bier Z. Zhang
Internet-Draft Juniper Networks
Intended status: Standards Track X. Min
Expires: 28 July 2024 ZTE
Y. Liu
China Mobile
H. Bidgoli
Nokia
25 January 2024
BIER Extension Headers
draft-zzhang-bier-extension-headers-02.txt
Abstract
Bit Index Explicit Replication (BIER) is a multicast technology with
a new encapsulation and forwarding paradigm. BIER encapsulation is
specified in RFC8296, and this document specifies extension headers
used with BIER encapsulation 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 28 July 2024.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
Zhang, et al. Expires 28 July 2024 [Page 1]
Internet-Draft BIER Extension Headers January 2024
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Background . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Specifications . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. BIER Encapsulation with Extension Headers . . . . . . . . 3
2.2. Extension Top Header . . . . . . . . . . . . . . . . . . 4
2.3. Extension Header Format . . . . . . . . . . . . . . . . . 5
3. Security Considerations . . . . . . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Normative References . . . . . . . . . . . . . . . . . . 6
5.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Background
[RFC8296] specifies BIER encapsulation header as following:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|OAM|Rsv| DSCP | Proto | BFIR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BitString (first 32 bits) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ BitString (last 32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The header is fixed format, making it difficult to extend for
additional functionalities.
[I-D.xzlnp-bier-ioam] describes In-situ Operations, Administration,
and Maintenance (IOAM) functionality for BIER, and proposes a way to
extend the BIER header to encode IOAM data as well as other potential
extension headers.
Zhang, et al. Expires 28 July 2024 [Page 2]
Internet-Draft BIER Extension Headers January 2024
[I-D.zzhang-intarea-generic-delivery-functions] considers Generic
Delivery Functions (GDFs, e.g., fragmentation, security, IOAM) that
can be applied to various layers (e.g., MPLS, IPv6, BIER) and
proposes a slightly different extension header mechanism that is
aligned with [I-D.song-mpls-extension-header] and work for both MPLS,
BIER, and potentially other layers.
[] is not adopted in the MPLS WG.
[I-D.jags-mpls-ps-mna-hdr] is the candidate solution, and the main
difference is that the "next header" concept is no longer used, which
means that IPv6 extension headers for GDFs can not be used as is.
However, other than that it takes a different way to get to the
ancillary data used for the functions, the data itself and the
handling can still be generic.
To align BIER and MPLS for a generic solution, this document now
takes the approach in [I-D.jags-mpls-ps-mna-hdr] for discussions and
progressing in the BIER WG.
2. Specifications
2.1. BIER Encapsulation with Extension Headers
The following figure illustrates a BIER header with extension
headers.
A TBD value for the "proto" field in the BIER header indicates that
some BIER Extension Headers follow the BIER header and precede the
BIER payload. An extension header could be an IPv6 one for a GDF
like IOAM, even though this is not an IPv6 protocol layer.
Zhang, et al. Expires 28 July 2024 [Page 3]
Internet-Draft BIER Extension Headers January 2024
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|OAM|R|H| DSCP | Proto=TBD | BFIR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BitString (first 32 bits) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ BitString (last 32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extension Top Header |
+---------------------------------------------------------------+
~ Extension Header (EH) 1 ~
+---------------------------------------------------------------+
~ ... ~
+---------------------------------------------------------------+
~ Extension Header (EH) N ~
+---------------------------------------------------------------+
~ Upper Layer Headers/Payload ~
+---------------------------------------------------------------+
R: The "R" flag bit is reserved. It MUST be set to 0 on transmission
and ignored on reception.
H: If the "H" flag bit is set, it indicates the presence of at least
one extension header that needs to be processed hop by hop even
before a BFER is reached.
2.2. Extension Top Header
The Extension Top Header (ETH) encoding is as following:
Zhang, et al. Expires 28 July 2024 [Page 4]
Internet-Draft BIER Extension Headers January 2024
0 1 2 3
0123456789012345 67890123 45678901
+--------------+-+--------+--------+
| Reserved |P| EHTL | NH |
+--------------+-+--------+--------+
Reserved: Reserved field.
