draft-ietf-bess-evpn-etree-00.txt   draft-ietf-bess-evpn-etree-01.txt 
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Intended Status: Standards Track Sami Boutros Intended Status: Standards Track Sami Boutros
Cisco Cisco
Wim Henderickx Wim Henderickx
Jorge Rabadan Jim Uttaro Jorge Rabadan Jim Uttaro
Alcatel-Lucent AT&T Alcatel-Lucent AT&T
John Drake Aldrin Isaac John Drake Aldrin Isaac
Wen Lin Bloomberg Wen Lin Bloomberg
Juniper Juniper
Expires: December 10, 2015 June 10, 2015 Expires: December 18, 2015 June 18, 2015
E-TREE Support in EVPN & PBB-EVPN E-TREE Support in EVPN & PBB-EVPN
draft-ietf-bess-evpn-etree-00 draft-ietf-bess-evpn-etree-01
Abstract Abstract
The Metro Ethernet Forum (MEF) has defined a rooted-multipoint The Metro Ethernet Forum (MEF) has defined a rooted-multipoint
Ethernet service known as Ethernet Tree (E-Tree). [ETREE-FMWK] Ethernet service known as Ethernet Tree (E-Tree). [ETREE-FMWK]
proposes a solution framework for supporting this service in MPLS proposes a solution framework for supporting this service in MPLS
networks. This document discusses how those functional requirements networks. This document discusses how those functional requirements
can be easily met with (PBB-)EVPN and how (PBB-)EVPN offers a more can be easily met with (PBB-)EVPN and how (PBB-)EVPN offers a more
efficient implementation of these functions. efficient implementation of these functions.
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(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
2 E-Tree Scenarios and EVPN / PBB-EVPN Support . . . . . . . . . 3 2 E-Tree Scenarios and EVPN / PBB-EVPN Support . . . . . . . . . 4
2.1 Scenario 1: Leaf OR Root site(s) per PE . . . . . . . . . . 3 2.1 Scenario 1: Leaf OR Root site(s) per PE . . . . . . . . . . 4
2.2 Scenario 2: Leaf AND Root site(s) per PE . . . . . . . . . . 4 2.2 Scenario 2: Leaf AND Root site(s) per PE . . . . . . . . . . 5
2.3 Scenario 3: Leaf AND Root site(s) per Ethernet Segment . . . 4 2.3 Scenario 3: Leaf AND Root site(s) per Ethernet Segment . . . 5
3 Operation for EVPN . . . . . . . . . . . . . . . . . . . . . . . 5 3 Operation for EVPN . . . . . . . . . . . . . . . . . . . . . . . 6
3.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 5 3.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 7
3.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3 E-TREE Traffic Flows for EVPN . . . . . . . . . . . . . . . 8 3.2.1 BUM Traffic supported by P2MP Tunnels . . . . . . . . . 7
3.3.1 E-Tree with MAC Learning . . . . . . . . . . . . . . . . 8 3.2.1 BUM Traffic supported by Ingress Replication . . . . . . 9
3.3.2 E-Tree without MAC Learning . . . . . . . . . . . . . . 9 3.3 E-TREE Traffic Flows for EVPN . . . . . . . . . . . . . . . 10
4 Operation for PBB-EVPN . . . . . . . . . . . . . . . . . . . . . 9 3.3.1 E-Tree with MAC Learning . . . . . . . . . . . . . . . . 11
4.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 9 3.3.2 E-Tree without MAC Learning . . . . . . . . . . . . . . 11
4.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 10 4 Operation for PBB-EVPN . . . . . . . . . . . . . . . . . . . . . 12
5 Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . 10 4.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 12
6 Security Considerations . . . . . . . . . . . . . . . . . . . . 10 4.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 13
7 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 10 5 BGP Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 13
8 References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 5.1 E-TREE Extended Community . . . . . . . . . . . . . . . . . 13
8.1 Normative References . . . . . . . . . . . . . . . . . . . 10 6 Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . 14
8.2 Informative References . . . . . . . . . . . . . . . . . . 11 7 Security Considerations . . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 8 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 14
9 References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1 Normative References . . . . . . . . . . . . . . . . . . . 14
9.2 Informative References . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
1 Introduction 1 Introduction
The Metro Ethernet Forum (MEF) has defined a rooted-multipoint The Metro Ethernet Forum (MEF) has defined a rooted-multipoint
Ethernet service known as Ethernet Tree (E-Tree). In an E-Tree Ethernet service known as Ethernet Tree (E-Tree). In an E-Tree
service, endpoints are labeled as either Root or Leaf sites. Root service, endpoints are labeled as either Root or Leaf sites. Root
sites can communicate with all other sites. Leaf sites can sites can communicate with all other sites. Leaf sites can
communicate with Root sites but not with other Leaf sites. communicate with Root sites but not with other Leaf sites.
