L2VPN Working Group Dave Allan, Jeff Tantsura
Internet Draft Ericsson
Intended status: Standards Track Don Fedyk
Expires: January 2014 Alcatel-Lucent
Ali Sajassi
Cisco
July 2013
802.1aq Support over EVPN
draft-allan-l2vpn-spbm-evpn-04
Abstract
This document describes how Ethernet Shortest Path Bridging MAC mode
(802.1aq) can be combined with EVPN in a way that interworks with
PBB-PEs as described in the PBB-EVPN solution in a way that permits
operational isolation of each Ethernet network subtending an EVPN
core while supporting full interworking between the different
variations of Ethernet operation.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance
with the provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on January 2014.
Copyright and License Notice
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Table of Contents
1. Introduction...................................................3
1.1. Authors......................................................3
1.2. Requirements Language........................................3
2. Conventions used in this document..............................3
2.1. Terminology..................................................3
3. Changes since previous version.................................4
4. Solution Overview..............................................4
5. Elements of Procedure..........................................5
5.1. PE Configuration.............................................5
5.2. DF Election..................................................6
5.3. Control plane interworking ISIS-SPB to EVPN..................6
5.4. Control plane interworking EVPN to ISIS-SPB..................7
5.5. Data plane Interworking 802.1aq SPBM island or PBB-PE to
EVPN..............................................................8
5.6. Data plane Interworking EVPN to 802.1aq SPBM island..........8
5.7. Data plane interworking EVPN to 802.1ah PBB-PE...............8
5.8. Multicast Support............................................8
6. Other Aspects..................................................8
6.1. Flow Ordering................................................8
6.2. Transit......................................................9
7. Acknowledgements...............................................9
8. Security Considerations........................................9
9. IANA Considerations............................................9
10. References....................................................9
10.1. Normative References........................................9
10.2. Informative References......................................9
11. Authors' Addresses...........................................10
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1. Introduction
This document describes how Ethernet Shortest Path Bridging MAC mode
(802.1aq) along with PBB-PEs and PBBNs (802.1ah) can be supported by
EVPN such that each island is operationally isolated while providing
full L2 connectivity between them. Each island can use its own
control plane instance and multi-pathing design, be it multiple ECT
sets, or multiple spanning trees.
The intention is to permit both past, current and emerging future
versions of Ethernet to be seamlessly integrated to permit large
scale, geographically diverse numbers of Ethernet end systems to be
fully supported with EVPN as the unifying agent.
1.1. Authors
David Allan, Jeff Tantsura, Don Fedyk, Ali Sajassi
1.2. Requirements Language
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 [1].
2. Conventions used in this document
2.1. Terminology
BCB: Backbone Core Bridge
BEB: Backbone Edge Bridge
BU: Broadcast/Unknown
B-MAC: Backbone MAC Address
B-VID: Backbone VLAN ID
CE: Customer Edge
C-MAC: Customer/Client MAC Address
DF: Designated Forwarder
ESI: Ethernet Segment Identifier
EVPN: Ethernet VPN
ISIS-SPB: IS-IS as extended for SPB
I-SID: I-Component Service ID
MP2MP: Multipoint to Multipoint
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MVPN: Multicast VPN
NLRI: Network Layer Reachability Information
PBBN: Provider Backbone Bridged Network
PBB-PE: Co located BEB and PE
PE: provider edge
P2MP: Point to Multipoint
P2P: Point to Point
RD: Route Distinguisher
SPB: Shortest path bridging
SPBM: Shortest path bridging MAC mode
3. Changes since previous version
1) Removal of reference to 802.1Qbp. This will be addressed in
separate document.
2) Determining ESI value exclusively requires configuration. This was
an open item in previous drafts.
4. Solution Overview
The EVPN solution for 802.1aq SPBM incorporates control plane
interworking in the PE to map ISIS-SPB [2] information elements into the
EVPN NLRI information and vice versa. This requires each PE to act both
as an EVPN BGP speaker and as an ISIS-SPB edge node. Associated with
this are procedures for configuring the forwarding operations of the PE
such that an arbitrary number of EVPN subtending SPBM islands may be
interconnected without any topological or multipathing dependencies.
This model also permits PBB-PEs as defined in draft-l2vpn-pbb-evpn-02[8]
to seamlessly communicate with the SPB islands.
