draft-ietf-bess-evpn-etree-01.txt   draft-ietf-bess-evpn-etree-02.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 18, 2015 June 18, 2015 Expires: January 6, 2015 July 6, 2015
E-TREE Support in EVPN & PBB-EVPN E-TREE Support in EVPN & PBB-EVPN
draft-ietf-bess-evpn-etree-01 draft-ietf-bess-evpn-etree-02
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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include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
2 E-Tree Scenarios and EVPN / PBB-EVPN Support . . . . . . . . . 4 2 E-Tree Scenarios and EVPN / PBB-EVPN Support . . . . . . . . . 4
2.1 Scenario 1: Leaf OR Root site(s) per PE . . . . . . . . . . 4 2.1 Scenario 1: Leaf OR Root site(s) per PE . . . . . . . . . . 4
2.2 Scenario 2: Leaf AND Root site(s) per PE . . . . . . . . . . 5 2.2 Scenario 2: Leaf OR Root site(s) per AC . . . . . . . . . . 5
2.3 Scenario 3: Leaf AND Root site(s) per Ethernet Segment . . . 5 2.3 Scenario 3: Leaf OR Root site(s) per MAC . . . . . . . . . . 6
3 Operation for EVPN . . . . . . . . . . . . . . . . . . . . . . . 6 3 Operation for EVPN . . . . . . . . . . . . . . . . . . . . . . . 7
3.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 7 3.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 7
3.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 7 3.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2.1 BUM Traffic supported by P2MP Tunnels . . . . . . . . . 7 3.2.1 BUM traffic originated from a single-homed site on a
3.2.1 BUM Traffic supported by Ingress Replication . . . . . . 9 leaf AC . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2.2 BUM traffic originated from a single-homed site on a
root AC . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2.3 BUM traffic originated from a multi-homed site on a
leaf AC . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2.4 BUM traffic originated from a multi-homed site on a
root AC . . . . . . . . . . . . . . . . . . . . . . . . 10
3.3 E-TREE Traffic Flows for EVPN . . . . . . . . . . . . . . . 10 3.3 E-TREE Traffic Flows for EVPN . . . . . . . . . . . . . . . 10
3.3.1 E-Tree with MAC Learning . . . . . . . . . . . . . . . . 11 3.3.1 E-Tree with MAC Learning . . . . . . . . . . . . . . . . 10
3.3.2 E-Tree without MAC Learning . . . . . . . . . . . . . . 11 3.3.2 E-Tree without MAC Learning . . . . . . . . . . . . . . 11
4 Operation for PBB-EVPN . . . . . . . . . . . . . . . . . . . . . 12 4 Operation for PBB-EVPN . . . . . . . . . . . . . . . . . . . . . 11
4.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 12 4.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 12
4.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 13 4.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 12
5 BGP Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5 BGP Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.1 E-TREE Extended Community . . . . . . . . . . . . . . . . . 13 5.1 Leaf ESI Label Extended Community . . . . . . . . . . . . . 13
5.2 E-TREE Extended Community . . . . . . . . . . . . . . . . . 13
6 Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . 14 6 Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . 14
7 Security Considerations . . . . . . . . . . . . . . . . . . . . 14 7 Security Considerations . . . . . . . . . . . . . . . . . . . . 14
8 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 14 8 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 14
9 References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 9 References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1 Normative References . . . . . . . . . . . . . . . . . . . 14 9.1 Normative References . . . . . . . . . . . . . . . . . . . 14
9.2 Informative References . . . . . . . . . . . . . . . . . . 14 9.2 Informative References . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
1 Introduction 1 Introduction
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(Root/Leaf) per PE or per Ethernet Segment: (Root/Leaf) per PE or per Ethernet Segment:
- Leaf OR Root site(s) per PE - Leaf OR Root site(s) per PE
- Leaf AND Root site(s) per PE - Leaf AND Root site(s) per PE
- Leaf AND Root site(s) per Ethernet Segment - Leaf AND Root site(s) per Ethernet Segment
2.1 Scenario 1: Leaf OR Root site(s) per PE 2.1 Scenario 1: Leaf OR Root site(s) per PE
In this scenario, a PE may have Root sites OR Leaf sites for a given In this scenario, a PE may receive traffic from either Root sites OR
VPN instance, but not both concurrently. The PE may have both Root Leaf sites for a given MAC-VRF/bridge table, but not both
and Leaf sites albeit for different VPNs. Every Ethernet Segment concurrently. In other words, a given MAC-VRF/bridge table on a PE is
connected to the PE is uniquely identified as either a Root or a Leaf either associated with a root or leaf. The PE may have both Root and
site. Leaf sites albeit for different MAC-VRFs/bridge tables.
