2 * Copyright © 2017 AT&T, Inc. and others. All rights reserved.
4 * This program and the accompanying materials are made available under the
5 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
6 * and is available at http://www.eclipse.org/legal/epl-v10.html
9 package org.opendaylight.transportpce.pce.networkanalyzer;
11 import java.util.ArrayList;
12 import java.util.HashMap;
13 import java.util.HashSet;
14 import java.util.List;
16 import java.util.Optional;
18 import java.util.concurrent.ExecutionException;
19 import java.util.stream.Collectors;
20 import org.opendaylight.mdsal.common.api.LogicalDatastoreType;
21 import org.opendaylight.transportpce.common.NetworkUtils;
22 import org.opendaylight.transportpce.common.ResponseCodes;
23 import org.opendaylight.transportpce.common.network.NetworkTransactionService;
24 import org.opendaylight.transportpce.pce.constraints.PceConstraints;
25 import org.opendaylight.yang.gen.v1.http.org.opendaylight.transportpce.pce.rev200128.PathComputationRequestInput;
26 import org.opendaylight.yang.gen.v1.http.org.openroadm.common.network.rev181130.Node1;
27 import org.opendaylight.yang.gen.v1.http.org.openroadm.network.types.rev181130.OpenroadmLinkType;
28 import org.opendaylight.yang.gen.v1.http.org.openroadm.network.types.rev181130.OpenroadmNodeType;
29 import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.network.rev180226.NetworkId;
30 import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.network.rev180226.Networks;
31 import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.network.rev180226.NodeId;
32 import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.network.rev180226.networks.Network;
33 import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.network.rev180226.networks.NetworkKey;
34 import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.network.rev180226.networks.network.Node;
35 import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.network.topology.rev180226.LinkId;
36 import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.network.topology.rev180226.Network1;
37 import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.network.topology.rev180226.networks.network.Link;
38 import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
39 //import org.opendaylight.yangtools.yang.common.Decimal64;
40 import org.slf4j.Logger;
41 import org.slf4j.LoggerFactory;
43 public class PceCalculation {
45 private static final Logger LOG = LoggerFactory.getLogger(PceCalculation.class);
46 private NetworkTransactionService networkTransactionService = null;
48 ///////////// data parsed from Input/////////////////
49 private PathComputationRequestInput input;
50 private String anodeId = "";
51 private String znodeId = "";
52 private String serviceFormatA = "";
53 private String serviceFormatZ = "";
54 private String serviceType = "";
55 private Long serviceRate = 0L;
57 private PceConstraints pceHardConstraints;
59 ///////////// Intermediate data/////////////////
60 private List<PceLink> addLinks = new ArrayList<>();
61 private List<PceLink> dropLinks = new ArrayList<>();
62 private HashSet<NodeId> azSrgs = new HashSet<>();
64 private PceNode aendPceNode = null;
65 private PceNode zendPceNode = null;
67 private List<Link> allLinks = null;
68 private List<Node> allNodes = null;
70 // this List serves graph calculation
71 private Map<NodeId, PceNode> allPceNodes = new HashMap<>();
72 // this List serves calculation of ZtoA path description
73 // TODO maybe better solution is possible
74 private Map<LinkId, PceLink> allPceLinks = new HashMap<>();
