Internet DRAFT - draft-wang-bess-l3-accessible-evpn
draft-wang-bess-l3-accessible-evpn
BESS Working Group W. Wang
Internet-Draft A. Wang
Intended status: Standards Track China Telecom
Expires: 9 September 2023 H. Wang
Huawei Technologies
8 March 2023
Layer-3 Accessible EVPN Services
draft-wang-bess-l3-accessible-evpn-05
Abstract
This draft describes layer-3 accessible EVPN service interfaces
according to [RFC7432], and proposes a new solution which can
simplify the deployment of layer-3 accessible EVPN service. This
solution allows each PE in EVPN network to maintain only one IP-VRF.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 9 September 2023.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Service Interfaces in layer-3 accessible EVPN . . . . . . . . 4
5. Solutions of LSI-aware bundle service interface . . . . . . . 6
6. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 7
6.1. Forwarding Plane . . . . . . . . . . . . . . . . . . . . 7
6.1.1. Extensions to VxLAN . . . . . . . . . . . . . . . . . 7
6.2. Control Plane . . . . . . . . . . . . . . . . . . . . . . 7
7. Modification of MAC/IP address storage mode on PE . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
10. Normative References . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
[RFC7432]defines three service interfaces for layer-2 accessible
EVPN: VLAN-Based Service Interface, VLAN-Bundle Service Interface and
VLAN-Aware Bundle Service Interface. These three types of service
interfaces can realize the isolation of layer-2 traffic of customers
in different ways, as shown in Figure 1.
1:1 1:1
+------+ +---------+ +------+
|VID 11+---+ EVI 1 +---+VID 12|
+------+ +---------+ +------+
|VID 21+---+ EVI 2 +---+VID 22|
+------+ +---------+ +------+
|VID 31+---+ EVI 3 +---+VID 32|
+------+ +---------+ +------+
|VID 41+---+ EVI 4 +---+VID 42|
+------+ +---------+ +------+
VLAN-based Service Interface
N:1 1:N
+------+ +---------+ +------+
|VID 11---------+ +--------+VID 12|
+------+ + + +------+
|VID 21+--------+ +--------+VID 22|
+------+ + EVI 1 + +------+
|VID 31+--------+ +--------+VID 32|
+------+ + + +------+
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|VID 41+--------+ +--------+VID 42|
+------+ +---------+ +------+
VLAN-bundle Service Interface
N:1 1:N
+----------------------+
+------+ |+--------------------+| +------+
|VID 11+--++ Broadcast Domain 1 ++--+VID 12|
+------+ |+--------------------+| +------+
|VID 21+--++ Broadcast Domain 2 ++--+VID 22|
+------+ |+--------------------+| +------+
|VID 31+--++ Broadcast Domain 3 ++--+VID 32|
+------+ |+--------------------+| +------+
|VID 41+--++ Broadcast Domain 4 ++--+VID 42|
+------+ |+--------------------+| +------+
| |
| EVI 1 |
+----------------------+
VLAN-Aware Bundle Service Interface
Figure 1: EVPN Service Interfaces Overview
For VLAN-based service interface, there is a one to one mapping
between VID and EVI. Each EVI has a single broadcast domain so that
traffic from different customers can be isolated.
For VLAN-bundle service interface, there is a N to one mapping
between VID and EVI. Each EVI has a single broadcast domain, but the
MAC address MUST be unique that can be used for customer traffic
isolation.
For VLAN-aware bundle service interface, there is a N to one mapping
between VID and EVI. Each EVI has multiple broadcast domains while
the MAC address can overlap. One broadcast domain corresponds to one
VID, which can be used to customer traffic isolation.
In the scenarios corresponding to these service interfaces, CE-PE
should be placed in the same Layer-2 network. In most of provider
network, CE-PE need to cross a Layer-3 network, then the above
service interfaces should be extended to adapt to the layer-3
network.
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In this draft, we describe three layer-3 accessible interfaces for
EVPN, summarize the existing layer-3 accessible EVPN solutions, and
propose a new solution which can simplify the depolyment of layer-3
accessible EVPN service.
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119] .
3. Terminology
The following terms are defined in this draft:
* CE: Client Edge
* PE: Provider Edge
* EVPN: BGP/MPLS Ethernet VPN, defined in [RFC7432]
* VxLAN: Virtual eXtensible Local Area Network, defined in [RFC7348]
* IPSec: Internet Protocol Security, defined in [RFC4301]
4. Service Interfaces in layer-3 accessible EVPN
In most of provider network, CE-PE need to cross a Layer-3 network.
With this scenario, service interfaces defined in [RFC7432] should be
extended to adapt to the layer-3 network. To achieve the traffic
isolation, tunnel encapsulation technologies can be used.
We define Logical Session Identifier(LSI) to distinguish the packets
from different tunnels, which is related to VNI/SPI. The length of
LSI is 16 bits.
