draft-ietf-idr-sr-policy-path-mtu-01.txt   draft-ietf-idr-sr-policy-path-mtu-02.txt 
Interdomain Routing Working Group C. Li Interdomain Routing Working Group C. Li
Internet-Draft Huawei Technologies Internet-Draft Huawei Technologies
Intended status: Standards Track Y. Zhu Intended status: Standards Track Y. Zhu
Expires: October 30, 2020 China Telecom Expires: May 5, 2021 China Telecom
A. Sawaf A. Sawaf
Saudi Telecom Company Saudi Telecom Company
Z. Li Z. Li
Huawei Technologies Huawei Technologies
April 28, 2020 November 1, 2020
Segment Routing Path MTU in BGP Segment Routing Path MTU in BGP
draft-ietf-idr-sr-policy-path-mtu-01 draft-ietf-idr-sr-policy-path-mtu-02
Abstract Abstract
Segment Routing is a source routing paradigm that explicitly Segment Routing is a source routing paradigm that explicitly
indicates the forwarding path for packets at the ingress node. An SR indicates the forwarding path for packets at the ingress node. An SR
policy is a set of candidate SR paths consisting of one or more policy is a set of candidate SR paths consisting of one or more
segment lists with necessary path attributes. However, the path segment lists with necessary path attributes. However, the path
maximum transmission unit (MTU) information for SR path is not maximum transmission unit (MTU) information for SR path is not
available in the SR policy since the SR does not require signaling. available in the SR policy since the SR does not require signaling.
This document defines extensions to BGP to distribute path MTU This document defines extensions to BGP to distribute path MTU
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2.1. Requirements Language . . . . . . . . . . . . . . . . . . 5
3. SR Policy for Path MTU . . . . . . . . . . . . . . . . . . . 3 3. SR Policy for Path MTU . . . . . . . . . . . . . . . . . . . 5
3.1. Path MTU Sub-TLV . . . . . . . . . . . . . . . . . . . . 4 3.1. Path MTU Sub-TLV . . . . . . . . . . . . . . . . . . . . 6
4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Implementation Status . . . . . . . . . . . . . . . . . . . . 6 5. Implementation Status . . . . . . . . . . . . . . . . . . . . 7
5.1. Huawei's Commercial Delivery . . . . . . . . . . . . . . 6 5.1. Huawei's Commercial Delivery . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 7 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . 7 10.1. Normative References . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . 8 10.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
Segment routing (SR) [RFC8402] is a source routing paradigm that Segment routing (SR) [RFC8402] is a source routing paradigm that
explicitly indicates the forwarding path for packets at the ingress explicitly indicates the forwarding path for packets at the ingress
node. The ingress node steers packets into a specific path according node. The ingress node steers packets into a specific path according
to the Segment Routing Policy ( SR Policy) as defined in to the Segment Routing Policy ( SR Policy) as defined in
[I-D.ietf-spring-segment-routing-policy]. In order to distribute SR [I-D.ietf-spring-segment-routing-policy]. In order to distribute SR
policies to the headend, [I-D.ietf-idr-segment-routing-te-policy] policies to the headend, [I-D.ietf-idr-segment-routing-te-policy]
specifies a mechanism by using BGP. specifies a mechanism by using BGP.
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This document defines extensions to BGP to distribute path MTU This document defines extensions to BGP to distribute path MTU
information within SR policies. The Link MTU information can be information within SR policies. The Link MTU information can be
obtained via BGP-LS [I-D.zhu-idr-bgp-ls-path-mtu] or some other obtained via BGP-LS [I-D.zhu-idr-bgp-ls-path-mtu] or some other
means. With the Link MTU, the controller can compute the PMTU and means. With the Link MTU, the controller can compute the PMTU and
convey the information via the BGP SR policy. convey the information via the BGP SR policy.
2. Terminology 2. Terminology
This memo makes use of the terms defined in [RFC8402] and [RFC3209]. This memo makes use of the terms defined in [RFC8402] and [RFC3209].
MTU: Maximum Transmission Unit, the size in bytes of the largest IP
packet, including the IP header and payload, that can be
transmitted on a link or path. Note that this could more properly
be called the IP MTU, to be consistent with how other standards
organizations use the acronym MTU.
Link MTU: The Maximum Transmission Unit, i.e., maximum IP packet
size in bytes, that can be conveyed in one piece over a link. Be
aware that this definition is different from the definition used
by other standards organizations.
