L2VPNs K. Patel
Internet-Draft A. Sajassi
Intended status: Standards Track Cisco Systems
Expires: January 3, 2016 J. Drake
Juniper Networks, Inc.
W. Henderickx
Alcatel-Lucent
July 2, 2015
Virtual Hub-and-Spoke in BGP EVPNs
draft-keyupate-evpn-virtual-hub-00
Abstract
Ethernet Virtual Private Network (EVPN) solution is becoming
pervasive for Network Virtualization Overlay (NVO) services in data
center (DC) applications and as the next generation virtual private
LAN services in service provider (SP) applications.
The use of host IP default route and host unknown MAC route within a
DC is well understood in order to ensure that leaf nodes within a DC
only learn and store host MAC and IP addresses for that DC. All
other host MAC and IP addresses from remote DCs are learned and
stored in DC GW nodes thus alleviating leaf nodes from learning host
MAC and IP addresses from the remote DCs.
This draft further optimizes the MAC and IP address learning at the
leaf nodes such that a leaf node within a DC only needs to learn and
store MAC and IP addresses associated with the sites directly
connected to it. A leaf node does not need to learn and store MAC
and IP addresses from any other leaf nodes thus reducing the number
of learned MACs and IP addresses per EVI substantially.
The modifications provided by this draft updates and extends RFC7024
for BGP EVPN Address Family.
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 http://datatracker.ietf.org/drafts/current/.
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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 January 3, 2016.
Copyright Notice
Copyright (c) 2015 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Routing Information Exchange for EVPN routes . . . . . . . . 4
5. EVPN unknown MAC Route . . . . . . . . . . . . . . . . . . . 5
5.1. Originating EVPN Unknown MAC Route by a V-Hub . . . . . . 5
5.2. Processing VPN-MAC EVPN unknown Route by a V-SPOKE . . . 5
5.3. Aliasing . . . . . . . . . . . . . . . . . . . . . . . . 5
5.4. Split-Horizon And Mass Withdraw . . . . . . . . . . . . . 6
6. Forwarding Considerations . . . . . . . . . . . . . . . . . . 7
6.1. IP-only Forwarding . . . . . . . . . . . . . . . . . . . 7
6.2. MAC-only Forwarding - Bridging . . . . . . . . . . . . . 7
6.3. MAC and IP Forwarding - IRB . . . . . . . . . . . . . . . 7
7. Handling of the Broadcast and Multicast traffic . . . . . . . 8
8. ARP/ND Suppression . . . . . . . . . . . . . . . . . . . . . 8
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
10. Security Considerations . . . . . . . . . . . . . . . . . . . 9
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
12. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 9
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
13.1. Normative References . . . . . . . . . . . . . . . . . . 9
13.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
Ethernet Virtual Private Network (EVPN) solution is becoming
pervasive for Network Virtualization Overlay (NVO) services in data
center (DC) applications and as the next generation virtual private
LAN services in service provider (SP) applications.
With EVPN, providing any-to-any connectivity among sites of a given
EVPN Instance (EVI) would require each Provider Edge (PE) router
connected to one or more of these sites to hold all the host MAC and
IP addresses for that EVI. The use of host IP default route and host
unknown MAC route within a DC is well understood in order to
alleviate the learning of host MAC and IP addresses to only leaf
nodes (PEs) within that DC. All other host MAC and IP addresses from
remote DCs are learned and stored in DC GW nodes thus alleviating
leaf nodes from learning host MAC and IP addresses from the remote
DCs.
This draft further optimizes the MAC and IP address learning at the
leaf nodes such that a leaf node within a DC only needs to learn and
store MAC and IP addresses associated with the sites directly
connected to it. A leaf node does not need to learn and store MAC
and IP addresses from any other leaf nodes thus reducing the number
of learned MACs and IP addresses per EVI substantially.
[RFC7024] provides rules for Hub and Spoke VPNs for BGP L3VPNs. This
draft updates and extends [RFC7024] for BGP EVPN Address Family.
