Networks and Protocols EE 122 Intro to Communication Networks Fall 2006 MW 4 5 30 in Donner 155 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 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 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 2 1 Goals for Today s Class Type of Networks And the key concept of multiplexing What s a Protocol Clients Servers Peer to Peer time permitting 3 Taxonomy of Communication Networks 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 w o rk 4 2 Taxonomy of Communication Networks 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 w o rk Bro a d c a s t Co m m u n ic a t io n Ne t w o rk 5 Broadcast Communication Networks Information transmitted by any node is received by every other node in the network Examples Usually in LANs Local Area Networks E g Ethernet WiFi E g lecture What problems does this raise Problem 1 limited range Problem 2 coordinating access to the shared communication medium Multiple Access Problem 6 3 Taxonomy of Communication Networks 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 w o rk Sw it c h e d Co m m u n ic a t io n Ne t w o rk Bro a d c a s t Co m m u n ic a t io n Ne t w o rk 7 Switched Communication Networks Information transmitted along a path of intermediary nodes switches or routers Basic issue how the switches figure out the next hop along the path Example and properties of a global switched communication network that you and millions of others use every day Another example 8 4 Taxonomy of Communication Networks 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 w o rk Sw it c h e d Co m m u n ic a t io n Ne t w o rk Bro a d c a s t Co m m u n ic a t io n Ne t w o rk Circ u it Sw it c h e d Co m m u n ic a t io n Ne t w o rk 9 Circuit Switching e g Phone Network Establish source creates circuit to destination Node along the path store connection info Nodes generally reserve resources for the connection If circuit not available Busy signal Transfer source sends data over the circuit No destination address since nodes know path Teardown source tears down circuit when done 10 5 Circuit Switching Node switch in a circuit switching network incoming links Node outgoing links How does the node connect the incoming link to the outgoing 11 Telephone Network Alexander Graham Bell 1876 Demonstrates the telephone at US Centenary Exhibition in Philadelphia 6 Circuit Switching With Human Operator 13 Telephone Network Almon Brown Strowger 1839 1902 1889 Invents the girl less cuss less telephone system the mechanical switching system 7 Timing in Circuit Switching Host 1 Switch 1 Switch 2 Host 2 time 15 Timing in Circuit Switching Host 1 Circuit Establishment Switch 1 Switch 2 Host 2 propagation delay between Host 1 and Switch1 time 16 8 Timing in Circuit Switching Host 1 Switch 1 Switch 2 Host 2 Transmission delay propagation delay between Host 1 and Switch1 Circuit Establishment time 17 Timing in Circuit Switching Host 1 Switch 1 Switch 2 Host 2 Transmission delay Circuit Establishment propagation delay between Host 1 and Switch1 time 18 9 Timing in Circuit Switching Host 1 Switch 1 Switch 2 Host 2 Transmission delay propagation delay between Host 1 and Switch1 Circuit Establishment propagation delay between Host 1 and Host 2 time 19 Timing in Circuit Switching Host 1 Switch 1 Switch 2 Host 2 Transmission delay propagation delay between Host 1 and Switch1 Circuit Establishment Transfer propagation delay between Host 1 and Host 2 Information time 20 10 Timing in Circuit Switching Host 1 Switch 1 Switch 2 Host 2 Transmission delay 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 Node switch in a circuit switching network incoming links Node outgoing links How do the black and orange circuits share the outgoing link 22 11 Circuit Switching Multiplexing a Link Time division Frequency division Each circuit allocated certain frequencies frequency Each circuit allocated certain time slots time time 23 Time Division Multiplexing Demultiplexing Frames Slots 0 1 2 3 4 5 0 1 2 3 4 5 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 In case of non permanent conversations Need to dynamically bind a slot to a conversation How to do this If a conversation does not use its circuit the capacity is lost 24 12 Taxonomy of Communication Networks 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 w o rk Sw it c h e d Co m m u n ic a t io n Ne t w o rk Circ u it Sw it c h e d Co m m u n ic a t io n Ne t w o rk Bro a d c a s t Co m m u n ic a t io n Ne t w o rk Pa c ke t Sw it c h e d Co m m u n ic a t io n Ne t w o rk 25 Packet Switching Data sent as chunks of formatted bit sequences Packets Packets have following structure Header 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 Once a node receives the entire packet it stores it briefly and then forwards it to the next node Store and Forward Networks Typically no capacity is allocated for packets …
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