VXLAN-GPE Encapsulation for In-situ OAM Data
draft-brockners-ioam-vxlan-gpe-00

Abstract

In-situ Operations, Administration, and Maintenance (IOAM) records operational and telemetry information in the packet while the packet traverses a path between two points in the network. This document outlines how IOAM data fields are encapsulated in VXLAN-GPE.

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Table of Contents

• 1. Introduction
• 2. Conventions
• 2.1. Requirement Language
• 2.2. Abbreviations
• 3. IOAM Data Field Encapsulation in VXLAN-GPE
• 3.1. IOAM Trace Data in VXLAN-GPE
• 3.2. IOAM POT Data in VXLAN-GPE
• 3.3. IOAM Edge-to-Edge Data in VXLAN-GPE
• 4. Discussion of the encapsulation approach
• 5. IANA Considerations
• 6. Security Considerations
• 7. Acknowledgements
• 8. References
• 8.1. Normative References
• 8.2. Informative References
• Authors' Addresses

1. Introduction

In-situ OAM (IOAM) records OAM information within the packet while the packet traverses a particular network domain. The term "in-situ" refers to the fact that the IOAM data fields are added to the data packets rather than being sent within packets specifically dedicated to OAM. This document defines how IOAM data fields are transported as part of the VXLAN-GPE [I-D.ietf-nvo3-vxlan-gpe] encapsulation. The IOAM data fields are defined in [I-D.ietf-ippm-ioam-data]. An implementation of IOAM which leverages VXLAN-GPE to carry the IOAM data is available from the FD.io open source software project [FD.io].

2. Conventions

2.1. Requirement 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].

2.2. Abbreviations

Abbreviations used in this document:

IOAM:

In-situ Operations, Administration, and Maintenance

MTU:

Maximum Transmit Unit

OAM:

Operations, Administration, and Maintenance

POT:

Proof of Transit

SFC:

Service Function Chain

VXLAN-GPE:

Virtual eXtensible Local Area Network, Generic Protocol Extension

3. IOAM Data Field Encapsulation in VXLAN-GPE

For encapsulating IOAM data fields into VXLAN-GPE [I-D.ietf-nvo3-vxlan-gpe] the different IOAM data fields are added as options within new IOAM protocol headers in VXLAN-GPE. In an administrative domain where IOAM is used, insertion of the IOAM protocol header(s) in VXLAN GPE is enabled at the VXLAN-GPE tunnel endpoints which also serve as IOAM encapsulating/decapsulating nodes by means of configuration. The VXLAN-GPE header is defined in [I-D.ietf-nvo3-vxlan-gpe]. IOAM specific fields for VXLAN-GPE are defined in this document.

3.1. IOAM Trace Data in VXLAN-GPE

IOAM tracing data represents data that is inserted at nodes that a packet traverses. To allow for optimal implementations in both software as well as hardware forwarders, two different ways to encapsulate IOAM data are defined: "Pre-allocated" and "Incremental". See [I-D.ietf-ippm-ioam-data] for details on IOAM tracing and the pre-allocated and incremental IOAM trace options.

The packet formats of the pre-allocated IOAM trace and incremental IOAM trace when encapsulated in VXLAN-GPE are defined as below.

 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 IP Header                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                       Outer UDP Header                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+
|R|R|Ver|I|P|R|O|          Reserved             |NP=IOAM_Trace  |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ GPE
|     Virtual Network Identifier (VNI)          | Reserved      |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+
|      Type     |   IOAM HDR len|    Reserved   | Next Protocol |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ IOAM
|         IOAM-Trace-Type       |NodeLen|  Flags  | Octets-left | Trace
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
|                                                               |  |
|                        node data list [0]                     | IOAM
|                                                               |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  D
|                                                               |  a
|                        node data list [1]                     |  t
|                                                               |  a
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~                             ...                               ~  S
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  p
|                                                               |  a
|                        node data list [n-1]                   |  c
|                                                               |  e
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  |
|                                                               |  |
|                        node data list [n]                     |  |
|                                                               |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-<--+
|                                                               |
|                                                               |
|                     Payload + Padding (L2/L3/ESP/...)         |
|                                                               |
|                                                               |
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Pre-allocated Trace Option Data MUST be 4-octet aligned.

