BIER Working Group X. Min
Internet-Draft Z. Zhang
Intended status: Standards Track ZTE Corp.
Expires: 26 January 2023 Y. Liu
China Mobile
N. Nainar
C. Pignataro
Cisco Systems, Inc.
25 July 2022
Bit Index Explicit Replication (BIER) Encapsulation for In-situ OAM
(IOAM) Data
draft-xzlnp-bier-ioam-04
Abstract
In-situ Operations, Administration, and Maintenance (IOAM) records
operational and telemetry information in the packet while the packet
traverses a path in the network. Bit Index Explicit Replication
(BIER) is an architecture that provides optimal multicast forwarding
through a "multicast domain", without requiring intermediate routers
to maintain any per-flow state or to engage in an explicit tree-
building protocol. The BIER header contains a bit-string in which
each bit represents exactly one egress router to forward the packet
to. This document outlines the requirements to carry IOAM data in
BIER header and specifies how IOAM data fields are encapsulated in
BIER header.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 26 January 2023.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
3. Requirements to carry IOAM data . . . . . . . . . . . . . . . 3
4. IOAM data fields encapsulation in BIER header . . . . . . . . 4
5. Considerations . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Selecting the encapsulation approach . . . . . . . . . . 6
5.2. Interaction with the BIER OAM field . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
In-situ Operations, Administration, and Maintenance (IOAM) records
operational and telemetry information in the packet while the packet
traverses a path in the network. [RFC9197] defines multiple IOAM
options with different IOAM data fields used to record various
telemetry data from the transit nodes.
[I-D.ietf-ippm-ioam-direct-export] defines IOAM Direct Export option
with IOAM data fields, which indicate telemetry data to be collected
without being embedded in data packets. The term "in-situ" refers to
the fact that the OAM data is added to the data packets rather than
being sent within packets specifically dedicated to OAM.
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Bit Index Explicit Replication (BIER), as defined in [RFC8279], is an
architecture that provides optimal multicast forwarding through a
"multicast domain", without requiring intermediate routers to
maintain any per-flow state or to engage in an explicit tree-building
protocol. The BIER header, as defined in [RFC8296], contains a bit-
string in which each bit represents exactly one egress router to
forward the packet to.
This document outlines the requirements to carry IOAM data in BIER
header and specifies how IOAM data fields are encapsulated in BIER
header.
2. Conventions Used in This Document
2.1. 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.
2.2. Abbreviations
Abbreviations used in this document:
BFER: Bit Forwarding Egress Router
BFIR: Bit Forwarding Ingress Router
BIER: Bit Index Explicit Replication
GRE: Generic Routing Encapsulation
IOAM: In-situ Operations, Administration, and Maintenance
OAM: Operations, Administration, and Maintenance
3. Requirements to carry IOAM data
[I-D.ietf-bier-use-cases] lists many use cases for BIER. Usually
there are many multicast flows within one network domain, and some of
the multicast flows, such as live video and real-time meeting, are
sensitive to packet loss, delay and other factors. The network
operator wants to know the real-time statistics for these flows, such
as delay, sequence, the ingress/egress interface, and the usage of
buffer.
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So methods are needed for measuring the real-time transportation
guarantee of BIER packets. This document attempts to provide a way
to record operational and telemetry information in the BIER packets
through in-situ OAM.
4. IOAM data fields encapsulation in BIER header
The BIER header is defined in [RFC8279]. The BIER OAM header that
follows BIER header is defined in [I-D.ietf-bier-ping]. IOAM-Data-
Fields can either be carried in BIER using a new type of OAM message
which follows the BIER OAM header (referred to as option 1), or be
carried in BIER using a new next protocol header which immediately
follows the BIER header (referred to as option 2). In this document,
option 2 is selected and the reason is discussed in Section 5.1. An
IOAM header is added containing different IOAM-Data-Fields defined in
[RFC9197] and [I-D.ietf-ippm-ioam-direct-export].
In a BIER domain where IOAM is applied, inserting the IOAM header
into BIER packets is enabled at the BFIRs, which also serve as IOAM
encapsulating nodes by means of configuration, and deleting the IOAM
header from BIER packets is enabled at the BFERs, which also serve as
IOAM decapsulating nodes by means of configuration.
