< draft-zhu-idr-bgp-ls-path-mtu-00.txt   draft-zhu-idr-bgp-ls-path-mtu-01.txt >
Network Working Group Y. Zhu Network Working Group Y. Zhu
Internet-Draft China Telecom Internet-Draft China Telecom
Intended status: Standards Track Z. Hu Intended status: Standards Track Z. Hu
Expires: January 1, 2019 G. Yan Expires: January 4, 2020 G. Yan
J. Yao J. Yao
Huawei Technologies Huawei Technologies
June 30, 2018 July 3, 2019
BGP-LS Extensions for Advertising Path MTU BGP-LS Extensions for Advertising Path MTU
draft-zhu-idr-bgp-ls-path-mtu-00 draft-zhu-idr-bgp-ls-path-mtu-01
Abstract Abstract
BGP Link State (BGP-LS) describes a mechanism by which link-state and BGP Link State (BGP-LS) describes a mechanism by which link-state and
TE information can be collected from networks and shared with TE information can be collected from networks and shared with
external components using the BGP routing protocol. The centralized external components using the BGP routing protocol. The centralized
controller (PCE/SDN) completes the service path calculation based on controller (PCE/SDN) completes the service path calculation based on
the information transmitted by the BGP-LS and delivers the result to the information transmitted by the BGP-LS and delivers the result to
the Path Computation Client (PCC) through the PCEP protocol. the Path Computation Client (PCC) through the PCEP or BGP protocol.
Segment Routing (SR) leverages the source routing paradigm, which can Segment Routing (SR) leverages the source routing paradigm, which can
be directly applied to the MPLS architecture with no change on the be directly applied to the MPLS architecture with no change on the
forwarding plane and applied to the IPv6 architecture, with a new forwarding plane and applied to the IPv6 architecture, with a new
type of routing header, called SRH. The SR uses the IGP protocol as type of routing header, called SRH. The SR uses the IGP protocol as
the control protocol. Compared to the MPLS tunneling technology, the the control protocol. Compared to the MPLS tunneling technology, the
SR does not require signaling. Therefore, the SR does not support SR does not require additional signaling. Therefore, the SR does not
the negotiation of the Path MTU. Since Multiple labels or SRv6 SIDs support the negotiation of the Path MTU. Since Multiple labels or
are pushed in the packets, it is more likely that the MTU exceeds the SRv6 SIDs are pushed in the packets, it is more likely that the
limit in the SR tunneling technology. packet size exceeds the path mtu of SR tunnel.
This document specify the extension to BGP Link State (BGP-LS) to This document specify the extension to BGP Link State (BGP-LS) to
carry maximum transmission unit (MTU) messages. The PCE/SDN carry maximum transmission unit (MTU) messages of link. The PCE/SDN
calculates the Path MTU while completing the service path calculation calculates the Path MTU while completing the service path calculation
based on the information transmitted by the BGP-LS. based on the information transmitted by the BGP-LS.
Requirements Language 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", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 1, 2019. This Internet-Draft will expire on January 4, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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directly applied to the MPLS architecture with no change on the directly applied to the MPLS architecture with no change on the
forwarding plane [I-D.ietf-spring-segment-routing-mpls] and applied forwarding plane [I-D.ietf-spring-segment-routing-mpls] and applied
to the IPv6 architecture with a new type of routing header called the to the IPv6 architecture with a new type of routing header called the
SR header (SRH) [I-D.ietf-6man-segment-routing-header]. SR header (SRH) [I-D.ietf-6man-segment-routing-header].
[I-D.ietf-idr-bgp-ls-segment-routing-ext] defines SR extensions to [I-D.ietf-idr-bgp-ls-segment-routing-ext] defines SR extensions to
BGP-LS and specifies the TLVs and sub-TLVs for advertising SR BGP-LS and specifies the TLVs and sub-TLVs for advertising SR
information. Based on the SR information reported by the BGP-LS, the information. Based on the SR information reported by the BGP-LS, the
SDN can calculate the end-to-end explicit SR-TE paths or SR Policies. SDN can calculate the end-to-end explicit SR-TE paths or SR Policies.
