Internet DRAFT - draft-ietf-bess-evpn-modes-interop
draft-ietf-bess-evpn-modes-interop
INTERNET-DRAFT L. Krattiger, Ed.
Intended Status: Informational A. Sajassi, Ed.
Expires: September 9, 2023 S. Thoria
Cisco Systems
J. Rabadan
Nokia
J. Drake
Juniper
March 8, 2023
EVPN Interoperability Modes
draft-ietf-bess-evpn-modes-interop-02
Abstract
Ethernet VPN (EVPN) provides different functional modes in the area
of Service Interface, Integrated Route and Bridge (IRB) and IRB Core
connectivity. This document specifies how the different EVPN
functional modes and types can interoperate with each other. This
document doesn't aim to redefine the existing functional modes but
describe how there is interoperability.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
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http://www.ietf.org/1id-abstracts.html
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Copyright and License Notice
Copyright (c) 2019 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
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Requirements Language . . . . . . . . . . . . . . . . . . . 3
2. Valid Combinations for Interoperability . . . . . . . . . . . 3
3. Service Interface Interoperability . . . . . . . . . . . . . . 5
3.1. VLAN-Aware Bundle and VLAN-Based . . . . . . . . . . . . . 5
3.1.1. VLAN-Aware Bundle Service PE . . . . . . . . . . . . . 6
3.1.2. VLAN-Based Service PE . . . . . . . . . . . . . . . . 7
3.2. Service Interface Interop Mode of Operation . . . . . . . . 7
4. Interoperability for different IRB Types . . . . . . . . . . . 8
4.1. Asymmetric IRB and Symmetric IRB . . . . . . . . . . . . . 8
4.1.1. Asymmetric IRB PE . . . . . . . . . . . . . . . . . . 10
4.1.2. Symmetric IRB PE . . . . . . . . . . . . . . . . . . . 10
4.2. IRB Interop Mode of Operation . . . . . . . . . . . . . . . 11
5. Interoperability for different IRB Core Connectivity Modes . . 13
5.1. Interface-Less and Interface-Ful Unnumbered IRB . . . . . 13
5.1.1. Interface-Less PE . . . . . . . . . . . . . . . . . . 15
5.1.2. Interface-Ful Unnumbered IRB . . . . . . . . . . . . . 15
5.2. Tunnel Encapsulation Consideration . . . . . . . . . . . . 17
6. Security Considerations . . . . . . . . . . . . . . . . . . . 17
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
8.1. Normative References . . . . . . . . . . . . . . . . . . . 18
8.2. Informative References . . . . . . . . . . . . . . . . . . 18
9. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 19
9.1. Demonstration of Applicability . . . . . . . . . . . . . . 19
9.1.1. Service Interface Interoperability . . . . . . . . . . 19
9.1.2. IRB Types . . . . . . . . . . . . . . . . . . . . . . 19
9.1.3. IRB Core Connectivity Types . . . . . . . . . . . . . 20
10. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 20
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1. Introduction
Ethernet VPN (EVPN) provides different functional modes in the area
of Service Interface, Integrated Route and Bridge (IRB) and IRB
connection model. It is understood that the different modes are
defined with different use-cases in mind. Even with the specific use-
cases and the resulting mode definition, the aim of interoperability
is critical.
The following EVPN modes are considered for interoperability. It is
limited to the most pertinent interop modes as oppose to all
permutations.
- For Service Interfaces, the VLAN Aware Bundle and VLAN Based types.
- In Integrated Routing and Bridging (IRB) the Asymmetric IRB and
Symmetric IRB type.
- Within the IRB connectivity types, interface-less and the
interface-ful Unnumbered IRB.
Future revisions of this Internet-Draft might address further
variations of interoperability.
1.1 Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Valid Combinations for Interoperability
The tables below provide an overview of the valid combinations for
interoperability described in this Internet-Draft.
For the Service Interface Types as described in [RFC7432] section 6
and [RFC8365] section 5.1.2. Interoperability considerations are
provided for the VLAN-Based Service interface ([RFC7432], section
6.1) and the VLAN-Aware Bundle Service Interface type ([RFC7432]
section 6.3). The VLAN Bundle Service Interface ([RFC7432] section
6.2) is not considered at this time.