This draft provides rules for Originating and Processing of the EVPN
host unknown MAC route and host default IP route by EVPN Virtual Hub
(V-HUB). This draft also provides rules for the handling of the BUM
traffic in Hub and Spoke EVPNs and handling of ARP suppression.
The leaf nodes and DC GW nodes in a data center are referred to as
Virtual Spokes (V-spokes) and Virtual Hubs (V-hubs) respectively. A
set of V-spoke can be associated with one or more V-hubs. If a V-
spokes is associated with more than one V-hubs, then it can load
balanced traffic among these V-hubs. Different V-spokes can be
associated with different sets of V-hubs such that at one extreme
each V-spoke can have a different V-hub set although this may not be
desirable and a more typical scenario may be to associate a set of V-
spokes to a set of V-hubs - e.g., topology for a DC POD where a set
of V-spokes are associated with a set of spine nodes or DC GW nodes.
In order to avoid repeating many of the materials covered in
[RFC7024], this draft is written as a delta document with its
sections organized to follow those of that RFC with only delta
description pertinent to EVPN operation in each section. Therefore,
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it is assumed that the readers are very familiar with [RFC7024] and
EVPN.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to
be interpreted as described in [RFC2119] only when they appear in all
upper case. They may also appear in lower or mixed case as English
words, without any normative meaning.
3. Terminology
ARP: Address Resolution Protocol
BEB: Backbone Edge Bridge
B-MAC: Backbone MAC Address
CE: Customer Edge
C-MAC: Customer/Client MAC Address
ES: Ethernet Segment
ESI: Ethernet Segment Identifier
IRB: Integrated Routing and Bridging
LSP: Label Switched Path
MP2MP: Multipoint to Multipoint
MP2P: Multipoint to Point
ND: Neighbor Discovery
NA: Neighbor Advertisement
P2MP: Point to Multipoint
P2P: Point to Point
PE: Provider Edge
EVPN: Ethernet VPN
EVI: EVPN Instance
RT: Route Target
Single-Active Redundancy Mode: When only a single PE, among a group
of PEs attached to an Ethernet segment, is allowed to forward traffic
to/from that Ethernet Segment, then the Ethernet segment is defined
to be operating in Single-Active redundancy mode.
All-Active Redundancy Mode: When all PEs attached to an Ethernet
segment are allowed to forward traffic to/from that Ethernet Segment,
then the Ethernet segment is defined to be operating in All-Active
redundancy mode.
4. Routing Information Exchange for EVPN routes
[RFC7024] defines multiple Route Types NLRI along with procedures for
advertisements and processing of these routes. Some of these
procedures are impacted as the result of hub-and-spoke architecture.
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The routing information exchange among the hub, spoke, and vanilla
PEs are subject to the same rules as described in section 3 of
[RFC7024]. Furthermore, if there are any changes to the EVPN route
advisements and processing from advertisements and processing from
[RFC7024], they are described below.
5. EVPN unknown MAC Route
Section 3 of [RFC7024] talks about how a V-hub of a given VPN must
export a VPN-IP default route for that VPN and this route must be
exported to only the V-spokes of that VPN associated with that V-hub.
[I-D.EVPN-overlay] defines the notion of the unknown MAC route for an
EVI which is analogous to a VPN-IP default route for a VPN. This
unknown MAC route is exported by a V-hub to its associated V-spokes.
If multiple V-hubs are associated with a set of V-spokes, then each
V- hub advertises it with a distinct RD when originating this route.
If a V-spoke imports several of these unknown MAC routes and they all
have the same preference, then traffic from the V-spoke to other
sites of that EVI would be load balanced among the V-hubs.
5.1. Originating EVPN Unknown MAC Route by a V-Hub
Section 7.3 of the [RFC7024] defines procedures for originating a
VPN-IP default route for a VPN. The same procuedures apply when a
V-hub wants to originate EVPN unknown MAC route for a given EVI. The
V-hub MUST announce unknown MAC route using the MAC/IP advertisement
route along with the Default Gateway extended community as defined in
section 10.1 of the [RFC7432].
