Internet DRAFT - draft-rabadan-l2vpn-dci-evpn-overlay
draft-rabadan-l2vpn-dci-evpn-overlay
L2VPN Workgroup J. Rabadan
Internet Draft S. Sathappan
Intended status: Standards Track W. Henderickx
S. Palislamovic
Alcatel-Lucent
F. Balus
Nuage Networks
Expires: August 18, 2014 February 14, 2014
Data Center Interconnect Solution for EVPN Overlay networks
draft-rabadan-l2vpn-dci-evpn-overlay-01.txt
Abstract
This document describes how Network Virtualization Overlay networks
(NVO3) can be connected to a Wide Area Network (WAN) in order to
extend the layer-2 connectivity required for some tenants. The
solution will analyze the interaction between NVO3 networks running
EVPN and other L2VPN technologies used in the WAN, such as VPLS/PBB-
VPLS or EVPN/PBB-EVPN, and will propose a solution for the
interworking between both.
Status of this Memo
This Internet-Draft is submitted 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/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
Rabadan et al. Expires August 18, 2014 [Page 1]
Internet-Draft DCI for E-VPN Overlays February 14, 2014
This Internet-Draft will expire on August 18, 2014.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Decoupled DCI solution for EVPN overlay networks . . . . . . . 3
2.1. Interconnect requirements . . . . . . . . . . . . . . . . . 4
2.2. VLAN-based hand-off . . . . . . . . . . . . . . . . . . . . 5
2.3. Pseudowire-based hand-off . . . . . . . . . . . . . . . . . 5
2.4. Multi-homing solution . . . . . . . . . . . . . . . . . . . 6
2.5. Data Center Gateway Optimizations . . . . . . . . . . . . . 7
2.5.1 Use of the Unknown MAC route to reduce unknown
flooding . . . . . . . . . . . . . . . . . . . . . . . . 7
2.5.2. MAC address advertisement control . . . . . . . . . . . 7
2.5.3. ARP flooding control . . . . . . . . . . . . . . . . . 8
3. Integrated DCI solution for EVPN overlay networks . . . . . . . 8
3.1. Interconnect requirements . . . . . . . . . . . . . . . . . 9
3.2. VPLS DCI for EVPN-Overlay networks . . . . . . . . . . . . 10
3.2.1. Control/Data Plane setup procedures on the DC GWs . . . 10
3.2.2. Multi-homing procedures on the DC GWs . . . . . . . . . 11
3.3. PBB-VPLS DCI for EVPN-Overlay networks . . . . . . . . . . 11
3.3.1. Control/Data Plane setup procedures on the DC GWs . . . 11
3.3.2. Multi-homing procedures on the DC GWs . . . . . . . . . 12
3.4. EVPN-MPLS DCI for EVPN-Overlay networks . . . . . . . . . . 12
3.4.1. Control Plane setup procedures on the DC GWs . . . . . 12
3.4.2. Data Plane setup procedures on the DC GWs . . . . . . . 14
3.4.3. Multi-homing procedures on the DC GWs . . . . . . . . . 14
3.4.4. Impact on MAC Mobility procedures . . . . . . . . . . . 15
3.4.5. Data Center Gateway optimizations . . . . . . . . . . . 16
3.4.6. Benefits of the EVPN-MPLS DCI solution . . . . . . . . 16
3.5. PBB-EVPN DCI for EVPN-Overlay networks . . . . . . . . . . 17
3.5.1. Control/Data Plane setup procedures on the DC GWs . . . 17
Rabadan et al. Expires August 18, 2014 [Page 2]
Internet-Draft DCI for E-VPN Overlays February 14, 2014
3.5.2. Multi-homing procedures on the DC GWs . . . . . . . . . 18
3.5.3. Impact on MAC Mobility procedures . . . . . . . . . . . 18
3.5.4. Data Center Gateway optimizations . . . . . . . . . . . 18
5. Conventions and Terminology . . . . . . . . . . . . . . . . . . 18
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 19
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 19
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8.1. Normative References . . . . . . . . . . . . . . . . . . . 19
8.2. Informative References . . . . . . . . . . . . . . . . . . 19
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 20
10. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction
[EVPN-Overlays] discusses the use of EVPN as the control plane for
Network Virtualization Overlay (NVO) networks, where VXLAN, NVGRE or
MPLS over GRE can be used as possible data plane encapsulation
options.
While this model provides a scalable and efficient multi-tenant
solution within the Data Center, it might not be easily extended to
the WAN in some cases due to the requirements and existing deployed
technologies. For instance, a Service Provider might have an already
deployed (PBB-)VPLS or (PBB-)EVPN network that must be used to
interconnect Data Centers and WAN VPN users.
