Internet DRAFT - draft-brissette-bess-vpws-seamless
draft-brissette-bess-vpws-seamless
BESS Working Group P. Brissette, Ed.
Internet-Draft A. Sajassi
Intended status: Standards Track L. Burdet
Expires: May 3, 2020 Cisco Systems
J. Uttaro
ATT
October 31, 2019
EVPN-VPWS Seamless Integration with Legacy VPWS
draft-brissette-bess-vpws-seamless-00
Abstract
This document specifies mechanisms for backward compatibility of
Ethernet VPN Virtual Private Wire Service (EVPN-VPWS) solutions with
legacy Virtual Private Wire Service (VPWS). It provides mechanisms
for seamless integration in the same MPLS/IP network on a per-
pseudowire or per-flexible-crossconnect basis. Implementation of
this document enables service providers to introduce EVPN-VPWS PEs in
their brown-field deployments of leagcy VPWS networks. This document
specifies control-plane and forwarding behavior needed for auto-
discovery of a pseudowire in order to enable seamless integration
between EVPN-VPWS and VPWS PEs.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on May 3, 2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terms and Abbreviations . . . . . . . . . . . . . . . . . . . 4
3. Solution Requirements . . . . . . . . . . . . . . . . . . . . 5
4. Seamless Integration . . . . . . . . . . . . . . . . . . . . 6
5. Capability Discovery . . . . . . . . . . . . . . . . . . . . 6
6. Forwarding and Control Plane Operations . . . . . . . . . . . 6
6.1. Multi-homed Operations . . . . . . . . . . . . . . . . . 8
6.1.1. Operations with Port-Active MH PEs . . . . . . . . . 8
6.1.2. Operation with Single-Active MH PEs . . . . . . . . . 9
6.1.3. Operation with All-Active MH PEs . . . . . . . . . . 9
6.1.3.1. Falling back to port-active . . . . . . . . . . . 9
6.1.3.2. All-active procedures . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
8. Security Considerations . . . . . . . . . . . . . . . . . . . 11
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1. Normative References . . . . . . . . . . . . . . . . . . 11
9.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
Virtual Private Wire Service (VPWS) is a widely-deployed Layer-2 VPN
(L2VPN) technology. Many service providers, who are looking at
adopting Ethernet VPN Virtual Private Wire Service (EVPN-VPWS), want
to preserve their investment in the VPWS networks. Hence, they
require mechanisms by which EVPN-VPWS can be introduced into their
brown-field legacy VPWS networks without requiring any upgrades
(software or hardware) to these networks. This document specifies
procedures for the seamless integration of the two technologies
(EVPN-VPWS and legacy VPWS) in the same MPLS/IP network. This
document specifies control-plane and forwarding behaviour needed for
auto-discovery of a pseudowire in order to enable seamless
integration between EVPN-VPWS Provider Edge(PE) devices and PEs
running legacy VPWS services.
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MPLS/IP Core
+---------------+
+---+ | | +---+
|PE1|----|----- PW1 -----|---|PE2| Legacy VPWS
| |----|---+ | +---+
+---+ | | |
EVPN-VPWS & | +--PW2---+ | +---+
Legacy VPWS | +--|---|PE3| EVPN-VPWS
| | +---+
+---------------+
Seamless Integration of EVPN-VPWS.
Figure 1
Figure 1 shows a simple network where PE1 runs in hybrid mode (EVPN-
VPWS and legacy VPWS). It provides a pseudowire (PW1) with PE2
running legacy VPWS. It also provides a pseudowire (PW2) with PE2
running EVPN-VPWS. PE2 may be upgraded to EVPN-VPWS seamlessly.
Legacy PEs may be setting up PWs per [RFC8077] or may be setting up a
VPWS service by first auto-discovering VPN members using [RFC6074]
and then setting up the PWs using [RFC8077] or [RFC6624].\
The seamless integration solution described in this document has the
following attributes:
- It is backward compatible with [RFC8214] and EVPN Flexible
crossconnect Service [evpn_fxc] document.
- New PEs can leverage the multi-homing mechanisms and provisioning
simplifications of EVPN Ethernet-Segment:
a. Auto-sensing of MHN / MHD
b. Auto-discovery of redundancy group
c. Auto-election of Designated Forwarder and VLAN carving
d. Support of various load-balancing mode such as port-active,
single-active and all-active
1.1. 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].
