SPRING Working Group R. Gandhi, Ed.
Internet-Draft Z. Ali
Intended status: Standards Track C. Filsfils
Expires: October 27, 2019 F. Brockners
Cisco Systems, Inc.
B. Wen
V. Kozak
Comcast
April 25, 2019
Segment Routing with MPLS Data Plane Encapsulation
for In-situ OAM Data
draft-gandhi-spring-ioam-sr-mpls-01
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 points in the network. This
document defines how IOAM data fields are transported with the
Segment Routing with MPLS data plane (SR-MPLS) encapsulation.
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 SR-MPLS Header . . . . . . . 3
4. Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. IOAM Indicator Label . . . . . . . . . . . . . . . . . . . 5
4.2. Hashing Function . . . . . . . . . . . . . . . . . . . . . 5
4.3. Node Capability . . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
8. Normative References . . . . . . . . . . . . . . . . . . . . . 7
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
In-situ Operations, Administration, and Maintenance (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 probe packets specifically dedicated to OAM.
Segment Routing (SR) 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, 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 IOAM data fields carried are defined in
[I-D.ietf-ippm-ioam-data], and can be used for various use-cases
including Performance Measurement (PM).
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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:
IOAM In-situ Operations, Administration, and Maintenance
OAM Operations, Administration, and Maintenance
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]. IOAM data fields are carried
in the SR-MPLS header, as IOAM data fields. The different IOAM data
fields defined in [I-D.ietf-ippm-ioam-data] are added as TLVs. More
than one TLVs 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) to indicate the presence of the IOAM data fields in
the MPLS header.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IOAM Indicator Label | TC |S| 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
IOAM Indicator Label as defined in Section 4.1.
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 4 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
This section summarizes the procedure for IOAM data encapsulation in
SR-MPLS.
o The ingress node inserts the IOAM Indicator Label and one or more
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IOAM TLV(s) in the MPLS header.
o The egress node "forwards and punts the timestamped copy" of the
data packet including IOAM TLVs when the node recognizes the IOAM
Indicator Label.
o The egress node also pops the IOAM Indicator Label and the IOAM
TLVs from the MPLS header.
4.1. IOAM Indicator Label
The IOAM Indicator Label can be a allocated using one of the
following methods:
o Label assigned by IANA with value TBA1.
o Label allocated by a controller from the global table of the
egress node. The controller provisions the label on both ingress
and egress nodes.
o Label allocated by the egress node from the global label table of
the egress node. The signaling extension for this is outside the
scope of this document.
4.2. Hashing Function
The ingress node needs to make sure the IOAM TLV does not start with
a well known protocol type (e.g. 0x4 for IPv4 and 0x6 for IPv6) and
does not alter the hashing function that uses the IP header.
Note that the hashing function that uses the label values from the
MPLS header may also now include the IOAM Indicator Label.
4.3. Node Capability
The egress node that has to pop the IOAM Indicator Label, TLVs, and
perform the IOAM function may not be capable of supporting it. The
ingress node needs to know if the egress node can support the IOAM
function. The signaling extension for this capability exchange is
outside the scope of this document.
5. 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
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value from the "Special-Purpose MPLS Label Values" registry:
+---------------+-------------------------+---------------+
| Value | Description | Reference |
+---------------+-------------------------+---------------+
| TBA1 | IOAM Indicator Label | This document |
+---------------+-------------------------+---------------+
6. 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.
7. Acknowledgements
The authors would like to thank Shwetha Bhandari and Vengada Prasad
Govindan for the discussions on IOAM.
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8. 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.
[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.
Contributors
Sagar Soni
Cisco Systems, Inc.
Email: sagsoni@cisco.com
Patrick Khordoc
Cisco Systems, Inc.
Email: pkhordoc@cisco.com
Authors' Addresses
Rakesh Gandhi (editor)
Cisco Systems, Inc.
Canada
Email: rgandhi@cisco.com
Zafar Ali
Cisco Systems, Inc.
Email: zali@cisco.com
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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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