For IETF documents, link MTU is uniformly defined as the IP MTU
over the link. This includes the IP header, but excludes link
layer headers and other framing that is not part of IP or the IP
payload.
Be aware that other standards organizations generally define link
MTU to include the link layer headers.
For the MPLS data plane, this size includes the IP header and data (or
other payload) and the label stack but does not include any lower-layer
headers. A link may be an interface (such as Ethernet or Packet-over-
SONET), a tunnel (such as GRE or IPsec), or an LSP.
Path: The set of links traversed by a packet between a source node
and a destination node.
Path MTU, or PMTU: The minimum link MTU of all the links in a path
between a source node and a destination node.
For the MPLS data plane, it is the MTU of an LSP from a given LSR to
the egress(es), over each valid (forwarding) path. This size includes
the IP header and data (or other payload) and any part of the label
stack that was received by the ingress LSR before it placed the packet
into the LSP (this part of the label stack is considered part of the
payload for this LSP). The size does not include any lower-level
headers.
Note that: The PMTU value may be modified by subtracting some overhead
introduced by protection mechanism, like TI-LFA. Therefore, the value
of PMTU dilivered to the ingress node MAY be smaller than the minimum
link MTU of all the links in a path between a source node and a
destination node.
2.1. Requirements Language 2.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. SR Policy for Path MTU 3. SR Policy for Path MTU
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comments and help. comments and help.
10. References 10. References
10.1. Normative References 10.1. Normative References
[I-D.ietf-idr-segment-routing-te-policy] [I-D.ietf-idr-segment-routing-te-policy]
Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P., Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P.,
Rosen, E., Jain, D., and S. Lin, "Advertising Segment Rosen, E., Jain, D., and S. Lin, "Advertising Segment
Routing Policies in BGP", draft-ietf-idr-segment-routing- Routing Policies in BGP", draft-ietf-idr-segment-routing-
te-policy-08 (work in progress), November 2019. te-policy-09 (work in progress), May 2020.
[I-D.ietf-spring-segment-routing-policy] [I-D.ietf-spring-segment-routing-policy]
Filsfils, C., Sivabalan, S., Voyer, D., Bogdanov, A., and Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
P. Mattes, "Segment Routing Policy Architecture", draft- P. Mattes, "Segment Routing Policy Architecture", draft-
ietf-spring-segment-routing-policy-06 (work in progress), ietf-spring-segment-routing-policy-08 (work in progress),
December 2019. July 2020.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>. July 2018, <https://www.rfc-editor.org/info/rfc8402>.
10.2. Informative References 10.2. Informative References
[I-D.ietf-spring-mpls-path-segment] [I-D.ietf-spring-mpls-path-segment]
Cheng, W., Li, H., Chen, M., Gandhi, R., and R. Zigler, Cheng, W., Li, H., Chen, M., Gandhi, R., and R. Zigler,
"Path Segment in MPLS Based Segment Routing Network", "Path Segment in MPLS Based Segment Routing Network",
draft-ietf-spring-mpls-path-segment-02 (work in progress), draft-ietf-spring-mpls-path-segment-03 (work in progress),
February 2020. September 2020.
[I-D.li-spring-srv6-path-segment] [I-D.li-spring-srv6-path-segment]
Li, C., Cheng, W., Chen, M., Dhody, D., and R. Gandhi, Li, C., Cheng, W., Chen, M., Dhody, D., and R. Gandhi,
"Path Segment for SRv6 (Segment Routing in IPv6)", draft- "Path Segment for SRv6 (Segment Routing in IPv6)", draft-
li-spring-srv6-path-segment-05 (work in progress), March li-spring-srv6-path-segment-06 (work in progress),
2020. September 2020.
[I-D.zhu-idr-bgp-ls-path-mtu] [I-D.zhu-idr-bgp-ls-path-mtu]
Zhu, Y., Hu, Z., Yan, G., and J. Yao, "BGP-LS Extensions Zhu, Y., Hu, Z., Peng, S., and R. Mwehair, "BGP-LS
for Advertising Path MTU", draft-zhu-idr-bgp-ls-path- Extensions for Advertising Path MTU", draft-zhu-idr-bgp-
mtu-02 (work in progress), January 2020. ls-path-mtu-04 (work in progress), August 2020.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>. <https://www.rfc-editor.org/info/rfc3209>.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205, Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016, RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>. <https://www.rfc-editor.org/info/rfc7942>.
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