+---------+ +---------+ +---------+ +---------+
| PE1 | | PE2 | | PE1 | | PE2 |
+---+ | +---+ | +------+ | +---+ | +---+ +---+ | +---+ | +------+ | +---+ | +---+
|CE1+-----ES1----+--+ | | | MPLS | | | +--+----ES2-----+CE2| |CE1+---ES1----+--+ | | | MPLS | | | +--+----ES2-----+CE2|
+---+ (Root) | | E | | | /IP | | | E | | (Leaf) +---+ +---+ (Root) | |MAC| | | /IP | | |MAC| | (Leaf) +---+
| | V | | | | | | V | | | |VRF| | | | | |VRF| |
| | I | | | | | | I | | +---+ | | | | | | | | | | +---+
| | | | | | | | +--+----ES3-----+CE3| | | | | | | | | +--+----ES3-----+CE3|
| +---+ | +------+ | +---+ | (Leaf) +---+ | +---+ | +------+ | +---+ | (Leaf) +---+
+---------+ +---------+ +---------+ +---------+
Figure 1: Scenario 1 Figure 1: Scenario 1
2.2 Scenario 2: Leaf AND Root site(s) per PE In such scenario, 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 importing and processing BGP MAC
routes from each other, thereby unnecessarily exhausting their RIB
tables. 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 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.
In this scenario, a PE may have a set of one or more Root sites AND a 2.2 Scenario 2: Leaf OR Root site(s) per AC
set of one or more Leaf sites for a given VPN instance. Every
Ethernet Segment connected to the PE is uniquely identified as either In this scenario, a PE may receive traffic from either Root OR Leaf
a Root or a Leaf site. sites on a given Attachment Circuit (AC) of a MAC-VRF/bridge table.
In other words, an AC (ES or ES/VLAN) is either associated with a
Root or Leaf (but not both).
+---------+ +---------+ +---------+ +---------+
| PE1 | | PE2 | | PE1 | | PE2 |
+---+ | +---+ | +------+ | +---+ | +---+ +---+ | +---+ | +------+ | +---+ | +---+
|CE1+-----ES1----+--+ | | | | | | +--+----ES2-----+CE2| |CE1+-----ES1----+--+ | | | | | | +--+---ES2/AC1--+CE2|
+---+ (Leaf) | | E | | | MPLS | | | E | | (Leaf) +---+ +---+ (Leaf) | |MAC| | | MPLS | | |MAC| | (Leaf) +---+
| | V | | | /IP | | | V | | | |VRF| | | /IP | | |VRF| |
| | I | | | | | | I | | +---+ | | | | | | | | | | +---+
| | | | | | | | +--+----ES3-----+CE3| | | | | | | | | +--+---ES2/AC2--+CE3|
| +---+ | +------+ | +---+ | (Root) +---+ | +---+ | +------+ | +---+ | (Root) +---+
+---------+ +---------+ +---------+ +---------+
Figure 2: Scenario 2 Figure 2: Scenario 2
2.3 Scenario 3: Leaf AND Root site(s) per Ethernet Segment In this scenario, if there are PEs with only root (or leaf) sites per
EVI, then the RT constrain procedures described in section 2.1 can
also be used here. However, when a Root site is added to a Leaf PE
(or vise versa), then that PE needs to process MAC routes from all
other Leaf PEs and add them to its forwarding table. 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.
In this scenario, a PE may have a set of one or more Root sites AND a 2.3 Scenario 3: Leaf OR Root site(s) per MAC
set of one or more Leaf sites for a given VPN instance. An Ethernet
Segment connected to the PE may be identified as both a Root and a In this scenario, a PE may receive traffic from both Root AND Leaf
Leaf site concurrently. sites on a given Attachment Circuit (AC) of a MAC-VRF/bridge table.
Since an Attachment Circuit (ES or ES/VLAN) carries traffic from both
Root and Leaf sites, the granularity at which Root or Leaf sites are
identifies is on a per MAC address. This scenario is considered in
this draft for EVPN service with only known unicast traffic - i.e.,
there is no BUM traffic.
