Internet DRAFT - draft-liu-6man-max-header-size
draft-liu-6man-max-header-size
6MAN Y. Liu
Internet-Draft Y. Shen
Intended status: Informational ZTE
Expires: 21 April 2024 19 October 2023
IPv6 Maximum Header Size Requirement
draft-liu-6man-max-header-size-00
Abstract
This document proposes the concept and the requirement of IPv6
Maximum Header Size to represent the total header size that a node is
able to process from an incoming packet in IPv6, as well as the
requirement for it.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 21 April 2024.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Signaling Requirements . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
7.1. Normative References . . . . . . . . . . . . . . . . . . 4
7.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
In terms of packet processing, a device has various capabilities.
For IPv6 routers, one of the capabilities is the Maximum Header Size
that a node can read and process from an incoming packet. And the
Maximum Header Size include the IPv6 header and IPv6 extension
header.
The introduction of IPv6 extension headers especially SRH, has
increased the packet header size greatly. And the possibility of
combination of extension headers packets makes the situation worse.
Without the knowledge of the processing abilities of downstream
nodes, the total header size of the packets sent by the upstream may
exceed the Maximum Header Size that the downstreams can process,
which may cause the packets to be discarded.
Although for some network devices, even when the size of the header
accepted exceeds the header processing buffer of the device, they can
still try to process this packet by recycling, but it's an impact of
packet forwarding efficiency.
So for efficient packet forwarding, in many cases it's very important
to know the maximum header size that each downstream nodes is able to
process at full forwarding rate.
Although there're already some related works on packet processing
size, but they are not sufficient.
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The concept Maximum SID Depth (MSD) is originally introduced for SR-
MPLS to represent the number of SIDs supported by a node or a link on
a node. MSD is further extended for SRv6 as per [RFC9352]. This can
be collected via IS-IS [RFC8491], OSPF [RFC8476], BGP-LS [RFC8814],
or PCEP [RFC8664].
MSD types for SRv6 are related with the number of SRv6 SIDs, but
other components within SRH such as SRH TLVs are not in the scope of
MSD. Not to speak of other IPv6 extension headers.
Based on the considerations above, this document defines the term
"IPv6 Maximum Header Size", which means, the maximum packet size,
starting from the IPv6 header, that a node is able to process at full
forwarding rate from an incoming IPv6 packet. And the signaling
requirement is also included.
2. Conventions used in this document
2.1. Terminology
MSD: Maximum SID Depth as in [RFC8491].
Full Forwarding Rate: As in [I-D.ietf-6man-hbh-processing] this is
the rate that a router can forward packets without adversely
impacting the aggregate forwarding rate.
MPD: Maximum Packet Depth supported by a node or a link on a node.
2.2. 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.
3. Use Cases
The headend node can attach data on the packet.
For SRv6 IOAM pre-allocated trace, the headend attachs the hop-by-hop
options header with the IOAM data fields ahead of SRH as introduced
in [RFC9486].
In the case of SR service
programming[I-D.ietf-spring-sr-service-programming], the SRH Opaque
Metadata TLV and NSH Carrier TLV may be inserted by the headend.
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For network slicing purpose, the VTN Option in IPv6 Hop-by-Hop option
may be carried in the packet [I-D.ietf-6man-enhanced-vpn-vtn-id].
And all the above functions may be used in combination.
The intermediate nodes may increase the size of the packet. The IPv6
extension headers, as well as their TLVs may be attached by the
intermediate destination nodes(e.g SR Segment Endpoint nodes) via
inserting or tunneling. In this case it is very important for
attaching nodes to obtain the packet processing sizes of the
downstream nodes.
For an SR Segment Endpoint nodes with an End.B6.Encaps[RFC8986] SID
instantiated, it will push a new IPv6 header with its own SRH
containing an segment list above the original IPv6 header.
4. Signaling Requirements
Based on the usecases, there're requirements for the headend and
intermediate nodes to be aware of the IPv6 Maximum Header Size of
other nodes.
Considering of the exsiting works for MSD in IGP [RFC8491][RFC8476],
using IGP to advertise this capability at node and/or link
granularity is an feasible solution.
BGP-LS MAY also needed if there's an controller needs to collect this
information and it does not participate in IGP routing.
5. IANA Considerations
This document makes no request of IANA.
6. Security Considerations
TBD
7. References
7.1. Normative References
[I-D.ietf-6man-hbh-processing]
Hinden, R. M. and G. Fairhurst, "IPv6 Hop-by-Hop Options
Processing Procedures", Work in Progress, Internet-Draft,
draft-ietf-6man-hbh-processing-10, 26 September 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-6man-
hbh-processing-10>.
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[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>.
[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>.
7.2. Informative References
[I-D.ietf-6man-enhanced-vpn-vtn-id]
Dong, J., Li, Z., Xie, C., Ma, C., and G. S. Mishra,
"Carrying Virtual Transport Network (VTN) Information in
IPv6 Extension Header", Work in Progress, Internet-Draft,
draft-ietf-6man-enhanced-vpn-vtn-id-05, 6 July 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-6man-
enhanced-vpn-vtn-id-05>.
[I-D.ietf-spring-sr-service-programming]
Clad, F., Xu, X., Filsfils, C., Bernier, D., Li, C.,
Decraene, B., Ma, S., Yadlapalli, C., Henderickx, W., and
S. Salsano, "Service Programming with Segment Routing",
Work in Progress, Internet-Draft, draft-ietf-spring-sr-
service-programming-08, 21 August 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-spring-
sr-service-programming-08>.
[RFC8476] Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak,
"Signaling Maximum SID Depth (MSD) Using OSPF", RFC 8476,
DOI 10.17487/RFC8476, December 2018,
<https://www.rfc-editor.org/info/rfc8476>.
[RFC8491] Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg,
"Signaling Maximum SID Depth (MSD) Using IS-IS", RFC 8491,
DOI 10.17487/RFC8491, November 2018,
<https://www.rfc-editor.org/info/rfc8491>.
[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>.
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[RFC8814] Tantsura, J., Chunduri, U., Talaulikar, K., Mirsky, G.,
and N. Triantafillis, "Signaling Maximum SID Depth (MSD)
Using the Border Gateway Protocol - Link State", RFC 8814,
DOI 10.17487/RFC8814, August 2020,
<https://www.rfc-editor.org/info/rfc8814>.
[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/info/rfc8986>.
[RFC9352] Psenak, P., Ed., Filsfils, C., Bashandy, A., Decraene, B.,
and Z. Hu, "IS-IS Extensions to Support Segment Routing
over the IPv6 Data Plane", RFC 9352, DOI 10.17487/RFC9352,
February 2023, <https://www.rfc-editor.org/info/rfc9352>.
[RFC9486] Bhandari, S., Ed. and F. Brockners, Ed., "IPv6 Options for
In Situ Operations, Administration, and Maintenance
(IOAM)", RFC 9486, DOI 10.17487/RFC9486, September 2023,
<https://www.rfc-editor.org/info/rfc9486>.
Authors' Addresses
Yao Liu
ZTE
China
Email: liu.yao71@zte.com.cn
Yiming Shen
ZTE
China
Email: shen.yiming@zte.com.cn
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