--- 1/draft-ietf-rtgwg-multihomed-prefix-lfa-02.txt 2017-10-30 11:13:53.448740929 -0700 +++ 2/draft-ietf-rtgwg-multihomed-prefix-lfa-03.txt 2017-10-30 11:13:53.484741786 -0700 @@ -1,28 +1,28 @@ Routing Area Working Group P. Sarkar, Ed. -Internet-Draft Individual +Internet-Draft Arrcus, Inc. Updates: 5286 (if approved) S. Hegde Intended status: Standards Track C. Bowers -Expires: January 26, 2018 Juniper Networks, Inc. +Expires: May 3, 2018 Juniper Networks, Inc. U. Chunduri, Ed. Huawei Technologies J. Tantsura Individual B. Decraene Orange H. Gredler RtBrick, Inc. - July 25, 2017 + October 30, 2017 LFA selection for Multi-Homed Prefixes - draft-ietf-rtgwg-multihomed-prefix-lfa-02 + draft-ietf-rtgwg-multihomed-prefix-lfa-03 Abstract This document shares experience gained from implementing algorithms to determine Loop-Free Alternates for multi-homed prefixes. In particular, this document provides explicit inequalities that can be used to evaluate neighbors as a potential alternates for multi-homed prefixes. It also provides detailed criteria for evaluating potential alternates for external prefixes advertised by OSPF ASBRs. This documents updates and expands some of the "Routing Aspects" as @@ -35,74 +35,74 @@ document are to be interpreted as described in RFC2119 [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/. + 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 January 26, 2018. + This Internet-Draft will expire on May 3, 2018. Copyright Notice Copyright (c) 2017 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 + (https://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. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 3 2. LFA inequalities for MHPs . . . . . . . . . . . . . . . . . . 4 3. LFA selection for the multi-homed prefixes . . . . . . . . . 4 3.1. Improved coverage with simplified approach to MHPs . . . 6 - 3.2. IS-IS ATT Bit considerations . . . . . . . . . . . . . . 7 + 3.2. IS-IS ATT Bit considerations . . . . . . . . . . . . . . 8 4. LFA selection for the multi-homed external prefixes . . . . . 8 4.1. IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.2. OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 4.2.1. Rules to select alternate ASBR . . . . . . . . . . . 8 - 4.2.2. Multiple ASBRs belonging different area . . . . . . . 9 - 4.2.3. Type 1 and Type 2 costs . . . . . . . . . . . . . . . 10 - 4.2.4. RFC1583compatibility is set to enabled . . . . . . . 10 - 4.2.5. Type 7 routes . . . . . . . . . . . . . . . . . . . . 10 + 4.2.1. Rules to select alternate ASBR . . . . . . . . . . . 9 + 4.2.2. Multiple ASBRs belonging different area . . . . . . . 10 + 4.2.3. Type 1 and Type 2 costs . . . . . . . . . . . . . . . 11 + 4.2.4. RFC1583compatibility is set to enabled . . . . . . . 11 + 4.2.5. Type 7 routes . . . . . . . . . . . . . . . . . . . . 11 4.2.6. Inequalities to be applied for alternate ASBR - selection . . . . . . . . . . . . . . . . . . . . . . 10 - 4.2.6.1. Forwarding address set to non-zero value . . . . 10 - 4.2.6.2. ASBRs advertising type1 and type2 cost . . . . . 11 - 5. LFA Extended Procedures . . . . . . . . . . . . . . . . . . . 12 - 5.1. Links with IGP MAX_METRIC . . . . . . . . . . . . . . . . 12 - 5.2. Multi Topology Considerations . . . . . . . . . . . . . . 13 - 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 - 7. Security Considerations . . . . . . . . . . . . . . . . . . . 14 - 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 - 8.1. Normative References . . . . . . . . . . . . . . . . . . 14 - 8.2. Informative References . . . . . . . . . . . . . . . . . 14 + selection . . . . . . . . . . . . . . . . . . . . . . 11 + 4.2.6.1. Forwarding address set to non-zero value . . . . 11 + 4.2.6.2. ASBRs advertising type1 and type2 cost . . . . . 12 + 5. LFA Extended Procedures . . . . . . . . . . . . . . . . . . . 13 + 5.1. Links with IGP MAX_METRIC . . . . . . . . . . . . . . . . 13 + 5.2. Multi Topology Considerations . . . . . . . . . . . . . . 