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2. Terms and Abbreviations
o CE: A Customer Edge device, e.g., a host, router, or switch.
o DF: EVPN Ethernet Segment Designated Forwarder.
o NDF: EVPN Ethernet Segment Non-Designated Forwarder.
o Ethernet Segment (ES): Refers to the set of Ethernet links that
connects a customer site (device or network) to one or more PEs.
o Ethernet Tag: An Ethernet Tag identifies a particular pseudowire,
e.g. a PW-ID.
o FEC: Forwarding Equivalence Class
o LDP-LM: LDP Label Mapping Message
o LDP-LW: LDP Label Withdraw Message
o LSP: Label Switched Path
o MHD: Multi-Homed Device
o MHN: Multi-Homed Network
o P2P: Point to Point - a P2P LSP typically refers to a LSP for
Layer2 pseudowire
o PE: Provider Edge device
o VPWS: Virtual Private Wire Service. It refers to legacy VPWS
circuit where pseudowires are signalled using LDP or BGP-AD
protocol. The latter is referred as VPWS A-D.
o EVPN-VPWS: Ethernet-VPN Virtual Private Wire Service. It refers
to EVPN-VPWS circuit where pseudowires are signalled via BGP-EVPN.
It also includes EVPN-FXC service.
o EVPN-FXC: Ethernet-VPN Flexible Cross-connect Service [evpn_fxc].
o Port-Active Redundancy Mode: When only a single PE, among all the
PEs attached to an Ethernet segment, is allowed to forward traffic
to/from that Ethernet segment for a given interface, then the
Ethernet Segment is defined to be operating in Port-Active
redundancy mode.
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o Single-Active Redundancy Mode: When only a single PE, among all
the PEs attached to an Ethernet segment, is allowed to forward
traffic to/from that Ethernet segment for a given VLAN, then the
Ethernet Segment is defined to be operating in Single-Active
redundancy mode.
o All-Active Redundancy Mode: When all PEs attached to an Ethernet
Segment are allowed to forward traffic to/from that Ethernet
segment for a given VLAN, then the Ethernet segment is defined to
be operating in All-Active redundancy mode.
o VPWS A-D: refers to Virtual Private Wire Services with BGP-based
Auto Discovery as in [RFC6074].
o PW: Pseudowire
3. Solution Requirements
o Following are the key requirements for backward compatibility
between EVPN-VPWS and VPWS:
o The solution MUST allow for staged migration towards EVPN-VPWS on
a site-by-site basis - e.g., new EVPN-VPWS sites to be provisioned
on EVPN-VPWS Provider Edge devices (PEs). Migration SHOULD be
possible on a per-pseudowire basis.
o The solution MUST NOT require any changes to existing VPWS or PEs,
not even a software upgrade.
o The solution MUST allow for the co-existence of PE devices running
EVPN-VPWS and VPWS for the same pseudowire and single-homed
segments.
o The solution MUST support port-active redundancy of multi-homed
networks and multi-homed devices for EVPN-VPWS PEs.
o The solution MUST support single-active redundancy of multi-homed
networks and multi-homed devices for EVPN-VPWS PEs.
o The solution SHOULD support all-active redundancy of multi-homed
Ethernet Segments for EVPN-VPWS PEs.
These requirements collectively allow for the seamless insertion of
the EVPN-VPWS technology into brown-field VPWS deployments.
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4. Seamless Integration
In order to support seamless integration with Legacy PEs, this
document may require Legacy PEs to setup PWs per [RFC8077] or may
require Legacy PEs to setup VPWS service by auto-discovering VPN
members using [RFC6074] and then setting up the PWs using [RFC8077]
or [RFC6624]. Furthermore, EVPN-VPWS PEs must support BGP EVPN
routes per [RFC8214] and one of method of legacy VPWS technologies.
All the logic for seamless integration SHALL reside on the EVPN-VPWS
PEs.
5. Capability Discovery
The EVPN-VPWS PEs MUST advertise both the BGP VPWS Auto-Discovery
(VPWS A-D) route or LDP-LM message as well as the BGP EVPN Ethernet-
AD per EVI route for a given pseudowire. The VPWS PEs only advertise
the BGP VPWS A-D route, per the procedures specified in [RFC4664] and
[RFC6074]. The operator may decide to use the same BGP Route Target
(RT) to identify a pseudowire on both EVPN-VPWS and VPWS networks.
