Hi Oliver,
thank you for your thorough review, clear and detailed questions. My apologies for the delay to respond. Please find my answers below in-line tagged GIM>>.
Regards,
Greg
On Fri, May 31, 2019 at 12:38 PM Olivier Bonaventure via Datatracker <noreply@xxxxxxxx> wrote:
Reviewer: Olivier Bonaventure
Review result: Ready with Issues
This document has been reviewed as part of the transport area review team's
ongoing effort to review key IETF documents. These comments were written
primarily for the transport area directors, but are copied to the document's
authors and WG to allow them to address any issues raised and also to the IETF
discussion list for information.
When done at the time of IETF Last Call, the authors should consider this
review as part of the last-call comments they receive. Please always CC
tsv-art@xxxxxxxx if you reply to or forward this review.
I have only limited knowledge of VXLAN and do not know all subtleties of BFD.
This review is thus more from a generalist than a specialist in this topic.
Major issues
Section 4 requires that " Implementations SHOULD ensure that the BFD
packets follow the same lookup path as VXLAN data packets within the
sender system."
Why is this requirement only relevant for the lookup path on the sender system
? What does this sentence really implies ?
GIM>> RFC 5880 set the scope of the fault detection of BFD protocol as
... the bidirectional path between two forwarding engines, includinginterfaces, data link(s), and to the extent possible the forwarding
engines themselves ...
The requirement aimed to the forwarding engine of a BFD system that transmits BFD control packets over VXLAN tunnel.
Is it a requirement that the BFD packets follow the same path as the data
packet for a given VXLAN ? I guess so. In this case, the document should
discuss how Equal Cost Multipath could affect this.
GIM>> I think that ECMP environment is more likely to be experienced by a transit node in the underlay. If the BFD session is used to monitor the specific underlay path, then, I agree, we should explain that using the VXLAN payload information to draw path entropy may cause data and BFD packets following different underlay routes. But, on the other hand, that is the case for OAM and fault detection in all overlay networks in general.
Minor issues
Section 1
You write "The asynchronous mode of BFD, as defined in [RFC5880],
can be used to monitor a p2p VXLAN tunnel."
Why do you use the word can ? It is a possibility or a requirement ?
GIM>> In principle, BFD Demand mode may be used to monitor p2p paths as well, I agree, will re-word to more assertive:
The asynchronous mode of BFD, as defined in [RFC5880],
is used to monitor a p2p VXLAN tunnel.
NVE has not been defined before and is not in the terminology.
GIM>> Will add to the Terminology and expand as:
NVE Network Virtualization Endpoint
This entire section is not easy to read for an outsider.
Section 3
VNI has not been defined
GIM>> Will add to the Terminology section:
VNI VXLAN Network Identifier (or VXLAN Segment ID)
Figure 1 could take less space
GIM>> Yes, can make it bit denser. Would the following be an improvement?
+------------+-------------+
| Server 1 |
| +----+----+ +----+----+ |
| |VM1-1 | |VM1-2 | |
| |VNI 100 | |VNI 200 | |
| | | | | |
| +---------+ +---------+ |
| Hypervisor VTEP (IP1) |
+--------------------------+
|
| +-------------+
| | Layer 3 |
+---| Network |
+-------------+
|
+-----------+
|
+------------+-------------+
| Hypervisor VTEP (IP2) |
| +----+----+ +----+----+ |
| |VM2-1 | |VM2-2 | |
| |VNI 100 | |VNI 200 | |
| | | | | |
| +---------+ +---------+ |
| Server 2 |
+--------------------------+
Section 4
I do not see the benefits of having one paragraph in Section 4 followed by only
Section 4.1
GIM>> Will merge Section 4.1 into 4 with minor required re-wording:
4. BFD Packet Transmission over VXLAN Tunnel
BFD packet MUST be encapsulated and sent to a remote VTEP as
explained in this section. Implementations SHOULD ensure that the
BFD packets follow the same lookup 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 Outer IP/UDP
and VXLAN headers MUST be encoded by the sender as defined in
[RFC7348].
BFD packet MUST be encapsulated and sent to a remote VTEP as
explained in this section. Implementations SHOULD ensure that the
BFD packets follow the same lookup 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 Outer IP/UDP
and VXLAN headers MUST be encoded by the sender as defined in
[RFC7348].
Section 4.1
The document does not specify when a dedicated MAC address or the MAC address
of the destination VTEP must be used. This could affect the interoperability of
implementations. Should all implementations support both the dedicated MAC
address and the destination MAC address ?