5.2. Processing VPN-MAC EVPN unknown Route by a V-SPOKE
Within a given EVPN, a V-spoke MUST import all the unknown MAC routes
unless the route-target mismatch happens. The processing of the
received VPN-MAC EVPN default route follows the rules explained in
the section 3 of the [RFC7024]. The unknown MAC route MUST be
installed according to the rules of MAC/IP Advertisement route
installation rules in section 9.2.2 of [RFC7024].
In absense of any more specific VPN-MAC EVPN routes, V-spokes
installing the unknown MAC route MUST use the route when performing
ARP proxy. This behavior would allow V-Spokes to forward the traffic
towards V-Hub.
5.3. Aliasing
[RFC7432] describes the concept and procedures for Aliasing where a
station is multi-homed to multiple PEs operating in an All-Active
redundancy mode, it is possible that only a single PE learns a set of
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MAC addresses associated with traffic transmitted by the station.
[RFC7432] describes the concepts and procedures for Aliasing, which
occurs when a CE is multi-homed to multiple PE nodes, operating in
all-active redundancy mode, but not all of the PEs learn the CE's set
of MAC addresses. This leads to a situation where remote PEs receive
MAC advertisement routes, for these addresses, from a single NVE even
though multiple NVEs are connected to the multi-homed station. As a
result, the remote NVEs are not able to effectively load-balance
traffic among the NVEs connected to the multi-homed Ethernet segment.
To alleviate this issue, EVPN introduces the concept of Aliasing.
This refers to the ability of a PE to signal that it has reachability
to a given locally attached Ethernet segment, even when it has learnt
no MAC addresses from that segment. The Ethernet A-D per-EVI route
is used to that end. Remote PEs which receive MAC advertisement
routes with non-zero ESI SHOULD consider the MAC address as reachable
via all NVEs that advertise reachability to the relevant Segment
using Ethernet A-D routes with the same ESI and with the Single-
Active flag reset.
This procedure is impacted for virtual hub-and-spoke topology because
a given V-spoke does not receive any MAC/IP advertisements from
remote V-spokes; therefore, there is no point in propagating Ethernet
A-D per-EVI route to the remote V-spokes. In this solution, the V-
hubs terminate the Ethernet A-D per-EVI route (used for Aliasing) and
follows the procedures described in [RFC7432] for handling this
route.
There are scenarios for which it is desirable to establish direct
communication path between a pair of V-spokes for a given host MAC
address. In such scenario, the advertising V-spoke advertises both
the MAC/IP route and Ethernet A-D per-EVI route with the RT of V-hub
(RT-VH) per section 3 of [RFC7024]. The use of RT-VH, ensures that
these routes are received by the V-spokes associated with that V-hub
set and thus enables the V-spokes to perform the Aliasing procedure.
In summary, PE devices (V-hubs in general and V-spokes occasionally)
that receive EVPN MAC/IP route advertisements (associated with a
multi-homed site) need to also receive the associated Ethernet A-D
per-EVI route advertisement(s) in order for them to perform Aliasing
procedure.
5.4. Split-Horizon And Mass Withdraw
[RFC7432] uses Ethernet A-D per-ES route to a) signal to remote PEs
the multi-homing redundancy type (Single-Active versus All-Active),
b) advertise ESI label for split-horizon filtering when MPLS
encapsulation is used, and c) advertise mass-withdraw when a failure
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of an access interface impacts many MAC addresses. This route does
not need to be advertise from a V-spoke to any remote V-spoke unless
a direct communication path between a pair of spoke is needed for a
given flow.
Even if communication between a pair of V-spoke is needed for just a
single flow, the Ethernet A-D per ES route needs to be advertised
from the originating V-spoke for that ES which may handle tens or
hundreds of thousands of flows. This is because in order to perform
Aliasing function for a given flow, the Ethernet A-D per-EVI route is
needed and this route itself is dependent on the Ethernet A-D per-ES
route. In such scenario, the advertising V-spoke advertises the
Ethernet A-D per-ES route with the RT of V-hub (RT-VH) per section 3
of [RFC7024].
