IP Prefix Advertisement in E-VPN
draft-rabadan-l2vpn-evpn-prefix-advertisement-00
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
|
|
|---|---|---|---|
| Authors | Jorge Rabadan , Jorge Rabadan , Wim Henderickx , Senad Palislamovic , Senad Palislamovic , Florin Balus , Florin Balus , Aldrin Isaac | ||
| Last updated | 2013-07-15 | ||
| Replaced by | draft-ietf-bess-evpn-prefix-advertisement, RFC 9136 | ||
| RFC stream | (None) | ||
| Formats | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-rabadan-l2vpn-evpn-prefix-advertisement-00
L2VPN Workgroup J. Rabadan
Internet Draft W. Henderickx
S. Palislamovic
Intended status: Standards Track Alcatel-Lucent
F. Balus
Nuage Networks
A. Isaac
Bloomberg
Expires: January 16, 2014 July 15, 2013
IP Prefix Advertisement in E-VPN
draft-rabadan-l2vpn-evpn-prefix-advertisement-00
Abstract
E-VPN provides a flexible control plane that allows intra-subnet
connectivity in an IP/MPLS and/or an NVO-based network. In Data
Centers, there is also a need for a dynamic and efficient inter-
subnet connectivity across Tenant Systems and End Devices that can be
physical or virtual and may not support their own routing protocols.
This document defines a new E-VPN route type for the advertisement of
IP Prefixes and explains how E-VPN should be used to provide
inter-subnet connectivity with the flexibility required by the Data
Center applications.
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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material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
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http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
This Internet-Draft will expire on January 16, 2014.
Copyright Notice
Copyright (c) 2013 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
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described in the Simplified BSD License.
Table of Contents
1. Introduction and problem statement . . . . . . . . . . . . . . 3
1.1 Inter-subnet connectivity requirements in Data Centers . . . 3
1.2 The requirement for advertising IP prefixes in E-VPN . . . . 5
1.3 The requirement for a new E-VPN route type . . . . . . . . . 6
2. The BGP E-VPN IP Prefix route . . . . . . . . . . . . . . . . . 8
2.1. IP Prefix Route encoding . . . . . . . . . . . . . . . . . 9
2.2. BGP remote-next-hop attribute . . . . . . . . . . . . . . . 9
3. Procedures associated to the advertisement of IP Prefixes . . . 10
3.1. Usage of the MAC advertisement and IP Prefix
advertisement routes . . . . . . . . . . . . . . . . . . . 10
3.2. Inter-subnet connectivity for TS . . . . . . . . . . . . . 11
3.3. Inter-subnet connectivity for redundant TS (floating IP) . 13
3.4. Inter-subnet connectivity for IRB interfaces . . . . . . . 15
3.4.1. Inter-subnet connectivity for unnumbered IRB
interfaces . . . . . . . . . . . . . . . . . . . . . . 17
4. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . 19
5. Conventions used in this document . . . . . . . . . . . . . . . 20
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 20
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 20
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
8.1. Normative References . . . . . . . . . . . . . . . . . . . 20
8.2. Informative References . . . . . . . . . . . . . . . . . . 20
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 20
10. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 21
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1. Introduction and problem statement
Inter-subnet connectivity is required within the Data Center,
therefore IP Prefixes must be advertised in the control plane. This
section explains why IP-VPN [RFC4364] procedures cannot be used for
such advertisements and why the existing E-VPN MAC route type does
not meet the Data Center requirements for the advertisement of IP
Prefixes, hence a new E-VPN route type is proposed.
Section 1.1 describes the inter-subnet connectivity requirements in
Data Centers. Section 1.2 and 1.3 explain why neither IP-VPN nor the
existing E-VPN route types meet the requirements for IP Prefix
advertisements. Once the need for a new E-VPN route type is
justified, sections 2 and 3 will describe this route type and how it
is used in some specific use cases.
1.1 Inter-subnet connectivity requirements in Data Centers
[E-VPN] is used as the control plane for a Network Virtualization
Overlay (NVO3) solution in Data Centers (DC), where Network
Virtualization Edge (NVE) devices can be located in Hypervisors or
TORs, as described in [E-VPN-OVERLAYS].
If we use the term Tenant System (TS) to designate a physical or
virtual system identified by MAC and IP addresses, and connected to
an E-VPN instance, the following considerations apply:
o The Tenant Systems may be Virtual Machines (VMs) that generate
traffic from their own MAC and IP.
o The Tenant Systems may be Virtual Appliance entities (VAs) that
forward traffic to/from IP addresses of different End Devices
seating behind them.
o These VAs can be firewalls, load balancers, NAT devices, other
appliances or virtual gateways with virtual routing instances.
o These VAs do not have their own routing protocols and hence
rely on the E-VPN NVEs to advertise the routes on their
behalf.
o In all these cases, the VA will forward traffic to the Data
Center using its own source MAC but the source IP will be the
one associated to the End Device seating behind or a
translated IP address (part of a public NAT pool) if the VA is
performing NAT.
o Note that the same IP address could exist behind two of these
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TS. One example of this would be certain appliance resiliency
mechanisms, where a virtual IP or floating IP can be own by
one of the two VAs running the resiliency protocol (the master
VA). VRRP is one particular example of this. Another example
is multi-homed subnets, i.e. the same subnet is connected to
two VAs.