GIM>> After further discussion, authors decided to remove the request for the dedicated MAC address allocation. Only the MAC address of the remote VTEP must be used as the destination MAC address in the inner Ethernet frame. Please check the attached diff between the -07 and the working versions or the working version of the draft.
It is unclear from this section whether IPv4 inside IPv6 and the opposite
should be supported or not.
GIM>> Any combination of outer IPvX and inner IPvX is possible.
Section 5.
If the received packet does not match the dedicated MAC address nor the MAC
address of the VTEP, should the packet be silently discarded or treated
differently ?
GIM>> As I've mentioned earlier, authors have decided to remove the use of the dedicated MAC address for BFD over VXLAN.
Section 5.1
Is this a modification to section 6.3 of RFC5880 ? This is not clear
GIM>> I think that this section is not modification but the definition of the application-specific procedure that is outside the scope of RFC 5880:
The method of demultiplexing the initial packets (in which Your
Discriminator is zero) is application dependent, and is thus outside
the scope of this specification.
Discriminator is zero) is application dependent, and is thus outside
the scope of this specification.
Section 9
The sentence " Throttling MAY be relaxed for BFD packets
based on port number." is unclear.
GIM>> Yes, thank you for pointing to this. The updated text, in the whole paragraph, is as follows:
NEW TEXT:
The document requires setting the inner IP TTL to 1, which could be
used as a DDoS attack vector. Thus the implementation MUST have
throttling in place to control the rate of BFD control packets sent
to the control plane. On the other hand, over aggressive throttling
of BFD control packets may become the cause of the inability to form
and maintain BFD session at scale. Hence, throttling of BFD control
packets SHOULD be adjusted to permit BFD to work according to its
procedures.
used as a DDoS attack vector. Thus the implementation MUST have
throttling in place to control the rate of BFD control packets sent
to the control plane. On the other hand, over aggressive throttling
of BFD control packets may become the cause of the inability to form
and maintain BFD session at scale. Hence, throttling of BFD control
packets SHOULD be adjusted to permit BFD to work according to its
procedures.
BFD S. Pallagatti, Ed.
Internet-Draft Rtbrick
Intended status: Standards Track S. Paragiri
Expires: December 18, 2019 Individual Contributor
V. Govindan
M. Mudigonda
Cisco
G. Mirsky
ZTE Corp.
June 16, 2019
BFD for VXLAN
draft-ietf-bfd-vxlan-08
Abstract
This document describes the use of the Bidirectional Forwarding
Detection (BFD) protocol in point-to-point Virtual eXtensible Local
Area Network (VXLAN) tunnels forming up an overlay network.
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 https://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
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 December 18, 2019.
Copyright Notice
Copyright (c) 2019 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
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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to this document. Code Components extracted from this document must
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 . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. Deployment . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. BFD Packet Transmission over VXLAN Tunnel . . . . . . . . . . 5
5. Reception of BFD Packet from VXLAN Tunnel . . . . . . . . . . 7
5.1. Demultiplexing of the BFD Packet . . . . . . . . . . . . 7
6. Use of the Specific VNI . . . . . . . . . . . . . . . . . . . 8
7. Echo BFD . . . . . . . . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9. Security Considerations . . . . . . . . . . . . . . . . . . . 8
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
12.1. Normative References . . . . . . . . . . . . . . . . . . 9
12.2. Informational References . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
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.
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]) resides behind an Network Virtualization
Endpoint (NVE), the mechanisms described in this document apply and
can, therefore, be used to test the connectivity from the source NVE
to the MSN.
This document describes the use of Bidirectional Forwarding Detection
(BFD) protocol to enable monitoring continuity of the path between
VXLAN VTEPs, performing as Network Virtualization Endpoints, and/or
availability of a replicator multicast service node.
2. Conventions used in this document
2.1. Terminology
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
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
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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). 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. BFD packets intended for a
Hypervisor VTEP MUST NOT be forwarded to a VM as a VM may drop BFD
packets leading to a false negative. This method is applicable
whether the VTEP is a virtual or physical device.