In summary, PE devices (V-hubs in general and V-spokes occasionally)
that receive EVPN MAC/IP route advertisements (associated with a
multi-homed site) need to also receive the associated Ethernet A-D
per-ES route advertisement(s).
6. Forwarding Considerations
6.1. IP-only Forwarding
When EVPN operates in IP-only forwarding mode using EVPN Route Type
5, then all forwarding considerations in section 4 of [RFC7024] are
directly applicable here.
6.2. MAC-only Forwarding - Bridging
When EVPN operates in MAC-only forwarding mode (i.e., bridging mode),
then for a given EVI, the MPLS label that a V-hub advertises with an
Unknown MAC address MUST be the label that identifies the MAC-VRF of
the V-hub in absense of a more specific MAC route. When the V-hub
receives a packet with such label, the V- hub pops the label and
determines further disposition of the packet based on the lookup in
the MAC-VRF. Otherwise, the MPLS label of the matching more specific
route is used and packet is is forwarded towards the associated
NEXTHOP of the more specific route.
6.3. MAC and IP Forwarding - IRB
When a EVPN speaker operates in IRB mode, it implements both the "IP
and MAC forwarding Modes" (aka Integrated Routing and Bridging -
IRB). On a packet by packet basis, the V-spoke decides whether to do
forwarding based on a MAC address lookup (bridge) or based on a IP
address lookup (route). If the host destination MAC address is that
of the IRB interface (i.e., if the traffic is inter-subnet), then the
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V-spoke performs an additional IP lookup in the IP-VRF. However, if
the host destination MAC address is that of an actual host MAC
address (i.e., the traffic is intra-subnet) , then the V-spoke only
performs a MAC lookup in the MAC-VRF. The procedure specified in
Section 6.1 and Section 6.2 are applicable to inter-subnet and intra-
subnet forwarding respectively. For intra-subnet traffic, if the MAC
address is not found in the MAC-VRF, then the V-spoke forwards the
traffic to the V-hub with the MPLS label received from the V-hub for
the unknown MAC address. For the Inter-subnet traffic, if the IP
prefix is not found in the IP-VRF, then the V-spoke forwards the
traffic to the V-hub with the MPLS label received from the V-hub for
the default IP address.
7. Handling of the Broadcast and Multicast traffic
The handling of the Broadcast and Multicast traffic should be done
according to the EVPN rules described in [RFC7432].
8. ARP/ND Suppression
[RFC7432] defines the procedures for ARP/ND suppression where a PE
can terminate gratuitous ARP/ND request message from directly
connected site and advertises the associated MAC and IP addresses in
an EVPN MAC/IP advertisement route to all other remote PEs. The
remote PEs that receive this EVPN route advertisement, install the
MAC/IP pair in their ARP/ND cache table thus enabling them to
terminate ARP/ND requests and generate ARP/ND responses locally thus
suppressing the flooding of ARP/ND requests over the EVPN network.
In this hub-and-spoke approach, the ARP suppression needs to be
performed by both the EVPN V-hubs as well V-spokes as follow. When a
V-Spoke receives a gratuitous ARP/ND request, it terminates it and
stores the source MAC/IP pair in its ARP/ND cache table. Then, it
advertises the source MAC/IP pair to its associated V-Hubs using EVPN
MAC/IP advertisement route. The V-Hubs upon receiving this EVPN
route advertisement, create an entry in their ARP/ND cache table for
this MAC/IP pair.
Now when a V-Spoke receives an ARP/ND request, it first looks up its
ARP cache table, if an entry for that MAC/IP pair is found, then an
ARP/ND response is generated locally and sent to the CE. However, if
an entry is not found, then the ARP/ND request is unicasted to one of
the V-hub associated with this V-spoke. Since, the associated V-hub
keeps all the MAC/IP ARP entries in its cache table, it can formulate
and ARP/ND response and forward it to that CE via the corresponding
V-spoke.
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9. IANA Considerations
This document does NOT make any new requests for IANA allocations.
