BGP-LS Extensions for Inter-As TE using EPE based mechanisms
draft-hegde-idr-bgp-ls-epe-inter-as-00
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| Authors | Shraddha Hegde , Srihari R. Sangli | ||
| Last updated | 2019-03-11 | ||
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draft-hegde-idr-bgp-ls-epe-inter-as-00
SPRING S. Hegde
Internet-Draft S. Sangli
Intended status: Standards Track Juniper Networks Inc.
Expires: September 12, 2019 March 11, 2019
BGP-LS Extensions for Inter-As TE using EPE based mechanisms
draft-hegde-idr-bgp-ls-epe-inter-as-00
Abstract
In certain network deployments, a single operator has multiple
Autonomous Systems(AS) to facilitate ease of management. A multiple
AS network design could also be a result of network mergers and
acquisitions. In such scenarios, a centralized Inter-domain TE
approach could provide most optimal allocation of resources and the
most controlled path placement. BGP-LS-EPE
[I-D.ietf-idr-bgpls-segment-routing-epe]describes an extension to BGP
Link State (BGP-LS) for the advertisement of BGP Peering Segments
along with their BGP peering node and inter-AS link information so
that efficient BGP Egress Peer Engineering (EPE) policies and
strategies can be computed based on Segment Routing. This document
describes extensions to the BGP-LS EPE to enable it to be used for
inter-AS Traffic-Engineering (TE) purposes.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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
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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 September 12, 2019.
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Internet-Draft BGP-LS extensions for Inter-AS TE using EPE March 2019
Copyright Notice
Copyright (c) 2019 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
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Reference Topology . . . . . . . . . . . . . . . . . . . . . 3
3. Fast Reroute Label . . . . . . . . . . . . . . . . . . . . . 4
4. TE Link attributes of PeerNode SID . . . . . . . . . . . . . 4
5. Backward Compatibility . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Segment Routing (SR) leverages source routing. A node steers a
packet through a controlled set of instructions, called segments, by
prepending the packet with an SR header with segment identifiers
(SID). A SID can represent any instruction, topological or service-
based. SR segments allows to enforce a flow through any topological
path or service function while maintaining per-flow state only at the
ingress node of the SR domain.
As there is no per-path state in the network, the bandwidth
management for the paths is expected to be handled by a controller
which has a complete view of:
1. Up-to-date topology of the network
2. Resources, States and Attributes of links and nodes of the
network
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3. Run-time utilization/availability of resources
In the case of multi-AS networks, the controller learns the topology
from all the involved ASes by participating in their IGPs or by BGP-
LS [RFC7752] and the inter-AS link information via BGP-LS
EPE[I-D.ietf-idr-bgpls-segment-routing-epe] along with extensions
defined in this document.Then the controller merges above information
sets to consolidated Traffic Engineering Database and computes end-
to-end TE paths.
2. Reference Topology
The controller learns TE attributes of all the links, including the
inter-AS links and uses the attributes to compute constrained paths.
The controller should be able to correlate the inter-AS links for
bidirectional connectivity from both ASes.
+----------+
|Controller|
+----------+
|
|----------|
+---------+ +------+
| | | |
| H B------D G
| | +---/| AS 2 |\ +------+
| |/ +------+ \ | |---L/8
A AS1 C---+ \| |
| |\\ \ +------+ /| AS 4 |---M/8
| | \\ +-E |/ +------+
| X | \\ | K
| | +===F AS 3 |
+---------+ +------+
Figure 1: Reference Diagram
The reference diagram from
[I-D.ietf-spring-segment-routing-central-epe] represents multiple
Autonomous Systems connected to each other. When the Multiple ASes
belong to same operator and are organised into separate domains for
operational purposes, it is advantageous to support Traffic-
Engineering across the ASes including the inter-AS links. The
controller has visibility of all of the ASes by means of IGP topology
exported via BGP-LS [RFC7752], or other means. In addition, the
inter-AS links and the labels associated with the inter-AS links are
exported via [I-D.ietf-idr-bgpls-segment-routing-epe]. The
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controller needs to correlate the information acquired from all of
the ASes, including the inter-AS links in order to get a view of the
unified topology so that it can build end-to-end Traffic-Engineered
paths.
3. Fast Reroute Label
[I-D.ietf-spring-segment-routing-central-epe] section 3.6 describes
mechanisms to provide Fast Reroute (FRR) protection for the EPE
Labels. The controller needs to know which links are used for
protection so that admission control and failure simulation can be
done effectively and appropriate inter-AS links used for path
construction.
