NSA COMPUTER NETWORK TEST
QUESTIONS WITH CORRECT ANSWERS
What is user space? - Answer-The section of memory in which normal user processes
run. Processes running in this space only have access to a limited part of this space
(the process's own space and any shared memory sections). Process in this space can
only access kernel space through controlled system calls.
What is kernel space? - Answer-The section of memory in which kernel processes run.
Processes running in this space have access to all memory spaces, user and kernel.
Significantly higher privilege than user space.
Name the seven layers of the *OSI model* - Answer-1: Physical
2: Data Link
3: Network
4: Transport
5: Session
6: Presentation
7: Application
Name the four layers of the *TCP/IP model* - Answer-1: Link
2: Internet
3: Transport
4: Application
What is encapsulation? - Answer-As data travels down the TCP/IP stack, the packet of
the higher layer becomes the payload of the packet of the next lower layer.
As data travels up the TCP/IP stack, the payload of each packet is extracted at each
layer of the stack.
What is the primary concern of the *Physical layer* of the OSI model? - Answer-The
transmission of raw bits
What are the primary 3 concerns of the *Data Link layer* of the OSI model? - Answer-1.
Grouping raw bits from the Physical layer in to frames
2. Detect and possibly correct errors from the Physical layer (checksum)
3. The transmission of data frames between nodes on a network
What are the 3 primary concerns of the *Network layer* of the OSI model? - Answer-1.
Provide an addressing scheme
2. The forwarding/routing of data packets between networks
3. Frame fragmentation with MTU field
,What is the primary concern of the *Transport layer* of the OSI model? - Answer-
Provide host-to-host communication services for applications (such as connection-
oriented communication, connectionless communication, reliability, flow control, and
multiplexing) through the transmission of data segments
What are the four primary concerns of the *Session layer* of the OSI model? - Answer-
Provides a mechanism for:
(1) Delimiting data flow
(2) Synchronizing data flow
(3) Maintaining state
(4) Checkpoint/recovery scheme
What are the four primary concerns of the *Presentation layer* of the OSI model? -
Answer-How data is formatted in a given session, including:
(1) Compression
(2) Encryption
(3) Byte-ordering
(4) Encoding
What is the primary concern of the *Application layer* of the OSI model? - Answer-
Provide services that allow end users to easily interface across the network
At what level of the OSI model does a *web application firewall* operate? - Answer-The
Application layer
At what level of the OSI model does a *router* operate? - Answer-The Network layer
(layer 3)
How does a router operate? - Answer-When a router receives a packet, it compares the
packet's destination IP address to each of its routing table entries. If the destination IP
address falls within the network range of one of the entries, the router forwards the
packet to the corresponding gateway. If the packet's destination IP address doesn't fall
within any of the routing table's network ranges, the packet is forwarded to the default
gateway.
True or false: a layer 3 switch can route packets between VLANs - Answer-True
At what level of the OSI model does a *layer 3 switch* operate? - Answer-The Network
layer (layer 3)
How does a switch operate? - Answer-When a switch receives a frame, it retrieves the
frame's destination MAC address and looks up the switch port corresponding to that
MAC address in the switch's content addressable memory (CAM) table. If it finds a
match, it forwards the frame to that switch port.
, At what level of the OSI model does a *switch* operate? - Answer-The Data Link layer
(layer 2)
At what level of the OSI model does a *layer 2 switch* operate? - Answer-The Data Link
layer (layer 2)
At what level of the OSI model does a *hub* operate? - Answer-The Physical layer
(layer 1)
What is a *repeater*? - Answer-An OSI layer 1 networking device that amplifies or
regenerates a signal before retransmitting it, expanding the network's coverage area.
At what level of the OSI model does a *repeater* operate? - Answer-The Physical layer
(layer 1)
At what level of the OSI model does a *cable* operate? - Answer-The Physical layer
(layer 1)
At what level of the OSI model does a *fiber cable* operate? - Answer-The Physical
layer (layer 1)
At what level of the OSI model does a *wireless transmission* operate? - Answer-The
Physical layer (layer 1)
At what level of the OSI model would *string, coax, Cat-6, or the air* be used? - Answer-
The Physical layer (layer 1)
What is a *bridge*? - Answer-An OSI layer 2 device that connects two networks in such
a way that they *function as a single network*.
In contrast to a router, which connects two or more networks such that they function as
independent but connected networks.
What is a *hub*? - Answer-An OSI layer 1 network device that connects multiple
devices together and makes them act as a single network segment. A hub broadcasts
the signals it receives to all connected devices (except for the sending device), greatly
decreasing network performance.
