Internet DRAFT - draft-gross-geneve
draft-gross-geneve
Network Working Group J. Gross
Internet-Draft T. Sridhar
Intended status: Standards Track VMware
Expires: April 28, 2015 P. Garg
Microsoft
C. Wright
Red Hat
I. Ganga
Intel
P. Agarwal
Broadcom
K. Duda
Arista
D. Dutt
Cumulus
J. Hudson
Brocade
October 25, 2014
Geneve: Generic Network Virtualization Encapsulation
draft-gross-geneve-02
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 draft describes Geneve, a protocol designed to
recognize and accommodate these changing capabilities and needs.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 28, 2015.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Design Requirements . . . . . . . . . . . . . . . . . . . . . 5
2.1. Control Plane Independence . . . . . . . . . . . . . . . 6
2.2. Data Plane Extensibility . . . . . . . . . . . . . . . . 7
2.2.1. Efficient Implementation . . . . . . . . . . . . . . 7
2.3. Use of Standard IP Fabrics . . . . . . . . . . . . . . . 8
3. Geneve Encapsulation Details . . . . . . . . . . . . . . . . 9
3.1. Geneve Frame Format Over IPv4 . . . . . . . . . . . . . . 9
3.2. Geneve Frame Format Over IPv6 . . . . . . . . . . . . . . 10
3.3. UDP Header . . . . . . . . . . . . . . . . . . . . . . . 12
3.4. Tunnel Header Fields . . . . . . . . . . . . . . . . . . 13
3.5. Tunnel Options . . . . . . . . . . . . . . . . . . . . . 14
3.5.1. Options Processing . . . . . . . . . . . . . . . . . 16
4. Implementation and Deployment Considerations . . . . . . . . 16
4.1. Encapsulation of Geneve in IP . . . . . . . . . . . . . . 16
4.1.1. IP Fragmentation . . . . . . . . . . . . . . . . . . 16
4.1.2. DSCP and ECN . . . . . . . . . . . . . . . . . . . . 17
4.1.3. Broadcast and Multicast . . . . . . . . . . . . . . . 17
4.2. NIC Offloads . . . . . . . . . . . . . . . . . . . . . . 18
4.3. Inner VLAN Handling . . . . . . . . . . . . . . . . . . . 18
5. Interoperability Issues . . . . . . . . . . . . . . . . . . . 19
6. Security Considerations . . . . . . . . . . . . . . . . . . . 19
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20
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9. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
9.1. Normative References . . . . . . . . . . . . . . . . . . 20
9.2. Informative References . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
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, ranging all the way from
VLANs [IEEE.802.1Q-2011] and MPLS [RFC3031] through the more recent
VXLAN [RFC7348], NVGRE [I-D.sridharan-virtualization-nvgre], and STT
[I-D.davie-stt], 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.
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 an integrated 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.
Current work such as [VL2] and the NVO3 working group
[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 system state along with the packet data. The use of
some metadata is certainly not a foreign concept - nearly all
protocols used for 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
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 ports for simple security policies to
service based context for interposing advanced middleboxes.
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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", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
In this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to be
interpreted as carrying RFC-2119 significance.
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 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
to better utilize network bandwidth while avoiding reordering a
single stream.
Geneve. Generic Network Virtualization Encapsulation. The tunnel
protocol described in this draft.
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LRO. Large Receive Offload. The receive-side equivalent function of
LSO, in which multiple protocol segments (primarily TCP) are
coalesced into larger data units.
NIC. Network Interface Card. 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.
OAM. Operations, Administration, and Management. A suite of tools
used to monitor and troubleshoot network problems.
Transit device. A forwarding element along the path of the tunnel
making up part of the Underlay Network. A transit device MAY be
capable of understanding the Geneve frame format but does not
originate or terminate Geneve packets.
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 with correct protocol headers. When
referring specifically to TCP/IP, this feature is often known as TSO
(TCP Segmentation Offload).
Tunnel endpoint. A component encapsulating packets, such as Ethernet
frames or IP datagrams, in Geneve headers and vice versa. As the
ultimate consumer of any tunnel metadata, 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. Endpoints are
frequently a component of an NVE but may also be found in middleboxes
or other elements making up an NVO3 Network.
VM. Virtual Machine.