Figure 1: IOAM Pre-allocated Trace Option Format over VXLAN-GPE

 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 IP Header                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                       Outer UDP Header                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+
|R|R|Ver|I|P|R|O|          Reserved             | NP=IOAM_Trace |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ GPE
|     Virtual Network Identifier (VNI)          | Reserved      |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+
|      Type     |   IOAM HDR len|    Reserved   | Next Protocol |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ IOAM
|        IOAM-Trace-Type        |NodeLen|  Flags  | Max Length  | Trace
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
|                                                               |  |
|                        node data list [0]                     | IOAM
|                                                               |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  D
|                                                               |  a
|                        node data list [1]                     |  t
|                                                               |  a
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~                             ...                               ~  S
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  p
|                                                               |  a
|                        node data list [n-1]                   |  c
|                                                               |  e
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  |
|                                                               |  |
|                        node data list [n]                     |  |
|                                                               |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-<--+
|                                                               |
|                                                               |
|                     Payload + Padding (L2/L3/ESP/...)         |
|                                                               |
|                                                               |
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IOAM Incremental Trace Option Data MUST be 4-octet aligned.

Figure 2: IOAM Incremental Trace Option Format over VXLAN-GPE

The IOAM Trace header consists of 8 octets, as illustrated in Figure 1 and Figure 2. The format of the first 4 octets (Figure 3) is specific to VXLAN-GPE, and is defined in this document. The format of the next 4 octets (trace option header) is defined in [I-D.ietf-ippm-ioam-data], and is described here for the sake of clarity.

 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Type     |   IOAM HDR len|    Reserved   | Next Protocol |  
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 3: Trace Shim Header for VXLAN-GPE

The fields of the trace shim header are as follows:

Type:

8-bit unsigned integer defining IOAM header type IOAM_TRACE_Preallocated or IOAM_Trace_Incremental are defined here.

IOAM HDR len:

8-bit unsigned integer. Length of the IOAM HDR in 4-octet units.

Reserved:

8-bit reserved field MUST be set to zero.

Next Protocol:

8-bit unsigned integer that determines the type of header following IOAM protocol. The value is from the IANA registry setup for VXLAN GPE Next Protocol defined in [I-D.ietf-nvo3-vxlan-gpe].

The fields of the trace option header [I-D.ietf-ippm-ioam-data] are as follows:

IOAM-Trace-Type:

16-bit identifier of IOAM Trace Type as defined in [I-D.ietf-ippm-ioam-data] IOAM-Trace-Types.

Node Data Length:

4-bit unsigned integer as defined in [I-D.ietf-ippm-ioam-data].

Flags:

5-bit field as defined in [I-D.ietf-ippm-ioam-data].

Octets-left:

7-bit unsigned integer as defined in [I-D.ietf-ippm-ioam-data].

Maximum-length:

7-bit unsigned integer as defined in [I-D.ietf-ippm-ioam-data].

Node data List [n]:

Variable-length field as defined in [I-D.ietf-ippm-ioam-data].

3.2. IOAM POT Data in VXLAN-GPE

IOAM proof of transit (POT, see also [I-D.brockners-proof-of-transit]) offers a means to verify that a packet has traversed a defined set of nodes. IOAM POT data fields are encapsulated in VXLAN-GPE using a dedicated VXLAN-GPE protocol 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 IP Header                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                       Outer UDP Header                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+
|R|R|Ver|I|P|R|O|          Reserved(MBZ)        |NP = IOAM_POT  |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ GPE
|     Virtual Network Identifier (VNI)          | Reserved      |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+
|IOAM POT Type|P|   IOAM HDR len|    Reserved   | Next Protocol |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ IOAM
|                           Random                              |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  P
|                        Random(contd.)                         |  O
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  T
|                         Cumulative                            |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  |
|                    Cumulative (contd.)                        |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+

Figure 4: IOAM POT Header Following the VXLAN-GPE Header

The IOAM POT Shim Header (Figure 5), which is defined in this document, is a 4-octet header, that includes the following fields:

IOAM POT Type:

7-bit identifier of a particular POT variant that specifies the POT data that is to be included as defined in [I-D.ietf-ippm-ioam-data].

Profile to use (P):

1-bit as defined in [I-D.ietf-ippm-ioam-data] IOAM POT Option.

IOAM HDR len:

8-bit unsigned integer. Length of the IOAM HDR in 4-octet units.

Reserved:

8-bit reserved field MUST be set to zero.

Next Protocol:

8-bit unsigned integer that determines the type of header following IOAM protocol. The value is from the IANA registry setup for VXLAN GPE Next Protocol defined in [I-D.ietf-nvo3-vxlan-gpe].

 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|IOAM POT Type|P|   IOAM HDR len|    Reserved   | Next Protocol |  
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 5: POT Shim Header for VXLAN-GPE

The rest of the fields in the POT option [I-D.ietf-ippm-ioam-data] are as follows:

Random:

64-bit Per-packet random number.

Cumulative:

64-bit Cumulative value that is updated by the Service Functions.