This document describes a Data Center Interconnect (DCI) solution for
E-VPN overlay Data Center networks, assuming that the Data Center
Gateway (DC GW) and the WAN Edge functions can be decoupled in two
separate systems or integrated into the same system. The former
option will be referred as "Decoupled DCI solution" throughout the
document whereas the latter one will be referred as "Integrated DCI
solution".
2. Decoupled DCI solution for EVPN overlay networks
This section describes the interconnect solution when the DC GW and
WAN Edge functions implemented in different systems. Figure 1 depicts
the reference model described in this section.
Rabadan et al. Expires August 18, 2014 [Page 3]
Internet-Draft DCI for E-VPN Overlays February 14, 2014
+--+
|CE|
+--+
|
+----+
+----| PE |----+
+---------+ | +----+ | +---------+
+----+ | +---+ +----+ +----+ +---+ | +----+
|NVE1|--| |DC | |WAN | |WAN | |DC | |--|NVE3|
+----+ | |GW1|--|Edge| |Edge|--|GW3| | +----+
| +---+ +----+ +----+ +---+ |
| DC1 | | WAN | | DC2 |
| +---+ +----+ +----+ +---+ |
| |DC | |WAN | |WAN | |DC | |
+----+ | |GW2|--|Edge| |Edge|--|GW4| | +----+
|NVE2|--| +---+ +----+ +----+ +---+ |--|NVE4|
+----+ +---------+ | | +---------+ +----+
+--------------+
|<-EVPN-Overlay-->|<-VLAN->|<-WAN L2VPN->|<--PW-->|<--EVPN-Overlay->|
hand-off hand-off
Figure 1 Decouple DCI model
The following section describes the interconnect requirements that
make Service Providers select this model and the requirements of the
solution itself.
2.1. Interconnect requirements
The proposed Interconnect architecture will be normally deployed in
networks where the EVPN-Overlay provider and WAN providers are
different entities and a clear demarcation is needed. The solution
must observe the following requirements:
o A simple connectivity hand-off must be provided between the EVPN-
Overlay network provider and the WAN provider so that QoS and
security enforcement are easily accomplished.
o The solution must be independent of the L2VPN technology deployed
in the WAN.
o Multi-homing between DC GW and WAN Edge routers is required. Per-
service load balancing MUST be supported. Per-flow load balancing
MAY be supported but it is not a strong requirement since a
deterministic path per service is usually required for an easy QoS
and security enforcement.
Rabadan et al. Expires August 18, 2014 [Page 4]
Internet-Draft DCI for E-VPN Overlays February 14, 2014
o Ethernet OAM and Connectivity Fault Management (CFM) functions must
be supported between the EVPN-Overlay network and the WAN network.
o The following optimizations MAY be supported at the DC GW:
+ Unknown flooding reduction for the unicast traffic sourced from
the DC Network Virtualization Edge devices (NVEs).
+ Control of the WAN MAC addresses advertised to the DC.
+ ARP flooding control for the requests coming from the WAN.
2.2. VLAN-based hand-off
In this option, the hand-off between the DC GWs and the WAN Edge
routers is based on 802.1Q VLANs. This is illustrated in Figure 1,
between the DC GWs in DC1 and the WAN Edge routers. Each EVPN
Instance (EVI) in the DC GW is connected to a different VPLS/EVI
instance in the WAN Edge router by using a different C-TAG VLAN ID or
a different combination of S-TAG/C-TAG VLAN IDs that matches at both
sides. In this use-case, the WAN Edge router becomes a VPLS/EVPN PE
with regular Attachment Circuits.
This option provides the best possible demarcation between the DC and
WAN providers and it does not require control plane interaction
between both providers. The disadvantages of this model are the
provisioning overhead and the reduced scalability (limited to the
VLAN-ID space).
In this model, the DC GW acts as a regular Network Virtualization
Edge (NVE) towards the DC. Its control plane, data plane procedures
and interactions are described in [EVPN-Overlays].
The WAN Edge router acts as a (PBB-)VPLS or (PBB-)EVPN PE. Its
functions are described in [RFC4761][RFC4762][RFC6074] or [EVPN][PBB-
EVPN].
2.3. Pseudowire-based hand-off
If MPLS can be enabled between the DC GW and the WAN Edge router, a
more scalable DCI solution can be deployed. In this option the hand-
off between both routers is based on FEC128-based pseudowires or,
alternatively, FEC129-based pseudowires for a greater level of
network automation. Note that this model still provides a clear
demarcation boundary between DC and WAN, and security/QoS policies
may be applied on a per pseudowire basis. The PW-based hand-off
interconnect is illustrated in Figure 1, between the DC2 DC GWs and
the WAN Edge routers.
