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38 Cards in this Set
- Front
- Back
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What does the Physical Layer transmit?
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Bits
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What does the Data Link Layer organize data into?
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Frames
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What are the jobs of the data link layer?
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physical addressing (MAC addresses)
Flow control/access control Data link protocols: stop and wait, go back N, selective repeat |
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What does the Network layer organize data into?
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Packets
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What layer handles routing?
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Network Layer
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What is adaptive routing?
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the adaptation to changes in traffic and/or network topology
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what does "isolated" mean in terms of the Network layer?
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nodes only know of neighbors
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What does the term "nonisolated" mean in terms of the network layer
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Global routing info is used
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At which layer are IP addresses determined?
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Network layer
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What does the Transport layer do?
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provides reliability to higher layers
creates a connection between hosts |
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What are the basic operations of the Transport layer?
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establish service
tear down service flow control, buffering, multiplexing |
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what are the transport layers protocols?
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UDP and TCP
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which transport layer protocol is connectionless?
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UDP
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which transport layer protocol is connection-oriented?
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TCP
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What is the main goal of the session layer?
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Crash recovery by means of check pointing
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Which layer deals with encryption, and compression?
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Presentation layer
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Which layer involves DNS?
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Application layer
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What constitutes a centralized routing algorithm?
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when routing tables are constructed at a central node and distributed to the other imps
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What constitutes a decentralized algorithm
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Each imp constructs its own routing table
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True or False: a Routing table needs the whole path to an imp
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False, it needs the next hop it needs to take - it trusts the other imps to get to the final destination
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What is the the hot potato method in terms of adaptive routing?
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When a packet arrives, it is sent out as fast as possible in the shortest outgoing queue
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What is the backward learning method in terms of adaptive routing?
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Observing the history of arriving packets
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What is distributed routing in terms of adaptive routing?
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When a node exchanges info with its direct neighbor
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what is link state routing
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the act of a node discovering its neighbors and learning their net addresses
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What is reverse path forwarding?
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if packet comes in on "Best line" forward it on to others
else: discard packet |
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what are three reasons for congestion in routing
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1) imps are too slow
2) queues in imps fill up 3) lines are too slow |
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What are the five strategies for dealing with congestion?
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1) preallocate resources
2) allow packets to be discarded at will 3) restrict number of packets in the net 4) use flow control 5) choke off input when congestion occurs |
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True or False: a flat address contains information regarding the structure
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False - a flat address only identifies a node
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What sometimes acts as a router, and sometimes acts like a bridge?
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A brouter
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What does a repeater do?
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connects two compatible LANS
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what is the basis for transferring information through a bridge?
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MAC layer addresses
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What type of address carries information about the structure of the network?
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hierarchical address
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True or False: flow control is end-to-end
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True
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What is the purpose of the three-way handshake?
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synchronizing both ends of a connection by allowing both sides to agree upon initial sequence numbers.
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What is bastract syntax notation?
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a common network representation that each node translates
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What is the first layer that is concerned with information being exchanged?
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Presentation layer
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What does DES stand for, and what is it?
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Data Encryption Standard - a standard created by IBM. use same key to encrypt and decrypt
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what is public key cryptography?
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The act of publishing the key and the algorithm. Decryption key is still only known by you though.
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