Nevertheless, Segment Routing is a tunneling technology based on the Nevertheless, Segment Routing is a tunneling technology based on the
IGP protocol as the control protocol, and there is no signaling for IGP protocol as the control protocol, and there is no additional
establishing the path. so the Segment Routing tunnel cannot currently signaling for establishing the path. so the Segment Routing tunnel
support the negotiation mechanism of the MTU. Multiple labels or cannot currently support the negotiation mechanism of the MTU.
SRv6 SIDs are pushed in the packets. This causes the length of the Multiple labels or SRv6 SIDs are pushed in the packets. This causes
packets encapsulated in the Segment Routing tunnel to increase during the length of the packets encapsulated in the Segment Routing tunnel
packet forwarding. This is more likely to cause MTU overrun than to increase during packet forwarding. This is more likely to cause
traditional MPLS. packet size exceed than traditional MPLS packet size.
This document specify the extension to BGP Link State (BGP-LS) to This document specify the extension to BGP Link State (BGP-LS) to
carry maximum transmission unit (MTU) messages. carry link maximum transmission unit (MTU) messages.
2. Deploying scenarios 2. Deploying scenarios
This document suggests a solution to extension to BGP Link State This document suggests a solution to extension to BGP Link State
(BGP-LS) to carry maximum transmission unit (MTU) messages. The MTU (BGP-LS) to carry maximum transmission unit (MTU) messages. The MTU
information of the link is acquired through the process of collecting information of the link is acquired through the process of collecting
link state and TE information by BGP-LS. Concretely, a router link state and TE information by BGP-LS. Concretely, a router
maintains one or more databases for storing link-state information maintains one or more databases for storing link-state information
about nodes and links in any given area. The router's BGP process about nodes and links in any given area. The router's BGP process
can retrieve topology from these LSDBs and distribute it to a can retrieve topology from these LSDBs and distribute it to a
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7.1. Normative References 7.1. Normative References
[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>.
7.2. Informative References 7.2. Informative References
[I-D.ietf-6man-segment-routing-header] [I-D.ietf-6man-segment-routing-header]
Filsfils, C., Previdi, S., Leddy, J., Matsushima, S., and Filsfils, C., Dukes, D., Previdi, S., Leddy, J.,
d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header Matsushima, S., and d. daniel.voyer@bell.ca, "IPv6 Segment
(SRH)", draft-ietf-6man-segment-routing-header-14 (work in Routing Header (SRH)", draft-ietf-6man-segment-routing-
progress), June 2018. header-21 (work in progress), June 2019.
[I-D.ietf-idr-bgp-ls-segment-routing-ext] [I-D.ietf-idr-bgp-ls-segment-routing-ext]
Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H., Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H.,
and M. Chen, "BGP Link-State extensions for Segment and M. Chen, "BGP Link-State extensions for Segment
Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-08 Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-16
(work in progress), May 2018. (work in progress), June 2019.
[I-D.ietf-spring-segment-routing] [I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B., Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing Litkowski, S., and R. Shakir, "Segment Routing
Architecture", draft-ietf-spring-segment-routing-15 (work Architecture", draft-ietf-spring-segment-routing-15 (work
in progress), January 2018. in progress), January 2018.
[I-D.ietf-spring-segment-routing-mpls] [I-D.ietf-spring-segment-routing-mpls]
Bashandy, A., Filsfils, C., Previdi, S., Decraene, B., Bashandy, A., Filsfils, C., Previdi, S., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing with MPLS Litkowski, S., and R. Shakir, "Segment Routing with MPLS
data plane", draft-ietf-spring-segment-routing-mpls-14 data plane", draft-ietf-spring-segment-routing-mpls-22
(work in progress), June 2018. (work in progress), May 2019.
[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, [RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
DOI 10.17487/RFC1191, November 1990, DOI 10.17487/RFC1191, November 1990,
<https://www.rfc-editor.org/info/rfc1191>. <https://www.rfc-editor.org/info/rfc1191>.
[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>.
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