In this model, besides the usual MPLS procedures between DC GW and
WAN Edge router, the DC GW MUST support an interworking function in
Rabadan et al. Expires August 18, 2014 [Page 5]
Internet-Draft DCI for E-VPN Overlays February 14, 2014
each EVI that requires extension to the WAN:
o If a FEC128-based pseudowire is used between the EVI (DC GW) and
the VSI (WAN Edge), the provisioning of the VCID for such
pseudowire MUST be supported on the EVI and must match the VCID
used in the peer VSI at the WAN Edge router.
o If BGP Auto-discovery [RFC6074] and FEC129-based pseudowires are
used between the DC GW EVI and the WAN Edge VSI, the provisioning
of the VPLS-ID MUST be supported on the EVI and must match the
VPLS-ID used in the WAN Edge VSI.
2.4. Multi-homing solution
As already discussed, single-active multi-homing, i.e. per-service
load-balancing multi-homing MUST be supported in this type of
interconnect. All-active multi-homing may be considered in future
revisions of this document.
The DC GWs will be provisioned with a unique ESI per WAN interconnect
and the hand-off attachment circuits or pseudowires between the DC GW
and the WAN Edge router will be assigned to such ESI. The ESI will be
administratively configured on the DC GWs according to the procedures
in [EVPN] and its use assumes that the DC GWs are connected to a
single DC and to a single WAN domain. Multi-homing for cases where
the DC GWs are connected to more than one DC and/or more than one WAN
domain is for further study. This ESI will be referred as "DCI-ESI"
hereafter.
The solution (on the DC GWs) MUST follow the single-active multi-
homing procedures as described in [EVPN-Overlays] for the provisioned
DCI-ESI, i.e. Ethernet A-D routes per ESI and per EVI will be
advertised to the DC NVEs. The MAC addresses learnt (in the data
plane) on the hand-off links will be advertised with the DCI-ESI
encoded in the ESI field.
The use of OAM is recommended between the DC GWs and the WAN Edge
routers:
o If the DCI solution is based on a VLAN hand-off, 802.1ag/Y.1731
Ethernet-CFM can be used by the non-DF DC GW so that the peer WAN
Edge router do not send any traffic to the DC GW for that
particular EVI.
o If the VPLS DCI solution is based on a pseudowire hand-off, the LDP
PW Status bits TLV can be used by the non-DF to signal "Standby
status" to the WAN Edge router for that particular EVI.
Rabadan et al. Expires August 18, 2014 [Page 6]
Internet-Draft DCI for E-VPN Overlays February 14, 2014
2.5. Data Center Gateway Optimizations
The following features MAY be supported on the DC GW in order to
optimize the control plane and data plane in the DC.
2.5.1 Use of the Unknown MAC route to reduce unknown flooding
The use of EVPN, as the control plane of Network Virtualization
Networks in the DC, brings a significant number of benefits as
described in [EVPN-Overlays]. There are however some potential
issues that SHOULD be addressed when the DC EVIs are connected to
the WAN VPN instances.
The first issue is the additional unknown unicast flooding created
in the DC due to the unknown MACs existing beyond the DC GW. In
virtualized DCs where all the MAC addresses are learnt in the
control/management plane, unknown unicast flooding is
significantly reduced. This is no longer true if the DC GW is
connected to a layer-2 domain with data plane learning.
The solution suggested in this document is based on the use of an
"Unknown MAC route" that is advertised by the Designated Forwarder
DC GW. The Unknown MAC route is a regular EVPN MAC/IP
Advertisement route where the MAC Address Length is set to 48 and
the MAC address to 00:00:00:00:00:00 (IP length is set to 0).
If this procedure is used, when an EVI is created in the DC GWs
and the Designated Forwarder (DF) is elected, the DF will send the
Unknown MAC route. The NVEs supporting this concept will prune
their unknown unicast flooding list and will only send the unknown
unicast packets to the owner of the Unknown MAC route. Note that
the DCI-ESI will be encoded in the ESI field of the NLRI so that
regular multi-homing procedures can be applied to this unknown MAC
too (e.g. backup-path).
2.5.2. MAC address advertisement control
Another issue derived from the EVI interconnect to the WAN layer-2
domain is the potential massive MAC advertisement into the DC. All
the MAC addresses learnt from the WAN on the hand-off attachment
circuits or pseudowires must be advertised by BGP EVPN. Even if
optimized BGP techniques like RT-constraint are used, the amount
of MAC addresses to advertise or withdraw (in case of failure)
from the DC GWs can be difficult to control and overwhelming for
the DC network, especially when the NVEs reside in the
hypervisors.
