wdiff rfc7637.alt-original rfc7637.txt

Network Working Group
Independent Submission P. Garg Garg, Ed.
Internet Draft
Request for Comments: 7637 Y. Wang Wang, Ed.
Intended
Category: Informational Microsoft
Expires: October 12, 2015 April 13,
ISSN: 2070-1721 September 2015

NVGRE: Network Virtualization using Using Generic Routing Encapsulation
draft-sridharan-virtualization-nvgre-08.txt

Abstract

This document describes the usage of the Generic Routing
Encapsulation (GRE) header for Network Virtualization (NVGRE) in
multi-tenant
datacenters. data centers. Network Virtualization decouples virtual
networks and addresses from physical network infrastructure,
providing isolation and concurrency between multiple virtual networks
on the same physical network infrastructure. This document also
introduces a Network Virtualization framework to illustrate the use
cases, but the focus is on specifying the data plane data-plane aspect of NVGRE.

Status of this This Memo

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Table of Contents

1. Introduction...................................................2 Introduction ....................................................2
1.1. Terminology...............................................4 Terminology ................................................4
2. Conventions used Used in this document..............................4 This Document ...............................4
3. NVGRE: Network Virtualization using GRE........................5 Using GRE (NVGRE) ........................4
3.1. NVGRE Endpoint............................................5 Endpoint .............................................5
3.2. NVGRE frame format........................................6 Frame Format .........................................5
3.3. Inner Tag as Defined by IEEE 802.1Q Tag..........................................9 ........................8
3.4. Reserved VSID.............................................9 VSID ..............................................8
4. NVGRE Deployment Consideration................................10 Considerations .................................9
4.1. ECMP Support.............................................10 Support ...............................................9
4.2. Broadcast and Multicast Traffic..........................10 Traffic ............................9
4.3. Unicast Traffic..........................................10 Traffic ............................................9
4.4. IP Fragmentation.........................................11 Fragmentation ..........................................10
4.5. Address/Policy Management & Routing......................11 and Routing .....................10
4.6. Cross-subnet, Cross-premise Communication................11 Cross-Subnet, Cross-Premise Communication .................10
4.7. Internet Connectivity....................................13 Connectivity .....................................12
4.8. Management and Control Planes............................13 Planes .............................12
4.9. NVGRE-Aware Devices......................................13 Devices .......................................12
4.10. Network Scalability with NVGRE..........................14 NVGRE ...........................13
5. Security Considerations.......................................15 Considerations ........................................14
6. IANA Considerations...........................................15
7. References....................................................15
7.1. Normative References.....................................15
7.2. Informative References...................................16
8. Authors and Contributors......................................16
9. Acknowledgments...............................................17 References ...........................................14
Contributors ......................................................16
Authors' Addresses ................................................17

1. Introduction

Conventional data center network designs cater to largely static
workloads and cause fragmentation of network and server capacity
[6][7]. [6]
[7]. There are several issues that limit dynamic allocation and
consolidation of capacity. Layer 2 networks use the Rapid Spanning
Tree Protocol (RSTP) (RSTP), which is designed to eliminate loops by
blocking redundant paths. These eliminated paths translate to wasted
capacity and a highly oversubscribed network. There are alternative
approaches such as TRILL the Transparent Interconnection of Lots of Links
(TRILL) that address this problem [13].

The network utilization inefficiencies are exacerbated by network
fragmentation due to the use of VLANs for broadcast isolation. VLANs
are used for traffic management and also as the mechanism for
providing security and performance isolation among services belonging
to different tenants. The Layer 2 network is carved into
smaller smaller-
sized subnets typically (typically, one subnet per VLAN, VLAN), with VLAN tags
configured on all the Layer 2 switches connected to server racks that
host a given tenant's services. The current VLAN limits
theoretically allow for 4K 4,000 such subnets to be created. The size
of the broadcast domain is typically restricted due to the overhead
of broadcast traffic. The 4K VLAN 4,000-subnet limit on VLANs is no longer
sufficient in a shared infrastructure servicing multiple tenants.

