Network Working Group L. Yong
Internet Draft L. Dunbar
Category: Informational Huawei
M. Toy
A. Isaac
Juniper Networks
V. Manral
Ionos Networks
Expires: March 2017 September 1, 2016
Use Cases for Data Center Network Virtualization Overlays
draft-ietf-nvo3-use-case-09
Abstract
This document describes Data Center (DC) Network Virtualization over
Layer 3 (NVO3) use cases that can be deployed in various data
centers and serve different applications.
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Table of Contents
1. Introduction...................................................3
1.1. Terminology...............................................4
2. Basic Virtual Networks in a Data Center........................4
3. DC Virtual Network and External Network Interconnection........6
3.1. DC Virtual Network Access via the Internet................6
3.2. DC VN and SP WAN VPN Interconnection......................7
4. DC Applications Using NVO3.....................................8
4.1. Supporting Multiple Technologies..........................9
4.2. DC Application with Multiple Virtual Networks.............9
4.3. Virtualized Data Center (vDC)............................10
5. Summary.......................................................11
6. Security Considerations.......................................12
7. IANA Considerations...........................................12
8. References....................................................12
8.1. Normative References.....................................12
8.2. Informative References...................................12
Contributors.....................................................13
Acknowledgements.................................................14
Authors' Addresses...............................................14
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1. Introduction
Server Virtualization has changed the Information Technology (IT)
industry in terms of the efficiency, cost, and speed of providing
new applications and/or services such as cloud applications. However
traditional Data Center (DC) networks have some limits in supporting
cloud applications and multi tenant networks [RFC7364]. The goal of
Network Virtualization Overlays in the DC is to decouple the
communication among tenant systems from DC physical infrastructure
networks and to allow one physical network infrastructure to provide:
o Multi-tenant virtual networks and traffic isolation among the
virtual networks over the same physical network.
o Independent address spaces in individual virtual networks such as
MAC, IP, TCP/UDP etc.
o Flexible Virtual Machines (VM) and/or workload placement
including the ability to move them from one server to another
without requiring VM address and configuration changes, and the
ability to perform a "hot move" with no disruption to the live
application running on VMs.
These characteristics of NVO3 help address the issues that cloud
applications face in Data Centers [RFC7364].
An NVO3 network may interconnect with another NVO3 virtual network,
or another physical network (i.e., not the physical network that the
NVO3 network is over), via a gateway. The use case examples for the
latter are: 1) DCs that migrate toward an NVO3 solution will be done
in steps, where a portion of tenant systems in a VN is on
virtualized servers while others exist on a LAN. 2) many DC
applications serve to Internet users who are on physical networks; 3)
some applications are CPU bound, such as Big Data analytics, and may
not run on virtualized resources. Some inter-VN policies can be
enforced at the gateway.
This document describes general NVO3 use cases that apply to various
data centers. Three types of the use cases described in this
document are:
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o Basic NVO3 virtual networks in a DC (Section 2). All Tenant
Systems (TS) in the virtual network are located within the same
DC. The individual virtual networks can be either Layer 2 (L2) or
Layer 3 (L3). The number of NVO3 virtual networks in a DC is much
higher than what traditional VLAN based virtual networks [IEEE
802.1Q] can support. This case is often referred as to the DC
East-West traffic.
o Virtual networks that span across multiple Data Centers and/or to
customer premises, i.e., an NVO3 virtual network where some
tenant systems in a DC attach to interconnect another virtual or
physical network outside the data center. An enterprise customer
may use a traditional carrier VPN or an IPsec tunnel over the
Internet to communicate with its systems in the DC. This is
described in Section 3.
o DC applications or services require an advanced network that
contains several NVO3 virtual networks that are interconnected by
the gateways. Three scenarios are described in Section 4: 1)
using NVO3 and other network technologies to build a tenant
network; 2) constructing several virtual networks as a tenant
network; 3) applying NVO3 to a virtualized DC (vDC).
The document uses the architecture reference model defined in
[RFC7365] to describe the use cases.
1.1. Terminology
This document uses the terminologies defined in [RFC7365] and
[RFC4364]. Some additional terms used in the document are listed
here.
DMZ: Demilitarized Zone. A computer or small sub-network that sits
between a trusted internal network, such as a corporate private LAN,
and an un-trusted external network, such as the public Internet.
DNS: Domain Name Service [RFC1035]
NAT: Network Address Translation [RFC1631]
Note that a virtual network in this document refers to an NVO3
virtual network in a DC [RFC7365].
