Bidirectional Forwarding Detection (BFD) for Generic Network Virtualization Encapsulation (Geneve)ZTE Corp.NanjingChina+86 18061680168xiao.min2@zte.com.cnEricssonUnited States of Americagregimirsky@gmail.comVMwareIndiasantosh.pallagatti@gmail.comNvidiaUnited States of Americajefftant.ietf@gmail.comGoogleUnited States of Americaaldrin.ietf@gmail.com
rtg
nvo3 This document describes the use of the Bidirectional Forwarding Detection (BFD) protocol in point-to-point
Generic Network Virtualization Encapsulation (Geneve) unicast tunnels used to make up an overlay network. Status of This Memo
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Table of Contents
. Introduction
. Conventions Used in This Document
. Abbreviations
. Requirements Language
. BFD Packet Transmission over a Geneve Tunnel
. BFD Encapsulation with the Inner Ethernet/IP/UDP Header
. Demultiplexing a BFD Packet When the Payload Is Ethernet
. BFD Encapsulation with the Inner IP/UDP Header
. Demultiplexing a BFD Packet When the Payload Is IP
. Security Considerations
. IANA Considerations
. References
. Normative References
. Informative References
Acknowledgements
Authors' Addresses
Introduction"Geneve: Generic Network Virtualization Encapsulation" provides an encapsulation scheme
that allows building an overlay network of tunnels by decoupling the address space of the attached virtual hosts from
that of the network. This document describes the use of the Bidirectional Forwarding Detection (BFD) protocol
to enable monitoring the continuity of the path between two Geneve tunnel endpoints, which may be a Network
Virtualization Edge (NVE) or another device acting as a Geneve tunnel endpoint. Specifically, the asynchronous mode of BFD,
as defined in , is used to monitor a point-to-point (P2P) Geneve tunnel. The support for the BFD Echo function is outside
the scope of this document. For simplicity, an NVE is used to represent the Geneve tunnel endpoint.
A Tenant System (TS) is used to represent the physical or virtual device attached to a Geneve tunnel endpoint from the
outside. A Virtual Access Point (VAP) is the NVE side of the interface between the NVE and the TS, and a VAP is a
logical network port (virtual or physical) into a specific virtual network. For detailed definitions and descriptions
of NVE, TS, and VAP, please refer to and . The use cases and the deployment of BFD for Geneve are mostly
consistent with what's described in Sections and of . One exception is the
usage of the Management Virtual Network Identifier (VNI), which is described in and is outside the scope of this
document. As specified in , Geneve MUST be used with
congestion controlled traffic or within a Traffic-Managed Controlled
Environment (TMCE) to avoid congestion; that requirement also applies to BFD
traffic. Specifically, considering the complexity and immaturity of
the BFD congestion control mechanism, BFD for Geneve MUST
be used within a TMCE unless BFD is really congestion controlled. As an
alternative to a real congestion control, an operator of a TMCE
deploying BFD for Geneve is required to provision the rates at which BFD
is transmitted to avoid congestion and false failure detection. Conventions Used in This DocumentAbbreviations
BFD:
Bidirectional Forwarding Detection
FCS:
Frame Check Sequence
Geneve:
Generic Network Virtualization Encapsulation
NVE:
Network Virtualization Edge
TMCE:
Traffic-Managed Controlled Environment
TS:
Tenant System
VAP:
Virtual Access Point
VNI:
Virtual Network Identifier
VXLAN:
Virtual eXtensible Local Area Network
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 when, and only when, they appear in all capitals,
as shown here.