This document proposes the addition of administrative options so
Rabadan et al. Expires August 18, 2014 [Page 7]
Internet-Draft DCI for E-VPN Overlays February 14, 2014
that the user can enable/disable the advertisement of MAC
addresses learnt from the WAN as well as the advertisement of the
Unknown MAC route from the DF DC GW. In cases where all the DC MAC
addresses are learnt in the control/management plane, the DC GW
may disable the advertisement of WAN MAC addresses. Any frame with
unknown destination MAC will be exclusively sent to the Unknown
MAC route owner(s).
2.5.3. ARP flooding control
Another optimization mechanism, naturally provided by EVPN in the
DC GWs, is the Proxy ARP function. The DC GWs SHOULD build a Proxy
ARP cache table as per [EVPN]. When the active DC GW receives an
ARP request coming from the WAN, the DC GW does a Proxy ARP table
lookup and replies to the ARP request as long as the information
is available in its table.
This mechanism is specially recommended on the DC GWs since it
protects the DC network from external ARP-flooding.
3. Integrated DCI solution for EVPN overlay networks
When the DC and the WAN are operated by the same administrative
entity, the Service Provider can decide to integrate the DC GW and
WAN Edge PE functions in the same router for obvious CAPEX and
OPEX saving reasons. This is illustrated in Figure 2. Note that
this model does not provide an explicit demarcation link between
DC and WAN anymore. ACLs or QoS policies between DC and WAN are
not required.
Rabadan et al. Expires August 18, 2014 [Page 8]
Internet-Draft DCI for E-VPN Overlays February 14, 2014
+--+
|CE|
+--+
|
+----+
+----| PE |----+
+---------+ | +----+ | +---------+
+----+ | +---+ +---+ | +----+
|NVE1|--| |DC | |DC | |--|NVE3|
+----+ | |GW1| |GW3| | +----+
| +---+ +---+ |
| DC1 | WAN | DC2 |
| +---+ +---+ |
| |DC | |DC | |
+----+ | |GW2| |GW4| | +----+
|NVE2|--| +---+ +---+ |--|NVE4|
+----+ +---------+ | | +---------+ +----+
+--------------+
|<--EVPN-Overlay--->|<-----VPLS--->|<---EVPN-Overlay-->|
|<--PBB-VPLS-->|
DCI options -> |<-EVPN-MPLS-->|
|<--PBB-EVPN-->|
Figure 2 Integrated DCI model
3.1. Interconnect requirements
The solution must observe the following requirements:
o The DC GW function must provide control plane and data plane
interworking between the EVPN-overlay network and the L2VPN
technology supported in the WAN, i.e. (PBB-)VPLS or (PBB-)EVPN, as
depicted in Figure 2.
o Multi-homing MUST be supported. Single-active multi-homing with
per-service load balancing MUST be implemented. All-active multi-
homing, i.e. per-flow load-balancing, MUST be implemented as long
as the technology deployed in the WAN supports it.
o If EVPN is deployed in the WAN, the MAC Mobility, Static MAC
protection and other procedures (e.g. proxy-arp) described in
[EVPN] must be supported end-to-end.
o Any type of inclusive multicast tree MUST be independently
supported in the WAN as per [EVPN], and in the DC as per [EVPN-
Overlays].
Rabadan et al. Expires August 18, 2014 [Page 9]
Internet-Draft DCI for E-VPN Overlays February 14, 2014
3.2. VPLS DCI for EVPN-Overlay networks
3.2.1. Control/Data Plane setup procedures on the DC GWs
Regular MPLS tunnels and TLDP/BGP sessions will be setup to the WAN
PEs and RRs as per [RFC4761][RFC4762][RFC6074] and overlay tunnels
and EVPN will be setup as per [EVPN-Overlays]. Note that different
route-targets for the DC and for the WAN are normally required. A
single type-1 RD per service can be used.
In order to support multi-homing, the DC GWs will be provisioned with
a DCI-ESI (see section 2.4), that will be unique per interconnection.
Note that Ethernet Segment is a system wide assigned value, as
opposed to the Ethernet Segments defined in [EVPN]. All the [EVPN]
procedures are still followed for the DCI-ESI, e.g. any MAC address
learnt from the WAN will be advertised to the DC with the DCI-ESI in
the ESI field.
A MAC-VRF per EVI will be created in each DC GW. The MAC-VRF will
have two different types of tunnel bindings instantiated in two
different split-horizon-groups:
o VPLS pseudowires will be instantiated in the "WAN
split-horizon-group".
o Overlay tunnel bindings (e.g. VXLAN, NVGRE) will be instantiated
in the "DC split-horizon-group".
Attachment circuits are also supported on the same MAC-VRF, but they
will not be part of any of the above split-horizon-groups.
Traffic received in a given split-horizon-group will never be
forwarded to a member of the same split-horizon-group.