Table 1 represent the considered Service Interface Types
interoperability:
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+-------------------+------------+-------------+--------------------+
| | VLAN-Based | VLAN Bundle | VLAN-Aware Bundle |
+-------------------+------------+-------------+--------------------+
| VLAN-Based | YES | NO | YES |
+-------------------+------------+-------------+--------------------+
| VLAN Bundle | NO | YES | NO |
+-------------------+------------+-------------+--------------------+
| VLAN-Aware Bundle | YES | NO | YES |
+-------------------+------------+-------------+--------------------+
Table 1
In regards to Integrated Route and Bridge (IRB), two different modes
are defined in [RFC9135], with section 5 describing Symmetric IRB and
section 6 Asymmetric IRB:
The interoperability considerations between both IRB modes,
Asymmetric IRB and Symmetric IRB, are represented within this
Internet-Draft.
For the IRB Core Connectivity, from all the available modes defined
in [RFC9136], considered for interoperability is the interface-less
mode (section 4.4.1) in conjunction with only one of the interface-
ful modes, namely interface-ful IP-VRF-to-IP-VRF with Unnumbered SBD
IRB (section 4.4.3). The close functional proximation between the two
interface-ful modes, considerations for interoperability between
interface-less and interface-ful Numbered are currently not
considered. Similarly, the interoperability between the two
interface-ful modes is currently not being considered, given the
close functional relation and to limit permutations. Future revisions
of this Internet-Draft might address further variations of
interoperability.
Table 2 represent the considered IRB Core Connectivity
interoperability.
+-----------------+----------------+---------------+----------------+
| | Interface-Less | Interface-Ful | Interface-Ful |
| | | Numbered IRB | Unnumbered IRB |
+-----------------+----------------+---------------+----------------+
| Interface-Less | YES | NO | YES |
+-----------------+----------------+---------------+----------------+
| Interface-Ful | NO | YES | NO |
| Numbered IRB | | | |
+-----------------+----------------+---------------+----------------+
| Interface-Ful | YES | NO | YES |
| Unnumbered IRB | | | |
+-----------------+----------------+---------------+----------------+
Table 2
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3. Service Interface Interoperability
3.1. VLAN-Aware Bundle and VLAN-Based
[RFC7432] section 6 describes three different Service Interface
Types. The two modes in focus for interoperability are namely the
VLAN-Based Service Interface as defined in [RFC7432] section 6.1 and
the VLAN-Aware Bundle Service Interface as defined in [RFC7432]
section 6.3. The VLAN Bundle Service Interface is not considered.
The VLAN-Based Service Interface defines an EVPN instance consisting
of only a single broadcast domain, or "Single Broadcast Domain per
EVI", as defined in [RFC8365] section 5.1.2 Option 1. In this mode,
individual BGP Route Distinguisher (RD) and Route Target (RT) are
required for each EVI. Each EVI corresponds to a single MAC-VRF
identified by the RT. This mode has the the advantage of an BGP RT
constraint mechanisms in order to limit the propagation and import of
routes to only the PE that are interested. With VLAN-Based, the MAC-
VRF corresponds to only a single bridge table. The VLAN-Based Service
Interface uses the EVPN MAC/IP Advertisement route ([RFC7432],
section 7.2) with the MUST requirement of the Ethernet Tag ID being
set to zero.
Differently, the VLAN-Aware Bundle Service Interface follows a
bundling of multiple broadcast domains, with each having its own
bridge table, into a single EVI. This refers to the definition of
"Multiple Broadcast Domain per EVI" as described in [RFC8365] section
5.1.2 Option 2. The advantage of this model allows a single RD/RT per
broadcast domain, which is a moot point when VLAN-Base uses auto-
derivation of RD/RT. With VLAN-Aware Bundle Service, RT Constraint,
as defined in [RFC4684], does not help to reduce the dissemination of
routes for a BD to the PEs attached to that BD. This is given by the
nature of the bundle service where the RT is not sufficient to
identify the MAC-VRF and corresponding bridge table. The differences
between the two modes of Service Interfaces, namely VLAN-Based and
VLAN-Aware Bundle Service Interface, is in the definition of the
Ethernet Tag field within the EVPN routes. While VLAN-Based Service
Interface defines the EtherTag as "must be set to zero", the VLAN-
Aware Bundle Service interface uses the VID within the EtherTag to
identify the bridge table within the MAC-VRF. These two requirements
are orthogonal and as a result make the interoperability of the two
types mutually exclusive, an interoperability is not achievable
(Figure 1).