[ETREE-FMWK] proposes the solution framework for supporting E-Tree [ETREE-FMWK] proposes the solution framework for supporting E-Tree
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3 Operation for EVPN 3 Operation for EVPN
[EVPN] defines the notion of an Ethernet Segment which can be readily [EVPN] defines the notion of an Ethernet Segment which can be readily
used to identify a Root and/or Leaf site in E-TREE services. In other used to identify a Root and/or Leaf site in E-TREE services. In other
words, [EVPN] has inherent capability to support E-TREE services words, [EVPN] has inherent capability to support E-TREE services
without defining any new BGP routes. It only requires a minor without defining any new BGP routes. It only requires a minor
modification to the existing procedures and a new BGP Extended modification to the existing procedures and a new BGP Extended
Community for leaf indication as shown later in this document. Community for leaf indication as shown later in this document.
In addition to the procedures below (which is a MUST requirement), an
EVPN PE implementation MAY provide topology constraint among the PEs
belonging to the same EVI associated with an E-TREE service. The
purpose of this topology constraint is to avoid having PEs with only
Leaf sites (e.g., scenario 1 in section 2.1) importing and processing
BGP MAC routes from each other, thereby unnecessarily exhausting
their RIB tables. However, when a Root site is added to a Leaf PE
(e.g., scenario 2 and 3 in sections 2.2 and 2.3), then that PE needs
to process MAC routes from all other Leaf PEs and add them to its
forwarding table. To support such topology constrain in EVPN, two BGP
Route-Targets (RTs) are used for every EVPN Instance (EVI): one RT is
associated with the Root sites and the other is associated with the
Leaf sites. On a per EVI basis, every PE exports the single RT
associated with its type of site(s). Furthermore, a PE with Root
site(s) imports both Root and Leaf RTs, whereas a PE with Leaf
site(s) only imports the Root RT. If for a given EVI, the PEs can
eventually have both Leaf and Root sites attached, even though they
may start as Root-only or Leaf-only PEs, then it is recommended to
use a single RT per EVI and avoid additional configuration and
operational overhead. If the number of EVIs is very large (e.g., more
than 32K or 64K), then RT type 0 as defined in [RFC4360] SHOULD be
used; otherwise, RT type 2 is sufficient.
The following procedures are used consistently for all the scenarios The following procedures are used consistently for all the scenarios
highlighted in the previous section. highlighted in the previous section.
3.1 Known Unicast Traffic 3.1 Known Unicast Traffic
For known unicast traffic, the PE must advertise a Leaf indication For known unicast traffic, the PE must advertise a Leaf indication
along with each MAC Advertisement route, to indicate that the along with each MAC Advertisement route, to indicate that the
associated MAC address was learnt from a Leaf Attachment Circuit associated MAC address was learnt from a Leaf Attachment Circuit
(AC). The lack of a Leaf indication, indicates the MAC address is (AC). The lack of a Leaf indication, indicates the MAC address is
learnt from a root AC. In other words, a default mode of operation learnt from a root AC. In other words, the default mode of operation
in an EVPN is that all ACs are root (can transmit and receive traffic in an EVPN is that all ACs are root (can transmit and receive traffic
to/from other ACs in an EVI) unless the AC is explicitly identified to/from other ACs in an EVI) unless the AC is explicitly identified
as a leaf. as a leaf.