14 + 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15 + 7. Security Considerations . . . . . . . . . . . . . . . . . . . 15 + 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 + 8.1. Normative References . . . . . . . . . . . . . . . . . . 15 + 8.2. Informative References . . . . . . . . . . . . . . . . . 16 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 1. Introduction The use of Loop-Free Alternates (LFA) for IP Fast Reroute is specified in [RFC5286]. Section 6.1 of [RFC5286] describes a method to determine loop-free alternates for a multi-homed prefixes (MHPs). This document describes a procedure using explicit inequalities that can be used by a computing router to evaluate a neighbor as a potential alternate for a multi-homed prefix. The results obtained are equivalent to those obtained using the method described in @@ -128,26 +128,27 @@ AF - Address Family ATT - IS-IS Attach Bit ECMP - Equal Cost Multi Path IGP - Interior Gateway Protocol IS-IS - Intermediate System to Intermediate System + LSP - IS-IS Link State PDU + OSPF - Open Shortest Path First MHP - Multi-homed Prefix MT - Multi Topology - SPF - Shortest Path First PDU 2. LFA inequalities for MHPs This document proposes the following set of LFA inequalities for selecting the most appropriate LFAs for multi-homed prefixes (MHPs). They can be derived from the inequalities in [RFC5286] combined with the observation that D_opt(N,P) = Min (D_opt(N,PO_i) + cost(PO_i,P)) over all PO_i @@ -156,40 +157,42 @@ D_opt(S,PO_best) + cost(PO_best,P) Link-Protection + Downstream-paths-only: D_opt(N,PO_i)+ cost(PO_i,P) < D_opt(S,PO_best) + cost(PO_best,P) Node-Protection: D_opt(N,PO_i)+ cost(PO_i,P) < D_opt(N,E) + D_opt(E,PO_best) + cost(PO_best,P) Where, + P - The multi-homed prefix being evaluated for + computing alternates S - The computing router N - The alternate router being evaluated E - The primary next-hop on shortest path from S to prefix P. PO_i - The specific prefix-originating router being evaluated. PO_best - The prefix-originating router on the shortest path from the computing router S to prefix P. Cost (X,P) - Cost of reaching the prefix P from prefix originating node X. D_opt(X,Y) - Distance on the shortest path from node X to node Y. Figure 1: LFA inequalities for MHPs 3. LFA selection for the multi-homed prefixes - To compute a valid LFA for a given multi-homed prefix P, through an - alternate neighbor N a computing router S MUST follow one of the - appropriate procedures below. + To compute a valid LFA for a given multi-homed prefix P, a computing + router S MUST follow one of the appropriate procedures below, for + each alternate neighbor N. Link-Protection : ================= 1. If alternate neighbor N is also prefix-originator of P, 1.a. Select N as a LFA for prefix P (irrespective of the metric advertised by N for the prefix P). 2. Else, evaluate the link-protecting LFA inequality for P with the N as the alternate neighbor. 2.a. If LFA inequality condition is met, select N as a LFA for prefix P. @@ -210,21 +213,23 @@ the metric advertised by N for the prefix P). 2. Else, evaluate the appropriate node-protecting LFA inequality for P with the N as the alternate neighbor. 2.a. If LFA inequality condition is met, select N as a LFA for prefix P. 2.b. Else, N is not a LFA for prefix P. Figure 2: Rules for selecting LFA for MHPs In case an alternate neighbor N is also one of the prefix-originators - of prefix P, N MAY be selected as a valid LFA for P. + of prefix P, N MAY be selected as a valid LFA for P since being a + prefix-originator it is guaranteed that N will not loop back packets + destined for prefix P to computing router S. However, if N is not a prefix-originator of P, the computing router SHOULD evaluate one of the corresponding LFA inequalities, as mentioned in Figure 1, once for each remote node that originated the prefix. In case the inequality is satisfied by the neighbor N router S MUST choose neighbor