The Encapsulation format for IOAM over BIER is defined as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
| BIFT-id | TC |S| TTL | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
|Nibble | Ver | BSL | Entropy | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ B
|OAM|Rsv| DSCP |Proto=TBA1 | BFIR-id | I
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ E
| BitString (first 32 bits) ~ R
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
~ ~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
~ BitString (last 32 bits) | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
| IOAM-Type | IOAM HDR Len | Reserved | Next Proto| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ I
| | O
| | A
~ IOAM Option and Data Space ~ M
| | |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
| |
| |
| Payload + Padding (L2/L3/...) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: IOAM Encapsulation Format within BIER
The BIER header and fields are defined in [RFC8296]. Within the BIER
header, a 6-bit field as "Proto" (Next Protocol) is used to identify
the type of the payload immediately following the BIER header, The
"Proto" value is set to TBA1 when the IOAM header is present.
The IOAM related fields in BIER are defined as follows:
IOAM-Type: An 8-bit field defining the IOAM option type, as
defined in Section 7.1 of [RFC9197] and Section 4.1 of
[I-D.ietf-ippm-ioam-direct-export].
IOAM HDR Len: An 8-bit unsigned integer. Length of the IOAM
header in 4-octet units.
Reserved: A 10-bit reserved field MUST be set to zero upon
transmission and ignored upon receipt.
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Next Proto: A 6-bit unsigned integer that identifies the type of
payload immediately following this IOAM option. The semantics of
this field are identical to the "Proto" field in [RFC8296].
IOAM Option and Data Space: IOAM option header and data is present
as specified by the IOAM-Type field, and is defined in Section 4
of [RFC9197] and Section 3 of [I-D.ietf-ippm-ioam-direct-export].
Multiple IOAM options MAY be included within a BIER encapsulation.
For example, if a BIER encapsulation contains two IOAM options
preceding a data payload, the "Next Proto" field of the first IOAM
option would be set to the value of TBA1 that indicates a second IOAM
option follows, while the "Next Proto" field of the second IOAM
option would be set to the value of "BIER Next Protocol" indicating
the type of the data payload. Each type of IOAM option MUST occur at
most once within a BIER encapsulation.
5. Considerations
This section summarizes a set of considerations on the overall
approach taken for IOAM data encapsulation in BIER, as well as
deployment considerations.
5.1. Selecting the encapsulation approach
Both the options described in Section 4 are supposed to be feasible,
nevertheless this document needs to select one as standardized
encapsulation for IOAM over BIER. Considering the fact that the
encapsulation format option 2 using a new next protocol header is
more concise than option 1 using a new type of OAM message, and many
other transport protocols, e.g., GRE, use a new next protocol header
to encapsulate IOAM data, the encapsulation format option 2 is
selected as the standardized one.
5.2. Interaction with the BIER OAM field
[RFC8296] defines a two-bit field, referred to as OAM.
[I-D.ietf-bier-pmmm-oam] describes how to use the two-bit OAM field
for alternate marking performance measurement method. This document
would not change the semantics of the two-bit OAM field. The BIER
IOAM header and the BIER OAM field are orthogonal and they can co-
exist in one packet, i.e., a BIER packet with IOAM data can set the
OAM field and a BIER packet with OAM field set can carry IOAM data
too.
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6. Security Considerations
This document describes the encapsulation of IOAM data fields in
BIER. Security considerations of the specific IOAM data fields are
described in [RFC9197] and [I-D.ietf-ippm-ioam-direct-export].
IOAM is considered a "per domain" feature, where one or several
operators decide on configuring IOAM according to their needs. IOAM
is intended for deployment in limited domains [RFC8799]. As such, it
assumes that a node involved in IOAM operation has previously
verified the integrity of the path. Still, operators need to
properly secure the IOAM domain to avoid malicious configuration and
use, which could include injecting malicious IOAM packets into the
domain.
As this document describes new protocol fields within the existing
BIER encapsulation, these are similar to the security considerations
of [RFC8296].
