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Networks > Applications > Flashcards

Applications Flashcards

1
Q

Process

A

program running within a host

-communicate with applicattion-layer protocol

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2
Q

user agent

A

interfaces with user “above” and network “below”
-implements user interface and application level protocol

Web: browser
Email: mail reader
streaming audio/ video: media player

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3
Q

application layer protocols (5)

A

one “piece” of an app

  • use communication services provided by lower level protocols (TCP, UDP)
  • types of messages exchanged (request/ response/ etc)
  • syntax of message types (what fields in messages and how fields are delineated)
  • semantics of fields
  • rules for when and how processes send&respond to messages
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4
Q

rlogin

A

logging into and executing commands on remote machines

only UNIX

simpler and more efficient than telnet

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5
Q

shell

A

application that reads and understands user commands and invokes corresponding programs

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6
Q

pro and con of letting TCP decide sizes of segments sent b/t client and server

A

pro: low network workload
con: slow responses

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7
Q

pros and con of forcing TCP to send 1 byte segments

A

Pro:
fast response time

con:
high workload

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8
Q

Nagle’s Algorithm

A

-get balance b/t response time and network workload

A TCP connection can have only 1 outstanding small segment

No additional small segments can be sent until that ACK is received (so the segment builds up and becomes large – in slow networks)

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9
Q

FTP (File Transfer Protocol)

A
  • one control connection for each FTP session
  • one data connection for each file transfer
  • server ports 20 & 21 reserved for FTP
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10
Q

Control connection

A
  • server waits for connection requests on port 21

- client sends connection requests to port 21 of server

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11
Q

Data connection

A
  • client chooses an unused port # and sends this # to server via control connection, using PORT command
  • server receives port # and establishes TCP connection to client
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12
Q

SMTP (Simple Mail transfer Protocol)

A

Sender’s Mail Transfer Agent establishes TCP connection with receiver’s Mail Transfer Agent

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13
Q

Mail transfer agent

A

program that performs SMTP protocol to actually deliver e-mails

(sendmail in Unix)

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14
Q

remote user agent

A
  • user agent that runs on a machine different from where mail storages are
  • need mail access protocol (POP, IMAP)
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15
Q

HTTP

A
  • Browsers request web pages from server using Hypertext Transfer Protocol
  • simple client-server transaction protocol
  • web’s application layer protocol
  • uses TCP
  • stateless (server keeps no info about past client requests)
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16
Q

URL

A

Objects on web are identified by Uniform Resource Locators (URL)

17
Q

Non persistent HTTP

A
  • at most 1 object is sent over TCP connection
  • requires at least 2 RTT’s per object

OS must do work for each TCP connection
-but browsers can open parallel TCP connections

18
Q

Persistent HTTP

with and without pipelining

A
  • multiple objects can be sent over 1 TCP connection
  • w/out pipelining: client issues new request only when previous one has been recieved (1 RTT for each object)
  • w/ pipelining: client sends requests as soon as it encounters referenced object. (~ 1 RTT for ALL referenced objects)
19
Q

POST method

A

web page includes form input

Input is uploaded to server in entity body

20
Q

URL method (GET)

A

Input is uploaded in URL field of request line

21
Q

PUT (HTTP/1.1)

A

uploads file in entity body to path speciefied in URL field

22
Q

Cookies (4 components)

A
  1. cookie header line in HTTP response message
  2. cookie header line in HTTP request message
  3. cookie file kept on user’s host and managed by user’s browser
  4. back-end database at Web site
23
Q

why web caching (proxy server)? (3)

A
  • reduce response time for client request
  • reduce traffic on an institutions access link
  • internet dense with caches enables “poor” content providers to effectively deliver content
24
Q

Content Distribution Networks (CDNs)

A
  • Content providers are its customers
  • replicates its customers’ content in CDN servers. When provider updates content, CDN updates servers
  • faster delivery
  • based on geographic locations
25
Q

problem with query flooding

A

excessive amount of network traffic

Networks (6 decks)

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