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VLAN-Aware Bundle VLAN-Based
Service Interface Service Interface
+--------------------------+ +--------------------------+
| PE1 | | PE2 |
| +---------+ +--------+ | | +--------+ +---------+ |
| | +-----+ | | | | | | | | | |
+-----| BD2 | +--+ | |--------| | +--+ |---+
|| | +-----+ | | | | | | | | | ||
|| | | | | | | | | | | ||
|| |MAC-VRF1 | |IP-VRF1 | | | |IP-VRF1 | |MAC-VRF1 | ||
|| +---------+ +--------+ | | +--------+ +---------+ ||
|| | | ||
|| +-----+ | | +-----+ ||
|| | BGP | | | | BGP | ||
|| +-----+ | | +-----+ ||
|+--------------------------+ +--------------------------+|
| 2|EthTag [2]| -----><----- 2|EthTag [0]| |
| |
| +------+ +------+ |
+-|M1/IP1! |M2/IP2!-+
+------+ +------+
Figure 1: Interop of different Service Interface Types
As illustrated in Figure 1, the MAC/IP routes exchanged by PE1 and
PE2 contain Ethernet Tags 2 and 0 respectively. The receiving PE will
not process these routes and will normally discard them (treat-as-
withdraw)."
By extending the requirements currently present, an interoperability
is achievable. The adjustment would be as follows.
3.1.1. VLAN-Aware Bundle Service PE
In case of VLAN Aware Bundle Service Interface on the receiving PE
and with the consideration of VLAN Based Service Interface on the
advertising PE:
- MUST Operate in Single Broadcast Domain per EVI.
- Multiple Broadcast Domain per EVI case is not considered.
- Must allow to send and receive zero EtherTag.
- The import of routes is performed based on the import policy
(route-target).
- With single bridge table per MAC-VRF, additional evaluation of the
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EtherTag field is not required; the bridge table is sufficiently
defined by the import route-target. Using a single MAC-VRF with per-
BD route-target would deviate from the VLAN-Based Service Interface
and would create a new interoperability permutation.
- No Change to data-plane operation, the MPLS label identifies MAC-
VRF + bridge-table, or the VNI identifies the MAC-VRF + the bridge-
table.
3.1.2. VLAN-Based Service PE
- Operates in Single Broadcast Domain per EVI.
In case of VLAN Based Service Interface on the receiving PE and with
the consideration of VLAN Based Service Interface on the advertising
PE:
- Operates in Single Broadcast Domain per EVI.
- MUST allow receiving of non-zero EtherTag.
- No Change in control-plane operation, the EVI import policy (route-
target) identifies the broadcast domain (bridge-table) within a MAC-
VRF.
- No Change to data-plane operation, the MPLS label identifies MAC-
VRF + bridge-table, or the VNI identifies the MAC-VRF + the bridge-
table.
While the expansion introduces additional configuration requirement
for the VLAN-Aware Bundle Service Interface, it also allows for
broader interoperability in the eventuality of Vendor "A" only
implemented VLAN-Based while Vendor "B" only implemented VLAN-Aware
Bundle Service Interface.
3.2. Service Interface Interop Mode of Operation
When Service Interface interoperability is required, a given PE
should follow this section's procedures for all its broadcast domains
(BDs) and not just the BDs that need interoperability.
For those BDs where interoperability between VLAN-Aware Bundle and
VLAN-Based Service Interface is needed, ignoring the presence of the
EVPN routes Ethernet Tag ID on the PEs supporting VLAN-Based mode is
not enough. Each PE needs to clearly signal what mode it supports, so
that all the PEs attached to the same EVI can understand in what mode
the EVI operates.
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Consider a scenario where PE1 is attached to the BD range BD1-10 and
it operates in VLAN-Aware mode, whereas PE2 is attached to the BD
range BD7-20 and operates in VLAN-Based mode. Interoperability is
required for the intersecting BDs, I.e., BD7-10.
For PE1, this means BD7-10 need to be separated into a dedicated MAC-
VRF each. EVPN routes for each of these four MAC-VRFs MUST be
advertised by PE1 with an Ethernet Tag ID of zero. In this way, PE1
indicates the use of VLAN-Based mode for those BDs. On reception, PE1
imports the BD7-10 routes based on the Route Target and ignoring the
Ethernet Tag ID, as the Route Target alone is sufficient to identify
the correct MAC-VRF and Bridge Table. The remaining BDs on PE1 (range
BD1-6) continue operating in VLAN-Aware Bundle mode.
In the same example, other PEs attached to BD1-6 must still process
the received Ethernet Tag ID in the EVPN routes from PE1, so that
they can identify the correct Bridge Table in a given MAC-VRF.
PE2 operates in VLAN-Based mode for BD7-20, as per [RFC7432] and
[RFC8365]. PE2's EVPN route advertisements for BD7-20 will include
individual Route Targets per BD and an Ethernet Tag ID of zero. On
reception, PE2 identifies the MAC-VRF and Bridge Table solely based
on the Route Target.