+---------+ +---------+ +---------+ +---------+
| PE1 | | PE2 | | PE1 | | PE2 |
+---+ | +---+ | +------+ | +---+ | +---+ +---+ | +---+ | +------+ | +---+ | +---+
|CE1+-----ES1----+--+ | | | | | | +--+----ES2-----+CE2| |CE1+-----ES1----+--+ | | | | | | +--+---ES2/AC1--+CE2|
+---+ (Leaf/Root)| | E | | | MPLS | | | E | | (Leaf/Root)+---+ +---+ (Root) | | E | | | MPLS | | | E | | (Leaf/Root)+---+
| | V | | | /IP | | | V | | | | V | | | /IP | | | V | |
| | I | | | | | | I | | +---+ | | I | | | | | | I | | +---+
| | | | | | | | +--+----ES3-----+CE3| | | | | | | | | +--+---ES2/AC2--+CE3|
| +---+ | +------+ | +---+ | (Leaf) +---+ | +---+ | +------+ | +---+ | (Leaf) +---+
+---------+ +---------+ +---------+ +---------+
Figure 3: Scenario 3 Figure 3: Scenario 3
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 ESI MPLS label used for split-horizon
used to identify a Root and/or Leaf site in E-TREE services. In other filtering of BUM traffic at the egress PE. Such egress filtering
words, [EVPN] has inherent capability to support E-TREE services capabilities can be leveraged in provision of E-TREE services as seen
without defining any new BGP routes. It only requires a minor shortly. In other words, [EVPN] has inherent capability to support E-
modification to the existing procedures and a new BGP Extended TREE services without defining any new BGP routes but just defining a
Community for leaf indication as shown later in this document. new BGP Extended Community for leaf indication as shown later in this
document.
In addition to the procedures below (which is a MUST requirement), an 3.1 Known Unicast Traffic
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 Since in EVPN, MAC learning is performed in control plane via
highlighted in the previous section. advertisement of BGP routes, the filtering needed by E-TREE service
for known unicast traffic can be performed at the ingress PE, thus
providing very efficient filtering and avoiding sending known unicast
traffic over MPLS/IP core to be filtered at the egress PE as done in
traditional E-TREE solutions (e.g., E-TREE for VPLS).
3.1 Known Unicast Traffic To provide such ingress filtering for known unicast traffic, a PE
MUST indicate to other PEs what kind of sites (root or leaf) its MAC
addresses are associated with. This indication is achieved by using
one of the following mechanisms:
For known unicast traffic, the PE must advertise a Leaf indication 1) For single-homing scenarios of sections 2.2 and 2.3, the PE
along with each MAC Advertisement route, to indicate that the advertises the MAC addresses received from a Leaf site, with an
associated MAC address was learnt from a Leaf Attachment Circuit Extended community indicating a leaf flag. The lack of such flag
(AC). The lack of a Leaf indication, indicates the MAC address is indicates that the MAC address is associated with a root site.
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
to/from other ACs in an EVI) unless the AC is explicitly identified
as a leaf.
Tagging MAC addresses with a leaf indication when they are associated 2) For multi-homing scenario of section 2.2, where an AC is either
with a leaf AC, enables remote PEs to perform ingress filtering for root or leaf (but not both), the PE advertises leaf indication along
known unicast traffic - i.e., on the ingress PE, the MAC destination with the Ethernet A-D per EVI route. Since these routes are always
address lookup yields, in addition to the forwarding adjacency, a advertised ahead of MAC advertisements route, there is no need to
flag which indicates whether the target MAC is associated with a Leaf append leaf-indication flag with the MAC advertisement routes. The
site or not. The ingress PE cross-checks this flag with the status of leaf indication flag on Ethernet A-D per EVI route tells the
the originating AC, and if both are Leafs, then the packet is not receiving PEs that all MAC addresses associated with this <ESI, EVI>
forwarded. or <ESI, EVI/VLAN> are from a leaf site. The lack of such leaf-
indication flag tells the receiving PEs that the MAC addresses are
associated with a root site.
The PE places all Leaf ACs of a given bridge domain in a single If a leaf site is multi-homed to PE1 an PE2, and PE1 advertises the
split-horizon group in order to prevent intra-PE forwarding among Ethernet A-D per EVI corresponding to this leaf site with the leaf-
Leaf ACs. This split-horizon function applies to both known unicast indication flag but PE2 does not, then the receiving PE MUST notify
and BUM traffic. the operator of such discrepancy and ignore the leaf-indication flag
on PE1. In other words, in case of discrepancy, the multi-homing for
that pair of PEs is assumed to be in default "root" mode for that
<ESI, EVI> or <ESI, EVI/VLAN>.
