Internet DRAFT - draft-ietf-nvo3-geneve
draft-ietf-nvo3-geneve
Network Working Group J. Gross, Ed.
Internet-Draft
Intended status: Standards Track I. Ganga, Ed.
Expires: September 8, 2020 Intel
T. Sridhar, Ed.
VMware
March 07, 2020
Geneve: Generic Network Virtualization Encapsulation
draft-ietf-nvo3-geneve-16
Abstract
Network virtualization involves the cooperation of devices with a
wide variety of capabilities such as software and hardware tunnel
endpoints, transit fabrics, and centralized control clusters. As a
result of their role in tying together different elements in the
system, the requirements on tunnels are influenced by all of these
components. Flexibility is therefore the most important aspect of a
tunnel protocol if it is to keep pace with the evolution of the
system. This document describes Geneve, an encapsulation protocol
designed to recognize and accommodate these changing capabilities and
needs.
Status of This Memo
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This Internet-Draft will expire on September 8, 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Design Requirements . . . . . . . . . . . . . . . . . . . . . 6
2.1. Control Plane Independence . . . . . . . . . . . . . . . 7
2.2. Data Plane Extensibility . . . . . . . . . . . . . . . . 7
2.2.1. Efficient Implementation . . . . . . . . . . . . . . 8
2.3. Use of Standard IP Fabrics . . . . . . . . . . . . . . . 8
3. Geneve Encapsulation Details . . . . . . . . . . . . . . . . 9
3.1. Geneve Packet Format Over IPv4 . . . . . . . . . . . . . 9
3.2. Geneve Packet Format Over IPv6 . . . . . . . . . . . . . 11
3.3. UDP Header . . . . . . . . . . . . . . . . . . . . . . . 13
3.4. Tunnel Header Fields . . . . . . . . . . . . . . . . . . 14
3.5. Tunnel Options . . . . . . . . . . . . . . . . . . . . . 15
3.5.1. Options Processing . . . . . . . . . . . . . . . . . 17
4. Implementation and Deployment Considerations . . . . . . . . 18
4.1. Applicability Statement . . . . . . . . . . . . . . . . . 18
4.2. Congestion Control Functionality . . . . . . . . . . . . 19
4.3. UDP Checksum . . . . . . . . . . . . . . . . . . . . . . 19
4.3.1. UDP Zero Checksum Handling with IPv6 . . . . . . . . 19
4.4. Encapsulation of Geneve in IP . . . . . . . . . . . . . . 21
4.4.1. IP Fragmentation . . . . . . . . . . . . . . . . . . 21
4.4.2. DSCP, ECN and TTL . . . . . . . . . . . . . . . . . . 22
4.4.3. Broadcast and Multicast . . . . . . . . . . . . . . . 23
4.4.4. Unidirectional Tunnels . . . . . . . . . . . . . . . 23
4.5. Constraints on Protocol Features . . . . . . . . . . . . 24
4.5.1. Constraints on Options . . . . . . . . . . . . . . . 24
4.6. NIC Offloads . . . . . . . . . . . . . . . . . . . . . . 25
4.7. Inner VLAN Handling . . . . . . . . . . . . . . . . . . . 25
5. Transition Considerations . . . . . . . . . . . . . . . . . . 26
6. Security Considerations . . . . . . . . . . . . . . . . . . . 26
6.1. Data Confidentiality . . . . . . . . . . . . . . . . . . 27
6.1.1. Inter-Data Center Traffic . . . . . . . . . . . . . . 27
6.2. Data Integrity . . . . . . . . . . . . . . . . . . . . . 28
6.3. Authentication of NVE peers . . . . . . . . . . . . . . . 29
6.4. Options Interpretation by Transit Devices . . . . . . . . 29
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6.5. Multicast/Broadcast . . . . . . . . . . . . . . . . . . . 29
6.6. Control Plane Communications . . . . . . . . . . . . . . 29
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 31
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 32
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 33
10.1. Normative References . . . . . . . . . . . . . . . . . . 33
10.2. Informative References . . . . . . . . . . . . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 37
1. Introduction
Networking has long featured a variety of tunneling, tagging, and
other encapsulation mechanisms. However, the advent of network
virtualization has caused a surge of renewed interest and a
corresponding increase in the introduction of new protocols. The
large number of protocols in this space, for example, ranging all the
way from VLANs [IEEE.802.1Q_2018] and MPLS [RFC3031] through the more
recent VXLAN [RFC7348] (Virtual eXtensible Local Area Network) and
NVGRE [RFC7637] (Network Virtualization Using Generic Routing
Encapsulation), often leads to questions about the need for new
encapsulation formats and what it is about network virtualization in
particular that leads to their proliferation. Note that the list of
protocols presented above is non-exhaustive.
While many encapsulation protocols seek to simply partition the
underlay network or bridge between two domains, network
virtualization views the transit network as providing connectivity
between multiple components of a distributed system. In many ways
this system is similar to a chassis switch with the IP underlay
network playing the role of the backplane and tunnel endpoints on the
edge as line cards. When viewed in this light, the requirements
placed on the tunnel protocol are significantly different in terms of
the quantity of metadata necessary and the role of transit nodes.
Work such as [VL2] (A Scalable and Flexible Data Center Network) and
the NVO3 Data Plane Requirements
[I-D.ietf-nvo3-dataplane-requirements] have described some of the
properties that the data plane must have to support network
virtualization. However, one additional defining requirement is the
need to carry metadata (e.g. system state) along with the packet
data; example use cases of metadata are noted below. The use of some
metadata is certainly not a foreign concept - nearly all protocols
used for network virtualization have at least 24 bits of identifier
space as a way to partition between tenants. This is often described
as overcoming the limits of 12-bit VLANs, and when seen in that
context, or any context where it is a true tenant identifier, 16
million possible entries is a large number. However, the reality is
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that the metadata is not exclusively used to identify tenants and
encoding other information quickly starts to crowd the space. In
fact, when compared to the tags used to exchange metadata between
line cards on a chassis switch, 24-bit identifiers start to look
quite small. There are nearly endless uses for this metadata,
ranging from storing input port identifiers for simple security
policies to sending service based context for advanced middlebox
applications that terminate and re-encapsulate Geneve traffic.
Existing tunnel protocols have each attempted to solve different
aspects of these new requirements, only to be quickly rendered out of
date by changing control plane implementations and advancements.
Furthermore, software and hardware components and controllers all
have different advantages and rates of evolution - a fact that should
be viewed as a benefit, not a liability or limitation. This draft
describes Geneve, a protocol which seeks to avoid these problems by
providing a framework for tunneling for network virtualization rather
than being prescriptive about the entire system.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
1.2. Terminology
The NVO3 Framework [RFC7365] defines many of the concepts commonly
used in network virtualization. In addition, the following terms are
specifically meaningful in this document:
Checksum offload. An optimization implemented by many NICs (Network
Interface Controller) which enables computation and verification of
upper layer protocol checksums in hardware on transmit and receive,
respectively. This typically includes IP and TCP/UDP checksums which
would otherwise be computed by the protocol stack in software.
Clos network. A technique for composing network fabrics larger than
a single switch while maintaining non-blocking bandwidth across
connection points. ECMP is used to divide traffic across the
multiple links and switches that constitute the fabric. Sometimes
termed "leaf and spine" or "fat tree" topologies.
ECMP. Equal Cost Multipath. A routing mechanism for selecting from
among multiple best next hop paths by hashing packet headers in order
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to better utilize network bandwidth while avoiding reordering of
packets within a flow.
Geneve. Generic Network Virtualization Encapsulation. The tunnel
protocol described in this document.
LRO. Large Receive Offload. The receive-side equivalent function of
LSO, in which multiple protocol segments (primarily TCP) are
coalesced into larger data units.
