INTERNET-DRAFT Luyuan Fang
Intended Status: Standards track David Ward
Expires: January 15, 2014 Rex Fernando
Cisco
Ning So Maria Napierala
TATA Communications AT&T
Jim Guichard Nabil Bitar
Cisco Verizon
Wen Wang Dhananjaya Rao
CenturyLink Cisco
Manuel Paul Bruno Rijsman
Deutsche Telekom Juniper
July 15, 2013
BGP IP VPN Virtual PE
draft-fang-l3vpn-virtual-pe-03
Abstract
This document describes the architecture solutions for BGP/MPLS IP
Virtual Private Networks (VPNs) with virtual Provider Edge (vPE)
routers. It provides a functional description of the vPE control
plane, the data plane, and the provisioning management process. The
vPE solutions supports both Software Defined Networking (SDN)
approach by allowing physical decoupling of the control and the
forwarding plane of a vPE, as well as a distributed routing approach.
These solutions allow vPE to be co-resident with the application
virtual machines (VMs) on a single end device, such as a server, as
well as on a Top-of-Rack switch (ToR), or in any network or compute
device. The ability to provide end-to-end native BGP IP VPN
connections between a Data Center (DC) (and/or other types of service
network) applications and the Enterprise IP VPN sites is highly
desirable to both Service Providers and Enterprises.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as
Internet-Drafts.
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Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference
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Copyright and License 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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Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Motivation and requirements . . . . . . . . . . . . . . . . 5
2. Virtual PE Architecture . . . . . . . . . . . . . . . . . . . . 6
2.1 Virtual PE definitions . . . . . . . . . . . . . . . . . . . 6
2.2 vPE Architecture and Design options . . . . . . . . . . . . 7
2.2.1 vPE-F host location . . . . . . . . . . . . . . . . . . 7
2.2.2 vPE control plane topology . . . . . . . . . . . . . . . 7
2.2.3 Data Center orchestration models . . . . . . . . . . . . 8
2.3 vPE Architecture reference models . . . . . . . . . . . . . 8
2.3.1 vPE-F in an end-device and vPE-C in the controller . . . 8
2.3.2 vPE-F and vPE-C on the same end-device . . . . . . . . . 9
2.3.3 vPE-F and vPE-C are on the ToR . . . . . . . . . . . . . 10
2.3.4 vPE-F on the ToR and vPE-C on the controller . . . . . . 12
2.3.5 Server view of vPE . . . . . . . . . . . . . . . . . . . 12
3. Control Plane . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.1 vPE Control Plane (vPE-C) . . . . . . . . . . . . . . . . . 13
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3.1.1 SDN approach . . . . . . . . . . . . . . . . . . . . . . 13
3.1.2 Distributed control plane . . . . . . . . . . . . . . . 14
3.3 Use of router reflector . . . . . . . . . . . . . . . . . . 14
3.4 Use of Constrained Route Distribution [RFC4684] . . . . . . 14
4. Forwarding Plane . . . . . . . . . . . . . . . . . . . . . . . 14
4.1 Virtual Interface . . . . . . . . . . . . . . . . . . . . . 14
4.2 Virtual Provider Edge Forwarder (vPE-F) . . . . . . . . . . 15
4.3 Encapsulation . . . . . . . . . . . . . . . . . . . . . . . 15
4.4 Optimal forwarding . . . . . . . . . . . . . . . . . . . . . 16
4.5 Routing and Bridging Services . . . . . . . . . . . . . . . 16
5. Addressing . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.1 IPv4 and IPv6 support . . . . . . . . . . . . . . . . . . . 17
5.2 Address space separation . . . . . . . . . . . . . . . . . . 17
6.0 Inter-connection considerations . . . . . . . . . . . . . . 17
7. Management, Control, and Orchestration . . . . . . . . . . . . 19
7.1 Assumptions . . . . . . . . . . . . . . . . . . . . . . . . 19
7.2 Management/Orchestration system interfaces . . . . . . . . . 19
7.3 Service VM Management . . . . . . . . . . . . . . . . . . . 20
7.4 Orchestration and IP VPN inter-provisioning . . . . . . . . 20
7.4.1 vPE Push model . . . . . . . . . . . . . . . . . . . . . 20
7.4.2 vPE Pull model . . . . . . . . . . . . . . . . . . . . . 21
7. Security Considerations . . . . . . . . . . . . . . . . . . . 22
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22
9.1 Normative References . . . . . . . . . . . . . . . . . . . 22
9.2 Informative References . . . . . . . . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24
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1 Introduction
Network virtualization enables multiple isolated individual networks
over a shared common network infrastructure. BGP/MPLS IP Virtual
Private Networks (IP VPNs) [RFC4364] have been widely deployed to
provide network based IP VPNs solutions. [RFC4364] provides routing
isolation among different customer VPNs and allow address overlapping
among these VPNs through the implementation of per VPN Virtual
Routing and Forwarding instances (VRFs) at a Service Provider Edge
(PE) routers, while forwarding customer traffic over a common IP/MPLS
network infrastructure.
