplish this each MES distributes to other MESes the
"per Ethernet Segment Ethernet A-D route" as per the procedures in
the section "Ethernet A-D Route per Ethernet Segment". This route is
imported by the MESes connected to the Ethernet Segment and also by
the MESes that have at least one E-VPN in common with the Ethernet
Segment in the route. As described in the section "Ethernet A-D Route
per Ethernet Segment", the route MUST carry an ESI MPLS Label
Extended Community with a valid ESI MPLS label.

17.1. ESI MPLS Label: Ingress Replication

An MES that is using ingress replication for sending broadcast,
multicast or unknown unicast traffic, distributes to other MESes,
that belong to the Ethernet segment, a downstream assigned "ESI MPLS
label" in the Ethernet A-D route. This label MUST be programmed in
the platform label space by the advertising MES. Further the
forwarding entry for this label must result in NOT forwarding packets
received with this label onto the Ethernet segment that the label was
distributed for.

Consider MES1 and MES2 that are multi-homed to CE1 on ES1. Further
consider that MES1 is using P2P or MP2P LSPs to send packets to MES2.
Consider that MES1 receives a multicast, broadcast or unknown unicast
packet from CE1 on VLAN1 on ESI1.

First consider the case where MES2 distributes an unique Inclusive
Multicast Ethernet Tag route for VLAN1, for each Ethernet segment on
MES2. In this case MES1 MUST NOT replicate the packet to MES2 for
<ESI1, VLAN1>.

Next consider the case where MES2 distributes a single Inclusive
Multicast Ethernet Tag route for VLAN1 for all Ethernet segments on
MES2. In this case when MES1 sends a multicast, broadcast or unknown
unicast packet, that it receives from CE1, it MUST first push onto
the MPLS label stack the ESI label that MES2 has distributed for
ESI1. It MUST then push on the MPLS label distributed by MES2 in the
Inclusive Ethernet Tag Multicast route for Ethernet Tag1. The
resulting packet is further encapsulated in the P2P or MP2P LSP label
stack required to transmit the packet to MES2. When MES2 receives
this packet it determines the set of ESIs to replicate the packet to
from the top MPLS label, after any P2P or MP2P LSP labels have been
removed. If the next label is the ESI label assigned by MES2 then
MES2 MUST NOT forward the packet onto ESI1.

17.2. ESI MPLS Label: P2MP MPLS LSPs

An MES that is using P2MP LSPs for sending broadcast, multicast or
unknown unicast traffic, distributes to other MESes, that belong to
the Ethernet segment or have an E-VPN in common with the Ethernet
Segment, an upstream assigned "ESI MPLS label" in the Ethernet A-D
route. This label is upstream assigned by the MES that advertises the
route. This label MUST be programmed by the other MESes, that are
connected to the ESI advertised in the route, in the context label
space for the advertising MES. Further the forwarding entry for this
label must result in NOT forwarding packets received with this label
onto the Ethernet segment that the label was distributed for. This
label MUST also be programmed by the other MESes, that import the
route but are not connected to the ESI advertised in the route, in
the context label space for the advertising MES. Further the
forwarding entry for this label must be a POP with no other
associated action.

Consider MES1 and MES2 that are multi-homed to CE1 on ES1. Also
consider MES3 that is in the same E-VPN as one of the E-VPNs to which
ES1 belongs. Further assume that MES1 is using P2MP MPLS LSPs to
send broadcast, multicast or uknown unicast packets. When MES1 sends
a multicast, broadcast or unknown unicast packet, that it receives
from CE1, it MUST first push onto the MPLS label stack the ESI label
that it has assigned for the ESI that the packet was received on. The
resulting packet is further encapsulated in the P2MP MPLS label stack
necessary to transmit the packet to the other MESes. Penultimate hop
popping MUST be disabled on the P2MP LSPs used in the MPLS transport
infrastructure for E-VPN. When MES2 receives this packet it
decapsulates the top MPLS label and forwards the packet using the
context label space determined by the top label. If the next label is
the ESI label assigned by MES1 then MES2 MUST NOT forward the packet
onto ESI1. When MES3 receives this packet it decapsulates the top
MPLS label and forwards the packet using the context label space
determined by the top label. If the next label is the ESI label
assigned by MES1 then MES3 MUST pop the label.