The layer-3 accessible interfaces for EVPN are shown in Figure 2,
refer to [RFC7432]
1:1 1:1
+------+ +---------+ +------+
|LSI 11+---+ IP-VRF1 +---+LSI 12|
+------+ +---------+ +------+
|LSI 21+---+ IP-VRF2 +---+LSI 22|
+------+ +---------+ +------+
|LSI 31+---+ IP-VRF3 +---+LSI 32|
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+------+ +---------+ +------+
|LSI 41+---+ IP-VRF4 +---+LSI 42|
+------+ +---------+ +------+
LSI-based Service Interface
N:1 1:N
+------+ +---------+ +------+
|LSI 11---------+ +--------+LSI 12|
+------+ + + +------+
|LSI 21+--------+ +--------+LSI 22|
+------+ + IP-VRF1 + +------+
|LSI 31+--------+ +--------+LSI 32|
+------+ + + +------+
|LSI 41+--------+ +--------+LSI 42|
+------+ +---------+ +------+
LSI-bundle Service Interface
N:1 1:N
+----------------------+
+------+ |+--------------------+| +------+
|LSI 11+--++ Logical Plane 1 ++--+LSI 12|
+------+ |+--------------------+| +------+
|LSI 21+--++ Logical Plane 2 ++--+LSI 22|
+------+ |+--------------------+| +------+
|LSI 31+--++ Logical Plane 3 ++--+LSI 32|
+------+ |+--------------------+| +------+
|LSI 41+--++ Logical Plane 4 ++--+LSI 42|
+------+ |+--------------------+| +------+
| |
| IP-VRF 1 |
+----------------------+
LSI-Aware Bundle Service Interface
Figure 2: Layer-3 accessible EVPN Service Interfaces Overview
For LSI-based service interface, there is a one to one mapping
between LSI and IP-VRF. Each IP-VRF has a single logical plane so
that traffic from different customers can be isolated.
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For LSI-bundle service interface, there is a N to one mapping between
LSI and IP-VRF. Each IP-VRF has a single logical plane, but the IP
address MUST be unique that can be used for customer traffic
isolation.
For LSI-aware bundle service interface, there is a N to one mapping
between LSI and IP-VRF. Each IP-VRF has multiple logical planes
while the IP address can overlap. One logical plane corresponds to
one LSI, which can be used to customer traffic isolation.
5. Solutions of LSI-aware bundle service interface
Let's assume a scenario as shown in Figure 3, where Backbone is EVPN
domain, and the MANs are Layer-3 network. VNIs in MANs are
independently allocated, which may lead to the overlap of VNI in
different customer sites.
+---+ +---+
|C-A+--------+ +-------+C-A|
+---+ | +-----------+ +-----------------+ +-----------+ | +---+
+-+--+ | | +-+-+ +-+-+ | | +--+-+
| CE +---+ MAN +-+PE | Backbone |PE +---+ MAN +---+ CE |
+-+--+ | | +-+-+ +-+-+ | | +--+-+
+---+ | +-----------+ +-----------------+ +-----------+ | +---+
|C-B+--------+ +-------+C-B|
+---+ +---+
Figure 3: LSI-aware bundle service interface scenario
If each VNI has its own IP-VRF, each PE and CE maintain an IP-VRF for
each deployment. In this situation, customer traffic can be isolated
by different VNIs, and there is no need for extending control plane/
forwarding plane protocols.
For deployment, we expect a simpler way, such as assign an IP-VRF to
each customer, not to each department. That is to say, all VNIs
share one IP-VRF on PEs. In this situation, each CE still maintain
an IP-VRF for each deployment, but each PE maintains only one VRF for
all deployments. In this situation, customer traffic cannot be
isolated by VNIs. We propose a solution for this scenario:
* Using LSI information to identify different customer routes /
traffic. As described above, LSI can be generated by VNI/SPI, and
there is a one to one mapping between LSI and VNI/SPI. PEs should
maintain the mapping table of LSI and VNI/SPI, so that they can
distinguish different customer routes / traffic. LSI information
can be transmitted by using Ethernet Tag ID or a newly defined ESI
type.
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* TBD (more solutions are welcome).
For example, the scenario shown in Figure 3 supports end-to-end L2/L3
data transmission. There is a N:1 mapping between LSI and EVI, 1:1
mapping between LSI and VLAN ID, and 1:1 mapping between LSI and VNI,
LSIs are used for traffic isolation. If customers need end-to-end L2
data transmission, the use of LSI is similar to VLAN ID. If
customers need end-to-end L3 data transmission, LSI can carry the
identification information of customers through the layer-3 network.
6. Protocol Extensions
6.1. Forwarding Plane
6.1.1. Extensions to VxLAN
When the forwarding plane uses VxLAN tunnel technologies, we should
extend the VxLAN GPE header to carry the LSI information, the
extentions to the VxLAN GPE header is shown in Figure 4:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R|S|Ver|I|P|B|O| LSI |Next Protocol |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VXLAN Network Identifier (VNI) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: The extentions to VxLAN GPE header
We define a S bit. If S is set to 1, it means the field after O bit
contains LSI information.