N, as one of the valid LFAs for the prefix P. When computing a downstream-only LFA, in addition to being a prefix- originator of P, router N MUST also satisfy the downstream-only LFA inequality specified in Figure 1. @@ -245,28 +250,28 @@ lower coverage. If an implementation chooses to simplify the multi- homed prefix calculation by assuming that the MHP is solely attached to the router that was its pre-failure optimal point of attachment, the procedure described in this memo can potentially improve coverage for equal cost multi path (ECMP) MHPs without incurring extra computational cost. The approach specified in [RFC5286] Section 6.1 last paragraph, is to simplify the MHP as solely attached to the router that was its pre- failure optimal point of attachment; though it is a scalable approach - and simplifies computation, [RFC5286] notes this may result in little + and simplifies computation, [RFC5286] notes this MAY result in little less coverage. This document improves the above approach to provide loop-free - alternatives without any additional cost for equal cost multi path - MHPs as described through the below example network. The approach - specified here MAY also be applicable for handling default routes as - explained in Section 3.2. + alternatives without any additional cost for ECMP MHPs as described + through the below example network. The approach specified here MAY + also be applicable for handling default routes as explained in + Section 3.2. 5 +---+ 8 +---+ 5 +---+ +-----| S |------| A |-----| B | | +---+ +---+ +---+ | | | | 5 | 5 | | | | +---+ 5 +---+ 4 +---+ 1 +---+ | C |---| E |-----| M |-------| F | +---+ +---+ +---+ +---+ @@ -283,62 +288,68 @@ attachment and share the same primary next-hop. Hence, an implementation MAY compare the kind of protection A provides to F (link-and-node protection) with the kind of protection C provides to E (link protection) and inherit the better alternative to prefix p and here it is A. However, in the below network prefix p has an ECMP through both node E and node F with cost 20. Though it has 2 pre-failure optimal points of attachment, the primary next-hop to each pre-failure optimal point of attachment is different. In this case, prefix p - shall inherit corresponding LFA to each primary next-hop calculated - for the router advertising the same respectively (node E's and node - F's LFA). + MUST inherit corresponding LFAs of each primary next-hop calculated + for the router advertising the same respectively. In the below + diagram that would be node E's and node F's LFA i.e., node N1 and + node N2 respectively. - +---+ 3 +---+ - | S |----------------| B | - +---+ +---+ - | | - 10 | 1 | - | | - +---+ 6 +---+ - | E |-----------------| F | - +---+ +---+ + 4 +----+ + +------------------| N2 | + | +----+ + | | 4 + 10 +---+ 3 +---+ + +------| S |----------------| B | + | +---+ +---+ + | | | + | 10 | 1 | + | | | + +----+ 5 +---+ 16 +---+ + | N1 |----| E |-----------------| F | + +----+ +---+ +---+ | 10 16 | +-----------p---------+ Figure 4: MHP with different ECMP Next-hops In summary, if there are multiple pre-failure points of attachment for a MHP and primary next-hop of a MHP is same as that of the primary next-hop of the router that was pre-failure optimal point of attachment, an implementation MAY provide the better protection to MHP without incurring any additional computation cost. 3.2. IS-IS ATT Bit considerations Per [RFC1195] a default route needs to be added in Level1 (L1) router to the closest reachable Level1/Level2 (L1/L2) router in the network advertising ATT (attach) bit in its LSP-0 fragment. All L1 routers in the area would do this during the decision process with the next- hop of the default route set to the adjacent router through which the closest L1/L2 router is reachable. The base LFA specification [RFC5286] does not specify any procedure for computing LFA for a - default route in IS-IS L1 area. Potentially one MAY consider a - default route