LSO. Large Segmentation Offload. A function provided by many
commercial NICs that allows data units larger than the MTU to be
passed to the NIC to improve performance, the NIC being responsible
for creating smaller segments of size less than or equal to the MTU
with correct protocol headers. When referring specifically to TCP/
IP, this feature is often known as TSO (TCP Segmentation Offload).
Middlebox. The term middlebox in the context of this document refers
to network service functions or appliances for service interposition
that would typically implement NVE functionality, which terminate or
re-encapsulate Geneve traffic.
NIC. Network Interface Controller. Also called as Network Interface
Card or Network Adapter. A NIC could be part of a tunnel endpoint or
transit device and can either process Geneve packets or aid in the
processing of Geneve packets.
Transit device. A forwarding element (e.g. router or switch) along
the path of the tunnel making up part of the Underlay Network. A
transit device may be capable of understanding the Geneve packet
format but does not originate or terminate Geneve packets.
Tunnel endpoint. A component performing encapsulation and
decapsulation of packets, such as Ethernet frames or IP datagrams, in
Geneve headers. As the ultimate consumer of any tunnel metadata,
tunnel endpoints have the highest level of requirements for parsing
and interpreting tunnel headers. Tunnel endpoints may consist of
either software or hardware implementations or a combination of the
two. Tunnel endpoints are frequently a component of an NVE (Network
Virtualization Edge) but may also be found in middleboxes or other
elements making up an NVO3 Network.
VM. Virtual Machine.
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2. Design Requirements
Geneve is designed to support network virtualization use cases for
data center environments, where tunnels are typically established to
act as a backplane between the virtual switches residing in
hypervisors, physical switches, or middleboxes or other appliances.
An arbitrary IP network can be used as an underlay although Clos
networks composed using ECMP links are a common choice to provide
consistent bisectional bandwidth across all connection points. Many
of the concepts of network virtualization overlays over Layer 3 IP
networks are described in the NVO3 Framework [RFC7365]. Figure 1
shows an example of a hypervisor, top of rack switch for connectivity
to physical servers, and a WAN uplink connected using Geneve tunnels
over a simplified Clos network. These tunnels are used to
encapsulate and forward frames from the attached components such as
VMs or physical links.
+---------------------+ +-------+ +------+
| +--+ +-------+---+ | |Transit|--|Top of|==Physical
| |VM|--| | | | +------+ /|Router | | Rack |==Servers
| +--+ |Virtual|NIC|---|Top of|/ +-------+\/+------+
| +--+ |Switch | | | | Rack |\ +-------+/\+------+
| |VM|--| | | | +------+ \|Transit| |Uplink| WAN
| +--+ +-------+---+ | |Router |--| |=========>
+---------------------+ +-------+ +------+
Hypervisor
()===================================()
Switch-Switch Geneve Tunnels
Figure 1: Sample Geneve Deployment
To support the needs of network virtualization, the tunnel protocol
should be able to take advantage of the differing (and evolving)
capabilities of each type of device in both the underlay and overlay
networks. This results in the following requirements being placed on
the data plane tunneling protocol:
o The data plane is generic and extensible enough to support current
and future control planes.
o Tunnel components are efficiently implementable in both hardware
and software without restricting capabilities to the lowest common
denominator.
o High performance over existing IP fabrics.
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These requirements are described further in the following
subsections.
2.1. Control Plane Independence
Although some protocols for network virtualization have included a
control plane as part of the tunnel format specification (most
notably, VXLAN [RFC7348] prescribed a multicast learning- based
control plane), these specifications have largely been treated as
describing only the data format. The VXLAN packet format has
actually seen a wide variety of control planes built on top of it.
There is a clear advantage in settling on a data format: most of the
protocols are only superficially different and there is little
advantage in duplicating effort. However, the same cannot be said of
control planes, which are diverse in very fundamental ways. The case
for standardization is also less clear given the wide variety in
requirements, goals, and deployment scenarios.
As a result of this reality, Geneve is a pure tunnel format
specification that is capable of fulfilling the needs of many control
planes by explicitly not selecting any one of them. This
simultaneously promotes a shared data format and reduces the chance
of obsolescence by future control plane enhancements.
2.2. Data Plane Extensibility
Achieving the level of flexibility needed to support current and
future control planes effectively requires an options infrastructure
to allow new metadata types to be defined, deployed, and either
finalized or retired. Options also allow for differentiation of
products by encouraging independent development in each vendor's core
specialty, leading to an overall faster pace of advancement. By far
the most common mechanism for implementing options is Type-Length-
Value (TLV) format.
It should be noted that while options can be used to support non-
wirespeed control packets, they are equally important on data packets
as well to segregate and direct forwarding (for instance, the
examples given before of input port based security policies and
terminating/re-encapsulating service interposition both require tags
to be placed on data packets). Therefore, while it would be
desirable to limit the extensibility to only control packets for the
purposes of simplifying the datapath, that would not satisfy the
design requirements.
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2.2.1. Efficient Implementation
There is often a conflict between software flexibility and hardware
performance that is difficult to resolve. For a given set of
functionality, it is obviously desirable to maximize performance.
However, that does not mean new features that cannot be run at a
desired speed today should be disallowed. Therefore, for a protocol
to be efficiently implementable means that a set of common
capabilities can be reasonably handled across platforms along with a
graceful mechanism to handle more advanced features in the
appropriate situations.
The use of a variable length header and options in a protocol often
raises questions about whether it is truly efficiently implementable
in hardware. To answer this question in the context of Geneve, it is
important to first divide "hardware" into two categories: tunnel
endpoints and transit devices.
Tunnel endpoints must be able to parse the variable header, including
any options, and take action. Since these devices are actively
participating in the protocol, they are the most affected by Geneve.
However, as tunnel endpoints are the ultimate consumers of the data,
transmitters can tailor their output to the capabilities of the
recipient.
Transit devices may be able to interpret the options, however, as
non-terminating devices, transit devices do not originate or
terminate the Geneve packet, hence MUST NOT modify Geneve headers and
MUST NOT insert or delete options, which is the responsibility of
tunnel endpoints. Options, if present in the packet, MUST only be
generated and terminated by tunnel endpoints. The participation of
transit devices in interpreting options is OPTIONAL.
Further, either tunnel endpoints or transit devices MAY use offload
capabilities of NICs such as checksum offload to improve the
performance of Geneve packet processing. The presence of a Geneve
variable length header should not prevent the tunnel endpoints and
transit devices from using such offload capabilities.
2.3. Use of Standard IP Fabrics
IP has clearly cemented its place as the dominant transport mechanism
and many techniques have evolved over time to make it robust,
efficient, and inexpensive. As a result, it is natural to use IP
fabrics as a transit network for Geneve. Fortunately, the use of IP
encapsulation and addressing is enough to achieve the primary goal of
delivering packets to the correct point in the network through
standard switching and routing.
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In addition, nearly all underlay fabrics are designed to exploit
parallelism in traffic to spread load across multiple links without
introducing reordering in individual flows. These equal cost
multipathing (ECMP) techniques typically involve parsing and hashing
the addresses and port numbers from the packet to select an outgoing
link. However, the use of tunnels often results in poor ECMP
performance without additional knowledge of the protocol as the
encapsulated traffic is hidden from the fabric by design and only
tunnel endpoint addresses are available for hashing.
Since it is desirable for Geneve to perform well on these existing
fabrics, it is necessary for entropy from encapsulated packets to be
exposed in the tunnel header. The most common technique for this is
to use the UDP source port, which is discussed further in
Section 3.3.