3) For multi-homing scenario of section 2.3, where an AC is both root
or leaf (i.e., root or leaf indication is at the granularity of MAC
address), the PE advertises leaf indication along with each MAC
advertisement route just as in (1). No leaf-indication flag SHALL be
sent along with the Ethernet A-D per EVI route for this scenario.
Tagging MAC addresses with a leaf indication (either directly via MAC
advertisement route or indirectly via Ethernet A-D per EVI route)
enables remote PEs to perform ingress filtering for known unicast
traffic - i.e., on the ingress PE, the MAC destination address lookup
yields, in addition to the forwarding adjacency, a 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 the
originating AC, and if both are Leafs, then the packet is not
forwarded.
To support the above ingress filtering functionality, a new E-TREE To support the above ingress filtering functionality, a new E-TREE
Extended Community with a Leaf indication flag is introduced [section Extended Community with a Leaf indication flag is introduced [section
5.1]. This new Extended Community is advertised with each EVPN MAC/IP 5.2]. This new Extended Community is advertised with either Ethernet
Advertisement route. A-D per EVI route or MAC/IP Advertisement route as described above.
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 Leaf AC or a
AC, the MPLS-encapsulated frames MUST be tagged with an indication of root AC, the MPLS-encapsulated frames MUST be tagged with an
whether they originated from a Root or a Leaf AC. This can be indication of whether they originated from a Leaf AC or not. In other
achieved in EVPN through the use of the ESI MPLS label. Therefore, words, leaf/root indication for BUM traffic is done at the
the ESI MPLS label not only identifies the Ethernet segment of origin granularity of AC. This can be achieved in EVPN through the use of
for a given frame, but also it identifies its type (e.g., Leaf or the ESI MPLS label. Therefore, the ESI MPLS label can be used to
Root). either identify the Ethernet segment of origin per [RFC 7432] or it
can be used to indicate that the packet is originated from a leaf
3.2.1 BUM Traffic supported by P2MP Tunnels site.
For multi-homing use cases where BUM traffic uses P2MP LSP, the
ingress PE adds an upstream-assigned ESI MPLS label to the frame per
[RFC7432] procedures and sends it to all the intended ingress PE
devices. Two ESI MPLS labels are used for each multi-homed Ethernet
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.
It should be noted that the former ESI MPLS label implicitly
identifies a Root Ethernet segment - i.e., an ESI MPLS label that is
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.
The egress PE can determine whether or not to forward a particular
frame to the destination 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.
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.
For single-homing use cases where BUM traffic uses P2MP LSP, the
ingress PE adds a special ESI MPLS label to the frame if the frame is
originated from a Leaf site. This special ESI MPLS label used for
single-homing scenarios is not on a per ES basis but rather on a per
PE basis - i.e., a single ESI MPLS label is used for all single-homed
segments on that PE. If the frame is originated from a Root site,
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 BUM traffic sent over a P2MP LSP or ingress replication, may need to
carry an upstream assigned or downstream assigned MPLS label
(respectively) for the purpose of egress filtering to indicate to the
egress PEs whether this packet is originated from a root AC or a leaf
AC.
The procedures for supporting BUM traffic using ingress replication, The main difference between downstream and upstream assigned ESI MPLS
are similar to the ones in the previous section. The main differences label is that in case of downstream assigned not all egress PE
are that the ESI label is downstream assigned and not all egress PE
devices need to receive the ESI label just like ingress replication devices need to receive the ESI label just like ingress replication
procedures defined in [RFC7432]. procedures defined in [RFC7432].
For frames received from a multi-homed Ethernet segment, the ingress There are four scenarios to consider:
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 3.2.1 BUM traffic originated from a single-homed site on a leaf AC
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 In this scenario, the ingress PE adds a special ESI MPLS label to the
same multi-homed Ethernet Segment and the frame is received on a Root frame indicating a Leaf site. This special ESI MPLS label used for
AC, then the ingress PE does not add any ESI MPLS label to the frame single-homing scenarios is not on a per ES basis but rather on a per
per [RFC7432]. PE basis - i.e., a single ESI MPLS label is used for all single-homed
ES's on that PE. This special ESI MPLS label is advertised to other
PE devices, using a new EVPN Extended Community called Leaf ESI MPLS
label Extended Community (section 5.1) along with a set of Ethernet
A-D per ES routes. The set of Ethernet A-D per ES routes may be
needed if the number of Route Targets (RTs) that need to be sent
exceed the limit on a single route per [RFC 7432]. The RT(s)
represent EVIs with at least a leaf site in them. The ESI for the
Ethernet A-D per ES route is set to zero indicating single-homed
sites.
