OSI Model
What layer number is the Physical layer of the OSI model?
1
At which OSI layer do we find bits?
1 or physical
At which OSI layer does a hub operate?
1 or physical
At which OSI layer does a signal repeater operate?
1 or physical
At which OSI layer is cat5 cable?
1 or physical
At which OSI layer is coaxial cable?
1 or physical
At which OSI layer is fiber-optic cable?
1 or physical
At which OSI layer is wireless signal?
1 or physical
What are the five non-routable IP address blocks?
10.x.x.x, 127.x.x.x, 169.254.x.x, 172.16-31.x.x, and 192.168.x.x.
What is the typical value for MTU (in bytes)?
1500
What layer number is the Data Link layer of the OSI model?
2
At which OSI layer do we find frames?
2 or datalink
At which OSI layer does a bridge operate?
2 or datalink
At which OSI layer does a switch operate?
2 or datalink
At which OSI layer is Ethernet?
2 or datalink
At which OSI layer is MAC Addressing?
2 or datalink
At which OSI layer is Physical Addressing?
2 or datalink
At which OSI layer is the Local Area Network?
2 or datalink
What layer number is the Network layer of the OSI model?
3
At which OSI layer are Wide Area Networks?
3 or network
At which OSI layer do we find packets?
3 or network
At which OSI layer does a gateway operate?
3 or network
At which OSI layer does a router operate?
3 or network
At which OSI layer is IP Addressing?
3 or network
At which OSI layer is Logical Addressing?
3 or network
At which OSI layer is Network Address Translation?
3 or network
At which OSI layer is Port Address Translation?
3 or network
At which OSI layer is the Internet?
3 or network
What layer number is the Transport layer of the OSI model?
4
At which OSI layer are software ports?
4 or transport
At which OSI layer do we find segments?
4 or transport
At which OSI layer is TCP?
4 or transport
At which OSI layer is UDP?
4 or transport
What layer number is the Session layer of the OSI model?
5
What layer number is the Presentation layer of the OSI model?
6
At which OSI layer is data compression?
6 or presentation
At which OSI layer is encryption / decryption?
6 or presentation
What layer number is the Application layer of the OSI model?
7
What is a hop?
A hop is the moving of a packet from one LAN to another.
What is a keep-alive?
A keep-alive is a message that is sent between two computers just to keep the connection from timing out and being dropped.
What is a software port?
A port is a number that indicates which computer program should receive the message.
How long do NAT address pool entries last?
Address pool entries often expire (a) after ten minutes, or (b) when the table is full the most stale entry expires.
What is garbage collection?
Garbage collection is a term for reclaiming resources that are no longer in use (or appear to be no longer in use). After collection, they can be recycled and used for something else.
How does a typical laptop computer discover its own MAC address?
It already knows it. It is burned in on the network card.
What is the purpose of TTL?
It reduces the risk of network loops.
Explain Man In The Middle?
Man in the middle is (a) a hacking technique. (b) Two computers believe they are talking to each other. (c) Instead they are talking through (by way of) a third computer.
What does having a routable address mean?
Packets can be sent to you by using your own IP address.
Which protocol provides for guaranteed delivery of information?
TCP, or Transmission Control Protocol
In NAT, how does the router remember the original sender?
The router keeps a table that matches outside port numbers with inside IP address and port number pairs.
Which protocol provides for fast (but not guaranteed) delivery of infor- mation?
UDP, or User Datagram Protocol
What is layer 7 of the OSI model?
application
What is the Protocol Data Unit at OSI layer 1?
bits
What is a two-port switch called?
bridge
What is layer 2 of the OSI model?
datalink
What is the Protocol Data Unit at OSI layer 2?
frame
What is a multi-port repeater called?
hub
What does MTU stand for?
maximum transmission (or transfer) unit
What does MAC stand for?
media access control
What is layer 3 of the OSI model?
network
What does NAT stand for?
network address translation
What is the Protocol Data Unit at OSI layer 3?
packet
What is layer 1 of the OSI model?
physical
What does PAT stand for?
port address translation
What is layer 6 of the OSI model?
presentation
What is a two-port hub called?
repeater
What is the Protocol Data Unit at OSI layer 4?
segment
What is layer 5 of the OSI model?
session
What is a multi-port bridge called?
switch
What does TTL stand for?
time to live
What does TCP stand for?
transmission control protocol
What is layer 4 of the OSI model?
transport
What does UDP stand for?
user datagram protocol
What does WAN stand for?
wide area network
