Comp Networks Flashcards
What do packet switches do?
forward packets (chunks of data)
give examples of some communication links
Fiber
Copper
Radio
Sattiliete
What are networks
collection of devices, routers
What are protocols
control sending, receiving of messages
How to connect end systems to edge router?
residential access nets
institutional access networks (school, company)
mobile access networks (WiFi, 4G/5G)
Give an example of a WLAN
WIFI in home
Give an example of wide-area cellular access networks
4G/5G
What do data centre networks do?
Connects hundreds. to thousands of servers together and to the internet
When does queueing occur
When work arrives faster than it can be serviced
What happens if the memory in the router fills up?
packets can be dropped
What does FDM stand for?
Frequency Division Multiplexing
What does TDM stand for?
Time Division Multiplexing
Why are protocols needed for packet switching
reliable data transfer and congestion control
Given millions of access ISP’s, how long does it take to connect them together?
O(N^2)
How does packet delay occur
Packets queue in router buffers, waiting for turn for transmission
what are the cleint and server roles in process communication
Client: process that initiates communications
Server: process that waits to be contacted
What is the HTTP port number?
80
How many bits are in a IP address
32
What transport service does an app need?
Data integrity
Throughput
Timing
Security
What does UDP service not provide
reliability, flow control, congestion control, timing, throughput guarantee, security or connection setup
What does SMTP stand for and where is it used?
Simple mail transfer protocol
Emails
Where is SMTP protocol located?
between mail servers to send email messages
What are the three phases of SMTP transfer
SMTP handshaking (greeting)
SMTP transfer of messages
SMTP closure
What is the SMTP port number?
220
is HTTP stateless
yes
What is the difference between persistent and non-persistent HTTP
Persistent: multiple objects can be sent over a single TCP connection between the server and the client
Non: only one object
What is first party and third party cookies?
First party: tracking user behaviour on a given site
Third party: tracking user behaviour across multiple sites
Give examples of some DNS services
hostname to ip address translation
host aliasing
mail server aliasing
load distribution
Name some features about TCP
reliable, in-order delivery
congestion control
flow control
connection setup
Name some features about UDP
unreliable, unordered delivery