4. Interoperability for different IRB Types
4.1. Asymmetric IRB and Symmetric IRB
The differences in the two inter-subnet forwarding modes, namely
Asymmetric IRB and Symmetric IRB, are beyond just the information
difference in the control-plane from an EVPN Route Type 2 perspective
(EVPN MAC/IP Advertisement route). The two IRB modes have significant
differences in inter-subnet forwarding behavior and as a result
different operation during label imposition or encapsulation.
With the Asymmetric IRB mode, the ingress PE performs a "bridge-and-
route" operation while the egress PE follows a "bridge-only"
approach. Differently, the forwarding behavior in Symmetric IRB mode
performs a "bridge-and-route" operation on the ingress PE followed by
a "route-and bridge" operation at the egress PE. The significance in
difference is not only in the forwarding behavior itself but also
around how the respective EVPN attribute are used for driving the
inter-subnet operation. More specifically, in the case of inter-
subnet forwarding with Asymmetric IRB, next to the MAC and IP address
present in the EVPN Route Type 2, only MPLS Label1 is used towards
the egress PE to specify the MAC-VRF and respective Bridge-Domain for
forwarding. In inter-subnet forwarding with Symmetric IRB, next to
the MAC and IP address present in the EVPN Route Type 2, MPLS Label2
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associated with the IP-VRF is used for the inter-subnet forwarding
operation towards egress PE. To facilitate interoperability between
Asymmetric and Symmetric IRB, the usage of EVPN Route Type 2 with
both MAC and IP address populated is considered. This is to not expand
the requirement of additional capability exchange between PEs.
Complementing Asymmetric IRBs absence of MPLS Label2 with a EVPN
Route Type 5 (IP Prefix Advertisement) is not part of this procedure.
The respective forwarding behaviors are described in [RFC9135]. The
following steps are required to ensure the interoperability between
the Asymmetric and Symmetric IRB modes.
Asymmetric IRB Symmetric IRB
+--------------------------+ +--------------------------+
| PE1 | | PE2 |
| +---------+ | | +---------+ |
| | +-----+ | | | | +-----+ | |
+-----| BD0 | +-IRB0-+ | | +-IRB0--+ | BD0 | | |
|| | +-----+ | | | | | | +-----+ | |
|| | | +---+----+ | | +---+----+ | | |
|| |MAC-VRF1 | | | | | | | |MAC-VRF1 | |
|| +---------+ |IP-VRF1 | |--------| |IP-VRF1 | +---------+ |
|| | | | | | | |
|| +---------+ +---+----+ | | +---+----+ +---------+ |
|| | +-----+ | | | | | | +-----+ | |
|| | | BD2 | +-IRB2-+ | | +-IRB2--+ | BD2 |-----+
|| | +-----+ | | | | +-----+ | ||
|| | | +-----+ | | +-----+ | | ||
|| |MAC-VRF2 | | BGP | | | | BGP | |MAC-VRF2 | ||
|| +---------+ +-----+ | | +-----+ +---------+ ||
|| | | ||
|+--------------------------+ +--------------------------+|
| 2|MAC/IP, 1 Label| -----><----- 2|MAC/IP, 2 Label| |
| |
| +------+ +------+ |
+-|M1/IP1! |M2/IP2!-+
+------+ +------+
Figure 2: Asymmetric IRB and Symmetric IRB
Figure 2 illustrates the overview of and Asymmetric IRB PE (PE1) and
a Symmetric IRB PE (PE2) within a interoperability deployment
scenario. Attached to PE1, end-point M1/IP1 is attached to BD0 within
MAC-VRF1. Respectively, on PE2 end-point M2/IP2 is connected via
attachment circuit to BD2 positioned within MAC-VRF2. IRB0 and IRB2
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represent the host-facing IRB interface for inter-subnet
communication between the end-points located in the different IP
Subnet. The IRB interfaces for a common MAC-VRF/BD on PE1 and PE2 use
the same IP address. With the IRB modes on PE1 being Asymmetric IRB
and PE2 being Symmetric IRB, the MPLS Label fields, as part of the
MAC/IP routes exchanged between the PEs, are different. PE1s update
contains a single label, representing MPLS Label1 used for bridging
purposes. PE2s advertisement contains two labels, one for bridging
and one for routing, as part of the MAC/IP route. While PE1 receives
all information necessary from PE2, PE2 is missing information
necessary for its routing operation. As a result, Inter-Subnet
routing between PE1 and PE2 is not achieved.
By following the current existing forwarding behavior as described in
[RFC9135], interoperability is theoretically achievable without
changes in the control-plane format. Nevertheless, there are
additional steps required that involves the local forwarding behavior
of the PE with Symmetric IRB mode.
