c
Network Working Group S. Previdi, Ed.
Internet-Draft C. Filsfils
Intended status: Standards Track S. Ray
Expires: November 27, 2014 K. Patel
Cisco Systems, Inc.
May 26, 2014
Segment Routing Egress Peer Engineering BGPLS Extensions
draft-previdi-idr-bgpls-segment-routing-epe-00
Abstract
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. A segment can represent any
instruction, topological or service-based. SR allows to enforce a
flow through any topological path and service chain while maintaining
per-flow state only at the ingress node of the SR domain.
The Segment Routing architecture can be directly applied to the MPLS
dataplane with no change on the forwarding plane. It requires minor
extension to the existing link-state routing protocols.
This document outline a BGPLS extension for exporting BGP egress
point topology information (including its peers, interfaces and
peering ASs) in a way that is exploitable in order to compute
efficient Egress Point Engineering policies and strategies.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://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
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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 November 27, 2014.
Copyright Notice
Copyright (c) 2014 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
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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 . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Segment Routing Documents . . . . . . . . . . . . . . . . . . 3
3. BGP Peering Segments . . . . . . . . . . . . . . . . . . . . 3
4. Peering Segment NLRI-Type . . . . . . . . . . . . . . . . . . 4
4.1. Peer Descriptors . . . . . . . . . . . . . . . . . . . . 4
4.2. Peer Attributes . . . . . . . . . . . . . . . . . . . . . 5
5. Definition of PeerNode and PeerAdj . . . . . . . . . . . . . 5
5.1. PeerNode Segment (PeerNodeSID) . . . . . . . . . . . . . 5
5.2. PeerAdj Segment (PeerAdjSID) . . . . . . . . . . . . . . 6
5.3. PeerSet Segment (PeerSetSID) . . . . . . . . . . . . . . 7
6. Illustration . . . . . . . . . . . . . . . . . . . . . . . . 7
6.1. Reference Diagram . . . . . . . . . . . . . . . . . . . . 7
6.1.1. PeerNode for Node D . . . . . . . . . . . . . . . . . 9
6.1.2. PeerNode for Node H . . . . . . . . . . . . . . . . . 9
6.1.3. PeerNode for Node E . . . . . . . . . . . . . . . . . 9
6.1.4. PeerAdj for Node E, Link 1 . . . . . . . . . . . . . 10
6.1.5. PeerAdj for Node E, Link 2 . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
8. Manageability Considerations . . . . . . . . . . . . . . . . 11
9. Security Considerations . . . . . . . . . . . . . . . . . . . 11
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
11.1. Normative References . . . . . . . . . . . . . . . . . . 11
11.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
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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. A segment can represent any
instruction, topological or service-based. SR allows to enforce a
flow through any topological path and service chain while maintaining
per-flow state only at the ingress node of the SR domain.
The Segment Routing architecture can be directly applied to the MPLS
dataplane with no change on the forwarding plane. It requires minor
extension to the existing link-state routing protocols.
This document outline a BGPLS extension for exporting BGP egress
point topology information (including its peers, interfaces and
peering ASs) in a way that is exploitable in order to compute
efficient Egress Point Engineering policies and strategies.
2. Segment Routing Documents
The main reference for this document is the SR architecture defined
in [I-D.filsfils-spring-segment-routing].
The Segment Routing Egress Peer Engineering architecture is described
in [I-D.filsfils-spring-segment-routing-central-epe].
3. BGP Peering Segments
As defined in [draft-filsfils-spring-segment-routing-epe], an EPE
enabled Egress PE node MAY advertise segments corresponding to its
attached peers. These segments are called BGP peering segments or
BGP Peering SIDs. They enable the expression of source-routed inter-
domain paths.
An ingress border router of an AS may compose a list of segments to
steer a flow along a selected path within the AS, towards a selected
egress border router C of the AS and through a specific peer. At
minimum, a BGP Peering Engineering policy applied at an ingress PE
involves two segments: the Node SID of the chosen egress PE and then
the BGP Peering Segment for the chosen egress PE peer or peering
interface.
Hereafter, we will define three types of BGP peering segments/SID's:
PeerNodeSID, PeerAdjSID and PeerGroupSID.
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4. Peering Segment NLRI-Type
This section described a new NLRI-Type in the BGP-LS specification
([I-D.ietf-idr-ls-distribution]). The new NLRI-Type (5) is called
the Peer NLRI-Type and describes the connectivity of a BGP Egress
router.
The format of the Peer NLRI Type is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+
| Protocol-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |
| (64 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Local Node Descriptors (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Peer Descriptors (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Link Descriptors (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where:
Local Node Descriptors: as defined in
[I-D.ietf-idr-ls-distribution] Section 3.2.1.2.
Link Descriptors: as defined in [I-D.ietf-idr-ls-distribution]
Section 3.2.2.
