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Versions: 00 01 02 03 04 05 draft-ietf-spring-segment-routing-central-epe

Network Working Group                                   C. Filsfils, Ed.
Internet-Draft                                           S. Previdi, Ed.
Intended status: Informational                                  K. Patel
Expires: January 5, 2015                             Cisco Systems, Inc.
                                                                E. Aries
                                                                 S. Shaw
                                                                Facebook
                                                             D. Ginsburg
                                                            D. Afanasiev
                                                                  Yandex
                                                            July 4, 2014


          Segment Routing Centralized Egress Peer Engineering
          draft-filsfils-spring-segment-routing-central-epe-02

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 illustrates the application of Segment Routing to solve
   the Egress Peer Engineering (EPE) requirement.  The SR-based EPE
   solution allows a centralized (SDN) controller to program any egress
   peer policy at ingress border routers or at hosts within the domain.
   This document is on the informational track.

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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   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
   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 January 5, 2015.

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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Segment Routing Documents . . . . . . . . . . . . . . . .   4
     1.2.  Problem Statement . . . . . . . . . . . . . . . . . . . .   4
   2.  BGP Peering Segments  . . . . . . . . . . . . . . . . . . . .   6
   3.  Distribution of External Topology and TE Information using
       BGP-LS  . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  EPE Route advertising the Peer D and its PeerNode SID . .   7
     3.2.  EPE Route advertising the Peer E and its PeerNode SID . .   7
     3.3.  EPE Route advertising the Peer F and its PeerNode SID . .   8
     3.4.  EPE Route advertising a first PeerAdj to Peer F . . . . .   8
     3.5.  EPE Route advertising a second PeerAdj to Peer F  . . . .   9
     3.6.  FRR . . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   4.  EPE Controller  . . . . . . . . . . . . . . . . . . . . . . .  10
     4.1.  Valid Paths From Peers  . . . . . . . . . . . . . . . . .  11
     4.2.  Intra-Domain Topology . . . . . . . . . . . . . . . . . .  11
     4.3.  External Topology . . . . . . . . . . . . . . . . . . . .  11
     4.4.  SLA characteristics of each peer  . . . . . . . . . . . .  12
     4.5.  Traffic Matrix  . . . . . . . . . . . . . . . . . . . . .  12
     4.6.  Business Policies . . . . . . . . . . . . . . . . . . . .  12
     4.7.  EPE Policy  . . . . . . . . . . . . . . . . . . . . . . .  12
   5.  Programming an input policy . . . . . . . . . . . . . . . . .  13



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     5.1.  At a Host . . . . . . . . . . . . . . . . . . . . . . . .  13
     5.2.  At a router - SR Traffic Engineering tunnel . . . . . . .  13
     5.3.  At a Router - BGP3107 policy route  . . . . . . . . . . .  14
     5.4.  At a Router - VPN policy route  . . . . . . . . . . . . .  14
     5.5.  At a Router - Flowspec route  . . . . . . . . . . . . . .  14
   6.  IPv6  . . . . . . . . . . . . . . . . . . . . . . . . . . . .  15
   7.  Benefits  . . . . . . . . . . . . . . . . . . . . . . . . . .  15
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
   9.  Manageability Considerations  . . . . . . . . . . . . . . . .  16
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  16
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  16
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  16
     12.2.  Informative References . . . . . . . . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   The document is structured as follows:

   o  Section 1 reminds the EPE problem statement and provides the key
      references.

   o  Section 2 defines the different BGP Peering Segments and the
      semantic associated to them.

   o  Section 3 describes the automated allocation of BGP Peering SID's
      by the EPE-enabled egress border router and the automated
      signaling of the external peering topology and the related BGP
      Peering SID's to the collector
      [[I-D.previdi-idr-bgpls-segment-routing-epe].

   o  Section 4 overviews the components of a centralized EPE
      controller.  The definition of the EPE controller is outside the
      scope of this document.

   o  Section 5 overviews the methods that could be used by the
      centralized EPE controller to implement an EPE policy at an
      ingress border router or at a source host within the domain.  The
      exhaustive definition of all the means to program an EPE input
      policy is outside the scope of this document.