Tagging MAC addresses with a leaf indication when they are associated Tagging MAC addresses with a leaf indication when they are associated
with a leaf AC, enables remote PEs to perform ingress filtering for with a leaf AC, enables remote PEs to perform ingress filtering for
known unicast traffic - i.e., on the ingress PE, the MAC destination known unicast traffic - i.e., on the ingress PE, the MAC destination
address lookup yields, in addition to the forwarding adjacency, a address lookup yields, in addition to the forwarding adjacency, a
flag which indicates whether the target MAC is associated with a Leaf flag which indicates whether the target MAC is associated with a Leaf
site or not. The ingress PE cross-checks this flag with the status of site or not. The ingress PE cross-checks this flag with the status of
the originating AC, and if both are a Leaf, then the packet is not the originating AC, and if both are Leafs, then the packet is not
forwarded. forwarded.
The PE places all Leaf Ethernet Segments (ACs) of a given bridge The PE places all Leaf ACs of a given bridge domain in a single
domain in a single split-horizon group in order to prevent intra-PE split-horizon group in order to prevent intra-PE forwarding among
forwarding among Leaf ACs (segments). This split-horizon function Leaf ACs. This split-horizon function applies to both known unicast
applies to BUM traffic as well. and BUM traffic.
To support the above ingress filtering functionality, a new Extended To support the above ingress filtering functionality, a new E-TREE
Community with a Leaf indication flag will be introduced [section Extended Community with a Leaf indication flag is introduced [section
xxx]. This new Extended Community will be advertised with each EVPN 5.1]. This new Extended Community is advertised with each EVPN MAC/IP
MAC/IP Advertisement route. Advertisement route.
3.2 BUM Traffic 3.2 BUM Traffic
For BUM traffic, it is not possible to perform filtering on the For BUM traffic, it is not possible to perform filtering on the
ingress PE, as is the case with known unicast, because of the multi- ingress PE, as is the case with known unicast, because of the multi-
destination nature of the traffic. As such, the solution relies on destination nature of the traffic. As such, the solution relies on
egress filtering. In order to apply the proper egress filtering, egress filtering. In order to apply the proper egress filtering,
which varies based on whether a packet is sent from a Root or a Leaf, which varies based on whether a packet is sent from a Root or a Leaf
the MPLS-encapsulated frames MUST be tagged with an indication of AC, the MPLS-encapsulated frames MUST be tagged with an indication of
whether they originated from a Root or a Leaf Ethernet Segment. This whether they originated from a Root or a Leaf AC. This can be
can be achieved in EVPN through the use of the ESI MPLS label, since achieved in EVPN through the use of the ESI MPLS label. Therefore,
this label identifies the Ethernet Segment of origin for a given the ESI MPLS label not only identifies the Ethernet segment of origin
frame. for a given frame, but also it identifies its type (e.g., Leaf or
Root).
3.2.1 BUM Traffic supported by P2MP Tunnels
For multi-homing use cases where BUM traffic uses P2MP LSP, the For multi-homing use cases where BUM traffic uses P2MP LSP, the
egress PE can determine whether or not to forward a particular frame ingress PE adds an upstream-assigned ESI MPLS label to the frame per
to an Ethernet Segment depending on the split-horizon rule defined in
[EVPN]:
- If the ESI Label indicates that the source Ethernet Segment is a [RFC7432] procedures and sends it to all the intended ingress PE
Root, then the frame can be forwarded on a segment granted that it devices. Two ESI MPLS labels are used for each multi-homed Ethernet
passes the split-horizon check. segment that has both Root and Leaf sites: one ESI MPLS label that
only identifies the Ethernet segment of origin per [RFC7432] and
another one that not only identifies the Ethernet segment of origin
but also its type (which is Leaf). If an Ethernet segment has only
Root sites, then the former ESI MPLS label is used and if an Ethernet
segment has only Leaf sites, then the latter ESI MPLS label is used.
