Internet DRAFT - draft-ietf-bess-pbb-evpn-isid-cmacflush
draft-ietf-bess-pbb-evpn-isid-cmacflush
BESS Workgroup J. Rabadan, Ed.
Internet-Draft S. Sathappan
Intended status: Standards Track K. Nagaraj
Expires: 16 June 2023 Nokia
M. Miyake
T. Matsuda
Softbank
13 December 2022
PBB-EVPN ISID-based CMAC-Flush
draft-ietf-bess-pbb-evpn-isid-cmacflush-06
Abstract
Provider Backbone Bridging (PBB) can be combined with Ethernet
Virtual Private Networks (EVPN) to deploy Ethernet Local Area Network
(ELAN) services in large Multi-Protocol Label Switching (MPLS)
networks (PBB-EVPN). Single-Active Multi-homing and per-I-SID (per
Service Instance Identifier) Load-Balancing can be provided to access
devices and aggregation networks. In order to speed up the network
convergence in case of failures on Single-Active Multi-Homed Ethernet
Segments, PBB-EVPN defines a flush mechanism for Customer MACs (CMAC-
flush) that works for different Ethernet Segment Backbone MAC (BMAC)
address allocation models. This document complements those CMAC-
flush procedures for cases in which no PBB-EVPN Ethernet Segments are
defined (the attachment circuit is associated to a zero Ethernet
Segment Identifier) and a Service Instance Identifier based (I-SID-
based) CMAC-flush granularity is required.
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). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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."
This Internet-Draft will expire on 16 June 2023.
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Copyright Notice
Copyright (c) 2022 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 (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology and Conventions . . . . . . . . . . . . . . . 4
2. Solution requirements . . . . . . . . . . . . . . . . . . . . 5
3. EVPN BGP Encoding for ISID-based CMAC-flush . . . . . . . . . 6
4. Solution description . . . . . . . . . . . . . . . . . . . . 8
4.1. ISID-based CMAC-Flush activation procedures . . . . . . . 8
4.2. CMAC-Flush generation . . . . . . . . . . . . . . . . . . 9
4.3. CMAC-flush process upon receiving a CMAC-flush
notification . . . . . . . . . . . . . . . . . . . . . . 9
5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 11
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
10.1. Normative References . . . . . . . . . . . . . . . . . . 11
10.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
[RFC7623] defines how Provider Backbone Bridging (PBB) can be
combined with Ethernet Virtual Private Networks (EVPN) to deploy ELAN
services in very large MPLS networks. [RFC7623] also describes how
Single-Active Multi-homing and per-I-SID Load-Balancing can be
provided to access devices and aggregation networks. When Access
Ethernet/MPLS Networks exists,
[I-D.ietf-bess-evpn-virtual-eth-segment] describes how virtual
Ethernet Segments can be associated to a group of Ethernet Virtual
Circuits (EVCs) or even Pseudowires (PWs). In order to speed up the
network convergence in case of failures on Single-Active Multi-Homed
Ethernet Segments, [RFC7623] defines a Customer MAC flush mechanism
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that works for different Ethernet Segment BMAC address allocation
models.
In some cases, the administrative entities that manage the access
devices or aggregation networks do not demand Multi-Homing Ethernet
Segments (ES) from the PBB-EVPN provider, but simply multiple single-
homed ES. If that is the case, the PBB-EVPN network is no longer
aware of the redundancy offered by the access administrative entity.
Figure 1 shows an example where the PBB-EVPN network provides four
different Attachment Circuits for I-SID1, with those Attachment
Circuits not being part of any Ethernet Segment or virtual Ethernet
Segment (therefore they are referred to as null virtual Ethernet
Segment).
