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What is the difference between a name server and a resolver ?

Bind is a name server.

A resolver is not a software, it is a collection of C functions in a systems libraries commonly referred to as such.

In windows

The resolver is a software component bundled in the Windows 2000 Transmission Control Protocol/Internet Protocol (TCP/IP) stack

In Linux

The resolver is a set of routines in the C library

What is the difference between an authoritative and a non-authoritative answer ?

The first query is authoritative, but then it can be cached, so all subsequent queries for that name could be non-authoritative answers.

aa is Authoritative Answere

8.8.8.8 (opendns -now google-) answers with a non authoritative answere.

Authoritative servers are servers that have been manually configured by an administrator to hold DNS Resource Records (RR) for a specific domain.

Some servers can also be configured to act as caching servers for zones over which they have no authority. Their answers are always non-authoritative.

Secondary servers are also authoritative servers.

The difference between primary and secondary servers is that only the primary servers hold the SOA record (Start-Of-Authority).

In this example, only dns-server.algerian-radio.dz holds the SOA records.

All authoritative servers are listed in NS records for the zone they have authority on.

The parent zone's name server must use delegation to child zones if one chooses to have different name servers for different zones.

What is a Glue Record ?

En recherchant sur Internet ce qu'était un Glue Record, ça m'a naivement paru idiot. Pourquoi avoir décidé que les enregistrements de type NS devaient contenir des noms de serveurs et non directement leurs IPs ? pourquoi toute cette gymnastique de mettre uniquement le nom, puis d'ajouter les IPs dans un Glue Record ? pourquoi est-ce que les concepteurs du protocol n'ont pas permis de mettre des IPs dans les records de type NS ?

Est-ce parce qu'un nom peut correspondre à plusieurs IPs ? Non puisque cela invaliderait le fait de demander plusieurs NS au cas où un name server tomberait en panne.

Je n'ai pas encore trouvé une réponse pertinente à cette question, je ne sais pas comment chercher d'ailleurs ( j'ai laissé une question sur developpez.com)

What is the difference between recursive and iterative queries

Servers that accecpt recursive queries can answer dns queries for domains they're not authoritative for, so they'll do the necessary dns queries to their forwarders (if they're configured to use one) or do the necessary iterative queries from root level down until they get to the specified zone and return the answer for their clients.

Servers that don't accept recursive queries won't answer their clients, so clients may retry with iterative queries.

Usually, DNS servers make iterative queries between them and client resolvers make dns queries to the company's dns server(s) or to the ISP's or to one of the public DNS servers (like google's or level3).


contact : @ychaouche yacinechaouche at yahoocom


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