The following figure illustrates some of the examples described
above.
NVE1
+--------+
TS1(VM)--|(EVI-10)|---------+
IP1/M1 +--------+ | DGW1
+---------+ +-------------+
| |----|(EVI-10) |
SN1---+ NVE2 | | | IRB1\ |
| +--------+ | | | (VRF)|---+
SN2---TS2(VA)--|(EVI-10)|----| | +-------------+ _|_
| IP2/M2 +--------+ | VXLAN/ | ( )
IP4---+ <-+ | nvGRE | DGW2 ( WAN )
| | | +-------------+ (___)
vIP23 (floating) | |----|(EVI-10) | |
| +---------+ | IRB2\ | |
SN1---+ <-+ NVE3 | | | (VRF)|---+
| IP3/M3 +--------+ | | +-------------+
SN3---TS3(VA)--|(EVI-10)|------+ |
| +--------+ |
IP5---+ |
|
NVE4 |
+---------------------+ |
IP6------|(EVI-1) | |
| \ IRB3 | |
| (VRF)-(EVI-10)|--+
| / |
|---|(EVI-2) |
SN4| +---------------------+
Figure 1 DC inter-subnet use-cases
Where:
NVE1, NVE2, NVE3, NVE4, DGW1 and DGW2 share the same E-VPN for a
particular tenant. EVI-10 is the corresponding E-VPN instance on each
element, and all the hosts connected to that instance belong to the
same IP subnet. The hosts connected to E-VPN 10 are listed below:
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o TS1 is a VM that generates/receives traffic from/to IP1, where
IP1 belongs to the E-VPN 10 subnet.
o TS2 and TS3 are Virtual Appliances (VA) that generate/receive
traffic from/to the subnets and hosts seating behind them
(SN1, SN2, SN3, IP4 and IP5). Their IP addresses (IP2 and IP3)
belong to the E-VPN subnet and they can also generate/receive
traffic. When these VAs receive packets destined to their own
MAC addresses (M2 and M3) they will route the packets to the
proper subnet or host. These VAs do not support routing
protocols to advertise the subnets connected to them and can
move to a different server and NVE when the Cloud Management
System decides to do so. These VAs may also support redundancy
mechanisms for some subnets, similar to VRRP, where a floating
IP is owned by the master VA and only the master VA forwards
traffic to a given subnet. E.g.: vIP23 in figure 1 is a
floating IP that can be owned by TS2 or TS3 depending on who
the master is. Only the master will forward traffic to SN1.
o Integrated Routing and Bridging interfaces IRB1, IRB2 and IRB3
have their own IP addresses that belong to the E-VPN 10 subnet
too. These IRB interfaces connect the E-VPN 10 subnet to
Virtual Routing and Forwarding (VRF) instances that can route
the traffic to other connected subnets for the same tenant
(within the DC or at the other end of the WAN). In some
occasions, the IRB interfaces do not terminate IP traffic
themselves and therefore they do not need any IP address
configured. In such case, we will refer to these special IRB
interfaces as "unnumbered" IRB interfaces.
All the above DC use cases use individual IP hosts and subnets for
intra/inter connectivity. Therefore, their IP addresses MUST be
advertised:
a) From the NVEs (since VAs and VMs do not run routing protocols) and
b) Associated to a next-hop that can be a VA IP address, a floating
IP address, and IRB IP address or a MAC address.
1.2 The requirement for advertising IP prefixes in E-VPN
In all the inter-subnet connectivity cases discussed in section 1.1
there is a need to advertise IP prefixes in the control plane that
cannot be satisfied by using [RFC4364] due to the following
requirements, specific to NVO-based Data Centers:
o The data plane in NVO-based Data Centers is not based on IP
over a GRE or MPLS tunnel as required by [RFC4364], but
Ethernet over an IP tunnel, such as VXLAN or NVGRE.
