Network Working Group L. Yong
Internet Draft L. Dunbar
Category: Informational Huawei
M. Toy
A. Isaac
Juniper Networks
V. Manral
Ionos Networks
Expires: April 2017 October 3, 2016
Use Cases for Data Center Network Virtualization Overlay Networks
draft-ietf-nvo3-use-case-12
Abstract
This document describes data center network virtualization over
layer (NVO3) network use cases that can be deployed in various data
centers and serve different data center applications.
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Table of Contents
1. Introduction...................................................3
1.1. Terminology...............................................4
2. Basic NVO3 Networks............................................5
3. DC NVO3 Network and External Network Interconnection...........6
3.1. DC NVO3 Network Access via the Internet...................6
3.2. DC NVO3 Network and SP WAN VPN Interconnection............8
4. DC Applications Using NVO3.....................................8
4.1. Supporting Multiple Technologies..........................9
4.2. DC Application with Multiple Virtual Networks.............9
4.3. Virtual Data Center (vDC)................................10
5. Summary.......................................................12
6. Security Considerations.......................................12
7. IANA Considerations...........................................12
8. References....................................................13
8.1. Normative References.....................................13
8.2. Informative References...................................13
Contributors.....................................................14
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
data center network virtualization overlay (NVO3) networks is to
decouple the communication among tenant systems from DC physical
infrastructure networks and to allow one physical network
infrastructure:
o Carry many NVO3 networks and isolate different NVO3 network
traffic on a physical network that carries NVO3 network traffic.
o Independent address spaces in individual NVO3 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 changes and physical infrastructure
network configuration changes, and the ability to perform a "hot
move" with no disruption to the live application running on VMs.
These characteristics of NVO3 networks help address the issues that
cloud applications face in data centers [RFC7364].
An NVO3 network may interconnect with another NVO3 network on the
same physical network, or another physical network (i.e., not the
physical network that the NVO3 network is carried 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 network use cases that apply to
various data centers. The use cases described here represent DC
provider's interests and vision for their cloud services. The
document groups the use cases into three categories from simple to
advance in term of implementation. However the implementations of
these use cases are outside the scope of this document. These three
categories are highlighted below:
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o Basic NVO3 networks (Section 2). All Tenant Systems (TS) in the
network are located within the same DC. The individual networks
can be either Layer 2 (L2) or Layer 3 (L3). The number of NVO3
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 A virtual network that spans across multiple Data Centers and/or
to customer premises where NVO3 networks are constructed and
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 networks that are interconnected by the
gateways. Three scenarios are described in Section 4: 1)
supporting multiple technologies; 2) constructing several virtual
networks as a tenant network; 3) applying NVO3 to a virtual Data
Center (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]
DC Operator: A role who is responsible to construct and manage cloud
service instances in their life-cycle and manage DC infrastructure
that runs these cloud instances.
DC Provider: A company that uses its DC infrastructure to offer
cloud services to its customers.
NAT: Network Address Translation [RFC3022]
vGW: virtual Gateway; a gateway component used for an NVO3 virtual
network to interconnect with another virtual/physical network.
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2. Basic NVO3 Networks
An NVO3 network provides communications among Tenant Systems (TS) in
a DC. A TS can be a physical server/device or a virtual machine (VM)
on a server, i.e., end-device [RFC7365]. A DC provider often uses
NVO3 networks for its internal applications in which each
application runs on many VMs or physical services and requires
application segregation.
A Network Virtual Edge (NVE) is an NVO3 architecture component
[RFC7365]]. It is responsible to forward and encapsulate the NVO3
traffic in outbound direction; and decapsulate and forward the NVO3
traffic in inbound direction [NVO3ARCH]. A Network Virtualization
Authority (NVA) is another NVO3 architecture component [RFC7365]. An
NVE obtains the reachability information of tenant systems in a NVO3
network from the NVA. The tenant systems attached to the same NVE
may belong to a same or different NVO3 networks.
