Text records are containers used by administrators to attach both human- and machine-readable notes to the zones. TXT records are used to validate, for example, email ownership, application licensing, or any information about a server, network, data center, company, or accounting data. The TXT record is formatted as standard UTF-8 ASCII text data.
All text data in the value field must be enclosed in quotation marks, and many different lines of text can share a single TXT record, as shown in Figure 3.21.
The pointer, or PTR, record is the reverse of what an A or quad A record does. The PTR will return the domain name when given the IP address; it maps the IP address to the domain name instead of the domain name to IP address mapping in standard DNS implementations, as shown in Figure 3.22.
The Alias record is proprietary to AWS and can map a zone apex, which is the raw domain name, to a fully qualified domain. Also, the Alias record maps your company domain name to the AWS internal DNS name. This allows for a user-friendly name that maps to the rather long and sometimes convoluted AWS domains. Another feature of using the Alias record is that Route 53 monitors the Alias record, and if the DNS changes on the backend, traffic will route to the new endpoint. Figure 3.23 shows the setup screen to configure an alias in the Route 53 web console.
The Service, or SRV, record redirects sessions for specific service types, such as VoIP or instant messaging sessions, to specific hosts and port numbers. The syntax is in the format of [priority] [weight] [port] [server host name] such as 1 10 5269 xmpp-server1.tipofthehat.com, as shown in Figure 3.24.
The Sender Policy Framework, or SPF, record was used to limit email spoofing and scammers and was used to validate the identity of the email sender. It has been deprecated and is not in common use because of interoperability issues. TXT records have replaced the use of SPF records. Figure 3.25 shows that Route 53 discourages the implementation of SPF records but still allows you to create them.
The Name Authority Pointer, or NAPTR, record is commonly used for Internet Telephony applications when mapping servers and user addresses in the Session Initiation Protocol (SIP) to convert phone numbers to URIs.
NAPTR record sets are used by Dynamic Delegation Discovery System (DDDS) applications to convert or replace one value with another. Figure 3.26 shows the Route 53 web console screen for the NAPTR record configuration.
The Certificate Authority Authorization, or CAA, record limits the certificate authorities (CAs) that can create TLS/SSL certificates in the domain. This is a whitelist of CAs that you allow to issue certificates for this domain or subdomain. Figure 3.27 shows the basic CAA resource record configuration.
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