4.1. Peer Descriptors
The following Sub-TLVs are allowed to be used as Peer Descriptors:
+------------+------------------------+--------+
| Sub-TLV | Description | Length |
| Code Point | | |
+------------+------------------------+--------+
| 512 | Peer Autonomous System | 4 |
| 513 | BGP-LS Identifier | 4 |
+------------+------------------------+--------+
Peer Descriptors Sub-TLVs are defined in
[I-D.ietf-idr-ls-distribution].
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4.2. Peer Attributes
The Peer Attributes Sub-TLVs codepoints and lengths are listed in the
following table:
+----------+--------------------------+----------+---------------+
| TLV Code | Description | Length | IS-IS SR TLV |
| Point | | | /sub-TLV |
+----------+--------------------------+----------+---------------+
| 1099 | Adjacency Segment | variable | 31 (section |
| | Identifier (Adj-SID) | | 2.3.1) |
| 1100 | LAN Adjacency Segment | variable | 32 (section |
| | Identifier (Adj-LAN SID) | | 2.3.2) |
| TBA | Peer Set SID | variable | 31 (section |
| | | | 2.3.1) |
+----------+--------------------------+----------+---------------+
Sections refer to [I-D.ietf-idr-ls-distribution].
The value of the Adj-SID, Adj-LAN-SID and Peer Set SID Sub-TLV SHOULD
be persistent across router restart.
5. Definition of PeerNode and PeerAdj
In this section the following Peer Segments are defined:
PeerNode Segment (PeerNodeSID)
PeerAdj Segment (PeerAdjSID)
PeerSet Segment (PeerSetSID)
5.1. PeerNode Segment (PeerNodeSID)
A BGP PeerNode segment/SID is a local segment. At the BGP node
advertising it, its semantics is:
o SR header operation: NEXT (as defined in
[I-D.filsfils-spring-segment-routing]).
o Next-Hop: the connected peering node to which the segment is
related.
The PeerNode is advertised with a Peering Segment NLRI, where:
o Local Node Descriptor is the IGP node describing the EPE enabled
egress PE.
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o Peer Descriptor is the ASN of the peer.
o Link Descriptors, as defined in [I-D.ietf-idr-ls-distribution]
contain the addresses used by the BGP session:
* IPv4 Interface Address (Sub-TLV 259) contains the BGP session
IPv4 local address.
* IPv4 Neighbor Address (Sub-TLV 260) contains the BGP session
IPv4 peer address.
* IPv6 Interface Address (Sub-TLV 261) contains the BGP session
IPv6 local address.
* IPv6 Neighbor Address (Sub-TLV 262) contains the BGP session
IPv6 peer address.
o Peer Attribute contains the Adj-SID TLV
5.2. PeerAdj Segment (PeerAdjSID)
A BGP PeerAdj segment/SID is a local segment. At the BGP node
advertising it, its semantics is:
o SR header operation: NEXT (as defined in
[I-D.filsfils-spring-segment-routing]).
o Next-Hop: the peer connected through the interface to which the
segment is related.
The PeerAdj is advertised with a Peering Segment NLRI, where:
o Local Node Descriptor is the IGP node describing the EPE enabled
egress PE.
o Peer Descriptor is the ip address and ASN of the peer.
o Link Descriptors, as defined in
[I-D.ietf-idr-ls-distribution]contain the addresses used by the
BGP session:
* IPv4 Interface Address (Sub-TLV 259) contains the BGP session
IPv4 local address.
* IPv4 Neighbor Address (Sub-TLV 260) contains the BGP session
IPv4 peer address.
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* IPv6 Interface Address (Sub-TLV 261) contains the BGP session
IPv6 local address.
* IPv6 Neighbor Address (Sub-TLV 262) contains the BGP session
IPv6 peer address.
o Peer Attribute contains the Adj-SID TLV
In addition, BGPLS Link Attributes, as defined in
[I-D.ietf-idr-ls-distribution]MAY be inserted in order to advertise
the characteristics of the link.
5.3. PeerSet Segment (PeerSetSID)
A PeerSet segment/SID is a local segment. At the BGP node
advertising it, its semantics is:
o SR header operation: NEXT (as defined in
[I-D.filsfils-spring-segment-routing]).
o Next-Hop: loadbalance across any connected interface to any peer
in the related set.
The PeerSet is advertised in a Peering Segment NLRI (PeerNode or
PeerAdj) as a BGPLS attribute.
The PeerSet Attribute contains an Adj-SID TLV, defined in Section 4.2
identifying the Set the PeerNode or PeerAdj is part of.
6. Illustration
6.1. Reference Diagram
The following reference diagram is used throughout this document.
The solution is described for IPv4 with MPLS-based segments.
