CNT 4007 Computer Networks - Chapter 1 : Overview Jonathan Kavalan, Ph.D. Department of Computer, Information Science and Engineering (CISE), University of Florida 1
Chapter 1: Introduction Our goal: get feel and terminology more depth, detail later in course approach: use Internet as example Overview: what s the Internet? what s a protocol? network edge; hosts, access net, physical media network core: packet/circuit switching, Internet structure performance: loss, delay, throughput protocol layers, service 2
All CS/CE majors should understand this joke, right? Things are not always what they seem; the first appearance deceives many; the intelligence of a few perceives what has been carefully hidden. - Phaedrus 3
Chapter 1: Introduction Our goal: get feel and terminology more depth, detail later in course approach: use Internet as example Overview: what s the Internet? what s a protocol? network edge; hosts, access net, physical media network core: packet/circuit switching, Internet structure performance: loss, delay, throughput protocol layers, service 4
PC server wireless laptop What s the Internet: nuts and bolts view cellular handheld router access points wired links millions of connected computing devices: hosts = end systems running communication network apps links fiber, copper, radio, satellite transmission rate = bandwidth Mobile network Home network Institutional network 5 Global ISP Regional ISP
What s the Internet protocols control sending, receiving of msgs e.g., TCP, IP, HTTP, Skype, Ethernet Internet: network of networks loosely hierarchical public Internet versus private intranet Internet standards RFC: Request for comments IETF: Internet Engineering Task Force Mobile network Global ISP Home network Regional ISP Institutional network 6
What s the Internet: a service view communication infrastructure enables distributed applications: Web, VoIP, email, games, e-commerce, file sharing communication services provided to apps: reliable data delivery from source to destination 7
What s a protocol? a human protocol and a computer network protocol: Hi Hi Got the time? 2:00 time TCP connection request TCP connection response Get http://www.ufl.edu/ <file> Q: Other human protocols? 8
What s a protocol? human protocols: what s the time? I have a question introductions specific msgs sent specific actions taken when msgs received, network protocols: machines rather than humans all communication activity in Internet governed by protocols protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, 9
A closer look at network structure: network edge: applications and hosts network core: routers network of networks access networks, physical media: communication 10
The network edge: end systems (hosts): run application programs e.g. Web, email at edge of network client/server model client host requests, receives service from always-on server e.g. Web browser/server; email client/server 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? 12
Residential access: point to point access Dialup via modem up to 56Kbps direct access to router (often less) Can t surf and phone at same time: can t be always on DSL: digital subscriber line deployment: telephone company (typically) up to 1 Mbps upstream (today typically < 256 kbps) up to 8 Mbps downstream (today typically < 1 Mbps) dedicated physical line to telephone 13 central
Digital Subscriber Lines Bandwidth versus distanced over category 3 UTP for DSL. 14
Digital Subscriber Lines A typical ADSL equipment configuration. 15