MPLS Data Plane Encapsulation for In-situ OAM Data
draft-gandhi-mpls-ioam-sr-04
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
|
|
|---|---|---|---|
| Authors | Rakesh Gandhi , Zafar Ali , Clarence Filsfils , Frank Brockners , Bin Wen , Voitek Kozak | ||
| Last updated | 2020-12-10 (Latest revision 2020-11-25) | ||
| Replaces | draft-gandhi-spring-ioam-sr-mpls | ||
| Replaced by | draft-gandhi-mpls-ioam, draft-gandhi-mpls-ioam, draft-gandhi-mpls-ioam | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | Candidate for WG Adoption | |
| Document shepherd | Loa Andersson | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | loa@pi.nu |
draft-gandhi-mpls-ioam-sr-04
MPLS Working Group R. Gandhi, Ed.
Internet-Draft Z. Ali
Intended status: Standards Track C. Filsfils
Expires: May 29, 2021 F. Brockners
Cisco Systems, Inc.
B. Wen
V. Kozak
Comcast
November 25, 2020
MPLS Data Plane Encapsulation for In-situ OAM Data
draft-gandhi-mpls-ioam-sr-04
Abstract
In-situ Operations, Administration, and Maintenance (IOAM) records
operational and telemetry information in the data packet while the
packet traverses a path between two nodes in the network. This
document defines how IOAM data fields are transported using the MPLS
data plane encapsulation, including Segment Routing (SR) with MPLS
data plane (SR-MPLS).
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirement Language . . . . . . . . . . . . . . . . . . 3
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
3. IOAM Data Field Encapsulation in MPLS Header . . . . . . . . 3
3.1. IOAM Indicator Labels . . . . . . . . . . . . . . . . . . 5
4. Procedure for Edge-to-Edge IOAM . . . . . . . . . . . . . . . 5
4.1. Edge-to-Edge IOAM Indicator Label Allocation . . . . . . 6
5. Procedure for Hop-by-Hop IOAM . . . . . . . . . . . . . . . . 6
5.1. Hop-by-Hop IOAM Indicator Label Allocation . . . . . . . 7
6. Considerations for ECMP . . . . . . . . . . . . . . . . . . . 7
7. Node Capability . . . . . . . . . . . . . . . . . . . . . . . 7
8. Data Packets with SR-MPLS Header . . . . . . . . . . . . . . 8
9. Security Considerations . . . . . . . . . . . . . . . . . . . 8
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
11.1. Normative References . . . . . . . . . . . . . . . . . . 9
11.2. Informative References . . . . . . . . . . . . . . . . . 10
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 11
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
In-situ Operations, Administration, and Maintenance (IOAM) records
operational and telemetry 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 the probe packets specifically
dedicated to OAM or Performance Measurement (PM). The IOAM data
fields are defined in [I-D.ietf-ippm-ioam-data], and can be used for
various use-cases for OAM and PM. The IOAM data fields are further
updated in [I-D.ietf-ippm-ioam-direct-export] for direct export use-
cases and in [I-D.ietf-ippm-ioam-flags] for Loopback and Active
flags.
This document defines how IOAM data fields are transported using the
MPLS data plane encapsulations, including Segment Routing (SR) with
MPLS data plane (SR-MPLS).
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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] [RFC8174]
when, and only when, they appear in all capitals, as shown here.
2.2. Abbreviations
Abbreviations used in this document:
ECMP Equal Cost Multi-Path
IOAM In-situ Operations, Administration, and Maintenance
MPLS Multiprotocol Label Switching
OAM Operations, Administration, and Maintenance
PM Performance Measurement
POT Proof-of-Transit
PSID Path Segment Identifier
SR Segment Routing
SR-MPLS Segment Routing with MPLS Data plane
3. IOAM Data Field Encapsulation in MPLS Header
The IOAM data fields defined in [I-D.ietf-ippm-ioam-data] are used.
IOAM data fields are carried in the MPLS header as shown in Figure 1.
More than one trace options can be present in the IOAM data fields.
The IOAM Indicator Label is added at the bottom of the MPLS label
stack (S flag set to 1) and it indicates the presence of the IOAM
data field(s) in the MPLS header.