+------------+-------------+
| Server 1 |
| +----+----+ +----+----+ |
| |VM1-1 | |VM1-2 | |
| |VNI 100 | |VNI 200 | |
| | | | | |
| +---------+ +---------+ |
| Hypervisor VTEP (IP1) |
+--------------------------+
|
| +-------------+
| | Layer 3 |
+---| Network |
+-------------+
|
+-----------+
|
+------------+-------------+
| Hypervisor VTEP (IP2) |
| +----+----+ +----+----+ |
| |VM2-1 | |VM2-2 | |
| |VNI 100 | |VNI 200 | |
| | | | | |
| +---------+ +---------+ |
| Server 2 |
+--------------------------+
Figure 1: Reference VXLAN Domain
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4. BFD Packet Transmission over VXLAN Tunnel
BFD packet MUST be encapsulated and sent to a remote VTEP as
explained in this section. Implementations SHOULD ensure that the
BFD packets follow the same lookup 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 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 Message ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FCS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: VXLAN Encapsulation of BFD Control Message
The BFD packet MUST be carried inside the inner MAC frame of the
VXLAN packet. The inner MAC frame carrying the BFD payload has the
following format:
Ethernet Header:
Destination MAC: This MUST be the MAC address of the
destination VTEP. The MAC address MAY be configured or it MAY
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be learned via a control plane protocol. The details of how
the MAC address of the destination VTEP is obtained are outside
the scope of this document.
Source MAC: MAC address of the originating VTEP
IP header:
Source IP: IP address of the originating VTEP.
Destination IP: IP address of the terminating VTEP.
TTL: MUST be set to 1 to ensure that the BFD packet is not
routed within the L3 underlay network.
The fields of the UDP header and the BFD control packet are
encoded as specified in [RFC5881].
5. Reception of BFD Packet from VXLAN Tunnel
Once a packet is received, VTEP MUST validate the packet. If the
Destination MAC of the inner MAC frame matches the MAC address of the
VTEP the packet MUST be processed further.
The UDP destination port and the TTL of the inner IP packet MUST be
validated to determine if the received packet can be processed by
BFD. BFD packet with inner MAC set to VTEP's MAC address MUST NOT be
forwarded to VMs.
5.1. Demultiplexing of the BFD Packet
Demultiplexing of IP BFD packet has been defined in Section 3 of
[RFC5881]. Since multiple BFD sessions may be running between two
VTEPs, there needs to be a mechanism for demultiplexing received BFD
packets to the proper session. The procedure for demultiplexing
packets with Your Discriminator equal to 0 is different from
[RFC5880]. For such packets, the BFD session MUST be identified
using the inner headers, i.e., the source IP, the destination IP, and
the source UDP port number present in the IP header carried by the
payload of the VXLAN encapsulated packet. The VNI of the packet
SHOULD be used to derive interface-related information for
demultiplexing the packet. If BFD packet is received with non-zero
Your Discriminator, then BFD session MUST be demultiplexed only with
Your Discriminator as the key.
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6. Use of the Specific 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 in common. When the single BFD session is used to
monitor the reachability of the remote VTEP, an implementation SHOULD
choose any of the VNIs but MAY choose VNI = 0.
7. Echo BFD
Support for echo BFD is outside the scope of this document.
8. IANA Considerations
This specification has no IANA action requested. This section may be
deleted before the publication.
9. Security Considerations
The document requires setting the inner IP TTL to 1, which could be
used as a DDoS attack vector. Thus the implementation MUST have
throttling in place to control the rate of BFD control packets sent
to the control plane. On the other hand, over aggressive throttling
of BFD control packets may become the cause of the inability to form
and maintain BFD session at scale. Hence, throttling of BFD control
packets SHOULD be adjusted to permit BFD to work according to its
procedures.
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 session that can be active at the
same time.
Other than inner IP TTL set to 1 and limit the number of BFD sessions
between the same pair of VTEPs, this specification does not raise any
additional security issues beyond those of the specifications
referred to in the list of normative references.
10. Contributors
Reshad Rahman
rrahman@xxxxxxxxx
Cisco
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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, and Anoop Ghanwani for the
extensive reviews and the most detailed and helpful comments.
12. References
12.1. Normative References
[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>.
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[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>.
Authors' Addresses
Santosh Pallagatti (editor)
Rtbrick
Email: santosh.pallagatti@xxxxxxxxx
Sudarsan Paragiri
Individual Contributor
Email: sudarsan.225@xxxxxxxxx
Vengada Prasad Govindan
Cisco
Email: venggovi@xxxxxxxxx
Mallik Mudigonda
Cisco
Email: mmudigon@xxxxxxxxx
Greg Mirsky
ZTE Corp.
Email: gregimirsky@xxxxxxxxx
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