In this case, when a VPWS PE receives the EVPN Ethernet-AD per EVI
route, it MUST ignore it on the basis that it belongs to an unknown
SAFI. However, the operator may choose to use two RTs - one to
identify the pseudowire on VPWS network and another for EVPN-VPWS
network and employ RT-constrained [RFC4684] in order to prevent BGP
EVPN routes from reaching the VPWS PEs.
When an EVPN-VPWS PE receives both a VPWS A-D route or a LDP-LM
message as well as an EVPN-VPWS Ethernet-AD per EVI route from a
given remote PE for the same pseudowire, it MUST give preference to
the EVPN-VPWS route for the purpose of discovery. This ensures that,
at the end of the route exchanges, all EVPN-VPWS capable PEs discover
other EVPN-VPWS capable PEs. Furthermore, all the VPWS-only PEs will
discover the EVPN-VPWS PEs as if they were standard VPWS PEs. In
other words, when the discovery phase is complete, the EVPN-VPWS PEs
will have discovered the remote PE per pseudowire along with their
associated capability (EVPN-VPWS or VPWS-only), whereas the VPWS PE
will have discovered the remote PE per pseudowire as if it was VPWS-
only PEs.
6. Forwarding and Control Plane Operations
The procedures for forwarding state setup on the VPWS PE are per
[RFC8077], [RFC4761] and [RFC4762].
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EVPN-VPWS & MPLS/IP
Legacy VPWS Core Legacy VPWS
+---------------+
+---+ | | +---+
|PE1|----|----- PW1 -----|---|PE2| Legacy VPWS
+---+ | | +---+
+---------------+
VPWS A-D route ] TX TX [ VPWS A-D route
or ] ---> <--- [ or
LDP Label Mapping ] [ LDP Label Mapping
AND
TX
EVPN per EVI/EAD ] --->
EVPN-VPWS Single-Homed
Figure 2
The procedures for forwarding state setup on the EVPN-VPWS PE are as
follows:
o The EVPN-VPWS PE MUST establish a PW to each remote PE from which
it has received only a VPWS A-D route or a LDP-LM message for the
corresponding pseudowire, and MUST set up the label stack
corresponding to the PW FEC.
o If an EVPN-VPWS PE receives a VPWS A-D route or a LDP-LM message
from a given PE, it sets up a Legacy VPWS PW to that PE. If it
then receives an EVPN Ethernet-AD per EVI route for that PW from
the same PE, then the EVPN-VPWS PE may bring the Legacy PW
operationally down and MUST forward traffic using the label
information from the EVPN Ethernet-AD per EVI route.
o If an EVPN-VPWS PE receives an EVPN Ethernet-AD per EVI route
followed by a VPWS A-D route or a LDP-LM message from the same PE,
then the EVPN-VPWS PE will setup the EVPN-VPWS PW. It may keep
the Legacy VPWS PW operationally down and MUST forward traffic
using the label information from that EVPN Ethernet-AD per EVI
route.
o For VPWS PE not using VPWS A-D or LDP signalling, the EVPN-VPWS
PEs need to be provisioned manually with PWs to those remote VPWS
PEs for each pseudowire. In that case, if an EVPN-VPWS PE
receives an EVPN Ethernet-AD per EVI route from a PE to which a PW
exists, it may keep VPWS PW operationally down and MUST forward
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traffic using the label information from that EVPN Ethernet-AD per
EVI route.
6.1. Multi-homed Operations
Figure 3 below demonstrates multi-homing scenarios. CE1 is connected
to PE1 and PE2 where PE1 is the designated forwarder while PE2 is the
non designated forwarder.
EVPN-VPWS & MPLS/IP
Legacy VPWS Core Legacy VPWS
+---------+
DF +---+ | | +---+ +---+
+--|PE1|----|---------|---|PE3|---|CE2|
+---+/ +---+ | PW1 /| +---+ +---+
|CE1| | / |
+---+\ +---+ | / |
+--|PE2|----|-----+ |
NDF +---+ | |
+---------+
EVPN-VPWS Port-Active Redundancy
Figure 3
6.1.1. Operations with Port-Active MH PEs
In Figure 3, PE1 and PE2 are configured in port-active load-balancing
mode. Both PEs are advertising EVPN Ethernet-AD per ES route with
the single-active bit set as described in EVPN port-active document
[evpn_pa]. In this example PE1 is DF elected for the shared Ethernet
Segment identifier.