3. Geneve Encapsulation Details
The Geneve packet format consists of a compact tunnel header
encapsulated in UDP over either IPv4 or IPv6. A small fixed tunnel
header provides control information plus a base level of
functionality and interoperability with a focus on simplicity. This
header is then followed by a set of variable options to allow for
future innovation. Finally, the payload consists of a protocol data
unit of the indicated type, such as an Ethernet frame. Section 3.1
and Section 3.2 illustrate the Geneve packet format transported (for
example) over Ethernet along with an Ethernet payload.
3.1. Geneve Packet Format Over IPv4
0 1 2 3
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Outer IPv4 Header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| IHL |Type of Service| Total Length |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identification |Flags| Fragment Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Time to Live |Protocol=17 UDP| Header Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Outer Source IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Outer Destination IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Outer UDP Header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port = xxxx | Dest Port = 6081 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Geneve Header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Ver| Opt Len |O|C| Rsvd. | Protocol Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Virtual Network Identifier (VNI) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Variable Length Options |
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Inner Ethernet Header (example payload):
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Inner Destination MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Inner Destination MAC Address | Inner Source MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Inner Source MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Optional Ethertype=C-Tag 802.1Q| Inner VLAN Tag Information |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Payload:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ethertype of Original Payload | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| Original Ethernet Payload |
| |
| (Note that the original Ethernet Frame's Preamble, Start Frame|
| Delimiter(SFD) & Frame Check Sequence(FCS) are not included |
| and the Ethernet Payload need not be 4-byte aligned) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Frame Check Sequence:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| New Frame Check Sequence (FCS) for Outer Ethernet Frame |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.2. Geneve Packet Format Over IPv6
0 1 2 3
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=0x86DD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Outer IPv6 Header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Traffic Class | Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Length | NxtHdr=17 UDP | Hop Limit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Outer Source IPv6 Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Outer Destination IPv6 Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Outer UDP Header:
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port = xxxx | Dest Port = 6081 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Geneve Header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Ver| Opt Len |O|C| Rsvd. | Protocol Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Virtual Network Identifier (VNI) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Variable Length Options |
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Inner Ethernet Header (example payload):
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Inner Destination MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Inner Destination MAC Address | Inner Source MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Inner Source MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Optional Ethertype=C-Tag 802.1Q| Inner VLAN Tag Information |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Payload:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ethertype of Original Payload | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| Original Ethernet Payload |
| |
| (Note that the original Ethernet Frame's Preamble, Start Frame|
| Delimiter(SFD) & Frame Check Sequence(FCS) are not included |
| and the Ethernet Payload need not be 4-byte aligned) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Frame Check Sequence:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| New Frame Check Sequence (FCS) for Outer Ethernet Frame |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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3.3. UDP Header
The use of an encapsulating UDP [RFC0768] header follows the
connectionless semantics of Ethernet and IP in addition to providing
entropy to routers performing ECMP. The header fields are therefore
interpreted as follows:
Source port: A source port selected by the originating tunnel
endpoint. This source port SHOULD be the same for all packets
belonging to a single encapsulated flow to prevent reordering due
to the use of different paths. To encourage an even distribution
of flows across multiple links, the source port SHOULD be
calculated using a hash of the encapsulated packet headers using,
for example, a traditional 5-tuple. Since the port represents a
flow identifier rather than a true UDP connection, the entire
16-bit range MAY be used to maximize entropy. In addition to
setting the source port, for IPv6, flow label MAY also be used for
providing entropy. For an example of using IPv6 flow label for
tunnel use cases, see [RFC6438].
If Geneve traffic is shared with other UDP listeners on the same
IP address, tunnel endpoints SHOULD implement a mechanism to
ensure ICMP return traffic arising from network errors is directed
to the correct listener. The definition of such a mechanism is
beyond the scope of this document.
Dest port: IANA has assigned port 6081 as the fixed well-known
destination port for Geneve. Although the well-known value should
be used by default, it is RECOMMENDED that implementations make
this configurable. The chosen port is used for identification of
Geneve packets and MUST NOT be reversed for different ends of a
connection as is done with TCP. It is the responsibility of the
control plane for any reconfiguration of the assigned port and its
interpretation by respective devices. The definition of the
control plane is beyond the scope of this document.
UDP length: The length of the UDP packet including the UDP header.
UDP checksum: In order to protect the Geneve header, options and
payload from potential data corruption, UDP checksum SHOULD be
generated as specified in [RFC0768] and [RFC1112] when Geneve is
encapsulated in IPv4. To protect the IP header, Geneve header,
options and payload from potential data corruption, the UDP
checksum MUST be generated by default as specified in [RFC0768]
and [RFC8200] when Geneve is encapsulated in IPv6, except for
certain conditions, which are outlined in the next paragraph.
Upon receiving such packets with non-zero UDP checksum, the
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receiving tunnel endpoints MUST validate the checksum. If the
checksum is not correct, the packet MUST be dropped, otherwise the
packet MUST be accepted for decapsulation.
Under certain conditions, the UDP checksum MAY be set to zero on
transmit for packets encapsulated in both IPv4 and IPv6 [RFC8200].
See Section 4.3 for additional requirements that apply when using
zero UDP checksum with IPv4 and IPv6. Disabling the use of UDP
checksums is an operational consideration that should take into
account the risks and effects of packet corruption.
3.4. Tunnel Header Fields
Ver (2 bits): The current version number is 0. Packets received by
a tunnel endpoint with an unknown version MUST be dropped.
Transit devices interpreting Geneve packets with an unknown
version number MUST treat them as UDP packets with an unknown
payload.
Opt Len (6 bits): The length of the options fields, expressed in
four byte multiples, not including the eight byte fixed tunnel
header. This results in a minimum total Geneve header size of 8
bytes and a maximum of 260 bytes. The start of the payload
headers can be found using this offset from the end of the base
Geneve header.
Transit devices MUST maintain consistent forwarding behavior
irrespective of the value of 'Opt Len', including ECMP link
selection.
O (1 bit): Control packet. This packet contains a control message.
Control messages are sent between tunnel endpoints. Tunnel
endpoints MUST NOT forward the payload and transit devices MUST
NOT attempt to interpret it. Since control messages are less
frequent, it is RECOMMENDED that tunnel endpoints direct these
packets to a high priority control queue (for example, to direct
the packet to a general purpose CPU from a forwarding ASIC or to
separate out control traffic on a NIC). Transit devices MUST NOT
alter forwarding behavior on the basis of this bit, such as ECMP
link selection.
C (1 bit): Critical options present. One or more options has the
critical bit set (see Section 3.5). If this bit is set then
tunnel endpoints MUST parse the options list to interpret any
critical options. On tunnel endpoints where option parsing is not
supported the packet MUST be dropped on the basis of the 'C' bit
in the base header. If the bit is not set tunnel endpoints MAY
strip all options using 'Opt Len' and forward the decapsulated
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packet. Transit devices MUST NOT drop packets on the basis of
this bit.
Rsvd. (6 bits): Reserved field, which MUST be zero on transmission
and MUST be ignored on receipt.
Protocol Type (16 bits): The type of the protocol data unit
appearing after the Geneve header. This follows the EtherType
[ETYPES] convention; with Ethernet itself being represented by the
value 0x6558.
Virtual Network Identifier (VNI) (24 bits): An identifier for a
unique element of a virtual network. In many situations this may
represent an L2 segment, however, the control plane defines the
forwarding semantics of decapsulated packets. The VNI MAY be used
as part of ECMP forwarding decisions or MAY be used as a mechanism
to distinguish between overlapping address spaces contained in the
encapsulated packet when load balancing across CPUs.
Reserved (8 bits): Reserved field which MUST be zero on transmission
and ignored on receipt.