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o The IP prefixes in the DC must be advertised with a
flexibility that does not exist in IP-VPNs. For instance:
a) The advertised next-hop for a given IP prefix can be an
IRB IP address (see section 3.4), a floating IP address (see
section 3.3) or even a MAC address (see section 3.4.1). In
the future, the ESI could also be defined as a next-hop for
the advertised prefixes.
b) As stated by [E-VPN-OVERLAYS], VXLAN or NVGRE virtual
identifiers can have a global or a local scope. The
implementation MUST support the flexibility to advertise IP
Prefixes associated to a global identifier (32-bit value
encoded in the E-VPN Ethernet Tag ID) or a locally
significant identifier (20-bit value encoded in the MPLS
label field). At the moment, [RFC4364] can only advertise
Prefixes associated to a locally significant identifier
(MPLS label).
o IP prefixes must be advertised by NVE devices that have no VRF
instances defined and no capability to process IP-VPN
prefixes. These NVE devices just support E-VPN and advertise
IP Prefixes on behalf of some connected Tenant Systems. In
other words: any attempt to solve this problem by simply using
[RFC4364] routes requires that any EVPN deployment must be
accompanied with a concurrent IP-VPN topology, which is not
possible in most of the cases.
o Finally, Data Center providers want to use a single BGP
Subsequent Address Family (AFI/SAFI) for the advertisement of
addresses within the Data Center, i.e. BGP E-VPN only, as
opposed to using E-VPN and IP-VPN in a concurrent topology.
This minimizes the control plane overhead in TORs and
Hypervisors and simplifies the operations.
E-VPN is extended - as described in this document - to advertise IP
prefixes with the flexibility required by the current and future Data
Center applications.
1.3 The requirement for a new E-VPN route type
[E-VPN] defines a MAC route (or route type 2) where a MAC address can
be advertised together with an IP address length (IPL) and IP address
(IP). While a variable IPL might be used to indicate the presence of
an IP prefix in a route type 2, there are several specific use cases
in which using this route type to deliver IP Prefixes is not
suitable.
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One example of such use cases is the "floating IP" example described
in section 1.1. In this example we need to decouple the advertisement
of the prefixes from the advertisement of the floating IP (vIP23 in
figure 1) and MAC associated to it, otherwise the solution gets
highly inefficient and does not scale.
E.g.: if we are advertising 1k prefixes from M2 (using route type 2)
and the floating IP owner changes from M2 to M3, we would need to
withdraw 1k routes from M2 and re-advertise 1k routes from M3.
However if we use a separate route type, we can advertise the 1k
routes associated to the floating IP address (vIP23) and only one
route type 2 for advertising the ownership of the floating IP, i.e.
vIP23 and M2 in the route type 2. When the floating IP owner changes
from M2 to M3, a single route type 2 withdraw/update is required to
indicate the change. The remote DGW will not change any of the 1k
prefixes associated to vIP23, but will only update the ARP resolution
entry for vIP23 (now pointing at M3).
Any other attempt to improve the efficiency of the solution when
using non-MAC-decoupled Prefix advertisements, will derive in
dependencies on the Cloud Management System (if ESIs are to be used)
and changes in the current E-VPN semantics. The DC applications
require mechanisms to provide IP Prefix resiliency independent of the
E-VPN procedures.
Other reasons to decouple the IP Prefix advertisement from the MAC
route are listed below:
o Clean identification, operation of troubleshooting of IP
Prefixes, not subject to interpretation and independent of the
IPL and the IP value. E.g.: An IP address for ARP resolution
must be always clearly distinguished from an /32 IP Prefix, or
a default IP route 0.0.0.0/0 must always be easily and clearly
distinguished from the absence of IP information.
o MAC address information must not be compared by BGP when
selecting two IP Prefix routes. If IP Prefixes are to be
advertised using MAC routes, the MAC information is always
present and part of the route key.
o IP Prefix routes must not be subject to MAC route procedures
such as MAC Mobility or aliasing. Prefixes advertised from two
different ESIs do not mean mobility; MACs advertised from two
different ESIs do mean mobility. Similarly load balancing for
IP prefixes is achieved through IP mechanisms such as ECMP,
and not through MAC route mechanisms such as aliasing.
o NVEs that do not require processing IP Prefixes must have an
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easy way to identify an update with an IP Prefix and ignore
it, rather than processing the MAC route only to find out
later that it carries a Prefix that must be ignored.
The following sections describe how E-VPN is extended with a new
route type for the advertisement of prefixes and how this route is
used to address the current and future inter-subnet connectivity
requirements existing in the Data Center.
2. The BGP E-VPN IP Prefix route
The current BGP E-VPN NLRI as defined in [E-VPN] is shown below:
+-----------------------------------+
| Route Type (1 octet) |
+-----------------------------------+
| Length (1 octet) |
+-----------------------------------+
| Route Type specific (variable) |
+-----------------------------------+
Where the route type field can contain one of the following specific
values:
+ 1 - Ethernet Auto-Discovery (A-D) route
+ 2 - MAC advertisement route
+ 3 - Inclusive Multicast Route
+ 4 - Ethernet Segment Route
This document defines an additional route type that will be used for
the advertisement of IP Prefixes:
+ 5 - IP Prefix Route
The support for this new route type is OPTIONAL.
