draft-ietf-spring-segment-routing-msdc-07.txt   draft-ietf-spring-segment-routing-msdc-08.txt 
Network Working Group C. Filsfils, Ed. Network Working Group C. Filsfils, Ed.
Internet-Draft S. Previdi Internet-Draft S. Previdi
Intended status: Informational Cisco Systems, Inc. Intended status: Informational Cisco Systems, Inc.
Expires: June 22, 2018 J. Mitchell Expires: June 24, 2018 J. Mitchell
Unaffiliated Unaffiliated
E. Aries E. Aries
Juniper Networks Juniper Networks
P. Lapukhov P. Lapukhov
Facebook Facebook
December 19, 2017 December 21, 2017
BGP-Prefix Segment in large-scale data centers BGP-Prefix Segment in large-scale data centers
draft-ietf-spring-segment-routing-msdc-07 draft-ietf-spring-segment-routing-msdc-08
Abstract Abstract
This document describes the motivation and benefits for applying This document describes the motivation and benefits for applying
segment routing in BGP-based large-scale data-centers. It describes segment routing in BGP-based large-scale data-centers. It describes
the design to deploy segment routing in those data-centers, for both the design to deploy segment routing in those data-centers, for both
the MPLS and IPv6 dataplanes. the MPLS and IPv6 dataplanes.
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-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
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 June 22, 2018. This Internet-Draft will expire on June 24, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 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
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2.1. Reference design . . . . . . . . . . . . . . . . . . . . 4 2.1. Reference design . . . . . . . . . . . . . . . . . . . . 4
3. Some open problems in large data-center networks . . . . . . 5 3. Some open problems in large data-center networks . . . . . . 5
4. Applying Segment Routing in the DC with MPLS dataplane . . . 6 4. Applying Segment Routing in the DC with MPLS dataplane . . . 6
4.1. BGP Prefix Segment (BGP-Prefix-SID) . . . . . . . . . . . 6 4.1. BGP Prefix Segment (BGP-Prefix-SID) . . . . . . . . . . . 6
4.2. eBGP Labeled Unicast (RFC8277) . . . . . . . . . . . . . 6 4.2. eBGP Labeled Unicast (RFC8277) . . . . . . . . . . . . . 6
4.2.1. Control Plane . . . . . . . . . . . . . . . . . . . . 7 4.2.1. Control Plane . . . . . . . . . . . . . . . . . . . . 7
4.2.2. Data Plane . . . . . . . . . . . . . . . . . . . . . 9 4.2.2. Data Plane . . . . . . . . . . . . . . . . . . . . . 9
4.2.3. Network Design Variation . . . . . . . . . . . . . . 10 4.2.3. Network Design Variation . . . . . . . . . . . . . . 10
4.2.4. Global BGP Prefix Segment through the fabric . . . . 10 4.2.4. Global BGP Prefix Segment through the fabric . . . . 10
4.2.5. Incremental Deployments . . . . . . . . . . . . . . . 11 4.2.5. Incremental Deployments . . . . . . . . . . . . . . . 11
4.3. iBGP Labeled Unicast (draft-ietf-mpls-rfc3107bis) . . . . 12 4.3. iBGP Labeled Unicast (RFC8277) . . . . . . . . . . . . . 12
5. Applying Segment Routing in the DC with IPv6 dataplane . . . 14 5. Applying Segment Routing in the DC with IPv6 dataplane . . . 14
6. Communicating path information to the host . . . . . . . . . 14 6. Communicating path information to the host . . . . . . . . . 14
7. Addressing the open problems . . . . . . . . . . . . . . . . 15 7. Addressing the open problems . . . . . . . . . . . . . . . . 15
7.1. Per-packet and flowlet switching . . . . . . . . . . . . 15 7.1. Per-packet and flowlet switching . . . . . . . . . . . . 15
7.2. Performance-aware routing . . . . . . . . . . . . . . . . 16 7.2. Performance-aware routing . . . . . . . . . . . . . . . . 16
7.3. Deterministic network probing . . . . . . . . . . . . . . 17 7.3. Deterministic network probing . . . . . . . . . . . . . . 17
8. Additional Benefits . . . . . . . . . . . . . . . . . . . . . 17 8. Additional Benefits . . . . . . . . . . . . . . . . . . . . . 17
8.1. MPLS Dataplane with operational simplicity . . . . . . . 18 8.1. MPLS Dataplane with operational simplicity . . . . . . . 18
8.2. Minimizing the FIB table . . . . . . . . . . . . . . . . 18 8.2. Minimizing the FIB table . . . . . . . . . . . . . . . . 18
8.3. Egress Peer Engineering . . . . . . . . . . . . . . . . . 18 8.3. Egress Peer Engineering . . . . . . . . . . . . . . . . . 18
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Figure 8: Node4 Forwarding Table Figure 8: Node4 Forwarding Table
The BGP-Prefix-SID can thus be deployed incrementally one node at a The BGP-Prefix-SID can thus be deployed incrementally one node at a
time. time.