o Only PE1, as DF, advertises the VPWS A-D route or LDP-LM message
towards remote PE3.
o PE1 advertises the EVPN Ethernet AD per EVI route for PW1 towards
remote PE3. The P-bit in L2 Attributes Extended Community is set
for PE1 as per [RFC8214]. The purpose is to have all required
EVPN-VPWS routes on remote PE so during an upgrade from Legacy
VPWS to EVPN-VPWS, those remote nodes are immediately upgraded.
o PE2, as NDF, only advertises its EVPN Ethernet AD per EVI route
corresponding to that same PW1. The B-bit in L2 Attributes
Extended Community is set for PE1 as per [RFC8214]
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Upon link failure between CE1 and PE1, PE1 and PE2 follows EVPN
Ethernet Segment DF Election and/or procedures described in [RFC8214]
for the EVPN-VPWS. Furthermore, PE1 withdraws its VPWS A-D route or
sends LDP-LW message to remote PE3 to teardown the Legacy PW.
Finally, PE2 advertises corresponding VPWS A-D route or LDP-LM
message for that PW1 and re-establish Legacy PW with new PE2
destination.
If PE3 is running 2-way pseudowire redundancy and PW-status is
enabled, PE2 may leverage the existance of standby/backup PW with
PE3. In this particular scenario where PW-status is enabled, PE2 may
advertise VPWS A-D route or LDP-LM message along with PW-status
message.
Once PE3 is upgraded and supports EVPN-VPWS, EVPN-VPWS routes are
exchanged by this PE. Higher precedence of EVPN-VPWS over VPWS allow
all PEs to avoid the usage of legacy circuit. At that point in time,
unpreferred legacy VPWS protocols and configuration may be removed
from all PEs.
6.1.2. Operation with Single-Active MH PEs
Single-active operation is similar to Port-active load-balancing mode
described above but at the VLAN level instead being of at the port/
interface level. Moreover, the procedures described in [RFC8214] are
applied.
The main difference resides on the support of Legacy PW VC-type 4 vs
PW VC-Type 5 mode on the EVPN-VPWS PE as per [RFC4448]. While
services running in port-active load-balancing mode require raw mode,
services running single-active load-balancing mode use tagged mode.
6.1.3. Operation with All-Active MH PEs
In EVPN-VPWS all-active load-balancing mode, all PEs participating in
a redundancy group forward traffic bidirectionally, reducing the
importance of DF and NDF PE. However PEs running Legacy VPWS do NOT
support all-active peering PEs as remote endpoint.
6.1.3.1. Falling back to port-active
PE discovering remote PE running VPWS PW MAY fallback into port-
active load-balancing mode. In that case, following rules are
applied
o Peering PEs advertises EVPN Ethernet-AD per ES route with the
single-active bit set.
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o DF PE advertises VPWS AD routes or LDP-LM message and EVPN
Ethernet AD per EVI route per PW.
o NDF PE advertises only EVPN Ethernet AD per EVI route per PW.
o If PE3 is running 2-ways pseudowire redundancy, PE2 may leverage
the existence of standby/backup PW with PE3. PE2 may advertises
VPWS AD route or LDP-LM message with proper PW-status message.
6.1.3.2. All-active procedures
To support the case where CE device is forwarding traffic to peering
PE, extensions to EVPN-VPWS MH procedure are required. In the
example of Figure 3, traffic from CE1 going to PE1 gets forwarded to
PE3 using the VPN label learned from VPWS AD route or LDP-LM message
received from PE3. Traffic from CE1 going to PE2 should gets
forwarded to PE3 using that same VPN label. Traffic coming from CE3
to PE3 gets forwarded only over the primary PW towards PE1. It is an
asymmetric forwarding.
Following rules are applied to achieve expected behaviour:
o Peering PEs advertises EVPN Ethernet-AD per ES route with the
single-active bit unset. Again, to this to get ready on remote PE
in case of that legacy PE gets upgraded to EVPN-VPWS.
o DF PE advertises VPWS AD routes or LDP-LM message and EVPN
Ethernet AD per EVI route per PW.
o NDF PE advertises only EVPN Ethernet AD per EVI route per PW.
o If PE3 is running 2-ways pseudowire redundancy, PE2 may leverage
the existence of standby/backup PW with PE3. PE2 may advertises
VPWS AD route or LDP-LM message with proper PW-status message.