As far as BUM flooding is concerned, a flooding list will be created
with the sub-list created by the inclusive multicast routes and the
sub-list created for VPLS in the WAN. BUM frames received from a
local attachment circuit will be flooded to both sub-lists. BUM
frames received from the DC or the WAN will be forwarded to the
flooding list observing the split-horizon-group rule described above.
Note that the DC GWs are not allowed to have an EVPN binding and a
pseudowire to the same far-end within the same MAC-VRF in order to
avoid loops and packet duplication:
o If an EVPN binding exists between two DC GWs and an attempt is
made to setup a pseudowire between them, the pseudowire will be
kept operationally down. The corresponding OAM signaling will be
Rabadan et al. Expires August 18, 2014 [Page 10]
Internet-Draft DCI for E-VPN Overlays February 14, 2014
triggered.
o If a pseudowire exists between two DC GWs and an attempt is made
to setup an EVPN binding, the pseudowire will be brought
operationally down before establishing the EVPN binding.
The optimizations procedures described in section 2.5 can also be
applied to this option.
3.2.2. Multi-homing procedures on the DC GWs
Single-active multi-homing MUST be supported on the DC GWs. All-
active multi-homing is not supported by VPLS.
All the single-active multi-homing procedures as described by [EVPN-
Overlays] will be followed for the DCI-ESI.
The non-DF DC GW for the DCI-ESI will block the transmission and
reception of all the bindings in the "WAN aplit-horizon-group" for
BUM and unicast traffic.
3.3. PBB-VPLS DCI for EVPN-Overlay networks
3.3.1. Control/Data Plane setup procedures on the DC GWs
In this case, there is no impact on the procedures described in
[RFC7041] for the B-component. However the I-component instances
become EVI instances with EVPN-Overlay bindings and potentially local
attachment circuits. M EVI instances can be multiplexed into the same
B-component instance. This option provides significant savings in
terms of pseudowires to be maintained in the WAN.
The DCI-ESI concept described in section 3.2.1 will also be used for
the PBB-VPLS-based DCI.
B-component pseudowires and I-component EVPN-overlay bindings
established to the same far-end will be compared. The following rules
will be observed:
o Attempts to setup a pseudowire between the two DC GWs within the
B-component context will never be blocked.
o If a pseudowire exists between two DC GWs for the B-component
and an attempt is made to setup an EVPN binding on an I-component
linked to that B-component, the EVPN binding will be kept
operationally down. Note that the BGP EVPN routes will still be
valid but not used.
Rabadan et al. Expires August 18, 2014 [Page 11]
Internet-Draft DCI for E-VPN Overlays February 14, 2014
o The EVPN binding will only be up and used as long as there is no
pseudowire to the same far-end in the corresponding B-component.
The EVPN bindings in the I-components will be brought down before
the pseudowire in the B-component is brought up.
The optimizations procedures described in section 2.5 can also be
applied to this DCI option.
3.3.2. Multi-homing procedures on the DC GWs
Single-active multi-homing MUST be supported on the DC GWs. All-
active multi-homing MAY be supported. Procedures for the support of
all-active multi-homing are for further study.
All the single-active multi-homing procedures as described by [EVPN-
Overlays] will be followed for the DCI-ESI for each EVI instance
connected to B-component.
The non-DF DC GW for the DCI-ESI will block the transmission and
reception of all the EVPN bindings in the corresponding I-components
for BUM and unicast traffic.
3.4. EVPN-MPLS DCI for EVPN-Overlay networks
If EVPN for MPLS tunnels, EVPN-MPLS hereafter, is supported in the
WAN, an end-to-end EVPN solution can be deployed. The following
sections describe the proposed solution as well as the impact
required on the [EVPN] procedures.
3.4.1. Control Plane setup procedures on the DC GWs
The DC GWs MUST establish separate BGP sessions for sending/receiving
EVPN routes to/from the DC and to/from the WAN. Normally each DC GW
will setup one (two) BGP EVPN session(s) to the DC RR(s) and one(two)
session(s) to the WAN RR(s). The route-distinguisher (RD) per EVI can
be used for the EVPN routes sent to both, WAN and DC RRs. On the
contrary, although reusing the same value is possible, different
route-targets are expected to be handled for the same EVI in the WAN.
As in the other discussed options, a DCI-ESI will be configured on
the DC GWs for multi-homing.
Received EVPN routes will never be reflected on the DC GWs but
consumed and re-advertised (if needed):
o Ethernet A-D routes, ES routes and inclusive multicast routes
are consumed by the DC GWs and processed locally for the
Rabadan et al. Expires August 18, 2014 [Page 12]
Internet-Draft DCI for E-VPN Overlays February 14, 2014
corresponding [EVPN] procedures.
o MAC/IP advertisement routes will be received, imported and if
they become active in the MAC FIB, the information will be re-
advertised as a new route:
+ The RD will be the DC GW's RD for the service.
