1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 *
19 */
20
21 package org.apache.directory.server.dns.io.encoder;
22
23
24 /**
25 * 3. The DNAME Resource Record
26 *
27 * The DNAME RR has mnemonic DNAME and type code 39 (decimal).
28 *
29 * DNAME has the following format:
30 *
31 * <owner> <ttl> <class> DNAME <target>
32 *
33 * The format is not class-sensitive. All fields are required. The
34 * RDATA field <target> is a <domain-name> [DNSIS].
35 *
36 * The DNAME RR causes type NS additional section processing.
37 *
38 * The effect of the DNAME record is the substitution of the record's
39 * <target> for its <owner> as a suffix of a domain name. A "no-
40 * descendants" limitation governs the use of DNAMEs in a zone file:
41 *
42 * If a DNAME RR is present at a node N, there may be other data at N
43 * (except a CNAME or another DNAME), but there MUST be no data at
44 * any descendant of N. This restriction applies only to records of
45 * the same class as the DNAME record.
46 *
47 * This rule assures predictable results when a DNAME record is cached
48 * by a server which is not authoritative for the record's zone. It
49 * MUST be enforced when authoritative zone data is loaded. Together
50 * with the rules for DNS zone authority [DNSCLR] it implies that DNAME
51 * and NS records can only coexist at the top of a zone which has only
52 * one node.
53 *
54 * The compression scheme of [DNSIS] MUST NOT be applied to the RDATA
55 * portion of a DNAME record unless the sending server has some way of
56 * knowing that the receiver understands the DNAME record format.
57 * Signalling such understanding is expected to be the subject of future
58 * DNS Extensions.
59 *
60 * Naming loops can be created with DNAME records or a combination of
61 * DNAME and CNAME records, just as they can with CNAME records alone.
62 * Resolvers, including resolvers embedded in DNS servers, MUST limit
63 * the resources they devote to any query. Implementors should note,
64 * however, that fairly lengthy chains of DNAME records may be valid.
65 *
66 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
67 * @version $Rev: 501160 $, $Date: 2007-01-29 20:41:33 +0100 (Mo, 29 Jan 2007) $
68 */
69 public class DnameRecordEncoder
70 {
71 }