   For editorial reason, the solution is described for IPv4.  A later
   section describes how the same solution is applicable to IPv6.







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1.1.  Segment Routing Documents

   The main references for this document are:

   o  SR Problem Statement: [I-D.ietf-spring-problem-statement].

   o  SR Architecture: [I-D.filsfils-spring-segment-routing].

   o  Distribution of External Topology and TE Information using BGP:
      [I-D.previdi-idr-bgpls-segment-routing-epe].

   The SR instantiation in the MPLS dataplane is described in
   [I-D.filsfils-spring-segment-routing-mpls].

   The SR IGP protocol extensions are defined in
   [I-D.ietf-isis-segment-routing-extensions],
   [I-D.ietf-ospf-segment-routing-extensions] and
   [I-D.psenak-ospf-segment-routing-ospfv3-extension].

   The Segment Routing PCE protocol extensions are defined in
   [I-D.sivabalan-pce-segment-routing].

1.2.  Problem Statement

   The EPE problem statement is defined in
   [I-D.ietf-spring-problem-statement].

   A centralized controller should be able to instruct an ingress PE or
   a content source within the domain to use a specific egress PE and a
   specific external interface to reach a particular destination.

   We call this solution "EPE" for "Egress Peer Engineering".  The
   centralized controller is called the "EPE Controller".  The egress
   border router where the EPE traffic-steering functionality is
   implemented is called an EPE-enabled border router.  The input policy
   programmed at an ingress border router or at a source host is called
   an EPE policy.

   The requirements that have motivated the solution described in this
   document are listed here below:

   o  The solution MUST apply to the Internet use-case where the
      Internet routes are assumed to use IPv4 unlabeled or IPv6
      unlabeled.  It is not required to place the internet routes in a
      VRF and allocate labels on a per route, or on a per-path basis.






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   o  The solution MUST NOT make any assumption on the currently
      deployed iBGP schemes (RRs, confederations or iBGP full meshes)
      and MUST be able to support all of them.

   o  The solution SHOULD minimize the need for new BGP capabilities at
      the ingress PE's.

   o  The solution MUST accommodate an ingress EPE policy at an ingress
      PE or directly at an source host within the domain.

   o  The solution MUST support automated FRR and fast convergence.

   The following reference diagram is used throughout this document.

   +---------+      +------+
   |         |      |      |
   |    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

   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 E: 1.0.2.1/24, E's interface: 1.0.2.2/24

   o  C's upper interface to F: 1.0.3.1/24, F's interface: 1.0.3.2/24

   o  C's lower interface to F: 1.0.4.1/24, F's interface: 1.0.4.2/24

   o  Loopback of F 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 (E)




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   o  Multi-hop eBGP peering with F on ip address 1.0.5.2 (F)

   C's resolution of the multi-hop eBGP session to F:

   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

   C is configured with local policy that defines a BGP PeerSet as the
   set of peers (1.0.2.2 and 1.0.5.2)

   X is the EPE controller within AS1 domain.

   H is a content source within AS1 domain.

2.  BGP Peering Segments

   AS defined in [I-D.filsfils-spring-segment-routing], Segments are
   defined by a Egress Peer Engineering (EPE) capable node and
   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.

   [I-D.filsfils-spring-segment-routing] defines three types of BGP
   peering segments/SID's: PeerNodeSID, PeerAdjSID and PeerSetSID.

   The BGP extensions to signal these BGP peering segments are outlined
   in the following section.

3.  Distribution of External Topology and TE Information using BGP-LS

   In ships-in-the-night mode with respect to the pre-existing iBGP
   design, a BGPLS session is established between the EPE-enabled border
   router and the EPE controller.