Data center operators must be able to achieve high utilization of
server and network capacity. In order to achieve efficiency efficiency, it
should be possible to assign workloads that operate in a single Layer
2 network to any server in any rack in the network. It should also
be possible to migrate workloads to any server anywhere in the
network while retaining the workloads' addresses. This can be
achieved today by stretching VLANs, however VLANs; however, when workloads migrate migrate,
the network needs to be reconfigured which and that is typically error
prone. By decoupling the workload's location on the LAN from its
network address, the network administrator configures the network once and
once, not every time a service migrates. This decoupling enables any
server to become part of any server resource pool.

The following are key design objectives for next generation next-generation data
centers:

a) location independent location-independent addressing

b) the ability to a scale the number of logical Layer 2/Layer 2 / Layer 3
networks
networks, irrespective of the underlying physical topology or
the number of VLANs

c) preserving Layer 2 semantics for services and allowing them to
retain their addresses as they move within and across data
centers

d) providing broadcast isolation as workloads move around without
burdening the network control plane

This document describes use of the Generic Routing Encapsulation
(GRE, [3][4])
(GRE) header [3] [4] for network virtualization. Network
virtualization decouples a virtual network from the underlying
physical network infrastructure by virtualizing network addresses.
Combined with a management and control plane for the virtual-to-
physical mapping, network virtualization can enable flexible virtual
machine placement and movement, movement and provide network isolation for a
multi-tenant datacenter. data center.

Network virtualization enables customers to bring their own address
spaces into a multi-tenant datacenter data center, while the datacenter data center
administrators can place the customer virtual machines anywhere in
the datacenter data center without reconfiguring their network switches or
routers, irrespective of the customer address spaces.

1.1. Terminology

Please refer to [9][11] RFCs 7364 [10] and 7365 [11] for more formal definition
definitions of terminology. The following terms were are used in this
document.

Customer Address (CA): These are This is the virtual IP addresses address assigned and
configured on the virtual NIC Network Interface Controller (NIC) within
each VM. These are This is the only
addresses address visible to VMs and applications
running within VMs.

Network Virtualization Edge (NVE): An This is an entity that performs
the network virtualization encapsulation and decapsulation.

Provider Address (PA): These are This is the IP addresses address used in the physical
network. PA's PAs are associated with VM CA's CAs through the network
virtualization mapping policy.

Virtual Machine (VM): These are instances This is an instance of OS's an OS running on top of
the hypervisor over a physical machine or server. Multiple VMs can
share the same physical server via the hypervisor, yet are completely
isolated from each other in terms of compute, CPU usage, storage, and other OS
resources.

Virtual Subnet Identifier (VSID): This is a 24-bit ID that uniquely
identifies a virtual subnet or virtual layer Layer 2 broadcast domain.

2. Conventions used Used in this document This Document

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [RFC2119]. RFC 2119 [1].

In this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case Lowercase uses of these words are not to be
interpreted as carrying RFC-2119 significance. the significance defined in RFC 2119.

3. Network Virtualization using Using GRE (NVGRE)

This section describes Network Virtualization using GRE, NVGRE. GRE (NVGRE).
Network virtualization involves creating virtual Layer 2 topologies
on top of a physical Layer 3 network. Connectivity in the virtual
topology is provided by tunneling Ethernet frames in GRE over IP over
the physical network.

In NVGRE, every virtual Layer 2 network is associated with a 24-bit
identifier, called a Virtual Subnet Identifier (VSID). A VSID is
carried in an outer header as defined in Section 3.2. , allowing This allows
unique identification of a tenant's virtual subnet to various devices
in the network. A 24-bit VSID supports up to 16 million virtual
subnets in the same management domain, in contrast to only
4K 4,000 that
is achievable with VLANs. Each VSID represents a virtual Layer 2
broadcast domain, which can be used to identify a virtual subnet of a
given tenant. To support multi-subnet virtual topology, datacenter data center
administrators can configure routes to facilitate communication
between virtual subnets of the same tenant.