4.1.1. Asymmetric IRB PE
In case of Asymmetric IRB as the advertising PE and with Symmetric
IRB on the receiving PE:
- Asymmetric IRB PE MUST send MAC and IP information with MPLS Label1
as described in [RFC9135].
In case of Symmetric IRB as the advertising PE and with Asymmetric
IRB on the receiving PE:
- Asymmetric IRB PE MUST be able to ignore MPLS Label2; [RFC9135]
already considers this.
4.1.2. Symmetric IRB PE
In case of Symmetric IRB as the advertising PE and with Asymmetric
IRB on the receiving PE:
- Symmetric IRB PE has no additional requirements.
In case of Asymmetric IRB as the advertising PE and with Symmetric
IRB on the receiving PE:
- Symmetric IRB PE requires to add the host-binding information, MAC
and IP, and associates them to the adjacency (ARP/ND) table facing
the PE with Asymmetric IRB; this is in addition of adding the MAC
address into the MAC-VRF table, using MPLS Label1. Since there is no
MPLS Label2 or Route-Target for the IP-VRF, the Host IP is not
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specifically added to IP-VRF table.
- Symmetric IRB PE must have defined all BD, MAC-VRF and IRB
interfaces of the Asymmetric IRB PE.
4.2. IRB Interop Mode of Operation
Interoperability between the Asymmetric IRB and Symmetric IRB mode
follows specific defined behavior that is predominantly required on
the PE that operates in the Symmetric IRB mode. Nevertheless, in
support for the interoperability, the PE operating in Asymmetric IRB
must accommodate the following two minimum requirements (with
references to Figure 2):
1) The PE that operates in Asymmetric IRB mode (PE1), MUST send the
MAC/IP route including the Host IP address and only MPLS Label1.
2) The PE with Asymmetric IRB (PE1) must accept the MAC/IP routes
sent from PE2 (Symmetric IRB), while ignoring the additional
information of MPLS Label2 and Route-Target of the IP-VRF.
In reference to 1), the PE MUST always send the end-point MAC
address, Host IP address and related MPLS Label1 as part of the
MAC/IP route towards the PE with Symmetric IRB (PE2). This route will
be sent only with MPLS Label1 and the Route-Target of the matching
MAC-VRF to achieve bridging. In reference to the illustration in
Figure 2, PE1 must generate and advertise an EVPN MAC/IP route using:
- MAC Length of 48
- MAC Address of M1
- IP Length of 32 / 128
- IP Address of IP1
- Label for MAC-VRF1
- Route-Target of MAC-VRF1
- Next-Hop PE1
For completeness of the requirements and in reference of 2), the
MAC/IP route advertised from the PE operating in Symmetric IRB (PE2)
is as follow:
- MAC Length of 48
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- MAC Address of M2
- IP Length of 32 /128
- IP Address of IP2
- Label for MAC-VRF2, IP-VRF1
- Route-Target of MAC-VRF2, IP-VRF1
- Next-Hop PE2
As defined in 2), the Label and Route-Target information for IP-VRF1
MUST be ignored by PE1 (PE with Asymmetric IRB).
With PE2 operating in Symmetric IRB and with enabled interop mode,
the MAC/IP route from PE1 (Asymmetric IRB) is processed in the
respective bridging, routing and adjacency table. Based on the Route-
Target for MAC-VRF1, the MAC address M1 will be imported into MAC-
VRF1 respectively and placed within BD0. In addition, the host-
binding information M1/IP1 MUST be installed within PE2s adjacency
table. Subsequent, on PE2 the MAC address M1 and the host-binding
information (adjacency table entry) of M1/IP1 MUST point towards PE1
as the next-hop. With no presence of the Route-Target for IP-VRF1,
the IP address IP1 will not be specifically imported into IP-VRF1 and
is not associated with a MPLS Label2. As a result of the
interoperability, the additional efficiency provided by Symmetric IRB
in regards of preserving adjacency table exhaustion is reduced; this
is specifically when communicating with an Asymmetric IRB based
egress PE. In contrary, the interop mode allows for communication
between the different IRB modes. As a result, in the eventuality that
Vendor "A" only provides Asymmetric IRB, while Vendor "B" only has
Symmetric IRB available, interoperability for inter-subnet forwarding
can be seamlessly achieved. In addition, two further benefits are
present by implementing an Asymmetric/Symmetric Co-Existence on the
same PE (dual-mode PE).
- A dual-mode PE can seamlessly communicate with PE's that are either
in Asymmetric or in Symmetric IRB mode.