+--------------+
| |
| |
+-----+ +----+ | | +----+ +---+
| |-----|SPBM| | | |PBB |---|CE2|
|SPBM | |PE1 | | IP/MPLS | |PE1 | +---+
+---+ |NTWK1| +----+ | Network | +----+
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|CE1|-| | | |
+---+ | | +----+ | |
| |-----|SPBM| | | +----+ +-----+
+-----+ |PE2 | | | |SPBM| |SPBM | +---+
+----+ | | |PE3 |---|NTWK2|-|CE3|
+--------------+ +----+ +-----+ +---+
Figure 1: PBB and SPBM EVPN Network
Each EVPN is identified by a route target. The route target identifies
the set of SPBM islands and BEB-PEs that are allowed to communicate.
Each SPBM island is administered to have an associated Ethernet Segment
ID (ESI) associated with it. This manifests itself as a set of Ethernet
segments, where each Ethernet segment ID is unique within the route
target.
BGP acts as a common repository of the I-SID attachment points for the
set of subtending PEs/SPBM islands. This is in the form of B-MAC
address/I-SID/Tx-Rx-attribute tuples. BGP leaks I-SID information into
each SPBM island on the basis of locally registered interest. If an SPBM
island has no BEBs registering interest in an I-SID, information about
that I-SID from other SPBM islands, PBB-PEs or PBBNs will not be leaked
into the local ISIS-SPB routing system.
For each B-VID in an SPBM island, a single SPBM-PE is elected the
designated forwarder for the B-VID. An SPBM-PE may be a DF for more than
one B-VID. This is described further in section 4.2. The SPBM-PE
originates IS-IS advertisements as if it were an I-BEB or IB-BEB that
proxy for the other SPBM islands and PBB PEs in the EVPN defined by the
route target, but the PE typically will not actually host any I-
components.
An SPBM-PE that is a DF for a B-VID strips the B-VID tag information
from frames relayed towards the EVPN. The DF also inserts the
appropriate B-VID tag information into frames relayed towards the SPBM
island on the basis of the local I-SID/B-VID bindings advertised in
ISIS-SPB.
5. Elements of Procedure
5.1. PE Configuration
At SPBM island commissioning a PE is configured with:
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1) The route target for the service instance. Where a route target
is defined as identifying the set of SPBM islands, PBBNs and PBB-
PEs to be interconnected by the EVPN.
2) The unique ESI for the SPBM island.
And the following is configured as part of commissioning an ISIS-SPB
node:
1) A Shortest Path Source ID (SPSourceID) used for algorithmic
construction of multicast DA addresses. Note this is required for
SPBM BEBs independent of the EVPN operation.
2) The set of VLANs (identified by B-VIDs) used in the SPBM island
and multi-pathing algorithm IDs to use. The B-VID may be
different in different domains and may be removed as carried over
the IP/MPLS network.
A type-1 Route Distinguisher (RD) for the node can be auto-derived.
This will be described in a future version of the document.
5.2. DF Election
PEs self appoint in the role of DF for a B-VID for a given SPBM
island. The procedure used is as per section 9.5 of draft-ietf-l2vpn-
evpn-03[4] "DF election".
5.3. Control plane interworking ISIS-SPB to EVPN
When a PE receives an SPBM service identifier and unicast address
sub-TLV as part of an ISIS-SPB MT capability TLV it checks if it is
the DF for the B-VID in the sub-TLV.
If it is the DF, and there is new or changed information then a MAC
advertisement route NLRI is created for each new I-SID in the sub-
TLV.
- the Route Distinguisher (RD) is set to that of the PE.
- the ESI is that of the SPBM island.
- the Ethernet tag ID contains the I-SID (including the Tx/Rx
attributes). The encoding of I-SID information is as per figure 2.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|T|R| Reserved | I-SID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: I-SID encoding in the Ethernet tag-ID field
- the MAC address from the sub-TLV
- an MPLS label
Similarly in the scenario where a PE became elected DF for a B-VID in
an operating network, the IS-IS database would be processed in order
to construct the NLRI information associated with the new role of the
PE.
If the BGP database has NLRI information for the I-SID, and this is
the first instance of registration of interest in the I-SID from the
SPB island, the NLRI information with that tag is processed to
construct an updated set of SPBM service identifier and unicast
address sub-TLVs to be advertised by the PE.
The ISIS-SPB information is also used to keep a local table indexed
by I-SID current to indicate the associated B-VID for processing of
frames received from EVPN. When an I-SID is associated with more than
one B-VID, only one entry is allowed in the table. Rules for this
will be in a future version of the document.
