A closer look at network structure 口 network edge applications and hosts 口 network core: ■|●●● m routers network of networks 口 access networks physical media communication links Introduction 1-16
Introduction 1-16 A closer look at network structure: q network edge: applications and hosts q network core: m routers m network of networks q access networks, physical media: communication links
Chapter 1: roadmap 1. 1 What is the internet? 1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5 Internet structure and isps 1.6 delay loss in packet-switched networks 1. 7 Protocol layers, service models 1. 8 History Introduction 1-17
Introduction 1-17 Chapter 1: roadmap 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5 Internet structure and ISPs 1.6 Delay & loss in packet-switched networks 1.7 Protocol layers, service models 1.8 History
The network edge 口 end systems( hosts) m run application programs Web email m at edge of network 口 client/ server model ■|●●● wn client host requests, receives service from always-on server W已 g Web browser/server email client/server 口peer- peer model minimal (or no)use of dedicated servers mmeg Gnutella, KazaA Introduction 1-18
Introduction 1-18 The network edge: q end systems (hosts): m run application programs m e.g. Web, email m at “edge of network” q client/server model m client host requests, receives service from always-on server m e.g. Web browser/server; email client/server q peer-peer model: m minimal (or no) use of dedicated servers m e.g. Gnutella, KaZaA
Network edge: connection-oriented service Goal: data transfer TCP service [RFC 7931 between end systems o reliable, in-order byte 口 handshaking: setup stream data transfer (prepare for) data loss: acknowledgements transfer ahead of time and retransmissions Hello, hello back human a flow contro/: protocol m sender won t overwhe m n set up state in two receiver communicating hosts 口 congestion contro/: TCP- Transmission m senders "slow down sending Control protocol rate"when network n Internet's connection- congested oriented service Introduction 1-19
Introduction 1-19 Network edge: connection-oriented service Goal: data transfer between end systems q handshaking: setup (prepare for) data transfer ahead of time m Hello, hello back human protocol m set up “state” in two communicating hosts q TCP - Transmission Control Protocol m Internet’s connection- oriented service TCP service [RFC 793] q reliable, in-order byte- stream data transfer m loss: acknowledgements and retransmissions q flow control: m sender won’t overwhelm receiver q congestion control: m senders “slow down sending rate” when network congested
Network edge: connectionless service Goal: data transfer App' s using TCP between end systems 口HTTP(eb),FTP(fle same as before transfer), telnet 口UDP- User datagram (remote login), SMTP Protocol [RFC 768] (email) Internet's connectionless service App's using UDP unreliable data transfer 口 streaming media, no flow control teleconferencing DNS Internet telephot ny no congestion control Introduction 1-20
Introduction 1-20 Network edge: connectionless service Goal: data transfer between end systems m same as before! q UDP - User Datagram Protocol [RFC 768]: Internet’s connectionless service m unreliable data transfer m no flow control m no congestion control App’s using TCP: q HTTP (Web), FTP (file transfer), Telnet (remote login), SMTP (email) App’s using UDP: q streaming media, teleconferencing, DNS, Internet telephony