   As a result of its local configuration and according to the behavior
   described in [I-D.previdi-idr-bgpls-segment-routing-epe], node C
   allocates the following BGP Peering Segments
   ([I-D.filsfils-spring-segment-routing]):




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   o  A PeerNode segment for each of its defined peer (D, E and F).

   o  A PeerAdj segment for each recursing interface to a multi-hop peer
      (e.g.: the upper and lower interfaces from C to F in figure 1).

   o  A PeerSet segment to the set of peers (E and F).

   C programs its forwarding table accordingly:

   Incoming             Outgoing
   Label     Operation  Interface
   ------------------------------------
   1012          POP    link to D
   1022          POP    link to E
   1032          POP    upper link to F
   1042          POP    lower link to F
   1052          POP    loadbalance on any link to F
   1060          POP    loadbalance on any link to E or to F

   C signals the related BGP-LS NLRI's to the EPE controller.  Each such
   BGP-LS route is described in the following sub-sections according to
   the encoding details defined in draft-previdi-idr-bgpl-segment-
   routing-epe-00.

3.1.  EPE Route advertising the Peer D and its PeerNode SID

   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

3.2.  EPE Route advertising the Peer E and its PeerNode SID

   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):
      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]

3.3.  EPE Route advertising the Peer F and its PeerNode SID

   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):
      3.3.3.3, 1.0.5.2

   Attributes:

   o  Adj-SID: 1052

   o  PeerSetSID: 1060

3.4.  EPE Route advertising a first PeerAdj to Peer F

   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]





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3.5.  EPE Route advertising a second PeerAdj to Peer F

   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]

3.6.  FRR

   An EPE-enabled border router should allocate a FRR backup entry on a
   per BGP Peering SID basis:

   o  PeerNode SID

      1.  If multi-hop, backup via the remaining PeerADJ SID's to the
          same peer.

      2.  Else backup via local PeerNode SID to the same AS.

      3.  Else pop the PeerNode SID and IP lookup (with potential BGP
          PIC fall-back).

   o  PeerAdj SID

      1.  If to a multi-hop peer, backup via the remaining PeerADJ SID's
          to the same peer.

      2.  Else backup via PeerNode SID to the same AS.

      3.  Else pop the PeerNode SID and IP lookup (with potential BGP
          PIC fall-back).

   o  PeerSet SID

      1.  Backup via remaining PeerNode SID in the same PeerSet.





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      2.  Else pop the PeerSet SID and IP lookup (with potential BGP PIC
          fall-back).

   We illustrate the different types of possible backups using the
   reference diagram and considering the Peering SID's allocated by C.

   PeerNode SID 1052, allocated by C for peer F:

   o  Upon the failure of the upper connected link CF, C can reroute all
      the traffic onto the lower CF link to the same peer (F).

   PeerNode SID 1022, allocated by C for peer E:

   o  Upon the failure of the connected link CE, C can reroute all the
      traffic onto the link to PeerNode SID 1052 (F).

   PeerNode SID 1012, allocated by C for peer D:

   o  Upon the failure of the connected link CD, C can pop the PeerNode
      SID and lookup the IP destination address in its FIB and route
      accordingly.

   PeerSet SID 1060, allocated by C for the set of peers E and F:

   o  Upon the failure of a connected link in the group, the traffic to
      PeerSet SID 1060 is rerouted on any other member of the group.

   For specific business reasons, the operator might not want the
   default FRR behavior applied to a PeerNode SID or any of its
   depending PeerADJ SID.

   The operator should be able to associate a specific backup PeerNode
   SID for a PeerNode SID: e.g. 1022 (E) must be backed up by 1012 (D)
   which over-rules the default behavior which would have preferred F as
   a backup for E.

4.  EPE Controller

   In this section, we provide a non-exhaustive set of inputs that an
   EPE controller would likely collect such as to perform the EPE policy
   decision.

   The exhaustive definition is outside the scope of this document.