17.3. ESI MPLS Label: MP2MP LSPs

The procedures for ESI MPLS Label assignment and usage for MP2MP LSPs
will be described in a future version.

18.

15. Load Balancing of Unicast Packets Frames

This section specifies how the load balancing is achieved to/from a CE
that has more than one interface that is directly connected procedures for sending
known unicast frames to one or
more MESes. The CE may be a host or a router or it may be a switched
network that is connected via LAG to the MESes.

18.1. multi-homed CE.

15.1. Load balancing of traffic from an MES PE to remote CEs

Whenever a remote MES PE imports a MAC advertisement for a given <ESI,
Ethernet Tag> in an E-VPN instance, EVI, it MUST consider the MAC as
reachahable via examine all the MESes from which it has imported Ethernet A-D
routes for that <ESI, Ethernet Tag>. Let us call this ESI in order to determine the initial
Ethernet A-D route set for load-balancing
characteristics of the given ESI. Ethernet segment.

15.1.1 Active-Standby Redundancy Mode

For the a given ESI ESI, if the remote MES PE has imported a an Ethernet A-D route
per Ethernet Segment
Ethernet A-D route, from at least one MES, PE, where the "Active-Standby"
flag in the ESI MPLS Label Extended Community is set, then the remote
MES
PE MUST first use deduce that the procedures Ethernet segment is operating in Active-
Standby redundancy mode. As such, the section "Designated
Forwarder Election" MAC address will be reachable
only via the PE announcing the associated MAC Advertisement route -
this is referred to pick a Designated Forwarder. as the primary PE. The eligible set of other PE nodes
advertising Ethernet A-D routes used per Ethernet Segment for the same ESI
serve as backup paths, in case the procedures below must comprise
this active PE encounters a failure.
These are referred to as the backup PEs.

If the primary PE encounters a failure, it MAY withdraw its Ethernet
A-D route for the affected segment prior to withdrawing the entire
set of MAC Advertisement routes. In the case where only a single
other backup PE in the network had advertised an Ethernet A-D route from
for the DF. same ESI, the remote PE can then use the Ethernet A-D route
withdrawal as a trigger to update its forwarding entries, for the
associated MAC addresses, to point towards the backup PE. As the
backup PE starts learning the MAC addresses over its attached
Ethernet segment, it will start sending MAC Advertisement routes
while the failed PE withdraws its own. This mechanism minimizes the
flooding of traffic during fail-over events.

15.1.2 All-Active Redundancy Mode

If for the given ESI ESI, none of the Ethernet A-D routes per Ethernet
Segment Ethernet A-D
routse, imported by the remote MES, PE have the "Active-Standby" flag set
in the ESI MPLS Label Extended Community, then the eligble set remote PE MUST
treat the Ethernet segment as operating in all-active redundancy
mode. The remote PE would then treat the MAC address as reachable via
all of the PE nodes from which it has received both an Ethernet A-D routes is set to the initial
route per Ethernet Segment as well as an Ethernet A-D route set. per EVI
for the ESI in question. The remote MES PE MUST use the MAC advertisement
and eligible Ethernet A-D routes to constuct construct the set of next-hops
that it can use to send the packet to the destination MAC. Each next-hop next-
hop comprises an MPLS label stack, stack that is to be used by the egress MES PE
to forward the packet. This label stack is determined as follows. If follows:

-If the next-hop is constructed as a result of a MAC route which has a valid MPLS label
stack, then this
label stack MUST be used. However However, if the MAC route doesn't exist or if it doesn't have a valid MPLS label stack exist,
then the next-hop and MPLS label stack is constructed as a result of one or
more corresponding
the Ethernet A-D routes as follows. routes. Note that the following description applies
to determining the label stack for a particular next-hop to reach a
given MES, PE, from which the remote MES PE has received and imported one or more Ethernet
A-D routes that have the matching ESI and Ethernet Tag as the one
present in the MAC advertisement. The Ethernet A-D routes mentioned
in the following description refer to the ones imported from this
given MES.

