@Override
    public void parseEntry(SpanObject span, SegmentObject segmentObject) {
        if (span.getSkipAnalysis()) {
            return;
        }
        if (log.isDebugEnabled()) {
            log.debug("service instance mapping listener parse reference");
        }
        if (!span.getSpanLayer().equals(SpanLayer.MQ)) {
            span.getRefsList().forEach(segmentReference -> {
                if (RefType.CrossProcess.equals(segmentReference.getRefType())) {
                    final String networkAddressUsedAtPeer = namingControl.formatServiceName(
                        segmentReference.getNetworkAddressUsedAtPeer());
                    if (config.getUninstrumentedGatewaysConfig().isAddressConfiguredAsGateway(
                        networkAddressUsedAtPeer)) {
                        /*
                         * If this network address has been set as an uninstrumented gateway, no alias should be set.
                         */
                        return;
                    }
                    final String serviceName = namingControl.formatServiceName(segmentObject.getService());
                    final String instanceName = namingControl.formatInstanceName(
                        segmentObject.getServiceInstance());

                    final NetworkAddressAliasSetup networkAddressAliasSetup = new NetworkAddressAliasSetup();
                    networkAddressAliasSetup.setAddress(networkAddressUsedAtPeer);
                    networkAddressAliasSetup.setRepresentService(serviceName);
                    networkAddressAliasSetup.setRepresentServiceNormal(true);
                    networkAddressAliasSetup.setRepresentServiceInstance(instanceName);
                    networkAddressAliasSetup.setTimeBucket(TimeBucket.getMinuteTimeBucket(span.getStartTime()));

                    sourceReceiver.receive(networkAddressAliasSetup);
                }

            });
        }
    }
NetworkAddressAliasMappingListener use the propagated data in the segment reference, set up the alias relationship
between network address and current service and instance. The alias relationship will be used in the {@link
RPCAnalysisListener#parseExit(SpanObject, SegmentObject)} to setup the accurate target destination service
and instance.

This is a key point of SkyWalking header propagation protocol.
oap-server/analyzer/agent-analyzer/src/main/java/org/apache/skywalking/oap/server/analyzer/provider/trace/parser/listener/NetworkAddressAliasMappingListener.java