001/* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, 013 * software distributed under the License is distributed on an 014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 015 * KIND, either express or implied. See the License for the 016 * specific language governing permissions and limitations 017 * under the License. 018 * 019 */ 020 021package org.apache.directory.server.dns.io.encoder; 022 023 024/** 025 * 4. NAPTR RR Format 026 * 027 * 4.1 Packet Format 028 * 029 * The packet format of the NAPTR RR is given below. The DNS type code 030 * for NAPTR is 35. 031 * 032 * The packet format for the NAPTR record is as follows 033 * 1 1 1 1 1 1 034 * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 035 * +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 036 * | ORDER | 037 * +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 038 * | PREFERENCE | 039 * +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 040 * / FLAGS / 041 * +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 042 * / SERVICES / 043 * +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 044 * / REGEXP / 045 * +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 046 * / REPLACEMENT / 047 * / / 048 * +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 049 * 050 * <character-string> and <domain-name> as used here are defined in RFC 051 * 1035 [7]. 052 * 053 * ORDER 054 * A 16-bit unsigned integer specifying the order in which the NAPTR 055 * records MUST be processed in order to accurately represent the 056 * ordered list of Rules. The ordering is from lowest to highest. 057 * If two records have the same order value then they are considered 058 * to be the same rule and should be selected based on the 059 * combination of the Preference values and Services offered. 060 * 061 * PREFERENCE 062 * Although it is called "preference" in deference to DNS 063 * terminology, this field is equivalent to the Priority value in the 064 * DDDS Algorithm. It is a 16-bit unsigned integer that specifies 065 * the order in which NAPTR records with equal Order values SHOULD be 066 * processed, low numbers being processed before high numbers. This 067 * is similar to the preference field in an MX record, and is used so 068 * domain administrators can direct clients towards more capable 069 * hosts or lighter weight protocols. A client MAY look at records 070 * with higher preference values if it has a good reason to do so 071 * such as not supporting some protocol or service very well. 072 * 073 * The important difference between Order and Preference is that once 074 * a match is found the client MUST NOT consider records with a 075 * different Order but they MAY process records with the same Order 076 * but different Preferences. The only exception to this is noted in 077 * the second important Note in the DDDS algorithm specification 078 * concerning allowing clients to use more complex Service 079 * determination between steps 3 and 4 in the algorithm. Preference 080 * is used to give communicate a higher quality of service to rules 081 * that are considered the same from an authority standpoint but not 082 * from a simple load balancing standpoint. 083 * 084 * It is important to note that DNS contains several load balancing 085 * mechanisms and if load balancing among otherwise equal services 086 * should be needed then methods such as SRV records or multiple A 087 * records should be utilized to accomplish load balancing. 088 * 089 * FLAGS 090 * A <character-string> containing flags to control aspects of the 091 * rewriting and interpretation of the fields in the record. Flags 092 * are single characters from the set A-Z and 0-9. The case of the 093 * alphabetic characters is not significant. The field can be empty. 094 * 095 * It is up to the Application specifying how it is using this 096 * Database to define the Flags in this field. It must define which 097 * ones are terminal and which ones are not. 098 * 099 * SERVICES 100 * A <character-string> that specifies the Service Parameters 101 * applicable to this this delegation path. It is up to the 102 * Application Specification to specify the values found in this 103 * field. 104 * 105 * REGEXP 106 * A <character-string> containing a substitution expression that is 107 * applied to the original string held by the client in order to 108 * construct the next domain name to lookup. See the DDDS Algorithm 109 * specification for the syntax of this field. 110 * 111 * As stated in the DDDS algorithm, The regular expressions MUST NOT 112 * be used in a cumulative fashion, that is, they should only be 113 * applied to the original string held by the client, never to the 114 * domain name produced by a previous NAPTR rewrite. The latter is 115 * tempting in some applications but experience has shown such use to 116 * be extremely fault sensitive, very error prone, and extremely 117 * difficult to debug. 118 * 119 * REPLACEMENT 120 * A <domain-name> which is the next domain-name to query for 121 * depending on the potential values found in the flags field. This 122 * field is used when the regular expression is a simple replacement 123 * operation. Any value in this field MUST be a fully qualified 124 * domain-name. Name compression is not to be used for this field. 125 * 126 * This field and the REGEXP field together make up the Substitution 127 * Expression in the DDDS Algorithm. It is simply a historical 128 * optimization specifically for DNS compression that this field 129 * exists. The fields are also mutually exclusive. If a record is 130 * returned that has values for both fields then it is considered to 131 * be in error and SHOULD be either ignored or an error returned. 132 * 133 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a> 134 */ 135public class NameAuthorityPointerEncoder 136{ 137}