The data packets with IOAM data fields carry only one IOAM Indicator
Label in the MPLS header. Any intermediate node that adds additional
MPLS encapsulation in the MPLS header may further update the IOAM
data fields in the header without inserting another IOAM Indicator
Label.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extension Label (15) | TC |0| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IOAM Indicator Label | TC |1| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
|0 0 1 0|R|R|R|R| Block Number | IOAM-OPT-Type |IOAM HDR Length| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ I
| | O
| | A
~ IOAM Option and Data Space ~ M
| | |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
| |
| |
| Payload + Padding |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: IOAM Encapsulation in MPLS Header
IOAM Indicator Label (IIL) (Edge-to-Edge or Hob-By-Hop) as defined in
this document.
The fields related to the encapsulation of IOAM data fields in the
MPLS header are defined as follows:
IP Version Number 0010b: The IP Version Number Field 0010b allows to
avoid incorrect IP header-based hashing over ECMP paths that uses
the value 0x4 (for IPv4) and value 0x6 (for IPv6) [RFC4928].
Block Number: The Block Number can be used to aggregate the IOAM
data collected in data plane, e.g. compute measurement metrics for
each block of a flow. It is also used to correlate the IOAM data
on different nodes.
R Bits: Reserved Bits MUST be set to zero upon transmission and
ignored upon receipt.
IOAM-OPT-Type: 8-bit field defining the IOAM Option type, as defined
in Section 8.1 of [I-D.ietf-ippm-ioam-data].
IOAM HDR LEN: 8-bit unsigned integer. Length of the IOAM HDR in
4-octet units.
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IOAM Option and Data Space: IOAM option header and data is present
as defined by the IOAM-OPT-Type field, and is defined in Section 5
of [I-D.ietf-ippm-ioam-data].
3.1. IOAM Indicator Labels
IOAM Indicator Label is used to indicate the presence of the IOAM
data field in the MPLS header.
Different IOAM Indicator Labels are used for E2E and HbH IOAM to
optimize processing on transit nodes and for checking if IOAM data
fields need to be processed. If only edge nodes need to process IOAM
data then E2E IOAM Indicator Label is used so that transit nodes can
ignore it. If both edge and transit nodes need to process IOAM data
then HbH IOAM Indicator Label is used.
The SR path computation needs to know the Maximum SID Depth (MSD)
that can be imposed at each node/link of a given SR path [RFC8664].
This ensures that the SID stack depth of a computed path does not
exceed the number of SIDs the node is capable of imposing. The MSD
used for path computation MUST include the IOAM Indicator Label.
4. Procedure for Edge-to-Edge IOAM
The Edge-to-Edge (E2E) IOAM includes IOAM Option-Type as Edge-to-Edge
Option-Type [I-D.ietf-ippm-ioam-data]. This section summarizes the
procedure for data encapsulation and decapsulation for Edge-to-Edge
IOAM in MPLS header.
o The encapsulating node inserts the E2E IOAM Indicator Label and
one or more IOAM data field(s) in the MPLS header.
o The decapsulating node "forwards and punts the timestamped copy"
of the data packet including IOAM data fields when the node
recognizes the E2E IOAM Indicator Label. The copy of the data
packet is punted to the slow path for OAM processing and is not
necessarily punted to the control-plane. The receive timestamp is
required by various E2E OAM use-cases.
o The decapsulating node processes the IOAM data field(s) using the
procedures defined in [I-D.ietf-ippm-ioam-data]. An example of
IOAM processing may be to export the data fields, send data fields
via Telemetry, etc.
o The decapsulating node also pops the E2E IOAM Indicator Label and
the IOAM data fields from the MPLS header.
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4.1. Edge-to-Edge IOAM Indicator Label Allocation
E2E IOAM Indicator Label is used to indicate the presence of the E2E
IOAM data field in the MPLS header. The E2E IOAM Indicator Label can
be allocated using one of the following methods:
o Labels assigned by IANA with value TBA1 and TBA2 from the Extended
Special-Purpose MPLS Values [I-D.ietf-mpls-spl-terminology].
o Labels allocated by a Controller from the global table of the
decapsulating node. The Controller provisions the label on both
encapsulating and decapsulating nodes.
o Labels allocated by the decapsulating node and signalled or
advertised in the network. The signaling and/or advertisement
extension for this is outside the scope of this document.