75 private Set<LinkId> linksToExclude = new HashSet<>();
76 private PceResult returnStructure;
78 private enum ConstraintTypes {
79 NONE, HARD_EXCLUDE, HARD_INCLUDE, HARD_DIVERSITY, SOFT_EXCLUDE, SOFT_INCLUDE, SOFT_DIVERSITY;
82 public PceCalculation(PathComputationRequestInput input, NetworkTransactionService networkTransactionService,
83 PceConstraints pceHardConstraints, PceConstraints pceSoftConstraints, PceResult rc) {
85 this.networkTransactionService = networkTransactionService;
86 this.returnStructure = rc;
88 this.pceHardConstraints = pceHardConstraints;
92 public void retrievePceNetwork() {
94 LOG.info("In PceCalculation retrieveNetwork: ");
97 returnStructure.setRC(ResponseCodes.RESPONSE_FAILED);
100 MapUtils.mapDiversityConstraints(allNodes, allLinks, pceHardConstraints);
103 returnStructure.setRC(ResponseCodes.RESPONSE_FAILED);
106 printNodesInfo(allPceNodes);
108 returnStructure.setRC(ResponseCodes.RESPONSE_OK);
112 private boolean parseInput() {
113 if (input.getServiceAEnd().getServiceFormat() == null || input.getServiceZEnd().getServiceFormat() == null
114 || input.getServiceAEnd().getServiceRate() == null) {
115 LOG.error("Service Format and Service Rate are required for a path calculation");
118 serviceFormatA = input.getServiceAEnd().getServiceFormat().getName();
119 serviceFormatZ = input.getServiceZEnd().getServiceFormat().getName();
120 serviceRate = input.getServiceAEnd().getServiceRate().toJava();
122 LOG.info("parseInput: A and Z :[{}] and [{}]", anodeId, znodeId);
123 if (!(serviceFormatA.equals(serviceFormatZ))) {
124 LOG.info("parseInput: different service format for A and Z not handled, will use service format from Aend");
125 } else if (serviceRate == 100L) {
126 switch (serviceFormatA) {
129 serviceType = "100GE";
132 serviceType = "OTU4";
135 serviceType = "ODU4";
138 LOG.debug("parseInput: unsupported service type: Format {} Rate 100L", serviceFormatA);
141 //switch(serviceRate) may seem a better option at first glance.
142 //But switching on Long or long is not directly possible in Java.
143 //And casting to int bumps the limit here.
144 //Passing by ENUM or String are possible alternatives.
145 //Maybe HashMap and similar options should also be considered here.
146 } else if ("Ethernet".equals(serviceFormatA)) {
147 //only rate 100L is currently supported except in Ethernet
148 if (serviceRate == 10L) {
149 serviceType = "10GE";
150 } else if (serviceRate == 1L) {
153 LOG.debug("parseInput: unsupported service type: Format Ethernet Rate {}", serviceRate);
156 LOG.debug("parseInput: unsupported service type: Format {} Rate {}",
157 serviceFormatA, serviceRate);
159 if ("ODU4".equals(serviceType) || "10GE".equals(serviceType) || "1GE".equals(serviceType)) {
160 anodeId = input.getServiceAEnd().getTxDirection().getPort().getPortDeviceName();
161 znodeId = input.getServiceZEnd().getTxDirection().getPort().getPortDeviceName();
163 anodeId = input.getServiceAEnd().getNodeId();
164 znodeId = input.getServiceZEnd().getNodeId();
167 returnStructure.setRate(input.getServiceAEnd().getServiceRate().toJava());
168 returnStructure.setServiceFormat(input.getServiceAEnd().getServiceFormat());
172 private boolean readMdSal() {
173 InstanceIdentifier<Network> nwInstanceIdentifier = null;
175 if (("OC".equals(serviceFormatA)) || ("OTU".equals(serviceFormatA)) || (("Ethernet".equals(serviceFormatA))
176 && (serviceRate == 100L))) {
178 LOG.info("readMdSal: network {}", NetworkUtils.OVERLAY_NETWORK_ID);
179 nwInstanceIdentifier = InstanceIdentifier.builder(Networks.class)