3.5. Tunnel Options
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Class | Type |R|R|R| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Variable Option Data |
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Geneve Option
The base Geneve header is followed by zero or more options in Type-
Length-Value format. Each option consists of a four byte option
header and a variable amount of option data interpreted according to
the type.
Option Class (16 bits): Namespace for the 'Type' field. IANA will
be requested to create a "Geneve Option Class" registry to
allocate identifiers for organizations, technologies, and vendors
that have an interest in creating types for options. Each
organization may allocate types independently to allow
experimentation and rapid innovation. It is expected that over
time certain options will become well known and a given
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implementation may use option types from a variety of sources. In
addition, IANA will be requested to reserve specific ranges for
allocation by IETF Review and for Experimental Use (see
Section 7).
Type (8 bits): Type indicating the format of the data contained in
this option. Options are primarily designed to encourage future
extensibility and innovation and so standardized forms of these
options will be defined in separate documents.
The high order bit of the option type indicates that this is a
critical option. If the receiving tunnel endpoint does not
recognize this option and this bit is set then the packet MUST be
dropped. If this bit is set in any option then the 'C' bit in the
Geneve base header MUST also be set. Transit devices MUST NOT
drop packets on the basis of this bit. The following figure shows
the location of the 'C' bit in the 'Type' field:
0 1 2 3 4 5 6 7 8
+-+-+-+-+-+-+-+-+
|C| Type |
+-+-+-+-+-+-+-+-+
The requirement to drop a packet with an unknown option with the
'C' bit set applies to the entire tunnel endpoint system and not a
particular component of the implementation. For example, in a
system comprised of a forwarding ASIC and a general purpose CPU,
this does not mean that the packet must be dropped in the ASIC.
An implementation may send the packet to the CPU using a rate-
limited control channel for slow-path exception handling.
R (3 bits): Option control flags reserved for future use. These
bits MUST be zero on transmission and MUST be ignored on receipt.
Length (5 bits): Length of the option, expressed in four byte
multiples excluding the option header. The total length of each
option may be between 4 and 128 bytes. A value of 0 in the Length
field implies an option with only an option header and no variable
option data. Packets in which the total length of all options is
not equal to the 'Opt Len' in the base header are invalid and MUST
be silently dropped if received by a tunnel endpoint that
processes the options.
Variable Option Data: Option data interpreted according to 'Type'.
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3.5.1. Options Processing
Geneve options are intended to be originated and processed by tunnel
endpoints. However, options MAY be interpreted by transit devices
along the tunnel path. Transit devices not interpreting Geneve
headers (which may or may not include options) MUST handle Geneve
packets as any other UDP packet and maintain consistent forwarding
behavior.
In tunnel endpoints, the generation and interpretation of options is
determined by the control plane, which is beyond the the scope of
this document. However, to ensure interoperability between
heterogeneous devices some requirements are imposed on options and
the devices that process them:
o Receiving tunnel endpoints MUST drop packets containing unknown
options with the 'C' bit set in the option type. Conversely,
transit devices MUST NOT drop packets as a result of encountering
unknown options, including those with the 'C' bit set.
o The contents of the options and their ordering MUST NOT be
modified by transit devices.
o If a tunnel endpoint receives a Geneve packet with 'Opt Len'
(total length of all options) that exceeds the options processing
capability of the tunnel endpoint then the tunnel endpoint MUST
drop such packets. An implementation may raise an exception to
the control plane of such an event. It is the responsibility of
the control plane to ensure the communicating peer tunnel
endpoints have the processing capability to handle the total
length of options. The definition of the control plane is beyond
the scope of this document.
When designing a Geneve option, it is important to consider how the
option will evolve in the future. Once an option is defined it is
reasonable to expect that implementations may come to depend on a
specific behavior. As a result, the scope of any future changes must
be carefully described upfront.
Architecturally, options are intended to be self-descriptive and
independent. This enables parallelism in option processing and
reduces implementation complexity. However, the control plane may
impose certain ordering restrictions as described in Section 4.5.1.
Unexpectedly significant interoperability issues may result from
changing the length of an option that was defined to be a certain
size. A particular option is specified to have either a fixed
length, which is constant, or a variable length, which may change
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over time or for different use cases. This property is part of the
definition of the option and conveyed by the 'Type'. For fixed
length options, some implementations may choose to ignore the length
field in the option header and instead parse based on the well known
length associated with the type. In this case, redefining the length
will impact not only parsing of the option in question but also any
options that follow. Therefore, options that are defined to be fixed
length in size MUST NOT be redefined to a different length. Instead,
a new 'Type' should be allocated. Actual definition of the option
type is beyond the scope of this document. The option type and its
interpretation should be defined by the entity that owns the option
class.
Options may be processed by NIC hardware utilizing offloads (e.g.
LSO and LRO) as described in Section 4.6. Careful consideration
should be given to how the offload capabilities outlined in
Section 4.6 impact an option's design.
4. Implementation and Deployment Considerations
4.1. Applicability Statement
Geneve is a network virtualization overlay encapsulation protocol
designed to establish tunnels between NVEs over an existing IP
network. It is intended for use in public or private data center
environments, for deploying multi-tenant overlay networks over an
existing IP underlay network.
Geneve is a UDP based encapsulation protocol transported over
existing IPv4 and IPv6 networks. Hence, as a UDP based protocol,
Geneve adheres to the UDP usage guidelines as specified in [RFC8085].
The applicability of these guidelines are dependent on the underlay
IP network and the nature of Geneve payload protocol (example TCP/IP,
IP/Ethernet).
Geneve is intended to be deployed in a data center network
environment operated by a single operator or adjacent set of
cooperating network operators that fits with the definition of
controlled environments in [RFC8085]. A network in a controlled
environment can be managed to operate under certain conditions
whereas in the general Internet this cannot be done. Hence
requirements for a tunnel protocol operating under a controlled
environment can be less restrictive than the requirements of the
general Internet.
For the purpose of this document, a traffic-managed controlled
environment (TMCE) is defined as an IP network that is traffic-
engineered and/or otherwise managed (e.g., via use of traffic rate
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limiters) to avoid congestion. The concept of TMCE is outlined in
[RFC8086]. Significant portions of the text in Section 4.1 through
Section 4.3 are based on [RFC8086] as applicable to Geneve.
It is the responsibility of the operator to ensure that the
guidelines/requirements in this section are followed as applicable to
their Geneve deployment(s).
4.2. Congestion Control Functionality
Geneve does not natively provide congestion control functionality and
relies on the payload protocol traffic for congestion control. As
such Geneve MUST be used with congestion controlled traffic or within
a network that is traffic managed to avoid congestion (TMCE). An
operator of a traffic managed network (TMCE) may avoid congestion by
careful provisioning of their networks, rate-limiting of user data
traffic and traffic engineering according to path capacity.
4.3. UDP Checksum
In order to provide integrity of Geneve headers, options and payload,
(for example to avoid misdelivery of payload to different tenant
systems) in case of data corruption, the outer UDP checksum SHOULD be
used with Geneve when transported over IPv4. The UDP checksum
provides a statistical guarantee that a payload was not corrupted in
transit. These integrity checks are not strong from a coding or
cryptographic perspective and are not designed to detect physical-
layer errors or malicious modification of the datagram (see
Section 3.4 of [RFC8085]). In deployments where such a risk exists,
an operator SHOULD use additional data integrity mechanisms such as
offered by IPsec (see Section 6.2).
An operator MAY choose to disable UDP checksums and use zero
checksums if Geneve packet integrity is provided by other data
integrity mechanisms such as IPsec or additional checksums or if one
of the conditions in Section 4.3.1 a, b, c are met.