<----G.8032--><--PBB-EVPN Network---><----MPLS---->
Access MPLS Access
Ring Network
I-SID1 ESI +-----+ +-----+
+----+ null| PE1 |---------| PE3 |
|CE1 |--------|BMAC1| |BMAC3| ESI null
+----+ active| | | |----+ PW
| +-----+ +-----+ \active
| | | \ +----+
| | | ==|CE3 |I-SID1
| | | / +----+
|stb ESI +-----+ +-----+ / PW
+----+ null| PE2 | | PE4 |----+ standby
|CE2 |--------|BMAC2| |BMAC4| ESI null
+----+ active| |---------| |
I-SID1 +-----+ +-----+
Figure 1: PBB-EVPN and non-ES based redundancy
In the example in Figure 1, CE1, CE2 and CE3 are attached to the same
service, identified by I-SID1, in the PBB-EVPN PEs. CE1 and CE2 are
connected to the PEs via G.8032 Ethernet Ring Protection Switching,
and their Attachment Circuits to PE1 and PE2 are represented by a
port and VLAN identifier. CE3 is dual-homed to PE3 and PE4 through
an active-standby PW, and its Attachment Circuit to the PEs is
represented by a PW. Each of the four PEs uses a dedicated Backbone
MAC address as source MAC address (BMAC1, BMAC2, BMAC3 and BMAC4,
respectively) when encapsulating customer frames in PBB packets and
forwarding those PBB packets to the remote PEs as per [RFC7623].
There are no multi-homed Ethernet Segments defined in the PBB-EVPN
network of the example, that is why the four Attachment Circuits in
Figure 1 show the text "ESI null", which means the Ethernet Segment
Identifier on those Attachment Circuits is zero. Since there are no
multi-homed ES defined, the PEs keep their Attachment Circuits active
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as long as the physical connectivity is established and the CEs are
responsible for managing the redundancy, avoiding loops and providing
per-I-SID load balancing to the PBB-EVPN network.
For instance, CE2 will block its link to CE1 and CE3 will block its
forwarding path to PE4. In this situation, a failure in one of the
redundant Attachment Circuits will trigger the CEs to start using
their redundant paths, however those failures will not trigger any
Customer MAC flush procedures in the PEs that implement [RFC7623],
since the PEs are not using the PBB-EVPN multi-homing procedures.
For example, if the active PW from CE3 (to PE3) fails, PE3 will not
issue any Customer MAC flush message and therefore the remote PEs
will continue pointing at PE3's Backbone MAC to reach CE3's Customer
MACs, until the Customer MACs age out in the I-SID1 forwarding
tables.
[RFC7623] provides a Customer MAC flush solution based on a shared
Backbone MAC update along with the MAC Mobility extended community
where the sequence number is incremented. However, the procedure is
only used along with multi-homed Ethernet Segments. Even if that
procedure could be used for null Ethernet Segments, as in the example
of Figure 1, the [RFC7623] Customer MAC flush procedure would result
in unnecessary flushing of unaffected I-SIDs on the remote PEs, and
subsequent flooding of unknown unicast traffic in the network.
This document describes an extension of the [RFC7623] Customer MAC
flush procedures, so that in the above failure example, PE3 can
trigger a Customer MAC flush notification that makes PE1, PE2 and PE4
flush all the Customer MACs associated to PE3's BMAC3 and (only)
I-SID1. This new Customer MAC flush procedure explained in this
document will be referred to as "PBB-EVPN I-SID-based CMAC-flush" and
can be used in PBB-EVPN networks with null or non-null (virtual)
Ethernet Segments.
1.1. Terminology and Conventions
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.
AC: Attachment Circuit.
B-Component: Backbone Component, as in [RFC7623].
BMAC: Backbone MAC address.
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BMAC/0 route: an EVPN MAC/IP Advertisement route that uses a BMAC in
the MAC address field and a zero Ethernet Tag ID.
BMAC/I-SID route: an EVPN MAC/IP Advertisement route that uses a BMAC
in the MAC address field and an I-SID in the Ethernet Tag field, and
it is used to notify remote PEs about the required CMAC-flush
procedure for the CMACs associated with the advertised BMAC and
I-SID.