180 .child(Network.class, new NetworkKey(new NetworkId(NetworkUtils.OVERLAY_NETWORK_ID))).build();
181 } else if ("ODU".equals(serviceFormatA) || ("Ethernet".equals(serviceFormatA) && serviceRate == 10L)
182 || ("Ethernet".equals(serviceFormatA) && serviceRate == 1L)) {
183 LOG.info("readMdSal: network {}", NetworkUtils.OTN_NETWORK_ID);
184 nwInstanceIdentifier = InstanceIdentifier.builder(Networks.class)
185 .child(Network.class, new NetworkKey(new NetworkId(NetworkUtils.OTN_NETWORK_ID))).build();
187 LOG.info("readMdSal: service-rate {} / service-format not handled {}", serviceRate, serviceFormatA);
192 Optional<Network> nwOptional =
193 networkTransactionService.read(LogicalDatastoreType.CONFIGURATION, nwInstanceIdentifier).get();
194 if (nwOptional.isPresent()) {
195 nw = nwOptional.get();
196 LOG.debug("readMdSal: network nodes: nwOptional.isPresent = true {}", nw);
198 } catch (InterruptedException | ExecutionException e) {
199 LOG.error("readMdSal: Error reading topology {}", nwInstanceIdentifier);
200 networkTransactionService.close();
201 returnStructure.setRC(ResponseCodes.RESPONSE_FAILED);
202 throw new RuntimeException(
203 "readMdSal: Error reading from operational store, topology : " + nwInstanceIdentifier + " :" + e);
205 networkTransactionService.close();
208 LOG.error("readMdSal: network is null: {}", nwInstanceIdentifier);
211 allNodes = nw.getNode().stream().sorted((n1, n2) -> n1.getNodeId().getValue().compareTo(n2.getNodeId()
212 .getValue())).collect(Collectors.toList());
213 Network1 nw1 = nw.augmentation(Network1.class);
215 allLinks = nw1.getLink().stream().sorted((l1, l2) -> l1.getSource().getSourceTp().toString().compareTo(l2
216 .getSource().getSourceTp().toString())).collect(Collectors.toList());
218 LOG.warn("no otn links in otn-topology");
220 if (allNodes == null || allNodes.isEmpty()) {
221 LOG.error("readMdSal: no nodes ");
224 LOG.info("readMdSal: network nodes: {} nodes added", allNodes.size());
225 LOG.debug("readMdSal: network nodes: {} nodes added", allNodes);
227 if (allLinks == null || allLinks.isEmpty()) {
228 LOG.error("readMdSal: no links ");
231 LOG.info("readMdSal: network links: {} links added", allLinks.size());
232 LOG.debug("readMdSal: network links: {} links added", allLinks);
237 private boolean analyzeNw() {
239 LOG.debug("analyzeNw: allNodes size {}, allLinks size {}", allNodes.size(), allLinks.size());
241 if (("100GE".equals(serviceType)) || ("OTU4".equals(serviceType))) {
242 // 100GE service and OTU4 service are handled at the openroadm-topology layer
243 for (Node node : allNodes) {
247 LOG.debug("analyzeNw: allPceNodes size {}", allPceNodes.size());
249 if (aendPceNode == null || zendPceNode == null) {
250 LOG.error("analyzeNw: Error in reading nodes: A or Z do not present in the network");
253 for (Link link : allLinks) {
257 LOG.debug("analyzeNw: addLinks size {}, dropLinks size {}", addLinks.size(), dropLinks.size());
259 LOG.debug("analyzeNw: azSrgs size = {}", azSrgs.size());
260 for (NodeId srg : azSrgs) {
261 LOG.debug("analyzeNw: A/Z Srgs SRG = {}", srg.getValue());
264 for (PceLink link : addLinks) {
265 filteraddLinks(link);
267 for (PceLink link : dropLinks) {
268 filterdropLinks(link);
272 // ODU4, 10GE/ODU2e or 1GE/ODU0 services are handled at openroadm-otn layer
274 for (Node node : allNodes) {
275 validateOtnNode(node);
278 LOG.info("analyzeNw: allPceNodes {}", allPceNodes);
280 if (aendPceNode == null || zendPceNode == null) {
281 LOG.error("analyzeNw: Error in reading nodes: A or Z do not present in the network");
284 for (Link link : allLinks) {