By default, UDP checksums MUST be used when Geneve is transported
over IPv6. A tunnel endpoint MAY be configured for use with zero UDP
checksum if additional requirements in Section 4.3.1 are met.
4.3.1. UDP Zero Checksum Handling with IPv6
When Geneve is used over IPv6, the UDP checksum is used to protect
IPv6 headers, UDP headers and Geneve headers, options and payload
from potential data corruption. As such by default Geneve MUST use
UDP checksums when transported over IPv6. An operator MAY choose to
configure to operate with zero UDP checksum if operating in a traffic
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managed controlled environment as stated in Section 4.1 if one of the
following conditions are met.
a. It is known that the packet corruption is exceptionally unlikely
(perhaps based on knowledge of equipment types in their underlay
network) and the operator is willing to take a risk of undetected
packet corruption
b. It is judged through observational measurements (perhaps through
historic or current traffic flows that use non zero checksum)
that the level of packet corruption is tolerably low and where
the operator is willing to take the risk of undetected
corruption.
c. Geneve payload is carrying applications that are tolerant of
misdelivered or corrupted packets (perhaps through higher layer
checksum validation and/or reliability through retransmission)
In addition Geneve tunnel implementations using zero UDP checksum
MUST meet the following requirements:
1. Use of UDP checksum over IPv6 MUST be the default configuration
for all Geneve tunnels.
2. If Geneve is used with zero UDP checksum over IPv6 then such
tunnel endpoint implementation MUST meet all the requirements
specified in Section 4 of [RFC6936] and requirement 1 as
specified in Section 5 of [RFC6936] as that is relevant to
Geneve.
3. The Geneve tunnel endpoint that decapsulates the tunnel SHOULD
check the source and destination IPv6 addresses are valid for the
Geneve tunnel that is configured to receive zero UDP checksum and
discard other packets for which such check fails.
4. The Geneve tunnel endpoint that encapsulates the tunnel MAY use
different IPv6 source addresses for each Geneve tunnel that uses
zero UDP checksum mode in order to strengthen the decapsulator's
check of the IPv6 source address (i.e the same IPv6 source
address is not to be used with more than one IPv6 destination
address, irrespective of whether that destination address is a
unicast or multicast address). When this is not possible, it is
RECOMMENDED to use each source address for as few Geneve tunnels
that use zero UDP checksum as is feasible.
Note that (for requirements 3 and 4) the receiving tunnel
endpoint can apply these checks only if it has out-of-band
knowledge that the encapsulating tunnel endpoint is applying the
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indicated behavior. One possibility to obtain this out-of-band
knowledge is through signaling by the control plane. The
definition of the control plane is beyond the scope of this
document.
5. Measures SHOULD be taken to prevent Geneve traffic over IPv6 with
zero UDP checksum from escaping into the general Internet.
Examples of such measures include employing packet filters at the
gateways or edge of Geneve network and/or keeping logical or
physical separation of the Geneve network from networks carrying
the general Internet traffic.
The above requirements do not change either the requirements
specified in [RFC8200] or the requirements specified in [RFC6936].
The use of the source IPv6 address in addition to the destination
IPv6 address, plus the recommendation against reuse of source IPv6
addresses among Geneve tunnels collectively provide some mitigation
for the absence of UDP checksum coverage of the IPv6 header. A
traffic-managed controlled environment that satisfies at least one of
three conditions listed at the beginning of this section provides
additional assurance.
Editorial Note (The following paragraph to be removed by the RFC
Editor before publication)
It was discussed during TSVART early review if the level of
requirement for using different IPv6 source addresses for different
tunnel destinations would need to be "MAY" or "SHOULD". The
discussion concluded that it was appropriate to keep this as "MAY",
since it was considered not realistic for control planes having to
maintain a high level of state on a per tunnel destination basis. In
addition, the text above provides sufficient guidance to operators
and implementors on possible mitigations.
4.4. Encapsulation of Geneve in IP
As an IP-based tunnel protocol, Geneve shares many properties and
techniques with existing protocols. The application of some of these
are described in further detail, although in general most concepts
applicable to the IP layer or to IP tunnels generally also function
in the context of Geneve.
4.4.1. IP Fragmentation
It is strongly RECOMMENDED that Path MTU Discovery ([RFC1191],
[RFC8201]) be used to prevent or minimize fragmentation. The use of
Path MTU Discovery on the transit network provides the encapsulating
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tunnel endpoint with soft-state about the link that it may use to
prevent or minimize fragmentation depending on its role in the
virtualized network. The NVE can maintain this state (the MTU size
of the tunnel link(s) associated with the tunnel endpoint), so if a
tenant system sends large packets that when encapsulated exceed the
MTU size of the tunnel link, the tunnel endpoint can discard such
packets and send exception messages to the tenant system(s). If the
tunnel endpoint is associated with a routing or forwarding function
and/or has the capability to send ICMP messages, the encapsulating
tunnel endpoint MAY send ICMP fragmentation needed [RFC0792] or
Packet Too Big [RFC4443] messages to the tenant system(s). When
determining the MTU size of a tunnel link, maximum length of options
MUST be assumed as options may vary on a per-packet basis. For
example, recommendations/guidance for handling fragmentation in
similar overlay encapsulation services like PWE3 are provided in
Section 5.3 of [RFC3985].
Note that some implementations may not be capable of supporting
fragmentation or other less common features of the IP header, such as
options and extension headers. For example, some of the issues
associated with MTU size and fragmentation in IP tunneling and use of
ICMP messages is outlined in Section 4.2 of
[I-D.ietf-intarea-tunnels].
4.4.2. DSCP, ECN and TTL
When encapsulating IP (including over Ethernet) packets in Geneve,
there are several considerations for propagating DSCP and ECN bits
from the inner header to the tunnel on transmission and the reverse
on reception.
[RFC2983] provides guidance for mapping DSCP between inner and outer
IP headers. Network virtualization is typically more closely aligned
with the Pipe model described, where the DSCP value on the tunnel
header is set based on a policy (which may be a fixed value, one
based on the inner traffic class, or some other mechanism for
grouping traffic). Aspects of the Uniform model (which treats the
inner and outer DSCP value as a single field by copying on ingress
and egress) may also apply, such as the ability to remark the inner
header on tunnel egress based on transit marking. However, the
Uniform model is not conceptually consistent with network
virtualization, which seeks to provide strong isolation between
encapsulated traffic and the physical network.
[RFC6040] describes the mechanism for exposing ECN capabilities on IP
tunnels and propagating congestion markers to the inner packets.
This behavior MUST be followed for IP packets encapsulated in Geneve.
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Though Uniform or Pipe models could be used for TTL (or Hop Limit in
case of IPv6) handling when tunneling IP packets, the Pipe model is
more aligned with network virtualization. [RFC2003] provides
guidance on handling TTL between inner IP header and outer IP
tunnels; this model is more aligned with the Pipe model and is
RECOMMENDED for use with Geneve for network virtualization
applications.
4.4.3. Broadcast and Multicast
Geneve tunnels may either be point-to-point unicast between two
tunnel endpoints or may utilize broadcast or multicast addressing.
It is not required that inner and outer addressing match in this
respect. For example, in physical networks that do not support
multicast, encapsulated multicast traffic may be replicated into
multiple unicast tunnels or forwarded by policy to a unicast location
(possibly to be replicated there).
With physical networks that do support multicast it may be desirable
to use this capability to take advantage of hardware replication for
encapsulated packets. In this case, multicast addresses may be
allocated in the physical network corresponding to tenants,
encapsulated multicast groups, or some other factor. The allocation
of these groups is a component of the control plane and therefore is
beyond the scope of this document.