5. Procedure for Hop-by-Hop IOAM
The Hop-by-Hop (HbH) IOAM includes IOAM Option-Types IOAM Pre-
allocated Trace Option-Type, IOAM Incremental Trace Option-Type and
IOAM Proof of Transit (POT) Option-Type [I-D.ietf-ippm-ioam-data].
This section summarizes the procedure for data encapsulation and
decapsulation for Hop-by-hop IOAM in MPLS header.
o The encapsulating node inserts the HbH IOAM Indicator Label and
one or more IOAM data field(s) in the MPLS header.
o The intermediate and decapsulating node enabled with IOAM
functions "forwards and punts the timestamped copy" of the data
packet including IOAM data fields when the node recognizes the HbH
IOAM Indicator Label. The copy of the data packet is punted to
the slow path for OAM processing and is not necessarily punted to
the control-plane. The receive timestamp is required by various
hop-by-hop OAM use-cases.
o The intermediate and decapsulating node processes the IOAM data
field(s) using the procedures defined in
[I-D.ietf-ippm-ioam-data]. An example of IOAM processing may be
to export the data fields, send data fields via Telemetry, etc.
o The decapsulating node pops the HbH IOAM Indicator Label and the
IOAM data fields from the MPLS header.
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5.1. Hop-by-Hop IOAM Indicator Label Allocation
HbH IOAM Indicator Label is used to indicate the presence of the HbH
IOAM data field in the MPLS header. The HbH IOAM Indicator Label can
be allocated using one of the following methods:
o Labels assigned by IANA with value TBA2 from the Extended Special-
Purpose MPLS Values [I-D.ietf-mpls-spl-terminology].
o Labels allocated by a Controller from the network-wide global
table. The Controller provisions the labels on all nodes
participating in IOAM functions along the data traffic path.
6. Considerations for ECMP
The encapsulating node needs to make sure the IOAM data field does
not start with a well known IP Version Number (e.g. 0x4 for IPv4 and
0x6 for IPv6) as it can alter the hashing function for ECMP that uses
the IP header. This is achieved by using the IOAM Indicator Label
that followed by IP Version Number 0010b. This approach is
consistent with utilizing 0000b or 0001b as the first nibble for IP
Version Number after the MPLS label stack, as described in [RFC4928]
[RFC4385].
Note that the hashing function for ECMP that uses the labels from the
MPLS header may now include the IOAM Indicator Label.
When entropy label [RFC6790] is used for hashing function for ECMP,
the procedure defined in this document does not alter the hashing
function.
7. Node Capability
The decapsulating node that has to pop the IOAM Indicator Label, data
fields, and perform the IOAM function may not be capable of
supporting it. The encapsulating node needs to know if the
decapsulating node can support the IOAM function. The signaling
extension for this capability exchange is outside the scope of this
document.
The intermediate node that is not capable of supporting the IOAM
functions defined in this document, can simply skip the IOAM
processing of the MPLS header.
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8. Data Packets with SR-MPLS Header
Segment Routing (SR) technology leverages the source routing paradigm
[RFC8660]. A node steers a packet through a controlled set of
instructions, called segments, by pre-pending the packet with an SR
header. In the SR with MPLS data plane (SR-MPLS), the SR header is
instantiated through a label stack.
An example of data packet carrying the SR-MPLS header with Path
Segment Identifier (PSID) [I-D.ietf-spring-mpls-path-segment] with
IOAM encapsulation is shown in Figure 2. The Path Segment Identifier
allows to identify the path associated with the data traffic being
monitored for IOAM on the decapsulating node.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label(1) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label(n) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSID | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Packet as shown in Figure 1 |
. .
+---------------------------------------------------------------+
Figure 2: Data Packet with SR-MPLS Header
9. Security Considerations
The security considerations of SR-MPLS are discussed in [RFC8660],
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.