289 LOG.info("analyzeNw: allPceNodes size {}, allPceLinks size {}", allPceNodes.size(), allPceLinks.size());
291 if ((allPceNodes.size() == 0) || (allPceLinks.size() == 0)) {
295 LOG.debug("analyzeNw: allPceNodes {}", allPceNodes);
296 LOG.debug("analyzeNw: allPceLinks {}", allPceLinks);
301 private boolean filteraddLinks(PceLink pcelink) {
303 NodeId nodeId = pcelink.getSourceId();
305 if (azSrgs.contains(nodeId)) {
306 allPceLinks.put(pcelink.getLinkId(), pcelink);
307 allPceNodes.get(nodeId).addOutgoingLink(pcelink);
308 LOG.debug("analyzeNw: Add_LINK added to source and to allPceLinks {}", pcelink.getLinkId());
312 // remove the SRG from PceNodes, as it is not directly connected to A/Z
313 allPceNodes.remove(nodeId);
314 LOG.debug("analyzeNw: SRG removed {}", nodeId.getValue());
319 private boolean filterdropLinks(PceLink pcelink) {
321 NodeId nodeId = pcelink.getDestId();
323 if (azSrgs.contains(nodeId)) {
324 allPceLinks.put(pcelink.getLinkId(), pcelink);
325 allPceNodes.get(nodeId).addOutgoingLink(pcelink);
326 LOG.debug("analyzeNw: Drop_LINK added to dest and to allPceLinks {}", pcelink.getLinkId());
330 // remove the SRG from PceNodes, as it is not directly connected to A/Z
331 allPceNodes.remove(pcelink.getDestId());
332 LOG.debug("analyzeNw: SRG removed {}", nodeId.getValue());
337 private boolean validateLink(Link link) {
338 LOG.info("validateLink: link {} ", link);
340 NodeId sourceId = link.getSource().getSourceNode();
341 NodeId destId = link.getDestination().getDestNode();
342 PceNode source = allPceNodes.get(sourceId);
343 PceNode dest = allPceNodes.get(destId);
345 if (source == null) {
346 LOG.debug("validateLink: Link is ignored due source node is rejected by node validation - {}",
347 link.getSource().getSourceNode().getValue());
351 LOG.debug("validateLink: Link is ignored due dest node is rejected by node validation - {}",
352 link.getDestination().getDestNode().getValue());
356 if (("100GE".equals(serviceType)) || ("OTU4".equals(serviceType))) {
357 // 100GE or OTU4 services are handled at WDM Layer
358 PceLink pcelink = new PceLink(link, source, dest);
359 if (!pcelink.isValid()) {
360 dropOppositeLink(link);
361 LOG.error(" validateLink: Link is ignored due errors in network data or in opposite link");
364 LinkId linkId = pcelink.getLinkId();
365 if (validateLinkConstraints(pcelink).equals(ConstraintTypes.HARD_EXCLUDE)) {
366 dropOppositeLink(link);
367 LOG.debug("validateLink: constraints : link is ignored == {}", linkId.getValue());
370 switch (pcelink.getlinkType()) {
373 allPceLinks.put(linkId, pcelink);
374 source.addOutgoingLink(pcelink);
375 LOG.debug("validateLink: {}-LINK added to allPceLinks {}",
376 pcelink.getlinkType(), pcelink);
379 pcelink.setClient(source.getRdmSrgClient(pcelink.getSourceTP().toString()));
380 addLinks.add(pcelink);
381 LOG.debug("validateLink: ADD-LINK saved {}", pcelink);
384 pcelink.setClient(dest.getRdmSrgClient(pcelink.getDestTP().toString()));
385 dropLinks.add(pcelink);
386 LOG.debug("validateLink: DROP-LINK saved {}", pcelink);
389 // store separately all SRG links directly
390 azSrgs.add(sourceId);
392 if (!dest.checkTP(pcelink.getDestTP().toString())) {
394 "validateLink: XPONDER-INPUT is rejected as NW port is busy - {} ", pcelink);
397 if (dest.getXpdrClient(pcelink.getDestTP().toString()) != null) {
398 pcelink.setClient(dest.getXpdrClient(pcelink.getDestTP().toString()));
400 allPceLinks.put(linkId, pcelink);
401 source.addOutgoingLink(pcelink);
402 LOG.debug("validateLink: XPONDER-INPUT link added to allPceLinks {}", pcelink);
404 // does it mean XPONDER==>>SRG ?
