NVO3 Working Group G. Mirsky
Internet-Draft X. Min
Intended status: Standards Track ZTE Corp.
Expires: September 10, 2020 S. Boutros
D. Black
Dell EMC
S. Pallagatti, Ed.
March 9, 2020

OAM for use in GENEVE


This document defines encapsulation for active Operations, Administration, and Maintenance protocols in Geneve protocol. Also, the format and operation of the Echo Request and Echo Reply mechanism in Geneve are defined.

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Table of Contents

1. Introduction

Geneve [I-D.ietf-nvo3-geneve] is intended to support various scenarios of network virtualization. In addition to carrying multi-protocol payload, e.g., Ethernet, IPv4/IPv6, the Geneve message includes metadata. Operations, Administration, and Maintenance (OAM) protocols support fault management and performance monitoring functions necessary for comprehensive network operation. Active OAM protocols, as defined in [RFC7799], use specially constructed packets, that are injected into the network. To ensure that the measured performance metric or the detected failure of the transport layer are related to the particular Geneve flow, it is critical that these test packets share fate with overlay data packets when traversing the underlay network.

This document describes several options for encapsulation of active OAM protocols in Geneve. These are intended to facilitate the discussion among experts and all interested in both OAM and Geneve subjects. The goal of such analysis is the selection of a practical number of encapsulation methods and providing definitions of any introduced constructs.

Also, a set of generic requirements for active OAM protocols in Geneve overlay network introduced in this document. These should be used in selecting the most suitable encapsulation for active OAM in Geneve.

1.1. Conventions used in this document

1.1.1. Terminology

CC Continuity Check

CV Connectivity Verification

FM Fault Management

GAL Generic Associated Channel Label

Geneve Generic Network Virtualization Encapsulation

NVO3 Network Virtualization Overlays

OAM Operations, Administration, and Maintenance

ACC Associated Control Channel

1.1.2. 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.

2. Active OAM Protocols in Geneve Networks

OAM protocols, whether it is part of fault management or performance monitoring, intended to provide reliable information that can be used to detect a failure, identify the defect, localize it, thus helping to apply corrective actions to minimize the negative impact on service. Several OAM protocols will be used to perform these functions, protocols that require demultiplexing at the receiving instance of Geneve. To improve the accuracy of the correlation between the condition experienced by the monitored Geneve tunnel and the state of the OAM protocol the OAM encapsulation is required to comply with the following requirements:

2.1. A Control Channel in the Geneve Network

There's a need for a general control channel between Geneve tunnel endpoints for OAM protocols that can be used for fault detection, diagnostics, maintenance, and other functions. Such a control tunnel is dedicated to carrying only control and management data between tunnel endpoints. Thus, the control channel of a Geneve tunnel SHOULD NOT carry tenant data. As no tenants are connected using the control channel, a system that supports this specification, SHOULD NOT forward a packet received over the control channel. Virtual Network Identifier (VNI) is used to identify the control channel. The value that is associated with this function is referred to as Management VNI. It is RECOMMENDED that the value 1 be used as the default value of Management VNI.

2.2. OAM Encapsulation in Geneve

One of the options is to use IP/UDP encapsulation for active OAM. In this case, OAM protocols are identified by the destination UDP port number. This approach is well-known and has been used, for example, in MPLS networks. To use IP/UDP encapsulation for an active OAM protocol the Protocol Type field of the Geneve header MUST be set to IPv4 (0x0800) or IPv6 (0x86DD) value. But extra IP/UDP headers that immediately follow the Geneve header adds to processing of OAM message, further disassociates OAM message from the Geneve header, all of which may cause false negative or positive failure reports. Also, the additional IP/UDP header adds noticeable overhead, especially if the underlay is the IPv6 network.

An associated control channel can be defined directly for a Geneve tunnel. This document defines the shim for Geneve is presented in Figure 1 to demultiplex Geneve OAM protocols without much of the overhead. The value of the Protocol Type MAY be set to 0x8902, the value assigned to the IEEE 802.1ag Connectivity Fault Management protocol as part of [IEEE.8021Q] and shared by ITU-T G.8013/Y.1731 OAM functions and mechanisms for Ethernet-based networks [ITU-T.1731]. Alternatively, the new value MAY be requested from the Ether Types registry.

3. Associated Control Channel in Geneve Networks

An associated control channel in the Geneve network is the channel that, by using the same encapsulation as user traffic, follows the same path through the underlay network as user traffic. In other words, the associated channel is in-band with user traffic. Creating the notion of the associated control channel (ACC) in the Geneve network ensures that packets of active OAM protocols carried in the ACC are in-band with user traffic.

