Network Architecture for Cyberspace Joel 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 Modulation/Demodulation Modem Analog-to-Digital Conversion 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

Multiplexing Frequency Division Multiplexing (FDM)

Multiplexing Time Division Multiplexing (TDM) user 1 user 3 Channel 4 2 Channel 1 user 4 user 2

Circuit Switching and Packet 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 Connectionless 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 number of hops distance (usually km) bandwidth traffic Shortest Path Best Route number of hops distance (usually km) bandwidth traffic communication cost Static Routing Dynamic Routing

Distance vector Routing Table at Router A Route to Preferred out line Distance in hops A B 1 C 2 D G E F

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 Topologies IEEE Standards Limited Bus, Ring, Star, … IEEE Standards Widespread use M M M Bus P P P P C C C Ring C C C C C Star C

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