Remove debtags references in section 6.10 sect.searching-packages
debtags is no longer a package, for now it seems the only option is aptitude.
Also without entering to aptitude something like
aptitude search "?tag(protocol::dns)"offers
p adns-tools - Asynchronous-capable DNS client utilities
p autofs-hesiod - Hesiod map support for autofs
i avahi-daemon - Demonio de mDNS/DNS-SD de Avahi
p avahi-discover - Interfaz de usuario del descubridor de servicios de avahi
p avahi-dnsconfd - Herramienta de configuración de DNS utilizando Avahi
i A avahi-utils - Herramientas de Avahi para navegar, publicar y descubrir
p bind9 - Internet Domain Name Server
p bind9-doc - Documentation for BIND 9
i bind9-host - utilidad de búsqueda DNS
p bootpc - Client to connect to a boot protocol (bootp) server
p chiark-scripts - chiark system administration scripts
p ddclient - address updating utility for dynamic DNS services
p dlint - Analiza información de zonas de DNS usando búsquedas en el servidor de n
p dns-browse - Front-ends to DNS search
p dns-flood-detector - detect abusive usage levels on high traffic nameservers
p dns2tcp - TCP-over-DNS tunnel server and client
p dnsmasq - Small caching DNS proxy and DHCP/TFTP server - system daemon
i A dnsmasq-base - Small caching DNS proxy and DHCP/TFTP server - executable
p dnsproxy - proxy for DNS queries
p dnssec-trigger - reconfiguration tool to make DNSSEC work
p dnstop - console tool to analyze DNS traffic
p dnstracer - trace DNS queries to the source
p dnswalk - Analiza zonas de información DNS con búsquedas en el servidor de nombres
p fpdns - remotely determine DNS server version
p gnome-nettool - Herramienta de información sobre la red para GNOME
p gwhois - generic Whois Client / Server
p hesiod - Project Athena's DNS-based directory service - utilities
p inadyn - simple and small dynamic DNS client with HTTPS support
p iodine - tool for tunneling IPv4 data through a DNS server
p ip2host - Resuelve direcciones IP a nombres de dominio en los registros del servid
p jdresolve - fast alternative to apache logresolve
p ldap2dns - LDAP based DNS management system
p libadns1-dev - Asynchronous-capable DNS client library (development)
p libasio-dev - cross-platform C++ library for network programming
p libasyncns-dev - Asynchronous name service query library development files
i libavahi-client-dev - Development files for the Avahi client library
p libavahi-glib-dev - Development headers for the Avahi GLib integration library
p libbind-confparser-perl - parser class for BIND configuration files
p libdns-zoneparse-perl - Perl extension for parsing and manipulating DNS Zone Files
p libgeo-ipfree-perl - module to look up the country of an IPv4 address
p libhesiod-dev - Project Athena's DNS-based directory service - development files
p libjmdns-java-doc - Documentation for Java implementation of multi-cast DNS
p libnet-abuse-utils-perl - Routines useful for processing network abuse
p libnet-dns-async-perl - Asynchronous DNS helper for high volume perl applications
p libnet-dns-perl - module to perform DNS queries
i A libnet-domain-tld-perl - list of currently available Top-level Domains (TLDs)
i A libnss-mdns - NSS module for Multicast DNS name resolution
p libpoe-component-client-dns-perl - POE Component for performing asynchronous DNS queries
p libudns-dev - async-capable DNS stub resolver library, development files
p libunbound-dev - static library, header files, and docs for libunbound
p mdns-scan - Scan for mDNS/DNS-SD services published on the local network
p nis - Network Information Service (NIS)
i A nodejs - evented I/O for V8 javascript - runtime executable
p nscd - biblioteca GNU C: demonio de la caché de servicio de nombres
p nsd - authoritative domain name server
p nslint - Lint for DNS files, checks integrity
p pdns-backend-ldap - LDAP backend for PowerDNS
p pdns-backend-mysql - MySQL backend for PowerDNS
p pdns-backend-pgsql - PostgreSQL backend for PowerDNS
p pdns-backend-pipe - pipe/coprocess backend for PowerDNS
p pdns-recursor - PowerDNS Recursor
p pdns-server - extremely powerful and versatile nameserver
p rblcheck - Tool to query DNSBL servers
p rbldnsd - small nameserver daemon designed for DNSBLs
p rdnssd - IPv6 recursive DNS server discovery daemon
i A resolvconf - name server information handler
p udns-utils - Several DNS-related utilities built on top of udns library
p unbound - validating, recursive, caching DNS resolver
p unscd - Micro Name Service Caching Daemon
p yaku-ns - small footprint, trivial to configure, DNS server