P: 1-bit flag indicating the type of the NH field.
EHTL: 8-bit unsigned integer for the Extension Header Total Length
in 4-octet units. This field keeps the total length of the
extension headers in this packet, not including the ETH itself.
NH: 8-bit selector for the Next Header. This field identifies the
type of the header following the final extension header.
If the P-flag is set, the value is from the Internet Protocol
Numbers registry. If the P-flag is not set, the value is from
BIER's own protocol registry number registry, which is now
extended from the original 6-bit to 8-bit. Note that only
the first 64 values from the original registry can be used
in the Proto field in the base BIER header. If a larger value
is needed, the ETH MUST be used (with or without some Extension
Headers).
A BIER capable router is smart enough to interpret the data afer the
base BIER header only according to the Proto field, so there is no
need to reserve a nibble at the begining of ETH to distinguish from
an IP header.
2.3. Extension Header Format
The format of a BIER Extension Header (EH) mimics the MPLS Post-Stack
Network Action Header [I-D.jags-mpls-ps-mna-hdr] (assuming the MPLS
format will be updated to put its equivalent of EH-DATA at the end of
the first word):
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EH-OP |R|R| EH-Len | EH-DATA ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
EH-OP: 7-bit OP Code for the extension. RR: 2-bit reserved field.
EH-LEN: 7-bit unsigned integer for the Extension Header Length in
4-octet units, not including the first four octets.
Zhang, et al. Expires 28 July 2024 [Page 5]
Internet-Draft BIER Extension Headers January 2024
EH-Data:Data for the extension header. The first two octets are not
counted in the EH-Len.
3. Security Considerations
To be provided.
4. IANA Considerations
The following IANA actions are requested.
* Assign a "BIER Extension Header" value from the "BIER Next
Protocol Identifiers" registry for the "proto" field in a BIER
header.
* Create a "BIER Extension Header OP Codes" registry for the "EH-OP"
field in a BIER specific extension header.
5. References
5.1. Normative References
[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>.
5.2. Informative References
[I-D.jags-mpls-ps-mna-hdr]
Rajamanickam, J., Gandhi, R., Zigler, R., Li, T., and J.
Dong, "Post-Stack MPLS Network Action (MNA) Solution",
Work in Progress, Internet-Draft, draft-jags-mpls-ps-mna-
hdr-01, 21 October 2023,
<https://datatracker.ietf.org/doc/html/draft-jags-mpls-ps-
mna-hdr-01>.
[]
Song, H., Zhou, T., Andersson, L., Zhang, Z. J., and R.
Gandhi, "MPLS Network Actions using Post-Stack Extension
Headers", Work in Progress, Internet-Draft, draft-song-
mpls-extension-header-13, 11 October 2023,
<https://datatracker.ietf.org/doc/html/draft-song-mpls-
extension-header-13>.
Zhang, et al. Expires 28 July 2024 [Page 6]
Internet-Draft BIER Extension Headers January 2024
[I-D.xzlnp-bier-ioam]
Min, X., Zhang, Z., Liu, Y., Nainar, N. K., and C.
Pignataro, "BIER Encapsulation for IOAM Data", Work in
Progress, Internet-Draft, draft-xzlnp-bier-ioam-06, 31
July 2023, <https://datatracker.ietf.org/doc/html/draft-
xzlnp-bier-ioam-06>.
[I-D.zzhang-intarea-generic-delivery-functions]
Zhang, Z. J., Bonica, R., Kompella, K., and G. Mirsky,
"Generic Delivery Functions", Work in Progress, Internet-
Draft, draft-zzhang-intarea-generic-delivery-functions-03,
11 July 2022, <https://datatracker.ietf.org/doc/html/
draft-zzhang-intarea-generic-delivery-functions-03>.
Authors' Addresses
Zhaohui Zhang
Juniper Networks
Email: zzhang@juniper.net
Xiao Min
ZTE
Email: xiao.min2@zte.com.cn
Yisong Liu
China Mobile
Email: liuyisong@chinamobile.com
Hooman Bidgoli
Nokia
Email: hooman.bidgoli@nokia.com
Zhang, et al. Expires 28 July 2024 [Page 7]