With the advent of compute capabilities and the proliferation of
virtualization in Data Center servers, a multi-tenant Data Center
becomes a reality. As applications and appliances are increasingly
being virtualized, support for virtual edge devices, such as virtual
IP VPN PE routers, becomes feasible and a natural part of the overall
virtualization solutions. There is a strong desire from Service
Providers to extend their existing BGP IP VPN deployments into Data
Centers to provide Virtual Private Cloud (VPC) services, as well as
to support virtual network functions, including IP VPN PE functions
outside of Data Centers. Scale and efficiency are crucial factors in
the cloud computing environment supporting various applications and
services, and in traditional service provider space.
The virtual Provider Edge (vPE) solution described in this document
allows for the extension of the PE functionality of BGP/MPLS IP VPN
to end devices, such as servers where the applications reside, or to
the first hop routing/switching device, such as a Top of the Rack
switch (ToR) in a Data Center.
The vPE solutions support both Software Defined Network (SDN)
approach by allowing physical decoupling of the control and the
forwarding plane of a vPE, and distributed routing approaches in the
same fashion as IP VPN is achieved with the physical PEs.
1.1 Terminology
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].
Term Definition
----------- --------------------------------------------------
3GPP 3rd Generation Partnership Project (3GPP)
AS Autonomous System
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ASBR Autonomous System Border Router
BGP Border Gateway Protocol
CE Customer Edge
ED End device: where Guest OS, Host OS/Hypervisor,
applications, VMs, and virtual router may reside
Forwarder L3VPN forwarding function
GRE Generic Routing Encapsulation
Hypervisor Virtual Machine Manager
I2RS Interface to Routing Systems
IaaS Infrastructure as a Service
LDP Label Distribution Protocol
LTE Long Term Evolution
MP-BGP Multi-Protocol Border Gateway Protocol
PCEF Policy Charging and Enforcement Function
P Provider backbone router
QoS Quality of Service
RR Route Reflector
RT Route Target
RTC RT Constraint
SDN Software Defined Network
ToR Top-of-Rack switch
VI Virtual Interface
vCE virtual Customer Edge Router
VM Virtual Machine
vPC virtual Private Cloud
vPE virtual Provider Edge Router
vPE-C virtual Provider Edge Control plane
vPE-F virtual Provider Edge Forwarder
VPN Virtual Private Network
vRR virtual Route Reflector1.2 Scope of the document
WAN Wide Area Network
1.2 Motivation and requirements
The recent rapid adoption of Cloud Services by Enterprises and the
phenomenal growth of mobile IP applications accelerate the need to
extend the BGP IP VPN capability into cloud service end devices. For
examples, Enterprise customers' want to extend the existing IP VPN
services in the WAN into the new cloud services supported by various
Data Center (DC) technologies; Large Enterprises have existing L3VPN
deployments and are extending them into their Data Centers; Mobile
providers adopting IP VPN into their 3GPP mobile infrastructure are
looking to extend the IP VPNs to their end devices of the call
processing center. In addition, vPE is one of the earlier work as
part of Network Function Virtualization (NfV) effort, where IP VPN PE
function is one of the network functions subject to virtualization.
In general, the vPE solutions can be used in cloud service
development or any other environment with or without the inter-
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connection to existing Enterprise BGP IP VPNs.
Key requirements for vPE solutions:
1) MUST support end device multi-tenancy, per tenant routing
isolation and traffic separation.
2) MUST support large scale IP VPNs in the Data Center, upto tens of
thousands of end devices and millions of VMs in the single Data
Center.
3) MUST support end-to-end IP VPN connectivity, e.g. IP VPN can start
from a Data Center end device, connect to a corresponding IP VPN in
the WAN, and terminate in another Data Center end device.
4) MUST allow physical decoupling of IP VPN PE control plane and
forwarding for network virtualization and abstraction.
5) MUST provide support of the control plane through a SDN controller
(centralized or distributed), as well as through the traditional
distributed MP-BGP approach.
6) MUST support VM mobility
7) MUST support orchestration/provisioning as a key deployment model
8) SHOULD be capable to support service chaining as part of the
solution [I-D.rfernando-l3vpn-service-chaining], [I-D.bitar-i2rs-
service-chaining].
The architecture and protocols defined in BGP/MPLS IP VPN [RFC4364]
provide the foundation for virtual PE extension. Certain protocol
extensions may be needed to support the virtual PE solutions.
2. Virtual PE Architecture
2.1 Virtual PE definitions
As defined in [RFC4364], an IP VPN is created by applying policies to
form a subset of sites among all sites connected to the backbone
network. It is a collection of "sites". A site can be considered as
a set of IP systems maintaining IP inter-connectivity without direct
connecting through the backbone. The typical use of L3VPM has been to
inter-connect different sites of an Enterprise networks through a
Service Provider's BGP IP VPNs in the WAN.
A virtual PE (vPE) is a BGP IP VPN PE software instance which may
reside in any network or computing devices. The control and
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forwarding components of the vPE can be decoupled, they may reside in
the same physical device, or most often in different physical
devices.