If there is a corresponding Ethernet A-D route for that <ESI,
Ethernet Tag> then that label stack MUST be used. If such PE.

-If an Ethernet
Tag A-D route doesn't exist but Ethernet A-D routes exist for <ESI,
Ethernet Tag = 0> and <ESI = 0, Ethernet Tag> then the label stack
must be constructed by using the labels from these two routes. If
this is not the case but an per Ethernet A-D route exists Segment for <ESI,
Ethernet Tag = 0> then the label from that route must be used.
Finally if this is also not the case but ESI exists,
together with an Ethernet A-D route exists
for <ESI = 0, Ethernet Tag = 0> per EVI, then the label from that
latter route must be used.

The following example explains the above when Ethernet A-D routes are
advertised per <ESI, Ethernet Tag>. above.

Consider a CE, CE1, CE (CE1) that is dual homed dual-homed to two MESes, MES1 PEs (PE1 and MES2 PE2) on a
LAG interface, ES1, interface (ES1), and is sending packets with MAC address MAC1 on
VLAN1. Based on E-VPN extensions described in sections "Determining
Reachability of Unicast Addresses" and "Auto-Discovery of Ethernet
Tags on Ethernet Segments", a A remote MES PE, say MES3 PE3, is able to learn that a MAC1 is reachable
via MES1 PE1 and MES2. PE2. Both MES1 PE1 and MES2 PE2 may advertise MAC1 in BGP if they
receive packets with MAC1 from CE1. If this is not the case case, and if
MAC1 is advertised only by MES1, MES3 PE1, PE3 still considers MAC1 as reachable
via both MES1 PE1 and MES2 PE2 as both MES1 PE1 and MES2 PE2 advertise a Ethernet A-D
route per ESI for ESI1 as well as an Ethernet A-D route per EVI for
<ESI1, VLAN1>.

The MPLS label stack to send the packets to MES1 PE1 is the MPLS LSP stack
to get to MES1 PE1 and the E-VPN label advertised by MES1 PE1 for CE1's MAC.

The MPLS label stack to send packets to MES2 PE2 is the MPLS LSP stack to
get to MES2 PE2 and the MPLS label in the Ethernet A-D route advertised by MES2
PE2 for <ES1, VLAN1>, if MES2 PE2 has not advertised MAC1 in BGP.

We will refer to these label stacks as MPLS next-hops.

The remote MES, MES3, PE (PE3) can now load balance the traffic it receives from
its CEs, destined for CE1, between MES1 PE1 and MES2. MES3 PE2. PE3 may use
the IP N-Tuple
flow information for it to hash traffic into one of the MPLS next-hops for
load balancing for of IP traffic. Or MES3 Alternatively PE3 may rely on the
source and
destination MAC addresses for load balancing.

Note that once MES3 PE3 decides to send a particular packet to MES1 PE1 or
MES2 PE2
it can pick from more than path one out of multiple possible paths to reach the
particular remote
MES PE using regular MPLS procedures. For instance instance, if
the tunneling technology is based on RSVP-TE LSPs, and MES3 PE3 decides to
send a particular packet to MES1 PE1, then MES3 PE3 can choose from multiple
RSVP-TE LSPs that have MES1 PE1 as their destination.

When MES1 PE1 or MES2 PE2 receive the packet destined for CE1 from MES3, PE3, if the
packet is a unicast MAC packet it is forwarded to CE1. If it is a
multicast or broadcast MAC packet then only one of MES1 PE1 or MES2 PE2 must
forward the packet to the CE. Which of MES1 PE1 or MES2 PE2 forward this packet
to the CE is determined by default based on which of the two is the DF. An alternate procedure to load balance multicast packets
will be described in the future.