+ The ESI will be set to the DCI-ESI.
+ The Ethernet-tag will be 0 or a new value.
+ The MAC length, MAC address, IP Length and IP address values
will be kept from the previously received NLRI.
+ The MPLS label will be 0 or a local label.
+ The appropriate RTs and [RFC5512] BGP Encapsulation extended
community will be used according to [EVPN-Overlays].
The DC GWs will also generate the following local EVPN routes that
will be sent to the DC and WAN, with their corresponding RT and
[RFC5512] BGP Encapsulation extended community values:
o ES route for the DCI-ESI.
o Ethernet A-D routes per ESI and EVI for the DCI-ESI.
o Inclusive multicast routes with independent tunnel type value
for the WAN and DC. E.g. a P2MP LSP may be used in the WAN
whereas ingress replication is used in the DC.
o MAC/IP advertisement routes for MAC addresses learnt in local
attachment circuits. Note that these routes will not include the
DCI-ESI, but ESI=0 or different from 0 for local Ethernet
Segments (ES).
Note that each DC GW will receive two copies of each of the above
routes generated by the peer DC GW (one copy for the DC encapsulation
and one copy for the WAN encapsulation). This is the expected
behavior on the DC GW:
o ES and A-D (per ESI) routes: regular BGP selection will be
applied.
o Inclusive multicast routes: if the Ethernet Tag ID matches on
both routes, regular BGP selection applies and only one route
will be active. It is recommended to influence the BGP selection
Rabadan et al. Expires August 18, 2014 [Page 13]
Internet-Draft DCI for E-VPN Overlays February 14, 2014
so that the DC route is preferred. If the Ethernet Tag ID does
not match, then BGP will consider them two separate routes. In
that case, the EVI service will select the DC route.
o MAC/IP advertisement routes for local attachment circuits: as
above, the DC GW will select only one. The decision will be made
at BGP or service level, depending on the Ethernet Tags.
The optimizations procedures described in section 2.5 can also be
applied to this option.
3.4.2. Data Plane setup procedures on the DC GWs
The procedure explained at the end of the previous section will make
sure there are no loops or packet duplication between the DC GWs of
the same DC since only one EVPN binding will be setup in the data
plane between the two nodes.
As for the rest of the EVPN tunnel bindings, two flooding lists will
be setup by each DC GW for the same MAC-VRF:
o EVPN-overlay flooding list (composed of bindings to the remote
NVEs or multicast tunnel to the NVEs).
o EVPN-mpls flooding list (composed of MP2P and or LSM tunnel to
the remote PEs)
Each flooding list will be part of a separate split-horizon group.
Traffic generated from a local AC can be flooded to both
split-horizon-groups. Traffic from a binding of a split-horizon-group
can be flooded to the other split-horizon-group and local ACs, but
never to a member of its own split-horizon-group.
3.4.3. Multi-homing procedures on the DC GWs
Single-active as well as all-active multi-homing MUST be supported.
All the multi-homing procedures as described by [EVPN] will be
followed for the DF election for DCI-ESI, as well as the backup-path
(single-active) and aliasing (all-active) procedures on the remote
PEs/NVEs. The following changes are required at the DC GW with
respect to the DCI-ESI:
o Single-active multi-homing; assuming a WAN split-horizon-group,
a DC split-horizon-group and local ACs on the DC GWs:
+ Forwarding behavior on the non-DF: the non-DF MUST NOT forward
BUM or unicast traffic received from a given split-horizon-
Rabadan et al. Expires August 18, 2014 [Page 14]
Internet-Draft DCI for E-VPN Overlays February 14, 2014
group to a member of his own split-horizon group or to the
other split-horizon-group. Only forwarding to local ACs is
allowed (as long as they are not part of an ES for which the
node is non-DF).
+ Forwarding behavior on the DF: the DF MUST NOT forward BUM or
unicast traffic received from a given split-horizon-group to a
member of his own split-horizon group or to the non-DF.
Forwarding to the other split-horizon-group and local ACs is
allowed (as long as they are not part of an ES for which the
node is non-DF).
o All-active multi-homing; assuming a WAN split-horizon-group, a
DC split-horizon-group and local ACs on the DC GWs:
+ Forwarding behavior on the non-DF: the non-DF follows the same
behavior as the non-DF in the single-active case but only for
BUM traffic. Unicast traffic received from a split-horizon-
group MUST NOT be forwarded to a member of its own split-
horizon-group but can be forwarded normally to the other
split-horizon-group and local ACs. If a known unicast packet
is identified as a "flooded" packet, the procedures for BUM
traffic MUST be followed.
