Chapter1 Introduction

1.1 what is Internet? What is a protocal

Internet: Network of Networks
protocals define the format, order of messages sent and received among network entities, and actions taken on message transmission, receipt.

1.2 Network edge

approximate speeds

access network	speeds
Ethenet	Wired. Up to 100's Gbps per link
802.11 WiFi	Wireless. 10’s to 100’s of Mbps per device.
Cable access Network	Wired. Up to 10’s to 100’s of Mbps downstream per user.
Digital subscriber Line	Wired. Up to 10’s of Mbps downstream per user.
4G cellular	Wireless. Up to 10’s Mbps per device.

1.3 The network core: packet/circuit switching, internet structure

1.4 performance: delay, loss, throughput

delay: processing delay, queueing delay, transmission delay, propagation delay

1.5 layering, encapsulation, sevice models

layered Internet protocal stack

1. application: supporting network applications
   • http, IMAP, SMTP, DNS
2. transport: process-process data transfer
   • TCP, UDP
3. network: routing of datagrams from source to destination
   • IP, Routing protocals
4. link: data transfer between neighboring network elements
   • Ethenet, 802.11(WiFi), PPP
5. physical: bits "on the wire"

layer
application	message	M
transport	segment	HtM
network	datagram	HnHtM
link	frame	HlHnHtM
pysical	bit