If the connectivity between the multi-homed CE and one of the MESes PEs
that it is multi-homed attached to fails, the MES MUST withdraw the MAC
address from BGP. In addition the MES PE MUST withdraw the Ethernet Tag
A-D routes, that had been previously advertised, for the Ethernet
Segment to the CE. When the MAC entry on the PE ages out, the PE MUST
withdraw the MAC address from BGP. Note that to aid convergence convergence, the
Ethernet Tag A-D routes MAY be withdrawn before the MAC routes. This
enables the remote MESes PEs to remove the MPLS next-hop to this particular MES
PE from the set of MPLS next-hops that can be used to forward traffic
to the CE. For further details and procedures on withdrawal of E-VPN
route types in the event of MES PE to CE failures please section "MES "PE to
CE Network Failures".

18.2.

15.2. Load balancing of traffic between an MES PE and a local CE

A CE may be configured with more than one interface connected to
different MESes PEs or the same MES PE for load balancing, using a technology
such as LAG. The MES(s) PE(s) and the CE can load balance traffic onto these
interfaces using one of the following mechanisms.

18.2.1.

15.2.1. Data plane learning

Consider that the MESes PEs perform data plane learning for local MAC
addresses learned from local CEs. This enables the MES(s) PE(s) to learn a
particular MAC address and associate it with one or more interfaces,
if the technology between the MES PE and the CE supports multi-pathing.
The MESes PEs can now load balance traffic destined to that MAC address on
the multiple interfaces.

Whether the CE can load balance traffic that it generates on the
multiple interfaces is dependent on the CE implementation.

18.2.2.

15.2.2. Control plane learning

The CE can be a host that advertises the same MAC address using a
control protocol on both interfaces. This enables the MES(s) PE(s) to learn
the host's MAC address and associate it with one or more interfaces.
The MESes PEs can now load balance traffic destined to the host on the
multiple interfaces. The host can also load balance the traffic it
generates onto these interfaces and the MES PE that receives the traffic
employs E-VPN forwarding procedures to forward the traffic.

19.

16. MAC Moves

In the case where a CE Mobility

It is possible for a given host or a switched network connected to
hosts, the end-station (as defined by its MAC address that is reachable via a given MES on a
particular ESI may
address) to move such that it becomes reachable via another
MES on another ESI. This from one Ethernet segment to another; this is
referred to as a "MAC Move".

Remote MESes must be able to distinguish a MAC move 'MAC Mobility' or 'MAC move' and it is different from
the case
where multi-homing situation in which a given MAC address on an ESI is reachable
via multiple PEs for the same Ethernet segment. In a MAC move, there
would be two different MESes sets of MAC Advertisement routes, one set with the new
Ethernet segment and load balancing is performed as described one set with the previous Ethernet segment, and
the MAC address would appear to be reachable via each of these
segments.

In order to allow all of the PEs in section "Load
Balancing the E-VPN to correctly determine
the current location of Unicast Packets". This distinction can be made as
follows. If a the MAC is learned address, all advertisements of it
being reachable via the previous Ethernet segment MUST be withdrawn
by a particular MES from multiple MESes,
then the MES performs load balancing only amongst PEs, for the set of MESes previous Ethernet segment, that had advertised
it.

If local learning is performed using the data plane, these PEs will
not be able to detect that the MAC address has moved to another
Ethernet segment and the receipt of MAC Advertisement routes, with
the same ESI. MAC Mobility extended community attribute, from other PEs serves
as the trigger for these PEs to withdraw their advertisements. If this
local learning is not performed using the case
then control or management planes,
these interactions serve as the MES chooses only one trigger for these PEs to withdraw
their advertisements.

In a situation where there are multiple moves of a given MAC,
possibly between the advertising MESes same two Ethernet segments, there may be
multiple withdrawals and re-advertisements. In order to reach ensure that
all PEs in the
MAC as per E-VPN receive all of these correctly through the
intervening BGP path selection.

There can be traffic loss during a MAC move. Consider MAC1 that infrastructure, it is
advertised by MES1 and learned from CE1 on ESI1. If MAC1 now moves
behind MES2, on ESI2, MES2 advertises necessary to introduce a
sequence number into the MAC in BGP. Until a remote
MES, MES3, determines that Mobility extended community attribute.