A virtualized Provider Edge Forwarder (vPE-F) is the forwarding
element of a vPE. vPE-F can reside in an end device, such as a server
in a Data Center where multiple application Virtual Machines (VMs)
are supported, or a Top-of-Rack switch (ToR) which is the first hop
switch from the Data Center edge. When a vPE-F is residing in a
server, its connection to a co-resident VM is as the same as the PE-
CE relationship in the regular BGP IP VPNs, but without routing
protocols or static routing between the virtual PE and CE because the
connection is internal to the device.
The vPE Control plane (vPE-C) is the control element of a vPE. When
using the approach where control plane is decoupled from the physical
topology, the vPE-F may be in a server and co-resident with
application VMs, while one vPE-C can be in a separate device, such as
an SDN Controller where control plane elements and orchestration
functions are located. Alternatively, the vPE-C can reside in the
same physical device as the vPE-F. In this case, it is similar to the
traditional implementation of VPN PEs where, distributed MP-BGP is
used for IP VPN information exchange, though the vPE is not a
dedicated physical entity as it is in a physical PE implementation.
2.2 vPE Architecture and Design options
2.2.1 vPE-F host location
Option 1a. vPE-F is on an end device as co-resident with application
VMs. For example, the vPE-F is on a server in a Data Center.
Option 1b. vPE-F forwarder is on a ToR or other first hop devices in
a Data Center, not as co-resident with the application VMs.
Option 1c. vPE-F is located on any network or compute devices in any
type of networks.
2.2.2 vPE control plane topology
Option 2a. vPE control plane is physically decoupled from the vPE-F.
The control plane may be located in a controller in a separate device
(a stand alone device or can be in the gateway as well) from the vPE
forwarding plane.
Option 2b. vPE control plane is supported through dynamic routing
protocols and located in the same physical device as the vPE-F.
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2.2.3 Data Center orchestration models
Option 3a. Push model: It is a top down approach, push IP VPN
provisioning state from a network management system or other
centrally controlled provisioning system to the IP VPN network
elements.
Option 3b. Pull model: It is a bottom-up approach, pull state
information from network elements to network management/AAA based
upon data plane or control plane activity.
2.3 vPE Architecture reference models
2.3.1 vPE-F in an end-device and vPE-C in the controller
Figure 1 illustrates the reference model for a vPE solution with the
vPE-F in the end device co-resident with applications VMs, while the
vPE-C is physically decoupled and residing on a controller.
The Data Center is connected to the IP/MPLS core via the
Gatways/ASBRs. The IP VPN , e.g. VPN RED, has a single termination
point within the Data Center at one of the VPE-F, and is inter-
connected in the WAN to other member sites which belong to the same
client, and the remote ends of VPN RED can be a PE which has VPN RED
attached to it, or another vPE in a different Data Center.
Note that the Data Center fabric/intermediate underlay devices in the
Data Center do not participate IP VPNs, their function is the same as
P routers in the IP/MPLS back bone and they do not maintain the IP
VPN states, not IP VPN aware.
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,-----.
( ')
.--(. '.---.
( ' ' )
( IP/MPLS WAN )
(. .)
( ( .)
WAN ''--' '-''---'
----------------|----------|------------------------
Service/DC | |
Network +-------+ +-------+
|Gateway|---|Gateway| *
| /ASBR | | /ASBR | *
+-------+ +-------+ *
| | +-------------+
| ,---. | |Controller |
.---. ( '.---. |(vPE-C and |
( ' ' ') |orchestrator)|
( Data Center ) +-------------+
(. Fabric ) *
( ( ).--' *
/ ''--' '-''--' \ *
/ / \ \ *
+-------+ +-------+ +-------+ +-------+
| vPE-F | | vPE-F | | vPE-F | | vPE-F |
+---+---+ +---+---+ +---+---+ +---+---+
|VM |VM | |VM |VM | |VM |VM | |VM |VM |
+---+---+ +---+---+ +---+---+ +---+---+
|VM |VM | |VM |VM | |VM |VM | |VM |VM |
+---+---+ +---+---+ +---+---+ +---+---+
End Device End Device End Device End Device
Figure 1. Virtualized Data Center with vPE at
the end device and vPE-C and vPE-F physically decoupled
Note:
a) *** represents Controller logical connections to the all
Gateway/ASBRs and to all vPE-F.
b) ToR is assumed included in the Data Center cloud.
2.3.2 vPE-F and vPE-C on the same end-device
In this option, vPE-F and vPE-C functionality are both resident in
the end-device. The vPE functions the same as it is in a physical PE.
MP-BGP is used for the VPN control plane. Virtual or physical Route
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Reflectors (RR) (not shown in the diagram) can be used to assist
scaling.
,-----.
( ')
.--(. '.---.
( ' ' )
( IP/MPLS WAN )
(. .)
( ( .)
WAN ''--' '-''---'
----------------|----------|----------------------
Service/DC | |
Network +-------+ +-------+
|Gateway|---|Gateway|
| /ASBR | | /ASBR | *
+-------+ +-------+ *
| | * MP-BGP
| ,---. | *
.---. ( '.---. *
( ' ' ') *
( Data Center ) *
(. Fabric ) *
( ( ).--' *
/ ''--' '-''--' \ *
/ / \ \ *
+-------+ +-------+ +-------+ +-------+
| vPE | | vPE | | vPE | | vPE |
+---+---+ +---+---+ +---+---+ +---+---+
|VM |VM | |VM |VM | |VM |VM | |VM |VM |
+---+---+ +---+---+ +---+---+ +---+---+
|VM |VM | |VM |VM | |VM |VM | |VM |VM |
+---+---+ +---+---+ +---+---+ +---+---+
End Device End Device End Device End Device
Figure 2. Virtualized Data Center with vPE at
the end device, VPN control signal uses MP-BGP
Note:
a) *** represents the logical connections using MP-BGP among the
Gateway/ASBRs and to the vPEs on the end devices.
b) ToR is assumed included in the Data Center cloud.