+ Forwarding behavior on the DF: the DF follows the same
behavior as the DF in the single-active case but only for BUM
traffic. Unicast traffic received from a split-horizon-group
MUST NOT be forwarded to a member of its own split-horizon-
group but can be forwarded normally to the other split-
horizon-group and local ACs. If a known unicast packet is
identified as a "flooded" packet, the procedures for BUM
traffic MUST be followed.
o No ESI label is required to be signaled for DCI-ESI for its use
by the non-DF in the data path. This is possible because the
non-DF and the DF will never forward BUM traffic (coming from a
split-horizon-group) to each other.
3.4.4. Impact on MAC Mobility procedures
Since the MAC/IP Advertisement routes are not reflected in the DC GWs
but rather consumed and re-advertised if active, the MAC Mobility
procedures can be constrained to each domain (DC or WAN) and resolved
within each domain. In other words, if a MAC moves within the DC, the
DC GW MUST NOT re-advertise the route to the WAN with a change in the
sequence number. Only when the MAC moves from the WAN domain to the
DC domain, the DC GW will re-advertise the MAC with a higher sequence
number in the MAC Mobility extended community. In respect to the MAC
Rabadan et al. Expires August 18, 2014 [Page 15]
Internet-Draft DCI for E-VPN Overlays February 14, 2014
Mobility procedures described in [EVPN] the MAC addresses learnt from
the NVEs in the local DC or on the local ACs will be considered as
local.
The sequence numbers MUST NOT be propagated between domains. The
sticky bit indication in the MAC Mobility extended community MUST be
propagated between domains.
3.4.5. Data Center Gateway optimizations
All the Data Center Gateway optimizations described in section 2.5
MAY be applied to the DC GWs when the DCI is based on EVPN-MPLS.
In particular, the use of the Unknown MAC route, as described in
section 2.5.1, reduces the unknown flooding in the DC but also solves
some transient packet duplication issues in cases of all-active
multi-homing. This is explained in the following paragraph.
Consider the diagram in Figure 2 for EVPN-MPLS DCI and all-active
multi-homing, and the following sequence:
a) MAC Address M1 is advertised from NVE3 in EVI-1.
b) DC GW3 and DC GW4 learn M1 for EVI-1 and re-advertise M1 to the
WAN with DCI2-ESI in the ESI field.
c) DC GW1 and DC GW2 learn M1 and install DC GW3/GW4 as next-hops
following the EVPN aliasing procedures.
d) Before NVE1 learns M1, a packet arrives to NVE1 with
destination M1. The packet is subsequently flooded.
e) Since both DC GW1 and DC GW2 know M1, they both forward the
packet to the WAN (hence creating packet duplication), unless
there is an indication in the data plane that the packet has
been flooded by NVE1. If the DC GWs signal the same VNI/VSID
for MAC/IP advertisement and inclusive multicast routes for
EVI-1, such data plane indication does not exist.
This undesired situation can be avoided by the use of the Unknown MAC
route. If this route is used, the NVEs will prune their unknown
unicast flooding list, and the non-DF DC GW will not received unknown
packets, only the DF will. This solves the MAC duplication issue
described above.
3.4.6. Benefits of the EVPN-MPLS DCI solution
Besides retaining the EVPN attributes between Data Centers and
Rabadan et al. Expires August 18, 2014 [Page 16]
Internet-Draft DCI for E-VPN Overlays February 14, 2014
throughout the WAN, the EVPN-MPLS DCI solution on the DC GWs has some
benefits compared to pure BGP EVPN RR or Inter-AS model B solutions
without a gateway:
o The solution supports the connectivity of local attachment
circuits on the DC GWs.
o Different data plane encapsulations can be supported in the DC
and the WAN.
o Optimized multicast solution, with independent inclusive
multicast trees in DC and WAN.
o MPLS Label aggregation: for the case where MPLS labels are
signaled from the NVEs for MAC/IP Advertisement routes, this
solution provides label aggregation. A remote PE MAY receive a
single label per DC GW MAC-VRF as opposed to a label per NVE.
o The DC GW will not propagate MAC mobility for the MACs moving
within a DC. Mobility intra-DC is solved by all the NVEs in the
DC. The MAC Mobility procedures on the DC GWs are only required in
case of mobility across DCs.
o Proxy-ARP function on the DGWs can be leveraged to reduce ARP
flooding in the DC or/and in the WAN.
3.5. PBB-EVPN DCI for EVPN-Overlay networks
[PBB-EVPN] is yet another DCI option. It requires the use of DC GWs
where I-components and associated B-components are EVI instances.