Since the best path sequence number is via MES2, it will
continue to send traffic destined for MAC1 to MES1. an unsigned 32 bit integer, all sequence
number comparisons must be performed modulo 2**32. This will not
occur deterministially until MES1 withdraws unsigned
arithmetic preserves the advertisement for
MAC1.

One recommended optimization relationship of sequence numbers as they
cycle from 2**32 - 1 to reduce the traffic loss during 0.

Every MAC
moves mobility event for a given MAC address will contain a
sequence number that is set using the following option. When an MES sees rules:

- A PE advertising a MAC update from address for the first time advertises it
with no MAC Mobility extended community attribute.

- A PE detecting a locally attached CE on an ESI, MAC address for which is it had
previously received a MAC Advertisement route with a different from
Ethernet segment identifier advertises the ESI on
which MAC address in a MAC
Advertisement route tagged with a MAC Mobility extended community
attribute with a sequence number one greater than the MES has currently learned sequence number
in the MAC, MAC mobility attribute of the corresponding entry received MAC Advertisement
route. In the case of the first mobility event for a given MAC
address, where the received MAC Advertisement route does not carry a
MAC Mobility attribute, the value of the sequence number in the local bridge forwarding table SHOULD
received route is assumed to be immediately purged
causing 0 for purpose of this processing.

- A PE detecting a locally attached MAC address for which it had
previously received a MAC Advertisement route with the MES same Ethernet
segment identifier advertises it with:
i. no MAC Mobility extended community attribute, if the received
route did not carry said attribute.

ii. a MAC Mobility extended community attribute with the sequence
number equal to withdraw its own E-VPN the sequence number in the received MAC advertisement
Advertisement route, if the received route is tagged with a MAC
Mobility extended community attribute.

A PE receiving a MAC Advertisement route for a MAC address with a
different Ethernet segment identifier and
replace a higher sequence number
than that which it with had previously advertised, withdraws its MAC
Advertisement route. If two (or more) PEs advertise the update.

A future version of this specification will describe other optimized
procedures to minimize traffic loss during same MAC moves.

20.
address with same sequence number but different Ethernet segment
identifiers, a PE that receives these routes selects the route
advertised by the PE with lowest IP address as the best route.

17. Multicast

The MESes PEs in a particular E-VPN may use ingress replication or P2MP
LSPs to send multicast traffic to other MESes.

20.1. PEs.

17.1. Ingress Replication

The MESes PEs may use ingress replication for flooding unknown unicast,
multicast or broadcast traffic as described in section "Handling of
Multi-Destination Traffic". A given unknown unicast or broadcast
packet must be sent to all the remote MESes. PEs. However a given multicast
packet for a multicast flow may be sent to only a subset of the MESes. PEs.
Specifically a given multicast flow may be sent to only those MESes PEs
that have receivers that are interested in the multicast flow.
Determining which of the MESes PEs have receivers for a given multicast
flow is done using explicit tracking described below.

20.2.

17.2. P2MP LSPs

A MES

An PE may use an "Inclusive" tree for sending an unknown unicast,
broadcast or multicast packet or a "Selective" tree. This terminology
is borrowed from [VPLS-MCAST].

A variety of transport technologies may be used in the SP network.
For inclusive P-Multicast trees, these transport technologies include
point-to-multipoint LSPs created by RSVP-TE or mLDP. For selective P-
Multicast trees, only unicast MES-MES PE-PE tunnels (using MPLS or IP/GRE
encapsulation) and P2MP LSPs are supported, and the supported P2MP
LSP signaling protocols are RSVP-TE, and mLDP.

20.3.

17.3. MP2MP LSPs

The root of the MP2MP LDP LSP advertises the Inclusive Multicast Tag
route with the PMSI Tunnel attribute set to the MP2MP Tunnel
identifier. This advertisement is then sent to all MESes PEs in the E-
VPN. E-VPN.
Upon receiving the Inclusive Multicast Tag routes with a PMSI Tunnel
attribute that contains the MP2MP Tunnel identifier, the receiving MESes
PEs initiate the setup of the MP2MP tunnel towards the root using the
procedures in [MLDP].