2.3.3 vPE-F and vPE-C are on the ToR
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In this option, vPE functionality is the same as a physical PE. MP-
BGP is used for the VPN control plane. Virtual or physical Route
Reflector (RR) (not shown in the diagram) can be used to assist
scaling.
,-----.
( ')
.--(. '.---.
( ' ' )
( IP/MPLS WAN )
(. .)
( ( .)
WAN ''--' '-''---'
----------------|----------|----------------------
Service/DC | |
Network +-------+ +-------+
|Gateway|---|Gateway|
| /ASBR | | /ASBR | *
+-------+ +-------+ *
| | * MP-BGP
| ,---. | *
.---. ( '.---. *
( ' ' ') *
( Data Center ) *
(. Fabric ) *
( ( ).--' *
/''--' '-/'--' \ *
+---+---+ +---+---+ +---+---+
|vPE| | |vPE| | |vPE| |
+---+ | +---+ | +---+ |
| ToR | | ToR | | ToR |
+-------+ +-------+ +-------+
/ \ / \ / \
+-------+ +-------+ +-------+ +-------+
| vPE | | vPE | | vPE | | vPE |
+---+---+ +---+---+ +---+---+ +---+---+
|VM |VM | |VM |VM | |VM |VM | |VM |VM |
+---+---+ +---+---+ +---+---+ +---+---+
|VM |VM | |VM |VM | |VM |VM | |VM |VM |
+---+---+ +---+---+ +---+---+ +---+---+
End Device End Device End Device End Device
Figure 3. Virtualized Data Center with vPE at
the ToP, VPN control signal uses MP-BGP
Note: *** represents the logical connections using MP-BGP among the
Gateway/ASBRs and to the vPEs on the ToRs.
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2.3.4 vPE-F on the ToR and vPE-C on the controller
In this option, the L3VPN termination is at the ToR, but the control
plane decoupled from the data plane and resided in a controller,
which can be on a stand alone device, or can be placed at the
Gateway/ASBR.
2.3.5 Server view of vPE
An end device shown in Figure 4 is a virtualized server that hosts
multiple VMs. The virtual PE is co-resident in the server. The vPE
supports multiple VRFs, VRF Red, VRF Grn, VRF Yel, VRF Blu, etc. Each
application VM is associated to a particular VRF as a member of the
particular VPN. For example, VM1 is associated to VRF Red, VM2 and
VM47 are associated to VRF Grn, etc. Routing isolation applies
between VPNs for multi-tenancy support. For example, VM1 and VM2
cannot communicate directly in a simple intranet L3VPN topology as
shown in the configuration.
The vPE connectivity relationship between vPE and the application VM
is similar to the PE-to-CE relationship in a regular BGP IP VPNs.
However, as the vPE and CE functions are co-resident in the same
server, the connection between them is an internal implementation of
the server.
+----------------------------------------------------+
| +---------+ +---------+ +---------+ +---------+ |
| | VM1 | | VM2 | | VM47 | | VM48 | |
| |(VPN Red)| |(VPN Grn)|... |(VPN Grn)| |(VPN Blu)| |
| +----+----+ +---+-----+ +----+----+ +----+----+ |
| | | | | |
| +---+ | +-------------+ +---+ |
| | | | | |
to | +---+------+-+---------------------+---+ |
Gateway| | | | | | | |
PE | | +-+-+ ++-++ +---+ +-+-+ | |
| | |VRF| |VRF| ....... |VRF| |VRF| | |
<------+------+ |Red| |Grn| |Yel| |Blu| | |
| | +---+ +---+ +---+ +---+ | |
| | L3 VPN virtual PE | |
| +--------------------------------------+ |
| |
| End Device |
+----------------------------------------------------+
Figure 4. Server View of vPE to VM relationship
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An application VM may send packets to a vPE forwarder that need to be
bridged, either locally to another VM, or to a remote destination. In
this case, the vPE contains a virtual bridge instance to which the
application VMs (CEs) are attached.
+----------------------------------------------------+
| +---------+ +---------+ +---------+ |
| | VM1 | | VM2 | | VM47 | |
| |(VPN Red)| |(VPN Grn)|... |(VPN Grn)| |
| +----+----+ +---+-----+ +----+----+ |
| | | | |
| +---+ +-----+ +-----+ |
| | | | | |
to | +---+------+-----+---+-----------------+ |
Gateway| | | | | | | |
PE | | +-+-----+ ++-++++++ | |
| | |VBridge| |VBridge| ....... | |
<------+------+ |Red | |Grn | | |
| | +-------+ +-------+ | |
| | vPE | |
| +--------------------------------------+ |
| |
| End Device |
+----------------------------------------------------+
Figure 4. Bridging Service at vPE
3. Control Plane
3.1 vPE Control Plane (vPE-C)
The vPE control plane functionality MAY use a SDN controller or be
distributed using MP-BGP.
