Some Questions Answers Q Will there be reserved Lab times A We asked for these but the scheduling folks are resisting Q Can we do the projects in groups A The first two projects are to be done individually We haven t yet decided about the third project Networks and Protocols EE 122 Intro to Communication Networks Fall 2006 MW 4 5 30 in Donner 155 Q What about the scheduling conflict with the finals for CS 162 and CS 194 A The instructors are aware of these and are trying to work out a general solution If need be we will have an alternative time for those students Vern Paxson TAs Dilip Antony Joseph and Sukun Kim http inst eecs berkeley edu ee122 Materials with thanks to Jennifer Rexford Ion Stoica and colleagues at Princeton and UC Berkeley 1 2 Taxonomy of Communication Networks Goals for Today s Class Type of Networks Communication networks can be classified based on the way in which the nodes exchange information And the key concept of multiplexing Co m m u n ic a t io n Ne t wo rk What s a Protocol Clients Servers Peer to Peer time permitting 3 Taxonomy of Communication Networks 4 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 Co m m u n ic a t io n Ne t wo rk E g Ethernet WiFi E g lecture Bro a d c a s t Co m m u n ic a t io n Ne t wo rk What problems does this raise Problem 1 limited range Problem 2 coordinating access to the shared communication medium Multiple Access Problem 5 6 1 Taxonomy of Communication Networks Switched Communication Networks Information transmitted along a path of intermediary nodes switches or routers Communication networks can be classified based on the way in which the nodes exchange information Co m m u n ic a t io n Ne t wo rk Swit c h e d Co m m u n ic a t io n Ne t wo rk Basic issue how the switches figure out the next hop along the path Bro a d c a s t Co m m u n ic a t io n Ne t wo rk Example and properties of a global switched communication network that you and millions of others use every day Another example 7 Taxonomy of Communication Networks Circuit Switching e g Phone Network Establish source creates circuit to destination Communication networks can be classified based on the way in which the nodes exchange information Node along the path store connection info Nodes generally reserve resources for the connection If circuit not available Busy signal Co m m u n ic a t io n Ne t wo rk Swit c h e d Co m m u n ic a t io n Ne t wo rk 8 Transfer source sends data over the circuit Bro a d c a s t Co m m u n ic a t io n Ne t wo rk No destination address since nodes know path Teardown source tears down circuit when done Circ u it Swit c h e d Co m m u n ic a t io n Ne t wo rk 9 Circuit Switching Telephone Network Node switch in a circuit switching network incoming links Node 10 Alexander Graham Bell 1876 Demonstrates the telephone at US Centenary Exhibition in Philadelphia outgoing links How does the node connect the incoming link to the outgoing 11 2 Telephone Network Circuit Switching With Human Operator Almon Brown Strowger 1839 1902 1889 Invents the girl less cuss less telephone system the mechanical switching system 13 Timing in Circuit Switching Host 1 Switch 1 Switch 2 Timing in Circuit Switching Host 2 Host 1 Switch 1 Switch 2 Host 2 propagation delay between Host 1 and Switch1 Circuit Establishment time time 15 Timing in Circuit Switching Host 1 Switch 1 Switch 2 16 Timing in Circuit Switching Host 2 Host 1 Transmission delay Circuit Establishment Switch 1 Switch 2 Host 2 Transmission delay 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 Timing in Circuit Switching Host 2 Switch 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 Host 2 propagation delay between Host 1 and Switch1 Circuit Establishment propagation delay between Host 1 and Host 2 Transfer Information time time 19 Timing in Circuit Switching Host 1 Switch 1 20 Circuit Switching Node switch in a circuit switching network Host 2 Switch 2 incoming links Transmission delay Node outgoing links propagation delay between Host 1 and Switch1 Circuit Establishment propagation delay between Host 1 and Host 2 Transfer Information time Circuit Teardown 21 Circuit Switching Multiplexing a Link Time division Each circuit allocated certain time slots How do the black and orange circuits share the outgoing link 22 Time Division Multiplexing Demultiplexing Frequency division Each circuit allocated certain frequencies Frames Slots 0 1 2 3 4 5 0 1 2 3 4 5 time frequency Time divided into frames frames into slots Relative slot position inside a frame determines to which conversation data belongs E g slot 0 belongs to orange conversation Requires synchronization between sender and receiver surprisingly difficult time In case of non permanent conversations Need to dynamically bind a slot to a conversation How to do this 23 If a conversation does not use its circuit the capacity is lost 24 4 Taxonomy of Communication Networks Packet Switching Data sent as chunks of formatted bit sequences Packets Communication networks can be classified based on the way in which the nodes exchange information Packets have following structure Co m m u n ic a t io n Ne t wo rk Header Swit c h e d Co m m u n ic a t io n Ne t wo rk Circ u it Swit c h e d Co m m u n ic a t io n Ne t wo rk Bro a d c a s t Co m m u n ic a t io n Ne t wo rk 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 Pa c ke t Swit c h e d Co m m u n ic a t io n Ne t wo rk Once a node receives the entire packet it stores it briefly and then forwards it to the next node Store and Forward Networks 25 Packet Switching Typically no capacity is allocated for packets 26 Packet Switching Multiplexing Demultiplexing Node in a packet switching network incoming links Node outgoing links Memory Data from any conversation can be transmitted at any given …
View Full Document
Unlocking...