20.3.1.

17.3.1. Inclusive Trees

An Inclusive Tree allows the use of a single multicast distribution
tree, referred to as an Inclusive P-Multicast tree, in the SP network
to carry all the multicast traffic from a specified set of E-VPN
instances EVIs on a
given MES. PE. A particular P-Multicast tree can be set up to carry the
traffic originated by sites belonging to a single E-VPN, or to carry
the traffic originated by sites belonging to different E-
VPNs. E-VPNs. The
ability to carry the traffic of more than one E-VPN on the same tree
is termed 'Aggregation'. The tree needs to include every
MES PE that is a
member of any of the E-VPNs that are using the tree. This implies
that an MES PE may receive multicast traffic for a multicast stream even
if it doesn't have any receivers that are interested in receiving
traffic for that stream.

An Inclusive P-Multicast tree as defined in this document is a P2MP
tree. A P2MP tree is used to carry traffic only for E-VPN CEs that
are connected to the MES PE that is the root of the tree.

The procedures for signaling an Inclusive Tree are the same as those
in [VPLS-MCAST] with the VPLS-AD route replaced with the Inclusive
Multicast Ethernet Tag route. The P-Tunnel attribute [VPLS-MCAST] for
an Inclusive tree is advertised in the Inclusive Ethernet A-D Multicast route as
described in section "Handling of Multi-Destination Traffic". Note
that an MES PE can "aggregate" multiple inclusive trees for different E-
VPNs
EVIs on the same P2MP LSP using upstream labels. The procedures for
aggregation are the same as those described in [VPLS-MCAST], with
VPLS A-D routes replaced by E-VPN Inclusive Multicast Ethernet A-D routes.

20.3.2.

17.3.2. Selective Trees

A Selective P-Multicast tree is used by an MES PE to send IP multicast
traffic for one or more specific IP multicast streams, originated by
CEs connected to the MES, PE, that belong to the same or different E-
VPNs, E-VPNs,
to a subset of the MESs PEs that belong to those E-VPNs. Each of the MESs PEs
in the subset should be on the path to a receiver of one or more
multicast streams that are mapped onto the tree. The ability to use
the same tree for multicast streams that belong to different E-
VPNs E-VPNs
is termed an MES PE the ability to create separate SP multicast trees for
specific multicast streams, e.g. high bandwidth multicast streams.
This allows traffic for these multicast streams to reach only those MES
PE routers that have receivers in these streams. This avoids flooding
other MES PE routers in the E-VPN.

An SP can use both Inclusive P-Multicast trees and Selective P-
Multicast trees or either of them for a given E-VPN on an MES, PE, based
on local configuration.

The granularity of a selective tree is <RD, MES, PE, S, G> where S is an
IP multicast source address and G is an IP multicast group address or
G is a multicast MAC address. Wildcard sources and wildcard groups
are supported. Selective trees require explicit tracking as described
below.

A E-VPN MES PE advertises a selective tree using a E-VPN selective A-D
route. The procedures are the same as those in [VPLS-MCAST] with S-
PMSI A-D routes in [VPLS-MCAST] replaced by E-VPN Selective A-D
routes. The information elements of the E-VPN selective A-D route
are similar to those of the VPLS S-PMSI A-D route with the following
differences. A E-VPN Selective A-D route includes an optional
Ethernet Tag field. Also an E-VPN selective A-D route may encode a
MAC address in the Group field. The encoding details of the E-VPN
selective A-D route will be described in the next revision.

Selective trees can also be aggregated on the same P2MP LSP using
aggregation as described in [VPLS-MCAST].

20.4.

17.4. Explicit Tracking

[VPLS-MCAST] describes procedures for explicit tracking that rely on
Leaf A-D routes. The same procedures are used for explicit tracking
in this specification with VPLS Leaf A-D routes replaced with E-VPN
Leaf A-D routes. These procedures allow a root MES PE to request
multicast membership information for a given (S, G), from leaf MESs. PEs.
Leaf MESs PEs rely on IGMP snooping or PIM snooping between the MES PE and the
CE to determine the multicast membership information. Note that the
procedures in [VPLS-MCAST] do not describe how explicit tracking is
performed if the CEs are enabled with join suppression. The
procedures for this case will be described in a future version.