The network virtualization overlay in this context means that a
virtual network is implemented with an overlay technology, i.e.,
within a DC, NVO3 traffic is encapsulated at an NVE and carried by a
tunnel to another NVE where the packet is decapsulated and sent to a
target tenant system [NVO3ARCH]. This architecture decouples a NVO3
network construction from the DC physical network configuration,
which provides the flexibility for VM placement and mobility. It
also means that the nodes in the infrastructure network (except
tunnel end point nodes) carry encapsulated NVO3 traffic but not
aware of the existence of NVO3 networks. In the architecture
[NVO3ARCH], one tunnel can carry NVO3 traffic belonging to different
NVO3 networks; a virtual network identifier is used in an NVO3
encapsulation protocol to differentiate NVO3 traffic.
An NVO3 network may be an L2 or L3 domain. The network provides
switching (L2) or routing (L3) capability to support host (i.e.
tenent systems) communications. An NVO3 network may required to
carry unicast traffic and/or multicast, broadcast/unknown (for L2
only) traffic from/to tenant systems. There are several ways to
transport NVO3 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].
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One NVO3 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.
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
using NVO3 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 an intra DC
tunnel and inter DC tunnel(s) can be stitched together to form an
end-to-end 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 NVO3 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 NVO3 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 an NVO3 network and the virtual
private network (VPN) on the Internet or wide-area networks (WAN).
Note that a VPN is not implemented by NVO3 solution. Two use cases
are described here.
3.1. DC NVO3 Network Access via the Internet
A customer can connect to an NVO3 network via the Internet in a
secure way. Figure 1 illustrates an example of this case. The NVO3
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
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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.
o Some vGW functions such as firewall and load balancer can be
performed by locally attached network appliance devices.
o If the NVO3 network 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
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3.2. DC NVO3 Network 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 an
NVO3 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 an NVO3 network
and a WAN 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 NVO3 network 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 the NVO3 network
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 NVO3 network in
the DC without interfering with the DC provider's underlying
physical networks and other NVO3 networks in the DC. The enterprise
can use its own address space in the NVO3 network. The DC provider
can manage which VM and storage elements attach to the NVO3 network.
The enterprise customer manages which applications run on the VMs
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
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virtualization overlay environment. The operators no longer need to
worry about the constraints of the DC physical network configuration
when creating VMs and configuring a network to connect them. 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.
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
NVO3 network and a GW/firewall can be used to between two NVO3
networks, i.e., two zones. As a result, a tunnel carrying NVO3
network traffic must be terminated at the GW/firewall where the NVO3
traffic is processed.
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4.3. Virtual 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 virtual Data Center (vDC) over its physical DC
infrastructure and offer a virtual Data Center service to enterprise
customers. A vDC at the DC Provider site provides the same
capability as the physical DC at a customer site. A customer manages
its own applications running in its 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.
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Figure 2 below illustrates one such scenario at service abstraction
level. In this example, the vDC contains 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. An Enterprise customer runs
Web/Mail/Voice applications on VMs within the vDC. The users at the
Enterprise site access the applications running in the vDC via the
VPN; Internet users access these applications via the
gateway/firewall at the provider DC site.
Internet ^ Internet
|
^ +--+---+
| | 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 Abstraction View
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
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enterprise customer may want multi-zones in a vDC (See section 4.2)
for the security and/or the ability to set different QoS levels for
the different applications.
The vDC use case requires an NVO3 solution to provide DC operators
with an easy and quick way to create an NVO3 network and NVEs for
any vDC design, to allocate TSs and assign TSs to the corresponding
NVO3 network, and to illustrate vDC topology and manage/configure
individual elements in the vDC in a secure way.
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 networks are just a portion of such services.
NVO3 uses tunnel techniques to deliver NVO3 traffic over DC physical
infrastructure 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 network in a DC may be accessed by external users in a
secure way. Many existing technologies can help achieve this.
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.
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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
[IEEE802.1Q] 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-05, work in
progress.
[NVO3ARCH] Black, D., et al, "An Architecture for Overlay Networks
(NVO3)", draft-ietf-nvo3-arch-08, 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.
[RFC3022] Srisuresh, P. and Egevang, K., "Traditional IP Network
Address Translator (Traditional NAT)", RFC3022, January
2001.
[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
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[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
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, Joe Touch, Olufemi Komolafe, and Matthew Bocci
for the review, comments, and suggestions.
Authors' Addresses
Lucy Yong
Huawei Technologies
Phone: +1-918-808-1918
Email: lucy.yong@huawei.com
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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
Vishwas Manral
Email: vishwas@ionosnetworks.com
Yong, et al. [Page 15]