2. Basic Virtual Networks in a Data Center
A virtual network in a DC enables communications among Tenant
Systems (TS). A TS can be a physical server/device or a virtual
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machine (VM) on a server, i.e., end-device [RFC7365]. A Network
Virtual Edge (NVE) can be co-located with a TS, i.e., on the same
end-device, or reside on a different device, e.g., a top of rack
switch (ToR). A virtual network has a virtual network identifier
(can be globally unique or locally significant at NVEs).
Tenant Systems attached to the same NVE may belong to the same or
different virtual networks. An NVE provides tenant traffic
forwarding/encapsulation and obtains tenant systems reachability
information from a Network Virtualization Authority (NVA)[NVO3ARCH].
DC operators can construct multiple separate virtual networks, and
provide each with own address space.
Network Virtualization Overlay in this context means that a virtual
network is implemented with an overlay technology, i.e., within a DC
that has IP infrastructure, tenant traffic is encapsulated at its
local NVE and carried by a tunnel to another NVE where the packet is
decapsulated and sent to a target tenant system. This architecture
decouples tenant system address space and configuration from the
infrastructure's, which provides great flexibility for VM placement
and mobility. It also means that the transit nodes in the
infrastructure are not aware of the existence of the virtual
networks and tenant systems attached to the virtual networks. The
tunneled packets are carried as regular IP packets and are sent to
NVEs. One tunnel may carry the traffic belonging to multiple virtual
networks; a virtual network identifier is used for traffic
demultiplexing. A tunnel encapsulation protocol is necessary for NVE
to encapsulate the packets from Tenant Systems and encode other
information on the tunneled packets to support NVO3 implementation.
A virtual network implemented by NVO3 may be an L2 or L3 domain. The
virtual network can carry unicast traffic and/or multicast,
broadcast/unknown (for L2 only) traffic from/to tenant systems.
There are several ways to transport virtual network BUM traffic
[NVO3MCAST].
It is worth mentioning two distinct cases regarding to NVE location.
The first is where TSs and an NVE are co-located on a single end
host/device, which means that the NVE can be aware of the TS's state
at any time via an internal API. The second is where TSs and an NVE
are not co-located, with the NVE residing on a network device; in
this case, a protocol is necessary to allow the NVE to be aware of
the TS's state [NVO3HYVR2NVE].
One virtual network can provide connectivity to many TSs that attach
to many different NVEs in a DC. TS dynamic placement and mobility
results in frequent changes of the binding between a TS and an NVE.
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The TS reachability update mechanisms need be fast enough so that
the updates do not cause any communication disruption/interruption.
The capability of supporting many TSs in a virtual network and many
more virtual networks in a DC is critical for the NVO3 solution.
If a virtual network spans across multiple DC sites, one design is
to allow the network to seamlessly span across the sites without DC
gateway routers' termination. In this case, the tunnel between a
pair of NVEs can be carried within other intermediate tunnels over
the Internet or other WANs, or the intra DC and inter DC tunnels can
be stitched together to form a tunnel between the pair of NVEs that
are in different DC sites. Both cases will form one virtual network
across multiple DC sites.
3. DC Virtual Network and External Network Interconnection
Many customers (an enterprise or individuals) who utilize a DC
provider's compute and storage resources to run their applications
need to access their systems hosted in a DC through Internet or
Service Providers' Wide Area Networks (WAN). A DC provider can
construct a virtual network that provides connectivity to all the
resources designated for a customer and allows the customer to
access the resources via a virtual gateway (vGW). This, in turn,
becomes the case of interconnecting a DC virtual network and the
network at customer site(s) via the Internet or WANs. Two use cases
are described here.
3.1. DC Virtual Network Access via the Internet
A customer can connect to a DC virtual network via the Internet in a
secure way. Figure 1 illustrates this case. The DC virtual network
has an instance at NVE1 and NVE2 and the two NVEs are connected via
an IP tunnel in the Data Center. A set of tenant systems are
attached to NVE1 on a server. NVE2 resides on a DC Gateway device.
NVE2 terminates the tunnel and uses the VNID on the packet to pass
the packet to the corresponding vGW entity on the DC GW (the vGW is
the default gateway for the virtual network). A customer can access
their systems, i.e., TS1 or TSn, in the DC via the Internet by using
an IPsec tunnel [RFC4301]. The IPsec tunnel is configured between
the vGW and the customer gateway at the customer site. Either a
static route or iBGP may be used for prefix advertisement. The vGW
provides IPsec functionality such as authentication scheme and
encryption; iBGP protocol traffic is carried within the IPsec tunnel.