3.3. IOAM Edge-to-Edge Data in VXLAN-GPE

The IOAM edge-to-edge option is to carry data that is added by the IOAM encapsulating node and interpreted by the IOAM decapsulating node. IOAM specific fields to encapsulate IOAM Edge-to-Edge data fields are defined as follows:

 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 IP Header                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                       Outer UDP Header                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+
|R|R|Ver|I|P|R|O|          Reserved             |NP = IOAM_E2E  |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ GPE
|     Virtual Network Identifier (VNI)          | Reserved      |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+
|Type=IOAM_E2E  |   IOAM HDR len  |  Reserved   | Next Protocol |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+IOAM
|      E2E Option data field determined by IOAM-E2E-Type        |  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+

Figure 6: IOAM Edge-to-Edge over a VXLAN-GPE Header

The IOAM E2E Shim Header, which is defined in this document, is a 4-octet header, that includes the following fields:

Type:

8-bit identifier of a particular E2E variant that specifies the E2E data that is to be included as defined in [I-D.ietf-ippm-ioam-data].

IOAM HDR len:

8-bit unsigned integer. Length of the IOAM HDR in 4-octet units.

Reserved:

8-bit reserved field MUST be set to zero.

Next Protocol:

8-bit unsigned integer that determines the type of header following IOAM protocol. The value is from the IANA registry setup for VXLAN GPE Next Protocol defined in [I-D.ietf-nvo3-vxlan-gpe].

 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type=IOAM_E2E  |   IOAM HDR len  |  Reserved   | Next Protocol | 
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 7: E2E Shim Header for VXLAN-GPE

The rest of the E2E option [I-D.ietf-ippm-ioam-data] consists of:

E2E Option data field:

Variable length field as defined in [I-D.ietf-ippm-ioam-data] IOAM E2E Option.

4. Discussion of the encapsulation approach

This section is to support the working group discussion in selecting the most appropriate approach for encapsulating IOAM data fields in VXLAN-GPE.

An encapsulation of IOAM data fields in VXLAN-GPE should be friendly to an implementation in both hardware as well as software forwarders. Hardware forwarders benefit from an encapsulation that minimizes iterative look-ups of fields within the packet: Any operation which looks up the value of a field within the packet, based on which another lookup is performed, consumes additional gates and time in an implementation - both of which are desired to be kept to a minimum. This means that flat TLV structures are to be preferred over nested TLV structures. IOAM data fields are grouped into three option categories: Trace, proof-of-transit, and edge-to-edge. Each of these three options defines a TLV structure. A hardware-friendly encapsulation approach avoids grouping these three option categories into yet another TLV structure, but would rather carry the options as a serial sequence.

Two approaches for encapsulating IOAM data fields in VXLAN-GPE could be considered:

1. Use a single GPE protocol type for all IOAM types: IOAM would receive a single GPE protocol type code point. A "sub-type" (e.g. 4 bit wide) would then specify what IOAM options type(s) (trace, proof-of-transit, edge-to-edge) are carried. In case there is a need for additional IOAM options, changes would be contained within the single GPE protocol type for IOAM.
2. Use one GPE protocol type per IOAM options type: Each IOAM data field option (trace, proof-of-transit, and edge-to-edge) would be specified by its own "next protocol", i.e. each IOAM options type becomes its own GPE protocol type with a dedicated code point. This implies that in case additional IOAM option types would be added in the future, additional GPE protocol type code points would need to be allocated.

The second option has been chosen here, because it avoids the additional layer of TLV nesting that the use of a single GPE protocol type for all IOAM option types would result in.

5. IANA Considerations

IANA is requested to allocate protocol numbers for the following VXLAN-GPE "Next Protocols" related to IOAM:

              +---------------+-------------+---------------+
              | Next Protocol | Description | Reference     |
              +---------------+-------------+---------------+
              | x             | IOAM_Trace  | This document |
              | y             | IOAM_POT    | This document |
              | z             | IOAM_E2E    | This document |
              +---------------+-------------+---------------+

6. Security Considerations

The security considerations of VXLAN-GPE are discussed in [I-D.ietf-nvo3-vxlan-gpe], and the security considerations of IOAM in general are discussed in [I-D.ietf-ippm-ioam-data].

IOAM is considered a "per domain" feature, where one or several operators decide on leveraging and configuring IOAM according to their needs. Still, operators need to properly secure the IOAM domain to avoid malicious configuration and use, which could include injecting malicious IOAM packets into a domain.

7. Acknowledgements

The authors would like to thank Eric Vyncke, Nalini Elkins, Srihari Raghavan, Ranganathan T S, Karthik Babu Harichandra Babu, Akshaya Nadahalli, Stefano Previdi, Hemant Singh, Erik Nordmark, LJ Wobker, and Andrew Yourtchenko for the comments and advice.

8. References

8.1. Normative References

8.2. Informative References

Authors' Addresses