When physical multicast is in use, devices with heterogeneous
capabilities may be present in the same group. Some options may only
be interpretable by a subset of the devices in the group. Other
devices can safely ignore such options unless the 'C' bit is set to
mark the unknown option as critical. Requirements outlined in
Section 3.4 apply for critical options.
In addition, [RFC8293] provides examples of various mechanisms that
can be used for multicast handling in network virtualization overlay
networks.
4.4.4. Unidirectional Tunnels
Generally speaking, a Geneve tunnel is a unidirectional concept. IP
is not a connection oriented protocol and it is possible for two
tunnel endpoints to communicate with each other using different paths
or to have one side not transmit anything at all. As Geneve is an
IP-based protocol, the tunnel layer inherits these same
characteristics.
It is possible for a tunnel to encapsulate a protocol, such as TCP,
which is connection oriented and maintains session state at that
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layer. In addition, implementations MAY model Geneve tunnels as
connected, bidirectional links, such as to provide the abstraction of
a virtual port. In both of these cases, bidirectionality of the
tunnel is handled at a higher layer and does not affect the operation
of Geneve itself.
4.5. Constraints on Protocol Features
Geneve is intended to be flexible to a wide range of current and
future applications. As a result, certain constraints may be placed
on the use of metadata or other aspects of the protocol in order to
optimize for a particular use case. For example, some applications
may limit the types of options which are supported or enforce a
maximum number or length of options. Other applications may only
handle certain encapsulated payload types, such as Ethernet or IP.
This could be either globally throughout the system or, for example,
restricted to certain classes of devices or network paths.
These constraints may be communicated to tunnel endpoints either
explicitly through a control plane or implicitly by the nature of the
application. As Geneve is defined as a data plane protocol that is
control plane agnostic, definition of such mechanisms are beyond the
scope of this document.
4.5.1. Constraints on Options
While Geneve options are flexible, a control plane may restrict the
number of option TLVs as well as the order and size of the TLVs
between tunnel endpoints to make it simpler for a data plane
implementation in software or hardware to handle
[I-D.ietf-nvo3-encap]. For example, there may be some critical
information such as a secure hash that must be processed in a certain
order to provide lowest latency or there may be other scenarios where
the options must be processed in a certain order due to protocol
semantics.
A control plane may negotiate a subset of option TLVs and certain TLV
ordering, as well may limit the total number of option TLVs present
in the packet, for example, to accommodate hardware capable of
processing fewer options [I-D.ietf-nvo3-encap]. Hence, a control
plane needs to have the ability to describe the supported TLVs subset
and their order to the tunnel endpoints. In the absence of a control
plane, alternative configuration mechanisms may be used for this
purpose. Such mechanisms are beyond the scope of this document.
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4.6. NIC Offloads
Modern NICs currently provide a variety of offloads to enable the
efficient processing of packets. The implementation of many of these
offloads requires only that the encapsulated packet be easily parsed
(for example, checksum offload). However, optimizations such as LSO
and LRO involve some processing of the options themselves since they
must be replicated/merged across multiple packets. In these
situations, it is desirable to not require changes to the offload
logic to handle the introduction of new options. To enable this,
some constraints are placed on the definitions of options to allow
for simple processing rules:
o When performing LSO, a NIC MUST replicate the entire Geneve header
and all options, including those unknown to the device, onto each
resulting segment unless an option allows an exception.
Conversely, when performing LRO, a NIC may assume that a binary
comparison of the options (including unknown options) is
sufficient to ensure equality and MAY merge packets with equal
Geneve headers.
o Options MUST NOT be reordered during the course of offload
processing, including when merging packets for the purpose of LRO.
o NICs performing offloads MUST NOT drop packets with unknown
options, including those marked as critical, unless explicitly
configured.
There is no requirement that a given implementation of Geneve employ
the offloads listed as examples above. However, as these offloads
are currently widely deployed in commercially available NICs, the
rules described here are intended to enable efficient handling of
current and future options across a variety of devices.
4.7. Inner VLAN Handling
Geneve is capable of encapsulating a wide range of protocols and
therefore a given implementation is likely to support only a small
subset of the possibilities. However, as Ethernet is expected to be
widely deployed, it is useful to describe the behavior of VLANs
inside encapsulated Ethernet frames.
As with any protocol, support for inner VLAN headers is OPTIONAL. In
many cases, the use of encapsulated VLANs may be disallowed due to
security or implementation considerations. However, in other cases
trunking of VLAN frames across a Geneve tunnel can prove useful. As
a result, the processing of inner VLAN tags upon ingress or egress
from a tunnel endpoint is based upon the configuration of the tunnel
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endpoint and/or control plane and not explicitly defined as part of
the data format.
5. Transition Considerations
Viewed exclusively from the data plane, Geneve is compatible with
existing IP networks as it appears to most devices as UDP packets.
However, as there are already a number of tunnel protocols deployed
in network virtualization environments, there is a practical question
of transition and coexistence.
Since Geneve builds on the base data plane functionality provided by
the most common protocols used for network virtualization (VXLAN,
NVGRE) it should be straightforward to port an existing control plane
to run on top of it with minimal effort. With both the old and new
packet formats supporting the same set of capabilities, there is no
need for a hard transition - tunnel endpoints directly communicating
with each other can use any common protocol, which may be different
even within a single overall system. As transit devices are
primarily forwarding packets on the basis of the IP header, all
protocols appear similar and these devices do not introduce
additional interoperability concerns.
To assist with this transition, it is strongly suggested that
implementations support simultaneous operation of both Geneve and
existing tunnel protocols as it is expected to be common for a single
node to communicate with a mixture of other nodes. Eventually, older
protocols may be phased out as they are no longer in use.
6. Security Considerations
As encapsulated within a UDP/IP packet, Geneve does not have any
inherent security mechanisms. As a result, an attacker with access
to the underlay network transporting the IP packets has the ability
to snoop, alter or inject packets. Compromised tunnel endpoints or
transit devices may also spoof identifiers in the tunnel header to
gain access to networks owned by other tenants.
Within a particular security domain, such as a data center operated
by a single service provider, the most common and highest performing
security mechanism is isolation of trusted components. Tunnel
traffic can be carried over a separate VLAN and filtered at any
untrusted boundaries.
When crossing an untrusted link, such as the general Internet, VPN
technologies such as IPsec [RFC4301] should be used to provide
authentication and/or encryption of the IP packets formed as part of
Geneve encapsulation (See Section 6.1.1).
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Geneve does not otherwise affect the security of the encapsulated
packets. As per the guidelines of BCP 72 [RFC3552], the following
sections describe potential security risks that may be applicable to
Geneve deployments and approaches to mitigate such risks. It is also
noted that not all such risks are applicable to all Geneve deployment
scenarios, i.e., only a subset may be applicable to certain
deployments. So an operator has to make an assessment based on their
network environment and determine the risks that are applicable to
their specific environment and use appropriate mitigation approaches
as applicable.
6.1. Data Confidentiality
Geneve is a network virtualization overlay encapsulation protocol
designed to establish tunnels between NVEs over an existing IP
network. It can be used to deploy multi-tenant overlay networks over
an existing IP underlay network in a public or private data center.
The overlay service is typically provided by a service provider, for
example a cloud services provider or a private data center operator,
this may or not may be the same provider as an underlay service
provider. Due to the nature of multi-tenancy in such environments, a
tenant system may expect data confidentiality to ensure its packet
data is not tampered with (active attack) in transit or a target of
unauthorized monitoring (passive attack) for example by other tenant
systems or underlay service provider. A compromised network node or
a transit device within a data center may passively monitor Geneve
packet data between NVEs; or route traffic for further inspection. A
tenant may expect the overlay service provider to provide data
confidentiality as part of the service or a tenant may bring its own
data confidentiality mechanisms like IPsec or TLS to protect the data
end to end between its tenant systems. The overlay provider is
expected to provide cryptographic protection in cases where the
underlay provider is not the same as the overlay provider to ensure
the payload is not exposed to the underlay.