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4.1.  Valid Paths From Peers

   The EPE controller should collect all the paths advertised by all the
   engineered peers.

   This could be realized by setting an iBGP session with the EPE-
   enabled border router, with "add-path all" and original next-hop
   preserved.

   In this case, C would advertise the following Internet routes to the
   EPE controller:

   o  NLRI <L/8>, nhop 1.0.1.2, AS Path {AS 2, 4}

      *  X (i.e.: the EPE controller) knows that C receives a path to
         L/8 via neighbor 1.0.1.2 of AS2.

   o  NLRI <L/8>, nhop 1.0.2.2, AS Path {AS 3, 4}

      *  X knows that C receives a path to L/8 via neighbor 1.0.2.2 of
         AS2.

   o  NLRI <L/8>, nhop 1.0.5.2, AS Path {AS 3, 4}

      *  X knows that C has an eBGP path to L/8 via AS3 via neighbor
         1.0.5.2

   An alternative option consists in Adj-RIB-In BMP from EPE-enabled
   border router to the EPE collector.

4.2.  Intra-Domain Topology

   The EPE controller should collect the internal topology and the
   related IGP SID's.

   This could be realized by collecting the IGP LSDB of each area or
   running a BGP-LS session with a node in each IGP area.

4.3.  External Topology

   Thanks to the collected BGP-LS routes described in the section 2
   (BGPLS advertisements), the EPE controller is able to maintain an
   accurate description of the egress topology of node C.  Furthermore,
   the EPE controller is able to associate BGP Peering SID's to the
   various components of the external topology.






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4.4.  SLA characteristics of each peer

   The EPE controller might collect SLA characteristics across peers.
   This requires an EPE solution as the SL A probes need to be steered
   via non-best-path peers.

   Uni-directional SLA monitoring of the desired path is likely
   required.  This might be possible when the application is controlled
   at the source and the receiver side.  Uni-directional monitoring
   dissociates the SLA characteristic of the return path (which cannot
   usually be controlled) from the forward path (the one of interest for
   pushing content from a source to a consumer and the one which can be
   controlled).

   Alternatively, Extended Metrics, as defined in
   [I-D.ietf-isis-te-metric-extensions] could also be advertised using
   new bgpls attributes.

4.5.  Traffic Matrix

   The EPE controller might collect the traffic matrix to its peers or
   the final destinations.  IPFIX is a likely option.

   An alternative option consists in collecting the link utilization
   statistics of each of the internal and external links, also available
   in current definition of [I-D.ietf-idr-ls-distribution].

4.6.  Business Policies

   The EPE controller should collect business policies.

4.7.  EPE Policy

   On the basis of all these inputs (and likely other), the EPE
   Controller decides to steer some demands away from their best BGP
   path.

   The EPE policy is likely expressed as a two-entry segment list where
   the first element is the IGP prefix SID of the selected egress border
   router and the second element is a BGP Peering SID at the selected
   egress border router.

   A few examples are provided hereafter:

   o  Prefer egress PE C and peer AS AS2: {64, 1012}.

   o  Prefer egress PE C and peer AS AS3 via ebgp peer 1.0.2.2: {64,
      1022}.



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   o  Prefer egress PE C and peer AS AS3 via ebgp peer 1.0.5.2: {64,
      1052}.

   o  Prefer egress PE C and peer AS AS3 via interface 1.0.4.2 of multi-
      hop ebgp peer 1.0.5.2: {64, 1042}.

   o  Prefer egress PE C and any interface to any peer in the group
      1060: {64, 1060}.

   Note that the first SID could be replaced by a list of segments.
   This is useful when an explicit path within the domain is required
   for traffic-engineering purpose.  For example, if the Prefix SID of
   node B is 60 and the EPE controller would like to steer the traffic
   from A to C via B then through the external link to peer D then the
   segment list would be {60, 64, 1012}.

5.  Programming an input policy

   The detailed/exhaustive description of all the means to implement an
   EPE policy are outside the scope of this document.  A few examples
   are provided in this section.