BFD Packet Transmission over a Geneve Tunnel Since the Geneve data packet payload may be either an Ethernet frame
or an IP packet, this document defines two formats of BFD packet
encapsulation in Geneve. The BFD session is originated and terminated at
the VAP of an NVE. The selection of the BFD packet encapsulation is
based on how the VAP encapsulates the data packets. If the payload is
IP, then BFD over IP is carried in the payload. If the payload is
Ethernet, then BFD over IP over Ethernet is carried in the payload. This occurs in
the same manner as BFD over IP in the IP payload case, regardless of
what the Ethernet payload might normally carry.BFD Encapsulation with the Inner Ethernet/IP/UDP Header If the VAP that originates the BFD packets is used to encapsulate
Ethernet data frames, then the BFD packets are encapsulated in Geneve as
described below. The Geneve packet formats over IPv4 and IPv6 are
defined in Sections
and of , respectively. The outer IP/UDP and Geneve headers are
encoded by the sender as defined in . Note that
the outer IP header and the inner IP header may not be of the same
address family. In other words, an outer IPv6 header accompanied by an
inner IPv4 header and an outer IPv4 header accompanied by an inner IPv6
header are both possible. Geneve Encapsulation of a BFD Control Packet with the Inner Ethernet/IP/UDP Header
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 IPvX Header ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Outer UDP Header ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Geneve Header ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Inner Ethernet Header ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Inner IPvX Header ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Inner UDP Header ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ BFD Control Packet ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Outer Ethernet FCS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The BFD packet MUST be carried inside the inner Ethernet frame of the Geneve packet.
The inner Ethernet frame carrying the BFD Control packet has the following format:
Inner Ethernet Header:
Destination MAC:
Media Access Control (MAC) address of a VAP of the terminating NVE.
Source MAC:
MAC address of a VAP of the originating NVE.
IP Header:
Source IP:
IP address of a VAP of the originating
NVE. If the VAP of the originating NVE has no IP address, then the
IP address 0.0.0.0 for IPv4 or ::/128 for IPv6 MUST
be used.
Destination IP:
IP address of a VAP of the terminating
NVE. If the VAP of the terminating NVE has no IP address, then the
IP address 127.0.0.1 for IPv4 or ::1/128 for IPv6
MUST be used.
TTL or Hop Limit:
The TTL for IPv4 or Hop Limit for IPv6 MUST be set to 255 in
accordance with , which specifies the
IPv4/IPv6 single-hop BFD.
The fields of the UDP header and the BFD Control packet are
encoded as specified in .
When the BFD packets are encapsulated in Geneve in this way, the
Geneve header defined in follows the value
set below.
The Opt Len field MUST be set as consistent with the Geneve specification () depending on whether
or not Geneve options are present in the frame. The use of Geneve options with BFD is beyond the scope of this document.
The O bit MUST be set to 1, which indicates this packet contains a control message.
The C bit MUST be set to 0, which indicates there isn't any critical option.
The Protocol Type field MUST be set to 0x6558 (Ethernet frame).
The Virtual Network Identifier (VNI) field MUST be set to the VNI number that the originating VAP is mapped to.
Demultiplexing a BFD Packet When the Payload Is Ethernet Once a packet is received, the NVE validates the packet as
described in . When the payload is Ethernet,
the Protocol Type field equals 0x6558. The destination MAC address of
the inner Ethernet frame matches the MAC address of a VAP, which is
mapped to the same VNI as the received VNI. Then, the destination IP,
the UDP destination port, and the TTL or Hop Limit of the inner IP
packet MUST be validated to determine whether
the received packet can be processed by BFD (i.e., the three field
values of the inner IP packet MUST be in compliance
with what's defined in of
this document, as well as ). If the validation fails, the received packet
MUST NOT be processed by BFD. In BFD over Geneve, a BFD session is originated and terminated at
a VAP. Usually one NVE owns multiple VAPs. Since multiple BFD sessions
may be running between two NVEs, there needs to be a mechanism for
demultiplexing received BFD packets to the proper
session. Furthermore, due to the fact that
allows for N-to-1 mapping between VAPs and VNIs at one NVE, multiple BFD
sessions between two NVEs for the same VNI are allowed. Also, note that
a BFD session can only be established between two VAPs that are mapped
to the same VNI and that use the same way to encapsulate data packets. If the BFD packet is received with the value of the Your Discriminator field set to 0, then the BFD session SHOULD be identified using