By using a separate route type for IP prefix advertisements, there is
a clean separation of functions between route types, i.e. route type
2 or MAC Advertisement route will be used for MAC and ARP resolution
advertisement, whereas route type 5 or IP Prefix route will be used
for the advertisement of prefixes. Since this new route type is
OPTIONAL, an implementation not supporting it will easily ignore the
route, based on the route type value.
The detailed encoding of this route and associated procedures are
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described in the following sections.
2.1. IP Prefix Route encoding
An IP Prefix advertisement route type specific E-VPN NLRI consists of
the following fields:
+---------------------------------------+
| RD (8 octets) |
+---------------------------------------+
|Ethernet Segment Identifier (10 octets)|
+---------------------------------------+
| Ethernet Tag ID (4 octets) |
+---------------------------------------+
| IP Address Length (1 octet) |
+---------------------------------------+
| IP Address (4 or 16 octets) |
+---------------------------------------+
| MPLS Label (3 octets) |
+---------------------------------------+
Where:
o RD, Ethernet Tag ID and MPLS Label fields will be used as
defined in [E-VPN] and [E-VPN-OVERLAYS].
o The Ethernet Segment Identifier will be zero for IP prefix
advertisements in this version of the document, and be re-used
in the future for other purposes.
o The IP address length can be set to a value between 0 and 32
(bits) for ipv4 and between 0 and 128 for ipv6.
o The IP address will be a 32 or 128-bit field (ipv4 or ipv6).
o The total route length will indicate the type of prefix (ipv4
or ipv6).
The Eth-Tag ID, IP address length and IP address will be part of the
route key used by BGP to compare routes. The rest of the fields will
be out of the route key.
2.2. BGP remote-next-hop attribute
The BGP remote-next-hop attribute [BGP-REMOTE-NH] will be sent along
with the IP Prefix advertisement to indicate the next-hop behind
which the advertised prefix is located. The following table shows the
different types of next-hops defined in this document and their
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corresponding encoding in the BGP remote-next-hop attribute.
+--------------------+----------------------------------+
| Prefix next-hop | Field in the remote-nh attribute |
+--------------------+----------------------------------+
| MAC address | sub-TLV (for VXLAN or NVGRE) |
| IRB IP address | tunnel address (ipv4 or ipv6) |
| Floating IP address| tunnel address (ipv4 or ipv6) |
+--------------------+----------------------------------+
3. Procedures associated to the advertisement of IP Prefixes
This section describes the separate function of each E-VPN
advertisement route: route type 2 for MAC/IP advertisements and route
type 5 for IP Prefixes.
After defining the role of each route type and the benefits of using
a separate route for IP Prefixes, the procedures associated to the
advertisement of prefixes will be explained in three different use
cases.
3.1. Usage of the MAC advertisement and IP Prefix advertisement routes
[E-VPN] describes the content of the BGP E-VPN route type 2 specific
NLRI, i.e. MAC Advertisement Route, where the IP address length (IPL)
and IP address (IP) of a specific advertised MAC are encoded. The
subject of the MAC advertisement route is the MAC address (M) and MAC
address length (ML) encoded in the route. The MAC mobility and other
complex procedures are defined around that MAC address. The IP
address information carries the host IP address required for the ARP
resolution of the MAC.
The BGP E-VPN route type 5 defined in this document, i.e. IP Prefix
Advertisement route, decouples the advertisement of IP prefixes from
the advertisement of any MAC address related to it. This brings some
major benefits to NVO-based networks where inter-subnet forwarding is
required. Some of those benefits are:
a) Upon receiving a route type 2 or type 5, an egress NVE can easily
distinguish MACs and IPs for ARP resolution from IP Prefixes. E.g.
an IP prefix with IPL=32 being advertised from two different
ingress NVEs (as route type 5) can be identified as such and be
imported in the designated routing context as two ECMP routes, as
opposed to two ARP entries competing for the same IP.
b) Similarly, upon receiving a route, an egress NVE not supporting
processing IP Prefixes can easily ignore the update, based on the
route type.
