A closer look at network structure: network edge: >mobile network hosts:clients and servers global ISP ·servers often in data centers home access networks, network regional ISP physical media: wired,wireless communication links network core. interconnected routers institutional ■network of networks network Introduction 1-11
Introduction A closer look at network structure: network edge: hosts: clients and servers servers often in data centers access networks, physical media: wired, wireless communication links network core: interconnected routers network of networks mobile network global ISP regional ISP home network institutional network 1-11
Access networks and physical media Q:How to connect end systems to edge router? residential access nets institutional access networks (school, company) mobile access networks keep in mind: bandwidth (bits per second)of access network? shared or dedicated? Introduction 1-12
Introduction Access networks and physical media Q: How to connect end systems to edge router? residential access nets institutional access networks (school, company) mobile access networks keep in mind: bandwidth (bits per second) of access network? shared or dedicated? 1-12
Access net:digital subscriber line ΘS) central office telephone network DSL splitter modem DSLAM ISP voice,data transmitted at different frequencies over DSL access dedicated line to central office multiplexer use existing telephone line to central office DSLAM data over DSL phone line goes to Internet voice over DSL phone line goes to telephone net 2.5 Mbps upstream transmission rate (typically 1 Mbps) 24 Mbps downstream transmission rate(typically 10 Mbps) Introduction 1-13
Introduction Access net: digital subscriber line (DSL) central office ISP telephone network DSLAM voice, data transmitted at different frequencies over dedicated line to central office use existing telephone line to central office DSLAM data over DSL phone line goes to Internet voice over DSL phone line goes to telephone net < 2.5 Mbps upstream transmission rate (typically < 1 Mbps) < 24 Mbps downstream transmission rate (typically < 10 Mbps) DSL modem splitter DSL access multiplexer 1-13
Access net:cable network cable headend cable splitter modem 0 V N I DD D D D D 0 E E E E E E TT O OIOIOIOIOIOIAIAIL 123456789 Channels frequency division multiplexing:different channels transmitted in different frequency bands Introduction 1-14
Introduction Access net: cable network cable modem splitter … cable headend Channels V I D E O V I D E O V I D E O V I D E O V I D E O V I D E O D A T A D A T A C O N T R O L 1 2 3 4 5 6 7 8 9 frequency division multiplexing: different channels transmitte d in different frequency bands 1-14
Access net:cable network cable headend cable splitter modem CMTS cable modem termination system data,TV transmitted at different frequencies over shared cable ISP distribution network HFC:hybrid fiber coax asymmetric:up to 30Mbps downstream transmission rate,2 Mbps upstream transmission rate network of cable,fiber attaches homes to ISP router homes share access network to cable headend ■ unlike DSL,which has dedicated access to central office Introduction 1-15
Introduction data, TV transmitted at different frequencies over shared cable distribution network cable modem splitter … cable headend CMTS ISP cable modem termination system HFC: hybrid fiber coax asymmetric: up to 30Mbps downstream transmission rate, 2 Mbps upstream transmission rate network of cable, fiber attaches homes to ISP router homes share access network to cable headend unlike DSL, which has dedicated access to central office Access net: cable network 1-15