3.5.1. Control/Data Plane setup procedures on the DC GWs
EVPN will independently run in both components, the I-component EVI
and B-component EVI. Compared to [PBB-EVPN], the DC C-MACs are no
longer learnt in the data plane on the DC GW but in the control plane
through EVPN running on the I-component. Remote C-MACs coming from
remote PEs are still learnt in the data plane. B-MACs in the B-
component will be assigned and advertised following the procedures
described in [PBB-EVPN].
A DCI-ESI will be configured on the DC GWs for multi-homing, but it
will only be used in the EVPN control plane for the I-component EVI.
No ESI will be used in the control plane of the B-component EVI as
per [PBB-EVPN].
The rest of the control plane procedures will follow [EVPN] for the
I-component EVI and [PBB-EVPN] for the B-component EVI.
Rabadan et al. Expires August 18, 2014 [Page 17]
Internet-Draft DCI for E-VPN Overlays February 14, 2014
From the data plane perspective, the I-component and B-component EVPN
bindings established to the same far-end will be compared and the I-
component EVPN-overlay binding will be kept down following the rules
described in section 3.3.1.
3.5.2. Multi-homing procedures on the DC GWs
Single-active as well as all-active multi-homing MUST be supported.
The forwarding behavior of the DF and non-DF will be changed based on
the description outlined in section 3.4.3, only replacing the "WAN
split-horizon-group" for the B-component.
3.5.3. Impact on MAC Mobility procedures
C-MACs learnt from the B-component will be advertised in EVPN within
the I-component EVI scope. If the C-MAC was previously known in the
I-component database, EVPN would advertise the C-MAC with a higher
sequence number, as per [EVPN]. From a Mobility perspective and the
related procedures described in [EVPN], the C-MACs learnt from the B-
component are considered local.
3.5.4. Data Center Gateway optimizations
All the considerations explained in section 3.4.5 are applicable to
the PBB-EVPN DCI option.
5. Conventions and Terminology
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 RFC-2119 [RFC2119].
BUM: it refers to the Broadcast, Unknown unicast and Multicast
traffic
DF: Designated Forwarder
DC GW: Data Center Gateway
DCI: Data Center Interconnect
ES: Ethernet Segment
ESI: Ethernet Segment Identifier
DCI-ESI: ESI defined on the DC GWs for multi-homing to/from the WAN
Rabadan et al. Expires August 18, 2014 [Page 18]
Internet-Draft DCI for E-VPN Overlays February 14, 2014
EVI: EVPN Instance
MAC-VRF: it refers to an EVI instance in a particular node
NVE: Network Virtualization Edge
TOR: Top-Of-Rack switch
VNI/VSID: refers to VXLAN/NVGRE virtual identifiers
6. Security Considerations
This section will be completed in future versions.
7. IANA Considerations
8. References
8.1. Normative References
[RFC4761]Kompella, K., Ed., and Y. Rekhter, Ed., "Virtual Private LAN
Service (VPLS) Using BGP for Auto-Discovery and Signaling", RFC 4761,
January 2007.
[RFC4762]Lasserre, M., Ed., and V. Kompella, Ed., "Virtual Private
LAN Service (VPLS) Using Label Distribution Protocol (LDP)
Signaling", RFC 4762, January 2007.
[RFC6074]Rosen, E., Davie, B., Radoaca, V., and W. Luo,
"Provisioning, Auto-Discovery, and Signaling in Layer 2 Virtual
Private Networks (L2VPNs)", RFC 6074, January 2011.
8.2. Informative References
[E-VPN] Sajassi et al., "BGP MPLS Based Ethernet VPN", draft-ietf-
l2vpn-evpn-05.txt, work in progress, February, 2014
[PBB-EVPN] Sajassi et al., "PBB-EVPN", draft-ietf-l2vpn-pbb-evpn-06,
work in progress, October, 2014
[EVPN-Overlays] Sajassi-Drake et al., "A Network Virtualization
Overlay Solution using EVPN", draft-sd-l2vpn-evpn-overlay-02.txt,
work in progress, October, 2013
Rabadan et al. Expires August 18, 2014 [Page 19]
Internet-Draft DCI for E-VPN Overlays February 14, 2014
9. Acknowledgments
This document was prepared using 2-Word-v2.0.template.dot.
10. Authors' Addresses
Jorge Rabadan
Alcatel-Lucent
777 E. Middlefield Road
Mountain View, CA 94043 USA
Email: jorge.rabadan@alcatel-lucent.com
Senthil Sathappan
Alcatel-Lucent
Email: senthil.sathappan@alcatel-lucent.com
Wim Henderickx
Alcatel-Lucent
Email: wim.henderickx@alcatel-lucent.com
Florin Balus
Nuage Networks
Email: florin@nuagenetworks.net
Senad Palislamovic
Alcatel-Lucent
Email: senad.palislamovic@alcatel-lucent.com
Rabadan et al. Expires August 18, 2014 [Page 20]
