Internet DRAFT - draft-ietf-bfd-vxlan
draft-ietf-bfd-vxlan
BFD S. Pallagatti, Ed.
Internet-Draft VMware
Intended status: Informational G. Mirsky, Ed.
Expires: April 29, 2021 ZTE Corp.
S. Paragiri
Individual Contributor
V. Govindan
M. Mudigonda
Cisco
October 26, 2020
BFD for VXLAN
draft-ietf-bfd-vxlan-16
Abstract
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.
Status of This Memo
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This Internet-Draft will expire on April 29, 2021.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in this Document . . . . . . . . . . . . . . 3
2.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 4
3. Deployment . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Use of the Management VNI . . . . . . . . . . . . . . . . . . 5
5. BFD Packet Transmission over VXLAN Tunnel . . . . . . . . . . 6
6. Reception of BFD Packet from VXLAN Tunnel . . . . . . . . . . 8
7. Echo BFD . . . . . . . . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9. Security Considerations . . . . . . . . . . . . . . . . . . . 9
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
12.1. Normative References . . . . . . . . . . . . . . . . . . 10
12.2. Informational References . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
"Virtual eXtensible Local Area Network" (VXLAN) [RFC7348] provides an
encapsulation scheme that allows building an overlay network by
decoupling the address space of the attached virtual hosts from that
of the network.
One use of VXLAN is in data centers interconnecting virtual machines
(VMs) of a tenant. VXLAN addresses requirements of the Layer 2 and
Layer 3 data center network infrastructure in the presence of VMs in
a multi-tenant environment by providing a Layer 2 overlay scheme on a
Layer 3 network [RFC7348]. Another use is as an encapsulation for
Ethernet VPN [RFC8365].
This document is written assuming the use of VXLAN for virtualized
hosts and refers to VMs and VXLAN Tunnel End Points (VTEPs) in
hypervisors. However, the concepts are equally applicable to non-
virtualized hosts attached to VTEPs in switches.
In the absence of a router in the overlay, a VM can communicate with
another VM only if they are on the same VXLAN segment. VMs are
unaware of VXLAN tunnels as a VXLAN tunnel is terminated on a VTEP.
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VTEPs are responsible for encapsulating and decapsulating frames
exchanged among VMs.
The ability to monitor path continuity, i.e., perform proactive
continuity check (CC) for point-to-point (p2p) VXLAN tunnels, is
important. The asynchronous mode of BFD, as defined in [RFC5880], is
used to monitor a p2p VXLAN tunnel.
In the case where a Multicast Service Node (MSN) (as described in
Section 3.3 of [RFC8293]) participates in VXLAN, the mechanisms
described in this document apply and can, therefore, be used to test
the continuity of the path between the source NVE and the MSN.
This document describes the use of Bidirectional Forwarding Detection
(BFD) protocol to enable monitoring continuity of the path between
VXLAN VTEPs that are performing as Network Virtualization Endpoints,
and/or between the source NVE and a replicator MSN using a Management
VNI (Section 4). All other uses of the specification to test toward
other VXLAN endpoints are out of the scope.
2. Conventions Used in this Document
2.1. Acronyms
BFD Bidirectional Forwarding Detection
CC Continuity Check
p2p Point-to-point
MSN Multicast Service Node
NVE Network Virtualization Endpoint
VFI Virtual Forwarding Instance
VM Virtual Machine
VNI VXLAN Network Identifier (or VXLAN Segment ID)
VTEP VXLAN Tunnel End Point
VXLAN Virtual eXtensible Local Area Network
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2.2. 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.
3. Deployment
Figure 1 illustrates the scenario with two servers, each of them
hosting two VMs. The servers host VTEPs that terminate two VXLAN
tunnels with VXLAN Network Identifier (VNI) number 100 and 200
respectively. Separate BFD sessions can be established between the
VTEPs (IP1 and IP2) for monitoring each of the VXLAN tunnels (VNI 100
and 200). Using a BFD session to monitor a set of VXLAN VNIs between
the same pair of VTEPs might help to detect and localize problems
caused by misconfiguration. An implementation that supports this
specification MUST be able to control the number of BFD sessions that
can be created between the same pair of VTEPs. This method is
applicable whether the VTEP is a virtual or physical device.