GRE is a proposed Proposed Standard from the IETF standard [3][4] [3] [4] and provides a way
for encapsulating an arbitrary protocol over IP. NVGRE leverages the
GRE header to carry VSID information in each packet. The VSID
information in each packet can be used to build multi-tenant-aware
tools for traffic analysis, traffic inspection, and monitoring.

The following sections detail the packet format for NVGRE, NVGRE; describe
the functions of a an NVGRE endpoint, endpoint; illustrate typical traffic flow
both within and across data centers, centers; and discuss address, policy
management address/policy
management, and deployment considerations.

3.1. NVGRE Endpoint

NVGRE endpoints are the ingress/egress points between the virtual and
the physical networks. The NVGRE endpoints are the NVEs as defined
in the NVO Network Virtualization over Layer 3 (NVO3) Framework document [9].
[11]. Any physical server or network device can be an NVGRE
endpoint. One common deployment is for the endpoint to be part of a
hypervisor. The primary function of this endpoint is to
encapsulate/decapsulate Ethernet data frames to and from the GRE
tunnel, ensure Layer 2 semantics, and apply isolation policy scoped
on VSID. The endpoint can optionally participate in routing and
function as a gateway in the virtual topology. To encapsulate an
Ethernet frame, the endpoint needs to know the location information
for the destination address in the frame. This information can be
provisioned via a management plane, plane or obtained via a combination of control plane
control-plane distribution or data
plane data-plane learning approaches. This
document assumes that the location information, including VSID, is
available to the NVGRE endpoint.

3.2. NVGRE frame format Frame Format

The GRE header format as specified in RFC RFCs 2784 [3] and RFC 2890 [3][4] [4] is
used for communication between NVGRE endpoints. NVGRE leverages the
Key extension specified in RFC 2890 [4] to carry the VSID. The
packet format for Layer 2 encapsulation in GRE is shown in Figure 1.

Outer Ethernet Header:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
Outer Ethernet Header: |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Outer) Destination MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|(Outer)Destination MAC Address | (Outer)Source MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Outer) Source MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Optional Ethertype=C-Tag 802.1Q| Outer VLAN Tag Information |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ethertype 0x0800 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

GRE Header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| |1|0| Reserved0 | Ver | Protocol Type 0x6558 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Virtual Subnet ID (VSID) | FlowID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Inner Ethernet Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Inner) Destination MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|(Inner)Destination MAC Address | (Inner)Source MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Inner) Source MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ethertype 0x0800 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 1 1: GRE Encapsulation Frame Format

Note: HL stands for Header Length.

The outer/delivery headers include the outer Ethernet header and the
outer IP header:

o The outer Ethernet header: The source Ethernet address in the
outer frame is set to the MAC address associated with the NVGRE
endpoint. The destination endpoint may or may not be on the same
physical subnet. The destination Ethernet address is set to the
MAC address of the nexthop next-hop IP address for the destination NVE.
The outer VLAN tag information is optional and can be used for
traffic management and broadcast scalability on the physical
network.

o The outer IP header: Both IPv4 and IPv6 can be used as the
delivery protocol for GRE. The IPv4 header is shown for
illustrative purposes. Henceforth Henceforth, the IP address in the outer
frame is referred to as the Provider Address (PA). There can be
one or more PA address associated with an NVGRE endpoint, with policy
controlling the choice of which PA to use for a given Customer
Address (CA) for a customer VM.

The

In the GRE header:

o The C (Checksum Present) and S (Sequence Number Present) bits in
the GRE header MUST be zero.

o The K bit (Key Present) bit in the GRE header MUST be set to one. The
32-bit Key field in the GRE header is used to carry the Virtual
Subnet ID (VSID), (VSID) and the FlowId: FlowID:

- Virtual Subnet ID (VSID): This is a 24-bit value that is used
to identify the NVGRE based NVGRE-based Virtual Layer 2 Network.

