OSI MODEL

Question 1

Physical Layer Characteristics

Answer 1

PDU: Bits
Protocol: Bluetooth, TIA
Devices: Cable, Hub

Question 2

What are the 2 methods to utilize bandwidth?

Answer 2

Broadband and baseband

Question 3

Explain broadband and baseband

Answer 3

Broadband: Like cable tv, each channel share the same bandwidth
Baseband: Like phone call, 1 phone call at a time - use reference clock to allow for synchronous communication

Question 4

Mutiplexing

Answer 4

Simultaneous use of baseband connection

Question 5

Hub

Answer 5

A layer 1 networking device
Single collision domain, single broadcast domain
Use half duplex for communication n CSMA/CD

Question 6

Data Link Layer Characteristics

Answer 6

PDU: Frame
Device: Switch, NIC, Bridges
Protocols: Ethernet, PPP, ATM

Question 7

MAC Address

Answer 7

Physical address
48-bit (12 digit hexa letter) address assigned to a NIC
First 3 pairs are vendor code

Question 8

Logical Link Control LLC

Answer 8

Provide basic flow control, basic error control func, connection services, and ack receipt of messages
Work via MAC Address

Question 9

How communication are synchronized at Layer 2?

Answer 9

ISOCHRONOUS, SYNCHRONOUS, and ASYNCHRONOUS

Question 10

Isochronous

Answer 10

Network devices use a common reference clock and create time slot for transmission (less overhead compared to the other 2)

Question 11

Synchronous

Answer 11

uses a common reference clock
have beginning and ending frames and special control characters

Question 12

Asynchronous

Answer 12

each device uses its own internal clock
use stop and start bits

Question 13

Network Layers Characteristics

Answer 13

PDU: Packet
Devices: Routers, multilayer switches
Protocols: IPv4, IPv6, ICMP

Question 14

What are the 3 ways that data is routed or forwarded in layer 3?

Answer 14

Packet switching
Circuit switching
Message switching

Question 15

Packet switching

Answer 15

data divided into packets and forwarded based on IP
keep switching packet until it reaches the final destination IP

Question 16

Circuit switching

Answer 16

SAME PATH THE WHOLE TIME (it might changes path when session ends tho)

Question 17

Message switching

Answer 17

data divided into messages
can be stored and forwarded

Question 18

Route Discovery and Selection

Answer 18

Manually configured as a static route or dynamically thru a routing protocol

Question 19

Which path to send? (Network layer)

Answer 19

Router uses routing table to forward packets based on destination IP via protocols like EIGRP, RIP, OSPF

Question 20

Layer 3 Connection Services

Answer 20

Augment layer 2 connection services to improve reliability: flow control and packet reordering

Question 21

ICMP

Answer 21

Internet Control Message Protocol (ping, traceroute)
send error messages and operational info to an IP destination

Question 22

Transport layer characteristics

Answer 22

PDU: Segment, Datagram
Protocol: TCP, UDP
Devices: WAN Accelerators, Load balancer, firewalls

Question 23

TCP

Answer 23

Transmission Control Protocol
connection oriented - reliable
segment retransmission and flow control thru windowing
segment sequencing
acknowledging segment

Question 24

UDP

Answer 24

User Datagram Protocol
connection-less - unreiable
good for streaming video and audio
less buffering

Question 25

Windowing

Answer 25

Allows the client to adjust the amount of data in each segment To maximize thruput and bandwidth

Question 26

Buffering

Answer 26

Occurs when devices allocate memory to store segments if bandwidth isn’t readily available

Question 27

Session Layer Characteristics

Answer 27

PDU: Data Protocol: H.323, H.264, NetBIOS

Question 28

Session layer’ functions

Answer 28

Set up: checking user credential, assigning a number to session to identify them Maintain: transfer data, reestablish connection, acknowledgment receipt Close: ending a session after the transfer is done or when one of the party disconnects

Question 29

Presentation Layer Characteristics

Answer 29

PDU: Data Protocols: POP3, IMAP, SMTP

Question 30

Application Layer’s Function

Answer 30

Provides application-level services where users communicate w computers

Question 31

Application services

Answer 31

Unite communications between components from more than one network application (POP3, IMAP, SMTP)

Question 32

Service Advertisement

Answer 32

Sending out announcements to other devices in the network to state the service they offer

Question 33

TCP FLAGS

Answer 33

SYN: Synchronize connections ACK: Ack receipt SYN-ACK: FIN: Tear down connection created by 3 ways handshake RST: Used when received unexpected packets PSH: Give data priority URG: Prioritize packet immediately

Question 34

Ethernet MTU

Answer 34

1500 Bytes