is being advertised from the border L1/L2 router where - ATT bit is set and can do LFA computation for the default route. - - But, when multiple ECMP L1/L2 routers are reachable in an L1 area - corresponding best LFAs SHOULD be given for each primary next-hop - associated with default route. Considerations as specified in - Section 3 and Section 3.1 are applicable for default routes, if the - default route is considered as ECMP MHP. + default route in IS-IS L1 area. This document specifies, potentially + a node MAY consider a default route is being advertised from the + border L1/L2 router where ATT bit is set and can do LFA computation + for the default route. But, when multiple ECMP L1/L2 routers are + reachable in an L1 area corresponding best LFAs SHOULD be given for + each primary next-hop associated with default route. Considerations + as specified in Section 3 and Section 3.1 are applicable for default + routes, if the default route is considered as ECMP MHP. Note that, + this document doesn't alter any ECMP handling rules or computation of + LFAs for ECMP in general as laid out in [RFC5286]. 4. LFA selection for the multi-homed external prefixes Redistribution of external routes into IGP is required in case of two different networks getting merged into one or during protocol migrations. External routes could be distributed into an IGP domain via multiple nodes to avoid a single point of failure. During LFA calculation, alternate LFA next-hops to reach the best ASBR could be used as LFA for the routes redistributed via that ASBR. @@ -355,78 +366,81 @@ 2 would also apply to multi-homed external prefixes as well. 4.2. OSPF Loop free Alternates [RFC 5286] describes mechanisms to apply inequalities to find the loop free alternate neighbor. For the selection of alternate ASBR for LFA consideration, additional rules have to be applied in selecting the alternate ASBR due to the external route calculation rules imposed by [RFC 2328]. - This document also defines the inequalities defined in RFC [5286] + This document also defines the inequalities defined in [RFC5286] specifically for the alternate loop-free ASBR evaluation. 4.2.1. Rules to select alternate ASBR The process to select an alternate ASBR is best explained using the rules below. The below process is applied when primary ASBR for the concerned prefix is chosen and there is an alternate ASBR originating same prefix. 1. If RFC1583Compatibility is disabled 1a. if primary ASBR and alternate ASBR are intra area non-backbone path go to step 2. 1b. If primary ASBR and alternate ASBR belong to intra-area backbone and/or inter-area path go to step 2. - 1c. for other paths, skip the alternate ASBR and + 1c. for other paths, skip this alternate ASBR and consider next ASBR. 2. If cost type (type1/type2) advertised by alternate ASBR same as primary - 2a. If not same skip alternate ASBR and consider next ASBR. + 2a. If not, same skip alternate ASBR and consider + next ASBR. + 2b. If same proceed to step 3. 3. If cost type is type1 - 3a. If cost is same, program ECMP + 3a. If cost is same, program ECMP and return. 3b. else go to step 5. 4 If cost type is type 2 4a. If cost is different, skip alternate ASBR and - consider next ASBR - 4b. If type2 cost is same, compare type 1 cost. - 4c. If type1 cost is also same program ECMP. + consider next ASBR. + 4b. If type2 cost is same, proceed to step 4c to compare + compare type 1 cost. + 4c. If type1 cost is also same program ECMP and return. 4d. If type 1 cost is different go to step 5. 