2. Design Requirements
Geneve is designed to support network virtualization use cases, 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. 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.
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+---------------------+ +-------+ +------+
| +--+ +-------+---+ | |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.
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, the original VXLAN spec prescribed a multicast learning-
based control plane), these specifications have largely been treated
as describing only the data format. The VXLAN frame 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.
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As a result of this reality, Geneve aims to be 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 increases the
chances that it will not be obsoleted 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 frames, they are equally important on data frames
as well to segregate and direct forwarding (for instance, the
examples given before of input port based security policies and
service interposition both require tags to be placed on data
packets). Therefore, while it would be desirable to limit the
extensibility to only control frames for the purposes of simplifying
the datapath, that would not satisfy the design requirements.
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 that
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.
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.
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However, as endpoints are the ultimate consumers of the data,
transmitters can tailor their output to the capabilities of the
recipient. As new functionality becomes sufficiently well defined to
add to endpoints, supporting options can be designed using ordering
restrictions and other techniques to ease parsing.
Transit devices MAY be able to interpret the options and participate
in Geneve packet processing. However, as non-terminating devices,
they do not originate or terminate the Geneve packet. The
participation of transit devices in Geneve packet processing 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.
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
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.
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3. Geneve Encapsulation Details
The Geneve frame 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. The following
subsections provide examples of Geneve frames transported (for
example) over Ethernet along with an Ethernet payload.
3.1. Geneve Frame 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identification |Flags| Fragment Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Time to Live |Protocol=17 UDP| Header Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Outer Source IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Outer Destination IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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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 FCS is not included) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Frame Check Sequence:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| New FCS (Frame Check Sequence) for Outer Ethernet Frame |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.2. Geneve Frame Format Over IPv6
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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:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port = xxxx | Dest Port = 6081 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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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 FCS is not included) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Frame Check Sequence:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| New FCS (Frame Check Sequence) for Outer Ethernet Frame |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 ingress 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
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rather than a true UDP connection, the entire 16-bit range MAY be
used to maximize entropy.
Dest port: IANA has assigned port 6081 as the fixed well-known
destination port for Geneve. This port MUST be used in both
directions of a flow. Although the well-known value should be
used by default, it is RECOMMENDED that implementations make this
configurable.
UDP length: The length of the UDP packet including the UDP header.
UDP checksum: The checksum MAY be set to zero on transmit for
packets encapsulated in both IPv4 and IPv6 [RFC6935]. When a
packet is received with a UDP checksum of zero it MUST be accepted
and decapsulated. If the ingress tunnel endpoint optionally
encapsulates a packet with a non-zero checksum, it MUST be a
correctly computed UDP checksum. Upon receiving such a packet,
the egress endpoint MUST validate the checksum. If the checksum
is not correct, the packet MUST be dropped, otherwise the packet
MUST be accepted for decapsulation. It is RECOMMENDED that the
UDP checksum be computed to protect the Geneve header and options
in situations where the network reliability is not high and the
packet is not protected by another checksum or CRC.
3.4. Tunnel Header Fields
Ver (2 bits): The current version number is 0. Packets received by
an endpoint with an unknown version MUST be dropped. Non-
terminating devices processing 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.
O (1 bit): OAM frame. This packet contains a control message
instead of a data payload. Endpoints MUST NOT forward the payload
and transit devices MUST NOT attempt to interpret or process it.
Since these are infrequent control messages, it is RECOMMENDED
that 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.
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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 devices where option parsing is not
supported the frame 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 frame.
Transit devices MUST NOT drop or modify packets on the basis of
this bit.
Rsvd. (6 bits): Reserved field which MUST be zero on transmission
and 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.
Transit devices MUST maintain consistent forwarding behavior
irrespective of the value of 'Opt Len', including ECMP link
selection. These devices SHOULD be able to forward packets
containing options without resorting to a slow path.
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
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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
implementation may use option types from a variety of sources. In
addition, IANA will be requested to reserve specific ranges for
standardized and experimental options.
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 a separate document.
The high order bit of the option type indicates that this is a
critical option. If the receiving endpoint does not recognize
this option and this bit is set then the frame MUST be dropped.
If the critical 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 critical option
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. MUST be
zero on transmission and 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. Packets in which the total
length of all options is not equal to the 'Opt Len' in the base
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header are invalid and MUST be silently dropped if received by an
endpoint.
