Network Working Group C. Filsfils, Ed. Internet-Draft S. Previdi, Ed. Intended status: Informational K. Patel Expires: January 7, 2016 Cisco Systems, Inc. E. Aries S. Shaw Facebook D. Ginsburg D. Afanasiev Yandex July 6, 2015 Segment Routing Centralized Egress Peer Engineering draft-filsfils-spring-segment-routing-central-epe-04 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 Filsfils, et al. Expires January 7, 2016 [Page 1] Internet-Draft Segment Routing Centralized EPE July 2015 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 7, 2016. Copyright Notice Copyright (c) 2015 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 Filsfils, et al. Expires January 7, 2016 [Page 2] Internet-Draft Segment Routing Centralized EPE July 2015 5.1. At a Host . . . . . . . . . . . . . . . . . . . . . . . . 13 5.2. At a router - SR Traffic Engineering tunnel . . . . . . . 13 5.3. At a Router - RFC3107 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 states 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. Filsfils, et al. Expires January 7, 2016 [Page 3] Internet-Draft Segment Routing Centralized EPE July 2015 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.ietf-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.ietf-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.ietf-ospf-ospfv3-segment-routing-extensions]. The Segment Routing PCE protocol extensions are defined in [I-D.ietf-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. Filsfils, et al. Expires January 7, 2016 [Page 4] Internet-Draft Segment Routing Centralized EPE July 2015 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 PEs. 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) Filsfils, et al. Expires January 7, 2016 [Page 5] Internet-Draft Segment Routing Centralized EPE July 2015 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.ietf-spring-segment-routing], certain segments are defined by an 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.ietf-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 BGP-LS 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.ietf-spring-segment-routing]): Filsfils, et al. Expires January 7, 2016 [Page 6] Internet-Draft Segment Routing Centralized EPE July 2015 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 load balance on any link to F 1060 POP load balance 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 subsections according to the encoding details defined in [I-D.previdi-idr-bgpls-segment-routing-epe]. 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 PeerNode-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 Filsfils, et al. Expires January 7, 2016 [Page 7] Internet-Draft Segment Routing Centralized EPE July 2015 o Link Descriptors (IPv4 interface address, neighbor IPv4 address): 1.0.2.1, 1.0.2.2 Attributes: o PeerNode-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 PeerNode-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 PeerAdj-SID: 1032 o LinkAttributes: see section 3.3.2 of [I-D.ietf-idr-ls-distribution] Filsfils, et al. Expires January 7, 2016 [Page 8] Internet-Draft Segment Routing Centralized EPE July 2015 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 PeerAdj-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 SIDs to the same peer. 2. Else backup via local PeerNode SID to the same AS. 3. Else pop the PeerNode SID and perform an IP lookup (with potential BGP PIC fall-back). o PeerAdj SID 1. If to a multi-hop peer, backup via the remaining PeerADJ SIDs to the same peer. 2. Else backup via PeerNode SID to the same AS. 3. Else pop the PeerNode SID and perform an IP lookup (with potential BGP PIC fall-back). o PeerSet SID 1. Backup via remaining PeerNode SIDs in the same PeerSet. Filsfils, et al. Expires January 7, 2016 [Page 9] Internet-Draft Segment Routing Centralized EPE July 2015 2. Else pop the PeerNode 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 SIDs 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 dependent 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 overrules 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. Filsfils, et al. Expires January 7, 2016 [Page 10] Internet-Draft Segment Routing Centralized EPE July 2015 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 the original next-hop preserved. In this case, C would advertise the following Internet routes to the EPE controller: o NLRI , 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 , 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 , 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 would be for an EPE collector to use BGP Monitoring Protocol (BMP) to track the Adj-RIB-In of EPE-enabled border routers. 4.2. Intra-Domain Topology The EPE controller should collect the internal topology and the related IGP SIDs. 