4. Associated Control Channel Header in Geneve

 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
| V |           Msg Type        |           Length              |

Figure 1: Format of the Associated Channel Header in Geneve Network

ACC Header immediately follows the Geneve header defined in [I-D.ietf-nvo3-geneve] and identifies the type of message carried over the Geneve ACC. The format of the Geneve ACC Header is:

The ACC Header consists of the following fields:

4.1. Use of the Geneve ACC Header in Active OAM

 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
~              Underlay network encapsulation                   ~
|Ver|  Opt Len  |O|C|    Rsvd.  |          Protocol Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Geneve
|        Virtual Network Identifier (VNI)       |    Reserved   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Header
|                    Variable Length Options                    |
| V |           Msg Type        |           Length              | ACC
~                    Active OAM message                          ~

Figure 2: Geneve OAM Header in Active OAM Packet

Active OAM methods, whether used for fault management or performance monitoring, generate dedicated test packets [RFC7799]. Format of an OAM test packet in the Geneve network presented in Figure 2.

5. Echo Request and Echo Reply in Geneve Tunnel

[Ed.note] Will be expanded in future versions.

6. IANA Considerations

IANA is requested to create a new registry called "Geneve Associated Channel".

6.1. Geneve Associated Channel Protocol Types

IANA is requested to create new sub-registry called "Geneve Associated Channel Protocol Types" in the "Geneve Associated Channel" registry. All code points in the range 1 through 15615 in this registry shall be allocated according to the "IETF Review" procedure as specified in [RFC8126]. Remaining code points are allocated according to Table 1:

Geneve OAM Protocol type
Value Description Reference
0 Reserved
1 - 15615 Unassigned IETF Review
15616 - 16127 Unassigned First Come First Served
16128 - 16143 Experimental This document
16144 - 16382 Private Use This document
16383 Reserved This document

7. Security Considerations


8. Acknowledgment


9. References

9.1. Normative References

[I-D.ietf-nvo3-geneve] Gross, J., Ganga, I. and T. Sridhar, "Geneve: Generic Network Virtualization Encapsulation", Internet-Draft draft-ietf-nvo3-geneve-16, March 2020.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC4385] Bryant, S., Swallow, G., Martini, L. and D. McPherson, "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385, February 2006.
[RFC5586] Bocci, M., Vigoureux, M. and S. Bryant, "MPLS Generic Associated Channel", RFC 5586, DOI 10.17487/RFC5586, June 2009.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017.

9.2. Informative References

[IEEE.8021Q] IEEE, "IEEE Standard for Local and metropolitan area networks -- Bridges and Bridged Networks", IEEE Std 802.1Q, December 2014.
[ITU-T.1731] ITU-T, "Operations, administration and maintenance (OAM) functions and mechanisms for Ethernet-based networks", ITU-T G.8013/Y.1731, August 2015.
[RFC7799] Morton, A., "Active and Passive Metrics and Methods (with Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799, May 2016.
[RFC8126] Cotton, M., Leiba, B. and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017.

Appendix A. Additional Considerations for OAM Encapsulation Method in Geneve

Several other options of OAM encapsulation were considered. Those are listed in the Appendix solely for the informational purpose.

A Protocol Type field might be used to demultiplex active OAM protocols directly. Such method avoids the use of additional intermediate header but requires that each active OAM protocol be assigned unique identifier from the Ether Types registry maintained by IANA.

The alternative to using the Protocol Type directly is to use a shim that, in turn, identifies the OAM Protocol and, optionally, includes additional information. [RFC5586] defines how the Generic Associated Channel Label (GAL) can be used to identify that the Associated Channel Header (ACH), defined in [RFC4385], immediately follows the Bottom-of-the-Stack label. Thus the MPLS Generic Associated Channel can be identified, and protocols are demultiplexed based on the value of the Channel Type field. Number of channel types, e.g., for continuity check and performance monitoring, already have been defined and are listed in IANA MPLS Generalized Associated Channel Types (including Pseudowire Associated Channel Types) registry. To use this approach, the value of the Protocol Type field in the Geneve header MUST be set to MPLS. The Geneve header MUST be immediately followed by the GAL label with the S flag set to indicate that GAL is the Bottom-of-the-stack label. Then ACH MUST follow the GAL label and the value of the Channel Type identifies which of active OAM protocols being encapsulated in the packet.

Authors' Addresses

Greg Mirsky ZTE Corp. EMail: gregimirsky@gmail.com
Xiao Min ZTE Corp. EMail: xiao.min2@zte.com.cn
Sami Boutros Ciena EMail: sboutros@ciena.com
David Black Dell EMC 176 South Street Hopkinton, MA, 01748 United States of America EMail: david.black@dell.com
Santosh Pallagatti (editor) VMware EMail: santosh.pallagatti@gmail.com