Transcript The Application Layer

Reference Models
a)
Protocols and networks in the TCP/IP model initially.
Reference Models
Physical Layer / Data Link
•mechanical, electrical, and timing interfaces to the network
•algorithms for reliable, efficient communication between two adjacent machines
Network Layer
•getting packets form the source all the way to the destination (end-to-end transmission)
The Transport Layer
•reliable, cost-effective data transport form the source to the destination machine,
independently of the physical network
The Application Layer
•programming that does a real work for users
•determines the presentation of the data and controls the session
Connection Establishment (Transport Layer)
How a user process in host 1 establishes a connection with a
time-of-day server in host 2.
The Application Layer
• Domain Name System
The DNS Name Space
Resource Records
Name Servers
• Electronic Mail
The User Agent
Message Transfer
Final Delivery
• WWW
• other
The DNS Name Space
A portion of the Internet domain name space.
Resource Records
A portion of a possible DNS database for cs.vu.nl.
Name Servers
Part of the DNS name space showing the division into zones.
Name Servers (2)
How a resolver looks up a remote name in eight steps.
Electronic Mail
Agent
•
any interface for e-mail
Transfer
•
SMTP; simple mail transfer protocol – TCP connection to port 25 for simple
ASCII protocol.
Final Delivery
•
•
•
POP; post office protocol; ‘pop’ the message from server
IMAP; internet message access protocol; multiple features – creating and
desrtoying mailboxes…
Webmail; mail through browser
IMAP
A comparison of POP3 and IMAP.
The World Wide Web
• Static Web Documents
• Dynamic Web Documents
• HTTP – The HyperText Transfer Protocol
URLs – Uniform Resource Locaters
Some common URLs.
Statelessness and Cookies
Some examples of cookies.
HTML – HyperText Markup Language
(b)
(a) The HTML for a sample Web page. (b) The formatted page.
Multimedia
• Introduction to Audio
• Streaming Audio
• Internet Radio
• Introduction to Video
• Video on Demand