3.1.1 SDN approach
This approach is appropriate when the vPE control and data planes are
physically decoupled. The control plane directing the data flow may
reside elsewhere, such a SDN controller. This approach requires a
standard interface to the routing system. The Interface to Routing
System (I2RS) is work in progress in IETF as described in [I-D.atlas-
i2rs-architecture], [I-D.rfernando-irs-fw-req].
Although MP-BGP is often the de facto preferred choice between vPE
and gateway-PE/ASBR, the use of extensible signaling messaging
protocols MAY often be more practical in a Data Center environment.
One such proposal that uses this approach is detailed in [I-D.ietf-
l3vpn-end-system].
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3.1.2 Distributed control plane
In the distributed control plane approach, the vPE participates in
the overlay L3VPN control protocol: MP-BGP [RFC4364].
When the vPE function is on a ToR, it participates the underlay
routing through IGP protocols: ISIS or OSPF.
When the vPE function is on a server, it functions as a host attached
to a server.
3.3 Use of router reflector
Modern Data Centers can be very large in scale. For example, the
number of VPNs routes in a very large Data Centers can surpass the
scale of those in a Service Provider backbone VPN network. There may
be tens of thousands of end devices in a single Data Center.
Use of Router Reflector (RR) is necessary in large-scale L3VPN
networks to avoid a full iBGP mesh among all vPEs and PEs. The L3 VPN
routes can be partitioned to a set of RRs, the partitioning
techniques are detailed in [RFC4364].
When the RR is residing in a physical device, e.g., a server, which
is partitioned to support multi-functions and applications VMs, the
RR becomes a virtualized RR (vRR). Since RR's performs control plane
only, a physical or virtualized server with large scale of computing
power and memory can be a good candidate as host of vRRs. The vRR can
also reside be in Gateway PE/ASBR, or in an end device.
3.4 Use of Constrained Route Distribution [RFC4684]
The Constrained Route Distribution [RFC4684] is a powerful tool for
selective L3VPN route distribution. Using this functionality, only
the BGP receivers (e.g, PE/vPE/RR/vRR/ASBRs, etc.) with the
particular L3VPNs attached will receive the route update for the
corresponding VPNs. It is critical to use constrained route
distribution to support large-scale L3VPN developments.
4. Forwarding Plane
4.1 Virtual Interface
A Virtual Interface (VI) is an interface within an end device that is
used for connection of the vPE to the application VMs in the same end
device. Such application VMs are treated as CEs in the regular
L3VPN's view.
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4.2 Virtual Provider Edge Forwarder (vPE-F)
The Virtual Provider Edge Forwarder (vPE-F) is the forwarding
component of a vPE where the tenant identifiers (for example MPLS VPN
labels) are pushed/popped.
The vPE-F location options include:
1) Within the end device where the virtual interface and application
VMs are located.
2) In an external device such as a Top of the Rack switch (ToR) in a
Data Center into which the end device connects.
Multiple factors should be considered for the location of the vPE-F,
including device capabilities, overall solution economics,
QoS/firewall/NAT placement, optimal forwarding, latency and
performance, operational impact, etc. There are design tradeoffs, it
is worth the effort to study the traffic pattern and forwarding
looking trend in your own unique Data Center as part of the exercise.
4.3 Encapsulation
There are two existing standardized encapsulation/forwarding options
tipically used for BGP/MPLS L3VPN.
1. MPLS label stack encoding with Label Distribution Protocol
[LDP], [RFC3032][RFC5036].
2. Encapsulating MPLS packets in IP or Generic Routing
Encapsulation (GRE), [RFC4023], [RFC4797].
3. Other types of encapsulation are possible. For example, VXLAN
[I-D.mahalingam-dutt-dcops-vxlan], NVGRE [I-D.sridharan-
virtualization-nvgre], and other modified version of these or other
existing protocols.
The most common BGP/MPLS L3VPNs deployments in Service Provider
networks use MPLS forwarding. This requires that an MPLS transport,
e.g., Label Switched Protocol (LDP) [RFC5036] to be deployed in the
network. It is proven to scale, and it comes with various security
mechanisms to protect the network against attacks.
However, the Data Center environment is different than the Service
Provider VPN networks or large Enterprise backbones. MPLS deployments
may or may not be feasible or desirable. Two major challenges for
MPLS deployments exist in this new environment: 1) the capabilities
of the end devices and the transport/forwarding devices; 2) the
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workforce skill set.
Encapsulating MPLS in IP or GRE tunnel [RFC4023] may often be more
practical in most Data Center, and computing environments. Note that
when IP encapsulations are used, the associated security
considerations must be analyzed carefully.
In addition, there are new encapsulation proposals for Data Centers
currently as work in progress within IETF, including several UDP
based encapsulations proposals and some TCP based proposal. These
overlay encapsulations can be suitable alternatives for a vPE,
considering the availability and leverage of support in virtual and
physical devices.