- A dual-mode PE can act as Anchor for interconnecting Symmetric IRB
and Asymmetric IRB based PE's (deployment restrictions might apply).
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5. Interoperability for different IRB Core Connectivity Modes
5.1. Interface-Less and Interface-Ful Unnumbered IRB
The two modes, namely interface-less and interface-ful Unnumbered SBD
IRB, are closely related in regards to the information required in
the EVPN Route Type 5. While interface-less provides all information
for the IP prefix advertisement within the EVPN Route Type 5, in the
case of interface-ful Unnumbered SBD IRB, an additional EVPN Route
Type 2 is required for the next-hop recursive lookup. From a
forwarding behavior, both approaches are similar and follow a
symmetric routing approach but are not interoperable. Note as per
[RFC9136] the interface-ful Unnumbered SBD IRB is an OPTIONAL mode.
Interface-Ful
Interface-Less Unnumbered IRB
+--------------------------+ +--------------------------+
| PE1 | | PE2 |
| +--------+ | | +--------+ |
| | | | | | | |
+----------------+ | |--------| | +----------------+
|| | | | | | | ||
|| | | | | | | ||
|| |IP-VRF1 | | | |IP-VRF1 | ||
|| +--------+ | | +--------+ ||
|| | | ||
|| +-----+ | | +-----+ ||
|| | BGP | | | | BGP | ||
|| +-----+ | | +-----+ ||
|+--------------------------+ +--------------------------+|
| 2|None| -----> |
| <----- 5|No Label| |
| |
| +-------+ +-------+ |
+-|TS1/SN1| |TS2/SN2!-+
+-------+ +-------+
Figure 3: Interoperability of different IRB Core Connectivity Mode
(unnumbered)
The illustration in Figure 3 represents the possible deployment
scenario between two different Core IRB Connectivity modes.
Specifically, PE1 is operating with interface-less Core IRB Mode
while PE2 operates with the interface-ful Unnumbered SDB IRB mode;
both operate without interoperability capabilities. Attached to PE1
and PE2 respectively, Tenant System 1 (TS1) and Tenant System 2 (TS2)
with different IP Subnet are present. TS1 attached on PE1 as well as
TS2 attached to PE2 are represented in a common IP-VRF (IP-VRF1),
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sharing a common Route-Target between the PEs. With the different IRB
Core Connectivity modes on PE1 and PE2 respectively, the differences
in IP prefix advertisements as described in [RFC9136] are present.
PE1 advertises only a single EVPN Route Type 5 (IP Prefix Route) for
TS1 using the fields following the interface-less mode:
EVPN Route Type 5:
- IP Length of 0 to 32 / 0 to 128
- IP Address of SN1
- Label for IP-VRF1
- GW IP Address set to zero
- Route-Target of IP-VRF1
- Router's MAC Extended Community of PE1
- Next-Hop PE1
Differently, PE2 advertises an EVPN Route Type 2 (MAC/IP Route) next
to the EVPN Route Type 5 (IP Prefix Route). The MAC/IP Route supports
the requirement for recursive next-hop resolution for the next-hop
used in the IP Prefix Route. Below the fields used in the Route Type
5 and respective Route Type 2 according to the interface-ful
Unnumbered IRB mode:
EVPN Route Type 5:
- IP Length of 0 to 32 / 0 to 128
- IP Address of SN1
- Label SHOULD be set to 0
- GW IP Address SHOULD be set to zero
- Route-Target of IP-VRF1
- Router's MAC Extended Community of PE2
- Next-Hop PE2
EVPN Route Type 2:
- MAC Length of 48
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- MAC Address of PE2
- IP Length of 0
- Label for IP-VRF1
- Route-Target of IP-VRF1
- Next-Hop PE2
While PE1 is missing the MPLS Label for the IP-VRF from PE2, PE2 is
missing the MPLS Label information and the necessary info for the
next-hop recursion. As a result, Routing with IP Prefix Advertisement
between PE1 and PE2 is not achieved.
By advertising an additional EVPN Route Type 2 from interface-less
(PE1) and by advertising the MPLS Label as part of EVPN Route Type 5
from PE2, interoperability is achievable. The specific mode of
operation would be as per the following two section and refers to
Figure 3 and Figure 4.
5.1.1. Interface-Less PE
In case of interface-less on the advertising PE and with the
consideration of interface-ful Unnumbered IRB as the receiving PE:
Shall generate and Advertise EVPN Route Type 2 for every IP-VRF
using.