- If the ESI Label indicates that the source Ethernet Segment is a It should be noted that the former ESI MPLS label implicitly
Leaf, then the frame can be forwarded only on a Root segment, granted identifies a Root Ethernet segment - i.e., an ESI MPLS label that is
that it passes the split-horizon check. signaled without the new E-TREE Extended Community (defined in
section [5.1]), is assumed to be of type Root. When advertising the
ESI MPLS label for an Ethernet Segment that has Leaf sites, the PE
MUST indicate that the corresponding ESI is of type Leaf. This is
achieved by advertising the Ethernet A-D per ES route with with the
ESI MPLS label Extended Community along with the new E-TREE Extended
Community that has a Leaf indication flag.
When advertising the ESI MPLS label for a given Ethernet Segment, a The egress PE can determine whether or not to forward a particular
PE must indicate whether the corresponding ESI is a Root or a Leaf frame to the destination Ethernet Segment depending on the following
site. This can be achieved by advertising the Ethernet A-D per ES rules:
route with with the ESI MPLS label Extended Community along with the
new Extended Community defined in section [xxx] that has a Leaf
indication flag.
In the case where a multi-homed Ethernet Segment has both Root and - If the ESI MPLS label indicates that the source Ethernet Segment is
Leaf sites attached, two ESI MPLS labels are allocated and the same as destination Ethernet segment, then the frame is blocked
advertised: one default ESI MPLS label that denotes Root and another according to the split-horizon rule in [RFC7432].
ESI MPLS label with Leaf indication that denotes Leaf. The ingress PE
imposes the right ESI MPLS label depending on whether the Ethernet
frame originated from the Root or Leaf site on that Ethernet Segment.
The mechanism by which the PE identifies whether a given frame
originated from a Root or Leaf site on the segment is based on the
Ethernet Tag associated with the frame (e.g., whether the frame come
from a leaf or a root AC). Other mechanisms of identification, beyond
the Ethernet Tag, are outside the scope of this document. It should
be noted that support for both Root and Leaf sites on a single
Ethernet Segment requires that the PE performs the Ethernet Segment
split-horizon check on a per Ethernet Tag basis. In the case where a
multi-homed Ethernet Segment has only either Root or Leaf sites
attached, then a single ESI MPL label is allocated and advertised.
Furthermore, a PE advertises a special per-PE Leaf MPLS label to - If the ESI MPLS label indicates that the source Ethernet Segment is
indicate Leaf. For traffic originated from single-homed segments, not the same as destination Ethernet segment and it doesn't have any
this label can be either upstream assigned or downstream assigned Leaf indication, then the frame is forwarded to the destination AC
(depending on whether BUM traffic uses P2MP LSP or ingress according to the split-horizon rule in [RFC7432].
replication). However, for traffic originated from multi-homed
segments, this label is downstream assigned as ingress replication is
assumed to be used for BUM traffic. Furthermore, this label is used
for traffic originating from a multi-homed segments that are not part
of the same redundancy group (same ES) as the advertising PE. This
label indicates to the egress PE that the BUM traffic is originated
from a Leaf AC. Note that this special label is advertised on a per
PE basis (i.e. each PE advertises only a single such special label).
It should be noted that this per-PE Leaf label is not used for multi-
homed segments when P2MP LSP is used for BUM traffic or when ingress
replication is destined to a PE that shares the same multi-homed ES -
i.e., in such scenarios, the color-coded per-ES ESI MPLS label is
used (indicating leaf or root).
This per-PE Leaf MPLS label is advertised along with the Leaf - If the ESI MPLS label indicates that the source Ethernet Segment is
indication flag with the Ethernet A-D per ES route. not the same as destination Ethernet segment but it has a Leaf
indication, then the frame is blocked if the destination AC is of
type Leaf and it is forwarded if the destination AC is of type Root.