This document defines a new flag 'F" in the Peering SIDs TLV to
indicate a SID as an FRR SID. The protection for any peering SID can
be specified using another PeerAdjSID, PeerNodeSID or PeerSetSID to
the controller. If the protection is achieved by fallback to local
IP lookup, FRR SID SHOULD not be advertised . The link(s)
represented by the FRR SID will carry the traffic when there is a
failure. These SIDs are included as an FRR SIDs in the peerAdjSID,
PeerNodeSID and PeerSetSID advertisements.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|V|L|B|P|F|Rsvd |
+-+-+-+-+-+-+-+-+
Figure 2: Peering SID TLV Flags Format
* F-Flag: FRR Label Flag: If set, the peer SID where the FRR Label
appears is using backup links represented by FRR Label.
4. TE Link attributes of PeerNode SID
A Peer Node Segment is a segment describing a peer, including the SID
(PeerNode SID) allocated to it. The link descriptors for the Peer
Node SID include the addresses used by the BGP session encoded using
TLVs as defined in [RFC7752]. In general case, eBGP session could be
of multi-hop type, and use multiple underlaying IP interfaces. The
IP addesess used by BGP session as local/neigbour are not sufficient
to identify this underlaying interfaces. At the same time, the
controller needs to know the links associated with the Peer Node SID,
to be able derive TE link attributes. This can be achieved by
including the interface local and remote addresses in the Link
attributes in Peer Node SID NLRI.
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PeerAdjSID MUST be advertised for each inter-AS link for the purposes
of inter-AS TE. The PeerAdjSID should contain link TE attributes
such as bandwidth, admin-group etc. The PeerAdjSID should also
contain the local and remote interface ipv4/ipv6 addresses which is
used for correlating the links. PeerNodeSID SHOULD contain the
additional attribute of link local address which is used by the
controller to find corresponding PeerAdjSID and hence the
corresponding link TE attributes. PeerAdjSID advertisements MUST
contain local and remote interface addresses for the purpose of
inter-As TE to be help controller correlate the links. Unnumbered
interface is not in the scope of this document.
+-----------+---------------------+--------------+------------------+
| TLV Code | Description | IS-IS TLV | Reference |
| Point | | /Sub-TLV | (RFC/Section) |
+-----------+---------------------+--------------+------------------+
| TBD | IPv4 Local interface| 22/6 | [RFC5305]/3.2 |
| | Address | | |
| TBD | IPv6 Local interface| 22/12 | [RFC6119]/4.2 |
| | Address | | |
+-------------------------------------------------------------------+
Figure 3: Link Addresses carried as attributes
For Example
5. Backward Compatibility
The extension proposed in this document is backward compatible with
procedures described in [I-D.ietf-idr-bgpls-segment-routing-epe] and
[I-D.ietf-spring-segment-routing-central-epe]
6. Security Considerations
TBD
7. IANA Considerations
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+-----------+---------------------+--------------+------------------+
| TLV Code | Description | IS-IS TLV | Reference |
| Point | | /Sub-TLV | (RFC/Section) |
+-----------+---------------------+--------------+------------------+
| TBD | IPv4 Local interface| 22/6 | [RFC5305]/3.2 |
| | Address | | |
| TBD | IPv6 Local interface| 22/12 | [RFC6119]/4.2 |
| | Address | | |
+-------------------------------------------------------------------+
Figure 4: Link Attribute TLVs
8. Acknowledgements
Thanks to Julian Lucek and Rafal Jan Szarecki for careful review and
suggestions.
9. References
9.1. Normative References
[I-D.ietf-idr-bgpls-segment-routing-epe]
Previdi, S., Talaulikar, K., Filsfils, C., Patel, K., Ray,
S., and J. Dong, "BGP-LS extensions for Segment Routing
BGP Egress Peer Engineering", draft-ietf-idr-bgpls-
segment-routing-epe-17 (work in progress), October 2018.
[I-D.ietf-spring-segment-routing-central-epe]
Filsfils, C., Previdi, S., Dawra, G., Aries, E., and D.
Afanasiev, "Segment Routing Centralized BGP Egress Peer
Engineering", draft-ietf-spring-segment-routing-central-
epe-10 (work in progress), December 2017.
[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>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/info/rfc7752>.
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9.2. Informative References
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
Authors' Addresses
Shraddha Hegde
Juniper Networks Inc.
Exora Business Park
Bangalore, KA 560103
India
Email: shraddha@juniper.net
Srihari Sangli
Juniper Networks Inc.
Exora Business Park
Bangalore, KA 560103
India
Email: ssangli@juniper.net
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