- FlowID: This is an 8-bit value that is used to provide per-
flow per-flow
entropy for flows in the same VSID. The FlowID MUST NOT be
modified by transit devices. The encapsulating NVE SHOULD
provide as much entropy as possible in the FlowId. FlowID. If a FlowID
is not generated, it MUST be set to all zero. zeros.

o The protocol type Protocol Type field in the GRE header is set to 0x6558
(transparent
(Transparent Ethernet bridging)[2].

The Bridging) [2].

In the inner headers (headers of the GRE payload):

o The inner Ethernet frame comprises of an inner Ethernet header
followed by optional inner IP header, followed by the IP payload.
The inner frame could be any Ethernet data frame not just IP.
Note that the inner Ethernet frame's FCS Frame Check Sequence (FCS) is
not encapsulated.

o For illustrative purposes purposes, IPv4 headers are shown as the inner IP
headers
headers, but IPv6 headers may be used. Henceforth Henceforth, the IP address
contained in the inner frame is referred to as the Customer
Address (CA).

3.3. Inner 802.1Q Tag as Defined by IEEE 802.1Q

The inner Ethernet header of NVGRE MUST NOT contain the tag as
defined by IEEE 802.1Q tag. [5]. The encapsulating NVE MUST remove any
existing IEEE 802.1Q Tag tag before encapsulation of the frame in NVGRE.
A decapsulating NVE MUST drop the frame if the inner Ethernet frame
contains an IEEE 802.1Q tag.

3.4. Reserved VSID

The VSID range from 0-0xFFF is reserved for future use.

The VSID 0xFFFFFF is reserved for vendor specific NVE-NVE vendor-specific NVE-to-NVE
communication. The sender NVE SHOULD verify the receiver NVE's
vendor before sending a packet using this VSID, however VSID; however, such a
verification mechanism is out of scope of this document.
Implementations SHOULD choose a mechanism that meets their
requirements.

4. NVGRE Deployment Considerations

4.1. ECMP Support

ECMP

Equal-Cost Multipath (ECMP) may be used to provide load balancing.
If ECMP is used, it is RECOMMENDED that the ECMP hash is calculated
either using the outer IP frame fields and entire Key field (32-bit) (32 bits)
or the inner IP and transport frame fields.

4.2. Broadcast and Multicast Traffic

To support broadcast and multicast traffic inside a virtual subnet,
one or more administratively scoped multicast addresses [8][10] [8] [9] can
be assigned for the VSID. All multicast or broadcast traffic
originating from within a VSID is encapsulated and sent to the
assigned multicast address. From an administrative standpoint standpoint, it is
possible for network operators to configure a PA multicast address
for each multicast address that is used inside a VSID, to facilitate VSID; this
facilitates optimal multicast handling. Depending on the hardware
capabilities of the physical network devices and the physical network
architecture, multiple virtual subnet subnets may re-use use the same physical IP
multicast address.

Alternatively, based upon the configuration at NVE, the NVE, broadcast and
multicast in the virtual subnet can be supported using N-Way N-way unicast.
In N-Way N-way unicast, the sender NVE would send one encapsulated packet
to every NVE in the virtual subnet. The sender NVE can encapsulate
and send the packet as described in the Unicast
Traffic Section 4.3. 4.3 ("Unicast Traffic").
This alleviates the need for multicast support in the physical
network.

4.3. Unicast Traffic

The NVGRE endpoint encapsulates a Layer 2 packet in GRE using the
source PA associated with the endpoint with the destination PA
corresponding to the location of the destination endpoint. As
outlined earlier, there can be one or more PAs associated with an
endpoint and policy will control which ones get used for
communication. The encapsulated GRE packet is bridged and routed
normally by the physical network to the destination PA. Bridging
uses the outer Ethernet encapsulation for scope on the LAN. The only
requirement is bi-directional bidirectional IP connectivity from the underlying
physical network. On the destination, the NVGRE endpoint
decapsulates the GRE packet to recover the original Layer 2 frame.
Traffic flows similarly on the reverse path.