In addition to egress filtering (which is a MUST requirement), an The ingress PE imposes the right ESI MPLS label depending on whether
EVPN PE implementation MAY provide topology constraint among the PEs the Ethernet frame originated from the Root or Leaf site on that
belonging to the same EVI associated with an E-TREE service. The Ethernet Segment. The mechanism by which the PE identifies whether a
purpose of this topology constraint is to avoid having PEs with only given frame originated from a Root or Leaf site on the segment is
host Leaf sites importing and processing BGP MAC routes from each based on the Ethernet Tag associated with the frame (e.g., whether
other, thereby unnecessarily exhausting their RIB tables. However, the frame come from a leaf or a root AC). Other mechanisms of
when a Root site is added to a Leaf PE, then that PE needs to process identification, beyond the Ethernet Tag, are outside the scope of
MAC routes from all other Leaf PEs and add them to its forwarding this document. It should be noted that support for both Root and Leaf
table. To support such topology constrain in EVPN, two BGP Route- sites on a single Ethernet Segment requires that the PE performs the
Targets (RTs) are used for every EVPN Instance (EVI): one RT is Ethernet Segment split-horizon check on a per Ethernet Tag basis. In
associated with the Root sites and the other is associated with the the case where a multi-homed Ethernet Segment has only either Root or
Leaf sites. On a per EVI basis, every PE exports the single RT Leaf sites attached, then a single ESI MPL label is allocated and
associated with its type of site(s). Furthermore, a PE with Root advertised.
site(s) imports both Root and Leaf RTs, whereas a PE with Leaf
site(s) only imports the Root RT. If for a given EVI, the PEs can For single-homing use cases where BUM traffic uses P2MP LSP, the
eventually have both Leaf and Root sites attached, even though they ingress PE adds a special ESI MPLS label to the frame if the frame is
may start as Root-only or Leaf-only PEs, then it is recommended to originated from a Leaf site. This special ESI MPLS label used for
use a single RT per EVI and avoid additional configuration and single-homing scenarios is not on a per ES basis but rather on a per
operational overhead. If the number of EVIs is very large (e.g., more PE basis - i.e., a single ESI MPLS label is used for all single-homed
than 32K or 64K), then RT type 0 as defined in [RFC4360] SHOULD be segments on that PE. If the frame is originated from a Root site,
used; otherwise, RT type 2 is sufficient. then the ingress PE does not add any ESI MPLS label per [RFC7432]
procedures. The egress PE, when receiving this special ESI MPLS
label, it blocks the frame if the destination AC is of type Leaf and
it forwards the frame if the destination AC is of type Root.
When a PE wants to advertise this special ESI label to other PE
devices, it advertises it using ESI MPLS label Extended Community
with the Ethernet A-D per ES route. The ESI for the Ethernet A-D per
ES route, can be of type 3, 4, or 5.
3.2.1 BUM Traffic supported by Ingress Replication
The procedures for supporting BUM traffic using ingress replication,
are similar to the ones in the previous section. The main differences
are that the ESI label is downstream assigned and not all egress PE
devices need to receive the ESI label just like ingress replication
procedures defined in [RFC7432].
For frames received from a multi-homed Ethernet segment, the ingress
PE may or may not add an ESI MPLS label based on the following
criteria:
- If the frame is forwarded to a PE that participates in the same
multi-homed Ethernet Segment and the frame is received on a Root AC,
then the ingress PE adds a per-ES downstream-assigned ESI MPLS label
to the frame per [RFC7432].
- If the frame is forwarded to a PE that participates in the same
multi-homed Ethernet Segment and the frame is received on a Leaf AC,
then the ingress PE adds the a per-ES downstream-assigned ESI MPLS
label indicating Leaf to the frame.
- If the frame is forwarded to a PE that does not participate in the
same multi-homed Ethernet Segment and the frame is received on a Leaf
AC, then the ingress PE adds a per-PE downstream-assigned special ESI
MPLS label indicating Leaf to the frame. This special ESI MPLS label
is per PE.
- If the frame is forwarded to a PE that does not participate in the
same multi-homed Ethernet Segment and the frame is received on a Root
AC, then the ingress PE does not add any ESI MPLS label to the frame
per [RFC7432].
For frames received from a single-homed Ethernet segment, the ingress
PE may or may not add an ESI MPLS label based on the following
criteria:
- If the frame is received on a Root AC, then the ingress PE does not
add any ESI MPLS label to the frame.