406 // store separately all SRG links directly
409 if (!source.checkTP(pcelink.getSourceTP().toString())) {
411 "validateLink: XPONDER-OUTPUT is rejected as NW port is busy - {} ", pcelink);
414 if (source.getXpdrClient(pcelink.getSourceTP().toString()) != null) {
415 pcelink.setClient(source.getXpdrClient(pcelink.getSourceTP().toString()));
417 allPceLinks.put(linkId, pcelink);
418 source.addOutgoingLink(pcelink);
419 LOG.debug("validateLink: XPONDER-OUTPUT link added to allPceLinks {}", pcelink);
422 LOG.warn("validateLink: link type is not supported {}", pcelink);
426 } else if (("ODU4".equals(serviceType)) || ("10GE".equals(serviceType)) || ("1GE".equals(serviceType))) {
427 // ODU4, 1GE and 10GE services relying on ODU2, ODU2e or ODU0 services are handled at OTN layer
428 PceLink pceOtnLink = new PceLink(link, source, dest);
430 if (!pceOtnLink.isOtnValid(link, serviceType)) {
431 dropOppositeLink(link);
432 LOG.error(" validateLink: Link is ignored due errors in network data or in opposite link");
436 LinkId linkId = pceOtnLink.getLinkId();
437 if (validateLinkConstraints(pceOtnLink).equals(ConstraintTypes.HARD_EXCLUDE)) {
438 dropOppositeLink(link);
439 LOG.debug("validateLink: constraints : link is ignored == {}", linkId.getValue());
443 switch (pceOtnLink.getlinkType()) {
445 if (dest.getXpdrClient(pceOtnLink.getDestTP().toString()) != null) {
446 pceOtnLink.setClient(dest.getXpdrClient(pceOtnLink.getDestTP().toString()));
449 allPceLinks.put(linkId, pceOtnLink);
450 source.addOutgoingLink(pceOtnLink);
451 LOG.info("validateLink: OTN-LINK added to allPceLinks {}", pceOtnLink);
454 LOG.warn("validateLink: link type is not supported {}", pceOtnLink);
459 LOG.error(" validateLink: Unmanaged service type {}", serviceType);
465 private boolean validateNode(Node node) {
466 LOG.debug("validateNode: node {} ", node);
468 // PceNode will be used in Graph algorithm
469 Node1 node1 = node.augmentation(Node1.class);
471 LOG.error("getNodeType: no Node1 (type) Augmentation for node: [{}]. Node is ignored", node.getNodeId());
474 OpenroadmNodeType nodeType = node1.getNodeType();
476 PceOpticalNode pceNode = new PceOpticalNode(node, nodeType, node.getNodeId(),
477 input.getServiceAEnd().getServiceFormat(), "optical");
478 pceNode.validateAZxponder(anodeId, znodeId);
479 pceNode.initWLlist();
481 if (!pceNode.isValid()) {
482 LOG.warn(" validateNode: Node is ignored");
486 if (validateNodeConstraints(pceNode).equals(ConstraintTypes.HARD_EXCLUDE)) {
489 if ((pceNode.getSupNetworkNodeId().equals(anodeId) && (this.aendPceNode == null))
490 && (Boolean.TRUE.equals(endPceNode(nodeType, pceNode.getNodeId(), pceNode)))) {
491 this.aendPceNode = pceNode;
493 if ((pceNode.getSupNetworkNodeId().equals(znodeId) && (this.zendPceNode == null))
494 && (Boolean.TRUE.equals(endPceNode(nodeType, pceNode.getNodeId(), pceNode)))) {
495 this.zendPceNode = pceNode;
498 allPceNodes.put(pceNode.getNodeId(), pceNode);
499 LOG.debug("validateNode: node is saved {}", pceNode.getNodeId().getValue());
503 private boolean validateOtnNode(Node node) {
505 LOG.info("validateOtnNode: {} ", node.getNodeId().getValue());
506 // PceOtnNode will be used in Graph algorithm
507 if (node.augmentation(Node1.class) != null) {
508 OpenroadmNodeType nodeType = node.augmentation(Node1.class).getNodeType();
510 PceOtnNode pceOtnNode = new PceOtnNode(node, nodeType, node.getNodeId(), "otn", serviceType);
511 pceOtnNode.validateXponder(anodeId, znodeId);
