OSI Model

Question 1

osi

Answer 1

open systems interconnection

Question 2

layer 1

Answer 2

physical layer
bits
cables, radio frequencies, hubs, waps, media converters

Question 3

broadband

Answer 3

divides bandwidth into separate channels

cable tv

Question 4

baseband

Answer 4

uses all available frequency on a medium

ethernet

Question 5

multiplexing

Answer 5

get more out of limited network
simultaneous use of broadband
TDM, StatTDM, FDM

Question 6

layer 2

Answer 6

data link layer
MAC frames
1. media access control: physical addressing
2. logical link layer: ack, flow control, error control
NIC, bridges, switches\
add src and dest MACs

Question 7

layer 3

Answer 7

network layer
IP packets
routers, multilayer switches, IPv4/6, ICMP
add src and dest IPs

Question 8

icmp

Answer 8

internet control message protocol

send error messages and operation information about IP

Question 9

layer 4

Answer 9

transport layer
segments/datagrams
tcp, udp, 
load balancers, firewalls
add src and dest ports

Question 10

tcp

Answer 10

transmission control protocol
reliable, connection-oriented
flow control, windowing, acks, retransmissions

Question 11

udp

Answer 11

user diagram protocol
unreliable, connectionless
no windowing or retransmission or acks
audio/video streaming

Question 12

windowing

Answer 12

allows clients to adjust the amount of data sent in each segment
continually adjusts based on retransmission rates

Question 13

buffering

Answer 13

allocate memory to store segments if bandwidth is not available
when ready, transmit from buffer
if full, messages are dropped :(

Question 14

layer 5

Answer 14

session layer
data
setup, maintain, teardown session
H.323, netBIOS

Question 15

layer 6

Answer 15

presentation layer
data
format and secure
tls, ssl, html, ascii. php, js etc…

Question 16

layer 7

Answer 16

application layer
data
email: pop3, imap, smtp
web: http, https
dns, ftp/s, telnet, ssh, snmp

Question 17

encapsulation

Answer 17

putting headers/trailer around some data

layers 7->1

Question 18

decapsulation

Answer 18

removing headers/trailer around some data

layers 1->7

Question 19

pdu

Answer 19

protocol data unit

bits, frames, packets, segments/datagrams

Question 20

syn

Answer 20

tcp synchronization flag

Question 21

ack

Answer 21

tcp acknowledgement flag

Question 22

fin

Answer 22

tcp finished packet

tear down connection

Question 23

rst

Answer 23

tcp reset flag

used when unexpected packet is received

Question 24

psh

Answer 24

tcp push flag

give data priority

Question 25

urg

Answer 25

tcp urgent flag

gives packet most priority (ignore anything else in queue)

Question 26

ethertype

Answer 26

field to indicate which protocol is encapsulating