The architecture of distributed systems
Client/Server computing
The programming model used in constructing distributed systems
Socket programming
Example client/server systems and their application-layer protocols
The World-Wide Web (HTTP)
Reliable file transfer (FTP)
E-mail (SMTP & POP)
Internet Domain Name System (DNS)
Computers (hosts, routers) connected to the Internet have twoforms of names:
IP address — a 32 bit identifier used for addressing hosts and routing data to them
Hostname — an ASCII string used by applications
The DNS is an Internet-wide service that provides mappings between IP addresses and hostnames
The DNS is a distributed database implemented in a hierarchy of name servers
The DNS is also an application-layer protocol
Hosts and routers use name servers to resolve names (address/name translation)
Name resolution is an essential Internet function implemented as application-layer protocol