the VNI number and the inner Ethernet/IP header. The inner Ethernet/IP header stands for the source MAC, the source IP,
the destination MAC, and the destination IP. An implementation MAY use the inner UDP port source number to aid in
demultiplexing incoming BFD Control packets. If it fails to identify the BFD session, the incoming BFD Control packets
MUST be dropped, and an exception event indicating the failure should be reported to the management. If the BFD packet is received with a non-zero Your Discriminator,
then the BFD session MUST be demultiplexed only with
the Your Discriminator as the key. BFD Encapsulation with the Inner IP/UDP Header If the VAP that originates the BFD packets is used to encapsulate IP
data packets, then the BFD packets are encapsulated in Geneve as
described below. The Geneve packet formats over IPv4 and IPv6 are
defined in Sections and of ,
respectively. The outer IP/UDP and Geneve headers are encoded by the
sender as defined in . Note that the outer IP
header and the inner IP header may not be of the same address family. In
other words, an outer IPv6 header accompanied by an inner IPv4 header
and an outer IPv4 header accompanied by an inner IPv6 header are both
possible. Geneve Encapsulation of a BFD Control Packet with the Inner IP/UDP Header
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Ethernet Header ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Outer IPvX Header ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Outer UDP Header ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Geneve Header ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Inner IPvX Header ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Inner UDP Header ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ BFD Control Packet ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FCS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The BFD packet MUST be carried inside the inner IP packet of the Geneve packet.
The inner IP packet carrying the BFD Control packet has the following format:
Inner IP Header:
Source IP:
IP address of a VAP of the originating NVE.
Destination IP:
IP address of a VAP of the terminating NVE.
TTL or Hop Limit:
The TTL for IPv4 or Hop Limit for IPv6 MUST be set to 255 in accordance with , which specifies the IPv4/IPv6 single-hop BFD.
The fields of the UDP header and the BFD Control packet are encoded as specified in .
When the BFD packets are encapsulated in Geneve in this way, the Geneve header defined in
follows the value set below.
The Opt Len field MUST be set as consistent with the Geneve specification () depending on whether
or not Geneve options are present in the frame. The use of Geneve options with BFD is beyond the scope of this document.
The O bit MUST be set to 1, which indicates this packet contains a control message.
The C bit MUST be set to 0, which indicates there isn't any critical option.
The Protocol Type field MUST be set to 0x0800 (IPv4) or 0x86DD (IPv6), depending on the address family
of the inner IP packet.
The Virtual Network Identifier (VNI) field MUST be set to the VNI number that the originating VAP is mapped to.
Demultiplexing a BFD Packet When the Payload Is IP Once a packet is received, the NVE validates the packet as
described in . When the payload is IP, the
Protocol Type field equals 0x0800 or 0x86DD. The destination IP
address of the inner IP packet matches the IP address of a VAP, which
is mapped to the same VNI as the received VNI. Then, the UDP
destination port and the TTL or Hop Limit of the inner IP packet
MUST be validated to determine whether or not the received
packet can be processed by BFD (i.e., the two field values of the
inner IP packet MUST be in compliance with what's
defined in of
this document as well as ). If the validation fails, the received packet
MUST NOT be processed by BFD. If the BFD packet is received with the value of the Your Discriminator field set to 0, then the BFD session SHOULD be identified using the VNI
number and the inner IP header. The inner IP header stands for the source IP and the destination IP. An implementation MAY
use the inner UDP port source number to aid in demultiplexing incoming BFD Control packets. If it fails to identify the BFD session,
the incoming BFD Control packets MUST be dropped, and an exception event indicating the failure should be reported to the management. If the BFD packet is received with a non-zero Your Discriminator, then the BFD session MUST be demultiplexed
only with the Your Discriminator as the key. Security Considerations Security issues discussed in and apply to this document. Particularly,
the BFD is an application that is run at the two Geneve tunnel endpoints. The IP underlay network and/or the Geneve option
can provide security between the peers, which are subject to the issue of overload described below. The BFD introduces no
security vulnerabilities when run in this manner. Considering Geneve does not have any inherent security mechanisms, BFD
authentication as specified in is RECOMMENDED to be utilized.