- If the frame is received on a Leaf AC, then the ingress PE adds a
special downstream-assigned ESI MPLS label indicating Leaf to the
frame.
Just as described in the previous section, the Leaf indication is
signaled using the new E-TREE extended community defined in section
[5.1] along with the ESI MPLS label extended community with the
Ethernet A-D per ES route.
The egress PE can determine whether or not to forward a particular
frame to the desitnation Ethernet Segment depending on the following
rules:
- If the ESI MPLS label indicates that the source Ethernet Segment is
the same as destination Ethernet segment, then the frame is blocked
according to the split-horizon rule in [RFC7432].
- If the ESI MPLS label indicates that the source Ethernet Segment is
not the same as destination Ethernet segment and it doesn't have any
Leaf indication, then the frame is forwarded to the destination AC
according to the split-horizon rule in [RFC7432].
- If the ESI MPLS label indicates that the source Ethernet Segment is
not the same as destination Ethernet segment but it has a Leaf
indication, then the frame is blocked if the destination AC is of
type Leaf and it is forwarded if the destination AC is of type Root.
- If the ESI label is a special ESI MPLS label, then the frame is
blocked if the destination AC is of type Leaf and it is forwarded if
the destination AC is of type Root.
3.3 E-TREE Traffic Flows for EVPN 3.3 E-TREE Traffic Flows for EVPN
Per [ETREE-FMWK], a generic E-Tree service supports all of the Per [ETREE-FMWK], a generic E-Tree service supports all of the
following traffic flows: following traffic flows:
- Ethernet Unicast from Root to Roots & Leaf - Ethernet Unicast from Root to Roots & Leaf
- Ethernet Unicast from Leaf to Root - Ethernet Unicast from Leaf to Root
- Ethernet Broadcast/Multicast from Root to Roots & Leafs - Ethernet Broadcast/Multicast from Root to Roots & Leafs
- Ethernet Broadcast/Multicast from Leaf to Roots - Ethernet Broadcast/Multicast from Leaf to Roots
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learning in the data-path over their Ethernet Segments, and advertise learning in the data-path over their Ethernet Segments, and advertise
reachability in EVPN MAC Advertisement routes which are imported only reachability in EVPN MAC Advertisement routes which are imported only
by PEs with at least one Root site in the EVI. A PE with only Leaf by PEs with at least one Root site in the EVI. A PE with only Leaf
sites will not import these routes. PEs with Root and/or Leaf sites sites will not import these routes. PEs with Root and/or Leaf sites
may use the Ethernet A-D routes for aliasing (in the case of multi- may use the Ethernet A-D routes for aliasing (in the case of multi-
homed segments) and for mass MAC withdrawal. homed segments) and for mass MAC withdrawal.
To support multicast/broadcast from Root to Leaf sites, either a P2MP To support multicast/broadcast from Root to Leaf sites, either a P2MP
tree rooted at the PE(s) with the Root site(s) or ingress replication tree rooted at the PE(s) with the Root site(s) or ingress replication
can be used. The multicast tunnels are set up through the exchange of can be used. The multicast tunnels are set up through the exchange of
the EVPN Inclusive Multicast route, as defined in [EVPN]. the EVPN Inclusive Multicast route, as defined in [RFC7432].
To support multicast/broadcast from Leaf to Root sites, ingress To support multicast/broadcast from Leaf to Root sites, ingress
replication should be sufficient for most scenarios where there is a replication should be sufficient for most scenarios where there is a
single Root or few Roots. If the number of Roots is large, a P2MP single Root or few Roots. If the number of Roots is large, a P2MP
tree rooted at the PEs with Leaf sites may be used. tree rooted at the PEs with Leaf sites may be used.
3.3.2 E-Tree without MAC Learning 3.3.2 E-Tree without MAC Learning
The PEs implementing an E-Tree service need not perform MAC learning The PEs implementing an E-Tree service need not perform MAC learning
when the traffic flows between Root and Leaf sites are multicast or when the traffic flows between Root and Leaf sites are multicast or
broadcast. In this case, the PEs do not exchange EVPN MAC broadcast. In this case, the PEs do not exchange EVPN MAC
Advertisement routes. Instead, the Ethernet A-D routes are used to Advertisement routes. Instead, the Ethernet A-D routes are used to
exchange the EVPN labels. exchange the EVPN labels.