513 if (!pceOtnNode.isValid()) {
514 LOG.warn(" validateOtnNode: Node {} is ignored", node.getNodeId().getValue());
517 if (validateNodeConstraints(pceOtnNode).equals(ConstraintTypes.HARD_EXCLUDE)) {
520 if (pceOtnNode.getNodeId().getValue().equals(anodeId) && this.aendPceNode == null) {
521 this.aendPceNode = pceOtnNode;
523 if (pceOtnNode.getNodeId().getValue().equals(znodeId) && this.zendPceNode == null) {
524 this.zendPceNode = pceOtnNode;
526 allPceNodes.put(pceOtnNode.getNodeId(), pceOtnNode);
527 LOG.info("validateOtnNode: node {} is saved", node.getNodeId().getValue());
530 LOG.error("ValidateOtnNode: no node-type augmentation. Node {} is ignored", node.getNodeId().getValue());
534 // if (mode == "AZ") {
535 // pceOtnNode.validateAZxponder(anodeId, znodeId);
536 // } else if (mode == "intermediate") {
537 // pceOtnNode.validateIntermediateSwitch();
539 // LOG.error("validateOtnNode: unproper mode passed to the method : {} not supported", mode);
544 private ConstraintTypes validateNodeConstraints(PceNode pcenode) {
545 if (pceHardConstraints.getExcludeSupNodes().isEmpty() && pceHardConstraints.getExcludeCLLI().isEmpty()) {
546 return ConstraintTypes.NONE;
548 if (pceHardConstraints.getExcludeSupNodes().contains(pcenode.getSupNetworkNodeId())) {
549 LOG.info("validateNodeConstraints: {}", pcenode.getNodeId().getValue());
550 return ConstraintTypes.HARD_EXCLUDE;
552 if (pceHardConstraints.getExcludeCLLI().contains(pcenode.getSupClliNodeId())) {
553 LOG.info("validateNodeConstraints: {}", pcenode.getNodeId().getValue());
554 return ConstraintTypes.HARD_EXCLUDE;
556 return ConstraintTypes.NONE;
559 private ConstraintTypes validateLinkConstraints(PceLink link) {
560 if (pceHardConstraints.getExcludeSRLG().isEmpty()) {
561 return ConstraintTypes.NONE;
564 // for now SRLG is the only constraint for link
565 if (link.getlinkType() != OpenroadmLinkType.ROADMTOROADM) {
566 return ConstraintTypes.NONE;
569 List<Long> constraints = new ArrayList<>(pceHardConstraints.getExcludeSRLG());
570 constraints.retainAll(link.getsrlgList());
571 if (!constraints.isEmpty()) {
572 LOG.info("validateLinkConstraints: {}", link.getLinkId().getValue());
573 return ConstraintTypes.HARD_EXCLUDE;
576 return ConstraintTypes.NONE;
579 private void dropOppositeLink(Link link) {
580 LinkId opplink = MapUtils.extractOppositeLink(link);
582 if (allPceLinks.containsKey(opplink)) {
583 allPceLinks.remove(opplink);
585 linksToExclude.add(opplink);
589 private Boolean endPceNode(OpenroadmNodeType openroadmNodeType, NodeId nodeId, PceOpticalNode pceNode) {
590 switch (openroadmNodeType) {
592 pceNode.initSrgTps();
593 this.azSrgs.add(nodeId);
596 pceNode.initXndrTps();
599 LOG.warn("endPceNode: Node {} is not SRG or XPONDER !", nodeId);
603 if (!pceNode.isValid()) {
604 LOG.error("validateNode : there are no availaible wavelengths in node {}", pceNode.getNodeId().getValue());
610 public PceNode getaendPceNode() {
614 public PceNode getzendPceNode() {
618 public Map<NodeId, PceNode> getAllPceNodes() {
619 return this.allPceNodes;
622 public Map<LinkId, PceLink> getAllPceLinks() {
623 return this.allPceLinks;
626 public String getServiceType() {
630 public PceResult getReturnStructure() {
631 return returnStructure;
634 private static void printNodesInfo(Map<NodeId, PceNode> allPceNodes) {
635 allPceNodes.forEach(((nodeId, pceNode) -> {
636 LOG.info("In printNodes in node {} : outgoing links {} ", pceNode.getNodeId().getValue(),
637 pceNode.getOutgoingLinks());