To support all-active load-balancing mode on EVPN-VPWS peering PEs,
the tunnel encapsulation attribute [tun_encap] is used to synchronize
alias PW label between peering PEs. The tunnel encapsulation
attribute, specifying the alias PW label and tunnel endpoint
(nexthop) of the remote PE (PE3), is transmitted along with EVPN
Ethernet-AD per EVI route. The NDF PEs uses the same VPN label per
Legacy PW as DF PE when transmitting traffic coming from CE (CE1)
towards remote PE(PE3).
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7. IANA Considerations
This document has no actions for IANA.
8. Security Considerations
The same Security Considerations described in RFC 8214 [RFC8214] are
valid for this document.
9. References
9.1. Normative References
[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>.
[RFC6074] Rosen, E., Davie, B., Radoaca, V., and W. Luo,
"Provisioning, Auto-Discovery, and Signaling in Layer 2
Virtual Private Networks (L2VPNs)", RFC 6074,
DOI 10.17487/RFC6074, January 2011,
<https://www.rfc-editor.org/info/rfc6074>.
[RFC6624] Kompella, K., Kothari, B., and R. Cherukuri, "Layer 2
Virtual Private Networks Using BGP for Auto-Discovery and
Signaling", RFC 6624, DOI 10.17487/RFC6624, May 2012,
<https://www.rfc-editor.org/info/rfc6624>.
[RFC8077] Martini, L., Ed. and G. Heron, Ed., "Pseudowire Setup and
Maintenance Using the Label Distribution Protocol (LDP)",
STD 84, RFC 8077, DOI 10.17487/RFC8077, February 2017,
<https://www.rfc-editor.org/info/rfc8077>.
[RFC8214] Boutros, S., Sajassi, A., Salam, S., Drake, J., and J.
Rabadan, "Virtual Private Wire Service Support in Ethernet
VPN", RFC 8214, DOI 10.17487/RFC8214, August 2017,
<https://www.rfc-editor.org/info/rfc8214>.
9.2. Informative References
[evpn_fxc]
Sajassi, A. and P. Brissette, "draft-ietf-bess-evpn-vpws-
fxc", 2019.
[evpn_pa] Brissette, P. and A. Sajassi, "draft-brissette-bess-evpn-
mh-pa", 2019.
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[RFC4448] Martini, L., Ed., Rosen, E., El-Aawar, N., and G. Heron,
"Encapsulation Methods for Transport of Ethernet over MPLS
Networks", RFC 4448, DOI 10.17487/RFC4448, April 2006,
<https://www.rfc-editor.org/info/rfc4448>.
[RFC4664] Andersson, L., Ed. and E. Rosen, Ed., "Framework for Layer
2 Virtual Private Networks (L2VPNs)", RFC 4664,
DOI 10.17487/RFC4664, September 2006,
<https://www.rfc-editor.org/info/rfc4664>.
[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>.
[RFC4761] Kompella, K., Ed. and Y. Rekhter, Ed., "Virtual Private
LAN Service (VPLS) Using BGP for Auto-Discovery and
Signaling", RFC 4761, DOI 10.17487/RFC4761, January 2007,
<https://www.rfc-editor.org/info/rfc4761>.
[RFC4762] Lasserre, M., Ed. and V. Kompella, Ed., "Virtual Private
LAN Service (VPLS) Using Label Distribution Protocol (LDP)
Signaling", RFC 4762, DOI 10.17487/RFC4762, January 2007,
<https://www.rfc-editor.org/info/rfc4762>.
[tun_encap]
Patel, K., Van de Velde, G., and S. Sangli, "draft-ietf-
idr-tunnel-encaps", 2019.
[vpls_AA] Sajassi, A., Salam, S., Brissette, P., and L. Jalil,
"draft-sajassi-bess-evpn-vpls-all-active", 2017.
Authors' Addresses
Patrice Brissette (editor)
Cisco Systems
Ottawa, ON
Canada
Email: pbrisset@cisco.com
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Ali Sajassi
Cisco Systems
USA
Email: sajassi@cisco.com
Luc Andre Burdet
Cisco Systems
Ottawa
Canada
Email: lburdet@cisco.com
James Uttaro
ATT
USA
Email: uttaro@att.com
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