If an operator determines data confidentiality is necessary in their
environment based on their risk analysis, for example as in multi-
tenant environments, then an encryption mechanism SHOULD be used to
encrypt the tenant data end to end between the NVEs. The NVEs may
use existing well established encryption mechanisms such as IPsec,
DTLS, etc.
6.1.1. Inter-Data Center Traffic
A tenant system in a customer premises (private data center) may want
to connect to tenant systems on their tenant overlay network in a
public cloud data center or a tenant may want to have its tenant
systems located in multiple geographically separated data centers for
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high availability. Geneve data traffic between tenant systems across
such separated networks should be protected from threats when
traversing public networks. Any Geneve overlay data leaving the data
center network beyond the operator's security domain SHOULD be
secured by encryption mechanisms such as IPsec or other VPN
technologies to protect the communications between the NVEs when they
are geographically separated over untrusted network links.
Specification of data protection mechanisms employed between data
centers is beyond the scope of this document.
The principles described in Section 4 regarding controlled
environments still apply to the geographically separated data center
usage outlined in this section.
6.2. Data Integrity
Geneve encapsulation is used between NVEs to establish overlay
tunnels over an existing IP underlay network. In a multi-tenant data
center, a rogue or compromised tenant system may try to launch a
passive attack such as monitoring the traffic of other tenants, or an
active attack such as trying to inject unauthorized Geneve
encapsulated traffic such as spoofing, replay, etc., into the
network. To prevent such attacks, an NVE MUST NOT propagate Geneve
packets beyond the NVE to tenant systems and SHOULD employ packet
filtering mechanisms so as not to forward unauthorized traffic
between tenant systems in different tenant networks. An NVE MUST NOT
interpret Geneve packets from tenant systems other than as frames to
be encapsulated.
A compromised network node or a transit device within a data center
may launch an active attack trying to tamper with the Geneve packet
data between NVEs. Malicious tampering of Geneve header fields may
cause the packet from one tenant to be forwarded to a different
tenant network. If an operator determines the possibility of such
threat in their environment, the operator may choose to employ data
integrity mechanisms between NVEs. In order to prevent such risks, a
data integrity mechanism SHOULD be used in such environments to
protect the integrity of Geneve packets including packet headers,
options and payload on communications between NVE pairs. A
cryptographic data protection mechanism such as IPsec may be used to
provide data integrity protection. A data center operator may choose
to deploy any other data integrity mechanisms as applicable and
supported in their underlay networks, although non-cryptographic
mechanisms may not protect the Geneve portion of the packet from
tampering.
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6.3. Authentication of NVE peers
A rogue network device or a compromised NVE in a data center
environment might be able to spoof Geneve packets as if it came from
a legitimate NVE. In order to mitigate such a risk, an operator
SHOULD use an authentication mechanism, such as IPsec to ensure that
the Geneve packet originated from the intended NVE peer, in
environments where the operator determines spoofing or rogue devices
is a potential threat. Other simpler source checks such as ingress
filtering for VLAN/MAC/IP address, reverse path forwarding checks,
etc., may be used in certain trusted environments to ensure Geneve
packets originated from the intended NVE peer.
6.4. Options Interpretation by Transit Devices
Options, if present in the packet, are generated and terminated by
tunnel endpoints. As indicated in Section 2.2.1, transit devices may
interpret the options. However, if the packet is protected by tunnel
endpoint to tunnel endpoint encryption, for example through IPsec,
transit devices will not have visibility into the Geneve header or
options in the packet. In such cases transit devices MUST handle
Geneve packets as any other IP packet and maintain consistent
forwarding behavior. In cases where options are interpreted by
transit devices, the operator MUST ensure that transit devices are
trusted and not compromised. The definition of a mechanism to ensure
this trust is beyond the scope of this document.
6.5. Multicast/Broadcast
In typical data center networks where IP multicasting is not
supported in the underlay network, multicasting may be supported
using multiple unicast tunnels. The same security requirements as
described in the above sections can be used to protect Geneve
communications between NVE peers. If IP multicasting is supported in
the underlay network and the operator chooses to use it for multicast
traffic among tunnel endpoints, then the operator in such
environments may use data protection mechanisms such as IPsec with
multicast extensions [RFC5374] to protect multicast traffic among
Geneve NVE groups.
6.6. Control Plane Communications
A Network Virtualization Authority (NVA) as outlined in [RFC8014] may
be used as a control plane for configuring and managing the Geneve
NVEs. The data center operator is expected to use security
mechanisms to protect the communications between the NVA to NVEs and
use authentication mechanisms to detect any rogue or compromised NVEs
within their administrative domain. Data protection mechanisms for
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control plane communication or authentication mechanisms between the
NVA and the NVEs are beyond the scope of this document.
7. IANA Considerations
IANA has allocated UDP port 6081 in the Service Name and Transport
Protocol Port Number Registry [IANA-SN] as the well-known destination
port for Geneve based on early registration.
Upon publication of this document, this registration will have its
reference changed to cite this document [RFC-to-be] and inline with
[RFC6335] the assignee and contact of the port entry should be
changed to IESG <iesg@ietf.org> and IETF Chair <chair@ietf.org>
respectively:
Service Name: geneve
Transport Protocol(s): UDP
Assignee: IESG <iesg@ietf.org>
Contact: IETF Chair <chair@ietf.org>
Description: Generic Network Virtualization Encapsulation (Geneve)
Reference: [RFC-to-be]
Port Number: 6081
In addition, IANA is requested to create a new "Geneve Option Class"
registry to allocate Option Classes. This registry is to be placed
under a new Network Virtualization Overlay (NVO3) protocols page (to
be created) in IANA protocol registries [IANA-PR]. The Geneve Option
Class registry shall consist of 16-bit hexadecimal values along with
descriptive strings, assignee/contact information and references.
The registration rules for the new registry are (as defined by
[RFC8126]):
+----------------+-------------------------+
| Range | Registration Procedures |
+----------------+-------------------------+
| 0x0000..0x00FF | IETF Review |
| 0x0100..0xFEFF | First Come First Served |
| 0xFF00..0xFFFF | Experimental Use |
+----------------+-------------------------+
Initial registrations in the new registry are as follows:
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+----------------+------------------+------------------+------------+
| Option Class | Description | Assignee/Contact | References |
+----------------+------------------+------------------+------------+
| 0x0100 | Linux | | |
| 0x0101 | Open vSwitch | | |
| | (OVS) | | |
| 0x0102 | Open Virtual | | |
| | Networking (OVN) | | |
| 0x0103 | In-band Network | | |
| | Telemetry (INT) | | |
| 0x0104 | VMware, Inc. | | |
| 0x0105 | Amazon.com, Inc. | | |
| 0x0106 | Cisco Systems, | | |
| | Inc. | | |
| 0x0107 | Oracle | | |
| | Corporation | | |
| 0x0108..0x0110 | Amazon.com, Inc. | | |
+----------------+------------------+------------------+------------+
8. Contributors
The following individuals were authors of an earlier version of this
document and made significant contributions:
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Pankaj Garg
Microsoft Corporation
1 Microsoft Way
Redmond, WA 98052
USA
Email: pankajg@microsoft.com
Chris Wright
Red Hat Inc.
1801 Varsity Drive
Raleigh, NC 27606
USA
Email: chrisw@redhat.com
Kenneth Duda
Arista Networks
5453 Great America Parkway
Santa Clara, CA 95054
USA
Email: kduda@arista.com
Dinesh G. Dutt
Independent
Email: didutt@gmail.com
Jon Hudson
Independent
Email: jon.hudson@gmail.com
Ariel Hendel
Facebook, Inc.