6.2. Control Plane
We propose two methods to advertise LSI information in control plane:
* Reusing the Ethernet Tag ID field. This method requires the
update of [I-D.ietf-bess-evpn-prefix-advertisement] (Etherenet Tag
ID is set to 0 for route type 5), and may arise some confuse with
the original definition of Ethernet Tag ID.
* Using the newly defined ESI type as shown in Figure 5. This
method can preserve the original purpose of ESI definition (multi-
homing).
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+---+---+---+---+---+---+---+---+---+---+
| T | Reserved | CE Identifier | LSI |
+---+---+---+---+---+---+---+---+---+---+
Figure 5: The format of new ESI type
Where:
* T (1 octet): specify the ESI Type. The recommended value is 0x06.
* CE Identifier (3 octets): the route ID/IPv4 address of CE.
* LSI (2 octets): the LSI information.
Since the length of LSI is 16 bits, while the length of Ethernet Tag
ID and ESI are 80 bits and 32 bits, respectively. We can only use
the lower 16 bits of Ethernet Tag ID / ESI field to carry LSI
information, the other bits MUST set to 0.
7. Modification of MAC/IP address storage mode on PE
LSI-aware bundle service interface also changes the storage mode of
MAC / IP address on PE, as shown in Figure 6.
+--------------------------+ +--------------------------------+
|MAC-VRF | |IP-VRF |
| | | |
| BD-A (LSI <-> VNI) | | Logical plane 1 (LSI <-> VNI) |
| MAC 1 | | IP Prefix 1 |
| ...... | | ...... |
| | | |
| BD-B (LSI <-> VNI) | | Logical plane 2 (LSI <-> VNI) |
| MAC 100 | | IP Prefix 100 |
| ...... | | ...... |
+--------------------------+ +--------------------------------+
LSI-Aware Bundle Service LSI-Aware Bundle Service
Interface(L2) Interface(L3)
Figure 6: Modification of MAC/IP address storage mode on PE
For end-to-end layer-2 data transmission, the storage mode of MAC
address in MAC-VRF is similar to VLAN-aware bundle service, the only
change is that different bridge domains are distinguished by LSI.
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For end-to-end layer-3 data transmission, sub-VRFs are needed in IP-
VRF to storage IP address. Different SDs are distinguished by LSIs.
8. Security Considerations
TBD
9. IANA Considerations
This draft extends the VxLAN GPE header, S bit of Flag and LSI field
are added:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R|S|Ver|I|P|B|O| LSI |Next Protocol |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VXLAN Network Identifier (VNI) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This draft also define a new ESI type:
+---+---+---+---+---+---+---+---+---+---+
| T | Reserved | CE Identifier | LSI |
+---+---+---+---+---+---+---+---+---+---+
10. Normative References
[I-D.ietf-bess-evpn-prefix-advertisement]
Rabadan, J., Henderickx, W., Drake, J., Lin, W., and A.
Sajassi, "IP Prefix Advertisement in Ethernet VPN (EVPN)",
Work in Progress, Internet-Draft, draft-ietf-bess-evpn-
prefix-advertisement-11, 18 May 2018,
<https://datatracker.ietf.org/doc/html/draft-ietf-bess-
evpn-prefix-advertisement-11>.
[I-D.ietf-bess-mvpn-evpn-aggregation-label]
Zhang, Z. J., Rosen, E. C., Lin, W., Li, Z., and I.
Wijnands, "MVPN/EVPN Tunnel Aggregation with Common
Labels", Work in Progress, Internet-Draft, draft-ietf-
bess-mvpn-evpn-aggregation-label-09, 12 December 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-bess-
mvpn-evpn-aggregation-label-09>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
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[RFC2890] Dommety, G., "Key and Sequence Number Extensions to GRE",
RFC 2890, DOI 10.17487/RFC2890, September 2000,
<https://www.rfc-editor.org/info/rfc2890>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <https://www.rfc-editor.org/info/rfc4301>.
[RFC7348] Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
eXtensible Local Area Network (VXLAN): A Framework for
Overlaying Virtualized Layer 2 Networks over Layer 3
Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,
<https://www.rfc-editor.org/info/rfc7348>.
[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>.
Authors' Addresses
Wei Wang
China Telecom
Beiqijia Town, Changping District
Beijing
Beijing, 102209
China
Email: weiwang94@foxmail.com
Aijun Wang
China Telecom
Beiqijia Town, Changping District
Beijing
Beijing, 102209
China
Email: wangaj3@chinatelecom.cn
Haibo Wang
Huawei Technologies
Huawei Building, No.156 Beiqing Rd.
Beijing
Beijing, 100095
China
Email: rainsword.wang@huawei.com
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