4.4. IP Fragmentation

Section 5.1 of RFC 2003 [12] Section 5.1 specifies mechanisms for handling
fragmentation when encapsulating IP within IP. The subset of
mechanisms NVGRE selects are intended to ensure that NVGRE NVGRE-
encapsulated frames are not fragmented after encapsulation en-route en route
to the destination NVGRE endpoint, endpoint and that traffic sources can
leverage Path MTU discovery.

A sender NVE MUST NOT fragment NVGRE packets. A receiver NVE MAY
discard fragmented NVGRE packets. It is RECOMMENDED that the MTU of
the physical network accommodates the larger frame size due to
encapsulation. Path MTU or configuration via control plane can be
used to meet this requirement.

4.5. Address/Policy Management & and Routing

Address acquisition is beyond the scope of this document and can be
obtained statically, dynamically dynamically, or using stateless address auto-
configuration.
autoconfiguration. CA and PA space can be either IPv4 or IPv6. In fact
fact, the address families don't have to match, match; for example, a CA can
be IPv4 while the PA is IPv6 IPv6, and vice versa.

4.6. Cross-subnet, Cross-premise Cross-Subnet, Cross-Premise Communication

One application of this framework is that it provides a seamless path
for enterprises looking to expand their virtual machine hosting
capabilities into public clouds. Enterprises can bring their entire
IP subnet(s) and isolation policies, thus making the transition to or
from the cloud simpler. It is possible to move portions of a an IP
subnet to the cloud however cloud; however, that requires additional configuration
on the enterprise network and is not discussed in this document.
Enterprises can continue to use existing communications models like
site-to-site VPN to secure their traffic.

A VPN gateway is used to establish a secure site-to-site tunnel over
the Internet Internet, and all the enterprise services running in virtual
machines in the cloud use the VPN gateway to communicate back to the
enterprise. For simplicity simplicity, we use a VPN GW gateway configured as a VM shown
(shown in Figure 2 2) to illustrate cross-subnet, cross-premise
communication.

+-----------------------+ +-----------------------+
| Server 1 | | Server 2 |
| +--------+ +--------+ | | +-------------------+ |
| | VM1 | | VM2 | | | | VPN Gateway | |
| | IP=CA1 | | IP=CA2 | | | | Internal External| |
| | | | | | | | IP=CAg IP=GAdc | |
| +--------+ +--------+ | | +-------------------+ |
| Hypervisor | | | Hypervisor| ^ |
+-----------------------+ +-------------------:---+
| IP=PA1 | IP=PA4 | :
| | | :
| +-------------------------+ | : VPN
+-----| Layer 3 Network |------+ : Tunnel
+-------------------------+ :
| :
+-----------------------------------------------:--+
| : |
| Internet : |
| : |
+-----------------------------------------------:--+
| v
| +-------------------+
| | VPN Gateway |
|---| |
IP=GAcorp| External IP=GAcorp|
+-------------------+
|
+-----------------------+
| Corp Layer 3 Network |
| (In CA Space) |
+-----------------------+
|
+---------------------------+
| Server X |
| +----------+ +----------+ |
| | Corp VMe1| | Corp VMe2| |
| | IP=CAe1 | | IP=CAe2 | |
| +----------+ +----------+ |
| Hypervisor |
+---------------------------+