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c) A MAC route includes the ML, M, IPL and IP in the route key that
is used by BGP to compare routes. Advertised IP Prefixes are
imported into the designated routing context, where there is no
MAC information associated to IP routes. In the example
illustrated in figure 1, subnet SN1 should be advertised by NVE2
and NVE3 and interpreted by DGW1 as the same route coming from two
different next-hops, regardless of the MAC address associated to
TS2 or TS3. This is easily accomplished in the route type 5 by
including only the IP information in the route key.
d) By decoupling the MAC from the IP Prefix advertisement procedures,
we can leave the IP prefix advertisements out of the MAC mobility
procedures defined in [E-VPN] for MACs. In addition, this allows
us to have an indirection mechanism for IP prefixes advertised
from a MAC/IP that can move between hypervisors. E.g. if there are
1,000 prefixes seating behind TS2 (figure 1), NVE2 will advertise
all those prefixes in type 5 routes associated to the next-hop
IP2. Should TS2 move to a different NVE, a single MAC
advertisement route withdraw for the M2/IP2 route from NVE2 will
invalidate the 1,000 prefixes, as opposed to have to wait for each
individual prefix to be withdrawn. This may be easily accomplished
by using a different IP Prefix route type that is not tied to a
MAC address.
3.2. Inter-subnet connectivity for TS
The following figure illustrates an example of inter-subnet
forwarding for subnets seating behind Virtual Appliances (on TS2 and
TS3).
SN1---+ NVE2 DGW1
| +--------+ +---------+ +-------------+
SN2---TS2(VA)--|(EVI-10)|----| |----|(EVI-10) |
| IP2/M2 +--------+ | | | IRB1\ |
IP4---+ | | | (VRF)|---+
| | +-------------+ _|_
| VXLAN/ | ( )
| nvGRE | DGW2 ( WAN )
SN1---+ NVE3 | | +-------------+ (___)
| IP3/M3 +--------+ | |----|(EVI-10) | |
SN3---TS3(VA)--|(EVI-10)|----| | | IRB2\ | |
| +--------+ +---------+ | (VRF)|---+
IP5---+ +-------------+
Figure 2 Inter-subnet forwarding for TS
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An example of inter-subnet forwarding between subnet SN1/24 and a
subnet seating in the WAN is described below. NVE2, NVE3, DGW1 and
DGW2 are running BGP E-VPN. TS2 and TS3 do not support routing
protocols, only a static route to forward the traffic to the WAN.
(1) NVE2 advertises the following BGP routes on behalf of TS2:
o Route type 2 (MAC route) containing: ML=48, M=M2, IPL=32,
IP=IP2
o Route type 5 (IP Prefix route) containing: IPL=24, IP=SN1,
remote-nh tunnel address=IP2
(2) NVE3 advertises the following BGP routes on behalf of TS3:
o Route type 2 (MAC route) containing: ML=48, M=M3, IPL=32,
IP=IP3
o Route type 5 (IP Prefix route) containing: IPL=24, IP=SN1,
remote-nh tunnel address=IP3
(3) DGW1 and DGW2 import both received routes based on the RT:
o Based on the EVI-10 route-target in DGW1 and DGW2, the MAC
route is imported and M2 is added to the EVI-10 MAC FIB along
with its corresponding tunnel information. For the VXLAN use
case, the VTEP will be derived from the MAC route BGP next-hop
and VNI from the Ethernet Tag or MPLS fields (see [E-VPN-
OVERLAYS]). IP2 - M2 is added to the ARP table.
o Based on the EVI-10 route-target in DGW1 and DGW2, the IP
Prefix route is also imported and SN1/24 is added to the
designated routing context with next-hop IP2 pointing at the
local EVI-10. Should ECMP be enabled in the routing context,
SN1/24 would also be added to the routing table with next-hop
IP3.
(4) When DGW1 receives a packet from the WAN with destination IPx,
where IPx belongs to SN1/24:
o A destination IP lookup is performed on the DGW1 VRF routing
table and next-hop=IP2 is found. The tunnel information to
encapsulate the packet will be derived from the route-type 2
(MAC route) received for M2/IP2.
o IP2 is resolved to M2 in the ARP table, and M2 is resolved to
the tunnel information given by the MAC FIB (remote VTEP and
VNI for the VXLAN case).
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o The IP packet destined to IPx is encapsulated with:
. Source inner MAC = IRB1 MAC
. Destination inner MAC = M2
. Tunnel information provided by the MAC FIB (VNI, VTEP IPs
and MACs for the VXLAN case)
(5) When the packet arrives at NVE2:
o Based on the tunnel information (VNI for the VXLAN case), the
EVI-10 context is identified for a MAC lookup.
o Encapsulation is stripped-off and based on a MAC lookup
(assuming MAC forwarding on the egress NVE), the packet is
forwarded to TS2, where it will be properly routed.
(5) Should TS2 move from NVE2 to NVE3, MAC Mobility procedures will
be applied to the MAC route IP2/M2, as defined in [EVPN]. Route type
5 prefixes are not subject to MAC mobility procedures, hence no
changes in the DGW VRF routing table will occur for TS2 mobility,
i.e. all the prefixes will still be pointing at IP2 as next-hop.
There is an indirection for e.g. SN1/24, which still points at
next-hop IP2 in the routing table, but IP2 will be simply resolved to
a different tunnel, based on the outcome of the MAC mobility
procedures for the MAC route IP2/M2.
