2. The Open Systems Interconnection Specifications Flashcards
Host 1 sent a SYN packet to Host 2. What will Host 2 send in response?
A. ACK
B. NAK
C. SYN/ACK
D. SYN/NAK
E. SYN
C.
A connection-oriented session is set up using what is called a three-way handshake. The transmitting host sends a SYN packet, the receiving host sends a SYN/ACK, and the transmitting host replies with the last ACK packet. The session is now set up.
TCP and UDP reside at which layer of the OSI model?
A. 1
B. 2
C. 3
D. 4
D.
TCP and UDP are Transport layer protocols. The transport layer is layer 4 of the OSI model.
Which layer of the OSI model provides an entry point for programs to acces the network infrastructure?
A. Application
B. Transport
C. Network
D. Physical
A.
The top layer of the OSI model gives applications acces to the services that allow network acces.
You are connected to a server on the Internet and you click a link on the server and receive a time-out message. What layer could be the source of this message?
A. Application
B. Transport
C. Network
D. Physical
A.
If the remote server is busy or does not respond to your web browser request, this is an Application layer problem.
Which layer of the OSI model is responsible for code and character-set conversion as well as recognizing data formats?
A. Application
B. Presentation
C. Session
D. Network
B.
The Presentation layer makes data “presentable” for the Application layer.
At which layers of the OSI model do bridges, hubs, and routers primarily operate, respectively?
A. Physical, Physical, Data Link
B. Data Link, Data Link, Network
C. Data Link, Physical, Network
D. Physical, Data Link, Network
C.
Bridges, like switches, are Data Link layer devices. Hubs, like repeaters, are Physical layer devices. Routers are Network layer devices.
Which layer of the OSI model is responsible for converting data into signals appropriate for the transmission medium?
A. Application
B. Network
C. Data Link
D. Physical
D.
The Physical layer’s job is to convert data into impulses that are designed for the wired or wireless medium beeing used on the attached segment.
A receiving host has failed to receive all the segments that it should acknowledge. What can the host do to improve the reliability of this communication session?
A. Send a different source port number
B. Restart the virtual circuit
C. Decrease the sequence number
D. Decrease the window size
D.
A receiving host can control the transmitter by using flow control (TCP uses windowing by default). By decreasing the window size, the receiving host can slow down the transmitting host so the receiving host does not overflow its buffers.
Which layer 1 devices can be used to enlarge the area covered by a single LAN segment? (Chooce two).
A. Firewall
B. NIC
C. Hub
D. Repeater
E. RJ-45 transceiver
C, D.
Not that you really want to enlarge a single collision domain, but a hub (multiport repeater) will provide this functionality for you.
Segmentation of a data stream happens at wich layer of the OSI model?
A. Physical
B. Data Link
C. Network
D. Transport
D.
The Transport layer receives large data streams from the upper layers and breaks thes up to smaller pieces called segments.
When data is encapsulated, which is the correct order?
A. Data, frame, packet, segment, bits
B. Segment, data, packet, frame, bits
C. Data, segment, packet, frame, bits
D. Data, segment, frame, packet, bits
C.
The encapsulation order is data, segment, packet, frame, bits.
What are two purposes for segmentation with a bridge? (Choose two).
A. To add more broadcast domains
B. To create more collision domains
C. To add more bandwith for users
D. To allow more broadcasts for users
B, C.
Bridges and Switches break up collision domains, which allows more bandwith for users.
Acknowledgments, sequencing, and flow control are characteristic of which OSI layer?
A. Layer 2
B. Layer 3
C. Layer 4
D. Layer 7
C.
A reliable Transport layer connection uses acknowledgements to make sure all data is received reliably. A reliable connection is defined by the use of acknowledgments, sequencing, and flow contyrol, which is characteristic of the Transport layer (layer 4).
Which of the following is true regarding sequencing and acknowledgments? (Choose all that apply).
A. The segments delivered are acknowledged back to the sender upon their reception.
B. If a segment is not received, the virtual circuit must be restarted from the beginning at a slower transmit interval.
C. Any segments not acknowledged are retransmitted.
D. Segments are sequenced back into their proper order upon arrival at their destination.
E. All segments are retransmitted on time slot intervalst.
A, C, D.
When sequencing and acknowledgments are usedm the segments delivered are acknowledged back to the sender upon their reception. At this point, any segments not acknowledgedvare retransmitted, and segments are sequenced back into their proper ordervupon arrival at their destination.
What is the purpose of flow control?
A. To ensure that data is retransmitted if an acknowledgment is not received.
B. To reassamble segments in the correct order at the destination device.
C. To provide a means for the receiver to gevern the amount of data sent by the sender.
D. To regulate the size of each segment.
C.
Flow control allows the receiving device to control the pace of the transmitting device so the receiving device’s buffer does not overflow.