Figure 2 2: Cross-Subnet, Cross-Premise Communication

The packet flow is similar to the unicast traffic flow between VMs, VMs;
the key difference in this case is that the packet needs to be sent
to a VPN gateway before it gets forwarded to the destination. As
part of routing configuration in the CA space, a per-tenant VPN
gateway is provisioned for communication back to the enterprise. The
example illustrates an outbound connection between VM1 inside the datacenter
data center and VMe1 inside the enterprise network. When the
outbound packet from CA1 to CAe1 reaches the hypervisor on Server 1,
the NVE in Server 1 can perform an the equivalent of a route lookup on
the packet. The cross premise cross-premise packet will match the default gateway rule
rule, as CAe1 is not part of the tenant virtual network in the datacenter. data
center. The virtualization policy will indicate the packet to be
encapsulated and sent to the PA of the tenant VPN gateway (PA4)
running as a VM on Server 2. The packet is decapsulated on Server 2
and delivered to the VM gateway. The gateway in turn validates and
sends the packet on the site-to-site VPN tunnel back to the
enterprise network. As the communication here is external to the datacenter
data center, the PA address for the VPN tunnel is globally routable.
The outer header of this packet is sourced from GAdc destined to
GAcorp. This packet is routed through the Internet to the enterprise
VPN gateway gateway, which is the other end of the site-to-site tunnel, tunnel; at which point
that point, the VPN gateway decapsulates the packet and sends it
inside the enterprise where the CAe1 is routable on the network. The
reverse path is similar once the packet reaches the enterprise VPN
gateway.

4.7. Internet Connectivity

To enable connectivity to the Internet, an Internet gateway is needed
that bridges the virtualized CA space to the public Internet address
space. The gateway need needs to perform translation between the
virtualized world and the Internet. For example, the NVGRE endpoint
can be part of a load balancer or a NAT, which NAT that replaces the VPN Gateway
on Server 2 shown in Figure 2.

4.8. Management and Control Planes

There are several protocols that can manage and distribute policy;
however, it is out of outside the scope of this document. Implementations
SHOULD choose a mechanism that meets their scale requirements.

4.9. NVGRE-Aware Devices

One example of a typical deployment consists of virtualized servers
deployed across multiple racks connected by one or more layers of
Layer 2 switches switches, which in turn may be connected to a layer Layer 3 routing
domain. Even though routing in the physical infrastructure will work
without any modification with NVGRE, devices that perform specialized
processing in the network need to be able to parse GRE to get access
to tenant specific tenant-specific information. Devices that understand and parse
the VSID can provide rich multi-tenancy aware multi-tenant-aware services inside the data
center. As outlined earlier earlier, it is imperative to exploit multiple
paths inside the network through techniques such as Equal Cost Multipath (ECMP). ECMP. The Key
field (32-
bit (a 32-bit field, including both the VSID and the optional
FlowID) can provide additional entropy to the switches to exploit
path diversity inside the network. A diverse ecosystem is expected
to emerge as more and more devices become multi-tenant aware. In the
interim, without requiring any hardware upgrades, there are
alternatives to exploit path diversity with GRE by associating
multiple PAs with NVGRE endpoints with policy controlling the choice
of which PA to be used. use.

It is expected that communication can span multiple data centers and
also cross the virtual to physical virtual/physical boundary. Typical scenarios that
require virtual-to-physical communication includes include access to storage
and databases. Scenarios demanding lossless Ethernet functionality
may not be amenable to NVGRE NVGRE, as traffic is carried over an IP
network. NVGRE endpoints mediate between the network virtualized network-virtualized and
non-network virtualized
non-network-virtualized environments. This functionality can be
incorporated into Top of Rack Top-of-Rack switches, storage appliances, load
balancers, routers etc. routers, etc., or built as a stand-alone appliance.

It is imperative to consider the impact of any solution on host
performance. Today's server operating systems employ sophisticated
acceleration techniques such as checksum offload, Large Send Offload
(LSO), Receive Segment Coalescing (RSC), Receive Side Scaling (RSS),
Virtual Machine Queue (VMQ) (VMQ), etc. These technologies should become
NVGRE aware. IPsec Security Associations (SA) (SAs) can be offloaded to
the NIC so that computationally expensive cryptographic operations
are performed at line rate in the NIC hardware. These SAs are based
on the IP addresses of the endpoints. As each packet on the wire
gets translated, the NVGRE endpoint SHOULD intercept the offload
requests and do the appropriate address translation. This will
ensure that IPsec continues to be usable with network virtualization
while taking advantage of hardware offload capabilities for improved
performance.