The fields of the Ethernet A-D route are populated per the procedures The fields of the Ethernet A-D route are populated per the procedures
defined in [EVPN], and the route import rules are as described in defined in [RFC7432], and the route import rules are as described in
previous sections. previous sections.
4 Operation for PBB-EVPN 4 Operation for PBB-EVPN
In PBB-EVPN, the PE must advertise a Root/Leaf indication along with In PBB-EVPN, the PE must advertise a Root/Leaf indication along with
each MAC Advertisement route, to indicate whether the associated B- each MAC Advertisement route, to indicate whether the associated B-
MAC address corresponds to a Root or a Leaf site. Similar to the EVPN MAC address corresponds to a Root or a Leaf site. Similar to the EVPN
case, this flag will be added to the Tunnel Encapsulation Type case, this flag will be added to the new E-TREE extended community
Extended Community [RFC5512], and advertised with each MAC defined in section [5.1], and advertised with each MAC Advertisement
Advertisement route. route.
In the case where a multi-homed Ethernet Segment has both Root and In the case where a multi-homed Ethernet Segment has both Root and
Leaf sites attached, two B-MAC addresses are allocated and Leaf sites attached, two B-MAC addresses are allocated and
advertised: one B-MAC address denotes Root and the other denotes advertised: one B-MAC address implicitly denoting Root and the other
Leaf. The ingress PE uses the right B-MAC source address depending on explicitly denoting Leaf. The former B-MAC address is not advertised
with the E-TREE extended community but the latter B-MAC denoting Leaf
is advertised with the new E-TREE extended community.
The ingress PE uses the right B-MAC source address depending on
whether the Ethernet frame originated from the Root or Leaf site on whether the Ethernet frame originated from the Root or Leaf site on
that Ethernet Segment. The mechanism by which the PE identifies that Ethernet Segment. The mechanism by which the PE identifies
whether a given frame originated from a Root or Leaf site on the whether a given frame originated from a Root or Leaf site on the
segment is based on the Ethernet Tag associated with the frame. Other segment is based on the Ethernet Tag associated with the frame. Other
mechanisms of identification, beyond the Ethernet Tag, are outside mechanisms of identification, beyond the Ethernet Tag, are outside
the scope of this document. It should be noted that support for both the scope of this document. It should be noted that support for both
Root and Leaf sites on a single Ethernet Segment requires that the PE Root and Leaf sites on a single Ethernet Segment requires that the PE
performs the Ethernet Segment split-horizon check on a per Ethernet performs the Ethernet Segment split-horizon check on a per Ethernet
Tag basis. In the case where a multi-homed Ethernet Segment has Tag basis.
either Root or Leaf sites attached, then a single B-MAC address is
allocated and advertised per segment.
Furthermore, a PE advertises two global B-MAC addresses: one for Root In the case where a multi-homed Ethernet Segment has only Root or
and another for Leaf, and tags them as such in the MAC Advertisement Leaf sites attached, then a single B-MAC address is allocated and
routes. These B-MAC addresses are used as source addresses for advertised per segment.
traffic originating from single-homed segments.
Furthermore, a PE advertises two special global B-MAC addresses: one
for Root and another for Leaf, and tags them as such in the MAC
Advertisement routes. These B-MAC addresses are used as source
addresses for traffic originating from single-homed segments.
