@Override
    public RemoteData.Builder serialize() {
        final RemoteData.Builder builder = RemoteData.newBuilder();
        builder.addDataStrings(serviceId);
        builder.addDataIntegers(serviceLayer.value());
        builder.addDataStrings(relatedServiceId);
        builder.addDataIntegers(relatedServiceLayer.value());
        builder.addDataLongs(getTimeBucket());
        return builder;
    }
The service layer of the lower service.
oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/hierarchy/service/ServiceHierarchyRelationTraffic.java