At what level of the OSI model does a *bridge* operate? - Answer-The Data Link layer
(layer 2)
What type of device is a *cable modem*? - Answer-A bridge
At what level of the OSI model does a *modem* operate? - Answer-The Data Link layer
(layer 2)
QUESTIONS WITH CORRECT ANSWERS
What is user space? - Answer-The section of memory in which normal user processes
run. Processes running in this space only have access to a limited part of this space
(the process's own space and any shared memory sections). Process in this space can
only access kernel space through controlled system calls.
What is kernel space? - Answer-The section of memory in which kernel processes run.
Processes running in this space have access to all memory spaces, user and kernel.
Significantly higher privilege than user space.
Name the seven layers of the *OSI model* - Answer-1: Physical
2: Data Link
3: Network
4: Transport
5: Session
6: Presentation
7: Application
Name the four layers of the *TCP/IP model* - Answer-1: Link
2: Internet
3: Transport
4: Application
What is encapsulation? - Answer-As data travels down the TCP/IP stack, the packet of
the higher layer becomes the payload of the packet of the next lower layer.
As data travels up the TCP/IP stack, the payload of each packet is extracted at each
layer of the stack.
What is the primary concern of the *Physical layer* of the OSI model? - Answer-The
transmission of raw bits
What are the primary 3 concerns of the *Data Link layer* of the OSI model? - Answer-1.
Grouping raw bits from the Physical layer in to frames
2. Detect and possibly correct errors from the Physical layer (checksum)
3. The transmission of data frames between nodes on a network
What are the 3 primary concerns of the *Network layer* of the OSI model? - Answer-1.
Provide an addressing scheme
2. The forwarding/routing of data packets between networks
3. Frame fragmentation with MTU field
,What is the primary concern of the *Transport layer* of the OSI model? - Answer-
Provide host-to-host communication services for applications (such as connection-
oriented communication, connectionless communication, reliability, flow control, and
multiplexing) through the transmission of data segments
What are the four primary concerns of the *Session layer* of the OSI model? - Answer-
Provides a mechanism for:
(1) Delimiting data flow
(2) Synchronizing data flow
(3) Maintaining state
(4) Checkpoint/recovery scheme
What are the four primary concerns of the *Presentation layer* of the OSI model? -
Answer-How data is formatted in a given session, including:
(1) Compression
(2) Encryption
(3) Byte-ordering
(4) Encoding
What is the primary concern of the *Application layer* of the OSI model? - Answer-
Provide services that allow end users to easily interface across the network
At what level of the OSI model does a *web application firewall* operate? - Answer-The
Application layer
At what level of the OSI model does a *router* operate? - Answer-The Network layer
(layer 3)
How does a router operate? - Answer-When a router receives a packet, it compares the
packet's destination IP address to each of its routing table entries. If the destination IP
address falls within the network range of one of the entries, the router forwards the
packet to the corresponding gateway. If the packet's destination IP address doesn't fall
within any of the routing table's network ranges, the packet is forwarded to the default
gateway.
True or false: a layer 3 switch can route packets between VLANs - Answer-True
At what level of the OSI model does a *layer 3 switch* operate? - Answer-The Network
layer (layer 3)
How does a switch operate? - Answer-When a switch receives a frame, it retrieves the
frame's destination MAC address and looks up the switch port corresponding to that
MAC address in the switch's content addressable memory (CAM) table. If it finds a
match, it forwards the frame to that switch port.
, At what level of the OSI model does a *switch* operate? - Answer-The Data Link layer
(layer 2)
At what level of the OSI model does a *layer 2 switch* operate? - Answer-The Data Link
layer (layer 2)
At what level of the OSI model does a *hub* operate? - Answer-The Physical layer
(layer 1)
What is a *repeater*? - Answer-An OSI layer 1 networking device that amplifies or
regenerates a signal before retransmitting it, expanding the network's coverage area.
At what level of the OSI model does a *repeater* operate? - Answer-The Physical layer
(layer 1)
At what level of the OSI model does a *cable* operate? - Answer-The Physical layer
(layer 1)
At what level of the OSI model does a *fiber cable* operate? - Answer-The Physical
layer (layer 1)
At what level of the OSI model does a *wireless transmission* operate? - Answer-The
Physical layer (layer 1)
At what level of the OSI model would *string, coax, Cat-6, or the air* be used? - Answer-
The Physical layer (layer 1)
What is a *bridge*? - Answer-An OSI layer 2 device that connects two networks in such
a way that they *function as a single network*.
In contrast to a router, which connects two or more networks such that they function as
independent but connected networks.
What is a *hub*? - Answer-An OSI layer 1 network device that connects multiple
devices together and makes them act as a single network segment. A hub broadcasts
the signals it receives to all connected devices (except for the sending device), greatly
decreasing network performance.
At what level of the OSI model does a *bridge* operate? - Answer-The Data Link layer
(layer 2)
What type of device is a *cable modem*? - Answer-A bridge
At what level of the OSI model does a *modem* operate? - Answer-The Data Link layer
(layer 2)