5.1.  At a Host

   A static IP/MPLS route can be programmed at the host H.  The static
   route would define a destination prefix, a next-hop and a label stack
   to push.  The global property of the IGP Prefix SID is particularly
   convenient: the same policy could be programmed across hosts
   connected to different routers.

5.2.  At a router - SR Traffic Engineering tunnel

   The EPE controller can configure the ingress border router with an SR
   traffic engineering tunnel T1 and a steering-policy S1 which causes a
   certain class of traffic to be mapped on the tunnel T1.

   The tunnel T1 would be configured to push the require segment list.

   The tunnel and the steering policy could be configured via PCEP
   according to [I-D.sivabalan-pce-segment-routing] and
   [I-D.ietf-pce-pce-initiated-lsp] or via Netconf ([RFC6241]).

   Example: at A

   Tunnel T1: push {64, 1042}
   IP route L/8 set nhop T1





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5.3.  At a Router - BGP3107 policy route

   The EPE Controller could build a BGP3107 ([RFC3107]) route (from
   scratch) and send it to the ingress router:

   o  NLRI: the destination prefix to engineer: e.g.  L/8.

   o  Next-Hop: the selected egress border router: C.

   o  Label: the selected egress peer: 1042.

   o  AS path: reflecting the valid AS path of the selected.

   o  Some BGP policy to ensure it be selected as best by the ingress
      router.

   This BGP3107 policy route "overwrites" an equivalent or less-specific
   "best path".  As the best-path is changed, this EPE input policy
   option influences the path propagated to the upstream peer/customers.

5.4.  At a Router - VPN policy route

   The EPE Controller could build a VPNv4 route (from scratch) and send
   it to the ingress router:

   o  NLRI: the destination prefix to engineer: e.g.  L/8.

   o  Next-Hop: the selected egress border router: C.

   o  Label: the selected egress peer: 1042.

   o  Route-Target: selecting the appropriate VRF at the ingress router.

   o  AS path: reflecting the valid AS path of the selected.

   o  Some BGP policy to ensure it be selected as best by the ingress
      router in the related VRF.

   The related VRF must be pre-configured.  A VRF fall-back into main
   FIB might be beneficial to avoid replicating all the "normal"
   internet paths in each VRF.

5.5.  At a Router - Flowspec route

   EPE Controller builds a FlowSpec route and sends it to the ingress
   router to engineer:

   o  Dissemination of Flow Specification Rules ([RFC5575].



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   o  Destination/Source IP Addresses, IP Protocol, Destination/Source
      port (+1 component).

   o  ICMP Type/Code, TCP Flags, Packet length, DSCP, Fragment.

6.  IPv6

   The described solution is applicable to IPv6, either with MPLS-based
   or IPv6-Native segments.  In both cases, the same three steps of the
   solution are applicable:

   o  BGP-LS-based signaling of the external topology and BGP Peering
      Segments to the EPE controller.

   o  Collection of various inputs by the EPE controller to come up with
      a policy decision.

   o  Programming at an ingress router or source host of the desired EPE
      policy which consists in a list of segments to push on a defined
      traffic class.

7.  Benefits

   The EPE solutions described in this document has the following
   benefits:

   o  No assumption on the iBGP design with AS1.

   o  Next-Hop-Self on the internet routes propagated to the ingress
      border routers is possible.  This is a common design rule to
      minimize the number of IGP routes and to avoid importing external
      churn into the internal domain.

   o  Consistent support for traffic-engineering within the domain and
      at the external edge of the domain.

   o  Support host and ingress border router EPE policy programming.

   o  EPE functionality is only required on the EPE-enabled egress
      border router and the EPE controller: an ingress policy can be
      programmed at the ingress border router without any new
      functionality.

   o  Ability to deploy the same input policy across hosts connected to
      different routers (global property of the IGP prefix SID).