When deployed together with a homogeneous SRGB (same SRGB across the When deployed together with a homogeneous SRGB (same SRGB across the
fabric), the operator incrementally enjoys the global prefix segment fabric), the operator incrementally enjoys the global prefix segment
benefits as the deployment progresses through the fabric. benefits as the deployment progresses through the fabric.
4.3. iBGP Labeled Unicast (draft-ietf-mpls-rfc3107bis) 4.3. iBGP Labeled Unicast (RFC8277)
The same exact design as eBGP8277 is used with the following The same exact design as eBGP8277 is used with the following
modifications: modifications:
All nodes use the same AS number. All nodes use the same AS number.
Each node peers with its neighbors via an internal BGP session Each node peers with its neighbors via an internal BGP session
(iBGP) with extensions defined in [RFC8277] (named "iBGP8277" (iBGP) with extensions defined in [RFC8277] (named "iBGP8277"
throughout this document). throughout this document).
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the possible paths, knowing exactly which links and devices these the possible paths, knowing exactly which links and devices these
packets will be crossing. Correlating results for multiple packets will be crossing. Correlating results for multiple
destinations with the topological data, it may automatically isolate destinations with the topological data, it may automatically isolate
possible problem to a link or device in the network. possible problem to a link or device in the network.
8. Additional Benefits 8. Additional Benefits
8.1. MPLS Dataplane with operational simplicity 8.1. MPLS Dataplane with operational simplicity
As required by [RFC7938], no new signaling protocol is introduced. As required by [RFC7938], no new signaling protocol is introduced.
The BGP-Prefix-SID is a lightweight extension to BGP Labeled Unicast The BGP-Prefix-SID is a lightweight extension to BGP Labeled Unicast
(RFC8277 [RFC8277]). It applies either to eBGP or iBGP based [RFC8277]. It applies either to eBGP or iBGP based designs.
designs.
Specifically, LDP and RSVP-TE are not used. These protocols would Specifically, LDP and RSVP-TE are not used. These protocols would
drastically impact the operational complexity of the Data Center and drastically impact the operational complexity of the Data Center and
would not scale. This is in line with the requirements expressed in would not scale. This is in line with the requirements expressed in
[RFC7938]. [RFC7938].
Provided the same SRGB is configured on all nodes, all nodes use the Provided the same SRGB is configured on all nodes, all nodes use the
same MPLS label for a given IP prefix. This is simpler from an same MPLS label for a given IP prefix. This is simpler from an
operation standpoint, as discussed in Section 9 operation standpoint, as discussed in Section 9
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[I-D.ietf-idr-bgp-prefix-sid] [I-D.ietf-idr-bgp-prefix-sid]
Previdi, S., Filsfils, C., Lindem, A., Sreekantiah, A., Previdi, S., Filsfils, C., Lindem, A., Sreekantiah, A.,
and H. Gredler, "Segment Routing Prefix SID extensions for and H. Gredler, "Segment Routing Prefix SID extensions for
BGP", draft-ietf-idr-bgp-prefix-sid-07 (work in progress), BGP", draft-ietf-idr-bgp-prefix-sid-07 (work in progress),
October 2017. October 2017.
[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-13 (work Architecture", draft-ietf-spring-segment-routing-14 (work
in progress), October 2017. in progress), December 2017.
[I-D.ietf-spring-segment-routing-central-epe] [I-D.ietf-spring-segment-routing-central-epe]
Filsfils, C., Previdi, S., Dawra, G., Aries, E., and D. Filsfils, C., Previdi, S., Dawra, G., Aries, E., and D.
Afanasiev, "Segment Routing Centralized BGP Egress Peer Afanasiev, "Segment Routing Centralized BGP Egress Peer
Engineering", draft-ietf-spring-segment-routing-central- Engineering", draft-ietf-spring-segment-routing-central-
epe-07 (work in progress), October 2017. epe-10 (work in progress), December 2017.
[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>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271, Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006, DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>. <https://www.rfc-editor.org/info/rfc4271>.
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