Flashcards
Data Communications and Net-Centric Computing
Flashcards do conjunto (28)
- 1Repeateris an electronic device that receives a signal and the retransmits it at a higher level and/or higher power, onto the other side of an obstruction, so that the signal can cover longer distances
- 2Hubis a device for connecting multiple twisted pair or fiber optic Ethernet devices together and making them act as a single network segment
- 3Network switch or switching hubis a computer networking device that connects network segments
- 4Firewallis a technological barrier designed to prevent unauthorised or unwanted communications between computer networks or hosts
- 5Routeris a device that forwards data packets across computer networks. Routers perform the data "traffic directing" functions on the internet
- 6Protocolsdefine format, order of messages sent and received among network entities, and actions taken on message transmission, also receipt
- 7TCPTransmission Control Protocol
- 8TCP servicereliable, in-order byte stream data transfer, loss: acknowledgements and retransmissions
- 9Handshakingset up (prepare for) data transfer a head of time
- 10Apps using TCPHTTP (Web)
FTP (file transfer)
Telnet (remote login)
SMTP (email) - 11UDPUser Datagram Protocol
(internets connectionless service) - 12UDP Serviceunreliable data transfer, no flow control, no congestion control
- 13Apps using UDPstreaming media
teleconferencing
DNS
internet telephony - 14Circuit switchingdedicated circuit per call: telephone net
- 15Packet-switchingdata sent through net in discrete "chunks"
- 16Coaxial Cabletwo concentric copper conductors
bidirectional
baseband:
-single channel on cable
-legacy Ethernet
broadband:
-multiple channel on cable
-HFC - 17Fiber optic cable-glass fiber carrying light pulses, each pulse a bit
- high-speed point-to-point transmission ( eg. 5 Gps)
- low error rate: repeaters spaces far apart; immune to electromagnetic noise - 18how do loss and delay occur?packets queue in router buffers
-packet arrival rate to link exceeds output link capacity
-packets queue, wait for turn
-free buffers: arriving packets dropped if no free buffers
-lost packet may be transmitted by previous node, by source end system or not retransmitted at all - 19Four sources of packet delay- nodal processing (check bit errors)
- queueing (time waiting at output link for transmission)
-transmission(time required to push bits from buffer)
-propagation(distance/speed) - 20Internet Protocol StackApplication: supporting network applications
Transport: host-host data transfer
Network: routing of datagrams from source to destination
Link: data transfer b/w neighbouring network elements
Physical: bits "on the wire" - 21ttransL/R - time to transmit entire message
L = no of bits
R = bps - 22Analog Sygnalvaries in a smooth way over time
- 23digital signalmaintains a constant level then changes to another constant level
- 24periodic sygnalpattern repeated over time
- 25aperiodicpattern not repeated over time
- 26Flow controlrefers to a set of procedures used to restrict the amount of data that the sender can send before waiting for acknowledgement
- 27error controlin the data link layer is based on automatic repeat request, which is the retransmission of data
- 28Stop and wit ARQsource submits frame
destination recieves frome and replies with ack
source waits for ack
Informações
- Descrição
- FlashCards sobre Data Communications and Net-Centric Computing, criado por mea_red em 22-10-2014.
- Criado por
- mea_red · out 2014
- Atualizado
- 23 abr 2016
- Visualizações
- 8
- Avaliação