4.4 Optimal forwarding
Many large cloud service operators have reported that the traffic
patterns in their Data Centers were dominated by East-West across
subnet traffic (between the end device hosting different applications
in different subnets) rather than North-South traffic (going in/out
of the Data Center and to/from the WAN) or switched traffic within
subnets. This is the primary reason that many new large scale design
has moved away from traditional Layer-2 design to Layer-3, especially
for the overlay networks.
When forwarding the traffic within the same VPN, the vPE SHOULD be
able to provide direct communication among the VMs/application
senders/receivers without the need of going through gateway devices.
If it is on the same end device, the traffic should not need to leave
the same device. If it is on different end device, optimal routing
SHOULD be applied.
When multiple VPNs need to be accessed to the end device virtual
interfaces CAN directly access multiple VPNs via using extranet VPN
techniques without the need of Gateway facilitation. This is done
through the use of BGP L3VPN policy control mechanisms to support
this function. In addition, ECMP is a built in layer-3 mechanism and
it is used for load sharing.
Optimal use of available bandwidth can be achieved by virtue of using
ECMP in the underlay, as long as the encapsulation includes certain
entropy in the header (e.g. VXLAN).
4.5 Routing and Bridging Services
A VPN forwarder (vPE-F) may support both IP forwarding as well as
Layer-2 bridging for traffic from attached end hosts. This traffic
may be between end hosts attached to the same VPN forwarder or to
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different VPN forwarders.
In both cases, forwarding at a VPN forwarder takes place based on the
IP or MAC route entries provisioned by the VPE controller.
When the vPE is providing a Layer-3 service to attached CEs, the VPN
forwarder will have a VPN VRF instance with IP routes installed for
both locally attached end-hosts and ones reachable via other VPN
forwarders. The vPE may perform IP routing for all IP packets in this
mode.
When the vPE provides a Layer-2 service to attached end-hosts, the
VPN forwarder will have an E-VPN instance with appropriate MAC
entries.
The vPE may support an Integrated Routing and Bridging service, in
which case the relevant VPN forwarders will have both MAC and IP
table entries installed, and will appropriately route or switch
incoming packets.
The vPE controller does the necessary provisioning to support various
services, as defined by an user.
5. Addressing
5.1 IPv4 and IPv6 support
IPv4 and IPv6 MUST be supported in the vPE solution.
This may present a challenge for older devices, but may not be an
issue for newer forwarding devices and servers. A server is replaced
much more frequently than a network router/switch and newer equipment
should be capable of IPv6 support.
5.2 Address space separation
The addresses used for the IP VPN overlay in a Data Center, SHOULD be
taken from separate address blocks than the ones used for the
underlay infrastructure of the Data Center. This practice is to
protect the Data Center infrastructure from being attacked if the
attacker gains access to the tenant VPNs.
Similarity, the addresses used for the Data Center, e.g., a Data
Center, SHOULD be separated from the WAN backbone addresses space.
6.0 Inter-connection considerations
The inter-connection considerations in this section are focused on
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intra-DC inter-connections.
There are deployment scenarios where IP VPN may not be supported in
every segment of the networks to provide end-to-end IP VPN
connectivity. An IP VPN vPE may be reachable only via an intermediate
inter-connecting network; interconnection may be needed in these
cases.
When multiple technologies are employed in the overall solution, a
clear demarcation should be preserved at the inter-connecting points.
The problems encountered in one domain should not impact other
domains.
From an IP VPN point of view: An IP VPN vPE that implements [RFC4364]
is a component of the IP VPN network only. An IP VPN VRF on a
physical PE or vPE contains IP routes only, including routes learnt
over the locally attached network.
As described earlier in this document, the IP VPN vPE should ideally
be located as close to the "customer" edge devices. For cases where
this is not possible, simple existing "IP VPN CE connectivity"
mechanisms should be used, such as static, or direct VM attachments
such as described in the vCE [I-D.fang-l3vpn-virtual-ce] option
below.
Consider the following scenarios when BGP MPLS VPN technology is
considered as whole or partial deployment:
Scenario 1: All VPN sites (CEs/VMs) support IP connectivity. The most
suited BGP solution is to use IP VPNs [RFC4364] for all sites with PE
and/or vPE solutions. This is a straightforward case.
Scenario 2: Legacy layer-2 connectivity must be supported in certain
sites/CEs/VMs, and the rest of the sites/CEs/VMs need only 3
connectivity.
One can consider using a combined vPE and vCE [I-D.fang-l3vpn-
virtual-ce] solution to solved the problem. Use of IP VPN for all
sites with IP connectivity, and a physical or virtual CE (vCE, may
reside on the end device) to aggregate the Layer-2 sites which for
example, are in a single container in a Data Center. The CE/vCE can
be considered as inter-connecting points, where the Layer-2 network
is terminated and the corresponding routes for connectivity of the L2
network are inserted into L3VPN VRFs. The Layer-2 aspect is
transparent to the L3VPN in this case.
Reducing operation complicity and maintaining the robustness of the
solution are the primary reasons for the recommendations.
