SPRING Working Group R. Gandhi, Ed.
Internet-Draft Z. Ali
Intended status: Standards Track C. Filsfils
Expires: February 23, 2020 F. Brockners
Cisco Systems, Inc.
B. Wen
V. Kozak
Comcast
August 22, 2019
Segment Routing with MPLS Data Plane Encapsulation
for In-situ OAM Data
draft-gandhi-spring-ioam-sr-mpls-02
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. Segment
Routing (SR) technology leverages the source routing paradigm. This
document defines how IOAM data fields are transported with the
Segment Routing with MPLS data plane (SR-MPLS) encapsulation. The
procedures defined are also equally applicable to all other MPLS data
plane encapsulations.
Status of This Memo
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document authors. All rights reserved.
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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 SR-MPLS Header . . . . . . . 3
4. Procedure for Edge-to-Edge IOAM . . . . . . . . . . . . . . . 5
4.1. Edge-to-Edge IOAM Indicator Labels . . . . . . . . . . . . 6
5. Procedure for Hop-by-Hop IOAM . . . . . . . . . . . . . . . . 7
6. Considerations for ECMP . . . . . . . . . . . . . . . . . . . 7
7. Node Capability . . . . . . . . . . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
9. Security Considerations . . . . . . . . . . . . . . . . . . . 8
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
11.1. Normative References . . . . . . . . . . . . . . . . . . 8
11.2. Informative References . . . . . . . . . . . . . . . . . 9
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
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.
Segment Routing (SR) technology leverages the source routing paradigm
[I-D.ietf-spring-segment-routing-mpls]. A node steers a packet
through a controlled set of instructions, called segments, by
pre-pending the packet with an SR header. In the MPLS data plane,
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the SR header is instantiated through a label stack.
This document defines how IOAM data fields are transported with the
SR with MPLS data plane (SR-MPLS) encapsulation. The procedures
defined are also equally applicable to all other MPLS data plane
encapsulations.
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
PBT Postcard Based Telemetry
PM Performance Measurement
PoT Proof-of-Transit
SR Segment Routing
SR-MPLS Segment Routing with MPLS Data plane
3. IOAM Data Field Encapsulation in SR-MPLS Header
SR-MPLS encapsulation is defined in
[I-D.ietf-spring-segment-routing-mpls]. The IOAM data fields are
defined in [I-D.ietf-ippm-ioam-data]. IOAM data fields are carried
in the SR-MPLS header as shown in Figure 1 and Figure 2. More than
one trace options can be present in the IOAM data fields. The
Indicator Label is added at the bottom of the MPLS label stack (S
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flag set to 1) to indicate the presence of the IOAM data field(s) in
the MPLS 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IOAM Indicator Label TBA1 | TC |1| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
| IOAM-Type | IOAM HDR LEN | RESERVED | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ I
| | O
| | A
~ IOAM Option and Data Space ~ M
| | |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
| |
| |
| Payload + Padding (L2/L3/ESP/...) |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: IOAM data encapsulation in SR-MPLS 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IOAM and Flow Indicator Label TBA2 | TC |1| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Flow label | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
| IOAM-Type | IOAM HDR LEN | RESERVED | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ I
| | O
| | A
~ IOAM Option and Data Space ~ M
| | |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
| |
| |
| Payload + Padding (L2/L3/ESP/...) |
| |
| |
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| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: IOAM data encapsulation with Flow Label in SR-MPLS Header
Indicator Label and Flow Label as defined in this document.
The fields related to the encapsulation of IOAM data fields in the
SR-MPLS header are defined as follows:
IOAM-Type: 8-bit field defining the IOAM Option type, as defined in
Section 7.2 of [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 upon
transmission and ignored upon receipt.
IOAM Option and Data Space: IOAM option header and data is present
as defined by the IOAM-Type field, and is defined in Section 4 of
[I-D.ietf-ippm-ioam-data].
4. Procedure for Edge-to-Edge IOAM
This section summarizes the procedure for data encapsulation and
decapsulation for IOAM Edge-to-Edge Option Type
[I-D.ietf-ippm-ioam-data] in SR-MPLS header.
o The encapsulating node inserts the IOAM Indicator Label or IOAM
Flow Indicator Label with Flow Label and one or more IOAM data
field(s) in the MPLS header. The procedure to generate the Flow
Label is outside the scope of this document.
o The decapsulating node "forwards and punts the timestamped copy"
of the data packet including IOAM data fields when the node
recognizes the IOAM Indicator Label and IOAM Flow 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 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.
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o The decapsulating node also pops the Indicator Label and the IOAM
data fields from the MPLS 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment List(1) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment List(n) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSID | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Packet as shown in Figure 1 or Figure 2 |
. .