Note that in the opposite direction, TS2 will send traffic based on
its static-route next-hop information (IRB1 and/or IRB2), and regular
E-VPN procedures will be applied.
3.3. Inter-subnet connectivity for redundant TS (floating IP)
Sometimes Tenant Systems (TS) work in active/standby mode where an
upstream floating IP - owned by the active TS - is used as the next-
hop to get to some subnets behind. This redundancy mode, alredy
introduced in section 1.1 and 1.3, is illustrated in Figure 3.
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NVE2 DGW1
+--------+ +---------+ +-------------+
+---TS2(VA)--|(EVI-10)|----| |----|(EVI-10) |
| IP2/M2 +--------+ | | | IRB1\ |
| <-+ | | | (VRF)|---+
| | | | +-------------+ _|_
SN1 vIP23 (floating) | VXLAN/ | ( )
| | | nvGRE | DGW2 ( WAN )
| <-+ NVE3 | | +-------------+ (___)
| IP3/M3 +--------+ | |----|(EVI-10) | |
+---TS3(VA)--|(EVI-10)|----| | | IRB2\ | |
+--------+ +---------+ | (VRF)|---+
+-------------+
Figure 3 Inter-subnet forwarding for redundant TS
In this example, assuming TS2 is the active TS and owns IP23:
(1) NVE2 advertises the following BGP routes for TS2:
o Route type 2 (MAC route) containing: ML=48, M=M2, IPL=32,
IP=IP23
o Route type 5 (IP Prefix route) containing: IPL=24, IP=SN1,
remote-nh tunnel address=IP23
(2) NVE3 advertises the following BGP routes for TS3:
o Route type 5 (IP Prefix route) containing: IPL=24, IP=SN1,
remote-nh tunnel address=IP23
(3) DGW1 and DGW2 import both received routes based on the RT:
o M2 is added to the EVI-10 MAC FIB along with its corresponding
tunnel information. For the VXLAN use case, the VTEP will be
derived from the MAC route BGP next-hop and VNI from the
Ethernet Tag or MPLS fields (see [E-VPN-OVERLAYS]). IP23 - M2
is added to the ARP table.
o SN1/24 is added to the designated routing context in DGW1 and
DGW2 with next-hop IP23 pointing at the local EVI-10.
(4) When DGW1 receives a packet from the WAN with destination IPx,
where IPx belongs to SN1/24:
o A destination IP lookup is performed on the DGW1 VRF routing
table and next-hop=IP23 is found. The tunnel information to
encapsulate the packet will be derived from the route-type 2
(MAC route) received for M2/IP23.
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o IP23 is resolved to M2 in the ARP table, and M2 is resolved to
the tunnel information given by the MAC FIB (remote VTEP and
VNI for the VXLAN case).
o The IP packet destined to IPx is encapsulated with:
. Source inner MAC = IRB1 MAC
. Destination inner MAC = M2
. Tunnel information provided by the MAC FIB (VNI, VTEP IPs
and MACs for the VXLAN case)
(5) When the packet arrives at NVE2:
o Based on the tunnel information (VNI for the VXLAN case), the
EVI-10 context is identified for a MAC lookup.
o Encapsulation is stripped-off and based on a MAC lookup
(assuming MAC forwarding on the egress NVE), the packet is
forwarded to TS2, where it will be properly routed.
(5) When the redundancy protocol running between TS2 and TS3 appoints
TS3 as the new active TS for SN1, TS3 will now own the floating IP23
and will signal this new ownership (GARP message or similar). Upon
receiving the new owner's notification, NVE3 will issue a route type
2 for M3-IP23. DGW1 and DGW2 will update their ARP tables with the
new MAC resolving the floating IP. No changes are carried out in the
VRF routing table.
In the DGW1/2 BGP RIB, there will be two route type 5 routes for SN1
(from NVE2 and NVE3) but only the one with the same BGP next-hop as
the IP23 route type 2 BGP next-hop will be valid.
3.4. Inter-subnet connectivity for IRB interfaces
In some other cases, the NVEs and DGWs will have just IRB interfaces
as hosts in the E-VPN instance. Figure 4 illustrates an example.