Some vGW features are listed below:
o The vGW maintains the TS/NVE mappings and advertises the TS
prefix to the customer via static route or iBGP.
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o Some vGW functions such as firewall and load balancer can be
performed by locally attached network appliance devices.
o If the virtual network in the DC uses different address space
than external users, then the vGW needs to provide the NAT
function.
o More than one IPsec tunnel can be configured for redundancy.
o The vGW can be implemented on a server or VM. In this case, IP
tunnels or IPsec tunnels can be used over the DC infrastructure.
o DC operators need to construct a vGW for each customer.
Server+---------------+
| TS1 TSn |
| |...| |
| +-+---+-+ | Customer Site
| | NVE1 | | +-----+
| +---+---+ | | CGW |
+------+--------+ +--+--+
| *
L3 Tunnel *
| *
DC GW +------+---------+ .--. .--.
| +---+---+ | ( '* '.--.
| | NVE2 | | .-.' * )
| +---+---+ | ( * Internet )
| +---+---+. | ( * /
| | vGW | * * * * * * * * '-' '-'
| +-------+ | | IPsec \../ \.--/'
| +--------+ | Tunnel
+----------------+
DC Provider Site
Figure 1 - DC Virtual Network Access via the Internet
3.2. DC VN and SP WAN VPN Interconnection
In this case, an Enterprise customer wants to use a Service Provider
(SP) WAN VPN [RFC4364] [RFC7432] to interconnect its sites with a
virtual network in a DC site. The Service Provider constructs a VPN
for the enterprise customer. Each enterprise site peers with an SP
PE. The DC Provider and VPN Service Provider can build a DC virtual
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network (VN) and VPN independently, and then interconnect them via a
local link, or a tunnel between the DC GW and WAN PE devices. The
control plane interconnection options between the DC and WAN are
described in RFC4364 [RFC4364]. Using Option A with VRF-LITE [VRF-
LITE], both ASBRs, i.e., DC GW and SP PE, maintain a
routing/forwarding table (VRF). Using Option B, the DC ASBR and SP
ASBR do not maintain the VRF table; they only maintain the VN and
VPN identifier mappings, i.e., label mapping, and swap the label on
the packets in the forwarding process. Both option A and B allow VN
and VPN using own identifier and two identifiers are mapped at DC GW.
With option C, the VN and VPN use the same identifier and both ASBRs
perform the tunnel stitching, i.e., tunnel segment mapping. Each
option has pros/cons [RFC4364] and has been deployed in SP networks
depending on the applications in use. BGP is used with these options
for route distribution between DCs and SP WANs. Note that if the DC
is the SP's Data Center, the DC GW and SP PE in this case can be
merged into one device that performs the interworking of the VN and
VPN within an AS.
The configurations above allow the enterprise networks to
communicate with the tenant systems attached to the VN in a DC
without interfering with the DC provider's underlying physical
networks and other virtual networks. The enterprise can use its own
address space in the VN. The DC provider can manage which VM and
storage elements attach to the VN. The enterprise customer manages
which applications run on the VMs in the VN without knowing the
location of the VMs in the DC. (See Section 4 for more)
Furthermore, in this use case, the DC operator can move the VMs
assigned to the enterprise from one sever to another in the DC
without the enterprise customer being aware, i.e., with no impact on
the enterprise's 'live' applications. Such advanced technologies
bring DC providers great benefits in offering cloud services, but
add some requirements for NVO3 [RFC7364] as well.
4. DC Applications Using NVO3
NVO3 technology provides DC operators with the flexibility in
designing and deploying different applications in an end-to-end
virtualization overlay environment. Operators no longer need to
worry about the constraints of the DC physical network configuration
when creating VMs and configuring a virtual network. A DC provider
may use NVO3 in various ways, in conjunction with other physical
networks and/or virtual networks in the DC for a reason. This
section highlights some use cases for this goal.
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4.1. Supporting Multiple Technologies
Servers deployed in a large data center are often installed at
different times, and may have different capabilities/features. Some
servers may be virtualized, while others may not; some may be
equipped with virtual switches, while others may not. For the
servers equipped with Hypervisor-based virtual switches, some may
support VxLAN [RFC7348] encapsulation, some may support NVGRE
encapsulation [RFC7637], and some may not support any encapsulation.