21.

18. Convergence

This section describes failure recovery from different types of
network failures.

21.1.

18.1. Transit Link and Node Failures between MESes PEs

The use of existing MPLS Fast-Reroute mechanisms can provide failure
recovery in the order of 50ms, in the event of transit link and node
failures in the infrastructure that connects the MESes.

21.2. MES PEs.

18.2. PE Failures

Consider a host host1 that is dual homed to MES1 PE1 and MES2. PE2. If MES1 PE1
fails, a remote MES, MES3, PE, PE3, can discover this based on the failure of
the BGP session. This failure detection can be in the sub-second
range if BFD is used to detect BGP session failure. MES3 PE3 can update
its forwarding state to start sending all traffic for host1 to only
MES2.
PE2. It is to be noted that this failure recovery is potentially
faster than what would be possible if data plane learning were to be
used. As in that case MES3 PE3 would have to rely on re-learning of MAC
addresses via MES2.

21.2.1. PE2.

18.2.1. Local Repair
It is possible to perform local repair in the case of MES PE failures.
Details will be specified in the future.

21.3. MES

18.3. PE to CE Network Failures

When an Ethernet segment connected to an MES PE fails or when a Ethernet
Tag is deconfigured decommissioned on an Ethernet segment, then the MES PE MUST
withdraw the Ethernet A-D route(s) announced for the <ESI, Ethernet
Tags> that are impacted by the failure or de-configuration. decommissioning. In
addition
addition, the MES PE MUST also withdraw the MAC advertisement routes that
are impacted by the failure or de-configuration. decommissioning.

The Ethernet A-D routes should be used by an implementation to
optimize the withdrawal of MAC advertisement routes. When an MES PE
receives a withdrawal of a particular Ethernet A-D route from an MES PE
it SHOULD consider all the MAC advertisement routes, that are learned
from the same <ESI, Ethernet Tag> as in the Ethernet A-D route, from
the advertising MES, PE, as having been withdrawn. This optimizes the
network convergence times in the event of MES PE to CE failures.

22.

19. LACP State Synchronization

This section requires review and discussion amongst the authors and
will be revised in the next version.

To support CE multi-homing with multi-chassis Ethernet bundles, the
MESes
PEs connected to a given CE should synchronize [802.1AX] LACP state
amongst each other. This ensures that the MESes PEs can present a single
LACP bundle to the CE. This is required for initial system bring-up
and upon any configuration change.

This includes at least the following LACP specific configuration
parameters:

- System Identifier (MAC Address): uniquely identifies a LACP
speaker.
- System Priority: determines which LACP speaker's port
priorities are used in the Selection logic.
- Aggregator Identifier: uniquely identifies a bundle within
a LACP speaker.
- Aggregator MAC Address: identifies the MAC address of the
bundle.
- Aggregator Key: used to determine which ports can join an
Aggregator.
- Port Number: uniquely identifies an interface within a LACP
speaker.
- Port Key: determines the set of ports that can be bundled.
- Port Priority: determines a port's precedence level to join
a bundle in case the number of eligible ports exceeds the
maximum number of links allowed in a bundle.

Furthermore, the MESes PEs should also synchronize operational (run-time)
data, in order for the LACP Selection logic state-machines to
execute. This operational data includes the following LACP
operational parameters, on a per port basis:

- Partner System Identifier: this is the CE System MAC address.
- Partner System Priority: the CE LACP System Priority
- Partner Port Number: CE's AC port number.
- Partner Port Priority: CE's AC Port Priority.
- Partner Key: CE's key for this AC.
- Partner State: CE's LACP State for the AC.
- Actor State: PE's LACP State for the AC.
- Port State: PE's AC port status.