CE: Customer Edge router.
CMAC: Customer MAC address.
ES, vES and ESI: Ethernet Segment, virtual Ethernet Segment and
Ethernet Segment Identifier.
EVI: EVPN Instance.
EVPN: Ethernet Virtual Private Networks, as in [RFC7432].
G.8032: Ethernet Ring Protection.
I-Component: Service Instance Component, as in [RFC7623].
I-SID: Service Instance Identifier.
MAC-VRF: A Virtual Routing and Forwarding table for MAC addresses.
PBB-EVPN: Provider-Backbone-Bridging and EVPN, as in [RFC7623].
PE: Provider Edge router.
RD: Route Distinguisher.
RT: Route Target.
Familiarity with the terminology in [RFC7623] is expected.
2. Solution requirements
The following requirements are followed by the CMAC-flush solution
described in this document:
a. The solution MUST prevent black-hole scenarios in case of
failures on null ES ACs (Attachment Circuits not associated to
ES, that is, their corresponding ESI is zero) when the access
device/network is responsible for the redundancy.
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b. This extension described in this document MUST with Single-Active
non-null ES and virtual ES, irrespective of the PE BMAC address
assignment (dedicated per-ES BMAC or shared BMAC, as in
[RFC7623]).
c. In case of failure on the egress PE, the solution MUST provide a
CMAC-flush notification at BMAC and I-SID granularity level.
d. The solution MUST provide a reliable CMAC-flush notification in
PBB-EVPN networks that use Route-Reflectors (RRs), without
causing "double flushing" or no flushing for certain I-SIDs due
to the notification messages being aggregated at the RR.
e. The solution MUST coexist in [RFC7623] networks where there are
PEs that do not support this specification.
f. The solution SHOULD be enabled/disabled by an administrative
option on a per-PE and per-I-SID basis.
3. EVPN BGP Encoding for ISID-based CMAC-flush
The solution does not use any new BGP attributes but reuses the MAC
Mobility extended community as an indication of CMAC-flush (as in
[RFC7623]) and encodes the I-SID in the Ethernet Tag field of the
EVPN MAC/IP advertisement route. As a reference, Figure 2 shows the
MAC Mobility extended community and the EVPN MAC/IP advertisement
route that are used specified in [RFC7432] and used in this document
as a CMAC-flush notification message.
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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=0x03 | Flags | Reserved=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+---------------------------------------+
| RD |
+---------------------------------------+
| ESI = 0 |
+---------------------------------------+
| Ethernet Tag ID = I-SID |
+---------------------------------------+
| MAC Address Length = 48 |
+---------------------------------------+
| BMAC Address |
+---------------------------------------+
| IP Address Length = 0 |
+---------------------------------------+
| MPLS Label1 |
+---------------------------------------+
Figure 2: CMAC-Flush notification encoding: BMAC/ISID route
Where:
* The route's RD and RT are the ones corresponding to its EVI.
Alternatively to the EVI's RT, the route MAY be tagged with an RT
auto-derived from the Ethernet Tag (I-SID) instead. [RFC7623]
describes how the EVPN MAC/IP Advertisement routes can be
advertised along with the EVI RT or an RT that is derived from the
I-SID.
* The Ethernet Tag encodes the I-SID for which the PE that receives
the route must flush the CMACs upon reception of the route.
* The MAC address field encodes the BMAC Address for which the PE
that receives the route must flush the CMACs upon reception of the
route.
* The MAC Mobility extended community is used as in [RFC7623], where
a delta in the sequence number between two updates for the same
BMAC/I-SID will be interpreted as a CMAC-flush notification for
the corresponding BMAC and I-SID.
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All the other fields are set and used as defined in [RFC7623]. This
document will refer to this route as the BMAC/I-SID route, as opposed
to the [RFC7623] BMAC/0 route (BMAC route sent with Ethernet Tag ID =
0).