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10. IANA Considerations
IANA maintains the "Special-Purpose Multiprotocol Label Switching
(MPLS) Label Values" registry (see <https://www.iana.org/assignments/
mpls-label-values/mpls-label-values.xml>). IANA is requested to
allocate IOAM Indicator Label value from the "Extended Special-
Purpose MPLS Label Values" registry:
+--------+--------------------------+---------------+
| Value | Description | Reference |
+--------+--------------------------+---------------+
| TBA1 | E2E IOAM Indicator Label | This document |
+--------+--------------------------+---------------+
| TBA2 | HbH IOAM Indicator Label | This document |
+--------+--------------------------+---------------+
IANA maintains IP Version Number Registry (see
<https://www.iana.org/assignments/version-numbers/version-
numbers.xml>). IANA is requested to allocate IP Version Number 0010b
for IOAM Data-type from "IP Version Numbers" registry.
11. References
11.1. Normative References
[I-D.ietf-ippm-ioam-data]
Brockners, F., Bhandari, S., and T. Mizrahi, "Data Fields
for In-situ OAM", draft-ietf-ippm-ioam-data-11 (work in
progress), November 2020.
[I-D.ietf-ippm-ioam-direct-export]
Song, H., Gafni, B., Zhou, T., Li, Z., Brockners, F.,
Bhandari, S., Sivakolundu, R., and T. Mizrahi, "In-situ
OAM Direct Exporting", draft-ietf-ippm-ioam-direct-
export-02 (work in progress), November 2020.
[I-D.ietf-ippm-ioam-flags]
Mizrahi, T., Brockners, F., Bhandari, S., Sivakolundu, R.,
Pignataro, C., Kfir, A., Gafni, B., Spiegel, M., and J.
Lemon, "In-situ OAM Flags", draft-ietf-ippm-ioam-flags-03
(work in progress), October 2020.
[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>.
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[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>.
[RFC8660] Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing with the MPLS Data Plane", RFC 8660,
DOI 10.17487/RFC8660, December 2019,
<https://www.rfc-editor.org/info/rfc8660>.
[RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "Path Computation Element Communication
Protocol (PCEP) Extensions for Segment Routing", RFC 8664,
DOI 10.17487/RFC8664, December 2019,
<https://www.rfc-editor.org/info/rfc8664>.
11.2. Informative References
[I-D.ietf-mpls-spl-terminology]
Andersson, L., Kompella, K., and A. Farrel, "Special
Purpose Label terminology", draft-ietf-mpls-spl-
terminology-05 (work in progress), November 2020.
[I-D.ietf-spring-mpls-path-segment]
Cheng, W., Li, H., Chen, M., Gandhi, R., and R. Zigler,
"Path Segment in MPLS Based Segment Routing Network",
draft-ietf-spring-mpls-path-segment-03 (work in progress),
September 2020.
[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, <https://www.rfc-editor.org/info/rfc4385>.
[RFC4928] Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal
Cost Multipath Treatment in MPLS Networks", BCP 128,
RFC 4928, DOI 10.17487/RFC4928, June 2007,
<https://www.rfc-editor.org/info/rfc4928>.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, DOI 10.17487/RFC6790, November 2012,
<https://www.rfc-editor.org/info/rfc6790>.
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Acknowledgements
The authors would like to thank Patrick Khordoc, Shwetha Bhandari and
Vengada Prasad Govindan for the discussions on IOAM. The authors
would also like to thank Tarek Saad, Loa Andersson, Greg Mirsky, and
Cheng Li for providing many useful comments.
Contributors
Sagar Soni
Cisco Systems, Inc.
Email: sagsoni@cisco.com
Authors' Addresses
Rakesh Gandhi (editor)
Cisco Systems, Inc.
Canada
Email: rgandhi@cisco.com
Zafar Ali
Cisco Systems, Inc.
Email: zali@cisco.com
Clarence Filsfils
Cisco Systems, Inc.
Belgium
Email: cf@cisco.com
Frank Brockners
Cisco Systems, Inc.
Hansaallee 249, 3rd Floor
DUESSELDORF, NORDRHEIN-WESTFALEN 40549
Germany
Email: fbrockne@cisco.com
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Bin Wen
Comcast
Email: Bin_Wen@cable.comcast.com
Voitek Kozak
Comcast
Email: Voitek_Kozak@comcast.com
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