EECS122 - Spring 2001 Communication NetworksCourse Objectives & ContentsOrganizationIntroductionWebWeb: ExampleSlide 7Slide 8Web: Locating ResourceWeb: ConnectionWeb: End-to-endWeb: PacketsWeb: BitsWeb: Points to rememberVoice Over IP: VoIPVoIP: General OperationsEECS122 - Spring 2001 Communication NetworksProf. Jean WalrandDepartment of EECSUniversity of CaliforniaBerkeleyCourse Objectives & ContentsExplain Internet and related networksCompare solutions, identify trends Technology:Links: ADSL, Cable Modem, OpticalLANs: EthernetRouters, SwitchesProtocols:Routing, Transport, ApplicationsOrganizationThree Lectures + 1 Discussion every weekGrading: HW: 20%, 2 Midterms: 30%, 1 Final: 30%, Projects: 20%Instructors: Prof. Jean WalrandTAs: Today: Introduction to networksFriday: Office hours, email addresses, TAsWeb site: See Prof. Walrand’s home pageIntroductionWebVoice over IPWebExampleLocating Resource: DNSConnectionEnd-to-endPacketsBitsPoints to rememberClick -> get pagepage from localor remote computerlink:http://cnn.comspecifies - protocol (http) - location (cnn.com)Web: ExampleWeb: ExampleClick -> get pagepage from localor remote computerlink:http://cnn.comspecifies - protocol (http) - location (cnn.com)Web: ExampleClick -> get pagepage from localor remote computerlink:http://cnn.comspecifies - protocol (http) - location (cnn.com)Web: Locating Resourcecnn.com is the name of a computer (and, implicitly, of a file in that computer)To find the address, the application uses a hierarchical directory service called theDomain Name Systeml o c a lc o mh o s tc n n . c o m ?c n n . c o m ?I P = a . b . c . dI P = a . b . c . dWeb: ConnectionThe protocol (http) sets up a connection between the host and cnn.com to transfer the pageThe connection transfers the page as a byte stream, without errors: pacing + error controlH o s tc n n . c o mWeb: End-to-endThe byte stream flows from end to end across many links and switches: routing (+ addressing)That stream is regulated and controlled by both ends: retransmission of erroneous or missing bytes; pacingH O S TC N N . C O Me n d - t o - e n d p a c i n g a n de r r o r c o n t r o lr o u t i n gWeb: PacketsThe network transports bytes grouped into packetsThe packets are “self-contained” and routers handle them one by oneThe end hosts worry about errors and pacing:Destination sends ACKsSource checks lossesCH O S T : BC N N . C O M : AA | B | # , C R C | b y t e sB : t oCWeb: BitsEquipment in each node sends the packets as a string of bitsThat equipment is not aware of the meaning of the bits0 1 0 1 1 . . . 0 1 1 . . . 1 1 0T r a n s m i t t e r P h y s i c a l M e d i u m R e c e i v e r0 1 0 1 1 . . . 0 1 1 . . . 1 1 0O p t i c a lC o p p e rW i r e l e s sWeb: Points to rememberSeparation of taskssend bits on a link: transmitter/receiver [clock, modulation,…]send packet on each hop [framing, error detection,…]send packet end to end [addressing, routing]pace transmissions [detect congestion]retransmit erroneous or missing packets [acks, timeout]find destination address from name [DNS]Scalabilityrouters don’t know about connectionsnames and addresses are hierarchicalVoice Over IP: VoIPGeneral OperationsVoIP: General OperationsGateways must reproduce the signaling and voiceSignaling: dialed digits, dial tone, ringingVoice: Packetize and absorb delay jitterNote: Routing problemI n t e r n e tP S T NP S T Ns i g n a l i n gv o i c e s i g n a
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