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7. Management, Control, and Orchestration
7.1 Assumptions
The discussion in this section is based on the following set of
assumptions:
- The WAN and the inter-connecting Data Center, MAY be under control
of separate administrative domains
- WAN Gateways/ASBRs/PEs are provisioned by existing WAN provisioning
systems
- If a single Gateway/ASBR/PE connecting to the WAN on one side, and
connecting to the Data Center network on the other side, then this
Gateway/ASBR/PE is the demarcation point between the two networks.
- vPEs and VMs are provisioned by Data Center Orchestration systems.
- Managing IP VPNs in the WAN is not within the scope of this
document except the inter-connection points.
7.2 Management/Orchestration system interfaces
The Management/Orchestration system CAN be used to communicate with
both the Data Center Gateway/ASBR, and the end devices.
The Management/Orchestration system MUST support standard,
programmatic interface for full-duplex, streaming state transfer in
and out of the routing system at the Gateway.
The programmatic interface is currently under definition in IETF
Interface to Routing Systems (I2RS)) initiative. [I-D.atlas-i2rs-
architecture], and [I-D.rfernando-irs-fw-req].
Standard data modeling languages will be defined/identified in I2RS.
YANG - A Data Modeling Language for the Network Configuration
Protocol (NETCONF) [RFC6020] is a promising candidate currently under
investigation.
To support remote access between applications running on an end
device (e.g., a server) and routers in the network (e.g. the DC
Gateway), a standard mechanism is expected to be identified and
defined in I2RS to provide the transfer syntax, as defined by a
protocol, for communication between the application and the
network/routing systems. The protocol(s) SHOULD be lightweight and
familiar by the computing communities. Candidate examples include
ReSTful web services, JSON [RFC4627], NETCONF [RFC6241], XMPP
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[RFC6120], and XML. [I-D.atlas-i2rs-architecture].
7.3 Service VM Management
Service VM Management SHOULD be hypervisor agnostic, e.g. On demand
service VMs turning-up SHOULD be supported.
7.4 Orchestration and IP VPN inter-provisioning
The orchestration system
1) MUST support IP VPN service activation in virtualized Data Center.
2) MUST support automated cross-provisioning accounting correlation
between the WAN IP VPN and Data Center for the same tenant.
3) MUST support automated cross provisioning state correlation
between WAN IP VPN and Data Center for the same tenant
There are two primary approaches for IP VPN provisioning - push and
pull, both CAN be used for provisioning/orchestration.
7.4.1 vPE Push model
Push model: push IP VPN provisioning from management/orchestration
systems to the IP VPN network elements.
This approach supports service activation and it is commonly used in
existing IP VPN Enterprise deployments. When extending existing WAN
IP VPN solutions into the a Data Center, it MUST support off-line
accounting correlation between the WAN IP VPN and the cloud/DC IP VPN
for the tenant. The systems SHOULD be able to bind interface
accounting to particular tenant. It MAY requires offline state
correlation as well, for example, binding of interface state to
tenant.
Provisioning the vPE solution:
1) Provisioning process
a. The WAN provisioning system periodically provides to the DC
orchestration system the VPN tenant and RT context.
b. DC orchestration system configures vPE on a per request basis
2) Auto state correlation
3) Inter-connection options:
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Inter-AS options defined in [RFC4364] may or may not be sufficient
for a given inter-connection scenario. BGP IP VPN inter-connection
with the Data Center is discussed in [I-D.fang-l3vpn-data-center-
interconnect].
This model requires offline accounting correlation
1) Cloud/DC orchestration configures vPE
2) Orchestration initiates WAN IP VPN provisioning; passes
connection IDs (e.g., of VLAN/VXLAN) and tenant context to WAN IP
VPN provisioning systems.
3) WAN IP VPN provisioning system provisions PE VRF and policies
as in typical Enterprise IP VPN provisioning processes.
4) Cloud/DC Orchestration system or WAN IP VPN provisioning system
MUST have the knowledge of the connection topology between the DC
and WAN, including the particular interfaces on core router and
connecting interfaces on the DC PE and/or vPE.
In short, this approach requires off-line accounting correlation
and state correlation, and requires per WAN Service Provider
integration.
Dynamic BGP sessions between PE/vPE and vCE MAY be used to
automate the PE provisioning in the PE-vCE model, that will remove
the needs for PE configuration. Caution: This is only under the
assumption that the DC provisioning system is trusted and can
support dynamic establishment of PE-vCE BGP neighbor
relationships, for example, the WAN network and the cloud/DC
belong to the same Service Provider.
7.4.2 vPE Pull model
Pull model: pull from network elements to network management/AAA
based upon data plane or control plane activity. It supports
service activation. This approach is often used in broadband
deployments. Dynamic accounting correlation and dynamic state
correlation are supported. For example, session based accounting
is implicitly includes tenant context state correlation, as well
as session-based state that implicitly includes tenant context.
Note that the pull model is less common for vPE deployment
solutions.
Provisioning process:
1) Cloud/DC orchestration configures vPE
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2) Orchestration primes WAN IP VPN provisioning/AAA for new
service, passes connection IDs (e.g., VLAN/VXLAN) and tenant
context.
3) Cloud/DC ASBR detects new VLAN and sends Radius Access-Request
(or Diameter Base Protocol request message [RFC6733]).