4.1 Known Unicast Traffic 4.1 Known Unicast Traffic
For known unicast traffic, the PEs perform ingress filtering: On the For known unicast traffic, the PEs perform ingress filtering: On the
ingress PE, the C-MAC destination address lookup yields, in addition ingress PE, the C-MAC destination address lookup yields, in addition
to the target B-MAC address and forwarding adjacency, a flag which to the target B-MAC address and forwarding adjacency, a flag which
indicates whether the target B-MAC is associated with a Root or a indicates whether the target B-MAC is associated with a Root or a
Leaf site. The ingress PE cross-checks this flag with the status of Leaf site. The ingress PE cross-checks this flag with the status of
the originating site, and if both are a Leaf, then the packet is not the originating site, and if both are a Leaf, then the packet is not
forwarded. forwarded.
skipping to change at page 10, line 33 skipping to change at page 13, line 29
is a Leaf, and the local Ethernet Segment is a Leaf as well, then the is a Leaf, and the local Ethernet Segment is a Leaf as well, then the
source B-MAC address is added to the B-MAC filtering list. source B-MAC address is added to the B-MAC filtering list.
- Otherwise, the B-MAC filtering list is not updated. - Otherwise, the B-MAC filtering list is not updated.
When the egress PE receives the packet, it examines the B-MAC source When the egress PE receives the packet, it examines the B-MAC source
address to check whether it should filter or forward the frame. Note address to check whether it should filter or forward the frame. Note
that this uses the same filtering logic as baseline [PBB-EVPN] and that this uses the same filtering logic as baseline [PBB-EVPN] and
does not require any additional flags in the data-plane. does not require any additional flags in the data-plane.
5 Acknowledgement 5 BGP Encoding
We would like to thank Sami Boutros and Dennis Cai for their This document defines one new BGP Extended Community for EVPN.
comments.
6 Security Considerations 5.1 E-TREE Extended Community
Same security considerations as [EVPN]. A new EVPN BGP Extended Community called E-TREE is introduced here.
This new extended community is a transitive extended community with
the Type field of 0x06 (EVPN) and the Sub-Type of 0x04. This extended
community is used to for leaf indication and it is advertised with an
EVPN MAC/IP route or an Ethernet A-D per ES route. When advertised
with an Ethernet A-D per ES route, it is sent along with ESI Label
Extended Community defined in section 7.5 of [RFC7432].
7 IANA Considerations The E-TREE Extended Community is encoded as an 8-octet value as
follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=0x06 | Sub-Type=0x04 | E-TREE Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| E-TREE Flags L|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Leaf flag (L): A value of 1 indicates a leaf
6 Acknowledgement
We would like to thank Dennis Cai for his comments.
7 Security Considerations
Same security considerations as [RFC7432].
8 IANA Considerations
Allocation of Extended Community Type and Sub-Type for EVPN. Allocation of Extended Community Type and Sub-Type for EVPN.
8 References 9 References
8.1 Normative References 9.1 Normative References
[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4360] S. Sangli et al, ""BGP Extended Communities Attribute", [RFC4360] S. Sangli et al, ""BGP Extended Communities Attribute",
February, 2006. February, 2006.
[RFC5512] Mohapatra, P. and E. Rosen, "The BGP [RFC7432] Sajassi et al., "BGP MPLS Based Ethernet VPN", February,
Encapsulation Subsequent Address Family Identifier (SAFI) 2015.
and the BGP Tunnel Encapsulation Attribute", RFC 5512,
April 2009.
8.2 Informative References 9.2 Informative References
[ETREE-FMWK] Key et al., "A Framework for E-Tree Service over MPLS [ETREE-FMWK] Key et al., "A Framework for E-Tree Service over MPLS
Network", draft-ietf-l2vpn-etree-frwk-03, work in progress, September Network", draft-ietf-l2vpn-etree-frwk-03, work in progress, September
2013. 2013.
[EVPN] Sajassi et al., "BGP MPLS Based Ethernet VPN", draft-ietf-
l2vpn-evpn-04.txt, work in progress, July, 2013.
[PBB-EVPN] Sajassi et al., "PBB-EVPN", draft-ietf-l2vpn-pbb-evpn- [PBB-EVPN] Sajassi et al., "PBB-EVPN", draft-ietf-l2vpn-pbb-evpn-
05.txt, work in progress, October, 2013. 05.txt, work in progress, October, 2013.
Authors' Addresses Authors' Addresses
Ali Sajassi Ali Sajassi
Cisco Cisco
Email: sajassi@cisco.com Email: sajassi@cisco.com
Samer Salam Samer Salam
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