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TCP/IP Tutorial and Technical Overview - IBM Redbooks

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In addition to TSIG, <strong>and</strong> GSS-TSIG, several RFCs extended the functionality of<br />

DNS such that it incorporated additional security methods. These additions,<br />

defined in RFC 4033 <strong>and</strong> referred to as the DNS Security Extensions (DNSSEC),<br />

allow DNS to authenticate the origin of data as well as negative responses to<br />

DNS queries. However, they do not provide confidentiality, access control lists,<br />

or protection against denial-of-service-attacks. New resource records relating to<br />

security were added by RFCs 4034 <strong>and</strong> 4398, <strong>and</strong> include:<br />

► DNSKEY (public key)<br />

► DS (delegation signer)<br />

► RRSIG (resource record digital signature)<br />

► NSEC (authenticated denial of existence)<br />

► CERT (public key certificates)<br />

Note that these RRs are also listed in Table 12-2 on page 438. Specific details<br />

about how the DNS protocol was modified to take advantage of these additions is<br />

in RFC 4035.<br />

12.2.1 Dynamic updates in the DDNS<br />

The DNS message format (shown in Figure 12-5 on page 440) was designed for<br />

the querying of a static DNS database. RFC 2136 defines a modified DNS<br />

message for updates, called the UPDATE DNS message, illustrated in<br />

Figure 12-13 on page 455. This message adds or deletes resource records in<br />

the DNS, <strong>and</strong> allows updates to take effect without the DNS having to be<br />

reloaded.<br />

454 <strong>TCP</strong>/<strong>IP</strong> <strong>Tutorial</strong> <strong>and</strong> <strong>Technical</strong> <strong>Overview</strong>

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