4) Radius Access-Accept (or Diameter Answer) with VRF and other
policies
Auto accounting correlation and auto state correlation is
supported.
7. Security Considerations
vPE solution presented a virtualized IP VPN PE model. There are
potential implications to IP VPN control plane, forwarding plane,
and management plane. Security considerations are currently under
study, will be included in the future revisions.
8. IANA Considerations
None.
9. References
9.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, January 2001.
[RFC4023] Worster, T., Rekhter, Y., and E. Rosen, Ed.,
"Encapsulating MPLS in IP or Generic Routing Encapsulation
(GRE)", RFC 4023, March 2005.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271, January
2006.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, February 2006.
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[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, November 2006.
[RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
"LDP Specification", RFC 5036, October 2007.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
October 2010.
[RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 6120, March 2011.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, June 2011.
[RFC6733] Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn,
Ed., "Diameter Base Protocol", RFC 6733, October 2012.
[I-D.ietf-l3vpn-end-system] Marques, P., Fang, L., Pan, P., Shukla,
A., Napierala, M., Bitar, N., "BGP-signaled end-system
IP/VPNs", draft-ietf-l3vpn-end-system-01, April, 2013.
9.2 Informative References
[RFC4627] Crockford, D., "The application/json Media Type for
JavaScript Object Notation (JSON)", RFC 4627, July 2006.
[RFC4797] Rekhter, Y., Bonica, R., and E. Rosen, "Use of Provider
Edge to Provider Edge (PE-PE) Generic Routing
Encapsulation (GRE) or IP in BGP/MPLS IP Virtual Private
Networks", RFC 4797, January 2007.
[I-D.fang-l3vpn-end-system-req] Napierala, M., and Fang, L.,
"Requirements for Extending BGP/MPLS VPNs to End-Systems",
draft-fang-l3vpn-end-system-requirements-01, Oct. 2012.
[I-D.atlas-i2rs-architecture] Atlas A., Halpern, J., Hares, S., Ward.
D., Nadeau, T., draft-atlas-i2rs-architecture-01, July
2013.
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[I-D.rfernando-irs-fw-req] Fernando, R., Medved, J., Ward, D., Atlas,
A., Rijsman, B., "IRS Framework Requirements", draft-
rfernando-irs-framework-requirement-00, Oct. 2012.
[I-D.rfernando-l3vpn-service-chaining] Fernando, R., Rao, D., Fang,
L., Napierala, M., So, N., draft-rfernando-l3vpn-service-
chaining-02, July 15, 2013.
[I-D.bitar-i2rs-service-chaining] Bitar, N., Geron, G., Fang, L.,
Krishnan, R., Leymann, N., Shah, H., Chakrabarti, S.,
Haddad, W., draft-bitar-i2rs-service-chaining-00, July
2013.
[I-D.fang-l3vpn-virtual-ce] Fang, L., Evans, J., Ward, D., Fernando,
R., Mullooly, J., So, N., Bitar., N., Napierala, M., "BGP
IP VPN Virtual PE", draft-fang-l3vpn-virtual-ce-01, Feb.
2013.
[I-D.fang-l3vpn-data-center-interconnect] Fang, L., Fernando, R.,
Rao, D., Boutros, S., BGP IP VPN Data Center Interconnect,
draft-fang-l3vpn-data-center-interconnect-01, Feb. 2013.
[I-D.mahalingam-dutt-dcops-vxlan]: Mahalingam, M, Dutt, D.., et al.,
"A Framework for Overlaying Virtualized Layer 2 Networks
over Layer 3 Networks" draft-mahalingam-dutt-dcops-vxlan-
04, May 2013.
[I-D.sridharan-virtualization-nvgre]: SridharanNetwork, M., et al.,
"Virtualization using Generic Routing Encapsulation",
draft-sridharan-virtualization-nvgre-02.txt, July 2012.
Authors' Addresses
Luyuan Fang
Cisco
111 Wood Ave. South
Iselin, NJ 08830
Email: lufang@cisco.com
David Ward
Cisco
170 W Tasman Dr
San Jose, CA 95134
Email: wardd@cisco.com
Rex Fernando
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Cisco
170 W Tasman Dr
San Jose, CA
Email: rex@cisco.com
Maria Napierala
AT&T
200 Laurel Avenue
Middletown, NJ 07748
Email: mnapierala@att.com
Nabil Bitar
Verizon
40 Sylvan Road
Waltham, MA 02145
Email: nabil.bitar@verizon.com
Dhananjaya Rao
Cisco
170 W Tasman Dr
San Jose, CA
Email: dhrao@cisco.com
Bruno Rijsman
Juniper Networks
10 Technology Park Drive
Westford, MA 01886
Email: brijsman@juniper.net
Ning So
Tata Communications
Plano, TX 75082, USA
Email: ning.so@tatacommunications.com
Jim Guichard
Cisco
Boxborough, MA 01719
Email: jguichar@cisco.com
Wen Wang
CenturyLink
2355 Dulles Corner Blvd.
Herndon, VA 20171
Email:Wen.Wang@CenturyLink.com
Manuel Paul
Deutsche Telekom
Winterfeldtstr. 21-27
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10781 Berlin, Germany
Email: manuel.paul@telekom.de
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