To construct a tenant network among these servers and the ToR
switches, operators can construct one traditional VLAN network and
two virtual networks where one uses VxLAN encapsulation and the
other uses NVGRE, and interconnect these three networks via a
gateway or virtual GW. The GW performs packet
encapsulation/decapsulation translation between the networks.
Another case is that some software of a tenant is high CPU and
memory consumption, which only makes a sense to run on metal servers;
other software of the tenant may be good to run on VMs. However
provider DC infrastructure is configured to use NVO3 to connect to
VMs and VLAN [IEEE802.1Q] connect to metal services. The tenant
network requires interworking between NVO3 and traditional VLAN.
4.2. DC Application with Multiple Virtual Networks
A DC application may necessarily be constructed with multi-tier
zones, where each zone has different access permissions and runs
different applications. For example, a three-tier zone design has a
front zone (Web tier) with Web applications, a mid zone (application
tier) where service applications such as credit payment or ticket
booking run, and a back zone (database tier) with Data. External
users are only able to communicate with the Web application in the
front zone; the back zone can only receive traffic from the
application zone. In this case, communications between the zones
must pass through a GW/firewall. Each zone can be implemented by one
virtual network and a GW/firewall can be used to between two virtual
networks, i.e., two zones. A tunnel carrying virtual network traffic
has to be terminated at the GW/firewall where overlay traffic is
processed.
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4.3. Virtualized Data Center (vDC)
An Enterprise Data Center today may deploy routers, switches, and
network appliance devices to construct its internal network, DMZ,
and external network access; it may have many servers and storage
running various applications. With NVO3 technology, a DC Provider
can construct a virtualized DC over its physical DC infrastructure
and offer a virtual DC service to enterprise customers. A vDC at the
DC Provider site provides the same capability as the physical DC at
the customer site. A customer manages their own applications running
in their vDC. A DC Provider can further offer different network
service functions to the customer. The network service functions may
include firewall, DNS, load balancer, gateway, etc.
Figure 3 below illustrates one such scenario. For simplicity, it
only shows the L3 VN or L2 VN in abstraction. In this example, the
DC Provider operators create several L2 VNs (L2VNx, L2VNy, L2VNz) to
group the tenant systems together on a per-application basis, and
one L3 VN (L3VNa) for the internal routing. A network firewall and
gateway runs on a VM or server that connects to L3VNa and is used
for inbound and outbound traffic processing. A load balancer (LB) is
used in L2VNx. A VPN is also built between the gateway and
enterprise router. The Enterprise customer runs Web/Mail/Voice
applications on VMs at the provider DC site which may be spread
across many servers. The users at the Enterprise site access the
applications running in the provider DC site via the VPN; Internet
users access these applications via the gateway/firewall at the
provider DC.
The Enterprise customer decides which applications should be
accessible only via the intranet and which should be assessable via
both the intranet and Internet, and configures the proper security
policy and gateway function at the firewall/gateway. Furthermore, an
enterprise customer may want multi-zones in a vDC (See section 4.1)
for the security and/or the ability to set different QoS levels for
the different applications.
The vDC use case requires the NVO3 solution to provide DC operators
with an easy and quick way to create a VN and NVEs for any vDC
design, to allocate TSs and assign TSs to the corresponding VN, and
to illustrate vDC topology and manage/configure individual elements
in the vDC in a secure way.
Internet ^ Internet
|
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^ +--+---+
| | GW |
| +--+---+
| |
+-------+--------+ +--+---+
|Firewall/Gateway+--- VPN-----+router|
+-------+--------+ +-+--+-+
| | |
...+.... |..|
+-------: L3 VNa :---------+ LANs
+-+-+ ........ |
|LB | | | Enterprise Site
+-+-+ | |
...+... ...+... ...+...
: L2VNx : : L2VNy : : L2VNz :
....... ....... .......
|..| |..| |..|
| | | | | |
Web App. Mail App. VoIP App.
Provider DC Site
Figure 2 - Virtual Data Center (vDC)
5. Summary
This document describes some general and potential NVO3 use cases in
DCs. The combination of these cases will give operators the
flexibility and capability to design more sophisticated cases for
various cloud applications.
DC services may vary, from infrastructure as a service (IaaS), to
platform as a service (PaaS), to software as a service (SaaS).
In these services, NVO3 virtual networks are just a portion of such
services.
NVO3 uses tunnel techniques to deliver VN traffic over an IP network.
A tunnel encapsulation protocol is necessary. An NVO3 tunnel may in
turn be tunneled over other intermediate tunnels over the Internet
or other WANs.