For frames received from a single-homed Ethernet segment, the ingress When a PE receives this special ESI MPLS label in the data path, it
PE may or may not add an ESI MPLS label based on the following blocks the packet if the destination AC is of type Leaf; otherwise,
criteria: it forwards the packet.
- If the frame is received on a Root AC, then the ingress PE does not 3.2.2 BUM traffic originated from a single-homed site on a root AC
add any ESI MPLS label to the frame.
- If the frame is received on a Leaf AC, then the ingress PE adds a In this scenario, the ingress PE does not add any ESI MPLS label and
special downstream-assigned ESI MPLS label indicating Leaf to the it operates per [RFC7432] procedures.
frame.
Just as described in the previous section, the Leaf indication is 3.2.3 BUM traffic originated from a multi-homed site on a leaf AC
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 In this scenario, the ingress PE adds an ESI MPLS label to the frame
frame to the desitnation Ethernet Segment depending on the following indicating both the Ethernet Segment of origin and its Leaf type. The
rules: reason Ethernet Segment of origin needs to be identified in addition
to Leaf type, is to accommodate multi-homing scenarios for Integrated
Routing and Bridging (IRB) where a source (Leaf) can be on one VLAN
and the receivers (roots) can be on some other VLANs for the same
Ethernet Segment.
- If the ESI MPLS label indicates that the source Ethernet Segment is This ESI MPLS label is advertised to other PE devices, using a new
the same as destination Ethernet segment, then the frame is blocked EVPN Extended Community called Leaf ESI Label Extended Community
according to the split-horizon rule in [RFC7432]. (section 5.1) along with a set of Ethernet A-D per ES routes
corresponding to the ES of the origin. If the egress ES is the same
as the originated ES, then the receiving PE uses the same procedure
for filtering BUM traffic as the one specified in [RFC 7432]. If the
egress ES is different from the originated ES, then the receiving PE
uses the ESI label to identify that the BUM traffic is associated
with a leaf site and thus blocking the BUM traffic if the destination
AC is also of type Leaf similar to section 3.2.1.
- If the ESI MPLS label indicates that the source Ethernet Segment is 3.2.4 BUM traffic originated from a multi-homed site on a root AC
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 In this scenario, both the ingress and egress PE devices follows the
not the same as destination Ethernet segment but it has a Leaf procedure defined in [RFC 7432] for adding and/or processing an ESI
indication, then the frame is blocked if the destination AC is of MPLS label.
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 The ingress PE imposes the right ESI MPLS label depending on whether
blocked if the destination AC is of type Leaf and it is forwarded if the Ethernet frame originated from the Root or Leaf site on that
the destination AC is of type Root. 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 for
identifying whether an egress AC is a root or leaf is beyond the
scope of this document.
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
skipping to change at page 11, line 32 skipping to change at page 11, line 7
Leaf to Root sites. In this case, the PE with Root sites performs MAC Leaf to Root sites. In this case, the PE with Root sites performs MAC
learning in the data-path over the Ethernet Segments, and advertises learning in the data-path over the Ethernet Segments, and advertises
reachability in EVPN MAC Advertisement routes. These routes will be reachability in EVPN MAC Advertisement routes. These routes will be
imported by PEs that have Leaf sites as well as by PEs that have Root imported by PEs that have Leaf sites as well as by PEs that have Root
sites, in a given EVI. Similarly, the PEs with Leaf sites perform MAC sites, in a given EVI. Similarly, the PEs with Leaf sites perform MAC
learning in the data-path over their Ethernet Segments, and advertise learning in the data-path over their Ethernet Segments, and advertise
reachability in EVPN MAC Advertisement routes 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 per [RFC 7432].
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 [RFC7432]. 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.
skipping to change at page 12, line 12 skipping to change at page 11, line 34
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 [RFC7432], 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 B-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 new E-TREE extended community case, this flag will be added to the new E-TREE Extended Community
defined in section [5.1], and advertised with each MAC Advertisement defined in section [5.2], and advertised with each MAC 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 implicitly denoting Root and the other advertised: one B-MAC address implicitly denoting Root and the other
explicitly denoting Leaf. The former B-MAC address is not advertised explicitly denoting Leaf. The former B-MAC address is not advertised
with the E-TREE extended community but the latter B-MAC denoting Leaf with the E-TREE extended community but the latter B-MAC denoting Leaf
is advertised with the new E-TREE extended community. is advertised with the new E-TREE extended community.