4.10. Network Scalability with NVGRE

One of the key benefits of using NVGRE is the IP address scalability
and in turn MAC address table scalability that can be achieved. An
NVGRE endpoint can use one PA to represent multiple CAs. This lowers
the burden on the MAC address table sizes at the Top of Rack Top-of-Rack
switches. One obvious benefit is in the context of server
virtualization
virtualization, which has increased the demands on the network
infrastructure. By embedding a an NVGRE endpoint in a hypervisor hypervisor, it
is possible to scale significantly. This framework allows for enables location
information to be preconfigured inside a an NVGRE endpoint endpoint, thus
allowing broadcast ARP traffic to be proxied locally. This approach
can scale to large sized large-sized virtual subnets. These virtual subnets can
be spread across multiple layer Layer 3 physical subnets. It allows
workloads to be moved around without imposing a huge burden on the
network control plane. By eliminating most broadcast traffic and
converting others to multicast multicast, the routers and switches can function
more efficiently optimally by building efficient multicast trees. By using
server and network capacity efficiently efficiently, it is possible to drive down
the cost of building and managing data centers.

5. Security Considerations

This proposal extends the Layer 2 subnet across the data center and
increases the scope for spoofing attacks. Mitigations of such
attacks are possible with authentication/encryption using IPsec or
any other IP based IP-based mechanism. The control plane for policy
distribution is expected to be secured by using any of the existing
security protocols. Further management traffic can be isolated in a
separate subnet/VLAN.

The checksum in the GRE header is not supported. The mitigation of
this is to deploy NVGRE based an NVGRE-based solution in a network that provides
error detection along the NVGRE packet path, for example, using
Ethernet CRC Cyclic Redundancy Check (CRC) or IPsec or any other error
detection mechanism.

6. IANA Considerations

This document has no IANA actions.

7. References

7.1. Normative References

[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997. 1997,
<http://www.rfc-editor.org/info/rfc2119>.

[2] Ethertypes, ftp://ftp.isi.edu/in-
notes/iana/assignments/ethernet-numbers IANA, "IEEE 802 Numbers",
<http://www.iana.org/assignments/ieee-802-numbers>.

[3] D. Farinacci et al, Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. Traina,
"Generic Routing Encapsulation (GRE)", RFC 2784, March, 2000.
DOI 10.17487/RFC2784, March 2000,
<http://www.rfc-editor.org/info/rfc2784>.

[4] G. Dommety, G., "Key and Sequence Number Extensions to GRE",
RFC 2890, DOI 10.17487/RFC2890, September 2000. 2000,
<http://www.rfc-editor.org/info/rfc2890>.

[5] Institute of Electrical IEEE, "IEEE Standard for Local and Electronics Engineers, "Virtual metropolitan area
networks--Media Access Control (MAC) Bridges and Virtual Bridged
Local Area Networks", IEEE Standard 802.1Q, 2005
Edition, May 2006.

7.2. Informative References Std 802.1Q.

[6] A. Greenberg Greenberg, A., et al, al., "VL2: A Scalable and Flexible Data Center
Network", Proc. SIGCOMM 2009. Communications of the ACM,
DOI 10.1145/1897852.1897877, 2011.

[7] A. Greenberg Greenberg, A., et al, al., "The Cost of a Cloud: Research Problems
in
the Data Center", Center Networks", ACM SIGCOMM Computer Communication Review.
Review, DOI 10.1145/1496091.1496103, 2009.

[8] B. Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2006. 2006,
<http://www.rfc-editor.org/info/rfc4291>.