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+------+
| |
+---D F
+---------+ / | AS 2 |\ +------+
| X |/ +------+ \ | Z |---L/8
A C---+ \| |
| |\\ \ +------+ /| AS 4 |---M/8
| AS1 | \\ +-H |/ +------+
| | \\ | G
+----P----+ +===E AS 3 |
| +--Q---+
| |
+----------------+
Figure 1: Reference Diagram
IPv4 addressing:
o C's interface to D: 1.0.1.1/24, D's interface: 1.0.1.2/24
o C's interface to H: 1.0.2.1/24, H's interface: 1.0.2.2/24
o C's upper interface to E: 1.0.3.1/24, E's interface: 1.0.3.2/24
o C's lower interface to E: 1.0.4.1/24, E's interface: 1.0.4.2/24
o Loopback of E used for eBGP multi-hop peering to C: 1.0.5.2/32
o C's loopback is 3.3.3.3/32 with SID 64
C's BGP peering:
o Single-hop eBGP peering with neighbor 1.0.1.2 (D)
o Single-hop eBGP peering with neighbor 1.0.2.2 (H)
o Multi-hop eBGP peering with E on ip address 1.0.5.2 (E)
C's resolution of the multi-hop eBGP session to E:
o Static route 1.0.5.2/32 via 1.0.3.2
o Static route 1.0.5.2/32 via 1.0.4.2
Node C configuration is such that:
o A PeerNode segment is allocated to each peer (D, H and E).
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o A PeerAdj segment is defined for each recursing interface to a
multi-hop peer (CE upper and lower interfaces).
o A PeerSet is defined to include all peers in AS3 (peers H and E).
6.1.1. PeerNode for Node D
Descriptors:
o Node Descriptors (router-ID, ASN): 3.3.3.3 , AS1
o Peer Descriptors (peer ASN): AS2
o Link Descriptors (IPv4 interface address, neighbor IPv4 address):
1.0.1.1, 1.0.1.2
Attributes:
o Adj-SID: 1012
6.1.2. PeerNode for Node H
Descriptors:
o Node Descriptors (router-ID, ASN): 3.3.3.3 , AS1
o Peer Descriptors (peer ASN): AS3
o Link Descriptors (IPv4 interface address, neighbor IPv4 address):
1.0.2.1, 1.0.2.2
Attributes:
o Adj-SID: 1022
o PeerSetSID: 1060
o Link Attributes: see section 3.3.2 of
[I-D.ietf-idr-ls-distribution]
6.1.3. PeerNode for Node E
Descriptors:
o Node Descriptors (router-ID, ASN): 3.3.3.3 , AS1
o Peer Descriptors (peer ASN): AS3
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o Link Descriptors (IPv4 interface address, neighbor IPv4 address):
3.3.3.3, 1.0.5.2
Attributes:
o Adj-SID: 1052
o PeerSetSID: 1060
6.1.4. PeerAdj for Node E, Link 1
Descriptors:
o Node Descriptors (router-ID, ASN): 3.3.3.3 , AS1
o Peer Descriptors (peer ASN): AS3
o Link Descriptors (IPv4 interface address, neighbor IPv4 address):
1.0.3.1 , 1.0.3.2
Attributes:
o Adj-SID: 1032
o LinkAttributes: see section 3.3.2 of
[I-D.ietf-idr-ls-distribution]
6.1.5. PeerAdj for Node E, Link 2
Descriptors:
o Node Descriptors (router-ID, ASN): 3.3.3.3 , AS1
o Peer Descriptors (peer ASN): AS3
o Link Descriptors (IPv4 interface address, neighbor IPv4 address):
1.0.4.1 , 1.0.4.2
Attributes:
o Adj-SID: 1042
o LinkAttributes: see section 3.3.2 of
[I-D.ietf-idr-ls-distribution]
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7. IANA Considerations
This document defines a new BGPLS NLRI TYPE known as the Peer NLRI
Type and a new BGP attribute known as the Peer Set SID TLV. The code
points are to be assigned by IANA.
8. Manageability Considerations
TBD
9. Security Considerations
TBD
10. Acknowledgements
TBD
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
11.2. Informative References
[I-D.filsfils-spring-segment-routing]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R.,
Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe,
"Segment Routing Architecture", draft-filsfils-spring-
segment-routing-01 (work in progress), May 2014.
[I-D.filsfils-spring-segment-routing-central-epe]
Filsfils, C., Previdi, S., Patel, K., Aries, E.,
shaw@fb.com, s., Ginsburg, D., and D. Afanasiev, "Segment
Routing Centralized Egress Peer Engineering", draft-
filsfils-spring-segment-routing-central-epe-01 (work in
progress), May 2014.
[I-D.ietf-idr-ls-distribution]
Gredler, H., Medved, J., Previdi, S., Farrel, A., and S.
Ray, "North-Bound Distribution of Link-State and TE
Information using BGP", draft-ietf-idr-ls-distribution-05
(work in progress), May 2014.
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Authors' Addresses
Stefano Previdi (editor)
Cisco Systems, Inc.
Via Del Serafico, 200
Rome 00142
Italy
Email: sprevidi@cisco.com
Clarence Filsfils
Cisco Systems, Inc.
Brussels
BE
Email: cfilsfil@cisco.com
Saikat Ray
Cisco Systems, Inc.
170, West Tasman Drive
San Jose, CA 95134
US
Email: sairay@cisco.com
Keyur Patel
Cisco Systems, Inc.
170, West Tasman Drive
San Jose, CA 95134
US
Email: keyupate@cisco.com
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