The above state needs to be communicated between MESes PEs forming a
multi-chassis multi-
chassis bundle during LACP initial bringup, upon any configuration
change and upon the occurrence of a failure.

It should be noted that the above configuration and operational state
is localized in scope and is only relevant to MESes PEs which connect to
the same multi-homed CE over a given Ethernet bundle.

Furthermore, the communication of state changes, upon failures, must
occur with minimal latency, in order to minimize the switchover time
and consequent service disruption. The protocol details for
synchronizing the LACP state will be described in the following
version.

23.

20. Acknowledgements

We would like to thank Yakov Rekhter, Pedro Marques, Kaushik Ghosh,
Nischal Sheth, Robert Raszuk and Raszuk, Amit Shukla and Nadeem Mohammed for
discussions that helped shape this document. We would also like to
thank Han Nguyen for his comments and support of this work. We would
also like to thank Steve Kensil for his review.

24.

21. References
[E-VPN-REQ] A. Sajassi, R. Aggarwal et. al., "Requirements for
Ethernet VPN", draft-sajassi-raggarwa-l2vpn-evpn-req-
00.txt

[RFC4364] "BGP/MPLS IP VPNs", Rosen, Rekhter, et. al., February 2006

[VPLS-MCAST] "Multicast in VPLS". R. Aggarwal et.al., draft-ietf-
l2vpn-vpls-mcast-04.txt

[RFC4761] Kompella, K. and Y. Rekhter, "Virtual Private LAN Service
(VPLS) Using BGP for Auto-Discovery and Signaling", RFC
4761, January 2007.

[RFC4762] Lasserre, M. and V. Kompella, "Virtual Private LAN Service
(VPLS) Using Label Distribution Protocol (LDP) Signaling",
RFC 4762, January 2007.

[VPLS-MULTIHOMING] "BGP based Multi-homing in Virtual Private LAN
Service", K. Kompella et. al., draft-ietf-l2vpn-vpls-
multihoming-00.txt

[PIM-SNOOPING] "PIM Snooping over VPLS", V. Hemige et. al., draft-
ietf-l2vpn-vpls-pim-snooping-01

[IGMP-SNOOPING] "Considerations for Internet Group Management
Protocol (IGMP) and Multicast Listener Discovery (MLD)
Snooping Switches", M. Christensen et. al., RFC4541,

[RT-CONSTRAIN] P. Marques et. al., "Constrained Route Distribution
for Border Gateway Protocol/MultiProtocol Label Switching
(BGP/MPLS) Internet Protocol (IP) Virtual Private Networks
(VPNs)", RFC 4684, November 2006

25.

[EVPN-SEGMENT-ROUTE] A. Sajassi et. al., "E-VPN Ethernet Segment
Route", draft-sajassi-l2vpn-evpn-segment-route-00.txt,
work in progress.

21. Author's Address

Rahul Aggarwal
Email: raggarwa_1@yahoo.com

Ali Sajassi
Cisco
170 West Tasman Drive
San Jose, CA 95134, US
Email: sajassi@cisco.com

Wim Henderickx
Alcatel-Lucent
e-mail: wim.henderickx@alcatel-lucent.com
Aldrin Isaac
Bloomberg
Email: aisaac71@bloomberg.net

James Uttaro
AT&T
200 S. Laurel Avenue
Middletown, NJ 07748
USA
Email: uttaro@att.com

Nabil Bitar
Verizon Communications
Email : nabil.n.bitar@verizon.com

Ravi Shekhar
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089 US
Email: rshekhar@juniper.net

John Drake
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089 US
Email: jdrake@juniper.net

Florin Balus
Alcatel-Lucent
e-mail: Florin.Balus@alcatel-lucent.com

Keyur Patel
Cisco
170 West Tasman Drive
San Jose, CA 95134, US
Email: keyupate@cisco.com

Sami Boutros
Cisco
170 West Tasman Drive
San Jose, CA 95134, US
Email: sboutros@cisco.com

Samer Salam
Cisco
595 Burrard Street, Suite 2123
Vancouver, BC V7X 1J1, Canada
Email: ssalam@cisco.com