[9] M. Lasserre et al, "Framework for DC Network Virtualization",
RFC 7365, October 2014.

[10] D. Meyer, D., "Administratively Scoped IP Multicast", BCP 23,
RFC 2365, DOI 10.17487/RFC2365, July 1998.

[11] T. Narten et al, 1998,
<http://www.rfc-editor.org/info/rfc2365>.

[10] Narten, T., Ed., Gray, E., Ed., Black, D., Fang, L., Kreeger,
L., and M. Napierala, "Problem Statement: Overlays for Network
Virtualization", RFC 7364, DOI 10.17487/RFC7364, October 2014,
<http://www.rfc-editor.org/info/rfc7364>.

[11] Lasserre, M., Balus, F., Morin, T., Bitar, N., and Y. Rekhter,
"Framework for Data Center (DC) Network Virtualization",
RFC 7365, DOI 10.17487/RFC7365, October 2014. 2014,
<http://www.rfc-editor.org/info/rfc7365>.

[12] C. Perkins, C., "IP Encapsulation within IP", RFC 2003,
DOI 10.17487/RFC2003, October
1996. 1996,
<http://www.rfc-editor.org/info/rfc2003>.

[13] J. Touch, J. and R. Perlman, "Transparent Interconnection of Lots
of Links (TRILL): Problem and Applicability Statement",
RFC 5556, DOI 10.17487/RFC5556, May 2009.

8. Authors and 2009,
<http://www.rfc-editor.org/info/rfc5556>.

Contributors

M. Sridharan
A. Greenberg
Y. Wang
P. Garg
N. Venkataramiah
Microsoft

K. Duda
Arista Networks

I. Ganga
Intel

G. Lin
Google
M. Pearson
Hewlett-Packard

P. Thaler
Broadcom

C. Tumuluri
Emulex

9. Acknowledgments

This document was prepared using 2-Word-v2.0.template.dot.

Authors' Addresses

Murari Sridharan
Microsoft Corporation
1 Microsoft Way
Redmond, WA 98052
United States
Email: muraris@microsoft.com

Yu-Shun Wang
Microsoft Corporation
1 Microsoft Way
Redmond, WA 98052
Email: yushwang@microsoft.com

Albert Greenberg
Microsoft Corporation
1 Microsoft Way
Redmond, WA 98052
United States
Email: albert@microsoft.com

Pankaj Garg

Narasimhan Venkataramiah
Microsoft Corporation
1 Microsoft Way
Redmond, WA 98052
Email: pankajg@microsoft.com

Narasimhan Venkataramiah
Facebook Inc
1730 Minor Ave.
Seattle, WA 98101
United States
Email: navenkat@microsoft.com

Kenneth Duda
Arista Networks, Inc.
5470 Great America Pkwy
Santa Clara, CA 95054
United States
Email: kduda@aristanetworks.com

Ilango Ganga
Intel Corporation
2200 Mission College Blvd.
M/S: SC12-325
Santa Clara, CA - 95054
United States
Email: ilango.s.ganga@intel.com

Geng Lin
Google
1600 Amphitheatre Parkway
Mountain View, California CA 94043
United States
Email: genglin@google.com
Mark Pearson
Hewlett-Packard Co.
8000 Foothills Blvd.
Roseville, CA 95747
United States
Email: mark.pearson@hp.com

Patricia Thaler
Broadcom Corporation
3151 Zanker Road
San Jose, CA 95134
United States
Email: pthaler@broadcom.com

Chait Tumuluri
Emulex Corporation
3333 Susan Street
Costa Mesa, CA 92626
United States
Email: chait@emulex.com

Authors' Addresses

Pankaj Garg (editor)
Microsoft Corporation
1 Microsoft Way
Redmond, WA 98052
United States
Email: pankajg@microsoft.com

Yu-Shun Wang (editor)
Microsoft Corporation
1 Microsoft Way
Redmond, WA 98052
United States
Email: yushwang@microsoft.com