When the _presence._tcp service is used, presence is exchanged via the format described in the TXT Records section of this document. In particular, presence information is not pushed as in XMPP (see &rfc3921;). Instead, clients listen for presence announcements from other local entities. Recommended rates for sending updates can be found in Multicast DNS.
Because link-local communication does not involve the exchange of XMPP presence, it is not possible to use &xep0115; for capabilities discovery. Therefore, it is REQUIRED to instead include the node and ver TXT records (and OPTIONAL to include the ext TXT record). The values of these records MUST be the same as the values for the 'node', 'ver', and 'ext' attributes that are advertised for the application in XMPP presence (if any) via the Entity Capabilities protocol as described in XEP-0115.