Variable Option Data: Option data interpreted according to 'Type'.
3.5.1. Options Processing
Geneve options are intended to be originated and processed by tunnel
endpoints. Options MAY be processed by transit devices along the
tunnel path as well. This document only details the handling of
options by tunnel endpoints. A future version of this document will
provide details of options processing by transit devices. Transit
devices not processing Geneve options SHOULD process Geneve frame as
any other UDP frame and maintain consistent forwarding behavior.
In tunnel endpoints, the generation and interpretation of options is
determined by the control plane, which is out of the scope of this
document. However, to ensure interoperability between heterogeneous
devices two requirements are imposed on endpoint devices:
o Receiving endpoints MUST drop packets containing unknown options
with the 'C' bit set in the option type.
o Sending endpoints MUST NOT assume that options will be processed
sequentially by the receiver in the order they were transmitted.
4. Implementation and Deployment Considerations
4.1. 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.
4.1.1. IP Fragmentation
To prevent fragmentation and maximize performance, the best practice
when using Geneve is to ensure that the MTU of the physical network
is greater than or equal to the MTU of the encapsulated network plus
tunnel headers. Manual or upper layer (such as TCP MSS clamping)
configuration can be used to ensure that fragmentation never takes
place, however, in some situations this may not be feasible.
It is strongly RECOMMENDED that Path MTU Discovery ([RFC1191],
[RFC1981]) be used by setting the DF bit in the IP header when Geneve
packets are transmitted over IPv4 (this is the default with IPv6).
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The use of Path MTU Discovery on the transit network provides the
encapsulating endpoint with soft-state about the link that it may use
to prevent or minimize fragmentation depending on its role in the
virtualized network.
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.
4.1.2. DSCP and ECN
When encapsulating IP (including over Ethernet) frames in Geneve,
there are several options for propagating DSCP and ECN bits from the
inner header to the tunnel on transmission and the reverse on
reception.
[RFC2983] lists considerations 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 SHOULD be followed for IP packets encapsulated in
Geneve.
4.1.3. Broadcast and Multicast
Geneve tunnels may either be point-to-point unicast between two
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,
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encapsulated multicast groups, or some other factor. The allocation
of these groups is a component of the control plane and therefore
outside of the scope of this document. When physical multicast is in
use, the 'C' bit in the Geneve header may be used with groups of
devices with heterogeneous capabilities as each device can interpret
only the options that are significant to it if they are not critical.
4.2. 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. However, a given option definition may
override this rule and specify different behavior in supporting
devices. 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 Option ordering is not significant and packets with the same
options in a different order MAY be processed alike.
o NICs performing offloads MUST NOT drop packets with unknown
options, including those marked as critical.
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.
4.3. 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.
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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
endpoint and/or control plane and not explicitly defined as part of
the data format.
5. Interoperability Issues
Viewed exclusively from the data plane, Geneve does not introduce any
interoperability issues as it appears to most devices as UDP frames.
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 is a superset of the functionality of the three most
common protocols used for network virtualization (VXLAN, NVGRE, and
STT) 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
frame formats supporting the same set of capabilities, there is no
need for a hard transition - endpoints directly communicating with
each other use any common protocol, which may be different even
within a single overall system. As transit devices are primarily
forwarding frames 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 UDP/IP packets, Geneve does not have any inherent security
mechanisms. As a result, an attacker with access to the underlay
network transporting the IP frames has the ability to snoop or inject
packets. Legitimate but malicious tunnel endpoints 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 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
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boundaries. In addition, tunnel endpoints should only be operated in
environments controlled by the service provider, such as the
hypervisor itself rather than within a customer VM.
When crossing an untrusted link, such as the public Internet, IPsec
[RFC4301] may be used to provide authentication and/or encryption of
the IP packets. If the remote tunnel endpoint is not completely
trusted, for example it resides on a customer premises, then it may
also be necessary to sanitize any tunnel metadata to prevent tenant-
hopping attacks.