5.4. Control plane interworking EVPN to ISIS-SPB
When a PE receives a BGP NLRI that has new information, it checks if
the I-SID in the Ethernet Tag ID locally maps to the B-VID that are
an elected DF. Note that if no BEBs in the SPB island have advertised
any interest in the I-SID, it will not be associated with any B-VID
locally, and therefore not of interest. If the I-SID is of local
interest to the SPBM island and the PE is the DF for the B-VID that
that I-SID is locally mapped to, a SPBM service identifier and
unicast address sub-TLV is constructed/updated for advertisement into
ISIS-SPB.
The NLRI information advertised into ISIS-SPB is also used to locally
populate a forwarding table indexed by B-MAC+I-SID that points to the
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label stack associated with the SPBM frame. The bottom label in the
stack being that offered in the NLRI.
5.5. Data plane Interworking 802.1aq SPBM island or PBB-PE to EVPN
When an PE receives a frame from the SPBM island in a B-VID for which
it is a DF, it looks up the B-MAC/I-SID information to determine the
label stack to be added to the frame for forwarding in the EVPN. The
PE strips the B-VID information from the frame, adds the label
information to the frame and forwards the resulting MPLS packet.
5.6. Data plane Interworking EVPN to 802.1aq SPBM island
When a PE receives a packet from the EVPN it may infer the B-VID to
overwrite in the SPBM frame from the I-SID or by other means (such as
via the bottom label in the MPLS stack).
If the frame has a local multicast DA, it overwrites the SPsourceID
in the frame with the local SPsourceID.
5.7. Data plane interworking EVPN to 802.1ah PBB-PE
A PBB-PE actually has no subtending PBBN nor concept of B-VID so no
frame processing is required.
A PBB-PE is required to accept SPBM encoded multicast DAs as if they
were 802.1ah encoded multicast DAs. The only information of interest
being that it is a multicast frame, and the I-SID encoded in the
lower 24 bits.
5.8. Multicast Support
Refer to "mLDP extensions for integrating EVPN and multicast"[5].
6. Other Aspects
6.1. Flow Ordering
When per I-SID multicast is implemented via PE replication, a stable
network will preserve frame ordering between known unicast and BU
traffic (e.g. race conditions will not exist). This cannot be
guaranteed when multicast is used in the EVPN.
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6.2. Transit
Any PE that does not need to participate in the tandem calculations
may use the IS-IS overload bit to exclude SPBM tandem paths and
behave as pure interworking platform (I-BEB).
7. Acknowledgements
The authors would like to thank Peter Ashwood-Smith, Martin Julien
and Janos Farkas for their detailed review of this draft.
8. Security Considerations
For a future version of this document.
9. IANA Considerations
For a future version of this document.
10. References
10.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[2] Fedyk et.al. "IS-IS Extensions Supporting IEEE 802.1aq
Shortest Path Bridging", IETF RFC 6329, April 2012
[3] Rosen et.al., "BGP/MPLS IP Virtual Private Networks
(VPNs)", IETF RFC 4364, February 2006
[4] Aggarwal et.al. "BGP MPLS Based Ethernet VPN", IETF work
in progress, draft-ietf-l2vpn-evpn-02, October 2012
[5] Allan et.al. "mLDP extensions for integrating EVPN and
multicast", IETF work in progress draft-allan-l2vpn-mldp-
evpn-01, May 2013
10.2. Informative References
[6] 802.1aq(2012) IEEE Standard for Local and Metropolitan
Area Networks: Bridges and Virtual Bridged Local Area
Networks - Amendment 9: Shortest Path Bridging
[7] Sajassi et.al. "PBB E-VPN", IETF work in progress, draft-
ietf-l2vpn-pbb-evpn-04, February 2013
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[8] 802.1Q (2011) IEEE Standard for Local and metropolitan
area networks--Media Access Control (MAC) Bridges and
Virtual Bridged Local Area Networks
11. Authors' Addresses
Dave Allan (editor)
Ericsson
300 Holger Way
San Jose, CA 95134
USA
Email: david.i.allan@ericsson.com
Jeff Tantsura
Ericsson
300 Holger Way
San Jose, CA 95134
Email: jeff.tantsura@ericsson.com
Don Fedyk
Alcatel-Lucent
Groton, MA 01450
USA
EMail: Donald.Fedyk@alcatel-lucent.com
Ali Sajassi
Cisco
170 West Tasman Drive
San Jose, CA 95134, US
Email: sajassi@cisco.com
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