Goals for Today s Class Type of Networks EE 122 Networks Protocols What is a Protocol Ion Stoica TAs Junda Liu DK Moon David Zats And the key concept of multiplexing http inst eecs berkeley edu ee122 fa09 Materials with thanks to Vern Paxson Jennifer Rexford and colleagues at UC Berkeley 1 What Global non digital Communication Network Do You Use Every Day 2 What s Another Such Network That You Use Every Day Roughly speaking how does it work 3 Taxonomy of Communication Networks 4 Taxonomy of Communication Networks Communication networks can be classified based on the way in which the nodes exchange information Communication Network Communication networks can be classified based on the way in which the nodes exchange information Communication Network Broadcast Communication Network 5 6 1 Broadcast Communication Networks Information transmitted by any node is received by every other node in the network Communication networks can be classified based on the way in which the nodes exchange information Examples Usually in LANs Local Area Networks Taxonomy of Communication Networks Communication Network E g Ethernet classical WiFi E g lecture Switched Communication Network What problems does this raise Problem 1 limited range Problem 2 privacy of communication Problem 3 coordinating access to the shared communication medium Multiple Access Problem Broadcast Communication Network 7 Switched Communication Networks 8 Taxonomy of Communication Networks Communication networks can be classified based on the way in which the nodes exchange information Communication Network Information transmitted along a path of intermediary nodes switches or routers Switched Communication Network Basic issue how the switches figure out the next hop along the path Broadcast Communication Network Circuit Switched Communication Network 9 Circuit Switching e g Phone Network Circuit Switching Establish source creates circuit to destination Transfer source sends data over the circuit Teardown source tears down circuit when done Nodes along the path store connection info Nodes generally reserve resources for the connection If circuit not available Busy signal 10 Node switch in a circuit switching network incoming links Node outgoing links No destination address since nodes know path 11 How does the node connect the incoming link to the outgoing 12 2 Circuit Switching With Human Operator Telephone Network Alexander Graham Bell 1876 Demonstrates the telephone at US Centenary Exhibition in Philadelphia 14 Timing in Circuit Switching Telephone Network Almon Brown Strowger 1839 1902 1889 Invents the girl less cuss less telephone system the mechanical switching system Host 1 Switch 1 Switch 2 Host 2 time 16 Timing in Circuit Switching Host 1 Switch 1 Switch 2 Timing in Circuit Switching Host 2 Host 1 Switch 1 Switch 2 Host 2 Transmission delay Circuit Establishment propagation delay between Host 1 and Switch1 time Circuit Establishment propagation delay between Host 1 and Switch1 time 17 18 3 Timing in Circuit Switching Host 1 Switch 1 Switch 2 Timing in Circuit Switching Host 2 Host 1 Switch 1 Transmission delay Transmission delay propagation delay between Host 1 and Switch1 Circuit Establishment Host 2 Switch 2 propagation delay between Host 1 and Switch1 Circuit Establishment propagation delay between Host 1 and Host 2 time time 19 Timing in Circuit Switching Host 1 Switch 1 Switch 2 20 Timing in Circuit Switching Host 2 Host 1 Switch 1 Transmission delay Transfer Transmission delay propagation delay between Host 1 and Switch1 Circuit Establishment Host 2 Switch 2 propagation delay between Host 1 and Host 2 propagation delay between Host 1 and Switch1 Circuit Establishment Transfer Information propagation delay between Host 1 and Host 2 Information time time Circuit Teardown 21 Circuit Switching Circuit Switching Multiplexing a Link Node switch in a circuit switching network incoming links Node outgoing links Time division Each circuit allocated certain time slots time How do the black and red circuits share the outgoing link 23 Frequency division frequency 22 Each circuit allocated certain frequencies time 24 4 Time Division Multiplexing Demultiplexing Frames Slots 0 1 2 3 4 5 5 Minute Break 0 1 2 3 4 5 Time divided into frames frames into slots Relative slot position inside a frame determines to which circuit data belongs E g slot 0 belongs to red circuit Requires synchronization between sender and receiver surprisingly non trivial In case of non permanent circuits If sender does not send data the circuit s capacity is lost Questions Before We Proceed Need to dynamically bind a slot to a circuit How to do this 25 Taxonomy of Communication Networks 26 Packet Switching Communication networks can be classified based on the way in which the nodes exchange information Data sent as chunks of formatted bit sequences Packets Packets have following structure Communication Network Header Switched Communication Network Circuit Switched Communication Network Broadcast Communication Network Packet Switched Communication Network Data Trailer sometimes Header and Trailer carry control information e g destination address checksum Each packet traverses the network from node to node along some path Routing based on header info Usually once a node receives the entire packet it stores it hopefully briefly and then forwards it to the next node Store and Forward Networks 27 Packet Switching Multiplexing Demultiplexing Packet Switching 28 Node in a packet switching network incoming links Node outgoing links Memory Data from any flow can be transmitted at any given time How to tell them apart Note for packet switching we use flow instead of circuit to denote packets sent by a sender to a receiver 29 Single flow can use the entire link capacity if it is alone Use meta data header to describe data 30 5 Taxonomy of Communication Networks Datagram Packet Switching Communication networks can be classified based on the way in which the nodes exchange information Communication Network Switched Communication Network Each packet is independently switched Broadcast Communication Network Circuit Switched Communication Network Packet Switched Communication Network Datagram Network 31 Timing of Datagram Packet Switching Host 1 Node 1 Example IP networks postal system Host 1 propagation delay between Host 1 and Node 1 Packet 1 Essentially chances are good that packets from different flows won t all arrive at the same time so we can get by without enough
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