Note that this BMAC/I-SID route will be accepted and reflected by any
[RFC7432] RR, since no new attributes or values are used. A PE
receiving the route will process the received BMAC/I-SID update only
in case of supporting the procedures described in this document.
4. Solution description
Figure 1 will be used in the description of the solution. CE1, CE2
and CE3 are connected to ACs associated to I-SID1, where no (Multi-
Homed) Ethernet Segments have been enabled, and the ACs and PWs are
in active or standby state as per Figure 1.
Enabling or disabling I-SID-based CMAC-flush SHOULD be an
administrative choice on the system that MAY be configured per I-SID
(I-Component). When enabled on a PE:
a. The PE will be able to generate BMAC/I-SID routes as CMAC-Flush
notifications for the remote PEs.
b. The PE will be able to process BMAC/I-SID routes received from
remote PEs.
When I-SID-based CMAC-flush is disabled, the PE will follow the
[RFC7623] procedures for CMAC-flush.
This CMAC-flush specification is described in three sets of
procedures:
* I-SID-based CMAC-flush activation
* CMAC-flush notification generation upon AC failures
* CMAC-flush process upon receiving a CMAC-flush notification
4.1. ISID-based CMAC-Flush activation procedures
The following behavior MUST be followed by the PBB-EVPN PEs following
this specification. Figure 1 is used as a reference.
* As in [RFC7623], each PE advertises a shared BMAC in a BMAC/0
route (with BMAC1, BMAC2, BMAC3 and BMAC4 in the MAC address
field, respectively). This is the BMAC that each PE will use as
BMAC SA (Source Address) when encapsulating the frames received on
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any local single-homed AC. Each PE will import the received
BMAC/0 routes from the remote PEs and will install the BMACs in
its B-component MAC-VRF. For instance, PE1 will advertise BMAC1/0
and will install BMAC2, BMAC3 and BMAC4 in its MAC-VRF.
* Assuming I-SID-based CMAC-flush is activated for I-SID 1, the PEs
will advertise the shared BMAC with I-SID 1 encoded in the
Ethernet Tag. That is, PE1 will advertise BMAC1/1 and will receive
BMAC2/1, BMAC3/1 and BMAC4/1. The receiving PEs MUST use these
BMAC/I-SID routes only for CMAC-flush procedures and they MUST NOT
be used them to add/withdraw any BMAC entry in the MAC-VRFs. As
per [RFC7623], only BMAC/0 routes can be used to add/withdraw
BMACs in the MAC-VRFs.
* The above procedure MAY also be used for dedicated BMACs (BMACs
allocated per Ethernet Segment).
4.2. CMAC-Flush generation
If, for instance, there is a failure on PE1's AC, PE1 will generate
an update including BMAC1/1 along with the MAC Mobility extended
community where the Sequence Number has been incremented. The
reception of the BMAC1/1 with a delta in the sequence number will
trigger the CMAC-flush procedures on the receiving PEs.
* An AC going operationally down MUST generate a BMAC/I-SID with a
higher Sequence Number. If the AC going down makes the entire
local I-SID go operationally down, the PE will withdraw the BMAC/
I-SID route for the I-SID.
* An AC going operationally up SHOULD NOT generate any BMAC/I-SID
update, unless it activates its corresponding I-SID, in which case
the PE will advertise the BMAC/I-SID route.
* An AC receiving a G.8032 flush notification or a flush message in
any other protocol from the access network MAY propagate it to the
remote PEs by generating a BMAC/I-SID route update with higher
Sequence Number.
4.3. CMAC-flush process upon receiving a CMAC-flush notification
A PE receiving a CMAC-flush notification will follow these
procedures:
* A received BMAC/I-SID route (with non-zero I-SID) MUST NOT add/
remove any BMAC to/from the MAC-VRF.