- MAC Length of 48
- MAC Address with "Router MAC"
- IP Length of 0
- Label for IP-VRF
- Route-Target of IP-VRF
In case of interface-less on the receiving PE and with the
consideration of interface-ful Unnumbered IRB as the advertising PE:
- MUST ignore EVPN Route Type 2 with MPLS Label and route-target
matching the IP-VRF because there is no MAC-VRF defined matching
these information.
5.1.2. Interface-Ful Unnumbered IRB
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In case of interface-ful Unnumbered on the advertising PE and with
the consideration of interface-less as the receiving PE:
- Shall advertise MPLS Label for IP-VRF in EVPN Route Type 5 with
matching route-target.
In case of interface-ful Unnumbered on the receiving PE and with the
consideration of interface-less as the advertising PE:
- No Additions Required.
Interface-Ful
Interface-Less Unnumbered IRB
+--------------------------+ +--------------------------+
| PE1 | | PE2 |
| +--------+ | | +--------+ |
| | | | | | | |
+----------------+ | |--------| | +----------------+
|| | | | | | | ||
|| | | | | | | ||
|| | IP-VRF | | | | IP-VRF | ||
|| +--------+ | | +--------+ ||
|| | | ||
|| +-----+ | | +-----+ ||
|| | BGP | | | | BGP | ||
|| +-----+ | | +-----+ ||
|+--------------------------+ +--------------------------+|
| 2|RMAC/RIP| -----> |
| <----- 5|Label| |
| |
| +-------+ +-------+ |
+-|TS1/SN1| |TS2/SN2!-+
+-------+ +-------+
Figure 4: Interop of different IRB Core Connectivity Types
(unnumbered)
Illustrated in Figure 4 are the additional requirements for
interface-less IRB Core Connectivity mode, specifically the MAC/IP
Route (EVPN Route Type 2) necessary for PE2s next-hop recursion.
Also, the MPLS Label addition within PE2s IP Prefix route (EVPN Route
Type 5) is represented, which is required for interface-ful
Unnumbered IRBs advertisement towards an interface-less PE (PE1)
The interop mode introduces additional control-plane advertisements
from an Interface-less perspective. This is necessary to allow
interface-ful Unnumbered SBD IRB to perform the recursive lookup
required. From a EVPN Type 5 perspective between the two types, most
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of the fields are already equally defined and populated as per
[RFC9136]. Exception is the IP-VRF Label, which is required to be
added in the interface-ful Unnumbered SBD IRB's EVPN Type 5. In
addition, the Interface-less addition allows the Co-Existence of both
types on the same PE (dual-mode PE). Such a dual-mode PE can
communicate at the same time with PE's that are in Interface-less or
in interface-ful Unnumbered SBD IRB mode.
The disadvantage of the additional advertisement has to be put into
relation to advantage of successful interoperability where eventualy
Vendor "A" only implemented interface-less while Vendor "B" only
implemented interface-ful Unnumbered SBD IRB.
5.2. Tunnel Encapsulation Consideration
In regards to IRB core connectivity both solutions, namely interface-
less and interface-ful, provide a solution for Layer 3 connectivity
among the IP-VRFs. Even as the functional result of both modes is the
same, there are important considerations in regards to tunnel
encapsulations.
[RFC9135] section 4 considers the choice for the NVO tunnel should be
dictated by the tunnel capabilities. For example for the IP-VRF-to-
IP-VRF model with interface-less, the NVO tunnel for MPLS needs to be
IP NVO and for VXLAN needs to be Ethernet NVO.
With the "IP-VRF-to-IP-VRF" model that is used in interface-ful
(numbered or unnumbered), section 4.4.2 or 4.4.3 respectively
describe the solution to accommodate Ethernet NVO tunnels (VXLAN or
GPE, GENEVE, MPLS with MAC payload) only. In the case of interface-
ful unnumbered, the Router-MAC Extended Community is always signaled
via EVPN update message, which implies the presence of a MAC payload.
IP NVO Tunnel are not applicable to these two use-cases/models
Depending on the use of NVO tunnels, interoperability between
interface-les and interface-ful unnumbered requires additional
changes on the Tunnel Encapsulation mode. This Internet-Draft
considers the usage of a compatible NVO Tunnel mode between a PE
operating in interface-les and a PE operating nterface-ful unnumbered
mode.
6. Security Considerations
TBD.
7. IANA Considerations
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TBD.
8. References
8.1. Normative References
[RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
2015, <https://www.rfc-editor.org/info/rfc7432>.
[RFC8365] Sajassi, A., Ed., Drake, J., Ed., Bitar, N., Shekhar, R.,
Uttaro, J., and W. Henderickx, "A Network Virtualization
Overlay Solution Using Ethernet VPN (EVPN)", RFC 8365, DOI
10.17487/RFC8365, March 2018, <https://www.rfc-
editor.org/info/rfc8365>.