7. IANA Considerations
In the "BIER Next Protocol Identifiers" registry created for
[RFC8296], a new Next Protocol Value for IOAM is requested from IANA
as follows:
+====================+=============+============+===========+
| BIER Next Protocol | Description | Semantics | Reference |
| Identifier | | Definition | |
+====================+=============+============+===========+
| TBA1 | In-situ OAM | Section 4 | This |
| | (IOAM) | | Document |
+--------------------+-------------+------------+-----------+
Table 1: New BIER Next Protocol Identifier
8. Acknowledgements
The authors would like to acknowledge Greg Mirsky for his thorough
review and very helpful comments.
9. References
9.1. Normative References
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[I-D.ietf-ippm-ioam-direct-export]
Song, H., Gafni, B., Brockners, F., Bhandari, S., and T.
Mizrahi, "In-situ OAM Direct Exporting", Work in Progress,
Internet-Draft, draft-ietf-ippm-ioam-direct-export-09, 15
June 2022, <https://www.ietf.org/archive/id/draft-ietf-
ippm-ioam-direct-export-09.txt>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", DOI 10.17487/RFC2119, BCP 14,
RFC 2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", DOI 10.17487/RFC8174, RFC 8174, BCP 14,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
Explicit Replication (BIER)", RFC 8279,
DOI 10.17487/RFC8279, November 2017,
<https://www.rfc-editor.org/info/rfc8279>.
[RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation
for Bit Index Explicit Replication (BIER) in MPLS and Non-
MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January
2018, <https://www.rfc-editor.org/info/rfc8296>.
[RFC9197] Brockners, F., Ed., Bhandari, S., Ed., and T. Mizrahi,
Ed., "Data Fields for In Situ Operations, Administration,
and Maintenance (IOAM)", DOI 10.17487/RFC9197, RFC 9197,
May 2022, <https://www.rfc-editor.org/info/rfc9197>.
9.2. Informative References
[I-D.ietf-bier-ping]
Kumar, N., Pignataro, C., Akiya, N., Zheng, L., Chen, M.,
and G. Mirsky, "BIER Ping and Trace", Work in Progress,
Internet-Draft, draft-ietf-bier-ping-07, 11 May 2020,
<https://www.ietf.org/archive/id/draft-ietf-bier-ping-
07.txt>.
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[I-D.ietf-bier-pmmm-oam]
Mirsky, G., Zheng, L., Chen, M., and G. Fioccola,
"Performance Measurement (PM) with Marking Method in Bit
Index Explicit Replication (BIER) Layer", Work in
Progress, Internet-Draft, draft-ietf-bier-pmmm-oam-12, 31
March 2022, <https://www.ietf.org/archive/id/draft-ietf-
bier-pmmm-oam-12.txt>.
[I-D.ietf-bier-use-cases]
Kumar, N., Asati, R., Chen, M., Xu, X., Dolganow, A.,
Przygienda, T., Gulko, A., Robinson, D., Arya, V., and C.
Bestler, "BIER Use Cases", Work in Progress, Internet-
Draft, draft-ietf-bier-use-cases-12, 10 September 2020,
<https://www.ietf.org/archive/id/draft-ietf-bier-use-
cases-12.txt>.
[RFC8799] Carpenter, B. and B. Liu, "Limited Domains and Internet
Protocols", RFC 8799, DOI 10.17487/RFC8799, July 2020,
<https://www.rfc-editor.org/info/rfc8799>.
Authors' Addresses
Xiao Min
ZTE Corp.
Nanjing
China
Email: xiao.min2@zte.com.cn
Zheng(Sandy) Zhang
ZTE Corp.
Nanjing
China
Email: zhang.zheng@zte.com.cn
Yisong Liu
China Mobile
Beijing
China
Email: liuyisong@chinamobile.com
Nagendra Kumar Nainar
Cisco Systems, Inc.
7200-11 Kit Creek Road
Research Triangle Park, NC 27709
United States of America
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Email: naikumar@cisco.com
Carlos Pignataro
Cisco Systems, Inc.
7200-11 Kit Creek Road
Research Triangle Park, NC 27709
United States of America
Email: cpignata@cisco.com
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