5. If route type (type 5/type 7) 5a. If route type is same, check route p-bit, forwarding address field for routes from both - ASBRs - match. If not skip alternate ASBR and consider + ASBRs match. If p-bit matches proceed to step 6. + If not, skip this alternate ASBR and consider next ASBR. - 5b. If route type is not same, skip ASBR - and consider next ASBR. + 5b. If route type is not same, skip this alternate ASBR + and consider next alternate ASBR. 6. Apply inequality on the alternate ASBR. Figure 5: Rules for selecting alternate ASBR in OSPF 4.2.2. Multiple ASBRs belonging different area - When "RFC1583compatibility" is set to disabled, OSPF[RFC2328] defines - certain rules of preference to choose the ASBRs. While selecting - alternate ASBR for loop evaluation for LFA, these rules should be - applied and ensured that the alternate neighbor does not loop the - traffic back. + When "RFC1583compatibility" is set to disabled, OSPF [RFC2328] + defines certain rules of preference to choose the ASBRs. While + selecting alternate ASBR for loop evaluation for LFA, these rules + should be applied and ensured that the alternate neighbor does not + loop the traffic back. When there are multiple ASBRs belonging to different area advertising - the same prefix, pruning rules as defined in RFC 2328 section 16.4.1 + the same prefix, pruning rules as defined in [RFC2328] section 16.4.1 are applied. The alternate ASBRs pruned using above rules are not considered for LFA evaluation. 4.2.3. Type 1 and Type 2 costs If there are multiple ASBRs not pruned via rules defined in 3.2.2, the cost type advertised by the ASBRs is compared. ASBRs advertising Type1 costs are preferred and the type2 costs are pruned. If two ASBRs advertise same type2 cost, the alternate ASBRs are considered along with their type1 cost for evaluation. If the two ASBRs with @@ -539,133 +553,136 @@ +---+ 10 | +---+ |D2 | +---+ Figure 8: Link with IGP MAX_METRIC In the simple example network, all the link costs have a cost of 10 in both directions, except for the link between S and N2. The S-N2 - link has a cost of 10 in the direction from S to N2, and a cost of - MAX_METRIC in the direction from N2 to S (0xffffff /2^24 - 1 for IS- - IS and 0xffff for OSPF) for a specific end to end Traffic Engineering - (TE) requirement of the operator. At node S, D1 is reachable through - N1 with cost 20, and D2 is reachable through N2 with cost 20. Even - though neighbor N2 satisfies basic loop-free condition (inequality 1 - of [RFC5286]) for D1 this could be excluded as potential alternative - because of the current exclusions as specified in section 3.5 and 3.6 - procedure of [RFC5286]. But, as the primary traffic destined to D2 - continue to use the link and hence irrespective of the reverse metric - in this case, the same link MAY be used as a potential LFA for D1. + link has a cost of 10 in the forward direction i.e., from S to N2, + and a cost of MAX_METRIC (0xffffff /2^24 - 1 for IS-IS and 0xffff for + OSPF) in the reverse direction i.e., from N2 to S for a specific end- + to-end Traffic Engineering (TE) requirement of the operator. At node + S, D1 is reachable through N1 with cost 20, and D2 is reachable + through N2 with cost 20. Even though neighbor N2 satisfies basic + loop-free condition (inequality 1 of [RFC5286]) for D1, S's neighbor + N2 could be excluded as a potential alternative because of the + current exclusions as specified in section 3.5 and 3.6 procedure of + [RFC5286]. But, as the primary traffic destined to D2 continue to + use the link and hence irrespective of the reverse metric in this + case, same link MAY be used as a potential LFA for D1. Alternatively, reverse metric of the link MAY be configured with MAX_METRIC-1, so that the link can be used as an alternative while - meeting the TE requirements. + meeting the operator's TE requirements and without having to update + the router to fix this particular issue. 