Network Architecture for Cyberspace Joel Crichlow, Ph.D.
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Transcript of Network Architecture for Cyberspace Joel Crichlow, Ph.D.
Network Architecture for CyberspaceJoel Crichlow, Ph.D
Network Architecture
Layers
Protocols
Standards
ISO/OSI Reference Model◦ International Organization for Standardization/Open
Systems Interconnection TCP/IP
◦ Transmission Control Protocol/Internet Protocol
ISO/OSI
Physical Layer
Digital-to-Analog Conversion
Analog-to-Digital Conversion◦ Modulation/Demodulation - modem
Transmission Media
Multiplexing
Circuit Switching and Packet Switching
Errors◦ Error correcting codes◦ Error detecting codes
Transmission Media
Twisted pair Coaxial cable Optical fibers Wireless Transmission
MultiplexingFrequency Division Multiplexing (FDM)
MultiplexingTime Division Multiplexing (TDM)
user 1
Channel
4
Channel
3
Channel
2
Channel
1
user 3
user 4
user 2
Circuit Switching and Packet Switching Circuit Switching
◦ Complete end-to-end path for exclusive use throughout the duration of session
Message Switching◦ Store-and-forward
Packet Switching
Data Link Layer
Link management◦ Efficient and reliable transmission of information from
one node (host or PSN) in the network to a neighboring node
Frames◦ Constructed from packets received from upper layer
Frames Flag – Begin, End
Bit stuffing◦ For example, if the flag is 01111110, then no sequence of 6 ‘1’ bits is allowed, a
‘0’ bit is inserted (stuffed) after every sequence of five ‘1’ bits
FLC - kind of frame, sequence number and acknowledgement indication
CRC – polynomial code
Network Layer
Connection Oriented Service◦ Set up connection then transfer data
Connectionless Service◦ Transfer data without setting up connection◦ Acknowledged, Unacknowledged
Virtual Call◦ Virtual Circuit for all packets in right sequence
Datagram◦ Each packet handled independently
Routing
Flow Control
Routing Shortest Path
Best Route◦ number of hops◦ distance (usually km)◦ bandwidth◦ traffic◦ communication cost
Static Routing
Dynamic Routing
Distance vector Routing
Route
to
Preferred out line Distance in hops
A A 0
B B 1
C B 2
D G 2
E E 1
F E 2
G G 1
Table at Router A
Path vector routing Current path vector for router A
Route to Preferred outline Path
A A A
B B A-B
C B A-B-C
D G A-G-D
E E A-E
F E A-E-F
G G A-G
Dynamic routing
Link State routing◦ Determine the delay along the link to neighbors◦ Send this information to all the other routers◦ Use this information to establish the shortest path to
every other router
Flow control and congestion
Too much traffic can overwhelm the system Finite bandwidth, finite memory Processing overhead Dropped packets Re-sends
Transport Layer
Process-to-Process Network-wide Addressing
◦ Name Servers Service
◦ Connection oriented◦ Connectionless◦ Integrity of delivered messages◦ Flow control
Session Layer
Application-oriented flavor◦ Different characteristics may determine different
procedures◦ Distributed computation vs multimedia transfer
Session management◦ Multiple transport connections◦ Multiple sessions over single transport connection
Presentation Layer
Data Integrity◦Data formats◦Conversions
Security and Privacy◦Encryption
Application Layer
The User Layer Useful Open? Friendly?
TCP/IP
ISO/OSI?
Five Layers
TCP - Transmission Control Protocol◦ Connection Oriented
UDP – User Datagram Protocol◦ Connectionless
IP – Internet Protocol◦ Datagram service
Local Area Networks
Range◦ Limited
Topologies◦ Bus, Ring, Star, …
IEEE Standards◦ Widespread use
M M M
P P P P
Bus
C
C
C
CC
Ring
C
C
C
C
Star
Wireless Computing
Base Station Adhoc Networks WiFi Bluetooth
WiFi
(a) WiFi with base station; (b) WiFi without base station
Bluetooth
Bluetooth topology: (a) 1 piconet, (b) A scatternet of 3 piconets
Conclusion We looked at:
ISO/OSI Reference Model
TCP/IP
Local Area Networks
Wireless Computing