The ingress PE uses the right B-MAC source address depending on The ingress PE uses the right B-MAC source address depending on
whether the Ethernet frame originated from the Root or Leaf 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. Tag basis.
In the case where a multi-homed Ethernet Segment has only Root or In the case where a multi-homed Ethernet Segment has only Root OR
Leaf sites attached, then a single B-MAC address is allocated and Leaf sites attached, then a single B-MAC address is allocated and
advertised per segment. advertised per segment.
Furthermore, a PE advertises two special global B-MAC addresses: one 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 for Root and another for Leaf, and tags the Leaf one as such in the
Advertisement routes. These B-MAC addresses are used as source MAC Advertisement route. These B-MAC addresses are used as source
addresses for traffic originating from single-homed segments. 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.
The PE places all Leaf Ethernet Segments of a given bridge domain in
a single split-horizon group in order to prevent intra-PE forwarding
among Leaf segments. This split-horizon function applies to BUM
traffic as well.
4.2 BUM Traffic 4.2 BUM Traffic
For BUM traffic, the PEs must perform egress filtering. When a PE For BUM traffic, the PEs must perform egress filtering. When a PE
receives a MAC advertisement route, it updates its Ethernet Segment receives a MAC advertisement route, it updates its Ethernet Segment
egress filtering function (based on the B-MAC source address), as egress filtering function (based on the B-MAC source address), as
follows: follows:
- If the MAC Advertisement route indicates that the advertised B-MAC - If the MAC Advertisement route indicates that the advertised B-MAC
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.
The PE places all Leaf Ethernet Segments of a given bridge domain in
a single split-horizon group in order to prevent intra-PE forwarding
among Leaf segments. This split-horizon function applies to BUM
traffic.
5 BGP Encoding 5 BGP Encoding
This document defines one new BGP Extended Community for EVPN. This document defines two new BGP Extended Community for EVPN.
5.1 E-TREE Extended Community 5.1 Leaf ESI Label Extended Community
This Extended Community is a new transitive Extended Community having
a Type field value of 0x06 (EVPN) and the Sub-Type 0x04. In purpose,
it is similar to ESI Label EC defined in [RFC 7432] with the only
difference that it is used to indicate a leaf site in addition to the
Ethernet segment of origin.
It may be advertised along with Ethernet Auto-discovery routes, and
it enables split-horizon procedures for multihomed sites as described
in Section 3.2.1.3. The Leaf ESI Label field represents an ES with a
leaf site by the advertising PE, and it is used in split-horizon
filtering by other PEs that are connected to the same multihomed
Ethernet segment and egress filtering by other PEs that are connected
to Leaf ACs.
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 | Reserved=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved=0 | Leaf ESI Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.2 E-TREE Extended Community
A new EVPN BGP Extended Community called E-TREE is introduced here. A new EVPN BGP Extended Community called E-TREE is introduced here.
This new extended community is a transitive extended community with This new extended community is a transitive extended community with
the Type field of 0x06 (EVPN) and the Sub-Type of 0x04. This extended the Type field of 0x06 (EVPN) and the Sub-Type of 0x05. This extended
community is used to for leaf indication and it is advertised with an 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 EVPN MAC/IP route or an Ethernet A-D per EVI route.
with an Ethernet A-D per ES route, it is sent along with ESI Label
Extended Community defined in section 7.5 of [RFC7432].
The E-TREE Extended Community is encoded as an 8-octet value as The E-TREE Extended Community is encoded as an 8-octet value as
follows: follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=0x06 | Sub-Type=0x04 | E-TREE Flags | | Type=0x06 | Sub-Type=0x05 | Reserved=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| E-TREE Flags L| | Rserved=0 | Reserved=0 |L|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Leaf flag (L): A value of 1 indicates a leaf Leaf flag (L): A value of 1 indicates a leaf
6 Acknowledgement 6 Acknowledgement
We would like to thank Dennis Cai for his comments. We would like to thank Dennis Cai and Antoni Przygienda for their
comments.
7 Security Considerations 7 Security Considerations
Same security considerations as [RFC7432]. Same security considerations as [RFC7432].
8 IANA Considerations 8 IANA Considerations
Allocation of Extended Community Type and Sub-Type for EVPN. Allocation of Extended Community Type and Sub-Type for EVPN.
9 References 9 References
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