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* An update of a previously received BMAC/I-SID route with a delta
Sequence Number, MUST flush all the CMACs associated to that I-SID
and BMAC. CMACs associated to the same I-SID but different BMAC
MUST NOT be flushed.
* A received BMAC/I-SID withdraw (with non-zero I-SID) MUST flush
all the CMACs associated to that BMAC and I-SID.
Note that the CMAC-flush procedures described in [RFC7623] for BMAC/0
routes are still valid and a PE receiving [RFC7623] CMAC-flush
notification messages MUST observe the behavior specified in
[RFC7623].
5. Conclusions
The I-SID-based CMAC-flush solution described in this document has
the following benefits:
a. The solution solves black-hole scenarios in case of failures on
null ES ACs, since the CMAC-flush procedures are independent of
the Ethernet Segment definition.
b. This extension can also be used with Single-Active non-null ES
and virtual ES, irrespective of the PE BMAC address assignment
(dedicated per-ES BMAC or shared BMAC).
c. It provides a CMAC-flush notification at BMAC and I-SID
granularity level, therefore flushing a minimum number of CMACs
and reducing the amount of unknown unicast flooding in the
network.
d. It provides a reliable CMAC-flush notification in PBB-EVPN
networks that use RRs. RRs will propagate the CMAC-flush
notifications for all the affected I-SIDs and irrespective of the
order in which the notifications make it to the RR.
e. The solution can coexist in a network with systems supporting or
not supporting this specification.
6. Security Considerations
Security considerations described in [RFC7623] apply to this
document.
In addition, this document suggests additional procedures, that can
be activated on a per I-SID basis, and generate additional EVPN MAC/
IP Advertisement routes in the network. The format of these
additional EVPN MAC/IP Advertisement routes is backwards compatible
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with [RFC7623] procedures and should not create any issues on
receiving PEs not following this specification, however, the
additional routes may consume extra memory and processing resources
on the receiving PEs. Because of that, it is RECOMMENDED to activate
this feature only when necessary (when multi-homed networks or
devices are attached to the PBB-EVPN PEs), and not by default in any
PBB-EVPN PE.
7. IANA Considerations
This document requests no actions from IANA.
8. Acknowledgments
The authors want to thank Vinod Prabhu, Sriram Venkateswaran, Laxmi
Padakanti, Ranganathan Boovaraghavan for their review and
contributions.
9. Contributors
10. References
10.1. Normative References
[RFC7623] Sajassi, A., Ed., Salam, S., Bitar, N., Isaac, A., and W.
Henderickx, "Provider Backbone Bridging Combined with
Ethernet VPN (PBB-EVPN)", RFC 7623, DOI 10.17487/RFC7623,
September 2015, <https://www.rfc-editor.org/info/rfc7623>.
[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>.
[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>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
10.2. Informative References
[I-D.ietf-bess-evpn-virtual-eth-segment]
Sajassi, A., Brissette, P., Schell, R., Drake, J., and J.
Rabadan, "EVPN Virtual Ethernet Segment", Work in
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Progress, Internet-Draft, draft-ietf-bess-evpn-virtual-
eth-segment-07, 6 July 2021,
<https://www.ietf.org/archive/id/draft-ietf-bess-evpn-
virtual-eth-segment-07.txt>.
Authors' Addresses
Jorge Rabadan (editor)
Nokia
520 Almanor Avenue
Sunnyvale, CA 94085
United States of America
Email: jorge.rabadan@nokia.com
Senthil Sathappan
Nokia
520 Almanor Avenue
Sunnyvale, CA 94085
United States of America
Email: senthil.sathappan@nokia.com
Kiran Nagaraj
Nokia
520 Almanor Avenue
Sunnyvale, CA 94085
United States of America
Email: kiran.nagaraj@nokia.com
M. Miyake
Softbank
Email: masahiro.miyake@g.softbank.co.jp
T. Matsuda
Softbank
Email: taku.matsuda@g.softbank.co.jp
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