1 Hacker Way
Menlo Park, CA 94025
USA
Email: ahendel@fb.com
9. Acknowledgements
The authors wish to acknowledge Puneet Agarwal, David Black, Sami
Boutros, Scott Bradner, Martin Casado, Alissa Cooper, Roman Danyliw,
Bruce Davie, Anoop Ghanwani, Benjamin Kaduk, Suresh Krishnan, Mirja
Kuhlewind, Barry Leiba, Daniel Migault, Greg Mirksy, Tal Mizrahi,
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Kathleen Moriarty, Magnus Nystrom, Adam Roach, Sabrina Tanamal, Dave
Thaler, Eric Vyncke, Magnus Westerlund and many other members of the
NVO3 WG for their reviews, comments and suggestions.
The authors would like to thank Sam Aldrin, Alia Atlas, Matthew
Bocci, Benson Schliesser, and Martin Vigoureux for their guidance
throughout the process.
10. References
10.1. Normative References
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
DOI 10.17487/RFC0768, August 1980,
<https://www.rfc-editor.org/info/rfc768>.
[RFC0792] Postel, J., "Internet Control Message Protocol", STD 5,
RFC 792, DOI 10.17487/RFC0792, September 1981,
<https://www.rfc-editor.org/info/rfc792>.
[RFC1112] Deering, S., "Host extensions for IP multicasting", STD 5,
RFC 1112, DOI 10.17487/RFC1112, August 1989,
<https://www.rfc-editor.org/info/rfc1112>.
[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
DOI 10.17487/RFC1191, November 1990,
<https://www.rfc-editor.org/info/rfc1191>.
[RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003,
DOI 10.17487/RFC2003, October 1996,
<https://www.rfc-editor.org/info/rfc2003>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", STD 89,
RFC 4443, DOI 10.17487/RFC4443, March 2006,
<https://www.rfc-editor.org/info/rfc4443>.
[RFC6040] Briscoe, B., "Tunnelling of Explicit Congestion
Notification", RFC 6040, DOI 10.17487/RFC6040, November
2010, <https://www.rfc-editor.org/info/rfc6040>.
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[RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement
for the Use of IPv6 UDP Datagrams with Zero Checksums",
RFC 6936, DOI 10.17487/RFC6936, April 2013,
<https://www.rfc-editor.org/info/rfc6936>.
[RFC7365] 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, <https://www.rfc-editor.org/info/rfc7365>.
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <https://www.rfc-editor.org/info/rfc8085>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
[RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed.,
"Path MTU Discovery for IP version 6", STD 87, RFC 8201,
DOI 10.17487/RFC8201, July 2017,
<https://www.rfc-editor.org/info/rfc8201>.
10.2. Informative References
[ETYPES] The IEEE Registration Authority, "IEEE 802 Numbers",
<https://www.iana.org/assignments/ieee-802-numbers>.
[I-D.ietf-intarea-tunnels]
Touch, J. and M. Townsley, "IP Tunnels in the Internet
Architecture", draft-ietf-intarea-tunnels-10 (work in
progress), September 2019.
[I-D.ietf-nvo3-dataplane-requirements]
Bitar, N., Lasserre, M., Balus, F., Morin, T., Jin, L.,
and B. Khasnabish, "NVO3 Data Plane Requirements", draft-
ietf-nvo3-dataplane-requirements-03 (work in progress),
April 2014.
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[I-D.ietf-nvo3-encap]
Boutros, S., "NVO3 Encapsulation Considerations", draft-
ietf-nvo3-encap-05 (work in progress), February 2020.
[IANA-PR] IANA, "Protocol Registries",
<https://www.iana.org/protocols>.
[IANA-SN] IANA, "Service Name and Transport Protocol Port Number
Registry", <https://www.iana.org/assignments/service-
names-port-numbers>.
[IEEE.802.1Q_2018]
IEEE, "IEEE Standard for Local and Metropolitan Area
Networks--Bridges and Bridged Networks", IEEE 802.1Q-2018,
DOI 10.1109/ieeestd.2018.8403927, July 2018,
<http://ieeexplore.ieee.org/servlet/
opac?punumber=8403925>.
[RFC2983] Black, D., "Differentiated Services and Tunnels",
RFC 2983, DOI 10.17487/RFC2983, October 2000,
<https://www.rfc-editor.org/info/rfc2983>.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001,
<https://www.rfc-editor.org/info/rfc3031>.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552,
DOI 10.17487/RFC3552, July 2003,
<https://www.rfc-editor.org/info/rfc3552>.
[RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
Edge-to-Edge (PWE3) Architecture", RFC 3985,
DOI 10.17487/RFC3985, March 2005,
<https://www.rfc-editor.org/info/rfc3985>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <https://www.rfc-editor.org/info/rfc4301>.
[RFC5374] Weis, B., Gross, G., and D. Ignjatic, "Multicast
Extensions to the Security Architecture for the Internet
Protocol", RFC 5374, DOI 10.17487/RFC5374, November 2008,
<https://www.rfc-editor.org/info/rfc5374>.
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[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165,
RFC 6335, DOI 10.17487/RFC6335, August 2011,
<https://www.rfc-editor.org/info/rfc6335>.
[RFC6438] Carpenter, B. and S. Amante, "Using the IPv6 Flow Label
for Equal Cost Multipath Routing and Link Aggregation in
Tunnels", RFC 6438, DOI 10.17487/RFC6438, November 2011,
<https://www.rfc-editor.org/info/rfc6438>.
[RFC7348] Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
eXtensible Local Area Network (VXLAN): A Framework for
Overlaying Virtualized Layer 2 Networks over Layer 3
Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,
<https://www.rfc-editor.org/info/rfc7348>.
[RFC7637] Garg, P., Ed. and Y. Wang, Ed., "NVGRE: Network
Virtualization Using Generic Routing Encapsulation",
RFC 7637, DOI 10.17487/RFC7637, September 2015,
<https://www.rfc-editor.org/info/rfc7637>.
[RFC8014] Black, D., Hudson, J., Kreeger, L., Lasserre, M., and T.
Narten, "An Architecture for Data-Center Network
Virtualization over Layer 3 (NVO3)", RFC 8014,
DOI 10.17487/RFC8014, December 2016,
<https://www.rfc-editor.org/info/rfc8014>.
[RFC8086] Yong, L., Ed., Crabbe, E., Xu, X., and T. Herbert, "GRE-
in-UDP Encapsulation", RFC 8086, DOI 10.17487/RFC8086,
March 2017, <https://www.rfc-editor.org/info/rfc8086>.
[RFC8293] Ghanwani, A., Dunbar, L., McBride, M., Bannai, V., and R.
Krishnan, "A Framework for Multicast in Network
Virtualization over Layer 3", RFC 8293,
DOI 10.17487/RFC8293, January 2018,
<https://www.rfc-editor.org/info/rfc8293>.
[VL2] "VL2: A Scalable and Flexible Data Center Network", ACM
SIGCOMM Computer Communication Review,
DOI 10.1145/1594977.1592576, 2009,
<https://www.sigcomm.org/sites/default/files/ccr/
papers/2009/October/1594977-1592576.pdf>.
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Authors' Addresses
Jesse Gross (editor)
Email: jesse@kernel.org
Ilango Ganga (editor)
Intel Corporation
2200 Mission College Blvd.
Santa Clara, CA 95054
USA
Email: ilango.s.ganga@intel.com
T. Sridhar (editor)
VMware, Inc.
3401 Hillview Ave.
Palo Alto, CA 94304
USA
Email: tsridhar@vmware.com
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