[RFC9135] Sajassi et al., "Integrated Routing and Bridging in
Ethernet VPN (EVPN)", RFC9135, DOI 10.17487 , October,
2021, <https://www.rfc-editor.org/info/rfc9135>.
[RFC9136] Rabadan et al., "IP Prefix Advertisement in Ethernet VPN
(EVPN)", RFC9136, DOI 10.17487 , October, 2021,
<https://www.rfc-editor.org/info/rfc9136>.
[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI
10.17487/RFC2119, March 1997, <http://www.rfc-
editor.org/info/rfc2119>.
[RFC1776] Crocker, S., "The Address is the Message", RFC 1776, DOI
10.17487/RFC1776, April 1 1995, <http://www.rfc-
editor.org/info/rfc1776>.
[TRUTHS] Callon, R., "The Twelve Networking Truths", RFC 1925, DOI
10.17487/RFC1925, April 1 1996, <http://www.rfc-
editor.org/info/rfc1925>.
8.2. Informative References
[RFC4684] Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk, R.,
Patel, K., and J. Guichard, "Constrained Route
Distribution for Border Gateway Protocol/MultiProtocol
Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual
Private Networks (VPNs)", RFC 4684, DOI 10.17487/RFC4684,
November 2006, <https://www.rfc-editor.org/info/rfc4684>.
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[EANTC] EANTC, "Multi-Vendor Interoperability Test", February 2019,
<http://www.eantc.de/fileadmin/eantc/downloads/News/2019/EANTC-
MPLSSDNNFV2019-WhitePaper-v1.2.pdf>.
[EVILBIT] Bellovin, S., "The Security Flag in the IPv4 Header",
RFC 3514, DOI 10.17487/RFC3514, April 1 2003,
<http://www.rfc-editor.org/info/rfc3514>.
[RFC5513] Farrel, A., "IANA Considerations for Three Letter
Acronyms", RFC 5513, DOI 10.17487/RFC5513, April 1 2009,
<http://www.rfc-editor.org/info/rfc5513>.
[RFC5514] Vyncke, E., "IPv6 over Social Networks", RFC 5514, DOI
10.17487/RFC5514, April 1 2009, <http://www.rfc-
editor.org/info/rfc5514>.
9. Conclusion
With minimal additions, the most common EVPN types for Virtual
Identifiers to EVI Mapping, Integrated Routing and Bridging and IP
Prefix Advertisement can be made interoperable. The aim for
interoperability doesn't remove the requirement for optimized types
for different use-cases but allows flexibility and basic
interoperability.
9.1. Demonstration of Applicability
Cisco, Juniper and Nokia demonstrated successfully the ability of
EVPN interoperability modes during EANTCs yearly "Multi-Vendor
Interoperability Test". The Whitepaper can be obtained through EANTC
with the latest version being available at [EANTC].
9.1.1. Service Interface Interoperability
A proof of the benefit with this interoperability mode has already
been demonstrated during EVPN Multi-Vendor interoperability testing
and also, in production environments. Specifically, Cisco and Nokia's
VLAN-Based Service Interface successful proofed interoperability with
Junipers VLAN-Aware Bundle Service Interface.
9.1.2. IRB Types
A proof of the benefit with this interoperability mode has already
successfully demonstrated during EVPN Multi-Vendor interoperability
testing. Specifically, Cisco operated in a Hybrid IRB (Dual-Mode)
mode while other Vendor operated in an Asymmetric IRB mode.
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Forwarding was achieved through dynamic detection of the alternate
Vendor PE's mode and adjustment to Asymmetric IRB for these specific
BDs. Communication for all other BDs continued to be Symmetric IRB.
9.1.3. IRB Core Connectivity Types
A proof of an interoperability mode between interface-less and
interface-ful Unnumbered SBD IRB has already been demonstrated in
production environments and during EVPN Multi-Vendor interoperability
testing. Specifically, Cisco's addition for Interface-less is
successfully deployed with Nokia's and Nuage's interface-ful
Unnumbered SBD IRB at customers
10. Authors' Addresses
Lukas Krattiger
Cisco
USA
EMail: lkrattig@cisco.com
Ali Sajassi
Cisco
USA
EMail: sajassi@cisco.com
Samir Thoria
Cisco
USA
EMail: sthoria@cisco.com
Jorge Rabadan
Nokia
EMail: jorge.rabadan@nokia.com
John E. Drake
Juniper
EMail: jdrake@juniper.net
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