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 (BGP-LS 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 SIDs to the various components of the external topology. Filsfils, et al. Expires January 7, 2016 [Page 11] Internet-Draft Segment Routing Centralized EPE July 2015 4.4. SLA characteristics of each peer The EPE controller might collect SLA characteristics across peers. This requires an EPE solution as the SLA probes need to be steered via non-best-path peers. Unidirectional 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. Unidirectional 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 BGP-LS 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 the 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 others), 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}. Filsfils, et al. Expires January 7, 2016 [Page 12] Internet-Draft Segment Routing Centralized EPE July 2015 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 purposes. 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 required segment list. The tunnel and the steering policy could be configured via PCEP according to [I-D.ietf-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 Filsfils, et al. Expires January 7, 2016 [Page 13] Internet-Draft Segment Routing Centralized EPE July 2015 5.3. At a Router - RFC3107 policy route The EPE Controller could build a RFC3107 ([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 selected valid AS path. o Some BGP policy to ensure it will be selected as best by the ingress router. This RFC3107 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 selected valid AS path. o Some BGP policy to ensure it will be selected as best by the ingress router in the related VRF. The related VRF must be preconfigured. A VRF fallback to the main FIB might be beneficial to avoid replicating all the "normal" Internet paths in each VRF. 5.5. At a Router - Flowspec route An EPE Controller builds a FlowSpec route and sends it to the ingress router to engineer: o Dissemination of Flow Specification Rules ([RFC5575]. Filsfils, et al. Expires January 7, 2016 [Page 14] Internet-Draft Segment Routing Centralized EPE July 2015 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 have 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 routing domain. o Consistent support for traffic-engineering within the domain and at the external edge of the domain. o Support both 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 (avail the global property of IGP prefix SIDs). Filsfils, et al. Expires January 7, 2016 [Page 15] Internet-Draft Segment Routing Centralized EPE July 2015 8. IANA Considerations This document does not request any IANA allocations. 9. Manageability Considerations TBD 10. Security Considerations TBD 11. Acknowledgements The authors would like to thank Acee Lindem for his comments and contributiuon. 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.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-11 (work in progress), June 2015. [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-05 (work in progress), June 2015. Filsfils, et al. Expires January 7, 2016 [Page 16] Internet-Draft Segment Routing Centralized EPE July 2015 [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-07 (work in progress), June 2015. [I-D.ietf-ospf-ospfv3-segment-routing-extensions] Psenak, P., Previdi, S., Filsfils, C., Gredler, H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPFv3 Extensions for Segment Routing", draft-ietf-ospf-ospfv3- segment-routing-extensions-03 (work in progress), June 2015. [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-05 (work in progress), June 2015. [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-04 (work in progress), April 2015. [I-D.ietf-pce-segment-routing] Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E., Lopez, V., Tantsura, J., Henderickx, W., and J. Hardwick, "PCEP Extensions for Segment Routing", draft-ietf-pce- segment-routing-05 (work in progress), May 2015. [I-D.ietf-spring-problem-statement] Previdi, S., Filsfils, C., Decraene, B., Litkowski, S., Horneffer, M., and R. Shakir, "SPRING Problem Statement and Requirements", draft-ietf-spring-problem-statement-04 (work in progress), April 2015. [I-D.ietf-spring-segment-routing] Filsfils, C., Previdi, S., Decraene, B., Litkowski, S., and R. Shakir, "Segment Routing Architecture", draft-ietf- spring-segment-routing-03 (work in progress), May 2015. [I-D.ietf-spring-segment-routing-mpls] Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., Litkowski, S., Horneffer, M., Shakir, R., Tantsura, J., and E. Crabbe, "Segment Routing with MPLS data plane", draft-ietf-spring-segment-routing-mpls-01 (work in progress), May 2015. Filsfils, et al. Expires January 7, 2016 [Page 17] Internet-Draft Segment Routing Centralized EPE July 2015 [I-D.previdi-idr-bgpls-segment-routing-epe] Previdi, S., Filsfils, C., Ray, S., Patel, K., Dong, J., and M. Chen, "Segment Routing Egress Peer Engineering BGP- LS Extensions", draft-previdi-idr-bgpls-segment-routing- epe-03 (work in progress), April 2015. 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 Ebben Aries Facebook US Email: exa@fb.com Steve Shaw Facebook US Email: shaw@fb.com Filsfils, et al. Expires January 7, 2016 [Page 18] Internet-Draft Segment Routing Centralized EPE July 2015 Daniel Ginsburg Yandex RU Email: dbg@yandex-team.ru Dmitry Afanasiev Yandex RU Email: fl0w@yandex-team.ru Filsfils, et al. Expires January 7, 2016 [Page 19]