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NVE1
+---------------------+ DGW1
IP1---|(EVI-1) | +-------------+
| \ IRB3 | +---------+ |(EVI-10) |
| (VRF)-(EVI-10)|--| |--| IRB1\ |
| / | | | | (VRF)|---+
|-|(EVI-2) | | | +-------------+ _|_
SN1| +---------------------+ | | ( )
| +---------------------+ | VXLAN/ | DGW2 ( WAN )
|-|(EVI-2) | | nvGRE | +-------------+ (___)
| \ IRB4 | | | |(EVI-10) | |
| (VRF)-(EVI-10)|--| |--| IRB2\ | |
| / | +---------+ | (VRF)|---+
SN2---|(EVI-3) | +-------------+
+---------------------+
NVE2
Figure 4 Inter-subnet forwarding for IRB interfaces
In this case:
(1) NVE1 advertises the following BGP routes for SN1 resolution:
o Route type 2 (MAC route) containing: ML=48, M=IRB3-MAC,
IPL=32, IP=IRB3-IP
o Route type 5 (IP Prefix route) containing: IPL=24, IP=SN1,
remote-nh tunnel address=IRB3-IP
(2) NVE2 advertises the following BGP routes for SN1 resolution:
o Route type 2 (MAC route) containing: ML=48, M=IRB4-MAC,
IPL=32, IP=IRB4-IP
o Route type 5 (IP Prefix route) containing: IPL=24, IP=SN1,
remote-nh tunnel address=IRB4-IP
(3) DGW1 and DGW2 import both received routes based on the RT:
o IRB3-MAC and IRB4-MAC are added to the EVI-10 MAC FIB along
with their corresponding tunnel information. For the VXLAN use
case, the VTEP will be derived from the MAC route BGP next-hop
and VNI from the Ethernet Tag or MPLS fields (see [E-VPN-
OVERLAYS]). IRB3-MAC - IRB3-IP and IRB4-MAC - IRB4-IP are
added to the ARP table.
o SN1/24 is added to the designated routing context in DGW1 and
DGW2 with next-hop IRB3-IP (and/or IRB4-IP) pointing at the
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local EVI-10.
Similar forwarding procedures as the ones described in the previous
use-cases are followed.
3.4.1. Inter-subnet connectivity for unnumbered IRB interfaces
In the previous example, the E-VPN instance can connect IRB
interfaces and any other Tenant Systems connected to it. E-VPN
provides connectivity for:
a) Traffic destined to the IRB IP interfaces as well as
b) Traffic destined to IP subnets seating behind the IRB interfaces,
e.g. SN1 or SN2.
In order to provide connectivity for (a) we need MAC routes (route-
type 2) distributing IRB MACs and IPs. Connectivity type (b) is
accomplished by the exchange of IP Prefix routes (route-type 5) for
IPs and subnets seating behind IRBs. As discussed in this document,
prefixes are advertised along with their corresponding remote
next-hop tunnel address, and those tunnel addresses are used to link
prefixes to MAC/IPs advertised in MAC routes (type 2).
In some cases, connectivity type (a) (see above) is not required and
the E-VPN instance is connecting only IRB interfaces, which are never
the final destination of any packet. This use case is depicted in the
diagram below and we refer to it as the "unnumbered IRB interface"
use-case:
NVE1
+------------+
IP1-----|(EVI-1) | DGW1
| \ | +---------+ +-----+
| (VRF)|----| |----|(VRF)|----+
| / | | | +-----+ |
|---|(EVI-2) | | | _|_
| +------------+ | | ( )
SN1| | VXLAN/ | ( WAN )
| NVE2 | nvGRE | (___)
| +------------+ | | |
|---|(EVI-2) | | | DGW2 |
| \ | | | +-----+ |
| (VRF)|----| |----|(VRF)|----+
| / | +---------+ +-----+
SN2-----|(EVI-3) |
+------------+
Figure 5 Inter-subnet forwarding for unnumbered IRB interfaces
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In this case, we need to provide connectivity from/to IP hosts in
SN1, SN2, IP1 and hosts seating at the other end of the WAN. The
E-VPN in the core just connects all the IRBs in NVE1, NVE2, DGW1 and
DGW2 but there will not be any IP host in this core E-VPN that is the
final destination of any IP packet.
Therefore there is no need to define IRB IP addresses (IRBs are not
represented in the diagram). This is the reason why we refer to this
solution as "unnumbered Ethernet IRB" solution.
In this case, the proposal is to use EVPN type 5 routes and the BGP
Remote-Next-Hop attribute, where the following information is
carried:
o Route type 5 Eth-Tag ID can contain the core instance VNI (if
the VNI is global, otherwise, for local significant VNIs, an
MPLS label field may be added with a 20-bit VNI encoded in the
label space, as per [E-VPN-OVERLAYS]).
o Route type 5 IP address length and IP address, as explained in
the previous section.
o Remote next-hop Tunnel Type is: TBD for VXLAN and TBD for
NVGRE (TBD by IANA).
o Remote next-hop Tunnel Address is populated with zeros,
meaning that the prefix next-hop is an "unnumbered IRB".
o Remote next-hop sub-TLV (for VXLAN/NVGRE) in the Tunnel
Parameters field: contains the next-hop MAC address associated
to the unnumbered IRB interface. This MAC address identifies
the NVE/DGW and can be re-used for all the VRFs in the node.