+---------------------------------------------------------------+
Figure 3: Data Packet over SR-MPLS Policy
4.1. Edge-to-Edge IOAM Indicator Labels
IOAM Indicator Label (value TBA1) and IOAM and Flow Indicator Label
(value TBA2) are used to indicate the presence of the IOAM data field
in the MPLS header.
The Indicator Label with value TBA2 is used to carry a second label
underneath with protocol value 0000b and 20-bit Flow Label. The
protocol value 0000b allows to avoid incorrect IP header based
hashing over ECMP paths that uses the value 0x4 (for IPv4) and value
0x6 (for IPv6) [RFC4928]. The Flow Label identifies the traffic flow
that can be used for IOAM purpose as well as for hashing over ECMP
paths.
The IOAM Indicator Label and IOAM and Flow 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 [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. The signaling
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extension for this is outside the scope of this document.
5. Procedure for Hop-by-Hop IOAM
The hop-by-hop IOAM includes IOAM-Types IOAM Pre-allocated Trace
Option Type, IOAM Incremental Trace Option Type and IOAM POT Option
Type.
Different Indicator Labels (TBA3 and TBA4) are used for hop-by-hop
IOAM.
The details for hop-by-hop IOAM will be added in a future version of
the document.
6. Considerations for ECMP
The encapsulating node needs to make sure the IOAM data field does
not start with a well known IP protocol value (e.g. 0x4 for IPv4 and
0x6 for IPv6) as it can alter the hashing function for ECMP that uses
the IP header. This can be achieved by using the IOAM and Flow
Indicator Label (value TBA2 and TBA4) that follows by protocol value
0000b. This approach is consistent with the use of utilizing 0000b
as the first nibble 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 also now include the Indicator Label.
The entropy label can be used for hashing function for ECMP as
defined in [RFC6790].
7. Node Capability
The decapsulating node that has to pop the 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.
8. IANA Considerations
IANA maintains the "Special-Purpose Multiprotocol Label Switching
(MPLS) Label Values" registry (see
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<https://www.iana.org/assignments/mpls-label-values/mpls-label-
values.xml>). IANA is requested to allocate IOAM Indicator Label
value and IOAM and Flow Indicator value from the "Extended
Special-Purpose MPLS Label Values" registry:
+-------------+-----------------------------------+---------------+
| Value | Description | Reference |
+-------------+-----------------------------------+---------------+
| TBA1 | E2E IOAM Indicator Label | This document |
+-------------+-----------------------------------+---------------+
| TBA2 | E2E IOAM and Flow Indicator Label | This document |
+-------------+-----------------------------------+---------------+
| TBA3 | HbH IOAM Indicator Label | This document |
+-------------+-----------------------------------+---------------+
| TBA4 | HbH IOAM and Flow Indicator Label | This document |
+-------------+-----------------------------------+---------------+
9. Security Considerations
The security considerations of SR-MPLS are discussed in
[I-D.ietf-spring-segment-routing-mpls], 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.
10. Acknowledgements
The authors would like to thank Shwetha Bhandari and Vengada Prasad
Govindan for the discussions on IOAM. The authors would also like to
thank Tarek Saad, Loa Andersson and Cheng Li for providing many
useful comments.
11. References
11.1. 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.
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[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", RFC 8174, May 2017.
[I-D.ietf-spring-segment-routing-mpls] Bashandy, A., Filsfils, C.,
Previdi, S., Decraene, B., Litkowski, S., and R. Shakir,
"Segment Routing with MPLS data plane",
draft-ietf-spring-segment-routing-mpls, work in progress.
[I-D.ietf-ippm-ioam-data] Brockners, F., Bhandari, S., Pignataro,
C., Gredler, H., Leddy, J., Youell, S., Mizrahi, T.,
Mozes, D., Lapukhov, P., Chang, R., and Bernier, D., "Data
Fields for In-situ OAM", draft-ietf-ippm-ioam-data, work
in progress.
11.2. Informative References
[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, February 2006.
[RFC4928] Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal
Cost Multipath Treatment in MPLS Networks", BCP 128, RFC
4928, June 2007.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, November 2012.
[mpls-spl-terminology] L. Andersson, et al. "Special Purpose Label
terminology", draft-ietf-mpls-spl-terminology, work in
progress.
Contributors
Sagar Soni
Cisco Systems, Inc.
Email: sagsoni@cisco.com
Patrick Khordoc
Cisco Systems, Inc.
Email: pkhordoc@cisco.com
Authors' Addresses
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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
Bin Wen
Comcast
Email: Bin_Wen@cable.comcast.com
Voitek Kozak
Comcast
Email: Voitek_Kozak@comcast.com
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