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8.  IANA Considerations

   TBD

9.  Manageability Considerations

   TBD

10.  Security Considerations

   TBD

11.  Acknowledgements

   TBD

12.  References

12.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3107]  Rekhter, Y. and E. Rosen, "Carrying Label Information in
              BGP-4", RFC 3107, May 2001.

   [RFC5575]  Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J.,
              and D. McPherson, "Dissemination of Flow Specification
              Rules", RFC 5575, August 2009.

   [RFC6241]  Enns, R., Bjorklund, M., Schoenwaelder, J., and A.
              Bierman, "Network Configuration Protocol (NETCONF)", RFC
              6241, June 2011.

12.2.  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-03 (work in progress), June 2014.









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   [I-D.filsfils-spring-segment-routing-mpls]
              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 with MPLS data plane", draft-filsfils-
              spring-segment-routing-mpls-02 (work in progress), June
              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.

   [I-D.ietf-isis-segment-routing-extensions]
              Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,
              Litkowski, S., Decraene, B., and J. Tantsura, "IS-IS
              Extensions for Segment Routing", draft-ietf-isis-segment-
              routing-extensions-02 (work in progress), June 2014.

   [I-D.ietf-isis-te-metric-extensions]
              Previdi, S., Giacalone, S., Ward, D., Drake, J., Atlas,
              A., Filsfils, C., and W. Wu, "IS-IS Traffic Engineering
              (TE) Metric Extensions", draft-ietf-isis-te-metric-
              extensions-03 (work in progress), April 2014.

   [I-D.ietf-ospf-segment-routing-extensions]
              Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
              Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
              Extensions for Segment Routing", draft-ietf-ospf-segment-
              routing-extensions-00 (work in progress), June 2014.

   [I-D.ietf-pce-pce-initiated-lsp]
              Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP
              Extensions for PCE-initiated LSP Setup in a Stateful PCE
              Model", draft-ietf-pce-pce-initiated-lsp-01 (work in
              progress), June 2014.

   [I-D.ietf-spring-problem-statement]
              Previdi, S., Filsfils, C., Decraene, B., Litkowski, S.,
              Horneffer, M., Geib, R., Shakir, R., and R. Raszuk,
              "SPRING Problem Statement and Requirements", draft-ietf-
              spring-problem-statement-01 (work in progress), June 2014.








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   [I-D.previdi-idr-bgpls-segment-routing-epe]
              Previdi, S., Filsfils, C., Ray, S., and K. Patel, "Segment
              Routing Egress Peer Engineering BGPLS Extensions", draft-
              previdi-idr-bgpls-segment-routing-epe-00 (work in
              progress), May 2014.

   [I-D.psenak-ospf-segment-routing-ospfv3-extension]
              Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
              Shakir, R., Henderickx, W., and J. Tantsura, "OSPFv3
              Extensions for Segment Routing", draft-psenak-ospf-
              segment-routing-ospfv3-extension-02 (work in progress),
              July 2014.

   [I-D.sivabalan-pce-segment-routing]
              Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E., and
              R. Raszuk, "PCEP Extensions for Segment Routing", draft-
              sivabalan-pce-segment-routing-02 (work in progress),
              October 2013.

Authors' Addresses

   Clarence Filsfils (editor)
   Cisco Systems, Inc.
   Brussels
   BE

   Email: cfilsfil@cisco.com


   Stefano Previdi (editor)
   Cisco Systems, Inc.
   Via Del Serafico, 200
   Rome  00142
   Italy

   Email: sprevidi@cisco.com


   Keyur Patel
   Cisco Systems, Inc.
   US

   Email: keyupate@cisco.com








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   Ebben Aries
   Facebook
   US

   Email: exa@fb.com


   Steve Shaw
   Facebook
   US

   Email: shaw@fb.com


   Daniel Ginsburg
   Yandex
   RU

   Email: dbg@yandex-team.ru


   Dmitry Afanasiev
   Yandex
   RU

   Email: fl0w@yandex-team.ru

























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