Example of prefix advertisement for the ipv4 prefix SN1/24 advertised
from NVE1:
(1) NVE1 advertises the following BGP route for SN1:
o Route type 5 (IP Prefix route) containing: Eth-Tag=VNI=10
(assuming global VNI), IPL=24, IP=SN1. In addition to that, a
Remote-NH attribute will be sent, where: Tunnel-type= VXLAN or
NVGRE and a Sub-TLV will contain a MAC address= NVE1 MAC.
o As discussed, no MAC route is advertised for this core evpn.
(2) DGW1 imports the received route from NVE1 and SN1/24 is added to
the designated routing context. The next-hop for SN1/24 will be given
by the route type 5 BGP next-hop (NVE1), which is resolved to a
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tunnel. For instance: if the tunnel is VXLAN based, the BGP next-hop
will be resolved to a VXLAN tunnel where: destination-VTEP= NVE1 IP,
VNI=10, inner destination MAC = NVE1 MAC (derived from the remote-nh
attribute).
(3) When DGW1 receives a packet from the WAN with destination IPx,
where IPx belongs to SN1/24:
o A destination IP lookup is performed on the DGW1 VRF routing
table and next-hop= "NVE1 IP" is found. The tunnel information
to encapsulate the packet will be derived from the route-type
5 received for SN1.
o The IP packet destined to IPx is encapsulated with: Source
inner MAC = DGW1 MAC, Destination inner MAC = NVE1 MAC, Source
outer IP (source VTEP) = DGW1 IP, Destination outer IP
(destination VTEP) = NVE1 IP
(4) When the packet arrives at NVE1:
o Based on the tunnel information (VNI for the VXLAN case), the
routing context is identified for an IP lookup.
o An IP lookup is performed in the routing context, where SN1
turns out to be a local subnet associated to EVI-2. A
subsequent lookup in the ARP table and the EVI-2 MAC FIB will
return the forwarding information for the packet in EVI-2.
4. Conclusions
A new E-VPN route type 5 for the advertisement of IP Prefixes is
proposed in this document. This new route type will have a
differentiated role from the route type 2, i.e. MAC advertisement
route, and will address all the inter-subnet connectivity scenarios
which are required in the Data Center. As discussed throughout the
document, IP-VPN cannot be used in an NVO-based DC to advertise IP
Prefixes and the existing E-VPN route type 2 does not meet the
requirements for all the DC use cases, therefore a new E-VPN route
type is required.
This new E-VPN route type 5 decouples the IP Prefix advertisements
from the MAC route advertisements in E-VPN, hence:
a) Allows the clean and clear announcements of ipv4 or ipv6 prefixes
in an NLRI with no MAC addresses in the route key, so that only IP
information is used in BGP route comparisons.
b) Since the route type is different from the MAC advertisement
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route, the advertisement of prefixes will be excluded from all the
procedures defined for the advertisement of VM MACs, e.g. MAC
Mobility or aliasing. As a result of that, the current E-VPN
procedures do not need to be modified.
c) Allows a flexible implementation where the prefix can be linked to
different types of next-hops: MAC address, IP address, IRB IP
address, ESI, etc. and these MAC or IP addresses do not need to
reside in the advertising NVE.
d) An E-VPN implementation not requiring IP Prefixes can simply
discard them by looking at the route type value.
5. 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 RFC-2119 [RFC2119].
6. Security Considerations
7. IANA Considerations
8. References
8.1. Normative References
[RFC4364]Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, February 2006.
8.2. Informative References
[E-VPN] Sajassi et al., "BGP MPLS Based Ethernet VPN", draft-ietf-
l2vpn-evpn-03.txt, work in progress, February, 2013
[E-VPN-OVERLAYS] Sajassi-Drake et al., "A Network Virtualization
Overlay Solution using E-VPN", draft-sd-l2vpn-evpn-overlay-01.txt,
work in progress, February, 2013
[BGP-REMOTE-NH] Van de Velde et al., "BGP Remote-Next-Hop",
draft-vandevelde-idr-remote-next-hop-03.txt, work in progress,
October, 2012
9. Acknowledgments
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The authors would like to thank Mukul Katiyar and Senthil Sathappan
for their valuable feedback and contributions.
10. Authors' Addresses
Jorge Rabadan
Alcatel-Lucent
777 E. Middlefield Road
Mountain View, CA 94043 USA
Email: jorge.rabadan@alcatel-lucent.com
Wim Henderickx
Alcatel-Lucent
Email: wim.henderickx@alcatel-lucent.com
Florin Balus
Nuage Networks
Email: florin@nuagenetworks.net
Aldrin Isaac
Bloomberg
Email: aisaac71@bloomberg.net
Senad Palislamovic
Alcatel-Lucent
Email: senad.palislamovic@alcatel-lucent.com
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