DNS, Telnet & SSH

What is DNS?

A system that maps hostnames to IP addresses and vice-versa.

Why does DNS exist?

People prefer names, while networks use numeric IP addresses.

What does DNS uniquely map?

Hostnames to IP addresses and IP addresses to hostnames.

What makes name space necessary?

Every name must uniquely map to a single IP address.

What are the two types of names spaces?

Flat and hierarchical.

What is a domain?

A subtree of the DNS hierarchy representing administrative authority.

What does DNS rely on to scale globally?

A hierarchy of name servers (root, TLD, authoritative).

What is a zone in DNS?

A portion of the DNS namespace served by an authoritative server.

Difference between zone and domain?

A domain is a logical structure; a zone is the part a server manages.

How do primary and secondar DNS servers differ?

Primary loads zone data from disk; secondary copies via zone transfer.

What three sections is the DNS tree divided into?

Generic domains, country domains, inverse domains.

What are generic domains?

Top-level domains for organizations (.com, .edu, .org).

What do country domains represent?

Country-code top-level domains like .us, .uk, .jp.

What is inverse domain used for?

Mapping IP addresses back to names (reverse lookup).

What is name resolution

Converting names to addresses and vice versa.

What is iterative DNS resolution?

Resolver queries each server one-by-one using referals.

What are the two DNS message types?

Query and Response.

What sections can DNS responses contain?

Header, question, answer, authoritative, and additional records.

What does TELNET stand for?

Terminal network.

What is TELNET used for?

Establishing remote terminal sessions over a network.

What type of protocol is TELNET?

Standard TCP/IP protocol for virtual terminal service.

What does TELNET allow a local terminal to do?

Appear as a remote terminal on another system.

Who proposed the virtual terminal service TELNET uses?

ISO.

What type of application program is TELNET?

General-purpose client-server application.

What is SSH?

Secure Shell, a secure remote login protocol.

What transport protocol does SSH use?

TCP.

How does SSH compare to TELNET?

Provides encryption and more features; more secure.