This document supports establishing multiple BFD sessions between the
same pair of NVEs. For each BFD session over a pair of VAPs residing
in the same pair of NVEs, there SHOULD be a mechanism to control the
maximum number of such sessions that can be active at the same time.
Particularly, assuming an example that each NVE of the pair
of NVEs has N VAPs using Ethernet as the payload, then there could be N
squared BFD sessions running between the pair of NVEs. Considering N
could be a high number, the N squared BFD sessions could result in
overload of the NVE. In this case, it's recommended that N BFD sessions
covering all N VAPs are run for the pair of NVEs. Generally speaking,
the number of BFD sessions is supposed to be enough as long as all VAPs
of the pair of NVEs are covered.IANA ConsiderationsThis document has no IANA actions.ReferencesNormative ReferencesKey words for use in RFCs to Indicate Requirement LevelsIn many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.Bidirectional Forwarding Detection (BFD)This document describes a protocol intended to detect faults in the bidirectional path between two forwarding engines, including interfaces, data link(s), and to the extent possible the forwarding engines themselves, with potentially very low latency. It operates independently of media, data protocols, and routing protocols. [STANDARDS-TRACK]Bidirectional Forwarding Detection (BFD) for IPv4 and IPv6 (Single Hop)This document describes the use of the Bidirectional Forwarding Detection (BFD) protocol over IPv4 and IPv6 for single IP hops. [STANDARDS-TRACK]Ambiguity of Uppercase vs Lowercase in RFC 2119 Key WordsRFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.Geneve: Generic Network Virtualization EncapsulationNetwork 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 of the system, the requirements on tunnels are influenced by all of these components. Therefore, flexibility is the most important aspect of a tunneling protocol if it is to keep pace with the evolution of technology. This document describes Geneve, an encapsulation protocol designed to recognize and accommodate these changing capabilities and needs.Informative ReferencesOAM for use in GENEVEEricssonCienaDell EMCVMwareWork in ProgressFramework for Data Center (DC) Network VirtualizationThis document provides a framework for Data Center (DC) Network Virtualization over Layer 3 (NVO3) and defines a reference model along with logical components required to design a solution.An Architecture for Data-Center Network Virtualization over Layer 3 (NVO3)This document presents a high-level overview architecture for building data-center Network Virtualization over Layer 3 (NVO3) networks. The architecture is given at a high level, showing the major components of an overall system. An important goal is to divide the space into individual smaller components that can be implemented independently with clear inter-component interfaces and interactions. It should be possible to build and implement individual components in isolation and have them interoperate with other independently implemented components. That way, implementers have flexibility in implementing individual components and can optimize and innovate within their respective components without requiring changes to other components.Bidirectional Forwarding Detection (BFD) for Virtual eXtensible Local Area Network (VXLAN)This document describes the use of the Bidirectional Forwarding Detection (BFD) protocol in point-to-point Virtual eXtensible Local Area Network (VXLAN) tunnels used to form an overlay network.Acknowledgements The authors would like to acknowledge , , and for their guidance on this work. The authors would like to acknowledge
for his explanation on the mapping relation between VAPs and VNIs. The authors would like to acknowledge , , , , , , , , , , , , , ,
, and for
their thorough review and very helpful comments.Authors' AddressesZTE Corp.NanjingChina+86 18061680168xiao.min2@zte.com.cnEricssonUnited States of Americagregimirsky@gmail.comVMwareIndiasantosh.pallagatti@gmail.comNvidiaUnited States of Americajefftant.ietf@gmail.comGoogleUnited States of Americaaldrin.ietf@gmail.com