Editing DNS zone transfer (section)

===Multiple resource records===
Originally, in the actual data transfer each set of resource records for a single domain name and type was transferred in a separate response message from the server to the client. However, this is inefficient, and some DNS server software implemented optimizations, geared at allowing the response compression mechanism in the DNS protocol to reduce the total bandwidth requirements of data transfers, such as:
* performing "additional section processing" to include any "glue" resource record sets in the same response as an NS, SRV, or MX resource record set
* collecting all of the resource record sets relating to a single domain name together and sending them, if they fit, in a single response

Some clients were written to expect ''only'' the original response format, and would fail to perform data transfer if such optimizations were employed. Several DNS server packages thus have a configuration setting allowing administrators to specify the use of "single answer format" responses for those clients that require it.