10. Security Considerations
All the security considerations in [RFC7432] apply directly to this
document because this document leverages [RFC7432] control plane and
their associated procedures - although not the complete set but
rather a subset.
This draft does not introduce any new security considerations beyond
that of [RFC7432] and [RFC4761] because advertisements and processing
of B-MAC addresses follow that of [RFC7432] and processing of C-MAC
addresses follow that of [RFC4761] - i.e, B-MAC addresses are learned
in control plane and C-MAC addresses are learned in data plane.
11. Acknowledgements
The authors would like to thank Yakov Rekhter for initial idea
discussions.
12. Change Log
Initial Version: Sep 21 2014
13. References
13.1. Normative References
[I-D.ietf-l2vpn-evpn]
Sajassi, A., Aggarwal, R., Bitar, N., Isaac, A., and J.
Uttaro, "BGP MPLS Based Ethernet VPN", draft-ietf-l2vpn-
evpn-11 (work in progress), October 2014.
[RFC1771] Rekhter, Y. and T. Li, "A Border Gateway Protocol 4 (BGP-
4)", RFC 1771, March 1995.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
March 2000.
[RFC3484] Draves, R., "Default Address Selection for Internet
Protocol version 6 (IPv6)", RFC 3484, February 2003.
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[RFC3931] Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling
Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005.
[RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
for IPv6 Hosts and Routers", RFC 4213, October 2005.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC4374] McCobb, G., "The application/xv+xml Media Type", RFC 4374,
January 2006.
[RFC6459] Korhonen, J., Soininen, J., Patil, B., Savolainen, T.,
Bajko, G., and K. Iisakkila, "IPv6 in 3rd Generation
Partnership Project (3GPP) Evolved Packet System (EPS)",
RFC 6459, January 2012.
[RFC7024] Jeng, H., Uttaro, J., Jalil, L., Decraene, B., Rekhter,
Y., and R. Aggarwal, "Virtual Hub-and-Spoke in BGP/MPLS
VPNs", RFC 7024, October 2013.
[RFC7432] Sajassi, A., Aggarwal, R., Bitar, N., Isaac, A., Uttaro,
J., Drake, J., and W. Henderickx, "BGP MPLS-Based Ethernet
VPN", RFC 7432, February 2015.
13.2. Informative References
[I-D.drao-bgp-l3vpn-virtual-network-overlays]
Rao, D., Mullooly, J., and R. Fernando, "Layer-3 virtual
network overlays based on BGP Layer-3 VPNs", draft-drao-
bgp-l3vpn-virtual-network-overlays-03 (work in progress),
July 2014.
[I-D.ietf-bess-evpn-overlay]
Sajassi, A., Drake, J., Bitar, N., Isaac, A., Uttaro, J.,
and W. Henderickx, "A Network Virtualization Overlay
Solution using EVPN", draft-ietf-bess-evpn-overlay-01
(work in progress), February 2015.
[RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery
Proxies (ND Proxy)", RFC 4389, April 2006.
[RFC4761] Kompella, K. and Y. Rekhter, "Virtual Private LAN Service
(VPLS) Using BGP for Auto-Discovery and Signaling", RFC
4761, January 2007.
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[RFC7080] Sajassi, A., Salam, S., Bitar, N., and F. Balus, "Virtual
Private LAN Service (VPLS) Interoperability with Provider
Backbone Bridges", RFC 7080, December 2013.
[RFC7209] Sajassi, A., Aggarwal, R., Uttaro, J., Bitar, N.,
Henderickx, W., and A. Isaac, "Requirements for Ethernet
VPN (EVPN)", RFC 7209, May 2014.
Authors' Addresses
Keyur Patel
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95124 95134
USA
Email: keyupate@cisco.com
Ali Sajassi
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95124 95134
USA
Email: sajassi@cisco.com
John E. Drake
Juniper Networks, Inc.
Email: jdrake@juniper.net
Wim Henderickx
Alcatel-Lucent
Email: wim.henderickx@alcatel-lucent.com
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