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+------------+-------------+
| Server 1 |
| +----+----+ +----+----+ |
| |VM1-1 | |VM1-2 | |
| |VNI 100 | |VNI 200 | |
| | | | | |
| +---------+ +---------+ |
| VTEP (IP1) |
+--------------------------+
|
| +-------------+
| | Layer 3 |
+---| Network |
+-------------+
|
+-----------+
|
+------------+-------------+
| VTEP (IP2) |
| +----+----+ +----+----+ |
| |VM2-1 | |VM2-2 | |
| |VNI 100 | |VNI 200 | |
| | | | | |
| +---------+ +---------+ |
| Server 2 |
+--------------------------+
Figure 1: Reference VXLAN Domain
At the same time, a service layer BFD session may be used between the
tenants of VTEPs IP1 and IP2 to provide end-to-end fault management
(this use case is outside the scope of this document). In such a
case, for VTEPs, the BFD Control packets of that session are
indistinguishable from data packets.
For BFD Control packets encapsulated in VXLAN (Figure 2), the inner
destination IP address SHOULD be set to one of the loopback addresses
from 127/8 range for IPv4 or to one of IPv4-mapped IPv6 loopback
addresses from ::ffff:127.0.0.0/104 range for IPv6.
4. Use of the Management VNI
In most cases, a single BFD session is sufficient for the given VTEP
to monitor the reachability of a remote VTEP, regardless of the
number of VNIs. BFD control messages MUST be sent using the
Management VNI which acts as the as control and management channel
between VTEPs. An implementation MAY support operating BFD on
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another (non-Management) VNI although the implications of this are
outside the scope of this document. The selection of the VNI number
of the Management VNI MUST be controlled through a management plane.
An implementation MAY use VNI number 1 as the default value for the
Management VNI. All VXLAN packets received on the Management VNI
MUST be processed locally and MUST NOT be forwarded to a tenant.
5. BFD Packet Transmission over VXLAN Tunnel
BFD packets MUST be encapsulated and sent to a remote VTEP as
explained in this section. Implementations SHOULD ensure that the
BFD packets follow the same forwarding path as VXLAN data packets
within the sender system.
BFD packets are encapsulated in VXLAN as described below. The VXLAN
packet format is defined in Section 5 of [RFC7348]. The value in the
VNI field of the VXLAN header MUST be set to the value selected as
the Management VNI. The Outer IP/UDP and VXLAN headers MUST be
encoded by the sender as defined in [RFC7348].
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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 IPvX Header ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Outer UDP Header ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ VXLAN Header ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Inner Ethernet Header ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Inner IPvX Header ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Inner UDP Header ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ BFD Control Packet ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Outer Ethernet FCS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: VXLAN Encapsulation of BFD Control Packet
The BFD packet MUST be carried inside the inner Ethernet frame of the
VXLAN packet. The choice of Destination MAC and Destination IP
addresses for the inner Ethernet frame MUST ensure that the BFD
Control packet is not forwarded to a tenant but is processed locally
at the remote VTEP. The inner Ethernet frame carrying the BFD
Control packet- has the following format:
Ethernet Header:
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Destination MAC: A Management VNI, which does not have any
tenants, will have no dedicated MAC address for decapsulated
traffic. The value (TBD1) SHOULD be used in this field.
Source MAC: MAC address associated with the originating VTEP.
Ethertype: is set to 0x0800 if the inner IP header is IPv4, and
is set to 0x86DD if the inner IP header is IPv6.
IP header:
Destination IP: IP address MUST NOT be of one of tenant's IP
addresses. The IP address SHOULD be selected from the range
127/8 for IPv4, for IPv6 - from the range ::ffff:127.0.0.0/104.