7. IANA Considerations
IANA has allocated UDP port 6081 as the well-known destination port
for Geneve. Upon publication, the registry should be updated to cite
this document. The original request was:
Service Name: geneve
Transport Protocol(s): UDP
Assignee: Jesse Gross <jgross@vmware.com>
Contact: Jesse Gross <jgross@vmware.com>
Description: Generic Network Virtualization Encapsulation (Geneve)
Reference: This document
Port Number: 6081
In addition, IANA is requested to create a "Geneve Option Class"
registry to allocate Option Classes. This shall be a registry of
16-bit hexadecimal values along with descriptive strings. The
identifiers 0x0-0xFF are to be reserved for standardized options for
allocation by IETF Review [RFC5226] and 0xFFFF for Experimental Use.
Otherwise, identifiers are to be assigned to any organization with an
interest in creating Geneve options on a First Come First Served
basis. There are no initial registry assignments.
8. Acknowledgements
The authors wish to thank Martin Casado, Bruce Davie and Dave Thaler
for their input, feedback, and helpful suggestions.
9. References
9.1. Normative References
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
9.2. Informative References
[ETYPES] The IEEE Registration Authority, "IEEE 802 Numbers", 2013,
<http://www.iana.org/assignments/ieee-802-numbers/
ieee-802-numbers.xml>.
[I-D.davie-stt]
Davie, B. and J. Gross, "A Stateless Transport Tunneling
Protocol for Network Virtualization (STT)", draft-davie-
stt-06 (work in progress), April 2014.
[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.
[I-D.sridharan-virtualization-nvgre]
Sridharan, M., Greenberg, A., Wang, Y., Garg, P.,
Venkataramiah, N., Duda, K., Ganga, I., Lin, G., Pearson,
M., Thaler, P., and C. Tumuluri, "NVGRE: Network
Virtualization using Generic Routing Encapsulation",
draft-sridharan-virtualization-nvgre-06 (work in
progress), October 2014.
[IEEE.802.1Q-2011]
IEEE, "IEEE Standard for Local and metropolitan area
networks -- Media Access Control (MAC) Bridges and Virtual
Bridged Local Area Networks", IEEE Std 802.1Q, 2011.
[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
November 1990.
[RFC1981] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery
for IP version 6", RFC 1981, August 1996.
[RFC2983] Black, D., "Differentiated Services and Tunnels", RFC
2983, October 2000.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, January 2001.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
Gross, et al. Expires April 28, 2015 [Page 21]
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[RFC6040] Briscoe, B., "Tunnelling of Explicit Congestion
Notification", RFC 6040, November 2010.
[RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and
UDP Checksums for Tunneled Packets", RFC 6935, April 2013.
[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, August 2014.
[RFC7365] Lasserre, M., Balus, F., Morin, T., Bitar, N., and Y.
Rekhter, "Framework for Data Center (DC) Network
Virtualization", RFC 7365, October 2014.
[VL2] Greenberg et al, , "VL2: A Scalable and Flexible Data
Center Network", 2009.
Proc. ACM SIGCOMM 2009
Authors' Addresses
Jesse Gross
VMware, Inc.
3401 Hillview Ave.
Palo Alto, CA 94304
USA
Email: jgross@vmware.com
T. Sridhar
VMware, Inc.
3401 Hillview Ave.
Palo Alto, CA 94304
USA
Email: tsridhar@vmware.com
Pankaj Garg
Microsoft Corporation
1 Microsoft Way
Redmond, WA 98052
USA
Email: pankajg@microsoft.com
Gross, et al. Expires April 28, 2015 [Page 22]
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Chris Wright
Red Hat Inc.
1801 Varsity Drive
Raleigh, NC 27606
USA
Email: chrisw@redhat.com
Ilango Ganga
Intel Corporation
2200 Mission College Blvd.
Santa Clara, CA 95054
USA
Email: ilango.s.ganga@intel.com
Puneet Agarwal
Broadcom Corporation
3151 Zanker Road
San Jose, CA 95134
USA
Email: pagarwal@broadcom.com
Kenneth Duda
Arista Networks
5453 Great America Parkway
Santa Clara, CA 95054
USA
Email: kduda@arista.com
Dinesh G. Dutt
Cumulus Networks
140C S. Whisman Road
Mountain View, CA 94041
USA
Email: ddutt@cumulusnetworks.com
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Jon Hudson
Brocade Communications Systems, Inc.
130 Holger Way
San Jose, CA 95134
USA
Email: jon.hudson@gmail.com
Gross, et al. Expires April 28, 2015 [Page 24]
