Application Layer Flashcards
Name 4 Network apps
Email
Streamed videos/audio
Social Networks
Search
Explain the Client-Server Architecture
The client communicates with the server and its IP address always changes.
The server acts as a Host, responding to requests from the client and its IP address is always the same.
What is a process?
Programs that are running within the host
Name three components of Email apps
- User agents
- Mail servers
- SMTP(Simple Mail Transfer Protocol)
Name 4 mail access protocols
SMTP
POP (delete and download)
IMAP (allows manipulation of stored msgs on server)
HTTP(gmail, hotmail)
Name 3 things cookies are used for?
Authorization
Shopping carts
Recommendations
What is a web cache?
A cache is a place to store something temporarily in a computing environment. Cache acts as both client and server without involving the original server. (proxy server)
What is a DNS?
Used to locate internet domain names and translate them into IP addresses.
What is a socket?
Interface (a “door”) into which application process can both send and receive messages.
Explain the P2P architecture
Peers request service from other peers, peers provide service to other peers in return. P2P architecture is self scalable.
What is inter-process communication?
Two process’ communicate within the same host
Explain process communication in the P2P architecture
Both the client and server process can carried out by applications
Why are port numbers important?
They help to identify process accurately with the combination of the IP address.
List two common port numbers and what they belong to
HTTP server :80
Mail Server: 25
What’s the difference between Open protocols and Proprietary protocols?
Open protocols allow for interoperability e.g. HTTP
Proprietary protocols are not e.g. Skype
Name 4 transport services that an application needs
(1) Data Integrity- e.g. file transactions
(2) Timing e.g. interactive games
(3) Throughput e.g. multimedia
(4) Security
What are the transport service requirements for: email, text messaging and interactive games?
Email- Data loss: none, Throughput: elastic, Time: none
Text Message-Data loss: none, throughput: elastic, time: none
Interactive games-Data loss: loss-tolerant, throughput: few kpbs, time: 100’s msec
What is the application layer protocol for the following: E-MAIL, WEB, FILE TRANSFER and STREAMING MULTIMEDIA?
SMTP
HTTP
FTP
SIP, RTP, proprietary
What is the transport layer protocol for the following: E-MAIL, WEB, FILE TRANSFER and STREAMING MULTIMEDIA?
TCP TCP TCP TCP or UDP TCP or UDP
What is a User agent?
Responsible for composing, editing and reading messages e.g. Outlook, iPhone email client
What is a Mail server?
Responsible for storing incoming messages and creating a message queue of messages to be sent out.
What happens when you send an email to someone?
1: Sender uses UA to compose a message
2: UA sends message to mail server it is then placed in a queue
3: Client side of SMTP opens TCP connection with recipients mail server
4: SMTP client sends the message to the recipient
5: Recipient’s mail server stores the messages in the mailbox
6: Recipient uses UA to read message
What are the 3 phases of transfer that SMTP employ?
- Handshaking
- Transfer of messages
- Closure
Why must SMTP messages be in 7 bit ASCII?
It allows for images and documents to be included in the message