5.2. Multi Topology Considerations Section 6.2 and 6.3.2 of [RFC5286] state that multi-topology OSPF and ISIS are out of scope for that specification. This memo clarifies and describes the applicability. In Multi Topology (MT) IGP deployments, for each MT ID, a separate shortest path tree (SPT) is built with topology specific adjacencies, the LFA principles laid out in [RFC5286] are actually applicable for MT IS-IS [RFC5120] LFA SPF. The primary difference in this case is, identifying the eligible-set of neighbors for each LFA computation which is done per MT ID. The eligible-set for each MT ID is determined by the presence of IGP adjacency from Source to the neighboring node on that MT-ID apart from the administrative restrictions and other checks laid out in [RFC5286]. The same is - also applicable for OSPF [RFC4915] [MT-OSPF] or different AFs in - multi instance OSPFv3 [RFC5838]. + also applicable for MT-OSPF [RFC4915] or different AFs in multi + instance OSPFv3 [RFC5838]. - However for MT IS-IS, if a default topology is used with MT-ID 0 + However for MT IS-IS, if a "standart topology" is used with MT-ID #0 [RFC5286] and both IPv4 [RFC5305] and IPv6 routes/AFs [RFC5308] are present, then the condition of network congruency is applicable for LFA computation as well. Network congruency here refers to, having same address families provisioned on all the links and all the nodes - of the network with MT-ID 0. Here with single decision process both + of the network with MT-ID #0. Here with single decision process both IPv4 and IPv6 next-hops are computed for all the prefixes in the network and similarly with one LFA computation from all eligible neighbors per [RFC5286], all potential alternatives can be computed. 6. Acknowledgements Thanks to Alia Atlas and Salih K A for their useful feedback and - inputs. + inputs. Thanks to Stewart Bryant for being document shepherd and + providing detailed review comments. 7. Security Considerations This document does not introduce any change in any of the protocol - specifications and also this does not introduce any new security - issues other than as noted in the LFA base specification [RFC5286]. + [RFC1195] [RFC5120] [RFC2328] [RFC5838] specifications discussed here + and also this does not introduce any new security issues other than + as noted in the LFA base specification [RFC5286]. 8. References 8.1. Normative References - [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and - dual environments", RFC 1195, DOI 10.17487/RFC1195, - December 1990, . - [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, - . + . + + [RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for + IP Fast Reroute: Loop-Free Alternates", RFC 5286, + DOI 10.17487/RFC5286, September 2008, + . 8.2. Informative References + [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and + dual environments", RFC 1195, DOI 10.17487/RFC1195, + December 1990, . + + [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, + DOI 10.17487/RFC2328, April 1998, + . + [RFC3137] Retana, A., Nguyen, L., White, R., Zinin, A., and D. McPherson, "OSPF Stub Router Advertisement", RFC 3137, DOI 10.17487/RFC3137, June 2001, - . + . [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", RFC 4915, DOI 10.17487/RFC4915, June 2007, - . + . [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi Topology (MT) Routing in Intermediate System to Intermediate Systems (IS-ISs)", RFC 5120, DOI 10.17487/RFC5120, February 2008, - . - - [RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for - IP Fast Reroute: Loop-Free Alternates", RFC 5286, - DOI 10.17487/RFC5286, September 2008, - . + . [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, DOI 10.17487/RFC5305, October - 2008, . + 2008, . [RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, DOI 10.17487/RFC5308, October 2008, - . + . [RFC5838] Lindem, A., Ed., Mirtorabi, S., Roy, A., Barnes, M., and R. Aggarwal, "Support of Address Families in OSPFv3", RFC 5838, DOI 10.17487/RFC5838, April 2010, - . - - [RFC7916] Litkowski, S., Ed., Decraene, B., Filsfils, C., Raza, K., - Horneffer, M., and P. Sarkar, "Operational Management of - Loop-Free Alternates", RFC 7916, DOI 10.17487/RFC7916, - July 2016, . + . Authors' Addresses Pushpasis Sarkar (editor) - Individual + Arrcus, Inc. Email: pushpasis.ietf@gmail.com Shraddha Hegde Juniper Networks, Inc. Electra, Exora Business Park Bangalore, KA 560103 India Email: shraddha@juniper.net