A Closer Look at network structure 口 Network edge applications and hosts 口 Access networks, physical media wired wireless communication links 口 Network core Interconnected routers e Network of networks Introductio 1-15
Introduction 1-15 A Closer Look at Network Structure: ❑ Network edge: applications and hosts ❑ Access networks, physical media: wired, wireless communication links ❑ Network core: ❖ Interconnected routers ❖ Network of networks
The Network edge End systems(hosts) .s Run application programs ÷Eg.Web, email .o At"edge of network" peer-peer 口 Client/ server model o Client host requests, receives service from always-on server SD E.g. Web browser/server client/server email client/server 口Peer- peer mode: Ⅳc 冷 Minimal(orno) use of dedicated servers %D E.g. Skype, Bit Torrent Introduction 1-16
Introduction 1-16 The Network Edge: ❑ End systems (hosts): ❖ Run application programs ❖ E.g. Web, email ❖ At “edge of network” client/server peer-peer ❑ Client/server model ❖ Client host requests, receives service from always-on server ❖ E.g. Web browser/server; email client/server ❑ Peer-peer model: ❖ Minimal (or no) use of dedicated servers ❖ E.g. Skype, BitTorrent
Network Edge: Reliable data Transfer Service Goal: data transfer TCP service_[RFC 7931 between end systems a Reliable in-order byte- 口 Handshaking: setup stream data transfer (prepare for) data .s Loss: acknowledgements transfer ahead of time and retransmissions 冷 Hello. hello back human口 Flow contro: proTocol Sender won 't overwhelm Set up state"in two receiver communicating hosts 口 Congestion contro/ 口TCP- Transmission 令 Senders" slow down Control protocol sending rate"when Internet's reliable data network congested transfer service Introduction 1-17
Introduction 1-17 Network Edge: Reliable Data Transfer Service Goal: data transfer between end systems ❑ Handshaking: setup (prepare for) data transfer ahead of time ❖ Hello, hello back human protocol ❖ Set up “state” in two communicating hosts ❑ TCP - Transmission Control Protocol ❖ Internet’s reliable data transfer service TCP service [RFC 793] ❑ Reliable, in-order bytestream data transfer ❖ Loss: acknowledgements and retransmissions ❑ Flow control: ❖ Sender won’t overwhelm receiver ❑ Congestion control: ❖ Senders “slow down sending rate” when network congested
Network Edge: Best Effort( Unreliable Data Transfer Service Goal: data transfer Apps using TCP between end systems 口HTTP(Web),FTP(file ÷5 ame as before! transfer telnet 口UDP- User datagram (remote login), SMTP Protocol [RFc 7681 (email) , Connectionless ☆ Unreliab| e data App's using UDP: transfer 口 streaming media, . No flow control teleconferencing, DNS, s No congestion control Internet telephony Introduction 1-18
Introduction 1-18 Network Edge: Best Effort (Unreliable) Data Transfer Service Goal: data transfer between end systems ❖ same as before! ❑ UDP - User Datagram Protocol [RFC 768]: ❖ Connectionless ❖ Unreliable data transfer ❖ No flow control ❖ No congestion control App’s using TCP: ❑ HTTP (Web), FTP (file transfer), Telnet (remote login), SMTP (email) App’s using UDP: ❑ streaming media, teleconferencing, DNS, Internet telephony
Access Networks and Physical Media Q: How to connect end systems to edge router? a Residential access nets 口 Institutional access networks(school company) u Mobile access networks Keep in mind: 口 Bandwidth( bits per secondof access network? 口 Shared or dedicated? Introduction 1-19
Introduction 1-19 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?