Alternatively, the destination IP address MAY be set to VTEP's
IP address.
Source IP: IP address of the originating VTEP.
TTL or Hop Limit: MUST be set to 255 in accordance with
[RFC5881].
The fields of the UDP header and the BFD Control packet are
encoded as specified in [RFC5881].
6. Reception of BFD Packet from VXLAN Tunnel
Once a packet is received, the VTEP MUST validate the packet. If the
packet is received on the management VNI and is identified as BFD
control packet addressed to the VTEP, and then the packet can be
processed further. Processing of BFD control packets received on
non-management VNI is outside the scope of this specification.
The received packet's inner IP payload is then validated according to
Sections 4 and 5 in [RFC5881].
7. Echo BFD
Support for echo BFD is outside the scope of this document.
8. IANA Considerations
IANA is requested to assign a single MAC address to the value TBD1
from the "IANA Unicast 48-bit MAC Address" registry from the
"Unassigned (small allocations)" block. The Usage field will be "BFD
for VXLAN" with a Reference field of this document.
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9. Security Considerations
Security issues discussed in [RFC5880], [RFC5881], and [RFC7348]
apply to this document.
This document recommends using an address from the Internal host
loopback addresses 127/8 range for IPv4 or an IP4-mapped IPv6
loopback address from ::ffff:127.0.0.0/104 range for IPv6 as the
destination IP address in the inner IP header. Using such an address
prevents the forwarding of the encapsulated BFD control message by a
transient node in case the VXLAN tunnel is broken as according to
[RFC1812].
A router SHOULD NOT forward, except over a loopback interface, any
packet that has a destination address on network 127. A router
MAY have a switch that allows the network manager to disable these
checks. If such a switch is provided, it MUST default to
performing the checks.
The use of IPv4-mapped IPv6 addresses has the same property as using
the IPv4 network 127/8, moreover, the IPv4-mapped IPv6 addresses
prefix is not advertised in any routing protocol.
If the implementation supports establishing multiple BFD sessions
between the same pair of VTEPs, there SHOULD be a mechanism to
control the maximum number of such sessions that can be active at the
same time.
10. Contributors
Reshad Rahman
rrahman@cisco.com
Cisco
11. Acknowledgments
Authors would like to thank Jeff Haas of Juniper Networks for his
reviews and feedback on this material.
Authors would also like to thank Nobo Akiya, Marc Binderberger,
Shahram Davari, Donald E. Eastlake 3rd, Anoop Ghanwani, Dinesh Dutt,
Joel Halpern, and Carlos Pignataro for the extensive reviews and the
most detailed and constructive comments.
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12. References
12.1. Normative References
[RFC1812] Baker, F., Ed., "Requirements for IP Version 4 Routers",
RFC 1812, DOI 10.17487/RFC1812, June 1995,
<https://www.rfc-editor.org/info/rfc1812>.
[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>.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<https://www.rfc-editor.org/info/rfc5880>.
[RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881,
DOI 10.17487/RFC5881, June 2010,
<https://www.rfc-editor.org/info/rfc5881>.
[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>.
[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>.
12.2. Informational References
[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>.
[RFC8365] Sajassi, A., Ed., Drake, J., Ed., Bitar, N., Shekhar, R.,
Uttaro, J., and W. Henderickx, "A Network Virtualization
Overlay Solution Using Ethernet VPN (EVPN)", RFC 8365,
DOI 10.17487/RFC8365, March 2018,
<https://www.rfc-editor.org/info/rfc8365>.
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Authors' Addresses
Santosh Pallagatti (editor)
VMware
Email: santosh.pallagatti@gmail.com
Greg Mirsky (editor)
ZTE Corp.
Email: gregimirsky@gmail.com
Sudarsan Paragiri
Individual Contributor
Email: sudarsan.225@gmail.com
Vengada Prasad Govindan
Cisco
Email: venggovi@cisco.com
Mallik Mudigonda
Cisco
Email: mmudigon@cisco.com
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