An NVO3 virtual network in a DC may be accessed by external users in
a secure way. Many existing technologies can help achieve this.
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NVO3 implementations may vary. Some DC operators prefer to use a
centralized controller to manage tenant system reachability in a
virtual network, while other operators prefer to use distribution
protocols to advertise the tenant system location, i.e., NVE
location. When a tenant network spans across multiple DCs and WANs,
each network administration domain may use different methods to
distribute the tenant system locations. Both control plane and data
plane interworking are necessary.
6. Security Considerations
Security is a concern. DC operators need to provide a tenant with a
secured virtual network, which means one tenant's traffic is
isolated from other tenants' traffic as well as from underlay
networks. DC operators also need to prevent against a tenant
application attacking their underlay DC network; further, they need
to protect against a tenant application attacking another tenant
application via the DC infrastructure network. For example, a tenant
application attempts to generate a large volume of traffic to
overload the DC's underlying network. An NVO3 solution has to
address these issues.
7. IANA Considerations
This document does not request any action from IANA.
8. References
8.1. Normative References
[RFC7364] Narten, T., et al "Problem Statement: Overlays for Network
Virtualization", RFC7364, October 2014.
[RFC7365] Lasserre, M., Motin, T., and et al, "Framework for DC
Network Virtualization", RFC7365, October 2014.
8.2. Informative References
[IEEE 802.1Q] IEEE, "IEEE Standard for Local and metropolitan area
networks -- Media Access Control (MAC) Bridges and Virtual
Bridged Local Area", IEEE Std 802.1Q, 2011.
[NVO3HYVR2NVE] Li, Y., et al, "Hypervisor to NVE Control Plane
Requirements", draft-ietf-nvo3-hpvr2nve-cp-req-01, work in
progress.
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[NVO3ARCH] Black, D., et al, "An Architecture for Overlay Networks
(NVO3)", draft-ietf-nvo3-arch-02, work in progress.
[NVO3MCAST] Ghanwani, A., "Framework of Supporting Applications
Specific Multicast in NVO3", draft-ghanwani-nvo3-app-
mcast-framework-02, work in progress.
[RFC1035] Mockapetris, P., "DOMAIN NAMES - Implementation and
Specification", RFC1035, November 1987.
[RFC1631] Egevang, K., Francis, P., "The IP network Address
Translator (NAT)", RFC1631, May 1994.
[RFC4301] Kent, S., "Security Architecture for the Internet
Protocol", rfc4301, December 2005
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, February 2006.
[RFC7348] Mahalingam,M., Dutt, D., ific Multicast in etc "VXLAN: A
Framework for Overlaying Virtualized Layer 2 Networks over
Layer 3 Networks", RFC7348 August 2014.
[RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A. and
J. Uttaro, "BGP MPLS Based Ethernet VPN", RFC7432,
February 2015
[RFC7637] Garg, P., and Wang, Y., "NVGRE: Network Virtualization
using Generic Routing Encapsulation", RFC7637, Sept. 2015.
[VRF-LITE] Cisco, "Configuring VRF-lite", http://www.cisco.com
Contributors
Vinay Bannai
PayPal
2211 N. First St,
San Jose, CA 95131
Phone: +1-408-967-7784
Email: vbannai@paypal.com
Ram Krishnan
Brocade Communications
San Jose, CA 95134
Phone: +1-408-406-7890
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Email: ramk@brocade.com
Kieran Milne
Juniper Networks
1133 Innovation Way
Sunnyvale, CA 94089
Phone: +1-408-745-2000
Email: kmilne@juniper.net
Acknowledgements
Authors like to thank Sue Hares, Young Lee, David Black, Pedro
Marques, Mike McBride, David McDysan, Randy Bush, Uma Chunduri, Eric
Gray, David Allan, and Joe Touch for the review, comments, and
suggestions.
Authors' Addresses
Lucy Yong
Huawei Technologies
Phone: +1-918-808-1918
Email: lucy.yong@huawei.com
Linda Dunbar
Huawei Technologies,
5340 Legacy Dr.
Plano, TX 75025 US
Phone: +1-469-277-5840
Email: linda.dunbar@huawei.com
Mehmet Toy
Phone : +1-856-792-2801
E-mail : mtoy054@yahoo.com
Aldrin Isaac
Juniper Networks
E-mail: aldrin.isaac@gmail.com
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Vishwas Manral
Email: vishwas@ionosnetworks.com
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